Wright Stuff C

bjt4888
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Re: Wright Stuff C

Postby bjt4888 » February 4th, 2019, 6:43 am

Jinhusong,

Try testing the thickness of the plastic blades. This year, for the first time, we have discovered variations in the thickness ranging between .007” and .010”. It appears that the plastic stock is not being kept consistent as each different thickness material is that thickness over the entire blade.

The best way to determine best is to fly them.

Brian T

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Re: Wright Stuff C

Postby jinhusong » February 4th, 2019, 9:10 am

Jinhusong,

Try testing the thickness of the plastic blades. This year, for the first time, we have discovered variations in the thickness ranging between .007” and .010”. It appears that the plastic stock is not being kept consistent as each different thickness material is that thickness over the entire blade.

The best way to determine best is to fly them.

Brian T
Hi Brian,

You are right. I can even feel the difference by hand. The measured thickness matches your range.

More questions, what's the tolerance between two blades in pitch? We found 5 degree difference at the widest chord but 1 degree difference at 75%. Any method for us to test dynamic balance of the prop? I tried rotate with rubber band and winder, while hand holding the prop hanger, cannot tell.

Thanks for your help,

Jinhu




Best,

Jinhu

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Re: Wright Stuff C

Postby bjt4888 » February 4th, 2019, 10:37 am

Jinhusong,

Good job measuring and testing. The out of the box pitch variation you mention is typical. My teams will twist the center spar (as shown in the Freedom Flight kit instructions) both to get pitch to match within 1-2 degrees at a predetermined radius and to change pitch overall for testing. Also, twisting the blade in localized areas to make the pitch equal all along the blade will give you a helical pitch distribution. Helical pitch distribution is fairly efficient and equal pitch along each blade (or, at least, known pitch along each blade) improves analysis of testing results.

Good question.

Brian T

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Re: Wright Stuff C

Postby bjt4888 » February 4th, 2019, 1:41 pm

Jinhusong,

Sorry, missed the dynamic balance question. Very even pitch between the two blades, combined with perfect static balance and perfectly straight shaft will improve the let down duration. This is a very fine adjustment, of course and not nearly as important as matching propeller to rubber, having a very good propeller and winding correctly. I would gues that having a perfectly balanced propeller (dynamically and static) might be worth 5 seconds.

Brian T

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Re: Wright Stuff C

Postby jinhusong » February 4th, 2019, 1:48 pm

Jinhusong,

Sorry, missed the dynamic balance question. Very even pitch between the two blades, combined with perfect static balance and perfectly straight shaft will improve the let down duration. This is a very fine adjustment, of course and not nearly as important as matching propeller to rubber, having a very good propeller and winding correctly. I would gues that having a perfectly balanced propeller (dynamically and static) might be worth 5 seconds.

Brian T
Hi Brian,

Got it.

Thanks,


Jinhu

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Re: Wright Stuff C

Postby klastyioer » February 4th, 2019, 4:22 pm

couple questions cause im not sure the answers to these but i think i may know them

do the wing posts and stab posts sizes matter? i know in the ff kit the wing post sizes are larger than the stab post sizes, but i dont rly know why this is or what purpose it serves.

what would you do if your plane is turning but when it turns, one side is pointed inwards to the circle its making? would you offset the posts or put in less tilt to the stab?

is it good or bad to have an angle in the prop bearing? my team debates its bad, the ff kit instructs to, so im conflicted.

i always wind off the plane, but my team winds on the plane. why is it bad to? (i know but i want to prove to whoever reading this that it is not beneficial)

some ppl are saying to spend as little time w/ the rubber wound up on the plane, some are saying to take your time when winding. whats true and what isnt like so many ppl are telling me 2 different sides.
it's not about the medals; go out there and have fun. make progress, learn a few things, have one heck of a time, because that's all that matters.

Builder Cult >:)

'17 - Towers, WS, rocks
'18 - Towers, WS, Mystery Arch, road
'19 - WS
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Re: Wright Stuff C

Postby coachchuckaahs » February 4th, 2019, 5:19 pm

I'll take a stab at a few of your questions.

