So I’ve tried to scour previous posts and have not had a satisfactory answer to this question. If it exists a link to previous thread is much appreciated!
I’m trying out poly resin after using epoxy exclusively and am having issues with lamination: with poly sanding the cut laps and cleaning the nose/tail prior to deck lamination was a pain. The lam resin instantly gums up my sanding disks and I went through about a dozen before getting it all smoothed out. I am using a random orbital sander that I typically use for epoxy. I’m definitely a novice glasser, but I do feel that I effectively pulled the bulk of the laminating resin out of the glass when I layed my lap. There was no major excesses, and the issue of gumming up the paper/disks happened even while knocking down the edge of the cut lap. I also allowed a 48 hour cure before sanding.
Based on pervious threads I tried:
-Using a coarser grit of disk (instantly gummed up at 100 and 80 grit)
-Cleaning off the disks as I go (brush would not even come close to getting the lam resin out of the disk and cleaning it with acetone removed the grit from the disk…)
-Layering sanding resin over the cut lap edge and sanding (had to get through the sanding resin and… back to the tacky lam resin)
-Hand sanding with a sanding block (all grits of paper gummed up)
-Transitioned to a medium sanding pad on sander/polisher (no more effective)
What am I missing in transitioning from epoxy to poly?
This is from an amateur who built a handful of garage boards about 50 years ago, so it is far less than gospel If nothing else, maybe my reply will provoke one of the knowledgeable pros here into giving you an authoritive answer. If subsequent answers disagree with mine, you can pretty well take it on faith that they are right and I am full of manure. But anyway -
My recollection is that a poly laminating coat will always be gummy to sand. My recollection also is that best practice is to squeegee as much resin out of that coat as you possibly can with out wrecking the lamination. The 3D weave of the cloth should clearly show after this operation. When the laminating coat(s) is completely cured, a coat of sanding resin is applied to the entire board, Poly sanding resin/catalyst formulations are specifically designed to reduce or eliminate the gumminess. That also makes it more brittle, which is why it is not used for laminating. All sanding is done on the sanding (or “hot”) coat. Once the glasser is satisifed with the smoothness of the sanding coat, a gloss coat (which I seem to recall is thinner sanding resin with wax added) is applied, but not sanded. Gloss coats became optional in he interests of weight savings.
Ok, you real pros, now tell this guy how wrong I am, and give him the correct answers
To clarify, my lam was good in terms of pulling out the excess resin. The weave was clearly visible thoughout when I was done. When I’m done the cut lap, there is a sharp edge and at the nose and tail there are creases in the glass where the lamination overlaps. I may be a novice, but I know those have to be knocked down before the next lamination and also the hotcoat. I’ve attached an example picture showing what I mean (mine are neater than this, but they must be smoothed). Here is a video of what I’m talking about. Even doing this with a sanding disk and coarse grit gummed up instantly.
Thanks for your reply, though. More helpful than “Someone else do this…” I know this is a basic question but like I said, I’ve searched the “archives,” tried what I found, and it still didn’t work. Swaylocks is great resource but the search function for a question this specific is not ideal.
Your pic shows a freelap, not a cutlap. A cutlap would have involved you taping off a lapline and you actually cutting that portion of the lap which extends unto your tape. In that event you’d have a nice even line to knock down. Some people use a file to to it, some use a grinder or even a dremel. The folds in your corners are there because you didn’t cut a vee or otherwise lay them flat when you squeegeeds them.
Laminating resin isn’t intended to be sanded. It will always be gummy, which ensures a better bond with the fill and finish coats that follow. That’s why people use files and grinders on the rough edges. If you’re that hot to use a sander on your edges (which isn’t the best way to do it) then you can baste that exposed edge with some sanding resin. Sanding resin is different because it includes a wax additive that enables the resin to set up hard instead of tacky.
So yeah, this one is going to take some work to fair out. NEXT TIME, tape off a 1" lap line and mask off the dry side of the board so no resin gets on it while you laminate the wet side, then come back and cut the lap with a razor or exacto after the resin sets but before it cures. IMO you should learn how to do a cutlap before moving on to a freelap (which doesn’t use a taped cut line) because doing a clean freelap is harder than doing a clean cutlap.
There are vids that show glassers of varying skill levels doing this. Some are better than others, so look around. Here’s one:
Thanks for bailing me out! At least I wasn’t completely wrong about the nature of lam resin Now that you mention the process, I did cut laps on my boards, and gently used a Surform file (which was my blank shaping tool, anyway) to knock down the proud edge.
One thing I am going to guess is that you are not catalyzing your lam resin enough. Iuse a die grinder and I usually get around the whole board with one ROLOC Disk that I drop in Acetone and reuse. Your laps are so big and fat that you are not just grinding the edge, but also the big fat lap of cloth.
First, you have there a not so even free lap. You need to work it out a bit better next time to make it flat as possible. Depends on the tail and edges, you make the intended relief cuts. If you will use tints; be careful with these relief cuts if not you will have a darker color and couple of tiny bubbles (that finish without the tint…)
If you have a fish tail; is better to cut a triangle shaped piece to put over because is not possible to follow a deep crack completely to have an smooth flat lap (to the middle of the crack)
The steps are very simple; and you forgot one:
-laminate the bottom. Sand only the tail and nose laps edges. In case that for any reason you have a non cured bottom lamination; do not sand anything and just laminate the deck; if not will be worst.
In case that you have a gummy situation and you do not have the right tool (and orbital sander is not a right tool for this with polyester) the secret tip is to brush a minimum of UV resin there, then sand it off.
Brush monomere.
-laminate the deck.
-Hot coat the deck AND laps. There you go; smooth to sand it.
Sometimes; depends on the situation, you can hot coat the deck to the rail apex (with a tape all along the rail) not sanding the lap, then fins and then hot coat the bottom.
If nothing else, maybe my reply will provoke one of the knowledgeable pros here into giving you an authoritive answer. If subsequent answers disagree with mine, you can pretty well take it on faith that they are right and I am full of manure. But anyway -
