How to make a Strong but Light Motorstick

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OpticsNerd
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How to make a Strong but Light Motorstick

Post by OpticsNerd » March 17th, 2019, 4:35 pm

Anyone know a good way to make a very strong but light motorstick? I mean stronger and lighter than the FF motorstick.

coachchuckaahs
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Re: How to make a Strong but Light Motorstick

Post by coachchuckaahs » March 17th, 2019, 5:17 pm

The main thing will be balsa selection. Last year for heli, building to minimum weight was a huge challenge. We cut over 30 motorsticks from about 7-8 different sheets of wood (all contest grade), and found 3 high quality sticks in the bunch. This was just for our final build. Test weight, flex, and buckling. Be prepared to throw a lot away! You will find that even adjacent cuts from a single sheet of wood can vary considerably.

Our team just completed building Limited Penny Planes for an AMA competition. The first two were completed today, and came in at 3.1 and 3.2g. The biggest variable is motorstick. We cut dozens and tested them before selecting the ones we would build around.

With WS, you can also reinforce selectively with carbon, kevlar, multiple pieces of wood, etc. LPP requires a single solid piece of balsa.

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2016 C WS 8th place
2018 B WS 2nd place
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Re: How to make a Strong but Light Motorstick

Post by klastyioer » March 17th, 2019, 6:09 pm

i agree with coach
honestly just try a ton until you find the ones you like
also i have another suggestion but ill say it afterwards if no one inputs anything else
it's not about the medals; go out there and have fun. make progress, learn a few things and have one heck of a time; that's all that matters.

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Re: How to make a Strong but Light Motorstick

Post by OpticsNerd » March 17th, 2019, 6:28 pm

coachchuckaahs wrote:The main thing will be balsa selection. Last year for heli, building to minimum weight was a huge challenge. We cut over 30 motorsticks from about 7-8 different sheets of wood (all contest grade), and found 3 high quality sticks in the bunch. This was just for our final build. Test weight, flex, and buckling. Be prepared to throw a lot away! You will find that even adjacent cuts from a single sheet of wood can vary considerably.

Our team just completed building Limited Penny Planes for an AMA competition. The first two were completed today, and came in at 3.1 and 3.2g. The biggest variable is motorstick. We cut dozens and tested them before selecting the ones we would build around.

With WS, you can also reinforce selectively with carbon, kevlar, multiple pieces of wood, etc. LPP requires a single solid piece of balsa.

Coach Chuck
Could you please give me some advice for reinforcing the motorstick?

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Re: How to make a Strong but Light Motorstick

Post by coachchuckaahs » March 18th, 2019, 7:31 am

Most people use carbon tow top and bottom, or just bottom. You can also use carbon strip, 0.005" or 0.007". Apply with glue sparingly, or you add a lot of weight. I would not use CA for this. Use thinner Duco, or possibly 3m77 for the strips. Experiment with weight vs. Strength for amount of carbon.

Balsa selection is still important. Start with lousy balsa and the carbon won't fix it.

You can also play with section (height and width). Height is more important for bending, both for buckling and torsion. You will find you want best torsion resistance between the wing posts, and best bending in the middle. Therefore you can taper in height and width toward the ends. You may also find a larger piece of lighter wood is better than a smaller peice of heavy wood, in terms of buckling, bending, and torsion.

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: How to make a Strong but Light Motorstick

Post by jander14indoor » March 18th, 2019, 8:26 am

If you are already an advanced flyer and good builder, you should consider hollow tube motor sticks for Wright Stuff. Probably easier than finding a good solid motor stick and not much harder than reinforcing a floppy stick with carbon and keeping the weight down.
I've been using the same hollow motor stick on my Wright stuff demo planes for years. Very stiff and light. Doesn't move with much larger rubber bands than needed the past few years. Obviously sturdy enough to survive 10 years of moving the wing around.

Do a little searching around the indoor sites and you'll find instructions on building rolled motor sticks.
Mine is actually a rectangular box beam I built to see if I could. walls are less than 1/32 thick, don't remember the thickness and height, but it looks FAT compared to most of the sticks you see in kits and is just about as light.

Jeff Anderson
Livonia, MI

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Re: How to make a Strong but Light Motorstick

Post by klastyioer » March 18th, 2019, 4:10 pm

jander14indoor wrote:If you are already an advanced flyer and good builder, you should consider hollow tube motor sticks for Wright Stuff. Probably easier than finding a good solid motor stick and not much harder than reinforcing a floppy stick with carbon and keeping the weight down.
I've been using the same hollow motor stick on my Wright stuff demo planes for years. Very stiff and light. Doesn't move with much larger rubber bands than needed the past few years. Obviously sturdy enough to survive 10 years of moving the wing around.

Do a little searching around the indoor sites and you'll find instructions on building rolled motor sticks.
Mine is actually a rectangular box beam I built to see if I could. walls are less than 1/32 thick, don't remember the thickness and height, but it looks FAT compared to most of the sticks you see in kits and is just about as light.

Jeff Anderson
Livonia, MI
first sentence says it all
thats what i was going to suggest
josh finn has a good video on how to make rolled fuses if you look it up on his channel
im sure there are more resources than that tho so do some scouting around
it's not about the medals; go out there and have fun. make progress, learn a few things and have one heck of a time; that's all that matters.

Check out Klastyioer's Userpage!

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