Rockhopper - Solutions!

[Vindi_andy]

Mike how did you do the square corners of sides to roof and how did the fibreglass lay over them.

[mikeschn]

Mike how did you do the square corners of sides to roof and how did the fibreglass lay over them.

I rounded over all the edges with a router bit (I think it was a 7/8" roundover).

The fiberglass wrapped around the corners pretty nice as long as we put the resin over the roundover in one pass.

At first we put the resin up to the roundover, and with the next batch of resin we continued over the roundover, and it wanted to lift.

Mike...

[pepper]

It's going to rain there today. Are you going to fiberglass?

[mikeschn]

I pulled out the teardrop and started sanding. It's not going well.

I am using 60 grit sandpaper on my random orbital sander, and I go through a sheet of sandpaper in about 30 seconds. I'm going to need cases of sanding disks at this rate.

What am I doing wrong?

Mike...

[nevadatear]

Is it not dry enough? I found that out the hard way. You still gum it up, but not as fast. I also found a drywall sander worker better for first pass. It was a pain to do by hand, but i could clean it better and it didn't get dull. Also, if you use an air hose to clean your sand paper frequently, you can make it last longer. It is mot so much that the sandpaper is worn down, but gummed up. Spray off the paper and it is sharp again for a while.

[mikeschn]

Well, I've let it cure for a week. So it's pretty dry. But yea, the sanddiscs are gumming up very quickly.

I think I am just going to knock off the high points, and then put another coat of resin on it, but this time the resin will have the surface wax in it. Hopefully it'll sand easier!

Mike...

[starleen2]

my experience with fiberglass resin is that you must blend the resin before adding the catalyst. It seems that some of the styrene settles out when the container sits on the resale shelf for a period of time and causes the resin to be a bit tacky and take longer to cure. A simple mixing or blending of the resin before adding the catalyst will helps to alleviate any problems. I usually invert the gallon container several times to ensure a good blend. Gummed up discs mean that the resin has not cured fully. if you used "unwaxed" resin to start with - then you must put on the final "waxed" coat for the undercoat to fully cure - then begin sanding. hope that helps

[tonyj]

Depending on the poly resin you are using, many laminating resins do not require sanding between coats. Additional coats chemically bond to the previous coat. Final or finish coat should contain wax which makes a good hard sandable surface. Sanding laminating resin will gum sandpaper quickly, and you don't really want to build multiple layers of waxed resin because it does require that mecanical bond produced by sanding.

Instead of sanding those high spots or drips and runs between coats, use a scraper. (I am assuming you are using polyester resin and not epoxy, since you have used the term "fiberglass.")

[pchast]

Stop Sanding.....

Its the wrong technique.

Use a card scraper.

when you sand you are taking off the sides around those high spots as much as the high spots themselves. Any paint scraper, I prefer a card scraper, will help level those runs. We had a lot of them on the canoe we just displayed... Actually you don't have to wait for the epoxy to totally set to use a scraper on it.

Have fun.

[doug hodder]

At a week, it should be sandable. Mike, did you use metered pumps? Doug

[rowerwet]

what brand of epoxy did you use? each seems to have different cure properties. I have some that is made not to blush (wax on the surface when it cures) and some that has to be sanded between coats if it cures.

[tonyj]

I think we need clarification--is the resin you are using polyester, or are you using epoxy?

[mikeschn]

It's polyester resin from US Composites. I did not add any surface wax to the mix for the first coat. It's the first coat I am trying to sand.

The next coat will have the surface wax, which should make it easier to sand.

No metered pumps. I used a 1/2 teaspoon measure for the hardener, and an accurately marked plastic bowl for the resin.

Mike...

[nevadatear]

Whoops. My remarks were for epoxy i'll shut up now

[rowerwet]

what was sad earlier about wood and resin expanding at different rates is true, I used boats that were built of plywood and marine epoxy, every year we made a "shoe" of polyester resin and heavy glass cloth (youth rowers, ran into and over a lot of stuff) once a section of poly resin is cracked or torn loose it all comes off quickly in sheets.
Epoxy becomes part of the wood and will take the top layer of wood with it. I know plenty of people who have built boats with poly resin, as long as the boat is stored out of the sun and weather and any dings or scratches are treated right away, one guy has a 25 year old boat that is doing just fine.