RR Hotcoat problem

General Discussion
1

I just hotcoated the longboard I’m shaping for myself with 10 oz of RR epoxy and 5 oz of the fast hardener, and for once it actually brushed on fairly easily without the weird white streaks I had been getting before. I pulled the tape after about an hour and a half, then left to go run some errands. When I got back it had cured completely and leveled out nicely, but on further inspection, I noticed a weird crack-like pattern on it. It looks like alligator skin. It doesn’t look like the cracks go all the way though the coat, more like they’re just on top, but they don’t wipe off.

Is it contamination? I wiped the board with denatured alcohol before hand and used a new 4" chip brush. Does it pose any problems for the board, or is just cosmetic? I’m a little hesitant to go on if the same thing’s going to happen to the other side.

2

first of all i know nothing about surfboards…

so that being said

it sounds like a mix problem

especially with fast hardner

I’ve had than happen before when different parts of the bucket kick off much slower than other parts because I didn’t spend the 4 minutes stirring it like I was supposed to. So you get those scales as the slower curing parts still try and level out against the already jellying parts. Sometimes a series of bad vibrations at the wrong time can do this. Happens alot with UV the way it kicks and you have to move it outside…

Again like i said i don’t anything about surfboards but it’s a guess…

3

Hmm, I think you could be right. I did spend around 3 minutes stirring like crazy, but even though there were a couple of little streaks left, I figured it would be fine. I’ve had batches where I stirred even less and didn’t have any problems, this is a first time.

Well if that’s all it is then I’ll just be more careful on the bottom and stir for longer. Are there any reduced bonding/chemical structure/whatever else complications?

Thanks

4

I managed to get a pretty good photo of the cracks this morning. They are all over the board. I’m hoping they won’t be an issue in sanding but we’ll see.

5

Rachel,

Are you using additive F? Also the board should be at room temperature. After you get the board covered I assume you are brushing lengthwise, then cross brushing and then finishing by brushing lengthwise. Get the resin on quickly, get it leveled out and then leave it. If you mess with it too long it will not come out smooth. Don’t have any air moving across the board from fans etc. I try to leave the room while it is leveling out and kicking. Hope some of this helps.

Dave_D

6

I can’t tell from the photo, but can you feel the cracks? Are you sure it’s not just streaks in the sanding coat? If it’s not cracks, it will sand right out. I’ve seen it in my epoxy sanding coats before, and it goes away when sanded. I can’t imagine it cracking, unless it was incredibly hot while curing (and I’m don’t know if that would cause it either).

7

Was it done in a completely still air enviro ?..no air current ?

8

Hi Rachel

An old friend in the aircraft compostite industry taught me this epoxy trick. Works well on our natural bamboo fabric laminations and hotcoats. I’m sure it’ll work with fiberglass too. No cracks or streaks, maybe an occasional “fisheye” from contamination. Might be something to try on your next board.

  • Pour the resin and hardener in the mixing bucket but DO NOT MIX.

-With the board on your glassing racks, sit the bucket on top so the resin and board are at the same “altitude”

-Let the resin sit (unmixed) for about 10-15 minutes to attain room temp - then mix thoroughly.

~Brian

Greenlight Surfboard Supply

www.greenlightsurfsupply.com

Surfing = Good for Your Soul

Shaping = Good for Your Surfing

Greenlight = Good for Your Environment

9

i’m with the above comment saying that it should sand out from what i’m seeing…

10

I didn’t use add F in this hotcoat because previously I’ve been having problems with white streaks when brushing it on that don’t disappear when it cures. The board was at room temperature throughout the entire glassing process, I work indoors and so it makes it easy to control the temp. There is an air vent directly above the board, but it has blocked for the most part. Otherwise there is very little air movement in the room. Once I brush it on and level it out, brushing lightly lengthwise, then crosswise then lengthwise again, I leave the room. I came back about an hour later to pull the tape.

