Okay I give up. I’ve had 4 batches of resin not cure properly. One hotcoat that was so uncured it still felt rubbery. It took a set of glass on fins 3 hours before I could even trim them. All with RR and fast hardener. I did another hotcoat earlier today with fast and the proper amount of Add F and while it feels much more solid, it still scratches with a fingernail. I’m hoping it will fully harden overnight.
The last time I had this problem it was because I hadn’t been using Add F. Now even with it I can’t get things to cure. It’s been over 3 hours since I glassed a batch of fins and the resin is still very gooey. Did they mix up the slow and fast hardeners at Fiberglass Supply? I’m running out of possibilities. I bought a heat lamp and even the extra warmth didn’t do much. It’s about 66 degrees where I work indoors with very low humidity. I’ve done a lot of work at this temp and never had this many problems.
Add this to the fact that one of my glassed on bonzer runners is off by 1/2" (!!!) and I just can’t deal with any more frustrations.
Are you using a digital scale? The ratios are slightly different when measured by weight rather than volume but a decent scale will give better accuracy. Many cheap ones are +/- 1 gram.
I think you know the drill… precise measurements, thorough mixing, etc. I’m pretty sure my epoxy batches are taking at least several hours to cure. Overnight before sanding seems to be normal. If it’s still rubbery, consider the possibility that it was measured improperly.
One of the wooden kayak sites says:
“For every 10 degrees F., the temperature falls (when below 77°F) the gel time in the pot will double. The thin film set will come close to a 1.3 increase in time for every 18°F below 77°F. The exact opposite will occur as temperatures increase above 77°F. The gel time in the pot will be cut in half for every 18°F.”
Your temperature is within adequate curing range so I don’t think that’s it. I’d give it a couple of days with exposure to as much warmth as you can muster. I’d give it a day or two at least and retest with your thumbnail. A thorough grind with coarse sanding discs and a re-coat might be in the cards.
On the side runner, consider a careful grind at the base to free it, and then remount.
Take a deep breath and remember it’s just a surfboard.
are you pre-heating the resin? I’ve never used RR. I use Fiberglass Hawaii’s Aluzine, which I hear is a similar viscosity (honey-like below 70º).
Its been cold here at night, so I when I’m getting set up to do any epoxy work I’ll either set the resin and hardener, or just the amout- unmixed- that I plan to use, in a paper mixing bucket (carefully, with a buffer and some disposable plastic) on top of an oil heater till it becomes fairly fluid, and I make sure the shop is at least 70º.
As far as the board that has the sticky hotcoat, maybe getting it warm will help. Some nice even heat… I actually use my car sometimes- the Volvo autoclave- I park it in the sun and put the board inside with a thermometer. It works!
Haha I’ve been taking a lot of deep breaths lately. Usually that’s my motto but both of these boards have been causing me too many headaches. A small patch here and there I can deal with. Re-hotcoating 2 boards is not pleasant.
Since I have to drive back to school on Monday with 2 finished boards I didn’t have time to wait any longer for the longboard to maybe cure. With the heat lamp on it, it did seem like it was curing a bit more, but only in 8" diameter spots. To cure the whole board like that would have taken days. I left it alone for two days hoping that would fix it but no luck so instead I just bit the bullet and sanded it off. I just put another hotcoat on it, this time trying to be super accurate with my measurements. I also used Add F and X-55. I hope the accelerator will speed things up enough so that it will cure properly. Fastest I’ve ever hotcoated a board and I could feel it gelling on my final brush out. So maybe a good sign?
Allan,
I preheat my resin in the microwave. Usually about 5-10 seconds, anymore and it’s too hot. Of the 4 batches that didn’t cure, I want to say one of them wasn’t preheated because it was just a fin and I didn’t think it was necessary.
I really thought I had all this epoxy stuff dialed in. So much for that.
I was going to say something about microwaving… I tried it a couple of times and it seemed to heat up way too fast and get way too fluid (also, I discovered that carbon fiber has tremendous conductivity- little bits of leftover strands in a cup from somewhere arced like tinfoil in the micro- it was wild! )
But, yeah, like Mr Mellor said, the mixing is critical. As well as using a digital gram scale I thoroughly mix by hand (bottom, sides and off the mixing stick) and then I use a drill-powered paint mixer to ensure complete mixing.
