Wright Stuff C

[Rossyspsce]

Rossyspace,

Good job reporting data. I don’t see that you mentioned the pitch of your flaring propeller. If the flaring propeller is performing similar to the 24 cm symmetrical propeller, you may need to increase pitch angle. We usually start by having three propellers of different pitches ready for testing and two to three different densities of rubber (more pitch usually requires more rubber density). Typical pitch/ diameter ratios to test would be in the 1.4 to 1.7 range for WS.

Also, if flaring propeller performance is similar to the symmetrical prop, maybe try sanding thinner to get more pronounced flare.

Also, 1,800 turns is only about 70% of breaking turns for a 20” loop of .094” rubber (around 2.5 grams). Get max turns up to 80 or 85% for better duration (will probably require more backoff turns and slightly lower launch torque at this turn count).

Good luck,

Brian T

By density do you mean like g/cm^3 or do you change density by thickness or other means

[coachchuckaahs]

By "density" Brian means the g/inch. This is a better measure of the rubber "width". It is influenced by the actual density (g/cc), the thickness (stock, but varies) and the witch (cut to width, but it is squishy and hard to measure).

The linear density (g/in) is the best characterization of the energy storage capacity (winds) and torque of a peice of rubber, and is more consistent than measuring "width"

Coach Chuck

[bjt4888]

Rossyspace,

Coach Chuck is right on with his explanation. If you filter for his comments and mine in this forum, you will find additional info. Knowing and selecting rubber density is critical to high quality testing and best flight times.

Brian T

[Flyingfish]

I've recently purchased flaring props, and I've heard that we're supposed to sand them? What parts should I be aiming to sand? Could someone point me to some resources or some advice? Thanks!

[bjt4888]

Flying fish,

There’s a diagram in the FF kit instructions recommending a trimmed shape and thickness distribution after sanding. Use a micrometer to test thickness as you sand.

Brian T

[klastyioer]

I've recently purchased flaring props, and I've heard that we're supposed to sand them? What parts should I be aiming to sand? Could someone point me to some resources or some advice? Thanks!

to add to what bjt said, go slow when sanding, dont go ham on the prop. i accidentally did and it ruined it so i wasted like 5 bucks...oops. but go slow and i suggest using a higher grain sand paper towards the end to smooth everything out.

[bjt4888]

Klastyioer,

Good point. We usually start sanding with 150 grit and finish with 220 and then 400. Perfectly smoothis not necessary especially if sanding the top surface of the blade. A little texture might actually improve aerodynamics.

Brian T

[Rossyspsce]

Does anyone know or is able to explain how to control the heigh the plane peaks at? Also, how to control the climb rate of the plane?

[CrayolaCrayon]

Does anyone know or is able to explain how to control the heigh the plane peaks at? Also, how to control the climb rate of the plane?

The more you dewind, the lower the plane will climb to, and the slower it will climb.

[bjt4888]

Rossyspace,

Crayola is correct, of course, backoff winding to optimum launch torque is the method to control climb height and this process does reduce climb rate. Other methods of moderating climb rate include: increase propeller pitch, reduce rubber density (roughly equivalent to thickness), trim CG further back and reduce decalage angle, increase roll by minimizing left wing washin (balancing against other turn trim) and use of a properly flaring propeller.

You will advance your knowledge of these concepts rapidly if you read this entire wiki and also read last year’s Division B WS wiki and the 2015 wiki. This doesn’t take that long as there are usually only a couple substantive comments per page.

Good luck,

Brian T