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World Models Spitfire Snap? - 6/15/2005 2:01:37 PM   
*Crash*Johnson*



Posts: 1089
Joined: 4/12/2003
From: Here, NJ, USA
Status: offline 		I have finally (about 6 months) gotten my Spit flying... What a journey. Engine issues, balance issues, ect ect... Anyway finally got it up in the air and it's odd....

If I bank it left and pull hard up elevator, it ~snaps~. Meaning: When I go full up elevator, it pulls a bit then snaps right (rolling over). Not too bad when ya have it up 200' and are expecting it, but when your 50' over terra firma it's frightening. I noticed the engine has a lot of right thrust in the firewall (sitting in the cockpit it goes right, I would assume that's right thrust).
Would this be the culprit? Is this common on warbirds, or Spit's in general?

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RE: World Models Spitfire Snap? - 6/15/2005 3:42:59 PM   
Ruudje


 

Posts: 107
Joined: 2/10/2003
From: Venray, NETHERLANDS
Status: offline 		Hi,

maybe your CG is too far aft.
It can also be a high speed snap. Too much speed combined with too much up elevator causes one wing to drop. Less elevator would then be the only remedy...

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RE: World Models Spitfire Snap? - 6/15/2005 3:50:29 PM   
*Crash*Johnson*



Posts: 1089
Joined: 4/12/2003
From: Here, NJ, USA
Status: offline 		I assume "aft" is tail heavy? Not possible, and if it is I am going to light the plane on fire and bury the ashes. I put a OS-FL70 four stroke on it and it took 16 oz to balance it where the manual said. So I took the engine off and replaced with a RCV 90 (added the 16oz I was looking for, and don't believe in adding dead weight...)

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RE: World Models Spitfire Snap? - 6/15/2005 4:41:08 PM   
SpitfireMKI



Posts: 1463
Joined: 7/6/2002
From: RAF Turnhouse 603 Squadron, MD, USA
Status: offline 		Ease up on that elevator chap, Ruudje is on track ! The only time you should be heavy into the elevator is when you flare.

S1

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RE: World Models Spitfire Snap? - 6/15/2005 4:48:25 PM   
Pete850



Posts: 250
Joined: 9/19/2003
From: WaterloovilleHampshire, UNITED KINGDOM
Status: offline 		Full up elevator + X = snap

Where X = warbird (and probably most planes come to think of it..........)

Cut your elevator throw right down and add 60% exponential. These birds are not sports planes or 3D'ers. Just be gentle with the controls and you'll be fine.

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RE: World Models Spitfire Snap? - 6/15/2005 4:58:34 PM   
*Crash*Johnson*



Posts: 1089
Joined: 4/12/2003
From: Here, NJ, USA
Status: offline 		The throw is set to the manual. Not much in there at all. Aint even used high rates on it. I was just mostly wondering if this was normal and if it's what they refer to as a "high speed snap".

It's not a bad flyer really, and I don't fly it like a 3-d plane (they're ok, just aint my thing [Read: I can't do the maneuvers])

Thanks for the advice guys!

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RE: World Models Spitfire Snap? - 6/15/2005 4:59:47 PM   
nmacwarbirds



Posts: 1186
Joined: 12/16/2004
From: Coltishall, UNITED KINGDOM
Status: offline 		Dear Crash Johnson
Spitfires need to be guided not forced around the sky.
My Spitfire has plenty of movement on all controls, so you need to fly these warbirds
gently and smoothly with rudder in the turns so the turns are in balance.
Regards Phil G.

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RE: World Models Spitfire Snap? - 6/15/2005 5:17:21 PM   
Tommy_Gun



Posts: 712
Joined: 4/7/2004
From: Ione, CA, USA
Status: offline 		As others posted above it does sound like too much elevator throw and possibly and AFT CofG.
Although if it IS balanced too nose heavy, the amount of elevator required to try and hold the nose up at low speed could cause an accelerated stall.
In recent model magazine articles the proper flight test methods have been illustrated to help you to determine how to make your plane fly better. They show how to check for proper CofG and engine thrust and decalage. Using those methods may be of some help for your Spitty.

