Cracked fiberglas

[sailortoo]

Sirs:
I made an anchor pulpit using a 2" x 12" x 48" pine board. The board seemed to be dry, I shaped it, sanded it, and overcoated it with polyester resin with glas cloth about 3/16" thick. After sanding with 80 grit sandpaper it was gel coated.

PROBLEM: After a year the pulpit has cracks along the edge (2" demenison) in several places. The cracks are through the gel coat and resin and have opened up and the underlying wood is visible. Cracks are about 1/16" wide and are only on the edges. The top and bottom has not cracked at all.

Is the problem possibly moisture from the wood? Any suggestions are appreciated.

[Valkyrie]

Did you also cover the edges with glass cloth? If not, theres the problem. I've never used pine to laminate myself but I do know even dry it has alot of sap in it that continues to dry for years.

[wdnboatbuilder]

Pine has alot of pitch and polyester nor epoxy will stick for too long. in order to stick it has to embed itself into the wood. Pine has so much sap (pitch) that it just won't allow the poly or epoxy to embed itself, same goes for oak ecept oak it the grain, it is so tight that it does not allow to embed either. Polyester resign will allow moisture through and it might be delaminating.

[sailortoo]

Bruce:
Thanx for the heads up. I have removed glas when cracks were found using a grinder and found cracks in the wood. I ground to the bottom of the cracks and plan to use ss screws to try to reinforce the cracked areas and then re-glas the pulpit. From you information, however, I may be wasting my time.

Merry Christmas

[wdnboatbuilder]

Now I will tell you that I'm not that well versed with polyester and some who has more experience in that dept HELP. but I do know epoxies. what I have said about epoxy is very true. In my opion which you can ask the same question to 100 boat builders and get 500 different answers, if the pine is in good condition grind the glass off and varnish the pine. If it is a good yellow or long leaf pine then it should not rot for awhile. ooops I said the V word.......varnish

[Ssor]

One of the problems that plague projects like this is sharp corners. Use your router and round all of the edges to a minimum 3/8 inch radius. Then whether you go back to the glass or if you coat with epoxy and varnish over for UV protection you should be able to avoid cracking at the corners. Remember that if you start with dry wood and wrap it with an inelastic cover and water gets in it will swell and break the cover.

[fiberglass jack]

it sound like delaminating u probally used waxed resin during the layup and the cracks are where u stoped durig the lay up yes the pine can contain water and sap that may be the problem but after a year and the warm weather in florada i dont think so maybe in a canadian winter just take a grinder and go to town remove the crap and reglass but use mat between layers of cloth and make sure the resin un waxed

[sailortoo]

OK. Posting some pictures of the thing. Overview and some close ups. The glas and gel coat are ok on top and bottom. The cracking was only along the edges of the board. I have removed material to the bottom of the cracks. If I repair would it reinforce the resin and glas if I bored some holes, say 1' deep into the wood and backfilled with resin?

Thanx!!

[Ssor]

That damage appears to me to be the result of the wood getting wet and swelling. Measure a dry piece (same species)as thick as your example. Measure with a vernier caliper or a micrometer and then soak the piece in water for a week and measure again. If you find that the swelling was substantial change to a species that is more stable. By substantial I am referring to percentages a 3/4 inch board is .75 inches if it swells to .80 inches that will be 6.7 percent. I don't believe that fiberglass-resin composites have that much elongation.

[fiberglass jack]

u drill hole dont back fill with just resin use a paste take some chop glass and cut it up good like into 1/8 to 1/4 inch length do this in a paper cup with a sissors get so resin and add hardner then the fiber and stuff the holes with it.if u glass the repair area grind a couple of inches on each side into the good glass and try not make the repair resin rich by the way next time use foam insead of wood its easy to shape and it has no moisture

[Guy G]

I'm not sure of what your doing after you laminate your wood, If you run any screws into it your allowing moisture in through those areas. I use pine and with out any problems for some uses. I always use dry wood then I take resin and thin it with acetone till it is a thin as water. I kick it off and brush the resin into the wood till it stops sucking in the resin. Then after it cures just litely scuff the wood before applying my lamination coats resin/mat. I try as I might not to run any screws into any type of wood if possible. Wood is okay to use if you can properly seal it. Your always taking a chance if you run any screws into it though!
Best of luck to you!
Guy