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High speed low drag aerobatic concept

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Jay Kempf

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A couple people have asked for higher res details of my the concept in my Avatar so I am going to put up a little more detail. I can get any view of course. Span is 20FT. Not tiny but not by any stretch large.
transparent general arrangement.jpgclsoeup gear down.jpgcloseup gear up.jpgavatar.jpg
render rear 7 feb 2011.jpgcowl canopy gear up dwn rear.jpgrender 7 feb 2011.jpg
 

WonderousMountain

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Clatsop, Or
Long landing gear, How much travel does it give?
The engine is Vfour? Compact, and not much prop extension.

Looks every bit as clean and well proportioned in full scale.

As a drawing it's very heartening.
You can move you legs a little right?

Mountain
 

Jay Kempf

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4-6" or about half a tire on rising rate spring geometry with a motocross monoshock damper. This one is for mostly good grass or smooth runways.

The design is more an exploration of very good aerodynamic details on a relatively conventional powerplane, albeit pusher, many borrowed from the best designs every perpetrated. The cooling is Meredyth, the front end is right out of Glasser Dirks, the tail group obviously has P38 heritage. As outrageous as the thing ended up looking it is built up of very sane and normal components and the build is very sane and straightforward. I have done skins for large model airplanes using some one off techniques that are pretty easy to do without a full mold but with a skinned hot wired female parts. This assumes room temperature first cure of course. But the whole thing could be built one off. I can get the geometry where I need it to be in my shop. I am not worried about that.

The engine is 1.7 liter Marine powerhead with somewhere between 1.75-2.0 reduction drive and it would have to tune out at around 175HP to get me what I want. The reduction drive and prop extension are the same unit. Prop 60" plus/minus 2" or so planned. The top half of the lower unit of the matching outboard looks exactly like a good torque converter housing on a car engine so that is a likely part to harvest from. There is also a large twin cylinder snowmobile engine that would work. Also some of the larger 4 cycle jet ski and snowmobile engines look good but I particularly like the v4 marine powerheads (2 stroke) for their power to weight and modern fuel and oil controls as well as altitude compensation. Turbo of course is another way to skin the cat on 1 liter.

I built a cockpit mockup of this one and it is very roomy. Room for 6' 4" comfortably and more with a little bulkhead adjustment. One thing I really like about this thing is it can be driven right up on a standard car hauler trailer and taken home to the shop for maintenance or storage. Nothing fancy needed. The outer wings are pretty small at just over 6' long and light weight.
 

bmcj

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For aerobatics, low drag may help you on the up line, but may be a detriment on the down line. Do you have a deployable drag board?
 

Jay Kempf

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For aerobatics, low drag may help you on the up line, but may be a detriment on the down line. Do you have a deployable drag board?
Yup, but you got a big fan to idle to slow you down on the downline plus I have big flaps to big angles to provide glide slope control.

Let me clarify the aerobatic thing. I have no interest in competition aerobatics. Like many of the designs I look at I am trying to take two things, incorporate them into one and then make the composite do both really well. So this idea is to combine a very fast (300MPH WOT run) ship that will also do quite some distance at high speeds if you load it up with fuel with a nice gentleman's aerobatic sport machine for around the home airport loaded with light fuel just for play.

That was where I started. The rest fell in behind. There is a central fuel tank and one in each wing. Load the wings up for cross country. Leave them dry for short distances and yanking and banking. Fill only in the central tank, pump to and from the outers (thanks AR for that). I have also looked at having two sets of outer wings and designing around the longer of the two to make sure I have the tail volume to handle it. I also looked at just removable wing tips that would go on outside the ailerons for cross country flight, that is just to add a little more wing area to carry more fuel.
 

delta

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Brookside Utah
It loos like a nice well thought out design to me. Have you done the RC yet? I'll bet she flies good if you have.

Rick
 

Jay Kempf

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It loos like a nice well thought out design to me. Have you done the RC yet? I'll bet she flies good if you have.

Rick
Nope, no RC yet, but that is coming. I am torn between doing something like this and doing a motor glider. But I am currently clearing out projects in the shop to do one or the other.

I worked on a micro UAV project a while back that taught me a ton about telemetry and I have some access to some hardware for small autopilots and multichannel telemetry gear. So I am looking at building a test platform large scale RC rig to do some evaluations. I think I could even do a small fiber optic camera that could look at tufting from different points on the airframe and download the video. The nice thing about these little autopilots is that they also collect all the normal flight data recorder stuff and GPS tracks so you can actually measure performance instead of guessing.

The hope was to have something that had good neutral handling. That is an issue for cross country but should be good for fun flying around the patch. There are pretty good solutions for autopilots for damping neutral designs for long distance travel so you don't have to pay attention so much. Ferrying of aerobatic designs must be an exercise in concentration.
 

Jay Kempf

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Isn't this already both? With sufficient rudder authority (you already have in it), it's no more complex than making new outer wing panels is it?
Longer tail booms, a different airfoil and less HP and I think yeah it could be. I originally thought that. But this one is going to be stressed to very high Gs so I really don't think in the end that it is in the structural efficiency category that I think a glider should be. I guess it boils down to what your definition of a motor glider is. I went after my motor glider concept to explore that possibility and that one can be scaled down with removable wing tips or something to jump into this category.

