Making propellers

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CrayolaCrayon
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Re: Making propellers

Post by CrayolaCrayon » January 9th, 2019, 6:39 am

It might be a bad set. Where are they breaking? Off the spar?
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coachchuckaahs
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Re: Making propellers

Post by coachchuckaahs » January 9th, 2019, 11:14 am

Our experience years ago is that repeated adjustments to pitch did eventually lead to failure. 1 or 2 adjustments were fine. Try to spread the adjustment across the entire exposed spar rather than in a very tight region. Better to have multiple props, each set to a major pitch adjustment, then limit additional adjustments to very small amounts near the initial major adjustment.

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Re: Making propellers

Post by Bitconnect » January 9th, 2019, 12:54 pm

I’m going to try to make a prop wth adjustable pitch by having round spars that fit very tightly into a hub. This should solve my problems with pitch changing. My plane is several grams underweight so I think this is feasible right now

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Re: Making propellers

Post by Bitconnect » January 9th, 2019, 12:55 pm

The thin spar that connects to he blade snapped. One time the thick portion just started cracking and eventually broke

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klastyioer
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Re: Making propellers

Post by klastyioer » January 9th, 2019, 2:04 pm

Bitconnect wrote:The thin spar that connects to he blade snapped. One time the thick portion just started cracking and eventually broke
oh thats weird its props cause ur pitch changing
with us the only part that snaps is the connected blade to spar part like the blade will crack from impact sometimes
but yea def try making props if u wanna mess w pitch
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Bitconnect
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Re: Making propellers

Post by Bitconnect » January 9th, 2019, 6:42 pm

Yeah, I'm going to cut blades from cups, use carbon fiber for spars, and use yellow plastic tubing for the pitch adjustment part. I'm gonna try to make it lighter than 2 grams but I'll see.

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Re: Making propellers

Post by Bitconnect » January 9th, 2019, 8:01 pm

Sadly, my cups are too small. Im going to cut my blades from a cylinder of plastic from a soda can. The bottle does not taper like what you're supposed to cut blades out of, but I've read that cylinders can also be used.

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Re: Making propellers

Post by jander14indoor » January 10th, 2019, 11:46 am

If you want larger pitch changes on Ikara props, careful, very localized application of heat can avoid the stress damage others have mentioned. Also very permanent. If you do it in a jig, easy to control accuracy.
You risk melting, but you'll now that right away.
At one point there was a video, but I wasn't able to find it with a short search. Been a lot of years since I last saw it.

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Re: Making propellers

Post by torqueburner » January 17th, 2019, 8:00 am

jander14indoor wrote:If you want larger pitch changes on Ikara props, careful, very localized application of heat can avoid the stress damage others have mentioned. Also very permanent. If you do it in a jig, easy to control accuracy.
You risk melting, but you'll now that right away.
At one point there was a video, but I wasn't able to find it with a short search. Been a lot of years since I last saw it.

Jeff Anderson
Livonia, MI
We used to do it the way that Jeff mentions, by heating the spar. I have the video he mentions; pm me with your email address and I'll send you a copy.

Recently we have been making a hub from a 2 cm piece of 5/32" polystyrene tubing (Evergreen #225). Round off the ends of the spars a bit and you get a snug fit that can be easily repitched, then held in place with a bit of Ambroid or Duco cement.

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Re: Making propellers

Post by jander14indoor » January 18th, 2019, 10:46 am

I've done the same using tissue tubes for the center of the spar. I inserted a small balsa dowel for the center 5 mm or so of the tube where the wire axis ran through it for strength and left the outer 5 mm or so open to insert spars with blades already glued on. Then set pitch with a gage. If its tight enough, no glue needed to lock in place.

Jeff Anderson
Livonia, MI

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