Beechwood Chip Posted October 6, 2015 Report Share Posted October 6, 2015 A friend of mine has a flat roof with a hatchway. He wants to build a fiberglass cover to replace the wooden one that has started to rot. The hatchway is about 60" x 18", and the sides extend about 4.5" above the roof. Neither of us has any experience working with fiberglass.So, our plan is to watch some videos, then make a wooden form for the inside of the cover and lay the fiberglass over that.Should we coat the form with something to keep the fiberglass resin from sticking?How should we reinforce the fiberglass to attach the latch and hinge?Anything else we should know?Thanks! Quote Link to comment Share on other sites More sharing options...
Boatworks Today Posted October 6, 2015 Report Share Posted October 6, 2015 Pm me with some pics and more detail :-). BoatworksToday@gmail.com have the subject heading WTO so I catch it! Quote Link to comment Share on other sites More sharing options...
wdwerker Posted October 6, 2015 Report Share Posted October 6, 2015 Sneaking off in private, for shame, some of us want to know as well ! Quote Link to comment Share on other sites More sharing options...
Just Bob Posted October 6, 2015 Report Share Posted October 6, 2015 Sneaking off in private, for shame, some of us want to know as well !+1 Quote Link to comment Share on other sites More sharing options...
wtnhighlander Posted October 6, 2015 Report Share Posted October 6, 2015 I would suggest to make the hatch from wood, maybe 1/4 ply on a frame, then totally encase it in fiberglass mat + resin. Quote Link to comment Share on other sites More sharing options...
Boatworks Today Posted October 6, 2015 Report Share Posted October 6, 2015 I think I understand what your looking to make. Is it something along the lines of the hatch cover in this video? Only larger?probably the easiest way to build this would be to make a plywood version of the cover and glass over it top and bottom (encasing the plywood). Round over all the edges so the glass can wrap the corners.as far as materials, you'll want roughly a gallon of laminating polyester resin, 4oz of Mek-p (hardener for the resin), 2 different types of glass (1.5 oz csm aka chopped strand matting, and 1708 biaxial). You can buy these rolls in different widths, so you'll need to figure out how much you'll need. Figure on laying 3 layers of csm and 1 layer of 1708. The order should go like this: csm, 1708, csm, csm.youll want to use this same laminating schedule on both the top and bottom of the plywood hatch. Use a solvent resistant roller and chip brushes for wetting out the glass, and don't worry about any excess glass strands hanging over the edges. That can all get trimmed off after everything is cured.because this is a laminating resin, after the glass has set up you'll need to apply a light coat of pva (poly vinyl alcohol). Think of this as a liquid plastic. Poly resin will not fully cure unless the surface is sealed from the air, the pva will do this. Pva is water soluable, so the following day wipe it down with warm water and a scotch right pad to remove this film. Sand the glass smooth and topcoat with either paint or gelcoat.when sourcing the materials, do not get the resin or glass from a big box or automotive store. It's poor quality. Here are some sites I'd recommendus-composites.comexpresscomposites.comfibreglast.comthe poly resin needs to be catalyzed around 1%. Figure roughly 10 drops of mek-p per ounce of resin. Depending on the temps, you'll have roughly 10 minutes of working time per batch. This is at 70f. The resin needs to maintain a minimum of 65f during the cure cycle which can take up to 24 hours to completely do its thing. If you have any questions just let me know :-) I didn't think that this info would be something that others would find interesting which is why I suggested sending me a pm ;-) Quote Link to comment Share on other sites More sharing options...
Tom Cancelleri Posted October 6, 2015 Report Share Posted October 6, 2015 I've worked with fiberglass in the past. It's some nasty stuff, the resin stinks, and the particles from cutting fiberglass isn't something you want to breath in. Make sure you wear proper protection, and work in an area with great ventilation. Quote Link to comment Share on other sites More sharing options...
Beechwood Chip Posted October 6, 2015 Author Report Share Posted October 6, 2015 Thanks! This is great info. I generally prefer to work with wood, but this needs to be water poof, rot proof, and light weight. Quote Link to comment Share on other sites More sharing options...
Tom King Posted October 7, 2015 Report Share Posted October 7, 2015 (edited) It would be worth looking at surfboard glassing videos on youtube. It's the same sort of thing minus putting in the graphics. It can go pretty easily and quickly, or you and try to figure out the details of how to do it yourself, and it can get away from you. Watching a board being glassed will give you a feel for how it goes. More resin does not make it stronger. You want to saturate all the glass, but much beyond that is just work and materials for nothing. You can see when it's saturated easily.For thicker laminations with matt instead of just the thin glass that they use on surfboards, one of the little stiff bristle rollers made for the purpose is well worth having. Acetone will do cleanup before it kicks. http://fiberglasssupply.com/Product_Catalog/LaminatingTools/laminatingtools.htmlHaving said that, I'd probably build it out of Aluminum, Stainless Steel, or Copper, or some combination of those. Edited October 7, 2015 by Tom King Quote Link to comment Share on other sites More sharing options...
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