Wright Stuff B

jgrischow1
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Re: Wright Stuff B

Post by jgrischow1 »

jgrischow1 wrote:
coachchuckaahs wrote:4. Increase SSM a little
5. Reduce launch torque a little (you have not reported launch torque)

I still think the majority of your issue is related to these two items. Of course, without video hard to be sure, but your reported CG is quite far back for this year's model, and in my experience so far, increasing torque with a small SSM results in dive. When you move the CG forward, you must increase incidence until stall begins in letdown, and then decrease just a little. It appeared that you moved the CG forward but never increased incidence or decalage to compensate. Don't be surprised if this year's model requires as much as 1cm of incidence.

Your observations of the warp in the wing, not previously seen, could make this even worse. You may have 1cm incidence at the center and half of that at the tip. You also may have a stab incidence or warp issue, which could impact decalage and mask the correct incidence.

It sounds like you need to go to the basics of trimming, step by step, starting with a thorough inspection of the plane and straitening of bent surfaces. CG and incidence adjusted at each step with low torque (50-60 winds) launch and observe letdown, get it right before moving to next steps.

Chuck
Thanks, Chuck, for your quick reply. As far as the CG goes, as I said awhile ago, when my kids altered their plane to Brian's specs, it wouldn't fly. Moving the wing up seemed to help. However, maybe they weren't trying enough other things, and the plane has been changed since then, so we will try again.

However, we also had to redo the wing covering, and either that or spraying more glue added more weight, so we had to remove some form the clay ballast on the nose. So, I think it will be even harder to get the CG as far forward as you recommend. But, we will try.

As far as torque goes, we usually launch at .15-.3. Our torque meter has broke several times though (read: my kids broke it) and the indicator wire has never been perfectly straight up and down at 12 noon, so we are estimating some what. We aren't getting close to the ceiling though at that torque, and ours is 24 ft ish, so I don't know how they will be able to climb higher for State, which has a 48 ft ceiling.

I will try to take a video tomorrow.
I tried to take a video, and of course it flew fine. However, launch torque was .15, so maybe that is the issue. My concern is still that we are leaving winds on the table, as our planes with .065 rubber land with winds remaining in a 24' gym, and if we can't launch with more torque, I don't know how it is going to climb more in a 48' gym. FFM manual says if your plane lands with winds remaining, you can go thicker and get longer flight times, but that will mean we will have more launch torque, so we will have to back off even more, etc. I guess it's just a matter of testing as much as possible until we find the optimal combo?
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Re: Wright Stuff B

Post by coachchuckaahs »

The launch torque is a function of your unwinds. The thicker rubber determines torque in cruise, late climb, and let down. Try the thicker rubber or reduce prop pitch a little. It may take a few more unwinds to get to the launch torque. Will it fly without diving at 0.2?

I would still look at SSM.

Chuck
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2018 B WS 2nd place
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2019 C WS Champion
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Re: Wright Stuff B

Post by jgrischow1 »

coachchuckaahs wrote:The launch torque is a function of your unwinds. The thicker rubber determines torque in cruise, late climb, and let down. Try the thicker rubber or reduce prop pitch a little. It may take a few more unwinds to get to the launch torque. Will it fly without diving at 0.2?

I would still look at SSM.

Chuck

Thanks for all your help. Seems like we can get it to not dive when we lower the launch torque enough. We will see what happens tomorrow.
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Re: Wright Stuff B

Post by coachchuckaahs »

Good luck, let us know

Chuck
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Re: Wright Stuff B

Post by bjt4888 »

Jgri,

Just wanted to offer your team additional encouragement and follow up. Keep up the good work.

Also wanted to reassure your team and the forum that the specs I recommended are working well. The team I was assisting this year won the Michigan State Championships with a 2:18 raw time flight under a 25 ft flyable ceiling. I was not this teams primary coach, one of the student's grandfather was the coach. He has many years of AMA outdoor flying experience and I just helped him get up to speed on indoor flying over the last two years. I practiced with the team a few times over the course of the season to help with some fine points.

This team used a design that closely followed the specs I mentioned and Coach Chuck mentioned in this thread and that looks like designs of Leo P, OlBill and Cezar Banks.