We don't build from a kit, and our wing and tail posts are same size. Perhaps in the kit the tail posts are smaller because they are shorter, so less bending loads? We use 1/16" square bass wood for all posts on our design.

Not sure on your turning question. Are you saying the nose points inward? Or the inboard wing tilts inward?

We have about a 2.5-3 degree angle on our prop hanger. Other designs will offset the wing posts such that the entire motor stick is angled inward, so that the bearing is in line with the rubber. Tail tilt, tail angular offset (rudder), and prop offset all affect the circle at different portions of the flight. Most designs have some implementation of left thrust for higher torque portion of flight.

Always wind off the plane! If you are properly stretch winding, the wind operation puts a significant load on the hook. The rubber is most likely to break during winding, as it is under stretch as well as wound to a higher torque than launch torque. If the rubber breaks while stretched on the plane you will often do damage to the plane. Further, if using a torque meter while winding, you wind on the torque meter. No easy way to do that on the plane, unless you have an expensive combined torque meter and winder. Damage is the primary reason, torque winding is second but still important.

I think your last question has two parts. Spend as little time wound. This is because the rubber will continue to relax, so if it stays on the plane wound for several minutes, the launch torque may not be the same as you intended/measured. You don't have time to wait anyway, at least in competition. Practice like you compete, for consistency. Second part, winding slowly. I have seen some say that you can "wind too fast", and in doing so may not get as many winds in the motor (again, it is relaxing as it gets stretched in winding). That said, we have a 10:1 winder, and we wind pretty fast. We can put on several thousand winds and then unwind, hook it up, and launch in the 3 minute setup window. If you have a 15:1 or 20:1 winder, perhaps you want to slow it a little. Try an experiment, see if you get more winds (or better time) with faster or slower winding. I am guessing on the scale of SO flying it is in the noise.

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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klastyioer
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Re: Wright Stuff C

Postby klastyioer » February 4th, 2019, 5:30 pm

I'll take a stab at a few of your questions.

We don't build from a kit, and our wing and tail posts are same size. Perhaps in the kit the tail posts are smaller because they are shorter, so less bending loads? We use 1/16" square bass wood for all posts on our design.

Not sure on your turning question. Are you saying the nose points inward? Or the inboard wing tilts inward?

We have about a 2.5-3 degree angle on our prop hanger. Other designs will offset the wing posts such that the entire motor stick is angled inward, so that the bearing is in line with the rubber. Tail tilt, tail angular offset (rudder), and prop offset all affect the circle at different portions of the flight. Most designs have some implementation of left thrust for higher torque portion of flight.

Always wind off the plane! If you are properly stretch winding, the wind operation puts a significant load on the hook. The rubber is most likely to break during winding, as it is under stretch as well as wound to a higher torque than launch torque. If the rubber breaks while stretched on the plane you will often do damage to the plane. Further, if using a torque meter while winding, you wind on the torque meter. No easy way to do that on the plane, unless you have an expensive combined torque meter and winder. Damage is the primary reason, torque winding is second but still important.

I think your last question has two parts. Spend as little time wound. This is because the rubber will continue to relax, so if it stays on the plane wound for several minutes, the launch torque may not be the same as you intended/measured. You don't have time to wait anyway, at least in competition. Practice like you compete, for consistency. Second part, winding slowly. I have seen some say that you can "wind too fast", and in doing so may not get as many winds in the motor (again, it is relaxing as it gets stretched in winding). That said, we have a 10:1 winder, and we wind pretty fast. We can put on several thousand winds and then unwind, hook it up, and launch in the 3 minute setup window. If you have a 15:1 or 20:1 winder, perhaps you want to slow it a little. Try an experiment, see if you get more winds (or better time) with faster or slower winding. I am guessing on the scale of SO flying it is in the noise.

