Thanks. I am doing a refit currently on our Marine ply Eventide 26, and the majority of rot issues I encountered was where polyester resin and glass cloth was used over ply. In most of the problmem areas, it simply did not bind with the wood fibers and I could pull it off by hand. Fresh water also got trapped behind the polyester, and wood rot set in. I've now replaced the majority of the rotten wood with fresh wood. I use Aerontec Epoxy products, which is very similar to West. After watching your video, I am convinced that I am doing the right thing in using thick epoxy for gluing and penetrating epoxy and not polyester for treating wood before painting with MS primer and 2k. The cost savings in the short run, which previous owners of our boat probably chose to do, is now causing me lots of headaches. I would rather spend more and know that the boat is good for another 50 years. (She was built in 1977)
Good information in this video. This supports the idea that all you need is epoxy to seal the plywood fully and then laminate glass ( or carbon ) fibers over it. Since your test showed, the first layer of plywood is in danger, so now I understand better why the screwing or nailing of laminates into the plywood increases a lot of total strength of the laminate. I have put 2-3 layers over the wood or plywood, then drilling the holes for screws or nails, then applying 3-4 layers over the nailed layer. But there are a lot of big boats that have been laminated with polyester resin and chopped mat BUT laminates are always nailed. Then the bonding force is more the combination of the laminate AND the screws or nails, and cheaper resin can be used again. But if one method has to be chosen, use epoxy as primary resin for boat repairs.
An extremely informative and valuable video. Many thanks for sharing. This couldn't have come at a better time - I am in the process of replacing the top skin on my aft cabin roof after replacing the balsa core. The top skin is 6mm thick. After a paralysing period of indecision and procrastination, I opted to use West System 105 epoxy for bonding the new balsa core and laying up the new top skin. I have just yesterday carried out a practice run at laying up a new (small) top skin in the garage at home using a piece of 6mm thick MDF with a square hole cut out and scarfed, to simulate the cut out section of cabin roof, then backed with some scrap plywood to simulate the core giving me a miniature pretend roof (approx. 1/8 of actual size) with a 6mm deep repair area to laminate into. I have a similar issue to you in that on my boat I cannot achieve the full 12:1 scarf ratio due to adjoining raised mouldings around the repair area. Best I can manage is a tad over 8:1 ratio. I opted for epoxy on that basis and was still reeling at the high material cost, wondering if I had been stupid. Your video has reassured me that I have made the right decision and I am now feeling a lot happier. During my practice lay up, I preheated the epoxy and hardner (206 slow) to 25 Dec C in my homemade warming cabinet and found the biaxial combination mat (6 layers) wet out ok with the use of a West System foam roller (expensive but worth it) and a bit of patience. I imagine it would be a nightmare in colder temperatures though (haven't tried). Thanks again for a very useful and well presented video. Just subscribed to your channel 😊.
This is the video I have been looking for. Excellent explanation of the pros and cons of poly vs epoxy. I am not sure why I have not seen your channel before now. I would say the YT algorithms are not working for you. Keep going.
Nice testing. I saw a short clip of adding layers of fiberglass to the hull... would love to see more on the osmosis treatment and just how far you went with it.
Thank you. We peeled then added a 200g cloth with epoxy over the whole bottom. I think we’ll make the bottom job a free video on UA-cam. It should be up this Autumn sometime. We still need to do the barrier coats and copper coat.
Thinning the Polyester with Styrene monomer, then wetting out the Marine Plywood first and allowing the resin to penetrate the Plywood, After curing for 30 minutes to an hour, will give the Polyester a much stronger bond when used full strength.
Great vid... Thanks. Important to note as well... once you've used epoxy in an area, don't apply any polyester based products over it without very specific surface prep. Epoxy onto polyester is fine.
I know this is the general rule, but I have yet to do an experiment to confirm. I suspect polyester will bond to epoxy in much the same way as it bonds to plywood!
@@seaschool_ Great... Please let us know the results. I'd imagine that any additional "keying" component that you introduce as well as perhaps a primer might get good results. Before I knew this rule of thumb though, I had a minor failure using gelcoat over an epoxied patch, with the gelcoat simply peeling off after a few months.
Nice this is extremely helpful. If you ever do this again you should consider that you can just use the scale to pull directly without using the weight.
Really interesting video. Andy has done a little similar tests on boatworks today-channel. There was at least bonding tests on different materials to gelcoat. This is very interesting subject for me as I'm going to build big boat from scratch with wood-epoxy method. For interior work it would be beneficial to be able to use something a bit cheaper than epoxy though. For the hull - not so sure as it has to be 100% waterproof to protect the wood itself.
@@seaschool_ I'm a bit lost on your comments above. What does the high temperature do to the epoxy? I've got some parts of my boat painted dark blue, and doing repairs with epoxy (as it can sit in the tub for long periods of time it takes me, unlike resin that will age ;) ). I am repainting it light blue, but it would help to know of the dangers of using epoxy on the roof, if it gets too hot in summer.
@@TechyBen Hello there. If you are in the tropics(are you?) and the sun is high, and you have painted your epoxy a dark colour then it can soften. For structural epoxy resin built elements this could be pretty disastrous. It does have to be pretty hot though for this to happen. If this doesn't answer your query please drop me an email at ahoy@sea.school
@@TechyBen I wouldn't worry then. I'm planning on taking Black Sheep down to tropics sometime and it's got black topsides so I've avoided using epoxy in these areas for this reason. However, on the deck, which will be a pale colour, I have used some epoxies in a few areas.
After using 20ltrs. of unwaxed resin [Polyester] 200 mtrs. of 16oz. x 100mm wide fibreglass tape and 4 litres of flow coat on my foam cored project boat, I needed to finish the job, by strengthening the the transom. This was the only place that I had timber [plywood] to work with. I tried polyester, the result was that I could lift the laminated glass layer with my fingernails. For me the only way to glass wood is to use epoxy resin. I only needed 1.5 ltrs so cost is not included in my decision in this case. If cost was a factor I would take into consideration the cost of doing the job twice.
For any kind of resin, first, score the surface with 40 or 80 grit sandpaper. After scoring, saturate the surface by resin before you place any lamination on it otherwise resin will be sucked up into the wood your lamination will be dry. Of course epoxy will be the winner of the bond test in any case but if you know what you are doing Polyester resin might be sufficient for the job. Boat manufacturers use polyester resin as they generally know what they are doing. For epoxy resin you need a workshop temperature of 15+ degrees Celcius for about 12 hours. Or make sure you work in a hot summer day. West System is a good epoxy but not my favorite. There are so many different epoxy resins available for marine use. I believe that WS is a rip off.
great video, great help! I'm from Brazil and I'm going to laminate a fishing boat made of garapeira wood this week, it will be with polyester resin and two layers of 600g biaxial combined fabric together with a 225g blanket, I don't know this additive for polyester around here, I know that polyester is much worse for wood than epoxy, but epoxy here costs 10 times more than polyester, can you help me with some way to make polyester stick better to wood please
Super interesting video! I've never heard or seen Prymax mentioned anywhere else but the results speak for themselves. There's absolutely no doubt epoxy wins for bonding in pretty much every circumstance but it would be hard to justify the price vs poly when used in conjunction with Prymax. Do you know much about Vinylester resin? I've read its somewhere between poly and epoxy performance wise but yet others say its no better than poly when bonding to wood.
