cabosil ratio epoxy/poly

[aquaprouts]

recently recored my coffin cover using 1/2 inch ply and poly thickened with cabosil as described in many posts here....however, as i was mixing the cabosil into the poly it only seemed to very marginally thicken the mix....i used a quart of resin to a half quart of cabosil...seemed like it just kept taking more and more witbout thickening and i got pressed for time and used the mix.....job turned out ok..... what are the approx ratios to get epoxy and poly to stand up for use as a good filler and bonding spread?...now ready to bond a 4x3 ply recore to the bottom skin and affix the salvaged nonskid on top......definately need to get this mix right this time as the lower skin and nonskid is not smooth.....leaning towards epoxy as more working time and no mat needed....any and all advice welcome....thnx!

[wingtime]

You can use milled fibers to thicken the resin.  It is considerably stronger than cabosil too.

[slvrlng]

With epoxy it is amazing how much cabosil it takes to thicken it. I try to get it to a true cold peanut butter consistency. The milled fibers will help with strength. I try to add them in first and then thicken. Even at this consistency it is amazing how much flow you can still get. I have resorted to using metal mixing sticks as I was breaking the wooden ones.

[Callyb]

What they said. I think you are looking for an actual recipe for mixing the the two, but I would say that if somebody gives you one it probably isn't a hard, fast rule. I usually add anywhere from 1 to 2 1/2 times the resin volume, it just depends on the consistency you are going for and the temperature of the resin, type of resin, etc...

[aquaprouts]

Got it!...seems i used way to little cabosil at a 1( cabosil) to 2 ratio...i will start the epoxy  mix at 2 to 1(resin) and go from there....any tricks in getting the cabosil to absorb rather than float on the top of the resin and blowing away while mixing? stuff is incredibly light?...should i use glass chop with cabosil to thicken quicker.....just stirring by hand the first go around...thnx!

[4shore]

I had the same trouble as you so I took my time and measured it out and I found to get vinylester to "peanut butter consistency" using Fumed Silica(aero cell brand) it took about 3 to 1 (silica to resin)

I haven't done much experimenting with milled fibers in it but will try this with the final fillets on my transom replacement.

I have found it to help to use a CORDED drill with a paddle mixer for paint to mix it quicker. Take a plastic cover the same size as your pot and make a X shape cut in it, stick the mixer shaft thru it and into your drill. This will keep the silica from flying out of the pot when you mix it.

[Georgie]

Prouts-

Like Cally was sayin' it just depends on what you're trying to do.  if you want a gravity resistant paste that doesn't drip when used on a vertical surface, then you're goint to use a ton of silica.  If you're using it as part of a laminate where it'll be contained within layers, then you don't need as much.  There's no specific "right" answer, only "right" mixtures for the specific job at hand....and like Wingtime said, use milled fibers instead of cabosil if you're doing a structural repair.  The cabosil is really only a "thickener" and has more function in gelcoat repairs than structural resin projects.

[4shore]

Have you attempted to make your own milled fibers out of scrap csm or 1708? I though this may be a great way to utilize small scraps.

[aquaprouts]

thanks for your insight and experience.....I have not yet tried milxing milled fibers or making them myself....I am basically doing laminating/recoring work so maybe the milled fibers are a better bet....do you basically cut up mat into 1/4 to 1/2 inch length strands to accomplish making them?  Also, has anyone tried using poly gel on any projects where a stand up filler/bonder is needed....I can get a quart at a local auto supply store for $14.00....it would seem ideal to fill the voids doing laminating uneven surfaces{?}....perhaps could even add some milled fiber to further strengthen it.....is it overkill to use epoxy in the type of work I am doing? It seems that poly was used in everything at the aquasport factory so why does it seem almost substandard in many discussions....I would think the poly today is superior to the 1977 poly used to build my 196!  Thanks again for your help.....all the tearing out and prep and grunt work done and time to start rebuilding!

[4shore]

My 2 cents and i would imagine saltfly's also: poly is ok if you're doing wet on wet lamination. I decided to go with vinyl ester. It is substantially stronger than poly as far as secondary bond goes and its not that much more expensive, a few bucks a gallon. Epoxy is almost double the price.  Epoxy also will not dissolve the bonding agents on standard csm. It has an allergic effect on some folks also. This is pretty rare though.

As far as filler/bonder between uneven surfaces i used a thickened resin on one surface and then a 1 oz csm on the other and pressed them together until i had "juice" squeezing out. Left it for 24 hours and it held fine.

[Shine]

for fillets and most glue jobs, i use a mix of silica and wood flour.  2/1 by weight woodflour to silica.  It makes a very smooth putty when you mix it thick, and a super strong glue for bonding when you mix it loose.  I keep a small bucket of it mixed up.