Another mix ratio question

See our FAQ and tutorials before posting.
User avatar
jacquesmm
Site Admin
Site Admin
Posts: 25457
Joined: Wed Aug 14, 2002 1:00 am
Location: Florida USA
Contact:

Re: Another mix ratio question

Post by jacquesmm » Sat Sep 02, 2017 6:40 pm

Glues and putties overlap. The ideal glue should not only bond well but flex and moves the same way than the glued materials.
For example, gluing foam with a very brittle and hard mix of epoxy and silica will cause problems, the foam will fail in shear.
The epoxy will take care of the bonding but the filler should match the glued materials.
To glue plywood, epoxy and woodflour is perfect.
To glue foam panels, I would use Gelmagic which is a great general purpose glue but epoxy resin mixed with ground foam powder will work but I did not know such a powder existed.
I built many foam sandwich boats and always filled the seams with resin and microballoons.
Cotton fiber may work.
Glass fiber is too stiff IMHO.

This question should go to the designer or the foam supplier.
In my foam sandwich designs, there is no need for glue but the putty is made with micro-balloons with, when needed, a little bit of silica in the mix to keep it from sagging. Gelmagic is fine too.


Jacques Mertens - Designer
http://bateau.com

User avatar
jacquesmm
Site Admin
Site Admin
Posts: 25457
Joined: Wed Aug 14, 2002 1:00 am
Location: Florida USA
Contact:

Re: Another mix ratio question

Post by jacquesmm » Sat Sep 02, 2017 7:10 pm

There is something wrong with this thread, maybe it's a question of terminology but you don't "glue" foam panels in composite construction. You may have to fill gaps with putty but not glue.
If this is about gaps, the goal is to have a putty that has mechanical properties as close as possible to the core. If this is CoreCell (I suspect, don't know), ask Corecell. Mr Johanssen is highly qualified but he may be retired by now.
Or use phenolic microballoons.

About terminology, don't get caught by commercial names.
Sil is silica is SiO2 is sand basically, also named colloidal silica because it is so fine that it stays in suspension in resins. It is sold under many different names (Cab-O-Sil) but it is silica. Can be as hard as concrete when cured but does not sag.
Then there are microballoons, glass bubbles, microspheres, glass or phenolic. Very light easy to sand, not strong at all but OK for fairing.
There are also some PVC or other polymer derived powders. The WEST 401 is one of them and System Three uses them in their QuickFair. Easy to sand, easy to smooth but gets soft at high temperatures, not a glue.

The big family of fillers used for glue and sometimes fairing are fibrous stuff: woodflour, milled glass fiber, cotton etc. Quite strong, not great for fairing.

Also consider the resin. Some are flexible, other brittle. If you glue something flexible with a stiff 5:1 epoxy, something is going to give IF the glue line share the load on the part but again, that should not happen in a well designed composite structure. The loads should go to the skin, not the core.

I feel we go all over the place because the question is not clear.
Jacques Mertens - Designer
http://bateau.com

Eric1
Very Active Poster
Very Active Poster
Posts: 1721
Joined: Tue Aug 19, 2014 3:17 pm
Location: Spartanburg,S.C.

Re: Another mix ratio question

Post by Eric1 » Sat Sep 02, 2017 8:53 pm

This is one reason I love this forum. I learn new things!! 8)

Jeff
Site Admin
Site Admin
Posts: 2517
Joined: Fri Apr 29, 2016 12:17 pm
Location: Vero Beach

Re: Another mix ratio question

Post by Jeff » Sun Sep 03, 2017 9:43 am

Good explanation Jacques!!! Continuing to learn!! Jeff

fallguy1000
Very Active Poster
Very Active Poster
Posts: 621
Joined: Tue Jan 12, 2010 12:25 am

Re: Another mix ratio question

Post by fallguy1000 » Sun Sep 03, 2017 10:13 am

JM-I mean gap filler, but until you said it; had no idea they were different from glue; anytime we add epoxy; seems like glue to me. That stuff is sticky!

I will ask RW. He did not spec a gap filler. I hate to be such a bother to him about mix ratios.

My ground corecell is from rebate production, but would not be enough for gap filling. Except maybe the bow joins. However, all the corecell scrap could be made into lots of material. So, yes, corecell. Hard to believe I googled ground corecell and found nothing. Recycling..

Sil32 is glass balls. Just a bad brand name; not my fault!

I had someone tell me they filled gaps with cotton and microballoons and cabosil and that cabosil alone is too hard. He never gave ratios. That is all. Just asking the ratios.

Honestly, when I go online and look for what would be a hundred combinations of fillers or adhesives; the information is a little limited.
My boat build is here -------->

viewtopic.php?f=12&t=62495

User avatar
jacquesmm
Site Admin
Site Admin
Posts: 25457
Joined: Wed Aug 14, 2002 1:00 am
Location: Florida USA
Contact:

Re: Another mix ratio question

Post by jacquesmm » Sun Sep 03, 2017 12:47 pm

Years ago, the maker of Corecell produced a putty for foam. The function of the putty was to improve the bond between the foam and a polyester skin.I think it was a polyester polyester but check with them. There is no need for such bonding putty but it can be used to fill small gaps.
The name was Corebond.

Besides that, to fill narrow gaps, almost anything will do.
Eazyfillet should work.
If you want to use your foam powder, think in terms of consistency not ratios. Peanut butter consistency is about 1 volume resin for 3 volumes filler, very approximate.
Jacques Mertens - Designer
http://bateau.com

fallguy1000
Very Active Poster
Very Active Poster
Posts: 621
Joined: Tue Jan 12, 2010 12:25 am

Re: Another mix ratio question

Post by fallguy1000 » Mon Sep 04, 2017 2:58 pm

I think I will do some tests. I have some time this week for other testing, so I will probably do some tests of fillers.

Thanks for the 1:3 number Jacques. Very helpful.

I'll test
Cab;sil32;cotton;ground corecell
In various combinations with the epoxy.

Not sure how, but thinking maybe I'll make some sticks.

Richard said to stay away from cotton n cabosil just now, so I'll test full bubbles.
My boat build is here -------->

viewtopic.php?f=12&t=62495

Jeff
Site Admin
Site Admin
Posts: 2517
Joined: Fri Apr 29, 2016 12:17 pm
Location: Vero Beach

Re: Another mix ratio question

Post by Jeff » Mon Sep 04, 2017 6:05 pm

Fallguy1000, we will get back to you tomorrow as soon as we talk with our suppliers!!! Jeff

Post Reply

Who is online

Users browsing this forum: No registered users and 1 guest