My Epiphany - Sanding - Sanding - Sanding

[parnold]

I'm having interesting problems with polyester resin and Loew's underlayment 5mm Luan. If you've read my last few posts, I had an issue with some resin that I under-hardened. I have since that time, sanded down the "offending" resin, which had about 98% hardened by the time I got to it with the sander. I applied some additional resin, using the correct mixing ration, and had the same problem, both going over the first coat, and where it was applied to fresh, virgin luan.

Last night, I tried sample #3. I over-hardened the resin, and did a test area applying a thick (to the point of running) coat over fresh luan, resined, sanded and recoated luan, and resined, and sanded only luan. The thick resin cured in a normal amount of time, within an hour or so, it was hard and dry to the touch.

Something in the Luan is retarding the curing of the polyester resin. I checked the batch code on the resin with the manufacturer, and it is current product. I sell several hundred gallons of this product every year, so I know the quality is top notch also, and there are no bad batches at the moment.

Tonight's project will be to attack the cured thick spot of resin on the trailer, to see if I can separate it from the substrate at all. If it fails tonights test, my only option is to sand the entire trailer down again in about a week when it has dried/cured, and run some tests using a sealing primer like a urethane primer. If it passes tonight's test, it means i'll be adding a few weeks to my build schedule, since dry between coats for at least the first couple coats will be a week instead of an hour.

This has me very puzzled. and frustrated.

[StandUpGuy]

If it is 98% hardened I think it will harden off on its own with time. Frankly I think if you applied the resin with no hardener with enough time it will set. I say just be patient and do other things if you have them to do and see if it sets the rest of the way on its own.

[Oldragbaggers]

I am really sorry to hear all this Paul. What a disappointment, not to mention all that additional work. Very weird. Could it be something with the glue in the Luan maybe??

[parnold]

That's what I'm thinking Becky, either the glue, or they use some type of preservative or anti fungal something or other (technical term). I have another call into the techie right now. They sell a lot of this resin in the marine market, so they are not unfamiliar with application to wood.

[parnold]

The hardened section where I laid the resin on real thick passed the screwdriver test. I gouged at it in several places, and scraped down to the surface of the wood without any chips popping up. I did one last test before dinner. The lower front board is now covered entirely with a pretty thick coat of resin, and as it was setting up, I put another coat on. I put it on just thick enough that it ran in a couple spots, but I was able to roll out the runs as I caught them before they set up too much. Worse case scenario is I may have to replace this one piece of wood, which will be an incredible pain, but doable.

I noticed in one of the spots where the resin hadn't set up properly that I was able to scrape away some red goo. This leads me to believe that the resin is interacting with the stain that they use on the wood. I tried wiping an untouched spot of the wood with a rag soaked in acetone, and I was able to get a little red on the rag, but not too much. I'm more afraid of what the acetone might do to the glue, than what the stain might do the the resin.

If tonight's test doesn't produce satisfactory results, I will have to get some more aggressive sandpaper, and sand off every bit of resin, and then run some tests with a urethane sealing primer.

Cross your fingers for me!

[StandUpGuy]

Ach! What a pain. I can sympathize after my fiberglassing custom shower pan. I had to grind my bad work down and sanding down fiberglass is tough going. The stuff is like a rock. The dust from it is probably going to kill me later on in life for having breathed it.

[parnold]

The stuff is like a rock. The dust from it is probably going to kill me later on in life for having breathed it.

I have respirators if it gets to that point. In the old days I used to paint cars wearing a bandana.. lol.. not so bright.

[Oldragbaggers]

Between the fiberglass sanding I've done on the teardrop and all the boat bottoms I've sanded, I'm doomed to an early grave I'm sure.

[parnold]

I don't suppose anyone is interested in seeing a picture of me sanding?

[Verna]

Thanks, but no thanks, Paul. I've sanded enough wood and I'm sure your sanding isn't any more exciting. Gotta take the good with the bad. Did you notice I didn't offer to help, either?????!!!!

[parnold]

Thanks, but no thanks, Paul. I've sanded enough wood and I'm sure your sanding isn't any more exciting. Gotta take the good with the bad. Did you notice I didn't offer to help, either?????!!!!

This is so much more exciting that wood sanding though, I'm sanding the polyester resin!

[pohukai]

LOL...sanding hardened epoxy is difficult and slow. I've learned, before the epoxy sets up, get the surface to the best possible finish to minimize the cosmetic sanding (removing sags). Soft epoxy is easier to work with than hardened epoxy.

[pappaw]

Paul, that's going to be one pretty camper

Cheers

[parnold]

Thanks Pawpaw. I'm certainly putting enough sweat into it! (in the 90's here today and I'll be sanding when i get home from work). I can't wait until the windows, door, and a/c are in, then I'll start on the interior.

[eaglesdare]

hey, i would like to see you sanding!