It all depends on what limit of usable speeds you want to build to I guess.

Everything is a compromise for the configurator :)
 

Airbender

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Apr 21, 2011
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Roaming
Hi Jay,

A few quick ones for you. How long have you been working on this and is there a reason you have a gap between the fin tips? Roughly what capacity is calculated for fuel storage?
That is the best looking design I have seen for a while, I'll be watching this one closely - keep up the work.
 

Jay Kempf

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Hi Jay,

A few quick ones for you. How long have you been working on this and is there a reason you have a gap between the fin tips? Roughly what capacity is calculated for fuel storage?
That is the best looking design I have seen for a while, I'll be watching this one closely - keep up the work.
Hee hee, the gap between the tip fins has been debated to almost fisticuffs :) My reasoning is one of all flying surfaces back there so not wanting to join the moving tips. The compromises while debated to death are really not that earth shattering.

I have been working on this design from a single envelope (literally) sketch about 5 years ago. That back of the envelope sketch was a fixed gear single bulkhead simple aerobat pusher. It has been in the 3D modeler in two versions for over two years. Lack of funds is currently holding any project back. The concept has become a little more elaborate as it evolved from it's start but still is faithful to the original thought.

Fuel is in three tanks. One in the central fuselage and central wing between the pods (about 15 gallons) in a tall but narrow fore/aft config with the back of the tank on the CG bulkhead. Then there are two wing tanks with just a single pump for transfer for each wing. Each wing tank gives an additional potential for about 12 gallons for a total of around 40 or 240 lb of fuel at full load for LONG cross country flights if necessary. The plan for fuel being a small single tank for around the patch flying for fun and a more span distributed large load for long travel. I don't really want to go that far or long in one flight but the potential is there so there is no reason not to build to that max gross takeoff weight. It is probable that a slightly larger span second set of outer wings makes sense for that larger fuel load and that has been factored into the tail volumes and overall strengths.
 

LOFT

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I like the layout. I've always been a fan of the Sadler Vampire. The separated tail though... hahaha I'm sure you've had enough "opinions" by now.
 

Jay Kempf

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I like the layout. I've always been a fan of the Sadler Vampire. The separated tail though... hahaha I'm sure you've had enough "opinions" by now.
Yup, I always thought of this as a Sadler Vampire on steroids. Or a Sadler Vampire if you didn't try to get it into the ultralight category.

Nope, I need more opinions hahahahahahaha
 

ThadBeier

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I really like this style of airplane. I am very curious why you have the break in the tail surface -- why not have it be a straight 45 degree angle? I suppose that would require it be a nosedragger...but you seem to be going to extreme lengths to get the gear far enough forward to be a taildragger already.

Also, there was a formula 1 race-plane design called "First Class Trash" back in the mid-'80's that was a very similar concept -- have you seen that? I confess I only saw it on a tshirt....but it made an impression!
 

Jay Kempf

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I really like this style of airplane. I am very curious why you have the break in the tail surface -- why not have it be a straight 45 degree angle? I suppose that would require it be a nosedragger...but you seem to be going to extreme lengths to get the gear far enough forward to be a taildragger already.

Also, there was a formula 1 race-plane design called "First Class Trash" back in the mid-'80's that was a very similar concept -- have you seen that? I confess I only saw it on a tshirt....but it made an impression!
The transition of the lower fin is for a direct load path against a tail strike putting the boom in bending only. Small planes with forward pilots do not stay on their nose wheels when the pilot is out. Tail dragger is the better compromise. And the added benefit of the tail dragger is that it is less gear doors to seal and there are no gear doors on the most critical part of the laminar flow portion of the fuselage in this configuration. I do have a tri gear version drawn. In a tri gear version I would not have the vertical portion of the tails.

Can't find first class trash pictures anywhere. I would like to see that.
 

Jay Kempf

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Jay I like your thinking on the 2-stroke outboard engine...these are amazing engines...especially with the direct injection...

Every bit as fuel efficient as a 4-stroke but with 2-stroke lightness and simplicity...

I particularly like the Evinrudes with the ETEC or wahtever it's called...also used on skidoo engines...

Only problem with outboards is the cooling...
ETEC is the best of the choices. And turbocharging is good too. What's the problem with cooling. It's just a flow rate and a heat flux to match a radiator to? Waterpumps are trivial accessories to add. I hear that cooling thing all the time but the engine meters the cooling flow even when it is being delivered unlimited potential supply. The cooling channels in the head and block are no more severe than any similar engine at say 100/liter.
 

ThadBeier

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I'm afraid First Class Trash was from the days before the widespread internet. That time will be called the Dark Ages soon enough...there are just not that many pictures from back then! I can't find any mention anywhere either. I did have a long conversation with the T-shirt wearer at the time about the plane, it was being built by a collection of airplane nuts in the Silicon Valley.
 
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