epoxy hot coat problem

i put the hotcoat on my 5’ 11" thruster and it turned out well and sanded down well… i waited overnight to sand it too, but there are 2 areas about the size of a quarter where the resin is still tacky and hasnt hardened. i used resin research epoxy and used a strict 2:1 ratio of epoxy to hardener. also added 2cc’s of additive f for every ounce of hardener, just like the resin research guide said. also, im pretty sure i mixed the resin in the cup very well. i did it when the temperature was in the sixties and humidity was very normal for southern california. anybody know what happened and what i should do?

… i cant figure it out

Brando

I’m a backyarder , I don’t work for Resin Research or in the surf industry. If it was my board I would treat the tacky areas as little repairs. Scoop out or wipe or sand the bad areas. Wear gloves.Get rid of all the gooy stuff. Then apply more “hotcoat”.

Why did it happen? Good question? I don’t really know why.

Temps in the sixties when glassing …not good…it can be done…75 would be much better.

Waited “overnight” to sand. I don’t postcure so I wait five days not five hours.

Mixing…I stir for 4-5 min…slow and steady.

It is odd that the whole board cured except a few small spots. I’m interested to hear what others have to say.

Ray

Most likely a mixing or measuring problem, even though the effort was there to be careful.

It happens, sometimes no matter how hard we try. I get brain-farts where I think i’ve done something correctly but really haven’t :slight_smile:

Most likely there was resin in the bottom of the cup, that didn’t get scraped up properly when mixing, then it drips out when you up-end the cup, and you get blotches of unmixed resin here and there. Thats my guess.

Gotta scrape the bottom and sides of the cup really thoroughly, and scrape off the mixing stick a few times. It’s a chore, but its gotta be done right, just one of those things.

Temperature shouldn’t be a problwm, the resin will just cure slowly.

Prepreg carbon gets frozen… no problems there.

Moisure is the main thing i’m scared about.

Theres so much moisture in the air here at the moment, I can’t get any wood to stick together!!! pissing me right off!

I’ve had the same problem with RR except it wasn’t on the board it was left in the cup,a few spots of uncured resin cconnected to a chunk that was perfectly cured.This happens when I put the resin in the cup first, it has lower viscosity than the hardener so it sticks down in the corners of the cup better.I’ve noticed that if the hardener goes in the cup first,I have no curing problems at all,75 degrees or better for epoxy work,I also want to get a scale for measuring the mix ratios,maybe find some cheap bowls with no corners to mix resin in as well.

Same here… hardener in the bucket first so the resin dosen’t stick to the sides or bottom. It also seems easier to measure accurately for me.

The other thing is… watch out for those drips along the lip of the bucket. Sometimes a drop of pure resin will stick to the lip of the bucket when you’re pouring, and it will stay there while you mix. It ends up coming out when you’re not paying attention, as you pour the mixture out, and it gets dragged out with the pour.

Jesus,

Interesting idea to put the hardener in first. I can definitely see how that might help the problem of less viscous resin sticking to the bottom of the cup.

My current method (after much trial and error and screaming and frustration) is to use the more expensive paint mixing cups. I wipe them with denatured alcohol just in case, put them on the scale and tare the scale. Then I pour in epoxy. Then Add F and mix. I got this tip from someone else to put the Add F in before the hardener. Then I put it back on the scale, tare, and pour in Hardener. Then I start to mix, then add in the correct amount of X-55. I think it really helps to use X-55 because it keeps the resin from running off the rails as much before it gels. Then I mix for at least the length of a song on the radio. If you can’t find a timer or don’t want to grab one with sticky hands, having a radio on helps. And you’re guaranteed at least 3 minutes of mixing that way. Then I pour it out on the board and brush out as usual.

After the resin cures I try to reuse the cups by cracking out all the cured epoxy. Usually after I do there’s still some gooey spots in the bottom of the cup. So even with all that prep and mixing, some of it is still stuck in the bottom of the cup.

I’ll have to try the hardener first next time. That won’t be for a while, so maybe someone with a more current project can try it out?

When you mix epoxy you must use a scale. If you do you will not have issues. Also make sure you mix the epoxy complete. Cut off the end of a tongue compress so it’s flat that way you can mix all the bottom epoxy as uniform as the rest of the cup.

I had rookies gluing up stringers into EPS and XPS Blanks with epoxy and they came apart. They were mixing by volume. I bought a scale and all my troubles went away. I use RR epoxie. I use to use West Marine Systems 10 years ago and never had a problem with their pumps. I still use it for wood projects. RR works best when you weight it. Guessing is dangerous to your pocket book and quality of your finish product! The Gurus of Epoxy all use scales.

I’ve done this one … small areas that didn’t get mixed in the corners or bottom of the bucket. Just do a couple small repairs and you’ll be fine. Mixing with the hardener first is a good tip. If the resin is thick (because it’s cold) it’s not a bad idea to heat it a bit before mixing. Either set the resin in the sun for a bit, keep it indoors or a few seconds in the microwave before adding it to the hardener.

Thanks for all the help guys. i am going to try a different stirring method and add the hardener before i add the resin, that makes sense. ill let everybody know how it goes

“Then I mix for at least the length of a song on the radio”.

Just hope they aren’t playing the full length version of In-A-Gadda-Da-Vida.

Rule of thumb for failsafe epoxy mixing…

Flat paddle stirring stick, swill the mix around as you stir, scrape the corners, stir til you hand hurts then stir again.

I’ll be trying the harder-first bit too…

Josh

www.joshdowlingshape.com

If you want to really play it safe. After following all the tips from above, transfer your mixed epoxy/hardener into a new cup and mix again.

This will cure your problems.

CJ