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J.L. Frusha

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I only see about 20 degree AoA (cord line to horizon) as it sits on the ground.

?? :)

Don't need extra steps to get in, but just after take-off and until just before landing it should be able to handle much higher angels of attack, slower.
 

TFF

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Rear engine won’t be able to half hover like a Bush plane. There is no vectored thrust over wing and tail. When you see a bush plane nose high, it’s cheating. You are not going to get steep angles like a conventional setup.
 

J.L. Frusha

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Rear engine won’t be able to half hover like a Bush plane. There is no vectored thrust over wing and tail. When you see a bush plane nose high, it’s cheating. You are not going to get steep angles like a conventional setup.

One way to find out, but, get down into a pea-patch, roll a few feet, get moving and off the ground, then rotate upward,

If I can get it built, I'd be willing to bet on it. T-O & L in less than 100-150 ft.
 

Victor Bravo

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The foam models prevent you from losing money. They don't "cost", they save.

So forget about the R/C equipment for now. Collect foam plates, foam "meat trays", and foam packing materials. Cost - zero. Make free flight gliding models of the various configurations.

The free foam sheet stuff, hot and cold glue sticks, clear box-sealing tape, and small razor blades that were peeled out of used shaving razors you cracked open with a hammer. If you don't want to buy the hammer, a rock will crack the razor open pretty well too..

You may get half a million dollars in free education from the gliders, as opposed to a million dollars form the R/C powered models. But you're still half a million ahead.
 

jedi

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Sahuarita Arizona, Renton Washington, USA
STOL includes Short Takeoff. If it will fly at 45 degree AoA and can only rotate to 30 degrees the takeoff run will be much longer than it could / should be unless you have a ramp or bumps it the runway to get airborne.

That was a bit of an issue with the Sea Era. It could land at a high AoA but couldn't rotate for low speed takeoff without waves. The good news is fast on the water is ok when it is smooth. It just takes a little bit bigger lake. When it is rough 60 mph is fast on the water. Ask a Seawind pilot.
 

Martin W

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.

Such a high thrust line will require a substantial horizontal tail to counteract pitch-down tendencies .... look at tails of amphibious craft with high mounted pusher props .

best wishes in your experiments.

.
 

J.L. Frusha

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Those high CL devices create a huge need for a countering CM devices like a huge tail on a long boom with a lot of up trim. Can't be used on a flying wing.
There are numerous flying wings with little, or even no vertical stab, from the Hortons and before, through the B1 Bomber.
 

J.L. Frusha

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.

Such a high thrust line will require a substantial horizontal tail to counteract pitch-down tendencies .... look at tails of amphibious craft with high mounted pusher props .

best wishes in your experiments.

.
It's more-or-less along the top of the wing, but there is plenty of room to adjust it. This is a preliminary design, I'm learning. If I could find, say, the vertical center of mass and drag, it would be placed better.

In addition, the high-lift devices make it want to pitch up.

There are no Amphibious Ffying wings, but I supposed someone could try to add floats, or a boat-like hull.
 

TFF

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I believe he is referring to the slats requirements of normal tail to keep the plane from pitching too much as speed changes. A flying wing has little leverage with the elevators. Think of a tail as a pry bar for the wing. Flying wing has very little leverage; that is why CG is critical. A long tail can have a much wider CG range because of the leverage.
 

J.L. Frusha

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I believe he is referring to the slats requirements of normal tail to keep the plane from pitching too much as speed changes. A flying wing has little leverage with the elevators. Think of a tail as a pry bar for the wing. Flying wing has very little leverage; that is why CG is critical. A long tail can have a much wider CG range because of the leverage.
Does it matter? Maybe, but I'm not second-guessing my design, at this time. It looks right to me, except, perhaps the thrust line. That may take adjustment.
 