For what its worth, while none of this stuff is rocket science (what is?) it doesn’t always go as smoothly as one would like. Everyone has horror stories!
By the way, the surfboard thing has been such a boy’s club for so long, I think its really cool that a woman is making boards. I wonder if more women got into it, would shapes change?
That really sucks…I can totally understand the fin batches, though. I had to get a smaller scale (accurate to 0.1g) to do small batches, as my 1g scale just wasn’t cutting it; I had several batches that just wouldn’t harden…
That is a very good sign if it was getting really thick when walking out. You’ll probably see brush-strokes in the coat after it cures…I do almost every time I heat the resin (I heat it a lot more than you guys do, around 100-110 deg, or 1-1.5 sec per oz of resin in the microwave), if it is above 80 deg outside…
When you do finish, please show us some pics! I really like that 5 footer…the swirl came out great…
That’s strange about the AddF. I’ve been using less and less, and it doesn’t seem to change the cure for me…I’m trying to get away from it (and any other type of additive) completely, though…
If it is only 66 degrees where you are working you are not going to get the set times you desire. Even if you nuke the resin everthing you are glassing is cold and will slow down the set time. Especially if its a thin film like a hot coat. In the winter (NC) I keep my resin in a hot box (old cooler with a heating pad and thermostat). Before we glass I get the shop and the board etc to at least 75 degrees. If you have Epoxy that never completely sets up you either are missing the correct ratio or not getting it mixed completely. A .1 gram scale and a calculator are the way to go. Tare the scale, pour some resin, .45 times the weight of the resin (for RR), tare and add the indicated amount of hardener. If you pour too much hardener, divide the difference by .45 and add that much more hardener. I use the clear plastic cups you can buy like a hundred of for $6 at Sams. There is a remote possiblilty of a bad batch of resin but it sounds like you didn’t have problems when laminating. What John Mellor said at the end of his post was the best advice I was ever given over the years of making boards. Doug Mann from Hawaii who taught me quite a lot used to say: Dave, its just a board. Those boards can be pesky rascals sometimes. Good luck and hang in there! You are an inspiration to us all!!!
I’ve had the same type of problem too. One time i layed up 2 boards simultaniously with RR. One turned out perfect, the other never really cured properly. Then when they were finished. The good one, stayed snow white, while the “soft one” turned yellow in spots…go figure.
So i think it is the devil himself come back to torment you. You need to do more clean living, and sacrafice 3 small pigmy goats.
I think my problem was that I didn’t mix well enough to the bottom of the container. I’m always trying to fold the RR to mix, instead of whipping it…like Poly. Always trying to keep dem bubbles down. I knew I had the right ratios, and was even slightly higher on the hardner. I think the RR ration are like 55% Epox, to 45% Hardner. Even doing it on a warm day, with a slight nuke. Also I like to mix bigger batches because there’s an attenuated chance of mixing failure.
As I see it, this mixing stuff is probably the biggest draw back with epoxy. There are so many ways to epoxy faliure, and only one right way to sucess. i.e. temp, ratio, humidity, mixing, age of product…All have to be almost perfect to align to the perfect surfboard. I think this is the main reason it hasn’t completely buried the poly resin surf industry (my humble opinion). RR is by far one of the most easy to use systems, but still has some very specific needs and traits to make it work to cosmetic & durable perfection. But once perfected i feel it makes a better board, and is worth the hassle.
That’s strange about the AddF. I’ve been using less and less, and it doesn’t seem to change the cure for me…I’m trying to get away from it (and any other type of additive) completely, though…
JSS
I don’t understand why everybody here is using that famous addF? I’ve never heard of it outside of swaylocks and I’ve never used it. I shaped 3 epoxy boards, none with that additive and they all cured without any problem. I never had curing problems, except my first try on some testfoam when I mixed 1/6 in place of 100/60. My epoxy is always curing and I use a 1g scale.
after you mixed with a stick, take another cup and pour your resin from one cup to the other (scrape all out of it, you have time, it’s epoxy!).
That way you won’t have unmixed resin in the edges!
I use 2 types of epoxy: epovoss LN (laminating resin thay stays a bit sticky for perfect bonding to the hotcoat, this heats a lot if you mold it!) and speedcoat CN (this is the hot/gloss resin that can be use for molding too) all produced by vosschemie.