Hi mate, I'm in Scotland currently restoring a Mayland Fisher 500 to hold dual motors combined 3x the intended transom limit and this is a small project but a difficult one because of that reason. I'm dealing with every nasty angle there is and at 6ft3" can barely fit in the cuddy. Moaning aside the detail for the job is simple- No expense spared make it look like new, keep it roughly the same weight and hull dimensions and make it last at least another 40-50yrs. The boat was built by ex ww2 guys at Mayland in the early 70s who built it as a scaled down Vospa MTB they had constructed during the war. The little boat is a masterpiece is overbuilt to a level ive never seen before for any size craft. Its got a 2 shell cuddy fully float tanked and the outside its got the outer hull + an inner hull & a deck sole as well as Flotation tanks and it doesnt use wood at all other than its backbone for laying up. It's a cut down bulkheads throught rather than stringers and just built to last forever... it straight up rejects poly and Vinyl fixes during the shrinkage phase especially if it's cold out it will delaminate an blow the entire fix out with a jet wash. Vinyl is OK for layup of boats when they are new and they chemically bond the entire thing, it's terrible for fixes plus you NEED to buy Vinyl resin from a reputable supplier as it only works for a few month after its been refined and bottled up. Its regarded as OK for interior use and only use it for structural if you can absolutely guarantee its age and you already know how to use it properly from smaller projects. Polly is poly its OK for minor fixes or large but non structural fixes but keep the area you are doing it in at the same temp for at least 12hr and it works outside OK in sunlight too. Proper Epoxy especially West Systems is by far the best not just in bad conditions but if you need to redo transoms etc that are already holding an engine that's at the upper boundary of the transom limit then the difference is that the repair with West Systems given you used the appropriate cloth will almost certainly never fail again in your lifetime, the polly or vinyl transom repair will either delaminate and crack after the first few winters or just perish over the next 5-7yr and need done again. You won't ever get poly or vinyl to do genuine Epoxy resins job and what people forget is that West systems be it the basic 105 or Gflex or other brands top epoxy are all from the same people and West Systems is just them selling you it direct rather than another badge on it with fillers or thinners in it.
Another thing about West Systems. The 105 is the daddy we know this and it's the most forgiving, however pay attention to which cloth you lay up with it and the thickness as you don't want your fix to be rigid on a boat that likes to flex, nor do you want to accidentally do a fix between say your deck sole and actual hull where two laminate GRP lay ups that were intended by design to have a gap between them and flex independantly.. are now fully bonded together because you glued them up with proper epoxy. Basically beware of what you bond up below the surface with proper Epoxy as it genuinely is so strong a bond that even if you skelp the hull off a rock that part you bonded up accidentally to your inner hull will also get the brunt of the energy transfer... so don't over-do the job if you are using proper Epoxy like West 105. Do your first soak coat thick then give it an hour then come back and lightly spread a thin layer over it keeping the brush or roller saturated so it doesn't grab the first sticky layer it just smears over it and gets rid of the bubbles. Then lay your cloth and don't put any resin above the cloth for the first minute or so just let it slither in. Then stipple the cloth in from above DO NOT PUSH OR SPREAD IT at this point. Give it another minute or so then stipple it again from directly above and you will see air pockets so its easy to judge which parts you need to stipple in. If you need it to be Uber flat you need a fin roller and don't overuse it just push it at medium-2-light pressure over the entire area in the 4 common directions then walk away when it looks half decent as the 'flow-out' process will do the rest. Never over work an area with a brush, roller or spray gun.. walk away when you feel the liquid or resin harden up and start dragging or in spray gun terms when you start pushing the layed paint about with the air pressure. I won't ever tire of telling folk to walk away from an area they have messed up AS SOON as they messed up, forget about that bit and move on dont destroy an entire area by pushing a mistake about trying to fix it. These bits can be fixed up perfectly by some leftover resin and cloth that you are using for the next bit of your project. One other thing to note if you aren't in the UK> We have powder bound chop strand for proper Epoxy, we are used to picking between the normal type Chop Strand matting for Poly and Vinyl resins OR the powder bound Chop Strand that's used with proper Epoxy. I know that most other places in the world outside UK and Japan you only associate chop strand with poly or vinyl but here in the UK the norm is that when using proper Epoxy you just order the "Powder bound" chop. The differnce is huge as powder bound chop strand with proper Epoxy can easily out perform Poly or Vinyl with the more advanced weaves of cloth so just to put that in perspective proper Epoxy with basic powder bound chop-strand matting can easily out perform the best Vinyl or Poly that has multiple axial layers and roving layers. If you try to lay up emulsion bound chop-strand designed for Poly or Vinyl with proper Epoxy resin then it will still work but you will need a lot of it and the repair will look ugly. If you try to lay power bound Chop Strand designed for Epoxy resins with Poly or Vinyl then you will have made a huge mistake as it will blow off in a high wind.
Thanks for your insight - I’m in need of info concerning the building of a center box between beams 2 and 3 on a Wharram Pahi 42ft. It is not about building of the box, but that of material used. My old one needs to be rebuilt because of rot. I used 9mm ply but was wondering if I can build it lighter with the same strength by using 6mm ply covered in chop strand or woven fibre. The fibre on the outside will also protect against water splashes? Any help will be much appreciated. Its about strength vs weight - 9mm ply - 6mm ply covered one side - or covered both sides
This is great information, thanks for sharing the tests. I wanted to do a similar comparison test, but had no idea about prymax so would have certainly discounted polyester had I done this myself as only a direct comparison between it and epoxy. It is a slight double edged sword for me as I was all ready for the epoxy route.... with its drawback for my use case. I have built a telescope observatory dome, which is thin plywood segments stretched over laminated plywood ribs - think a low resolution chocolate orange cut in half :D I want to encapsulate it in epoxy fibreglass for waterproofing and keep it a natural, unpainted finish like boat brightwork. The more I read the more I wonder if I am about to shoot myself in the foot given the UV instability of epoxy. Generally the takeway seems to be "low maintenance brightwork" is an oxymoron! Given how well prymax looks to work, I wonder if polyester resin could be back on the table for a (sort of) clear wood finish as, anecdotally at least, it seems to hold up well in the sun. I think I will do my own test, definitely using prymax - I plan on only using one 200gsm twill weave layer and there may be something about polyester resin preferring thicker layups than that, perhaps too brittle in thinner layers... testing will tell. All the best with your rebuld.
One option would be to use a UV resistant epoxy. West System 105 resin with their 207 "special coating" hardner is claimed to be crystal clear, UV resistant and further fortified by overcoating with polyurethane varnish. It is their recommendation for clear finishing wood that will be exposed to sunlight. I've never tried it but it would be my go to choice for what you are describing. Polyester resin will turn opaque over time anyway if left clear and look nasty.
for better polyester adhesion ont existing polyester, you must hammer the polyester with a wood chisel, to get some fibres out, then use a first coat of thin polyester resin, then proceed normally.
