Another mix ratio question

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fallguy1000
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Another mix ratio question

Post by fallguy1000 » Thu Aug 31, 2017 5:11 pm

I was told to use cotton fiber and sil32(balloons) and cabosil and epoxy for a panel joining goo.

Has anyone ever tried this combo?

I'd like a starter recipe. Volume, if possible.


My boat build is here -------->

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terrulian
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Re: Another mix ratio question

Post by terrulian » Thu Aug 31, 2017 7:23 pm

I have no idea...sorry.
But Jacques says to use wood flour and epoxy, I believe. What would be the advantage of doing something other than what the designer recommends?
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narfi
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Re: Another mix ratio question

Post by narfi » Thu Aug 31, 2017 7:31 pm

He is joining foam panels on a boat from another designer.

terrulian
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Re: Another mix ratio question

Post by terrulian » Thu Aug 31, 2017 7:35 pm

OK, didn't know that. :roll: Thanks.
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narfi
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Re: Another mix ratio question

Post by narfi » Thu Aug 31, 2017 7:39 pm

terrulian wrote:
Thu Aug 31, 2017 7:35 pm
OK, didn't know that. :roll: Thanks.
Its interesting to me, he is building and experimenting with methods for something so large, his table is impressive.
viewtopic.php?f=12&t=62495

I dream that some day Ill make something that big :P

fallguy1000
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Re: Another mix ratio question

Post by fallguy1000 » Fri Sep 01, 2017 12:37 am

amtcomposites suggests (sil32 replaces balloons, btw)

cotton:cabosil:sil32:epoxy by volume at

1:1:1:1 for a light duty adhesive, light weight for relative strength, density I get when I calculate is 0.8625 g/ml (lighter than water)

or

cotton:cabosil:epoxy by volume at

1:1:1 for a bonding adhesive certified for aircraft, but the density is 1.09 g/ml (heavier than water)

the heavier mixture, I expect would be a B to sand

I think I like the first one for a general purpose adhesive. I might do some testing of both. My most critical joint would be where the bottom of the hull intersects the sides. This would be where the greatest impacts to the hull would occur if the hull comes off a wave and down. If the aircraft bond is significantly better in testing, I might use it for those places it seams(ha!) best. Otherwise the lighter bond might be the way to go for fillets.

I also think I'll try a mixture with ground corecell in it as well. It'd be bulkier, but lighter than water as well. Maybe something like
cotton:cabosil:sil32:ground corecell:epoxy
1:1:1:0.5:1

thanks for any replies

I did test one of my early all cabosil joins today and it was terribly brittle I thought.
My boat build is here -------->

viewtopic.php?f=12&t=62495

Eric1
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Re: Another mix ratio question

Post by Eric1 » Fri Sep 01, 2017 4:40 am

I hope Jacques will weigh in on this. I've never worked with the foam you're using but it's my understanding that colloidal silica produces a very strong adhesive for this type of bonding. My knowledge is limited to the work I've done with it. I have bonded g10 rocket fins to g10 tubing and could stand on the finished rocket without breaking the fins off.

fallguy1000
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Re: Another mix ratio question

Post by fallguy1000 » Fri Sep 01, 2017 4:08 pm

But sanding will be required. The goo goes on inside and oozes outside. The outside joins are done after sanding the rebates, so sanding is a for sure, not if.

I broke the small join I made with colloidal; it was brittle, but the glue didn't fail; just like with wood; the core next to the colloidal/epoxy broke under lots of torque (sic). I think my friends concern was with the joins printing through the 2 18 oz biax tapes.
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TomW1
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Re: Another mix ratio question

Post by TomW1 » Sat Sep 02, 2017 4:40 pm

I am not sure what you are asking exactly but any time you start adding cotton or fiberglass fibers to the mix your sanding becomes extremely harder. My first question is what does Richard specify for those joints and go with that. Second you will be covering the joints with fiberglass and that is what will provide your strength. I would say that outside and inside you will have 8 or more layers of fiberglass. These parts will be the strongest parts of your boat and are like an I beam for the hull.

I am enjoying watching your build. Just be careful and not starve the fiberglass of resin.

Tom
Restored Mirror Dinghy, Bought OD18 built by CL, Westlawn School of Yacht Design courses.

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Re: Another mix ratio question

Post by Jeff » Sat Sep 02, 2017 4:45 pm

fallguy1000, when you have time, check your email. I asked Jamie to send you a summary of what we have accomplished and what information we are waiting for regarding your request. Also we sent you a spec sheet on a product that was recommended for your purpose by a supplier of ours!! Have a good weekend, Jeff

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