And the only way I can really describe it is like alligator skin. Or a dry and cracked riverbed. I can’t feel the cracks with my hand, it just feels smooth, but they are definitely visible.

11

Hi Rachel -

The surface in the photo actually looks pretty clean to me. It should sand out and gloss over no problem. Even gloss coats can look a bit funky initially. Wet/dry fine sanding and a buff out usually takes care of that.

That is nothing like the problem I had on the “slabbing” fill coat I described in PM.

12

I’ve had that before. It was from too much resin and not enough hardener (unless it was over 100 degrees). Test your measuring bucket for accuracy. I always pour a little bit more hardener into the batch because my buckets suck.

Drag your fingernails over the board. If it scratches, you might want to sand it with 50 grit and rehotcoat it. If it is hard, then you are in the clear.

edit

Figured I’d clarify the last part. If it is hard and looks like what you have in the picture, then additive f will help the cause (problem would be heat/humidity). If it is soft with that look, then more hardener will take care of it next time around (calibrate, use a scale, or buy better buckets). You’ll know what you have by how fast your first load of sandpaper clogs, and that will tell the tale of another hotcoat or not. If it needs a second hotcoat, it will take a little more than half of what you used the first time and gives you a chance to polish it.

Now where is the picture of the whole board? :slight_smile:

13

hey remember that commercial for moisturizer lotion where they had that pretty lady with photoshopped / vegas edited skin where it shows the desert and her laying in a those laydown pool chairs, and an alligator crusing next to her and she runs her hand on top of its scales as it passes by. and they have some animation of how cool and soothing like swallowing real italian gellato icecream, mmm silky . …

I think it could be either mixing or contamination or lack of additive f, but seems like schroeder nailed it since he ran into issue like yours.

I had no issues with mine . . . but I did use an unorthodox method . . .

here’s the method I used . . .

Jim P / Herb S both said denature alky is best left out. Contrary to popular belief, the denature A leaves residue. So I left it out. I did sand my board

Hawtcoat:

temp was round 70

used the normal ration 2:1 RR to hardner.

1 cc per oz of hardner Add F

did the 2 cup method, no scales (get one measuring cup, mask tape inside for a mark for oz of hardner you want. container cup, larger, to hold resin. fill to mark with resin, pour in container. fill to mark with resin pour. Hold breath, measure cc’s Add f, pour in container. fill hardner to mark, pour. release breath, Gekko State doesn’t have a uber respirator, only dust masks for this mission ). I stumbled across the post describing the method above, so its not my invention. The reasoning is since volume is measured via the same cup, same mark, I get a near perfect 2:1 ratio. its simple it’s fucking genius . . . :slight_smile:

Owwch . . . sailor mouth slip up.

mixed for two minutes / alligator + transformer seconds, not speedy american seconds, scraping bottom / sides all over. One thing fo sure, I hit up all the angles during mixing, did everything except mix with the container cup upside down, getting all the resin mixed up in here. Since I counted slowly, it might have been 3-4 stopwatch minutes.

brushed it on, but it was thicked and looked jacked, but settled. Put board in outside container (so birds wouldn’t shat on my board or big bugs land in it or dust / dander or the night invading cats step all over it), and left,

Next day it was smooth as glass . . . with a few uneven spots. I was so amp’d I was skipping around how it was good. TG. Thank God.

14

It looks to me like your alcohol might not have been fully evaporated??

Other possibilities are blush residue that floated to the top…

I have seen this also occur when I decided to make “just one more” pass with the brush when I should have left it alone!

resin already thickening and not leveling out…

Use the F…it thins the resin some and helps with blush and bonding…

M.

15

Mix your RR by weight, get a cheap scale at office depot for 12$. the mixing weight is 55% to 45%. The epoxy is a bit heavier than the hardner.

Those white streaks might be from over working the resin. Those are probably from the last tipouts, or from a re-pour. Walking the hotcoat too much add millions of tiny bubbles that end up looking like white streaks or blush.

