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Old 04-03-2005, 07:46 PM
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levansic levansic is offline
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Default Home-made prop thoughts

I've been giving a lot of thought towards building a prop lately. Most of the home-made prop's I've seen are of the exact same design with a laminated wood core and fiberglass wrapping on the outside.

Cutting the wood core takes a lot of hand work. When looking at a three-blade design, minor variations between the blades could contribute to balance and vibration problems down the road.

Being a CNC guy, I would try to reduce the amount of carving time required by cutting the blades in a CNC mill. Unfortunately, I can't cut wood in my CNC machines because of the contamination that the wood chips would cause.

I've seen that Hartzell has been using foam cores in it's composite constant speed prop blades, and wondered if the same could be done for a fixed-pitched composite prop. I have no problems cutting foam on the CNC, as it doesn't contain wood resins, nor does it decompose.

The other home-made props I've seen rely on the wood for a good portion of the strength of the prop blade. My engineering background tells me that I could compensate for the loss of the wood strength by using stronger composites and possibly a shear web through the blade, similar to the EZ wing construction.

I'm just thinking out loud here, and any prop that I build myself would be extensively tested before coming close to being mounted on a plane. I'm just looking at this from the perspective of differing construction methods to improve and speed up results.

Any thoughts?

-- Len
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Old 04-03-2005, 08:52 PM
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why not call an aircraft salvage yard and get a prop strike blade to examine? good starting point
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Old 04-03-2005, 11:44 PM
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Quote:
Originally Posted by Dust
why not call an aircraft salvage yard and get a prop strike blade to examine? good starting point
You mean a Hartzell composite prop strike, or a wooden composite strike, or both?

I didn't think about strike resistance. Hmmmm.

I don't plan on striking my prop, but you never know. Then again, most of Hartzell's GA props are aluminum, which would bend rather than shatter.

I would bet that if a composite prop was made strong enough, then it would survive a prop strike with just a portion abraded off the end, like a wood prop. A hard strike would destroy either.

OK, with a foam core, even an abrasion type of strike would immediately ground the plane and require replacement of the prop. If you could easily produce the cores, then this would be a much less costly replacement.

-- Len
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Old 04-04-2005, 12:48 AM
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I mean - get one that has exactly or as close as that as you can find that you would like to build yourself to examine - why not, once it is strikes the ground, not mere brushing, it is trash and should be able to be had for about the price of shipping
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  #5  
Old 04-04-2005, 01:07 AM
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the prop you describe has been done,Burt alive i think or he has the link(i posted it last year.
i started a wood core but put it on holed when i found the link to the composite one,and yes it has strands of glass from tip to hub and back.
and if you hit moc 1 you'll need carbon tips, so they say
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Old 04-04-2005, 09:33 AM
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If you mean Bulent Alieve, he's just down the road in Ft. Lauderdale. His prop has a wood core.
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Old 04-04-2005, 10:16 AM
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You could try this link to Nick's Prop Page on the EZ-Noselift site.

Read a rather scornful comment in an old CP where Burt noted one home designed & built prop failed at something like 0.1HRS flight time, looks like fun though.
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Old 04-07-2005, 01:58 PM
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Thanks Spodman!

So I'm not the only nut who thinks this is possible for the homebuilder. I don't have a plane yet, so I don't have room to criticize his methods, but I was a bit worried with the haphazard method of obtaining airfoil shapes that he is using. From most of what I read, there is a lot of science to picking the right airfoil section across the prop blade. Helix angle is important, but also the Mcrit of the airfoil employed, especially towards the end.

I intend to carve the foils first, with troughs for reinforcement layups, rather than cutting the helix, and approximating the foils afterward.

-- Len
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  #9  
Old 04-07-2005, 02:47 PM
Rob Wright Rob Wright is offline
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http://www.russellw.com/manuals/aero...ce/default.htm

what would be cool is to build an Aeromatic Propeller.


mmm...
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