RC prop Help a first time builder

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billj

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Jun 1, 2016
Messages
16
Location
Virginia
The pilot. Youra. DEADDUK seems to like it ok...lol
 

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BBerson

Light Plane Philosopher
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Dec 16, 2007
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Location
Port Townsend WA
The new prop should be same as old prop to start from. Then if the static rpm of the old was incorrect, make a new prop to fit the desired manufacturer static full throttle rpm. More pitch or diameter will decrease rpm and power.
 

Martti Mattila

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Feb 24, 2021
Messages
113
Oh boy, in my youth we had to carve our rubberband propps from balsa, that teaches something. Now doing props for VW.s and Rotaxies. There is a plenty videos about prop making in ytube but learn to balancing that is important. Propmaking is the skill what is worth to learn, after that you dont have time for anything else.
 

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TFF

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Apr 28, 2010
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Memphis, TN
My dad could carve a pretty balsa prop. And I could break them. I wish I had one now.

If you have a duplicator you are going to have to carve your pattern. There are plenty of how to carve props you can Google. Essentially you mark the leading edge and trialing. There is simple math to figure out there the lines go for pitch. Then you whittle. It’s not going to be a one and done. Five and done maybe. Prop aerodynamics is finicky because they move fast. The cool thing about carving your own, you can make a cool scale display prop for the pits.
 

billj

Member
Joined
Jun 1, 2016
Messages
16
Location
Virginia
My direction now is to build a prop using styro or home builders foam sheet insulation...get everything
Where it needs on the sample.
Cover and glass sample..
Duplicate sample in wood..

I've watched lots of you tube. The marking and precisely shaping of the airfoil is still a little illusive .

I think the foam plan will work..unlike wood..you can add back.
 

Appowner

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Mar 30, 2021
Messages
129
Location
Michigan
I did look - 49” diameter is the small end of ultralight props, although powered parachutes do go a little smaller. I was not trying to discourage you, just putting out the caution that, as terrific as this bunch is, it might not be the help you need…
As a modeler I just want to say the bunch here are far and away smarter and nicer than most you find on the dedicated model forums. Good crew here!
 

Appowner

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Joined
Mar 30, 2021
Messages
129
Location
Michigan
Just a thought but have you considered building the dummy prop like a wing? Ribs etc to get the profile right? Fill with foam and shape then glass? And since you have a duplicator you really only need one blade and dup it for both of the real ones. Or am I talking through my hat? :)
 

flitzerpilot

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Joined
Apr 19, 2017
Messages
428
Location
Hirwaun, Aberdare, S.Wales, UK.
Thanks for the hat-tipping, VB.

Even though the standard Z-21 spans only 18', it somehow looks bigger! The prototype is also red, :0) like that super Fokker DR.1 at 65% scale on here.

Of course the Goblins at 16'10" span and about 13' long are the smallest practical Flitzers imv. Here's a picture combining both!
 

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billj

Member
Joined
Jun 1, 2016
Messages
16
Location
Virginia
Just a thought but have you considered building the dummy prop like a wing? Ribs etc to get the profile right? Fill with foam and shape then glass? And since you have a duplicator you really only need one blade and dup it for both of the real ones. Or am I talking through my hat? :)
Exactly the direction I'm going..I can mess alot with foam..plus you have the benefit of filling mistakes.. I'm going to experiment there with the
"new" design . Alot faster too.
 

Tiger Tim

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Apr 26, 2013
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Thunder Bay
How much is left of your broken prop? If you can piece together one whole blade I’d be tempted to do that, then cut the blade off the hub and reattach at the coarser pitch you’re looking for*. Smooth out the join then use it as a pattern in your duplicator. Test fly that and if you like the performance you can carve a more elegant master to the new pitch.

*before someone drops in with an, “Um, actually,” I’m aware that this method won’t produce a perfectly helical pitch distribution. We may not even want perfectly helical for peak efficiency anyways.
 

billj

Member
Joined
Jun 1, 2016
Messages
16
Location
Virginia
I have a 100% blade to duplicate...but test running before the mishap indicates it will probably fly but will be a little " light"
So copying the original is first work.Bolt to the duplicator and learn.
Second blade will be a totally different
Education...lol
 
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