To start with I’m new to the forum and I’m a windsurfer, I hope though that you will accept me here
I have started to make a plywood fin for my surfboard with fiberglass and Poly resin.
Now I’m at the point where I’m supposed to do the finishing coat(hot coat).
Unfortunately I can’t buy any surfacing agent here where I live, I tried to just ad a little more catalyst to the resin but it just wont fully cure.
After that I putted the fin with the applied resin into a oven I have in order to give the resin some more heat and what happened is that some of the fiberglass is now totally visible again???
So my question is, is there any possibility to get a nice finish coat with the material I have??? BTW I have Styrene and parrafin but in solid form.
This is a common issue and worth a search for a longer answer.
You can try melting the wax and adding it to your lam resin. might work. Also, you can put another layer of lam down and cover it with plastic to keep the oxygen off of it. You should be able to sand then.
Melt wax first and add it to your lam resin. 5% sounds a bit much but not too bad. I think it is something like 2-4% but whatever. Styrene is not a must but it helps thin out the resin. Additive F is also called Styrene in Wax
A “hot coat” is not the same as a finish coat. Hot coats are used to fill the weave in a lamination and allow you to sand before finishing. They are also called a sanding coat for that exact reason. Experienced laminators know exactly how much resin to use for a hot coat because most of it gets sanded off. getting the amount just right cuts down on waste, and sanding.
Surfacing agent is nothing more than wax dissolved in styrene. If you have no way replicate it or make your own, wrap the fin with wax paper. Make sure the paper makes good contact with the entire surface. Poly resin is known as an “air inhibited” resin. Meaning, it won’t fully cure when exposed to air. Surface agent forms a wax film on a cured batch that creates a barrier to the air, allowing the resin to harden completely. Wax paper can be a substitute for applications that don’t have extreme or complex curves in the part being made.
And something else, cause of the hole work I always had some leftovers. So I just let the over resin in the tube witch then became totaly hard and none sticky…
What is the difference ??? the thikness, if so then the top of the nugets should still be sticky, no?
Sorry for the many questions im just happy that i found somebody to ask…
Looking at the picture of the two pieces of extra resin-the edge of the left one looks like wax.
Could it be that your resin already has wax, like a gloss coat resin? Are you buying from a fiberglass supplier?
If your resin has wax in it, that would explain why the pucks are not sticky (wax came to the top properly and resin cured without air) and the fin is sticky (wax not able to rise correctly through the cloth and/or was overworked during lamination, causing air to reach the resin and inhibit the cure at the surface).
Did you try the plastic film or waxed paper? Did it help?
I did a side of a board once with a final coat of gloss resin and brushed it too many times. I got sticky spots everywhere from disturbing the wax. The folks here showed me my mistake and waxed paper helped most of them to cure without being sticky. The next gloss coat went much better.
If the glass is not bonded to the fin where it looks dry…you may have to start over.
@jrandy what you see there is plastic on the leftovers, I use small plastic cups for my resin and when it hardens out it burns/melts it.
I haven’t tried out the wax paper yet but i will. I guess after I brushed the resin over the fin I will just apply the paper,right?
Something else I tried was to stir melted wax into my resin, witch went directly hard:) I’ll try to get some kind of solution in the big city’s.
One last thing I did yesterday was applying a thin coat of wethershield yat varnish that provides you a gloss finish, but i didn’t worked too well either.
I did some more tries today and actually got useful results, as you can see below.
The one on the right, I just rubbed a candle over it and it worked no more sticky sticky.
Plastic did not worked at all and the wax paper, either it is the wrong one or I did something wrong, was not so great either, I still had some sticky parts here and there :?
Tomorrow i wanna try and sand it to a nice finish, any suggestion what grid I should use for the wax???
Meanwhile I sanded my fin once more down to the wood and then glassed it again (this time two layers, photo below)
after that I did a filler coat an a pseudo hot coat ( the candle wax will follow tomorrow) wish me luck…
and it worked no more sticky sticky.