The polyester works maybe better in reality than this. In the real world, you would wet the plywood in advance, before laying any cloth, a bit more than here. The second thing is that with poly, on the bonding layer, you usually would use chopped strand mat( emulsion bond version), as a bonding layer before any other matt. CSM helps wetting also the cloth. I am a hobby boat repair guy, and even if epoxy as a resin has a much better bond, i consider hand laminating polyester is a bit more forgiving. Alternating CSM with cloth makes polyester laminating much easier than with epoxy. particularly in difficult bends....Epoxy also needs much beter prep( due to lack of emulsion bond matt). Rotten plywood is usually due to holes in laminate, never mind epoxy or polyester. In repair jobs, I actually mostly use epoxy as then i don't need to worry what material is previously used....but I would otherwise use polyester as its so much easier to laminate.
I live in a tropical environment, and want to do my project under the shade. Epoxy looks better for what I need, I'm hoping that my project is super water proof. Epoxy over plywood. What's your recommendation ?
Hi. How about poly as a sheath on a hulls exterior.? Thanks. Think you answered my question by saying the lack of water resistance. As we live with only water access and I have to push the boat out over 300 m of mud. We just hot our barge stolen , so are making another. Was wondering if poly would be a sheath possibility. As no paint on the bottom because of the daily going to school drop off. Any thoughts would be appreciated! Thanks. From NZ.
This is for a small boat I guess if you’re pushing it. You could use gelcoat, or you could epoxy. Neither will stand up to contact with ground very well though. Put a Ultra high molecular weight polyethylene strip along the keel so that it protects the boat and works better as a sledge.
Thanks for comment. We will be including vinyl ester in future tests. As the focus of this was laminating onto marine plywood we decided to leave it out this time.
I may have got this wrong but I seem to remember reading somewhere that vinyl-ester has a poor shelf life. Hence unless you are using it regularly, it makes for poor economy to have unused resin on the shelf going off before you have chance to use it up. Perhaps not an issue on a big project that's in full swing, but for DIY use where the project happens in bits and bobs over time, then probably wouldn't be a good option.
@@dannyboy9817 Suppliers usually say 6 months but I've had stuff that lasts for a couple of years easily on the shelf. You know when it's gone off - it goes pretty solid and impossible to shake up/stir.
Great video! Can you advise what you would consider suitable for the following application, I am building some outdoor furniture and each has an inlay design, hopefully filled with a suitable resin, unsure as the advise given is varying from flooring experts to crafters, some say you can't use a resin outdoors and others imply you can with the right additives. Each unlay and design is filled with a resin pour of no more than 4mm and would be pigmented and coloured - and requires a suitable resin (Epoxy resin, Polyester resin, and Polyurethane resin) that can withstand the elements, the UV conditions and the rain and moisture, and in some cases the colder climates. Appreciate your recommendations and expertise, thanks Gaz
Isothalic polyester resin is much better when it comes to water resistance than the standard general purpose orthothalic polyester resin. Also tissue, also called veil, resists osmosis even when used with general purpose orthothalic polyester.
Welcome to the world of boat maintenance. When we buy a boat we have basically committed a large quantity of time to , A . Maintenance schedule and B . A certain amount of pleasure . The trick is to be VERY CAREFUL what you buy , even if it's free . !
Yes, owning a boat is time consuming. Especially one with lots of wood like mine. We now live in a world where we are are forced to make absurd efficiencies with our time. Working on a project, that takes so much time, seems almost counter cultural. Yet humans were meant to build, it is what we have evolved to do, and imo we have yet to come up with a more beautiful invention than a seaworthy sail boat carving through the ocean using the wind to drive it. So spending some time to make that happen is ok with me.
I need a very liquid (low viscosity) Epoxi or PE for filling fine cracks in concrete. can you recommend something? is PE or Epoxi thinner? want to use a syringe with a 4 mm tube
Use the stuff designed for that as proper epoxy resin or Poly and Vinyl stuff needs coated for UV protection afterwards. There are several brands in the UK that sell both boat, swimming pool and general building Epoxy mixes but you might need to do some homework. For example epoxy paint wise its a mob called Black Country paints that sell every other brand it here for them to then water it down and use talcum powder as a filler then sell you it at 40x inflated price in a homestore or Amazon as a "Driveway Epoxy filler" Find the main supplier like i was saying about Black Country paints here in the UK the next brand down they sell the not so good stuff too are sold on Amazon and ebay and online under other names like 'TA paints' and 'Indistrial paints' a few other brand names. They supplying our military paints even the Aquasteel stuff used as a rust convertor on our submarines but they sell the leftover stuff to other brands to sell to the average consumer. Do some homework on epoxies for garden use and I'm sure you will find out what's what in your neck of the woods then jusy buy the stuff the farmers etc use direct from the supplier, guaranteed they will sell it from a gallon can upwards mate 👍
Hi how are you ? I need a advice from you , i have a refrigerator room made from panels but water its leaking under the panel . So my idea was to cover panels with marine wood panel and than i want to coat it with epoxy resin . Do you think it will work ? Temp of the fridge goes -30 celsius .
Marine ply is designed to soak in whatever liquid that is put on it. The intention being that if its first big soak is epoxy resin then it fully soaks it in using capillary action beyond what water can do. You could buy expensive marine ply and fully saturate it in epoxy before use but A. It's going to be expensive. B. Time consuming due to cure times and full soak times given the plywoods drinking habit. C. Heavy AF once the epoxy has soaked in and cured it will be the weight of the liquid epoxy and the ply and a saturated board of even 9mm thick marine ply with proper Epoxy resin is F-ing heavy mate trust me it will drink the epoxy in if its genuine marine ply and youl be left with basically glass window weight roof panels. Use the conventional air gap, vapour barrier and fridge insulator mate it's cheaper, lighter and uses the air gap as the ultimate moisture trap rather than your wallet and bank balance.
Thanks for comment. Vacuum bagging is too specialist for most DIY boat owners. Therefore we won’t be including it in our videos for the foreseeable. It would have created a neater and lighter layup (perfect resin to cloth ration) but I doubt it would have changed the breaking strength of these resins or polyesters performance as a glue.
tabi bu deneylerde bir çok faktör var ama yined bir fikir veriyor,mesela hangisinin elastikiyeti daha iyi hangisinin çekme dayanımı daha iy?,bilirsiniz bu tür hesaplamalarda çekme kopma burkulma gibi dayanımlar ve eldeki veriler önemli olur. 3 ününde eşit koşullarda denenmesi gerekirdi,sen ne kdar eşit vrnbildin belli değil ama yaklaşık değerleri yakaladın.
@@paulbriggs3072 ... no ! the diluted resin infiltrate deeply in the wood (no fibre), witch makes a much better and deeper adhesion layer with the wood ! ... when tacky ... add normal resin with fibres !
@@paulbriggs3072 You and OP are both right. It breaks down the resin (weakens it), so that smaller and smaller bits of it can filter down into the wood, stopping where the finest bits are not able to sink further into the wood. It makes a web that is infused into the wood, which is like thousands of micro tent stakes. And if the surface is wiped clean before it cures, there no significant weak layer of resin left to bond to. It’s just primed with resin.
