Hot Coat Sanding Help

I ran into some issues after I started sanding my hot coat. I posted previously regarding air bubbles along the rail after lam. I cut them out with razor and repatched and that worked out great. But a few other spots I had bubble, the patch popped out during sanding. I believe I was sanding too hard. I did not use enough catalyst so my hot coat turned out gummy so I was trying to get through the gum. See pictures below:

My thought would be to either patch with glass and resin and re-hot coat. Or to just fill holes with resin, then hot coat again. How should I go about this?

Also, I have some yellowish/brown spots after sanding. I think this could be gummed up hot coat from sanding too intense. ANy ideas on how to fix this? 

Always appreciate your help,



Sand those spots.  Feather them back.  anything that is exsposed foam will of course need a spot patch of 4 or 6 oz. cloth. The brown is from over sanding heat.  On thearea along the stringer I would fill with Cabosil and put cloth over it.  Do it all at once.  Cabosil diluted in resin, squeeged into the crack/hole, cloth and resin right over the top of it.  Hotcoat and sand.

Too much sanding for sure. now patch as McDing explain and do a thick hotcoat then sand up to have a flat surface but stop if you touch fiber. The trick is to have a true surface finish shape so you can laminate it flat wich need less hot coat thickness to be sanded flat.

As lemat says;  Every surface needs to be flat or smooth to accept the next step.  No divots in the foam.  A tight lamination with no dry spots or bubbles and then a hotcoat that fills the weave.

You might consider using a cheater coat next time and less MEK .   Less MEK will give you more time to insure that everything is wet out.  A cheater coat acts as a second coat making sure that anything you can’t see or missed is wet out.  Sort of like a second coat of paint. Cheater Coat =  As soon as you have everything wet out, rails, nose and tail, you MEK about half as much resin as you started with and squeege that back over the whole lam.  

Thank you both for this feedback! I really appreciate your help here. 

So with the cheater coat, the initial coat does not have any harderner? Then you add MEK with half as much resin and re-coat everything. Is that correct? 

Ive been having a hard time with resin gelling too fast. Its pretty hot here in NC and then also 90% humidity, so slowly figuring out how much to add with temp and other factors. 

No you need hardener in each coat  otherwise resin will not kick. McDing cheater coat is a second layer of resin lay on fresh lam that start to kick. if you lam with as much resin in one shot, fiber will float but with cheater coat you can lam fiber tight on blank first then well saturated and cover fiber thanks too cheater coat. works really well  with epoxy too. I am not a poly guy so each time i use it i use minimal hardener according to temperature, resin always kick even with only a few drops.