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Possible to repair this prop?


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s1buell_wl, yes I saw that one yesterday. looks like it could do the job. They also have a movieclip on youtube how to repair fish poles:

Doesn't look to complicated.

Today I manage to get hold of a guy that repair carbon fiber on a professional basis. Unfortunately he doesn't have the time to fix mine but he gave me enough confidence to believe I can do it myself.

I was a bit uncertain about the products I found for repair, the epoxy and the carbon fiber but he says it's fine for minor damage so I bought a sheet of carbon fiber and epoxy resin.

Today I managed to remove loose pieces inside the propeller and I had to open it up slightly in the damage area to get them out

The idea I have it seal the hole somehow without adding to much material, then add epoxy on top of that. Grind that down to get a smooth surface and then apply carbon fiber sheet on top of that to have the strength back.

It wont look perfekt I'm sure but hopefully good enough. I probably need to do something similar on the other side if they weight different gets too big. I'll use clear coat to fix the remaining weight difference.

Opinions are welcome

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He didn't give me full instructions how he would do it, but I don't think it's hard to apply carbon fiber onto a flat surface. The tricky part is probably to get most of the resin out without making a mess out of everything.

I'm a beginner at this kind of work, so we'll see.

I was a bit eager to start, so I have begun already. cleaned the surface with alcohol. Applied some epoxy resin and added strings of carbon to build up the surface. I sure have some sanding to do when it has cured.

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As I said, I started and what I did was this:

I used a knife to open up the hole in the propeller, it was about 5x10 mm large. I shoke the propeller and manage to get all loose parts out of it.

I cleaned the propeller with alcohol and then sanded it and cleaned it again.

I mixed i little of resin into a disposable cup. Mixed it with a nail. about a tablespoon.

Then I started to apply it onto the broken surface to wet the fibers. I used the nail for this.

I cut a small piece of carbon cloth and broke it apart so it became pieces of hair. see the picture.

I used the fibers as a bridge to seal the hole in the propeller. Most of them are lengthwise so there isn't much strength in this. I used the nail (the head) and dipped it into the resin and wet the fiber. slowly building it up.

I also took some tiny fragments of fiber and mashed into cavities with the nail.

The consistency of the resin is like runny syryp to begin with and after 10-15 minutes it starts to get stickier. Carbon fiber behaves like soft brush.

The idea now it to let it harden, then sand it down again and apply some filler and then sand that down so the surface is smooth so it will be easier to apply the carbon fiber fabric.

Not so sure about this to be honest, I'll probably get a hole back when I start to sand, but well see.

So far it has been easy. I have no idea if it is the right way to do it though. But I'll think it'll work.

573364191cc8a_2012-06-2819.22.01(Medium)

573364192000f_2012-06-2819.19.54(Medium)

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Your almost there,,,

Best bet in the future if you have access to the fabric, is to chop it up with a pair os scissors and mix it into the resin until its like putty. :-)

Bin the idea of the fabric on the top, it will add nothing to the strength and make the finish harder to get nice. I am a bit of a geek when it comes to Carbon as I used to make the TVR 24 hour team and the Ducati BSB stuff for them :-)

SW :D

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Thanks for the advice Simon, it is good to have someone around that knows this stuff.

But I don't understand why it wouldn't add to the strength. I would like one or two pieces that are a few cm larger than the damage on each side. a piece of fabric about 10x7 cm or something. that I roll on top on it and on the sides.

Why wouldn't that help?

BTW how much is actually needed to get strength? how many layers?

What I'm using is about 200 g / m2

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Its more about the construction of the layers rather than the number...

But with 200g m2 plain weave (as per your pic) and polyester resin ( which I am guessing your using with a 15-20 min working life) you would need about 5-6 layers of 200gm before it was worth thinking about.

MAINLY because your sticking it on to the top, and its not interlaced and pressed with the other layers. You can try as hard as you like to get a proper bond, but it just wont happen 'structurally' if 'stuck' on the top.

The filling looks great, surface finish that and paint it black ( or mix some black pigment in with your resin when adding the final coat. :-)

SW :D

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No I'm using laminating epoxy

It may look good but I truly doubt it'll be strong enough yet, it is too thin.