No. Proper Epoxy will stick to anything even glass and diamonds they use it to set polished diamons it has the most tenacious bond known and works on anything and bonds to poly and vinyl resin better than they do to themselves. The problem is whan you use proper epoxy for a fix you cannot use poly of vinyl over the top as it hasn't got the ability to bond to glass, diamond or pure epoxy resin so you need to either use a fairing filler with the final epoxy layer even coloidal silica and sand that back before applying the poly or vinyl or you can sand the bare epoxy barrier coat back to around 190grit max (240grit can just about make enough grip if you keep using fresh pads) and apply an adhesion promoter from a can or spray gun, do two coats of adhesion promoter maybe 30 mins apart and ignore the 10-15 between coats that it says on the data sheet then apply your poly or vinyl directly over it. Another acceptable method is to 40-80grit the epoxy then soak it with Acetone repeatedly, dry it quickly with air hose then fire the poly or Vinyl resin on while it's in a state of "acceptance" The problem you have is that proper epoxy is really good at resisting chemicals and it's only too willing to accepting poly based paints but it's because they are heavily saturated with xylene etc and by the nature they bond to the surface not just themselves. Poly resin and vinyl bond mostly to their own.
I would probably automatically go with the best performing product despite material costs because I would assume the major cost would be the labor and not the materials and I would prefer to avoid doing the repair a second time.
The video is hopefully demonstrating that there is some nuance to what the best performing is - depending on the situation.If you use epoxy on black painted hull in the tropics the whole thing can start melting in the sun. This therefore isn't the best performing product.
Right after I finished fiberglassing my plywood boat with polyester resin and cloth,I heard that the cost of epoxy was coming down to near the cost of polyester! I don’t know this for sure. But now it’s too late. I will just have to assume it’s going to hold up.
I wonder why you did not wet out the the plywood before laminating, best practice says you should. If you had the results would be much different but the epoxy will always be better. When you use epoxy you also get a much better moisture barrier, critical when using timber in a marine environment. As we all know you can't buy quality resins cheaply hence the price difference between poly and epoxy.
Thanks for your comment. Perhaps you should look again at this video. I did wet out the plywood before laying up. Epoxy is an excellent resin, but not necessarily always the right choice.
Hey, there is Epoxy resin, Polyester resin, And Polyurethane resin. There is no fiberglass resin as far as I'm aware. The 'Fiberglass' part is the mat. You can apply a resin directly to your wood surface. This would make the wood waterproof and it would give it some extra strength. HOWEVER; As far as I'm aware the mat (which is the fiberglass part, not the resin) is what gives laminated materials their real strength. So it seems that it really is worth it to put the fiberglass mat down if you need strength especially bending resistance. Fiberglass mat is much cheaper than resin anyway, so you might as well. 👍👍
@@Farmer2492 I wouldn’t. It’s too brittle without being bound with matting. If you do use resin as a coating like this you use flowcoat, which is similar to gelcoat. When this is painted directly onto wood (rather than laminate over wood) it will often crack quickly.
My 50 year old plywood dinghy is still holding together well so I think polyester is good enough for this purpose. I avoid epoxy because the fumes are horrible and I end up looking like the elephant man 🙂
One reason I made the video was to show how important it is to prime the surface of the ply before using polyester. Prymax one way of doing this. Your method is another.
Great overall but don't you think pouring sand into a bucket to test more precisely the weight of the breaking strength would be, rather than 2 bricks versus 4 bricks? PLUS, there is something else you didn't discuss which is that epoxy is superior in preventing rot. West System did surveys of 40 year old epoxy wood boats that had few problems. Most 40 year old polyester fiberglass encapsulated boats have rotted wood inside.. By the way to give you an idea of the spying tht goes on, while I was watching this, an epoxy ad interrupted the video!
Thanks for this. I like the sand idea - although I would have needed a lot of buckets to get 30 kilos! Regards to rot, that occurs because of delamination allowing moisture in - so bond is crucial to this
@paulbriggs3072 Thanks for your comment. Did you watch the whole video?We discuss water resistance later in this video. We'll be conducting some tests soon on how brittle they are comparatively, as well as some tests on how high temperatures can cause epoxies to fail prematurely.
polyester resin is JUST for Layup, it is not designed for structural strength on bulkheads s similar, if you need to add strength to a frame or bulkhead apply more wood using epoxy or sheath in epoxy. you always Layup with Poly and Glue with epoxy.
Most production boats are built with just polyester against plywood - that's why I did this test. I agree that using polyester resin as a glue in this way is not the best construction method.
Because the epoxy is stronger than wood, and the polyester is weaker than wood. The glass to glass bond is stronger too, and the wood is protected from rot with epoxy. West System did assessments of 40-year-old epoxy-over-wood boats which had little or virtually no rot. Polyester fiberglass boats of that vintage all have rotted wood stringers.
Not for this one - I wasn't too worried about it for laminating onto ply - but we'll include Vinyl for the next one which is about laminating onto old glass
![Polyester VS Epoxy Resin comparison test - carbon / glass. Expedition lifeboat conversion.Ep102 [4K]](http://i.ytimg.com/vi/Ee6gLcvaLME/mqdefault.jpg)
Thanks. I am doing a refit currently on our Marine ply Eventide 26, and the majority of rot issues I encountered was where polyester resin and glass cloth was used over ply. In most of the problmem areas, it simply did not bind with the wood fibers and I could pull it off by hand. Fresh water also got trapped behind the polyester, and wood rot set in. I've now replaced the majority of the rotten wood with fresh wood. I use Aerontec Epoxy products, which is very similar to West. After watching your video, I am convinced that I am doing the right thing in using thick epoxy for gluing and penetrating epoxy and not polyester for treating wood before painting with MS primer and 2k. The cost savings in the short run, which previous owners of our boat probably chose to do, is now causing me lots of headaches. I would rather spend more and know that the boat is good for another 50 years. (She was built in 1977)
Good information in this video. This supports the idea that all you need is epoxy to seal the plywood fully and then laminate glass ( or carbon ) fibers over it. Since your test showed, the first layer of plywood is in danger, so now I understand better why the screwing or nailing of laminates into the plywood increases a lot of total strength of the laminate. I have put 2-3 layers over the wood or plywood, then drilling the holes for screws or nails, then applying 3-4 layers over the nailed layer. But there are a lot of big boats that have been laminated with polyester resin and chopped mat BUT laminates are always nailed. Then the bonding force is more the combination of the laminate AND the screws or nails, and cheaper resin can be used again. But if one method has to be chosen, use epoxy as primary resin for boat repairs.
