Another EPP F-117

anything to do with foam or depron models
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RocketManRC
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Re: Another EPP F-117

Unread post by RocketManRC » Sun Oct 02, 2011 8:58 pm

I really would like to build a scratch built airplane again soon...

I had a productive weekend finishing several long term projects and fixing a lot of the aircraft that needed some attention.

Now I have a month of testing to do. lol.
Rick MacDonald
May you live in interesting times!

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Paul E. Wogg
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Re: Another EPP F-117

Unread post by Paul E. Wogg » Tue Oct 04, 2011 5:06 pm

Question, Curiosity :geek:
If I recall, these planes are inherently unstable, and require fly by wire with a computer stabilization system,
Are the foamies also difficult to fly?, or is it not equivalent in scale?
If they are difficult....would a gyro help?

Paul
3 point landing! 3/100 that is.
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karlpenney
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Re: Another EPP F-117

Unread post by karlpenney » Tue Oct 04, 2011 7:17 pm

I expect this one will be pretty tame. Should fly similar to the EPP F-22.

Gyros on elevon planes are a bit tricky to implement. You have to angle them, I think around 45 degrees, due to each servo controlling both pitch and roll.

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yorcram
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Re: Another EPP F-117

Unread post by yorcram » Wed Oct 05, 2011 8:26 am

The real plane (and most modern fighters) have a rearward cg. This makes them more maneuverable, but needs computers to keep making constant small adjustments for control.
On our models we move the cg forward for stability.

marc
Plane Crazey :D

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Paul E. Wogg
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Re: Another EPP F-117

Unread post by Paul E. Wogg » Wed Oct 05, 2011 8:49 am

Thanks for the clarification!!
Paul
3 point landing! 3/100 that is.
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saboo
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Re: Another EPP F-117

Unread post by saboo » Wed Oct 05, 2011 2:26 pm

Moving the CG fore and aft only affects the longitudinal stability. Roll stability is affected by Vertical CG vs vertical height of center of lift. Yaw stability is affected by lateral or side areas location versus center of lateral area.

A prime example are the high wing planes like a Cessna 172. Straight wing. Virtually no dihedral. All lift forces originate above the vertical CG. The CG position generates a pendulum effect and thus roll stability. The opposite of this is the low wing Cherokee. It has a lot of dihedral. This helps two ways. Dihedral raises the centre of lift vertically. Also the CG of the fuselage and load is lowered versus the CG of the wing alone. The Cherokee needs the dihedral for roll stability. If you had too much dihedral the plane would be hard to roll. The 172 uses the straight wing to reduce roll stability generated by the high wing to offset the increased stability from the low CG.

An extreme example of this is the C-5a Galaxy. It has anhedral. This is to lower the centre of lift versus the vertical CG. Imagine if there is a 60 ton tank sitting in the cargo area of a C-5A. The CG is so low the plane would be difficult to roll without the anhedral.

A fighter with this is the F4 Phantom. Low to mid wing but a virtually straight wing and anhedral tailerons. The full size 117 has flat straight wing, high CG, and uses fly by wire and electronic stabilization.

So with the foam 117, you can affect the stability just by where you mount the battery. Above the wing reduces roll stability, and below increases it. ( pendulum effect ) Change the side area forward versus aft and you affect the yaw stability. The position where the thrust of the motor is on the airframe also affects yaw stability. Further aft decreases yaw stability particularly if forward side areas are increased.

So if Karl can mount some kind of computerized Inertial measurement unit to control stability, he can make it so unstable that without the IMU it would be difficult to fly. So instead people make the models stable. Position longitudinal CG for pitch stability, vertical CG for roll stability, and lateral or side areas for yaw stability and we have an easy to fly plane.

Saboo
Nothing like the smell of electrons in the morning ;-)

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Paul E. Wogg
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Re: Another EPP F-117

Unread post by Paul E. Wogg » Wed Oct 05, 2011 5:04 pm

Thank you Saboo
This makes it much clearer....well explained!
Thanks!
Paul
3 point landing! 3/100 that is.
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karlpenney
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Re: Another EPP F-117

Unread post by karlpenney » Sat May 26, 2012 1:16 pm

After 7+ months of procrastinating, I finally got around to finishing this one last week! With a small 3S 460 battery the flying weight will be 239g.
F117-1.JPG
F117-2.JPG
F117-3.JPG

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MarkL
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Re: Another EPP F-117

Unread post by MarkL » Sat May 26, 2012 2:00 pm

Looks good!

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