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Sockmonkey

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Development of the PAV project?

I know I'm wierd but - I really like that proposed composite flat panel construction. Still has to be my favorite proposal.

That and cruising around in a carbon fiber wobbling goblin would be sweet :wonder::beer:
The flat panel construction gives me an idea. Say the plane was made of flat panel sub-assemblies in the form of boxes and pyramid shapes put together. that way the panels also form the internal framework.
 

Hephaestus

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Lol - I was specifically referencing that flat panel PAV design :)

Build the biggest sheets available - CNC router to size/shape, interlock and affix, then you're just cleaning up the seams to finish. Like an ikea airplane.
 

rotax618

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As Vhhjr pointed out the problem of using flat panels is the very large area, the panel has to be exceptionally light weight/area. If I were designing a Faceted Sport Plane, I would use alloy tubes as Barnaby has and infill between the tubes with blue foam with a layer of light carbon on each side, the foam would stabilise the tubes so thinner walled tubing could be used to save weight and the carbon would provide reinforcement for the connections.
 

SamP

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While watching Barnaby's videos (system design), he mentioned one of the drawbacks is that the FMX is difficult to get into. The original had a hatch in the floor. I was thinking that the main landing gear could be moved aft, and shortened so that you could essentially walk up the rear and enter from the top. Your AOA would be higher, and should be able to lift off with less ground roll as well. From my understanding, the main gear is usually just aft of the CG to enable rotation. However, if you are already at a higher angle, you wouldn't need to rotate, like a taildragger.

Am I forgetting something? It's been a long time since I took airplane design courses.

The other thought I had was that the carrying capacity of the FMX-7 could potentially make it a 3 seater, or maybe even a 4 person airplane.
 

Riggerrob

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While watching Barnaby's videos (system design), he mentioned one of the drawbacks is that the FMX is difficult to get into. The original had a hatch in the floor. I was thinking that the main landing gear could be moved aft, and shortened so that you could essentially walk up the rear and enter from the top. Your AOA would be higher, and should be able to lift off with less ground roll as well. From my understanding, the main gear is usually just aft of the CG to enable rotation. However, if you are already at a higher angle, you wouldn't need to rotate, like a taildragger.

Am I forgetting something? It's been a long time since I took airplane design courses.
Dear SamP,

Your suggestion is similar to the landing gear on Ver Hees Deltas and close to Dyke Delta.
Ver Hees Deltas have large main gear legs - essentially a really big nose-wheel - plus small tial wheels under the trailing edge of the wing.

Dyke Delta has more typical tricycle landing gear, but main gear legs are so short that they pbarely keep the belly out of the weeds. The nose gear leg is noticeably longer to set the best angle for take-off. The ground angle is set at pretty mush the best angle for landings and take-offs. Dyke pilots report that they just advance the throttle and watch the airplane take-off on its own.
A major consideration is that deltas generate hellacious amounts of drag if they get too nose high, so the simple answer is to never get to deep behind the power curve. The simplest way avoid getting too far behind the power curve is to install landing gear that holds the wing at the best angle for landings and take-offs. Then they pilot does not need to change pitch angles with the wheel or control stick. Elevon trim is enough.
 

rotax618

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I don’t believe there is an “ideal” angle for takeoff and landing, especially for landing. Very low aspect aircraft can be landed with a very short roll by using the “hellacious” drag at a flare to add aerodynamic braking. I agree climbing in from underneath the craft is not ideal, if it had 2 blade prop it may be possible to lower the nose leg like the Vari/Long Eze and climb in from the nose.
 
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Dennis K

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I read Ver Hees has no interest in selling plans or kits for his two seat Delta and is looking for either a buyer or partner to continue with the project.
 

Dennis K

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I don’t believe there is an “ideal” angle for takeoff and landing, especially for landing. Very low aspect aircraft can be landed with a very short roll by using the “hellacious” drag at a flare to add aerodynamic braking. I agree climbing in from underneath the craft is not ideal, if it had 2 blade prop it may be possible to lower the nose leg like the Vari/Long Eze and climb in from the nose.
Too great an angle of attack and you drag the wing tips on the runway coming or going.
 

rv7charlie

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The designer usually knows best. For instance, what if that very high drag at high AOA won't allow the airframe to reach flying speed easily?
 

SamP

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Dear SamP,

Your suggestion is similar to the landing gear on Ver Hees Deltas and close to Dyke Delta.
Ver Hees Deltas have large main gear legs - essentially a really big nose-wheel - plus small tial wheels under the trailing edge of the wing.

Dyke Delta has more typical tricycle landing gear, but main gear legs are so short that they pbarely keep the belly out of the weeds. The nose gear leg is noticeably longer to set the best angle for take-off. The ground angle is set at pretty mush the best angle for landings and take-offs. Dyke pilots report that they just advance the throttle and watch the airplane take-off on its own.
A major consideration is that deltas generate hellacious amounts of drag if they get too nose high, so the simple answer is to never get to deep behind the power curve. The simplest way avoid getting too far behind the power curve is to install landing gear that holds the wing at the best angle for landings and take-offs. Then they pilot does not need to change pitch angles with the wheel or control stick. Elevon trim is enough.
Thanks for the references. Those are pretty cool planes as well!
 

Sockmonkey

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I don’t believe there is an “ideal” angle for takeoff and landing, especially for landing. Very low aspect aircraft can be landed with a very short roll by using the “hellacious” drag at a flare to add aerodynamic braking.
I would say that the "never exceed" pitch angle for a delta would be determined by your engine thrust, and have your prefered angle be a few degrees less than that.
 

Sockmonkey

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How about an extendable nose gear? Get up to speed then telescope the thing. Though if you're using vortex lift for STOL you're gonna need the thrust to do so anyhow.
 

SamP

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=low AoA take off/landings thanks LE VORTEX generators,
invented by Witold Kasper,BOING employer...
Cool video. Apparently the nickname of the plane was ‘Monica’, on the account of the large intake…

im not sure I understand how the LE vortex generators enable a flatter approach. My understanding is that the f-18 LE vortex generators enable high AOA because the vortex helps keep the flow attached to the top of the wing. The facetmobile needs a high AOA for slow approach and decent descent rate.
 

henryk

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understand how the LE vortex generators enable a flatter approach.
-see VORTEX AUGMENTED LIFT, Kasper, KC200 ...

 

SamP

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Wow. That wing has a lot going on. I see the apex flaps, leading edge flaps, as well as the flaperons in back.

so, trying to distill my understanding:
  1. Flying wing designs like the facetmobile generally have an airfoil shape with a low Cl vs angle
  2. This requires high AOA to reduce speed and sink rate
  3. This makes the landing gear taller, if you want to a somewhat flat deck angle
  4. Apex flaps or something like that makes for a thicker airfoil (effectively)increases the slope of the lift curve, enabling a flatter descent for a better pilot view
Sound about right?

looking at The definition of the Reynolds number, where the characteristic cord length in this case would be the fuselage, it seems that the aircraft must be operating at a high Reynolds number, and you really wouldn’t get smooth airflow anyway, so the facets would it be that big of a deal.

I just find the design so fascinating and thought-provoking. It’s helping dust off a lot of cobwebs. Thanks for the lively discussion.
 
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