An extremely informative and valuable video. Many thanks for sharing. This couldn't have come at a better time - I am in the process of replacing the top skin on my aft cabin roof after replacing the balsa core. The top skin is 6mm thick. After a paralysing period of indecision and procrastination, I opted to use West System 105 epoxy for bonding the new balsa core and laying up the new top skin. I have just yesterday carried out a practice run at laying up a new (small) top skin in the garage at home using a piece of 6mm thick MDF with a square hole cut out and scarfed, to simulate the cut out section of cabin roof, then backed with some scrap plywood to simulate the core giving me a miniature pretend roof (approx. 1/8 of actual size) with a 6mm deep repair area to laminate into. I have a similar issue to you in that on my boat I cannot achieve the full 12:1 scarf ratio due to adjoining raised mouldings around the repair area. Best I can manage is a tad over 8:1 ratio. I opted for epoxy on that basis and was still reeling at the high material cost, wondering if I had been stupid. Your video has reassured me that I have made the right decision and I am now feeling a lot happier. During my practice lay up, I preheated the epoxy and hardner (206 slow) to 25 Dec C in my homemade warming cabinet and found the biaxial combination mat (6 layers) wet out ok with the use of a West System foam roller (expensive but worth it) and a bit of patience. I imagine it would be a nightmare in colder temperatures though (haven't tried). Thanks again for a very useful and well presented video. Just subscribed to your channel 😊.
This is the video I have been looking for. Excellent explanation of the pros and cons of poly vs epoxy. I am not sure why I have not seen your channel before now. I would say the YT algorithms are not working for you. Keep going.
Very helpful comparison. Thank you for adding the bullet points at the end.
Nice testing. I saw a short clip of adding layers of fiberglass to the hull... would love to see more on the osmosis treatment and just how far you went with it.
Thank you. We peeled then added a 200g cloth with epoxy over the whole bottom. I think we’ll make the bottom job a free video on UA-cam. It should be up this Autumn sometime. We still need to do the barrier coats and copper coat.
Thinning the Polyester with Styrene monomer, then wetting out the Marine Plywood first and allowing the resin to penetrate the Plywood, After curing for 30 minutes to an hour, will give the Polyester a much stronger bond when used full strength.
Great vid... Thanks. Important to note as well... once you've used epoxy in an area, don't apply any polyester based products over it without very specific surface prep. Epoxy onto polyester is fine.
I know this is the general rule, but I have yet to do an experiment to confirm. I suspect polyester will bond to epoxy in much the same way as it bonds to plywood!
@@seaschool_ Great... Please let us know the results. I'd imagine that any additional "keying" component that you introduce as well as perhaps a primer might get good results. Before I knew this rule of thumb though, I had a minor failure using gelcoat over an epoxied patch, with the gelcoat simply peeling off after a few months.
Nice this is extremely helpful. If you ever do this again you should consider that you can just use the scale to pull directly without using the weight.
In my first time watch your video..I'm from Tepeng,Malaysia appriciete your test....thanks for de knowleges had u shared with us..
Excellent 'shade tree' video. I really enjoyed it and found it useful. Thanks.
Really interesting video. Andy has done a little similar tests on boatworks today-channel. There was at least bonding tests on different materials to gelcoat.
This is very interesting subject for me as I'm going to build big boat from scratch with wood-epoxy method. For interior work it would be beneficial to be able to use something a bit cheaper than epoxy though. For the hull - not so sure as it has to be 100% waterproof to protect the wood itself.
Thanks for this. For your application I’d probably use epoxy on the outside, but avoid painting it a dark colour unless your sailing in colder climes.
@@seaschool_ I'm a bit lost on your comments above. What does the high temperature do to the epoxy? I've got some parts of my boat painted dark blue, and doing repairs with epoxy (as it can sit in the tub for long periods of time it takes me, unlike resin that will age ;) ). I am repainting it light blue, but it would help to know of the dangers of using epoxy on the roof, if it gets too hot in summer.
@@TechyBen Hello there. If you are in the tropics(are you?) and the sun is high, and you have painted your epoxy a dark colour then it can soften. For structural epoxy resin built elements this could be pretty disastrous. It does have to be pretty hot though for this to happen. If this doesn't answer your query please drop me an email at ahoy@sea.school
@@seaschool_ No, just the UK. :P Gets hot on the surface in full sun in summer. But I'm mainly only doing repairs so far.
@@TechyBen I wouldn't worry then. I'm planning on taking Black Sheep down to tropics sometime and it's got black topsides so I've avoided using epoxy in these areas for this reason. However, on the deck, which will be a pale colour, I have used some epoxies in a few areas.
After using 20ltrs. of unwaxed resin [Polyester] 200 mtrs. of 16oz. x 100mm wide fibreglass tape and 4 litres of flow coat on my foam cored project boat, I needed to finish the job, by strengthening the the transom. This was the only place that I had timber [plywood] to work with. I tried polyester, the result was that I could lift the laminated glass layer with my fingernails. For me the only way to glass wood is to use epoxy resin. I only needed 1.5 ltrs so cost is not included in my decision in this case. If cost was a factor I would take into consideration the cost of doing the job twice.
For any kind of resin, first, score the surface with 40 or 80 grit sandpaper. After scoring, saturate the surface by resin before you place any lamination on it otherwise resin will be sucked up into the wood your lamination will be dry. Of course epoxy will be the winner of the bond test in any case but if you know what you are doing Polyester resin might be sufficient for the job. Boat manufacturers use polyester resin as they generally know what they are doing. For epoxy resin you need a workshop temperature of 15+ degrees Celcius for about 12 hours. Or make sure you work in a hot summer day. West System is a good epoxy but not my favorite. There are so many different epoxy resins available for marine use. I believe that WS is a rip off.
This was my thought also. I'd like to see the experiment repeated with the scoring done first.
great video, great help! I'm from Brazil and I'm going to laminate a fishing boat made of garapeira wood this week, it will be with polyester resin and two layers of 600g biaxial combined fabric together with a 225g blanket, I don't know this additive for polyester around here, I know that polyester is much worse for wood than epoxy, but epoxy here costs 10 times more than polyester, can you help me with some way to make polyester stick better to wood please
Super interesting video! I've never heard or seen Prymax mentioned anywhere else but the results speak for themselves. There's absolutely no doubt epoxy wins for bonding in pretty much every circumstance but it would be hard to justify the price vs poly when used in conjunction with Prymax. Do you know much about Vinylester resin? I've read its somewhere between poly and epoxy performance wise but yet others say its no better than poly when bonding to wood.
