Sounds like a solar sail!

Found this from a site talking about drag research on class 8 trucks. Specifically studying and guessing at the drag co-efficient of the new Tesla semi.

So the product of the overall co-efficient is squared as velocity increases. Interesting to see how some shapes are literally more than 25 times less efficient than others. And then the you square the resulting difference as speed increases.

Any one of those shapes resemble anything we are talking about? Those numbers behind them matter? Implications?

The above is somewhat elementary. There are many more drag factors at play in an aircraft. Better to look at entire aircraft for inspiration. Somewhere I have the equivalent flat plate drag areas for most current general aviation aircraft. I moved to 46U recently and all my books and notes are still in boxes. Will post when I find. From memory, the Lancair type aircraft provided the first dramatic drop down to the order of a square foot or so. Planes like a Cessna 210 have 4-5 X the drag...

Klaus at SZP has done some great work/performance with his Long EZ. But, in general, the performance doesn’t scale. Many of my friends have built the Rutan canards and, while they love them, they are not very practical aircraft. They ride with me in my 182. But you can’t tell someone that their child is ugly.

I have a paper that offers a proof that you will always get better performance with a conventional or three surface aircraft (on an equal lifting surface area basis) when compared to a canard.

I don’t understand how Peter thought he would get good performance with the design — particularly by/while scaling to a wide body. Defies logic and need — does anyone really need an SUV sized cabin? The Raptor is going in the direction of the Beech Starship and we know where that ended.

But I admire Peter for his effort and wish the project well.

Best,

Tom

Anyone getting college credits toward a higher degree for participating in this thread?

The above is somewhat elementary. There are many more drag factors at play in an aircraft. Better to look at entire aircraft for inspiration. Somewhere I have the equivalent flat plate drag areas for most current general aviation aircraft. I moved to 46U recently and all my books and notes are still in boxes. Will post when I find. From memory, the Lancair type aircraft provided the first dramatic drop down to the order of a square foot or so. Planes like a Cessna 210 have 4-5 X the drag...

Klaus at SZP has done some great work/performance with his Long EZ. But, in general, the performance doesn’t scale. Many of my friends have built the Rutan canards and, while they love them, they are not very practical aircraft. They ride with me in my 182. But you can’t tell someone that their child is ugly.

I have a paper that offers a proof that you will always get better performance with a conventional or three surface aircraft (on an equal lifting surface area basis) when compared to a canard.

I don’t understand how Peter thought he would get good performance with the design — particularly by/while scaling to a wide body. Defies logic and need — does anyone really need an SUV sized cabin? The Raptor is going in the direction of the Beech Starship and we know where that ended.

But I admire Peter for his effort and wish the project well.

Best,

Tom

”From your post above.... "I have a paper that offers a proof that you will always get better performance with a conventional or three surface aircraft (on an equal lifting surface area basis) when compared to a canard."

A.) That does not even pass the common sense test.

B.) It is dead wrong. Like completely 180 degrees out.

C.) Properly designed canard/pushers don't need an equal lift surface. Does this matter? (Yes!) Why? (Common sense. Don't even have to get into the math.)”

Aero often defies common sense. Like the fact that the flaps on the Beech Starship do nothing. The proof I mentioned was done by a noted aerodynamicist with many successful designs. Most people have common sense and could not design a credible aircraft.

Am not sure of the argument; I offered my opinion on the unsuitability of canard aircraft designs. And I respect differences of opinion. If anyone feels strongly otherwise, all the best. Write Peter a big check to show you are serious. But remember that Beech Starship data point.

Best,

Tom

P.S. I should disclose that I fly a 3-Surface Aircraft, Cessna 182 with Petersen Canard STC.

That engine has flown to 30,000 feet with no ill results. Raptor being non certified can go as high as the engine would allow.

Equal surface area, does not mean the different surfaces are equal, it means that the
sum total of all horizontal surface areas are equal...


IE Comparing a conventional aircraft with a canard of the SAME total surface area

I'd be very interested in the proof so offered.

My intuition says that an aircraft would be more efficient with all surfaces lifting (canard)
that with one surface lifting and one pushing down. (conventional aircraft)

As a counter point voyager was a canard, but global flyer was not.
Also no high performance sailplanes are canards...

Am going to start calling Horse Hockey on folks a little more severely. This post above is just complete rubbish. The 18K ceiling has to do with Class A airspace certification which is much more expensive. Period.

Here is the proof.
The Unmanned version flown by Israelis has a service ceiling of 30K with the same engines.

https://en.wikipedia.org/wiki/Diamond_DA42

Anyone that wants further information here is a link to the Diamond forum where several folks talk about this very issue.

https://www.diamondaviators.net/forum/v ... php?t=4742

Thanks for sharing that info Tom,

It sounds intriguing. Can you tell where to find the paper?

cheers
--Chris

Thanks for your thoughts.

I will post the proof when I unpack my books and boxes.

The counterintuitive aspect to your statement is that the forward flying surface (or set of forward flying surfaces) always have to stall first. In a canard, this limits its lifting capability. The proof is only a page or two long... If one is designing a more or less conventional plane, the first item to address is that the tail does not stall throughout the flight envelope. And go from there...

Blue skies,

Tom

Thanks for your thoughts.

I will post the proof when I unpack my books and boxes.

The counterintuitive aspect to your statement is that the forward flying surface (or set of forward flying surfaces) always have to stall first. In a canard, this limits its lifting capability. The proof is only a page or two long... If one is designing a more or less conventional plane, the first item to address is that the tail does not stall throughout the flight envelope. And go from there...

Blue skies,

Tom

On a canard, the wing will generally be larger than necessary, since it never stalls (the foreplanes/canard will normally stall first and the overall design will usually be such to ensure this canard-first stall). The larger than necessary main wing incurs a wetted area drag penalty. This doesn't have to be a major penalty, with careful optimization of the wing for when the airplane is at its design point- i.e. cruise or whatever design point the designer has in mind.

There is the advantage of all lifting surfaces contributing positive lift and none of them negative lift, as is the typical case for the horizontal stab on a conventional airplane. The big drag advantage here is that the main wing has to create less positive lift, since it doesn't have to make up for any negative lift from the other surface, and thus the main wing also creates much less induced drag. Here's the funny counterpoint to this apparent advantage, and BT'ers who are well versed in the aerodynamic details of the Bonanza will already know this: the horizontal stab on a conventional airplane doesn't have to create negative lift! It is possible to have a conventional airplane (wings in front, horizontal stab aft) with a horizontal stab that creates positive lift and that airplane can still have natural positive stability.

So that's the standard textbook thinking on canards vs conventional airplanes, the explanation behind it, but also some additional considerations.

It depends... it always depends...




And this isn't even touching the discussion of where to put the propeller.