I'd say that those two are among many important things when it comes to airplane design. This video was only focused on how airplane geometry effects weight. But the two items that you called out are excellent items to address in future videos. The flap effectiveness should be addressed within the next few months (and I've talked about it in previous videos). The thin shell buckling will be further down the road when I get to more structural design issues.
The result for wing taper at 17:19 seems intuitively low to me; enough so that I decided to run the numbers as well. Raymer did come out with only a 2.8% weight reduction, but the Nicolai/USAF DATCOM method shows a 10.8% reduction. Given that neither method considers ultralights, it will be interesting to see what you discover. I highly recommend Snorri Gudmundsson's book "General Aviation Aircraft Design" since it is approachable, very thorough, and contains/compares methods from almost every conceptual aircraft designer as it relates to GA aircraft. For those reasons it has definitely become the got-to resource on my bookshelf.
I'll have to take a look at that book. Thanks. I was also surprised at the how little weight the taper would save. But like you said, those equations were derived using GA and larger airplanes as the basis. We will see.
When playing with tail moment arms while designing control line stunt models, we generally measured from the centre of pressure (thickest point, admittedly usually somewhere around the 25% position of chord), to the centre of pressure of the tail, which is usually the hinge point, as this is where the centre of pressure would be as soon as you apply movement to the surface. Yes, this means if you build a model with flaps, you need a longer fuselage because of the CofP shift when the flaps move. This shows up if you make a flapped model's fuse too short, the turn creates a lot of drag instead of a tight turn. I actually came to this video to comment on the concept of the twin boom with split tail as shown on the avatar, to say that the torsional loads on the boom from the asymmetric tail would negate any attempt at a weight saving. But I'll definitely give these videos a look...
A cylindrical tube is an incredibly efficient means of transmitting torque. We are talking about needing only several thousandths of an inch more material to cope with the torque of this design vs a conventional design having the same diameter booms. A conventional tail still produces torsion. This is heavier, because of how small diameter the booms are, they have small Moment of Area/MOI than a larger tube/fuselage, therefore they will bend more and require more substantial wall thickness than a larger diameter boom would. Assuming both designs limit tailplane incidence changes to the same degree. The biggest flaw with a design like this, is that you eliminated the biggest advantage of having the propeller slipstream blowing over the elevator. Which would assist in raising the nose to flying attitude substantially sooner than by leaving the elevators out in free-stream airflow. E.G with airflow from the prop it may rotate to takeoff attitude at 5-10mph, vs needing 30mph without. Because the prop slipstream is likely faster than 30mph, even when Stationary.
Sucessful ultralight aircraft design is a huge challenge. Single cylinder engines did not provide safe climb performance or acceptable TBO. Sadly ultralightium (carbon) remains very expensive and difficult to use compared to aluminum, wire and fabric. I am certain a modern composite ultralight can be constructed, it will take a lot of late nights and a sharp pencil. The Thundergull and Sadler Vampite are the best examples of what can be done with conventional material, a good starting point.
That is certainly a possibility. On ultralights adding LE slats usually adds more wight and we generally don't have the weight margin to spar. It might be possible though. Junkers style controls have great lift/control but they do add a little more drag. Most of the time that is perfectly fine on an ultralight. If one of your goals is low drag then Junkers surfaces would not be the right choice.
@@Designer103 my goal actually lines up with you project #2. I have a small farm in Texas and want to be able to fly in and out of a short grass field. I'm not very good with learning new programs. Open VSP is likely beyond my capabilities. Is a collaboration possible?
That is so strange, man, the weight limitation in Brazil is to be under 350 kgs, ~~< 700 pounds, what is not light at all. We feel like ww2 wood aircraft is ok. Any way, our regulations are disconnected from the legal system as well as free from physical meaning.
For me math is just a tool. I don't love it or hate it. BUT, many viewers will stop viewing a video if they encounter math. So for those viewers I let them know ahead of time when there is little or no math so that they are more likely to stick with the video and maybe enjoy the video.
@@Designer103 I could probably add here that I was pretty bad at maths in school, but once I got into aircraft design, I could start to see the relevance and get a better understanding of how it is applied, but yeah, if someone throws up a wall of formulae, I tend to glaze over as well.
Two important things you still need to consider: composite panel buckling and flap effectiveness at low Reynolds numbers.