Hi mate, I'm in Scotland currently restoring a Mayland Fisher 500 to hold dual motors combined 3x the intended transom limit and this is a small project but a difficult one because of that reason. I'm dealing with every nasty angle there is and at 6ft3" can barely fit in the cuddy. Moaning aside the detail for the job is simple- No expense spared make it look like new, keep it roughly the same weight and hull dimensions and make it last at least another 40-50yrs. The boat was built by ex ww2 guys at Mayland in the early 70s who built it as a scaled down Vospa MTB they had constructed during the war. The little boat is a masterpiece is overbuilt to a level ive never seen before for any size craft. Its got a 2 shell cuddy fully float tanked and the outside its got the outer hull + an inner hull & a deck sole as well as Flotation tanks and it doesnt use wood at all other than its backbone for laying up. It's a cut down bulkheads throught rather than stringers and just built to last forever... it straight up rejects poly and Vinyl fixes during the shrinkage phase especially if it's cold out it will delaminate an blow the entire fix out with a jet wash. Vinyl is OK for layup of boats when they are new and they chemically bond the entire thing, it's terrible for fixes plus you NEED to buy Vinyl resin from a reputable supplier as it only works for a few month after its been refined and bottled up. Its regarded as OK for interior use and only use it for structural if you can absolutely guarantee its age and you already know how to use it properly from smaller projects. Polly is poly its OK for minor fixes or large but non structural fixes but keep the area you are doing it in at the same temp for at least 12hr and it works outside OK in sunlight too. Proper Epoxy especially West Systems is by far the best not just in bad conditions but if you need to redo transoms etc that are already holding an engine that's at the upper boundary of the transom limit then the difference is that the repair with West Systems given you used the appropriate cloth will almost certainly never fail again in your lifetime, the polly or vinyl transom repair will either delaminate and crack after the first few winters or just perish over the next 5-7yr and need done again. You won't ever get poly or vinyl to do genuine Epoxy resins job and what people forget is that West systems be it the basic 105 or Gflex or other brands top epoxy are all from the same people and West Systems is just them selling you it direct rather than another badge on it with fillers or thinners in it.
Another thing about West Systems. The 105 is the daddy we know this and it's the most forgiving, however pay attention to which cloth you lay up with it and the thickness as you don't want your fix to be rigid on a boat that likes to flex, nor do you want to accidentally do a fix between say your deck sole and actual hull where two laminate GRP lay ups that were intended by design to have a gap between them and flex independantly.. are now fully bonded together because you glued them up with proper epoxy. Basically beware of what you bond up below the surface with proper Epoxy as it genuinely is so strong a bond that even if you skelp the hull off a rock that part you bonded up accidentally to your inner hull will also get the brunt of the energy transfer... so don't over-do the job if you are using proper Epoxy like West 105. Do your first soak coat thick then give it an hour then come back and lightly spread a thin layer over it keeping the brush or roller saturated so it doesn't grab the first sticky layer it just smears over it and gets rid of the bubbles. Then lay your cloth and don't put any resin above the cloth for the first minute or so just let it slither in. Then stipple the cloth in from above DO NOT PUSH OR SPREAD IT at this point. Give it another minute or so then stipple it again from directly above and you will see air pockets so its easy to judge which parts you need to stipple in. If you need it to be Uber flat you need a fin roller and don't overuse it just push it at medium-2-light pressure over the entire area in the 4 common directions then walk away when it looks half decent as the 'flow-out' process will do the rest. Never over work an area with a brush, roller or spray gun.. walk away when you feel the liquid or resin harden up and start dragging or in spray gun terms when you start pushing the layed paint about with the air pressure. I won't ever tire of telling folk to walk away from an area they have messed up AS SOON as they messed up, forget about that bit and move on dont destroy an entire area by pushing a mistake about trying to fix it. These bits can be fixed up perfectly by some leftover resin and cloth that you are using for the next bit of your project.
One other thing to note if you aren't in the UK>
We have powder bound chop strand for proper Epoxy, we are used to picking between the normal type Chop Strand matting for Poly and Vinyl resins OR the powder bound Chop Strand that's used with proper Epoxy. I know that most other places in the world outside UK and Japan you only associate chop strand with poly or vinyl but here in the UK the norm is that when using proper Epoxy you just order the "Powder bound" chop. The differnce is huge as powder bound chop strand with proper Epoxy can easily out perform Poly or Vinyl with the more advanced weaves of cloth so just to put that in perspective proper Epoxy with basic powder bound chop-strand matting can easily out perform the best Vinyl or Poly that has multiple axial layers and roving layers. If you try to lay up emulsion bound chop-strand designed for Poly or Vinyl with proper Epoxy resin then it will still work but you will need a lot of it and the repair will look ugly. If you try to lay power bound Chop Strand designed for Epoxy resins with Poly or Vinyl then you will have made a huge mistake as it will blow off in a high wind.
What a great informative video. Thank you!
Thanks for your insight - I’m in need of info concerning the building of a center box between beams 2 and 3 on a Wharram Pahi 42ft. It is not about building of the box, but that of material used.
My old one needs to be rebuilt because of rot. I used 9mm ply but was wondering if I can build it lighter with the same strength by using 6mm ply covered in chop strand or woven fibre. The fibre on the outside will also protect against water splashes? Any help will be much appreciated.
Its about strength vs weight - 9mm ply - 6mm ply covered one side - or covered both sides
This is great information, thanks for sharing the tests. I wanted to do a similar comparison test, but had no idea about prymax so would have certainly discounted polyester had I done this myself as only a direct comparison between it and epoxy. It is a slight double edged sword for me as I was all ready for the epoxy route.... with its drawback for my use case.
I have built a telescope observatory dome, which is thin plywood segments stretched over laminated plywood ribs - think a low resolution chocolate orange cut in half :D I want to encapsulate it in epoxy fibreglass for waterproofing and keep it a natural, unpainted finish like boat brightwork. The more I read the more I wonder if I am about to shoot myself in the foot given the UV instability of epoxy. Generally the takeway seems to be "low maintenance brightwork" is an oxymoron!
Given how well prymax looks to work, I wonder if polyester resin could be back on the table for a (sort of) clear wood finish as, anecdotally at least, it seems to hold up well in the sun. I think I will do my own test, definitely using prymax - I plan on only using one 200gsm twill weave layer and there may be something about polyester resin preferring thicker layups than that, perhaps too brittle in thinner layers... testing will tell.
All the best with your rebuld.
One option would be to use a UV resistant epoxy. West System 105 resin with their 207 "special coating" hardner is claimed to be crystal clear, UV resistant and further fortified by overcoating with polyurethane varnish. It is their recommendation for clear finishing wood that will be exposed to sunlight. I've never tried it but it would be my go to choice for what you are describing. Polyester resin will turn opaque over time anyway if left clear and look nasty.
And absorb water. Prob not a issue in your case….
for better polyester adhesion ont existing polyester, you must hammer the polyester with a wood chisel, to get some fibres out, then use a first coat of thin polyester resin, then proceed normally.
The polyester works maybe better in reality than this. In the real world, you would wet the plywood in advance, before laying any cloth, a bit more than here. The second thing is that with poly, on the bonding layer, you usually would use chopped strand mat( emulsion bond version), as a bonding layer before any other matt. CSM helps wetting also the cloth. I am a hobby boat repair guy, and even if epoxy as a resin has a much better bond, i consider hand laminating polyester is a bit more forgiving. Alternating CSM with cloth makes polyester laminating much easier than with epoxy. particularly in difficult bends....Epoxy also needs much beter prep( due to lack of emulsion bond matt). Rotten plywood is usually due to holes in laminate, never mind epoxy or polyester. In repair jobs, I actually mostly use epoxy as then i don't need to worry what material is previously used....but I would otherwise use polyester as its so much easier to laminate.
Congratulations on 1000 likes. I dedicate it to you.
I live in a tropical environment, and want to do my project under the shade. Epoxy looks better for what I need, I'm hoping that my project is super water proof. Epoxy over plywood. What's your recommendation ?
