Mixing epoxy resin into a putty

[elite51203]

I'm about to "glue in" my transom core and I have a few questions about mixing up a batch of thickened resin. I'm using the 3:1 ratio of the thin epoxy system from US composites. I also have plenty of cabosil to thicken the resin.

My questions are:

Can I mix a big batch of resin thickened with cabosil?  Enough to trowel on the entire transom skin with a 1/4" trowel

Will mixing that much cause it kick off rapidly?

Can I use a paddle paint stirrer on a drill to mix it? Or will that much stirring and mixing cause it to kick off quicker?

Should I order and use the slow hardener for this?

[Callyb]

Yes you can mix it in big batches, well (and not to sound like a jerk) some people can. Temperature is the big variable that you have to contend with, if it is hot when you are mixing it, you will have a shorter kick time. One way to avoid this is put you resin in the refrigerator or ice it down. The other big thing is; once you get it mixed get it out of the pot as soon as possible and spread it thin. This way the resin won't build heat as fast.

As a testament to the big batch thing, I just put glass on the inside of my boat. The temp in the garage was 60 degrees and I was doing 100 ounce batches by myself.

It is all about the temps!

EDIT: I do not mean spreading the resin as thin as possible on the layup itself... You obviously want as much as needed to get a good bond.

[dirtwheelsfl]

Yeah what Carl said^^.      

I would definitely get the slow hardener.     Paint mixer will work fine too.  

The "thin" resin will take longer to get thick versus a thicker gluing resin but youll be fine...   I guesstimate about a half gallon batch to do it...

[RickK]

Ditto what they said ^^
Make sure you mix the resin and hardener and then add the cabosil.

[fishinonthebrain]

Ditto what they said. I use a hand held electric mixer I stole from the kitchen to whip up the epoxy then mix cabosil until desired effect is reached. The mixer helps to speed up the process in hotter weather or just saves time.

[melba toast]

We use a mixing bit that is attached to an electric drill to mix faster when doing big batches.

[elite51203]

I've got the slow hardener ordered from US Composites.  I plan on using a paint mixing bit with an electric drill, and mixing about 80-100 ounces at a time.  I just want to make sure that it doesn't start to kick off too soon!

[RickK]

I bought the little red paint mixer from HD and put in my drill - made the putty so nice and fluffy     (Made the process so easy too)

[dbiscayne]

I wasted a whole transom worth of thickened resin cause it kicked off before I was ready to clamp the wood on.  Once it gets hot it seems to lose some of it's 'stickiness', I could still work it but didn't trust the bond I'd end up with and would have always worried about trapping big air pockets so I scraped it all off before it was too late.

Second round, after mixing I immediately split the gallon resin batch into 4 smaller containers, then thickened each.  Worked as fast as I could with a helper, got it all together in time.

[Georgie]

Just another consideration, but if pot life allows, I've always coated the two mating surfaces with un-thickened resin first, then added the thickener to the pot for the rest of the mix to be used as a space filler.  I feel the thinner resin on the two mating surfaces penetrates smaller voids and pores better than the thickened epoxy and therefore results in a stronger overall bond so long as they are both done in the same layup.  It also seems to help "lubricate" the thickened resin so that it squeezes or flows a little better.  I have no way to actually verify if this is true, but it's just something I've always done on the basis of what seems to be a relatively logical assumption.  

[elite51203]

Once epoxy resin has cured, does it need to be sanded or scuffed up in order for another layer of glass and resin to be bonded to it?

[elite51203]

Just another consideration, but if pot life allows, I've always coated the two mating surfaces with un-thickened resin first, then added the thickener to the pot for the rest of the mix to be used as a space filler.  I feel the thinner resin on the two mating surfaces penetrates smaller voids and pores better than the thickened epoxy and therefore results in a stronger overall bond so long as they are both done in the same layup.  It also seems to help "lubricate" the thickened resin so that it squeezes or flows a little better.  I have no way to actually verify if this is true, but it's just something I've always done on the basis of what seems to be a relatively logical assumption.  

I think that's a great idea. Makes sense to me.

[Georgie]

does it need to be sanded or scuffed up in order for another layer of glass and resin to be bonded to it?

Regardless of actual "need" I would NEVER pass up the opportunity to improve the secondary bond between two laminations by giving it a once over with some 80-grit.  Gotta do it!

[dirtwheelsfl]

does it need to be sanded or scuffed up in order for another layer of glass and resin to be bonded to it?

Regardless of actual "need" I would NEVER pass up the opportunity to improve the secondary bond between two laminations by giving it a once over with some 80-grit.  Gotta do it!

Yes I always give it a "liability sanding" to knock down any sharp spots ,burrs etc. Just enough to take the gloss off. Be wary of "amine blush" too...

[Shine]

Just another consideration, but if pot life allows, I've always coated the two mating surfaces with un-thickened resin first, then added the thickener to the pot for the rest of the mix to be used as a space filler.  I feel the thinner resin on the two mating surfaces penetrates smaller voids and pores better than the thickened epoxy and therefore results in a stronger overall bond so long as they are both done in the same layup.  It also seems to help "lubricate" the thickened resin so that it squeezes or flows a little better.  I have no way to actually verify if this is true, but it's just something I've always done on the basis of what seems to be a relatively logical assumption.   <!-- s:scratch: --><!-- s:scratch: -->

Yes! you need to coat the two surfaces with un-thickened "neat" epoxy.  Especially important with wood core, but also a good idea for foam