One trick is after you layed the hotcoat down, come back with the heat gun and gently massage the bubbles out with heat. The heat loosens up the epoxy and lets the bubbles out. But you can F it up and make it slab off too, so becareful.

Best is to pour to cover the board, cross stroke, level and pull off excess at same time, then tip out once…and walk away.

Keep away from the DNA, but use Additive F. ALso make sure everything is nice and sunny wary. Sunny warm material always makes a lamination, hotcoat, or gloss. Using it cold or barely warm, will just cause grief.

16

Okay so I was working on another board installing a leash loop and was using some extra resin from that to rehotcoat a section of the tail that had been subjected to a couple sand-throughs. I used Additive F this time, hoping that would fix all my problems. I went back this morning to pop out the plastic straw I used to make the loop and noticed that on the hotcoated area it still had a little bit of the alligator skin cracking, although it wasn’t as bad as the other board.

In sanding I found out that it does go away without too much effort, but gums up the sandpaper like crazy.

So my next question is, if it’s not solved by using Add F, could it be the resin? All of these hotcoats have been done using a new gallon of resin I just opened. Is it possible there could be some sort of contamination that’s caused by the resin?

17

I guess? I mean, I’ve never had the problems you mention to that degree. If it keeps happening then that would be the suspect.

It sounds like it’s trying to slab, or do the brain / orange peal pattern. I only get this when I put too much product on the board. Maybe you hotcoats are too thick? You should be using just enough to fill the weave, I mean like 1/32-1/16 thick…right?

Maybe it’s the Additive F that’s bad? Have you tried a test on a scrap of what ever? Just mix Epoxy & hardner nothing else. see how it goes?

perplexing. It really shouldn’t be this difficult, and it should actually be easier than Poly resin. I feel your pain.

18

Rachel, I found that in mixing small batches of RR epoxy, that it’s harder to achieve the magic 2:1 ratio. I had the same problem with FCS plugs. The resin never got hard and had to be removed (messy). Your problem sounds like you got close, but maybe not close enough, leaving a gummy finished product.

Doug

19

As I continue to get even more frustrated trying to sand the hotcoat on the longboard, I’m starting to wonder how I will be able to fix this. The problem appears to be less of an issue when using Additive F. Admittedly I only mixed an ounce for the leash loop and trying to get a tenth of a cc is a bit difficult even with the syringes I have, and using a very small mixing cup (the kind they give you for cough syrup). Everything hardened properly on that one, there’s just a small bit of cracking visible.

Also, I can definitely see how I did not mix enough hardener on the longboard. After letting it try to cure and harden for several days I took it outside to sand and it was incredibly tacky and there were spots I hadn’t noticed before that were still wet. When I sand this, should I do it lightly and try to just scuff it up and then re-hotcoat, or should I sand through the top layer of cracked stuff and then hotcoat?

This is ridiculous, I have never had a problem like this, one of the many reasons I continued to use epoxy, even over PU foam.

Thanks for all the help guys, maybe we can get down to the bottom of this.

20

Also, I can definitely see how I did not mix enough hardener on the longboard. After letting it try to cure and harden for several days I took it outside to sand and it was incredibly tacky and there were spots I hadn’t noticed before that were still wet.

Hi Rachel -

It does sound like a possible proportioning error. There is some tolerance for less than perfect ratios but with RR, 2:1 is key. Spots that are still wet might indicate inadequate mixing?

I’ve also read that epoxy is particularly sensitive to contaminants. Mixing container, stir stick, syringes, brush… any of those could introduce contaminants that might affect things.

This is no knock on RR but even the most precise manufacturing facilities can make an error or run into “bottom of the barrel” sort of issues.

On hot coats or gloss coats that are FUBR, I’ve gone through whole packs of sanding discs, gumming each disc up, before recoating. It sucks. Sorry you’re having to go through it.