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SPAD first flight : Problems getting nose up

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SPAD first flight : Problems getting nose up

Old 07-21-2008, 11:09 AM
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Default SPAD first flight : Problems getting nose up

Last week I finished building my first SPAD and it had its first two successful flights. A trainer called SPADET. I got the plans from spadtothebone.com. It flew great. The only problem was that it was very hard to bring its nose up. I had to give full up-elevator for it to go up, but it responded very slowly.

The airplane does not pull up nor downwards if I leave the stick in neutral position, and if I give down elevator then it responds quickly… only the up elevator responds very heavily and slowly, even when the elevator is at 45 degrees upward.

What can be de cause? What can I do so it will respond better for up elevator?

Thanks for your help!
Old 07-21-2008, 11:31 AM
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Default RE: SPAD first flight : Problems getting nose up

Where is your CG (Center of Gravity)?
Old 07-21-2008, 11:47 AM
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Default RE: SPAD first flight : Problems getting nose up

The CG is where the spar is. About 3 inches from the leading edge and 7 inches from the trailing edge.
Old 07-21-2008, 12:00 PM
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Default RE: SPAD first flight : Problems getting nose up

You might want to check how your elevator servo is mounted. Sometimes when you mount a servo on a SPAD with zip-ties or double stick tape, they tend to move a bit. It may look OK on the ground, but when you get some wind pressure against it in flight, maybe your servo is moving and not your elevator.

If your CG is good, and it flies level with no elevator input, I can't think of another reason for this behavior.

Good luck.
Old 07-21-2008, 12:39 PM
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Default RE: SPAD first flight : Problems getting nose up

ditto on whar mclina said, the control rods can be flexing also. I had that problem. I put the servo closer to the evevator to eleminate a long control rod and I actualy cut a hole in the fuse and mounted the servo. its solid now. what engine are you using, if its too small, the plane could be way underpowered. a friend of mine would get his plane into a steep fast dive and at times, the elevator wouldnt pull it up, instant lawn dart, another thing, put some skewers in the elevator @ both sides of the hinge line and across the moving part itself. make sure the control horn isnt bending the coro either
Old 07-21-2008, 01:01 PM
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Default RE: SPAD first flight : Problems getting nose up

I didn't think of the pushrod flexing. That's very likely. On long pushrods, I have run them through a couple of very small eye screws to keep them straight. If you look closely at this picture, you'll see an eye screw near the vertical stab, which keeps the rudder pushrod from flexing. There are also a series of them keeping the nose wheel pushrod straight.
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Old 07-21-2008, 04:38 PM
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Default RE: SPAD first flight : Problems getting nose up

Hola kaisven
I notice the Spaniards are doing great at the Tour de France this year. Congratulations. Your problem could be a few small ones. I notice the building directions have the elevator control horn mounted on the top of the elevator. This gives a PULL motion when up elevator is required. The PULL motion will prevent the rod from flexing in the UP elevator direction. Some people change the horn so it is under the elevator. If this is done, then everything on the control rod must be very rigid/stiff. Entiende?

The elevator itself could be flexing. A piece of round stiff wood inserted into one of the coroplast flutes near the hinge can correct this. We use bamboo rods sold for cooking meat on outdoor grills in the USA (called bamboo skewers).

It could also be that your main landing gear is a little too far back. This would make rotation at takeoff a little more difficult, and would not effect pitch in the air.

You could have a little negative incidence in the wing, or the front landing gear could be a little short. Both these things would make it a little more difficult to rotate.
Old 07-21-2008, 08:35 PM
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Default RE: SPAD first flight : Problems getting nose up

those are all very good points also. I never even thougt of the horn location. I will have to make sure that I put the horns on the pull stroke.
Old 07-21-2008, 10:33 PM
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Default RE: SPAD first flight : Problems getting nose up

what every one said plus,
On spads the ailerons need a LITTLE reflex (both ailerons up slightly). However to much of this will cause a distinct nose down force.
I did this on a Pro-Twister with very large ailerons just recently. It ran around the runway gathering "nice car" comments
a couple of twists down on both clevises and the problem disapeared. A good starting point for aileron position is even with the fuse.

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