Wright Stuff C

[xiangyu]

Xiangyu,

Congrats on building the biplane. Did you have the following all exactly per plan: CG, wing incidence and wing washin? Did you install the carbon diagonal struts connecting the wing LE and TE to the wing posts exactly per the plan? If not, what does each of these specs measure and what is your diagonal strut arrangement? What is your circle size? When you changed the CG during testing, how much did you move it between each test flight (this is the key question).

Brian T

Yes, I believe I followed everything correctly. (What is wing washin?) I also played around with circle size a bit to see if that was causing the problem and it appears that it's not. Normally I would make the circle size with diameter the width of a basketball court. When we played around with CG, we tried a different variety between small adjustments and fairly large adjustments. After playing around with CG I bit I am generally able to make the plane fly level, but again it just doesn't climb and whenever I try to change something to increase the climb, the plane just stalls out. One key observation that makes my bi plane different from the monoplane is that my bi plane has less weight at the nose since with two wings it is heavier so I had to get rid of some of the clay to keep the plane around 8g.

Thanks for you help!
Xiangyu

[bjt4888]

Are you verifying the CG with the motor installed per page 14 of the instructions? Is it 1.8” forward of the wing TE? Be sure as this year’s design is extremely sensitive to CG placement. 1/8” off will cause poor flying.

Washin is the slight “wing warp” referred to on page 15 of the instructions. The inner wing relative to the circle direction should have the TE 3/16” lower than the LE. The removable shim is placed either under the bottom edge of the front of the “wing mount” wood strip and this change in placement of the shim will alternately twist the wing to washin either the right wing or the left wing. This twist or washin on the inner wing (again, relative to the circle direction) will allow the inner wing to provide enough lift to prevent rolling or diving to the floor. The correct washin is critical to achieving a decent climb.

Measure the washin by eye or by gently setting the lower wing against a flat surface and using a ruler.

Brian T

[bjt4888]

...removable shim either under the bottom edge of the front of the wing mount wood strip or the bottom edge of the back of the wing mount wood strip...

[bjt4888]

...or, removable shim under the bottom edge of the rear of the wing mount to washin the right wings and under the top edge of the rear of the wing mount to twist washin into the left wings (this is the actual method written on the plans; the above method will also work, but I'd go with this plan recommended method)...

[Airco2020]

I know I saw a reference to gear boxes early on this year. I was thinking of exploring that idea further but wanted to make sure nobody saw any rules preventing their use? I don't see anything, but wanted to check before I spent a lot of time exploring.

[bjt4888]

Air,

See gearbox discussion beginning with reply #55:

https://www.hippocketaeronautics.com/hp ... c=24586.50

Brian T

[Airco2020]

Air,

See gearbox discussion beginning with reply #55:

https://www.hippocketaeronautics.com/hp ... c=24586.50

Brian T

Thanks, I knew I saw that somewhere. Any comments on if this is in the rules? I don't see anything prohibiting a gearbox - I just want to make sure I'm not missing anything. Any opinions appreciated.

[bjt4888]

Air,

Of course, this is just my opinion, but I don’t see that the rules would disallow a gearbox. Note the comments in the Hip Pocket thread are from World Championship level modelers and professional engineers. I don’t have direct experience with this strategy.

Brian T

[FranklinHung]

I know Freedom Flight Models has 3 different size rubber included in the kit. Does anyone know those 3 sizes? Thanks!

[xiangyu]

I know Freedom Flight Models has 3 different size rubber included in the kit. Does anyone know those 3 sizes? Thanks!

It all depends on the plane. Ideally I believe you want to go as thin as possible as you can get more winds into it but also making sure there's enough power for the plane to decently climb.

Edit: Just realized you might be asking about the actual size numbers, sorry! I believe it's the following three: 0.058, 0.065, and 0.072. I don't have my kit with me right now but I think that what they are if someone wants to confirm it.