Tandem Wing Pusher

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Starman

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This is an idea for a tandem wing pusher aircraft with the primary design goal being minimum wing sizes.

To achieve minimum wing sizes both wings are lifting and most of the area of both wings contain large flaps, the front flap is also the pitch control. The center of gravity is a little ahead of the trailing edge of the front wing, which will carry aprox 75% of the weight, the rear wing carrying 25%.

Total wing area is about 180 ft sq and each wing main center section is 15 ft long. Added wingtips make the front span 25 ft and the rear span 30 ft.

The primary structure is a wood/carbon fiber box beam that utilizes round carbon rods the same way a wing spar does.

Edited to update drawing
 

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autoreply

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I guess, this is where to continue:
That sounds good. Do you have any idea how much a broken glider with the modern laminar cockpit would sell for?
No, that's mainly a factor of luck. If you're patient, you might not have to pay too much.

The first generation of glass (Libelle, DG-100/200, ASW-12/15/17, SH Cirrus, Mosquito) can be bought (flying) for as low as 5-10K. I now, fuselages for simulators (also often taken from wrecks) usually sell for well below 1000 Euro's.

Your searchterm is "bruch" (wrecked) on the German website, section "biete" (offered). There's currently an open cirrus in the club class section. Wings 'n wheels is the US source. Place an add for a broken glass glider and you just might get lucky and get one for a couple hundred bucks.
 

Starman

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Thanks Autoreply I will do that, it will work out nicely, I'm sure.

... and the nice thing about gliders is that some of them are two seaters

The landing gear will be tricycle, fixed at first. the rear wheels will be on a metal leaf spring located at the rear wing main spar. No doubt if it continues development it will have retracts later.

Here is the same plane with a two seat cockpit, and for those who are unwilling to take the water cooled challenge, sporting a IO-540 in the middle.

Second one is for people who like little engines, which will go all the way in the back, using a standard pusher aircraft prop/engine, or smaller auto engine.

Third one is like the first with long range tanks.

The top views are of the two seater with long range wing tips added.
 

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Starman

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What's happened with your previous project aka "Pancake"?
I dropped it because of the large size of the parts, it would be too difficult to build and handle and transport.

If I had a big shop/hanger at an airport it would be better for the flying flapjack, but I prefer making things at home anyway.
 

Jay Kempf

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Starman,

This isn't a tandem wing and isn't based on a wrecked component but it could be and I have thought of that. But the influence and layout is right spot on. In fact I removed all other protrusions and attachments from the front end for drag reduction reasons on this design. It is really easy to make the weight and balance come out once you go into this sort of design by stretching parts of the fuselage between the heavy parts.

Glider front ends leading to a clean pusher installation with all the intersections and distances from one turbulent source to another while managing aerodynamic blanking on the controls is a tricky job but taken one feature at a time it can be optimized.

I like what you have drawn so far. Right out of my own sketch book. I spent some time laying out a multiwing platform with a whole bunch of high aspect ratio wings along a common fuselage. It had outriggers that acted like fences across all the tips and also to support tail booms. Tandem and multiwing may be a way to get some efficiency in a pusher in a small footprint if all the details are managed well.
 

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Mac790

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Starman said:
...but I prefer making things at home anyway.
I know something about it, I too prefer work at home, it's also more efficient approach, you don't waste time for "journeys" home-shop-home.

Jay what engine is it? seems like a V-4, deltahawk?

Seb
 

Starman

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Your design, Jay is the kind I always liked too, and that one really looks like military hardware for some reason, did you plan that on purpose? You could definitely make that into a good all out racer too by lengthening it. What's hard to figure out is why more people don't make these types of planes. I guess only record breakers do.
 

Starman

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I could make the backbone frame out of aluminum plate, I have a bunch of it in the back yard that's perfect for it. Shiny aluminum could look nice and I can make that fast.

Concerning making the backbone out of wood and carbon fibre. I envision a couple of parallel 2 x 10 boards, wrapped in CF :)

There is a kind of manufactured wood product that has the wood fibers taken out of the wood , straightened so it's like fiberglass UNI and bound with resin, does anybody know what that is called? I'm thinking something like a box beam made of that stuff with the 2 X 10 boards hollowed out and radiused for lightness and wrapped inside and out with CF for torsional stiffness.

The wings will be built VeriEze style.

With four seat cockpit and without the wingtips:
 

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Jay Kempf

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I know something about it, I too prefer work at home, it's also more efficient approach, you don't waste time for "journeys" home-shop-home.

Jay what engine is it? seems like a V-4, deltahawk?

Seb
1.7L marine V4 like Evinrude ETEC. It will put out 150-175 HP all day long in any attitude and the altitude compensating computer is stock. Requires a custom PSRU of course. But that is where I have been looking. The idea is fixed pitch prop optimized for 300mph with excess HP so that takeoff and climb will be more than adequate. KISS right. All works in the spreadsheet I built.

And of course if you have all that kind of performance you gotta have a way to slow down and trim your AOA in all regimes. So big flaps to large deflection just like any Schreder glider.

Starman for your project you should look at buying the partial kit which would give you just the front end of an HP-18 sailplane. Already has a place to attach the rest of your design and a spar carry through and fairing for your front wing. Really like the racer concept you put up here. Been real close to there myself on the computer.
 