Hi. How about poly as a sheath on a hulls exterior.? Thanks. Think you answered my question by saying the lack of water resistance.
As we live with only water access and I have to push the boat out over 300 m of mud.
We just hot our barge stolen , so are making another. Was wondering if poly would be a sheath possibility. As no paint on the bottom because of the daily going to school drop off.
Any thoughts would be appreciated!
Thanks. From NZ.
This is for a small boat I guess if you’re pushing it. You could use gelcoat, or you could epoxy. Neither will stand up to contact with ground very well though. Put a Ultra high molecular weight polyethylene strip along the keel so that it protects the boat and works better as a sledge.
Would have been interesting to compare with Vinyl Ester. We have used and find it a very good middle ground product
Thanks for comment. We will be including vinyl ester in future tests. As the focus of this was laminating onto marine plywood we decided to leave it out this time.
I may have got this wrong but I seem to remember reading somewhere that vinyl-ester has a poor shelf life. Hence unless you are using it regularly, it makes for poor economy to have unused resin on the shelf going off before you have chance to use it up. Perhaps not an issue on a big project that's in full swing, but for DIY use where the project happens in bits and bobs over time, then probably wouldn't be a good option.
@@dannyboy9817 we have not had an issue in 3 years we have been using it. We do need to shake it up if it has been sitting for while.
@@dannyboy9817 Suppliers usually say 6 months but I've had stuff that lasts for a couple of years easily on the shelf. You know when it's gone off - it goes pretty solid and impossible to shake up/stir.
Thanks for that. Worth knowing 👍
Thank you for doing, and sharing this!
Great video! Can you advise what you would consider suitable for the following application, I am building some outdoor furniture and each has an inlay design, hopefully filled with a suitable resin, unsure as the advise given is varying from flooring experts to crafters, some say you can't use a resin outdoors and others imply you can with the right additives. Each unlay and design is filled with a resin pour of no more than 4mm and would be pigmented and coloured - and requires a suitable resin (Epoxy resin, Polyester resin, and Polyurethane resin) that can withstand the elements, the UV conditions and the rain and moisture, and in some cases the colder climates. Appreciate your recommendations and expertise, thanks Gaz
Hi,dear You have a better choice by Nano painting,which is much better and waterproof.
@@yanivm3738 Hi, what is Nano painting?
I only really use epoxy for structural uses so can’t advise. I know that it has poor uv properties though.
Im making a Plywood Canoe. Do i have to use a marine specific epoxy? like the West Systems 105 or can I use a more common general purpose epoxy?
You can use any two to one epoxy or better.
Isothalic polyester resin is much better when it comes to water resistance than the standard general purpose orthothalic polyester resin. Also tissue, also called veil, resists osmosis even when used with general purpose orthothalic polyester.
Welcome to the world of boat maintenance. When we buy a boat we have basically committed a large quantity of time to , A . Maintenance schedule and B . A certain amount of pleasure . The trick is to be VERY CAREFUL what you buy , even if it's free . !
Yes, owning a boat is time consuming. Especially one with lots of wood like mine. We now live in a world where we are are forced to make absurd efficiencies with our time. Working on a project, that takes so much time, seems almost counter cultural. Yet humans were meant to build, it is what we have evolved to do, and imo we have yet to come up with a more beautiful invention than a seaworthy sail boat carving through the ocean using the wind to drive it. So spending some time to make that happen is ok with me.
@@seaschool_ That is an almost moving bit of writing, and makes me feel a lot better about the Twister I am about to restore down here in NZ...
I need a very liquid (low viscosity) Epoxi or PE for filling fine cracks in concrete. can you recommend something? is PE or Epoxi thinner? want to use a syringe with a 4 mm tube
You can get specialist low viscosity resins.
Use the stuff designed for that as proper epoxy resin or Poly and Vinyl stuff needs coated for UV protection afterwards. There are several brands in the UK that sell both boat, swimming pool and general building Epoxy mixes but you might need to do some homework. For example epoxy paint wise its a mob called Black Country paints that sell every other brand it here for them to then water it down and use talcum powder as a filler then sell you it at 40x inflated price in a homestore or Amazon as a "Driveway Epoxy filler" Find the main supplier like i was saying about Black Country paints here in the UK the next brand down they sell the not so good stuff too are sold on Amazon and ebay and online under other names like 'TA paints' and 'Indistrial paints' a few other brand names. They supplying our military paints even the Aquasteel stuff used as a rust convertor on our submarines but they sell the leftover stuff to other brands to sell to the average consumer. Do some homework on epoxies for garden use and I'm sure you will find out what's what in your neck of the woods then jusy buy the stuff the farmers etc use direct from the supplier, guaranteed they will sell it from a gallon can upwards mate 👍
@@seaschool_ i bought one, extra long cure time. worked well. almost too viscos. came out of cracks i not even knew they where there. :D
Hi how are you ? I need a advice from you , i have a refrigerator room made from panels but water its leaking under the panel . So my idea was to cover panels with marine wood panel and than i want to coat it with epoxy resin . Do you think it will work ? Temp of the fridge goes -30 celsius .
Marine ply is designed to soak in whatever liquid that is put on it. The intention being that if its first big soak is epoxy resin then it fully soaks it in using capillary action beyond what water can do. You could buy expensive marine ply and fully saturate it in epoxy before use but A. It's going to be expensive. B. Time consuming due to cure times and full soak times given the plywoods drinking habit. C. Heavy AF once the epoxy has soaked in and cured it will be the weight of the liquid epoxy and the ply and a saturated board of even 9mm thick marine ply with proper Epoxy resin is F-ing heavy mate trust me it will drink the epoxy in if its genuine marine ply and youl be left with basically glass window weight roof panels. Use the conventional air gap, vapour barrier and fridge insulator mate it's cheaper, lighter and uses the air gap as the ultimate moisture trap rather than your wallet and bank balance.
And mixed both epoxy dry then apply polyester?
Great test thanks
Can one tell by visual inspection whether a part or joint that had been put togther had used epoxy or polyester resin?
Yes up close epoxy resin looks like a matrix
Hi sir thanks for guidance sir I have one question. For artificial stone which one strong plz answer..
Can't help you with this I'm afraid as haven't used either with artificial stone.
I'd like to see all these done again but in a vacuum bag for compression against the timber if you could.
Thanks for comment. Vacuum bagging is too specialist for most DIY boat owners. Therefore we won’t be including it in our videos for the foreseeable. It would have created a neater and lighter layup (perfect resin to cloth ration) but I doubt it would have changed the breaking strength of these resins or polyesters performance as a glue.
tabi bu deneylerde bir çok faktör var ama yined bir fikir veriyor,mesela hangisinin elastikiyeti daha iyi hangisinin çekme dayanımı daha iy?,bilirsiniz bu tür hesaplamalarda çekme kopma burkulma gibi dayanımlar ve eldeki veriler önemli olur. 3 ününde eşit koşullarda denenmesi gerekirdi,sen ne kdar eşit vrnbildin belli değil ama yaklaşık değerleri yakaladın.