I would also suggest that before you go and use the computer radio to adjust the response of any surface.
That you FIRST adjust the mechanical linkages to get as you can to the desired results. THEN use the convenience of Expo and Dual Rates.


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RE: World Models Spitfire Snap? - 6/15/2005 9:15:56 PM   
F4u5



Posts: 1819
Joined: 1/19/2002
From: Apple Valley, MN, USA
Status: offline 		You could have a warped wing...check the washout in both to see if they are close.

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RE: World Models Spitfire Snap? - 6/15/2005 9:18:33 PM   
*Crash*Johnson*



Posts: 1089
Joined: 4/12/2003
From: Here, NJ, USA
Status: offline 		How would I go about checking that? I have an incidence meter, but aint taken it out of the box. It's one of them tools I forgot I have... Mostly bought it cause I found out you can use it to check heli pitches.

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RE: World Models Spitfire Snap? - 6/15/2005 10:05:58 PM   
F4u5



Posts: 1819
Joined: 1/19/2002
From: Apple Valley, MN, USA
Status: offline 		You could use an incidence meter on the outer wing, but I have never used one. I usually just eyeball it or lay the wing on a flat surface and take measurements.

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RE: World Models Spitfire Snap? - 6/16/2005 9:13:16 AM   
luc-RCU



Posts: 256
Joined: 8/29/2003
From: Courbevoie, FRANCE
Status: offline 		well, I got the WM spit but never managed to have a nice flight with her. Seemed tail heavy, even if CG was as mentioned.
Retract supports collapsed on a landing not that strong. I gave this plane away...
The H9 warbirds fly much better and I never got retract attachment problems (though retracts are weaker)

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RE: World Models Spitfire Snap? - 6/16/2005 12:22:56 PM   
SpitfireMKI



Posts: 1463
Joined: 7/6/2002
From: RAF Turnhouse 603 Squadron, MD, USA
Status: offline 		Satisfy my curiousity, Are you just yanking back hard on the elevator expecting it to respond ?

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RE: World Models Spitfire Snap? - 6/16/2005 1:34:53 PM   
*Crash*Johnson*



Posts: 1089
Joined: 4/12/2003
From: Here, NJ, USA
Status: offline 		Perhaps my first post wasn't clear enough.

When I fly her, I go easy into the turns, kinda like it's a Zagi. Coordinate the rudder and ailerons and bank it soft and bring it around. I tried to do an S turn (I think that's the maneuver... Go inverted and up elevator to bring it around) and it snapped. It'll fly ok if I go easy on it, but I was just wondering what would cause this. Eliptical wing? Right thrust on the engine?

LUC, I hear ya about the CG. The manual had 110mm first, then amended it to 105mm. I could get the 110 easily with a FL-70 4s. It flew REAL squirrley, so to get the 105mm I had to add 16oz of engine. Seems to fly ok now, feels a bit heavy but adding a pound of weight will do that.

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RE: World Models Spitfire Snap? - 6/16/2005 1:47:36 PM   
SpitfireMKI



Posts: 1463
Joined: 7/6/2002
From: RAF Turnhouse 603 Squadron, MD, USA
Status: offline 		Ok, Up elevator refers to nose up, which would be pulling back on the stick, full down or nose down would be pushing forward on the stick.

If inverted, you push forward on the stick to maintain level inverted flight. First you will notice that you must fly at a higher angle of attack to maintain level flight, our "semi symetrical" airfoils are designed to be more efficent right side up. Therefore, your stall speed inverted is higher, now throw in nose heavy, and too much elevator and the wing will no longer want to fly.

This is not a spitfire trait, although every spit I have flown has always been elevator sensitive, that long tail makes a great lever.

S1

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RE: World Models Spitfire Snap? - 6/16/2005 2:59:07 PM   
SBR_RV



Posts: 839
Joined: 8/23/2003
From: mildura, AUSTRALIA
Status: offline 		dude what do u expect, its a warbird

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