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Jay Kempf

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Thanks Autoreply I will do that, it will work out nicely, I'm sure.

... and the nice thing about gliders is that some of them are two seaters

The landing gear will be tricycle, fixed at first. the rear wheels will be on a metal leaf spring located at the rear wing main spar. No doubt if it continues development it will have retracts later.

Here is the same plane with a two seat cockpit, and for those who are unwilling to take the water cooled challenge, sporting a IO-540 in the middle.

Second one is for people who like little engines, which will go all the way in the back, using a standard pusher aircraft prop/engine, or smaller auto engine.

Third one is like the first with long range tanks.

The top views are of the two seater with long range wing tips added.
Starman,

Seems like the overall size is a bit much for the task. The concept is sound. A guy in the model airplane world years ago built a test platform for a canard with large flaps. The flaps were geared together such that the AOA front to rear always made the front stall first. The thing could slow down to a walk and was dead stable and had a WIDE cg range. I always like that idea. In other words you don't have to pull back on the stick to go up or down. You just pull on the flap lever and push or pull on the throttle. The B52 took off actually a little nose down demonstrating the idea.

I would chop the outer wings off at the widest trailer you want to use instead of 15 feet. That way you can just pull the outer wing sections and drive it up on. I also think that you can put the long range tanks in the outer sections so that you remove them for local fun flying. Modular, multi-task is a great concept to work towards. I have exactly the same sort of thing going. Add tail boom length and outer wing length and change the task of the craft. Those are inexpensive mods.
 

NorthwestJack

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The problem in this design(the original one listed at the top) unfortunately is the propeller shaft. I am fighting engine redrive problems in a regular tractor engine. It seems that everybody is designing redrives, but very, very few are actually working without selfdestructing. I purchased an Aerotwin engine (brand new design and I havent had if running for 4 years because their redrive keeps burning . They keep redesigning it). That is the case with many others.
Adding a long propshaft to this system will make it a nightmare to work properly. Vibration and torsional problems are not very easely fixed. I dont think there are any satisfactory airplanes out there flying this configuration.
Jacques
 

Starman

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1.7L marine V4 like Evinrude ETEC. It will put out 150-175 HP all day long in any attitude and the altitude compensating computer is stock. Requires a custom PSRU of course. But that is where I have been looking. The idea is fixed pitch prop optimized for 300mph with excess HP so that takeoff and climb will be more than adequate. KISS right. All works in the spreadsheet I built.
That sounds good Jay. However, keeping with the KISS concept, I recommend using a stock airplane engine at first while ironing out the airframe, and then add your lighter water cooled later, further back to get the CG right

And of course if you have all that kind of performance you gotta have a way to slow down and trim your AOA in all regimes. So big flaps to large deflection just like any Schreder glider.

Starman for your project you should look at buying the partial kit which would give you just the front end of an HP-18 sailplane. Already has a place to attach the rest of your design and a spar carry through and fairing for your front wing. Really like the racer concept you put up here. Been real close to there myself on the computer.
In my tandem design the front flap is also the pitch control so there is no "main" flaps. The flap on the rear wing is optional and mainly extends the area. I'll probably just make the rear wing area a little bigger and just forget the rear flap. That way the rear wing would have no control surfaces, no control runs, etc. It could have the ailerones in back if there is no flap there.

The HP 18 looks really good and it's a two seater, definitely in the running for a standardized version of this! How much would a front end kit for one of those cost, do you know?

Concerning where to cut the wings. Making it 8 ft wide so it will fit on the road is good, I could possibly make the rear wing like the VeriEze. However I want the whole center section of the front wing to be in one piece and bolted down to the frame.

In any case the first flying copy of this will be, as I said, naked, with no skins ... except for on the wings :) Basically like the UL that started this design.

So it will look like this. I think I'll make the first backbone out of aluminum plate, maybe CF for later. The cockpit is made out of an aluminum pipe, rolled up into a loop.
 

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Starman

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Starman,

Seems like the overall size is a bit much for the task.
Looks can be deceiving. Think of it this way, how big is a sailplane cockpit mounted on a broomstick? Also, the wings are minimum size.

It's not big, it's extremely small. The only 'big' part is the broomstick and it's only about a 10" sized box beam, just big enough for the intake manifold of a big V8 to fit inside it.

Your other ideas are very good and I am considering them.
 
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Starman

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The problem in this design(the original one listed at the top) unfortunately is the propeller shaft. I am fighting engine redrive problems in a regular tractor engine. It seems that everybody is designing redrives, but very, very few are actually working without selfdestructing. I purchased an Aerotwin engine (brand new design and I havent had if running for 4 years because their redrive keeps burning . They keep redesigning it). That is the case with many others.
Adding a long propshaft to this system will make it a nightmare to work properly. Vibration and torsional problems are not very easely fixed. I dont think there are any satisfactory airplanes out there flying this configuration.
Jacques
Jaques, I wish you good luck with your project. After seeing what happens to most PSRUs out there I'm left with no choice other than to acknowledge that the ones making them are incredibly dumb!

There are enough long shaft designs out there that are trouble free.
 
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