Wright Stuff C

lechassin
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Re: Wright Stuff C

Post by lechassin » February 25th, 2020, 12:59 pm

Interesting. Monoplane, if I recall correctly? I confess I would not have predicted that the bipes need a more conservative CG nor do I understand why, now that I know it's the case.

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Re: Wright Stuff C

Post by coachchuckaahs » February 25th, 2020, 2:41 pm

lechassin wrote:
February 25th, 2020, 12:59 pm
Interesting. Monoplane, if I recall correctly? I confess I would not have predicted that the bipes need a more conservative CG nor do I understand why, now that I know it's the case.
Ours is a bipe

Coach Chuck
Coach, Albuquerque Area Home Schoolers Flying Events
Nationals Results:
2016 C WS 8th place
2018 B WS 2nd place
2018 C Heli Champion
2019 B ELG 3rd place
2019 C WS Champion
AMA Results: 3 AAHS members qualify for US Jr Team in F1D, 4 new youth senior records

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Re: Wright Stuff C

Post by calgoddard » February 25th, 2020, 5:45 pm

In the case of exceptional students with expert coaches, like coach Chuck and his students, its probably OK to compete with a biplane under the WS 2020 rules.

For all others, I recommend competing with a monoplane under the WS 2020 rules.

A biplane suffers aerodynamic interference between its two overlapping wings. The high-pressure air below the upper wing and the low-pressure air above the lower wing tend to cancel each other out. Because of this aerodynamic interference, a biplane does not obtain twice the lift of a monoplane having only half the wing area of the biplane. Any additional lift generated by the second wing of a biplane is largely offset by its significant additional drag.

There are many other very significant disadvantages of utilizing a biplane configuration under the WS 2020 rules, as explained in detail in my December 10, 2019 post.

I note that Troy's A and B teams are competing with monoplanes in WS this year. If I am not mistaken, Troy has won Nationals in Division C at least ten times. Troy was always very tough competition for the WS teams that I coached.

Coach Chuck - I really enjoyed your article in the recent edition of the NFFS digest about the junior F1D team. Good luck in Slanic.

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Re: Wright Stuff C

Post by coachchuckaahs » February 25th, 2020, 7:47 pm

Thanks Cal! The guys at indoor flying tonight were having the kids autograph the magazine!

Coach Chuck
Coach, Albuquerque Area Home Schoolers Flying Events
Nationals Results:
2016 C WS 8th place
2018 B WS 2nd place
2018 C Heli Champion
2019 B ELG 3rd place
2019 C WS Champion
AMA Results: 3 AAHS members qualify for US Jr Team in F1D, 4 new youth senior records

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Re: Wright Stuff C

Post by Airco2020 » February 25th, 2020, 9:01 pm

Yes, best of luck coach Chuck and team at the F1d competition. That's really Awesome!

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Re: Wright Stuff C

Post by NorCalplaya » February 25th, 2020, 9:05 pm

calgoddard wrote:
February 25th, 2020, 5:45 pm
A biplane suffers aerodynamic interference between its two overlapping wings. The high-pressure air below the upper wing and the low-pressure air above the lower wing tend to cancel each other out. Because of this aerodynamic interference, a biplane does not obtain twice the lift of a monoplane having only half the wing area of the biplane. Any additional lift generated by the second wing of a biplane is largely offset by its significant additional drag.
Would increasing the distance between the upper and lower wings aid in generating more lift? I noticed this climbing difficulty, but the cruise on biplanes is quite good. I have been able to get 1:20-1:30 at 20 ft, but at GGSO, it was difficult to rise past ~20 feet. Also, I have trimmed my plane in the 20 ft ceiling, and high torque causes power stalls rather easily.

bjt4888
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Re: Wright Stuff C

Post by bjt4888 » February 26th, 2020, 2:38 am

NorCalplaya wrote:
February 25th, 2020, 9:05 pm
calgoddard wrote:
February 25th, 2020, 5:45 pm
A biplane suffers aerodynamic interference between its two overlapping wings. The high-pressure air below the upper wing and the low-pressure air above the lower wing tend to cancel each other out. Because of this aerodynamic interference, a biplane does not obtain twice the lift of a monoplane having only half the wing area of the biplane. Any additional lift generated by the second wing of a biplane is largely offset by its significant additional drag.
Would increasing the distance between the upper and lower wings aid in generating more lift? I noticed this climbing difficulty, but the cruise on biplanes is quite good. I have been able to get 1:20-1:30 at 20 ft, but at GGSO, it was difficult to rise past ~20 feet. Also, I have trimmed my plane in the 20 ft ceiling, and high torque causes power stalls rather easily.
See this: https://www.witpress.com/Secure/elibrar ... 020FU1.pdf

If power stalling, you can try these steps:

1. Move CG forward about 1/8”. If this cures power stalling, also watch that it doesn’t create a nose-down attitude during the latter phase of flight (called the let-down phase of flight).

2. If turn circle is large, slightly tighter can fix power stall.

3. If inner wing panel washin is excessive and circle is on the large size and not rolling in much or at all, power stall can be fixed by reducing washin.

4. If propeller pitch is on the large side or flaring (if flaring propeller) is on the soft side, slightly reduce pitch or stiffen flaring to increase horsepower.

So, the fixes depend upon your design, the current state of trim and the current flying attitude. If you have time to supply more detail on trim and flight profile, we can give more specific help.

Good job posting your question. Keep up the good work.

Brian T

lechassin
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Re: Wright Stuff C

Post by lechassin » February 26th, 2020, 5:47 am

Monoplane vs biplane:

I confess that I've been trying my best on PMs to help with questions on how to reproduce our flights, anything from putting one of our props on another design to adding some of our plane's features onto another design. So far that hasn't worked for anyone and I sometimes get a comment like "oh well, it works for you", in apparent resignation.

It could work for anyone, and I disagree that monoplanes and biplanes are equal this year (admittedly that remains to be seen). However, the universal negative feedback on our bipe does have me pulling away from recommending it.

For those who wish to copy our plane anyways, l recommend that you copy it exactly. As with any competition product, every part has been tweaked for a specific characteristic and the plane is right on the edge of the rules in every way.

I'll post a plan and list each part and its rationale if desired.

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Re: Wright Stuff C

Post by CrayolaCrayon » February 26th, 2020, 6:03 am

No plane is the same... ever. Two planes built the exact same can perform very differently, from what I've experienced. You have to test what works for you. It's a different path for everyone.
Wright Stuff 2nd 2019 Nationals
USA F1D Team 2020 Image
1391 Turns

lechassin
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Re: Wright Stuff C

Post by lechassin » February 26th, 2020, 9:25 am

CrayolaCrayon wrote:
February 26th, 2020, 6:03 am
No plane is the same... ever. Two planes built the exact same can perform very differently, from what I've experienced. You have to test what works for you. It's a different path for everyone.
That's been our experience also. Even though we built our planes with machine blocks, and we built the props on a jig, slight variations means each plane trimmed differently. We also have a favorite, whose [small] advantage we don't understand. For sure the biplane is a more complicated build/trim process so that's an obstacle.

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