I'm a bit worried about the crack that opened up along the blade, don't like that, so that's the reason I want to make the structure stronger.

Maybe I should open it up again and add a putty of carbon, as long as I'm not adding too much.

Still like the idea of adding the fabric on the surface, I'm too curious not to :)

If done professionally, what tools/products are used then to fix something like this?

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It would not happen :-(

It would get binned as Carbon is a mare to repair for the same reason as above.

The truth is though, your prop is only carbon on the very outside layer, most likely 1 x 200gm m2 then backed up with glass, or filled with polyurethane foam.

Make sure the leading edge is fully sealed, and then once cured try an ultra safe ground run ( go to the north pole and do it ) :-)

Good Luck, I am sure the chopped carbon and epoxy will work as long as you keyed it in. :-)

SW :D

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Well if the pros can't fix them properly then there isn't much point sending them to them either.

Yes there isn't much carbon in them, that's for sure. They break easily especially along the propeller. I wonder if they glue two pieces together.

I don't mind them breaking though, rather that than the motor. So I'll guess a few layers of carbon on the damage will do a good enough job to hold it together.

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Man what a mess I made out of this prop. Applied resin, let that dry for a while until it got sticky, applied a piece of carbon and made a mess out of that, removed that and tried again.

Think it'll be okay in the end after sanding and little more coating. But I do agree with you Simon, making a putty would have been much better. Applying woven carbon wasn't easy.

5733641923617_2012-07-0221.27.41(Medium)

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I should have said....

SORRY... IF you are going to put a layer on top, while its still 'green' wrap it in cling film nice and tight ;-) It's a tip for next time,(to stop the edges lifting during the shrinkage of the cure) but I still remain unconvinced about how long its going to stay there if honest.

Good luck though :-)

SW :D

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I have overworked this propeller, but I'm clear coating it now. Using 2 component clear coat.

The propeller better hold now! :) I'm not pleased with orange peel surface and just for the fun of it I might wet sand and then polish the surface to get it good. On the other hand my new glider has arrived so we'll see.

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Soon there :) I'm getting a bit sloppy in the end now, need to have it done so I can test it out and then test the new glider.

[youtubevideo]

[/youtubevideo]

balancing the prop now. I used a 22 mm copper pipe that I cut off and a bit of tape to get it to fit inside the hub of the propeller. The stand are made out of two inverted soup plates.

Works well. I wasn't sure if it would so I switch sides of the plate, still falling on the heavy side, turned the propeller upside down, removed the pipe and switch that 180 degrees and put it back and so on until I tested all ways and it works well as a balancer.

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A shitload of sanding, or at least plenty more than I would have needed if I fixed the problem correctly from the beginning but it's fine, I was curious to test.

Actually I lost track on the amount of epoxy layers I added but I had a slight problem with the carbon piece I added. It rose slightly in the edges (as simon said it would) So I needed to sand that and to get a smooth surface. But I'm guessing four layers.

And I kind of like to paint with the epoxy as well so I added more than I needed. In the end I had added enough to conclude I would need sand the blade down all the way.

Also I found a few marks in the other side from the time I lost the muffler so I painted that one too. Needed to add some weight anyway.

Sanded it with 240 grain between the epoxy. Then When I was happy I added two component clear coat with a brush. two layers on each side, no wait three on the "good side". But I wasn't sure how to get that in balance and had gotten to the point that the weather forcast looked good again plus the fact the speedster had arrived, so I sanded again with 240 and 400 and 800 (wet sanding) and sprayed it with 1 component clear coat. Not much point adding the two component I guess :)

anyway, may sound like a lot of work but it really isn't much of deal. It doesn't take much time to sand it.

Waiting for the epoxy and clear coat takes time.

Now I have a sweet amateurish look on the blades. Orangle peel clear coat. Wasn't adding enough between sprays.

Maybe I'll fix it but well.. we'll see :)

I'm waiting for the clear coat to harden now, Tomorrow it could be used for flying.

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