Their best flight at this ceiling height was about 2:28 and there was potential for even better duration.

Brian T
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Re: Wright Stuff B

Post by jgrischow1 »

bjt4888 wrote:Jgri,

Just wanted to offer your team additional encouragement and follow up. Keep up the good work.

Also wanted to reassure your team and the forum that the specs I recommended are working well. The team I was assisting this year won the Michigan State Championships with a 2:18 raw time flight under a 25 ft flyable ceiling. I was not this teams primary coach, one of the student's grandfather was the coach. He has many years of AMA outdoor flying experience and I just helped him get up to speed on indoor flying over the last two years. I practiced with the team a few times over the course of the season to help with some fine points.

This team used a design that closely followed the specs I mentioned and Coach Chuck mentioned in this thread and that looks like designs of Leo P, OlBill and Cezar Banks.

Their best flight at this ceiling height was about 2:28 and there was potential for even better duration.

Brian T
coachchuckaahs wrote:Good luck, let us know

Chuck
Thanks for your help, gentlemen. Our flights at State were in the 1:10-1:15 range. Not sure the exact stats my kids flew with, but in practice they were using .065 rubber and 1800-1900 winds launching at .15-.2 torque. Pre-changes, we could get in the 1:30-1:40 range. I guess I couldn't translate your advice into practical suggestions to the kids. Thanks again.
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Re: Wright Stuff B

Post by bjt4888 »

Jgri,

Congratulations on working through the science of aerospace with your students. It is a quite a challenge to get to the best solution anx you did well.

It is looking like next year's event for middle schoolers will be "elastic launch glider". If you would like to start preparing, you could read my posts in the high school forum from 2013 and 2014. I also posted quite a bit of info on this event in Hip Pocket Aeronautics Science Olympiad thread.

The info I posted for glider includes a very good basic glider, Stan Buddenbohm's excellent Little Sweep SO kit, and a plan and info to a high performance "flapper" glider. If you have questions, post them on Hip Pocket as there won't be a scioly.org wiki cor the event till the Fall.

Glider is my favorite event and I have a lot of background in it.

Brian T
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Re: Wright Stuff B

Post by jgrischow1 »

bjt4888 wrote:Jgri,

Congratulations on working through the science of aerospace with your students. It is a quite a challenge to get to the best solution anx you did well.

It is looking like next year's event for middle schoolers will be "elastic launch glider". If you would like to start preparing, you could read my posts in the high school forum from 2013 and 2014. I also posted quite a bit of info on this event in Hip Pocket Aeronautics Science Olympiad thread.

The info I posted for glider includes a very good basic glider, Stan Buddenbohm's excellent Little Sweep SO kit, and a plan and info to a high performance "flapper" glider. If you have questions, post them on Hip Pocket as there won't be a scioly.org wiki cor the event till the Fall.

Glider is my favorite event and I have a lot of background in it.

Brian T
Will do, thanks!
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Re: Wright Stuff B

Post by Almandine »

Hey guys, a couple questions,
1. Would it be beneficial if I were to adjust the pitch of my Delta Darter propeller? Would my flight times potentially change if I did change it? If yes, how would I change it?
2. Above 65 winds on my 1:15 winder, using .073", ~ 1.2g rubber, the plane starts turning left at an undesirable angle, way too tight. I suspect it being due to the torque effect. Is there any way to stop or mitigate this?
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Re: Wright Stuff B

Post by waffletree »

Almandine wrote:Hey guys, a couple questions,
1. Would it be beneficial if I were to adjust the pitch of my Delta Darter propeller? Would my flight times potentially change if I did change it? If yes, how would I change it?
2. Above 65 winds on my 1:15 winder, using .073", ~ 1.2g rubber, the plane starts turning left at an undesirable angle, way too tight. I suspect it being due to the torque effect. Is there any way to stop or mitigate this?
My team had this issue of the for a really long time now and we got it figured out only a few months ago. The turning problem could be because of the rubber band twisting the motor stick a tiny tiny bit, which would make it have a very tight turn. We ended up putting some superglue along the bottom of the motor stick, which I suggest not doing if your plane is already heavy, but it helped us be able to go past 60-65 winds.
Hope that was at least semi helpful :)
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