How to mix and apply a hot coat?

[Evinrude Boater]

I have three strips of wood for stiffeners to encapsulate in the bottom of my hull before I install stringers on top. I read about applying a hot coat to end grain balsa to prevent excessive resin absorption. I think I need to do the same for this new wood since I want to fill all voids between the wood and hull with resin before glassing them over. How is a hot coat prepared and applied?

 

[Terry H]

Re: How to mix and apply a hot coat?

I'm not sure what a "hot coat" is but when I have everything ready to laminate, I will apply a thinned coat of resin over new wood. That will soak in and givc a good deep bond. I use poly resin and a spray gun or brush, don't know what the epoxy guys do. I use acetone to thin with...and I thin the resin to water viscosity...30-50%. Catalyze as per the total volume. I will then use thickened resin to do whatever patches and fillets are needed, then start the layup...If at all possible I will finish the layup all at once therefore giving a good primary bond. If you glass over anythin that has set up you must grind it down to get a good bond. I know this is too much info, but I see too many folks doing one layer, let set than the next...there is no chemical bond that way, just a glue bond or what is called a secondary bond...just too many thoughts

 

[Evinrude Boater]

Re: How to mix and apply a hot coat?

Thanks Chief, I get the picture. I think a hot coat is mixed with more catalyst to make it set faster. The thinned coat is what I was wanting to know about.<br />Can you lay another layer of glass over a tacky layer without any sanding/grinding?

 

[Terry H]

Re: How to mix and apply a hot coat?

That's the idea, do all your layup at one time. No grinding. I don't think I would mix more catalyst than recommended, but maybe someone else knows better. Always catalyze by volume, if you thin or thicken the resin, go by the total volume. Sometimes if I have a large layup I will catalyze a little on the lean side to give me time, then make the last mix a little on the hot side. Always squeegie out the excess resin and airvoids. Too much resin=brittleness. just another thought

 

[BillP]

Re: How to mix and apply a hot coat?

Hot coats are done ONLY with polyester (laminating or finishing)resin and normally for two reasons. <br /><br />One is to fill the fabric weave and leave a thick coating for sanding. <br /><br />The other is used to seal foam or core material and prevent it absorbing resin out of the glass job before it hardens. If the core "sucks" resin into itself the glass job is dry and has "pin" hole size bubbles...which make a brittle and weak glass job. <br /><br />In glassing surfboards, to do a SANDING surface over a previously glassed foam blank, we used 40cc of hardener in a pint of resin...this is so "hot" the drips get hard before they hit the floor. <br /><br />For GLASSING the surfboard (to prevent resin from soaking into the foam blank)we kicked it so the resin got hard in about 6 minutes...kicking exactly at the time you are working the LAST wrinkle or bubble out of the cloth.

 

[Evinrude Boater]

Re: How to mix and apply a hot coat?

Thanks everyone, I think I should buy the book instead of y'all writing it for me.

 

[Terry H]

Re: How to mix and apply a hot coat?

Ther's enough info here on this forum to write the book...an, everybody is happy to help...just a thought