The ratio for Resin Research is 2 parts resin to 1 part hardener by volume. That would be 200% resin to 100% hardener. By weight it is 100:45. For example 100 grams resin, 45 grams hardener. The difference in the volume ratio and the weight ratio is due to the difference in the Specific Gravities of the resin and hardener. Adding more hardener than required is not good. More hardener will make poly kick quicker but with epoxy it can cause it to cure softer if at all. I think the window is +/- 5% before you start altering the properties of the cured product. In fact I thought someone on here mentioned that it was better to err on the less hardener side with epoxy. As far as stirring it Greg L in his Epoxy Glassing video whips the crap out of it with a paint stick. Maybe he will chime in but I don’t think he’s worrying about bubbles. Hope this helps.
Good news! The hotcoat I put on last night has cured rock hard. Besides all the zits and a few bristles I missed, I don’t see any leftover brush strokes. It actually looks like one of my better hotcoats. I’m hoping I can just get away with starting at 120 or 220 and treat it like a gloss coat.
I’m going to have to concede that perhaps my mix ratio was way off on the one hotcoat that was still rubbery. I think for everything else I’m going to use X-55 except installing fin boxes.
I’ll agree with Resinhead about mixing being the hardest part about epoxy. But you still can’t beat the very little smell and almost no VOCs. Especially since I usually work indoors.
Now I’ve just got to grind off that fin and glass it back on without anymore problems and I’ll be much happier.
I preheat my resin in the microwave. Usually about 5-10 seconds, anymore and it’s too hot. Of the 4 batches that didn’t cure, I want to say one of them wasn’t preheated because it was just a fin and I didn’t think it was necessary.
A tip a long-time epoxy pro gave me…
Get a 5 gallon bucket, fill with hot tap water, and leave the resin in there for a significant time before you mix (like 20-30 minutes). The RR resin is very tough to mix at inadequate temps (but 66F should be OK, I did a lot closer to 50 F).
Glad to hear that you had better results with the X55. I used to have similar problems to yours when I didn’t use a scale. I bought a $20 digital scale on Ebay and my problems went away. I also sat down and made a chart that I use now to mix my resin. I keep it in my shop on the wall next to where I mix the resin. It starts with 1 and goes to 40. One side is the oz. of resin and next to it is the oz. of hardener. I found that before the chart I was using too much hardener and would always end up with extra resin on the 3 gallon kits. The chart also has the mix ratios for the Aluzine which are different than the RR.
The X55 has also been great, just remember that it’s hydrochloric acid and should be handled carefully. I took the time to read the MSDS sheets on the RR website, they are very informative.
Another tip is to try the super fast setting epoxy from FBH. I use it on all my leash plugs and fin boxes. Once mixed it goes to a hard gel in less than 30-40 seconds. I use the grams on the scale and mix only enough for one box at a time in tiny dixie cups. You can set your boxes and leash plug and be glassing immediately.
Are you using scales? One sure way to f%@k it up with epoxy is to measure it by volume, not weight. Get some digital ones accurate to a tenth of a gram or whatever if you don’t already.
When something like this happens to me, I hate to admit it, but it is almost always operator error. I could swear up and down on a bible that I measured correctly. Why then, when it was time to order more Resin Research, did I have 1/2 gallon of resin left over but no hardener? Yikes! I have the most problems when I use Additive F, and I completely stopped using it on colored board hot coats
In the shop they tell me every time to mix by weight! Because the resins expand differently with the temperature, so you have to mix in different volume-proportions when the temp changes (but luckily that’s not that big difference but it can make your mixing error bigger)
And when you heat one component you’re just begging for troubles if you mix by volume.
You need to have the right proportion of the molecules. Epoxy don’t uses a catalyst that gets out afterwards like poly does, epoxy curing is a polyaddition. The molecules of both parts form a big molecule with each other, so it needs to be mixed really well in the right proportion.
AND THE ONLY WAY TO MEASURE MOLECULES IS BY WEIGHT!
If volume works for you, great. But if you want to have the best epoxy possible or want to eliminate the chance of bad curing do it by weight. If you have a 1g scale, avoid mixing less than 50g (=1.8oz).