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72" yak dive under power

 
Old 04-16-2006, 09:08 PM
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daveopam
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Default 72" yak dive under power

Reza, thanks for your help on the flat spins. I still have not nailed the sweet spot but with 5 more flights on it it's getting better. Using less ELEV is helping I just need more stick time.
Today as I flew I noticed that when putting along straight and level. When I advanced the throttle the plane would pull down about 18". Do you think I have some strange thrust angle in the fire wall? Or could it be CG related? I have been trying different props and the CG is a little AFT of the line. It will climb hands off inverted. Under full power it will almost do a big loop hands off inverted.



Thanks David
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Old 04-16-2006, 09:29 PM
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Default RE: 72" yak dive under power

daveopam, check for down thrust. my 72 had alot of d thrust built in and wayne said it should not have any. so i removed it a now it flys great. i think a few kits were built wrong with the d thrust so check it and set it to 0 and let it rip.

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Old 04-17-2006, 11:32 AM
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Default RE: 72" yak dive under power

Thanks Randy I will give it try. Did you mesure by leveling the wing with the table and then putting a square to it? I have an incidence meter.

David
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Old 04-17-2006, 01:30 PM
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Default RE: 72" yak dive under power

Hi David,
You shouldn't have any down thrust. Only right thrust. Please check and let me know if you need any help. Keep me posted.

Thank you,
Reza
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Old 04-17-2006, 01:54 PM
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Default RE: 72" yak dive under power

Thank You Reza. I will check it Tuesday.


David
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Old 04-17-2006, 03:36 PM
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Default RE: 72" yak dive under power

wayne told me to level the hatch line and then check for down thrust. let us know what you find

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Old 04-18-2006, 11:53 AM
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Default RE: 72" yak dive under power

There is some down thrust in this airframe. I dont know the degrees but it is 1/4" at 6" using two straight edges. I need to do some repairs then I will shim the motor up.
Thanks everyone for helping.

David
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Old 04-18-2006, 11:55 AM
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Default RE: 72" yak dive under power

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Old 04-21-2006, 08:48 PM
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Default RE: 72" yak dive under power

daveopam, what did you find wrong with your yak?


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Old 04-22-2006, 09:27 AM
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Default RE: 72" yak dive under power

The fire wall has some down thrust is it. This is what gave me several problems. Besides the pull down under power. It would tuck to the belly on left and right knife edge. It would also climb big time when inverted. I knocked the gear out of it so I have a little work to do on it. I was just going to shim the mount with washers. After looking at it I am a little concerned about doing it that way. I think I may pull the mounts and sand the back of them to get the zero thrust I need. Do you think that's the way to do it? Or should I just put some washers under the bottom?
I have shimmed one with washers in the past but it was a soft mount. It only contacted the firewall at the bolts any way.

David


I should also say that QQ has been very good to me dealing with this problem. His customer care is #1.
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Old 04-22-2006, 02:24 PM
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Default RE: 72" yak dive under power

i just shimed mine with washers and have burnt around 4 gal of fuel through her with out any trouble. if you sand the mount be careful not to change the right thrust.

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Old 04-23-2006, 09:47 AM
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Default RE: 72" yak dive under power

I think I will start by trying the washers. Thanks for your help Randy.



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