Plane descending too fast

Polar
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Re: Plane descending too fast

Post by Polar » January 28th, 2019, 8:29 am

Ah, I see. Thank you for your thorough explanation.

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Re: Plane descending too fast

Post by bjt4888 » January 28th, 2019, 9:17 am

Polar,

If you want more info on winding to near maximum and backing off, I wrote a fairly detailed response abou this in the 2015 WrightStuff forum in a topic named “Winding”. This is a short topic and reads pretty quickly. My detailed response is one of the last posts.

Good question. Keep digging and researching.

Brian T

Polar
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Re: Plane descending too fast

Post by Polar » January 28th, 2019, 5:25 pm

bjt,

I found your article and it was very helpful. I will incorporate that technique into my testing. Thank you

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Re: Plane descending too fast

Post by NigerianScammer » February 23rd, 2019, 5:53 pm

bjt4888 wrote:Bitconnect,

Also, your decalage angle is greater than recommended in the FF instructions. Every 1/32” difference in this angle will significantly change how the airplane flies. The stab should have a slight left panel washin and the stab in total should have 1/32” positive incidence (LE higher than TE).

Good luck and good flying.

Brian T
Why would you put down trim on stab?wouldn’t you want a neutral to slightly negative incidence to induce lift? At least for me i put about 1/32” negative incidence trim on the stab and my plane flies pretty good. If I try to put it neutral the plane doesn’t climb as much.

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Re: Plane descending too fast

Post by bjt4888 » February 23rd, 2019, 6:36 pm

Nigerian,

Slight positive incidence in the stab is a standard trim strategy for indoor models with heavy wingloading. F1M models use this trim sometimes. The FF designs have use this trim strategy effectively in the past too. Negative stab incidence does not inhibit the lifting character of the stabilizer. When this stab trim is used, corresponding increased positive wing incidence is necessary. The end result of this trim is the motor stick flies more parallel to the ground, possibly reducing potential for propeller stall.

Remember, incidence angles, and resultant decalage angle is not the same as angle of attack. It is angle of attack (flying surface angle relative to the free stream) that is related to lift and drag. Read about these terms on the NASA Glenn Research Center student pages here:

https://wright.nasa.gov/airplane/lifteq.html

Brian T

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Re: Plane descending too fast

Post by bjt4888 » February 23rd, 2019, 6:38 pm

Sorry, should have typed “... slightly positive stab incidence does not inhibit...”

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Re: Plane descending too fast

Post by NigerianScammer » February 24th, 2019, 12:09 pm

bjt4888 wrote:Nigerian,

Slight positive incidence in the stab is a standard trim strategy for indoor models with heavy wingloading. F1M models use this trim sometimes. The FF designs have use this trim strategy effectively in the past too. Negative stab incidence does not inhibit the lifting character of the stabilizer. When this stab trim is used, corresponding increased positive wing incidence is necessary. The end result of this trim is the motor stick flies more parallel to the ground, possibly reducing potential for propeller stall.

Remember, incidence angles, and resultant decalage angle is not the same as angle of attack. It is angle of attack (flying surface angle relative to the free stream) that is related to lift and drag. Read about these terms on the NASA Glenn Research Center student pages here:

https://wright.nasa.gov/airplane/lifteq.html

Brian T
Ok thanks, I’ll try it. I usually have trouble getting my plane to lift, especially with a flare propeller, and I put negative incidence to help it rise. Would this mean if I increase stab incidence I would have to seriously compensate on the main wing?

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Re: Plane descending too fast

Post by bjt4888 » February 24th, 2019, 4:31 pm

Nigerian,

Yes, slight positive stab incidence requires slightly more positive wing incidence. Compare this trim to what you are using now (slight negative stab incidence along with a corresponding wing incidence that gives good flight character). Compare to see which trim gives the best duration.

This trim difference comparison is interesting, but, if I were you, I would just stay with what is working for you now and focus your time on testing various rubber thickness (actually density, not thickness) and length and various propeller styles (flaring for sure) and blade pitch.

Brian T

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Re: Plane descending too fast

Post by NigerianScammer » February 25th, 2019, 4:20 pm

Ok thank you, i’ll keep testing and see what happens

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