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RE: Composite design factors - 12/10/2007 3:30:21 AM   
dreadnaut



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quote:

ORIGINAL: Spike


quote:

ORIGINAL: SCALECRAFT

mad

For a gel coat/surface coat of the mold we use cabosil (fluffed silica) and a bit of black pigment to show voids easily in the layup of the parts. Should be like pudding that self levels, but can stick to the sides.

...

Steve


When I've tried to use Cabosil in the past, I've had a very hard time mixing it in. It seems to like to make little balls that resist mixing. Any tips?

- Spike


I've had this problem too, and it can be a serious headache. You just have to work it. I use small plastic dixie cups and use a popsicle stick to work it against the side to break up the lumps. I add the graphite powder after, otherwise you will not see them all. Mixing smaller batches makes it easier.

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RE: Composite design factors - 12/10/2007 4:12:56 AM   
SCALECRAFT


 

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Status: offline 		Lumpy cabisil. Yes, it can happen but it just takes a bit more mixing as mentioned before. I have noticed lumpy cabosil when I store it a long time. May be moisture clumping the filler together??

I use slow hardner. Its thinner and gives easier and more mix time. Also cold temperatures makes mixing harder, epoxy is less viscous.

Gotta try the graphite powder one day.

Steve

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RE: Composite design factors - 12/10/2007 4:26:55 AM   
seanreit



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From: Cedar Park, TX, USA
Status: offline 		After I glass a wing, for the second coat I mix some talc powder with resin, and some west sys graphite powder (black) and paint that on my wings. Easy to sand and fills the weave, and easy to see when you've gone through (color difference).

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RE: Composite design factors - 12/10/2007 3:00:38 PM   
SCALECRAFT


 

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From: MONTEBELLO, CA, USA
Status: offline 		On composite wings??? Or as a method of finishing the surface.

Steve

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RE: Composite design factors - 12/10/2007 5:27:46 PM   
daven



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From: Andover, MN, USA
Status: offline 		I had issues with the lumpy cabosil when I was using Pro-Set, but I don't have a problem with them using EZ Lam.

Not sure what the difference would be??

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RE: Composite design factors - 12/10/2007 5:51:06 PM   
seanreit



Posts: 6979
Joined: 4/17/2002
From: Cedar Park, TX, USA
Status: offline 		I use MAS epoxy and have never had the lumps. I might have had it once with West Systems, but can't remember for sure. I like MAS better than West systems, but it does not seem to last as long as west systems did. I think it's a thinner resin and thinner hardner.

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RE: Composite design factors - 12/10/2007 6:07:47 PM   
seanreit



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Status: offline 		This is for a built up wing that is sheeted and glassed whether it be foam, or classic ribs and spars then sheeted. This is the process I use prior to adding any primer.

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RE: Composite design factors - 12/10/2007 9:35:22 PM   
SCALECRAFT


 

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Status: offline 		Thanks.

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RE: Composite design factors - 12/10/2007 11:28:00 PM   
Randy Etken



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From: Shakopee, MN, USA
Status: offline 		If you want to stop getting lumps, make yourself a mixer out of threaded rod and star servo wheel. Works great, saves time and always a good mix.

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RE: Composite design factors - 12/10/2007 11:31:07 PM   
Randy Etken



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Status: offline 		Clean it in Laquer thinner or Acetone.

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RE: Composite design factors - 12/11/2007 12:20:25 AM   
dreadnaut



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quote:

ORIGINAL: Randy Etken

Clean it in Laquer thinner or Acetone.


I find that a better sovent for cleaning epoxy resin is denatured alcohol.

Use water as a solvent for PVA.

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RE: Composite design factors - 12/11/2007 3:19:44 AM   
SCALECRAFT


 

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Status: offline 		Randy

i like that idea.Thanks. In fact if you heat up the horns and make them paddle like i think if would work great. Also, you can mix in a yogurt cup with the shaft going through the plastic cap and containing the cabosil dust. The ones with the clear caps.

steve

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RE: Composite design factors - 12/11/2007 5:14:30 AM   
Randy Etken



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Status: offline 		Yes I do put a small twist in them.

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RE: Composite design factors - 12/11/2007 2:00:21 PM   
daven



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Status: offline 		Thanks for the tip Randy, I could have used that over the weekend.

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RE: Composite design factors - 12/12/2007 3:18:48 AM   
TeamSeacats



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Status: offline 		likewise...a great "duh" idea.

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