Epoxy resin is good for Carbon fiber skinning?
This is good stuff
Nice test and guiad for us
Thanks and welcome
for better polyester adhesion on wood, you must thin the first coat with 30 % acetone, then proceed normally.
You weaken the resin that way.
@@paulbriggs3072 ... no ! the diluted resin infiltrate deeply in the wood (no fibre), witch makes a much better and deeper adhesion layer with the wood ! ... when tacky ... add normal resin with fibres !
@@paulbriggs3072 ... doing so, ... you will not be able to peel off the polyester !
@@paulbriggs3072 You and OP are both right. It breaks down the resin (weakens it), so that smaller and smaller bits of it can filter down into the wood, stopping where the finest bits are not able to sink further into the wood. It makes a web that is infused into the wood, which is like thousands of micro tent stakes. And if the surface is wiped clean before it cures, there no significant weak layer of resin left to bond to. It’s just primed with resin.
Hello can you please tell if i can coat the first layer of fiber glass with epoxy and later layers with polyester as epoxy is expensive
What I’ve read is that epoxy bonds to polyester, but polyester does not bond well to epoxy.
No. Proper Epoxy will stick to anything even glass and diamonds they use it to set polished diamons it has the most tenacious bond known and works on anything and bonds to poly and vinyl resin better than they do to themselves. The problem is whan you use proper epoxy for a fix you cannot use poly of vinyl over the top as it hasn't got the ability to bond to glass, diamond or pure epoxy resin so you need to either use a fairing filler with the final epoxy layer even coloidal silica and sand that back before applying the poly or vinyl or you can sand the bare epoxy barrier coat back to around 190grit max (240grit can just about make enough grip if you keep using fresh pads) and apply an adhesion promoter from a can or spray gun, do two coats of adhesion promoter maybe 30 mins apart and ignore the 10-15 between coats that it says on the data sheet then apply your poly or vinyl directly over it. Another acceptable method is to 40-80grit the epoxy then soak it with Acetone repeatedly, dry it quickly with air hose then fire the poly or Vinyl resin on while it's in a state of "acceptance"
The problem you have is that proper epoxy is really good at resisting chemicals and it's only too willing to accepting poly based paints but it's because they are heavily saturated with xylene etc and by the nature they bond to the surface not just themselves. Poly resin and vinyl bond mostly to their own.
@@bigduphusaj162 thanks for detailed explanation :)
I would probably automatically go with the best performing product despite material costs because I would assume the major cost would be the labor and not the materials and I would prefer to avoid doing the repair a second time.
The video is hopefully demonstrating that there is some nuance to what the best performing is - depending on the situation.If you use epoxy on black painted hull in the tropics the whole thing can start melting in the sun. This therefore isn't the best performing product.
Thanks! Great Video!
Great info.
Thanks.
Right after I finished fiberglassing my plywood boat with polyester resin and cloth,I heard that the cost of epoxy was coming down to near the cost of polyester! I don’t know this for sure. But now it’s too late. I will just have to assume it’s going to hold up.
There are some advantages to using polyester resin over epoxy - that aren’t to do with cost. These are summarised at the end of this video.
Epoxy is now the same price as polyester in my country%
I wonder why you did not wet out the the plywood before laminating, best practice says you should. If you had the results would be much different but the epoxy will always be better. When you use epoxy you also get a much better moisture barrier, critical when using timber in a marine environment. As we all know you can't buy quality resins cheaply hence the price difference between poly and epoxy.
Thanks for your comment. Perhaps you should look again at this video. I did wet out the plywood before laying up. Epoxy is an excellent resin, but not necessarily always the right choice.
SYSTEM 3 of Seattle
《 2to1》 [resin , hardener]
You're not supposed to use any of them for repairing teeth.
hi can i just put Fiberglass resin over ply no matting
Hey, there is Epoxy resin, Polyester resin, And Polyurethane resin. There is no fiberglass resin as far as I'm aware. The 'Fiberglass' part is the mat.
You can apply a resin directly to your wood surface. This would make the wood waterproof and it would give it some extra strength.
HOWEVER; As far as I'm aware the mat (which is the fiberglass part, not the resin) is what gives laminated materials their real strength. So it seems that it really is worth it to put the fiberglass mat down if you need strength especially bending resistance.
Fiberglass mat is much cheaper than resin anyway, so you might as well. 👍👍
Like paint?
@@seaschool_ yes
@@Farmer2492 I wouldn’t. It’s too brittle without being bound with matting. If you do use resin as a coating like this you use flowcoat, which is similar to gelcoat. When this is painted directly onto wood (rather than laminate over wood) it will often crack quickly.
@@seaschool_ thank you i might just put marine Varnish over it probably 8 coats will that work better
My 50 year old plywood dinghy is still holding together well so I think polyester is good enough for this purpose. I avoid epoxy because the fumes are horrible and I end up looking like the elephant man 🙂
It's all changed since I was a boy 1960s
Shame you didn’t do the lain poly properly. Ie prime the ply with poly thinned with styrene.
So is that what plymax is
One reason I made the video was to show how important it is to prime the surface of the ply before using polyester. Prymax one way of doing this. Your method is another.
Great overall but don't you think pouring sand into a bucket to test more precisely the weight of the breaking strength would be, rather than 2 bricks versus 4 bricks? PLUS, there is something else you didn't discuss which is that epoxy is superior in preventing rot. West System did surveys of 40 year old epoxy wood boats that had few problems. Most 40 year old polyester fiberglass encapsulated boats have rotted wood inside.. By the way to give you an idea of the spying tht goes on, while I was watching this, an epoxy ad interrupted the video!
Thanks for this. I like the sand idea - although I would have needed a lot of buckets to get 30 kilos! Regards to rot, that occurs because of delamination allowing moisture in - so bond is crucial to this
@@seaschool_ Actually, polyester resin fiberglass can suffer from osmosis and this is where moisture enters the layup. It is more brittle as well.
@paulbriggs3072 Thanks for your comment. Did you watch the whole video?We discuss water resistance later in this video. We'll be conducting some tests soon on how brittle they are comparatively, as well as some tests on how high temperatures can cause epoxies to fail prematurely.
This is a great informative video thanks. Unfortunately so much offered opinion on the net is from old parrots.
polyester resin is JUST for Layup, it is not designed for structural strength on bulkheads s similar, if you need to add strength to a frame or bulkhead apply more wood using epoxy or sheath in epoxy. you always Layup with Poly and Glue with epoxy.
Most production boats are built with just polyester against plywood - that's why I did this test. I agree that using polyester resin as a glue in this way is not the best construction method.
Epoxy glass may be very strong, but being that much stronger than ply, why not use poly.
Because the epoxy is stronger than wood, and the polyester is weaker than wood. The glass to glass bond is stronger too, and the wood is protected from rot with epoxy. West System did assessments of 40-year-old epoxy-over-wood boats which had little or virtually no rot. Polyester fiberglass boats of that vintage all have rotted wood stringers.
so not testing vinylester...
Not for this one - I wasn't too worried about it for laminating onto ply - but we'll include Vinyl for the next one which is about laminating onto old glass
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