I'd say that those two are among many important things when it comes to airplane design. This video was only focused on how airplane geometry effects weight. But the two items that you called out are excellent items to address in future videos. The flap effectiveness should be addressed within the next few months (and I've talked about it in previous videos). The thin shell buckling will be further down the road when I get to more structural design issues.
The result for wing taper at 17:19 seems intuitively low to me; enough so that I decided to run the numbers as well. Raymer did come out with only a 2.8% weight reduction, but the Nicolai/USAF DATCOM method shows a 10.8% reduction. Given that neither method considers ultralights, it will be interesting to see what you discover.
I highly recommend Snorri Gudmundsson's book "General Aviation Aircraft Design" since it is approachable, very thorough, and contains/compares methods from almost every conceptual aircraft designer as it relates to GA aircraft. For those reasons it has definitely become the got-to resource on my bookshelf.
I'll have to take a look at that book. Thanks.
I was also surprised at the how little weight the taper would save. But like you said, those equations were derived using GA and larger airplanes as the basis. We will see.
When playing with tail moment arms while designing control line stunt models, we generally measured from the centre of pressure (thickest point, admittedly usually somewhere around the 25% position of chord), to the centre of pressure of the tail, which is usually the hinge point, as this is where the centre of pressure would be as soon as you apply movement to the surface.
Yes, this means if you build a model with flaps, you need a longer fuselage because of the CofP shift when the flaps move. This shows up if you make a flapped model's fuse too short, the turn creates a lot of drag instead of a tight turn.
I actually came to this video to comment on the concept of the twin boom with split tail as shown on the avatar, to say that the torsional loads on the boom from the asymmetric tail would negate any attempt at a weight saving.
But I'll definitely give these videos a look...
The twin tail in the picture was just for fun. Yes, this tail design would weight more to deal with the torsional load of the horizontal tails.
A cylindrical tube is an incredibly efficient means of transmitting torque.
We are talking about needing only several thousandths of an inch more material to cope with the torque of this design vs a conventional design having the same diameter booms. A conventional tail still produces torsion.
This is heavier, because of how small diameter the booms are, they have small Moment of Area/MOI than a larger tube/fuselage, therefore they will bend more and require more substantial wall thickness than a larger diameter boom would. Assuming both designs limit tailplane incidence changes to the same degree.
The biggest flaw with a design like this, is that you eliminated the biggest advantage of having the propeller slipstream blowing over the elevator. Which would assist in raising the nose to flying attitude substantially sooner than by leaving the elevators out in free-stream airflow. E.G with airflow from the prop it may rotate to takeoff attitude at 5-10mph, vs needing 30mph without. Because the prop slipstream is likely faster than 30mph, even when Stationary.
Sucessful ultralight aircraft design is a huge challenge. Single cylinder engines did not provide safe climb performance or acceptable TBO. Sadly ultralightium (carbon) remains very expensive and difficult to use compared to aluminum, wire and fabric. I am certain a modern composite ultralight can be constructed, it will take a lot of late nights and a sharp pencil. The Thundergull and Sadler Vampite are the best examples of what can be done with conventional material, a good starting point.
Very interesting
Automatic LE Slats and Junkers style control surfaces?
That is certainly a possibility. On ultralights adding LE slats usually adds more wight and we generally don't have the weight margin to spar. It might be possible though. Junkers style controls have great lift/control but they do add a little more drag. Most of the time that is perfectly fine on an ultralight. If one of your goals is low drag then Junkers surfaces would not be the right choice.
@@Designer103 my goal actually lines up with you project #2.
I have a small farm in Texas and want to be able to fly in and out of a short grass field.
I'm not very good with learning new programs. Open VSP is likely beyond my capabilities. Is a collaboration possible?
That is so strange, man, the weight limitation in Brazil is to be under 350 kgs, ~~< 700 pounds, what is not light at all. We feel like ww2 wood aircraft is ok. Any way, our regulations are disconnected from the legal system as well as free from physical meaning.
Wow. I had not heard of Brazil's regs before. Very interesting. Thank you for the information.
Why are you so down on math? You Can't build an airplane without it. Trial and guess is too expensive...
For me math is just a tool. I don't love it or hate it. BUT, many viewers will stop viewing a video if they encounter math. So for those viewers I let them know ahead of time when there is little or no math so that they are more likely to stick with the video and maybe enjoy the video.
@@Designer103 I could probably add here that I was pretty bad at maths in school, but once I got into aircraft design, I could start to see the relevance and get a better understanding of how it is applied, but yeah, if someone throws up a wall of formulae, I tend to glaze over as well.