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Maybe, but I'm not second-guessing my design, at this time.
The early stages are the best times to "second guess". Good foundations lead to good final results.
My quick eyeball guess representing the overall CG based on a pilot and fuel being about the same weight as a legal part 103 airframe:
Red circle = pilot CG
Green circle = plane CG
Light blue = overall CG
CG.jpg
Real numbers would be much better.
My guess for the center of drag would be pretty close to the overall CG. Moving the engine below the wing looks like good idea?
 

J.L. Frusha

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The early stages are the best times to "second guess". Good foundations lead to good final results.
My quick eyeball guess representing the overall CG based on a pilot and fuel being about the same weight as a legal part 103 airframe:
Red circle = pilot CG
Green circle = plane CG
Light blue = overall CG
View attachment 120900
Real numbers would be much better.
My guess for the center of drag would be pretty close to the overall CG. Moving the engine below the wing looks like good idea?
Actually, wing CG is -0.72 inches..., forward of the LE, in the V. Corresponds closely with your pilot/fuel CG. Hopefully I can get enough balancing moment from the battery, to counter the 1/2 VW, prop and fuselage. May have to be under, or even forward of my feet Wing Calc sheet is posted above.

Don't forget, the wing is forward swept.
 

Martin W

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It's more-or-less along the top of the wing, but there is plenty of room to adjust it. This is a preliminary design, I'm learning. If I could find, say, the vertical center of mass and drag, it would be placed better.

In addition, the high-lift devices make it want to pitch up.

There are no Amphibious Ffying wings, but I supposed someone could try to add floats, or a boat-like hull.
.

YES ... your thrust line is is up on the wing ... (draw a straight line through prop and engine) ... (sideways view)

... your center of mass would be about your chest height (sideways view) ... draw a straight line through it (parallel to thrust line)

... your thrust line would be at least 36 inches above center of mass .... very high .... full thrust wants to push you both forward and nose down .... the exact opposite of what you want on takeoff and for stable flight .

.

Research early gyrocopters ... many had high thrust lines (8-12 inches) ... no tail feathers .... they tumbled out of the sky on a regular basis .... lowered thrust lines combined with horizontal stabilizers now make them very safe.

In your case the engine mounted behind the seat might work OK (similar to gyrocopters)

.

.
 

Martin W

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.

Just had a thought .... lots of (cheap) gyrocopters that have wrecked rotors from low speed rollovers etc .... buy one .... toss out rotor components and install your wing.

.
 

J.L. Frusha

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.

Just had a thought .... lots of (cheap) gyrocopters that have wrecked rotors from low speed rollovers etc .... buy one .... toss out rotor components and install your wing.

.
Probably more work to reconfigure than cutting from scratch.

I'll "Git 'er Done" as I can afford it. May be 1 piece at a time, one month at a time, but this one gets built, not reconfigured from a gyro.
 

J.L. Frusha

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Messages
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Location
Luling, Texas
.

YES ... your thrust line is is up on the wing ... (draw a straight line through prop and engine) ... (sideways view)

... your center of mass would be about your chest height (sideways view) ... draw a straight line through it (parallel to thrust line)

... your thrust line would be at least 36 inches above center of mass .... very high .... full thrust wants to push you both forward and nose down .... the exact opposite of what you want on takeoff and for stable flight .

.

Research early gyrocopters ... many had high thrust lines (8-12 inches) ... no tail feathers .... they tumbled out of the sky on a regular basis .... lowered thrust lines combined with horizontal stabilizers now make them very safe.

In your case the engine mounted behind the seat might work OK (similar to gyrocopters)

.

.
I

Thrust line is going to be high, due to the common 1/2 VW/prop combos. I'd rather not throw more weight on with a reduction drive.
 

Martin W

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Messages
209
I

Thrust line is going to be high, due to the common 1/2 VW/prop combos. I'd rather not throw more weight on with a reduction drive.
.

I still dont think you grasp thrust line vs center of mass .
I am talking about horizontal thrust line and horizontal CofM
Vertical CofG is something else

Let me greatly exaggerate ....
--- Place your engine on a mount 25 feet above your machine
--- give it full throttle
--- will your aircraft move forward or fall on its nose ???

.
 
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