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Old Mar 07, 2002, 06:19 PM
Sticky Shepherd
Graham Stabler's Avatar
Oxford/England
Joined May 2001
4,017 Posts
homebrew cf prop

This is my first attempt at a carbon prop, it's not perfect but not too bad either.

The mould consists of a u80 prop stuck to a plate of ali. The underside of the prop was then filled with epoxy putty which was then cut to form a bevel around the edges of the prop. The prop was also extended with putty to 95mm making it a U95 or something. Ignore the holes around the prop these shouldn't be there and are a relic from a previous mould attempt. I covered them in tape.

The top of the mould was produced by pressing epoxy putty over the male half which had been pretreated with pva release agent. This is a mix of pva glue alcohol and ink. I got mine ready mixed. Could probably use wax, I don't know. Once hard I coated the mould in pva release and trapped two layers of thin CF cloth between the mould halves. These had been brushed with laminating epoxy using a sponge brush. The panels of CF were cut out by making a frame of tape preventing fraying and destortion. I clamped it up and stuck it atop of a radiator to cure for 24hours. After which I spilt the mould and trimmed with scissors. The surface finish wasn't too hot due to the poor surface finish of the mould but it cleaned up ok. I added the hub of a u80 to the centre of the prop to make my life simple. I only hope it works ok.

Not a how-to as the results weren't that good, at least compared to the Aeronutz resident expert Gordon "prop" Brown. But I thought it might inspire others a bit. I only did it as a bit of fun not expecting it to work at all.

Graham

Here's the two mould parts:
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Old Mar 07, 2002, 06:20 PM
Sticky Shepherd
Graham Stabler's Avatar
Oxford/England
Joined May 2001
4,017 Posts
mould together:
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Last edited by Graham Stabler; Mar 08, 2002 at 04:36 AM.
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Old Mar 07, 2002, 06:21 PM
Sticky Shepherd
Graham Stabler's Avatar
Oxford/England
Joined May 2001
4,017 Posts
The prop and a stock u80:
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Old Mar 07, 2002, 07:32 PM
Registered User
Houston Texas
Joined Mar 2001
743 Posts
Graham,

I would have to say not bad for a first try, I would watch out with props looking that good you might get a few requests. Hopefully this might inspire GWS to produce ones for the not so talented folks, IE "ME"

Philip
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Old Mar 07, 2002, 08:10 PM
Old Desert Rat
Arizona Chuck's Avatar
Rimrock AZ. USA
Joined Mar 2000
1,113 Posts
That looks good, got to try it. If we could come up with a way to build the mold split in the middle so you could make it a any pitch. Might have to do it in 3 sections, 6 parts so you can get it apart, so you can rotate around the hub.
Think I'll try makeing the mold out of "Rock Hard"
Anyone can buy things, ain't it fun to make it yourself? Even if you spend twice as much and spend hours on it.
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Old Mar 08, 2002, 04:48 AM
Sticky Shepherd
Graham Stabler's Avatar
Oxford/England
Joined May 2001
4,017 Posts
Another prop building method I'm going to try is to form some carbon around a cardboard tube and then cut blade shapes out of it at an angle to the axis and mount them in a hub. This is the same way people make yogurt pop props. If you make a jig for hub cutting then you can have any pitch you like.

I would be as happy if K&P got inspired. The increase in performance we have seen from these sorts of props shows that the kp props don't really seem to cut the mustard. The carbon props we have tried so far haven't been designed as such only given the t.l.a.r. treatment. There could be even more performance just waiting out there. Gordon suggested we modified the motor (kp00) to draw more current when geared for vertical performance. Only time will tell.


Graham
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Old Mar 08, 2002, 02:39 PM
Registered User
Leicester England
Joined Jun 2001
591 Posts
Graham's SE5 with Gordon's CF Prop

Looks nice eh?http://www.aeronutz.flyer.co.uk/grahamSE5hand.jpg

You can see it will fly good just from this picy!
It does.

Mark

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Old Mar 10, 2002, 02:29 AM
Registered User
Thessaloniki, Greece
Joined Mar 2001
105 Posts
have a look at this site for a simple method of laying carbon propellers over comercial

http://bund.unisport.etc.tu-bs.de/~m...ints/howto.htm
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Old Mar 25, 2002, 06:42 AM
Sticky Shepherd
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Oxford/England
Joined May 2001
4,017 Posts
Just thought I'd dig this thread up from the deepest depths to mention that I got to test the prop on saturday. I had one of Gordons great carbon fibre jobs on the front but it was a little battered and my se5 struggled to complete two circuits so I tried my prop and the model was transformed back to its old self. Power to spare. The CofG was a little rearward as I rebuilt the nose pusing the motor further back into the fusy, this gave slightly scarey flights including an acccidental "almost stall turn". All this on two cells with 2 cells and a 200ohm actuator. I'm going to add a low impedance actuator (100ohm) to the elevator and a mosfet to give powerful up contol and attempt a loop

Graham
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Old Mar 25, 2002, 06:57 AM
in persuit of low wing loading
Gordon Johnson's Avatar
Boston, Mass
Joined May 2001
6,432 Posts
Graham,
Funny, I was planning to find this thread as I may be trying to make CF props myself. I'm going to look at the composites store's site for supplies. Can you give me a quick list of what I would need to have on hand for my first trip into CF molding? I'm guessing I need CF cloth, some sort of resin, molding putty, and past that I'm at a loss. Also, what did you do for a hub? Did you just mold it slightly thicker and make it a push on, or did you glue something on the backside like WES does? Thanks in advance.
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Old Mar 25, 2002, 07:33 AM
Sticky Shepherd
Graham Stabler's Avatar
Oxford/England
Joined May 2001
4,017 Posts
To make my mould I used:

A bit of aluminium sheet.
A u80 prop
Some 5 min epoxy (to tack prop to ali plate)
Some metal filled epoxy (body filler probably better cheaper)
Pva release agent (very good stuff)

To make a prop I used:

2 pieces of ~90g carbon cloth
laminating epoxy used to skin wings etc (very thin)
pva release agent
a U80 prop
some cheap foam brushes

I cut the blades of the U80 at an angle to produce a hub which was glued into the back of the carbon version. The blades were cut off at an angle to distribute the stress otherwise it would just snap at the edge in a crash. A perfect push fit, funny that.

You don't need much!

Graham
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Old Mar 25, 2002, 08:41 AM
in persuit of low wing loading
Gordon Johnson's Avatar
Boston, Mass
Joined May 2001
6,432 Posts
Graham,

Thanks, I'll start acquiring the materials.
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