Coach Chuck
okay thx
yea those were all answers to the questions i had in my head
and by the turn i mean the plane is tilted significantly inwards towards the circle its making when in flight
idk why ppl say that rudder offsets, changing the stab posts, and degree in the bearing is bad i just dont get that. i also dont get why you would wind off the plane and not use 2 winding rings but whatever.
i get your response to the last question completely, thanks for making it clearer cause i didnt quite understand why.
we do the same for posts but we use balsa, though bass is a good choice since they need to be quite sturdy. we dont use kits either, i just figured i would reference one.
it's not about the medals; go out there and have fun. make progress, learn a few things, have one heck of a time, because that's all that matters.

Builder Cult >:)

'17 - Towers, WS, rocks
'18 - Towers, WS, Mystery Arch, road
'19 - WS
'20 - WS, Boomilever, PPP

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Re: Wright Stuff C

Postby bjt4888 » February 5th, 2019, 7:49 am

Katie,

“Tilting inward” while circling is referred to as banking. Banking is ok, and even desireable for low ceiling sites, if it accomplishes a reduced climb rate during the early high torque portion of the flight. Knowing how much to bank and whether the bank is effective can be determined by testing. Try adjusting trim settings (rudder, stab tilt, left wing washin, etc.) moreand then less to see what works best.

Nothing is inherently bad about using rudder, various stab post length or thrustline offset. All of these are trim methods used by top level flyers. The most commonly used trim method is to use a moderate amount of all of these: wing offset, thrustline offset, left wing washin, stab tilt, tailboom offset and possibly rudder offset. Different designs and different flying conditions may require more or less of each trim setting for longest duration flights.

It is a little unusual that this year’s FF kit has stab posts above the tailboom. I suspect that this configuration may help reduce Dutch Roll that is the typically occurs in tandem airplanes; maybe. Usually stabilizer posts are below the tailboom serving the dual purpose of making stabilizer incidence adjustable and causing vertical separation of the wing and stabilizer. Increased vertical separation of the wing and stabilizer moves the stabilizer out of the turbulent air caused by the wing (the wing’s wake). I’m not recommending posts below the tailboom though as I suspect the FF configuration may help the tandem stability (also may help prevent the stab from getting bumped out of alignment on landings).

Good luck and good questions,

Brian T

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Re: Wright Stuff C

Postby klastyioer » February 5th, 2019, 9:05 am

Katie,

“Tilting inward” while circling is referred to as banking. Banking is ok, and even desireable for low ceiling sites, if it accomplishes a reduced climb rate during the early high torque portion of the flight. Knowing how much to bank and whether the bank is effective can be determined by testing. Try adjusting trim settings (rudder, stab tilt, left wing washin, etc.) moreand then less to see what works best.

Nothing is inherently bad about using rudder, various stab post length or thrustline offset. All of these are trim methods used by top level flyers. The most commonly used trim method is to use a moderate amount of all of these: wing offset, thrustline offset, left wing washin, stab tilt, tailboom offset and possibly rudder offset. Different designs and different flying conditions may require more or less of each trim setting for longest duration flights.

It is a little unusual that this year’s FF kit has stab posts above the tailboom. I suspect that this configuration may help reduce Dutch Roll that is the typically occurs in tandem airplanes; maybe. Usually stabilizer posts are below the tailboom serving the dual purpose of making stabilizer incidence adjustable and causing vertical separation of the wing and stabilizer. Increased vertical separation of the wing and stabilizer moves the stabilizer out of the turbulent air caused by the wing (the wing’s wake). I’m not recommending posts below the tailboom though as I suspect the FF configuration may help the tandem stability (also may help prevent the stab from getting bumped out of alignment on landings).

Good luck and good questions,

Brian T
thanks best of luck to your teams as well
it's not about the medals; go out there and have fun. make progress, learn a few things, have one heck of a time, because that's all that matters.

Builder Cult >:)

'17 - Towers, WS, rocks
'18 - Towers, WS, Mystery Arch, road
'19 - WS
'20 - WS, Boomilever, PPP


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