Any advice for my hot coat shocker?

Hi there,

I have been finishing up work on my 2nd board a 6’3 shortboard thruster. I gave it a final sand and then thought I would give it a 2nd hot coat on the bottom and the rails just to get rid of a few small holes and imperfections. I rough sanded the area that I wanted to re-coat masked off the bottom and then hot coated the bottom, I waited a day then masked one of the rails hot coated that then another day masked the other rail and coated that.

I was busy for a few days and then I went out to sand these areas and finish the board off. I was dissapointed to find the bottom of the board very tacky. After being frustrated with trying to sand this. I picked up a broken board which I hadnt touched in 6 weeks. I had glued and glassed a side of (and had the resin kick way to quickly resulting in a mess). I tried sanding the excess off this board and it sanded exponentially better than the tacky hot coat.

I did not measure my mixes so this could be a contributor to the problem? I used a lam resin w/ some sanding wax and a hardner. I noticed the rails sanded as I would have expected them to but I am having a really hard time with the gumming that is occuring when trying to sand the bottom. One thing I remember was the day I did the coat on the bottom was extremely humid and wet. Could this have anything to do with the problem?

After researching the archives I think I am going to leave the board for another week or 2 and then try sand again. Also I read that could if you can get through the top layer it should be hard underneath. I am hoping this too could be the case.

Any thoughts on what may have lead to this problem would be appreciated. Also any suggestions for sanding?


Howzit darius, Take a big sanding block, wrap some 80 grit sand paper on it and just knock down the gummy bottom, after you do that it should sand just fine. The gummy stuff is just on the surface. You can always use more SA when mixing a hot coat batch but if you use to little or set the batch off to hot that’s when you end up with a gummy surface.Aloha,Kokua

…I dont know where you live

and in the last years I had with Kokua many chats about humidity, etc; he has a different experience in Hawaii

but I tell you that COLD + humidity is a bad mix plus old resin, bad chemicals proportions, technique, etc

cold + humidity kill gloss coats and 50% of hot coats

I live in Auckland, New Zealand.

the tacky hot coat was done in our ultra humid and wet tropical cyclones that we get occasionally in our summers. Ill get my sanding block out (maybe not in a hurry in the hope that it will harden).

Its definately a good way to learn these things by running into things like this, doing some research and then reflecting during a session of sanding which is way more difficult than it needs to me.

Thanks alot for the advice guys I really appreciate it.

I had a similar thing happen on the deck of my last build, what I did was wrap a layer of “cling film” (ceranwrap) really tightly over the area, pressing out as much air as i could, then left it a couple of days. I can’t claim that it cured it completely but it was way less gummy than before and sanded out ok. Worth a try?

Could be due to the cold/humid weather and or not enough wax? id sand it with some 36 grit on an 8 inch pad, if that is too hard and you’re going through too many sanding pads just filler over the top!

“I did not measure my mixes so this could be a contributor to the problem?”

Hi Darius -

A number of things can lead to the problem you describe. Using supplies within their shelf life period and maintaining strict proportioning is always a safe bet.

Calibrate - I borrow kitchen utensils to measure water which is poured in my recycled mixing buckets - place a few marks for a known quantity of resin. Make sure the containers are dry before using. Calibrated mixing buckets are available as are scales. Just have an idea on your quatities.

I know how much surfacing agent and catalyst to mix for various resin amounts but “wing it” according to temperature. Keep in mind that strict proportioning is variable and should account for things like temperature changes. Some guys have catalyst charts on the wall to account for various quantities and different temperature ranges but specific proportions may fluctuate from one brand to another. I’ve heard of resin that had a pre-mixed accelerator and needed far less catalyst than another brand so stick with one brand if you can.

Something as simple as over brushing can remove wax that has already surfaced and leave you with a gummy surface. Get the resin on the board ASAP and leave it alone.

So… use fresh resin, maintain proportions for the various temperature ranges in which you work and don’t overbrush.

For your immediate problem - you might just brush on another batch, make sure you’ve mixed the correct proportions and then break out the sander. It happens.