Re: Morgan Deck repair advice
well, before I weigh in on the glass layup, I would like to offer some food for thought on the foam and it's location for use. Looking at the original construction, the reason ply was used in the high load areas (winches, main sheet traveler, genny tracks, cleats, etc) is because of it's strength properties; particularly compressive strength. In your situation, with the exception of the stays (which carry the load down to the keel), all of the other load bearring hardware is through bolted through ply, with some areas having backing plates.
The advantage of using ply here is that when loads are applied (and on a 36' sailboat, there will be many thousands of pounds of force) it's able to take the strain and distribute the stress over a much larger area. This is where compressive properties become critical. If the core material easily compresses, there is a likelyhood that the mounting bolts will actually get pulled throught the glass and into the core, or even possibly pulled through and rip out.
Looking at the properties of the foam that your using, it's a 5 pound density (it's really not that much). Balsa core that has been properly saturated with resin is twice that, and plywood of the same thickness is roughly four to five times that of the balsa. This particular type of foam relies mostly on the glass for it's strength; it doesn't really add much to the overall layup. If you're already committed to this material, I would go heavy on the glass and use oversized backing plates for much of the hardware (stanchions included; especially if you intent to do any crossings). OK, enough of that rant...
As far as glass selection and layup, I would be looking at using a combo of the 1708 bi-ax and 1.5oz matting. Think of the matting as a glue/bonding layer within the laminates. Now, the 1708 has a .75oz mat backer on it. So, If it were me I would use the 1.5oz mat as the first layers against the foam, then build with alternating layers of the 1708 and 1.5 oz mat, finishing off with 2-3 layers of the 1.5 oz matting. The 1708 is a little thinner material than the 38.5 oz cloth allowing you to have more layers in a given thickness; much like plywood, more layers = stronger / stiffer laminate. Matting is excellent to use for top layers because it sands level allowing you to have a smooth surface for finishing; woven cloth and the likes will give you print through that will allow you to see the weave pattern on the finished surfaces. Even though you are looking to re-use the original skin, you will still be grinding and tapering seams between the skin sections to glass back together to re-form the solid surface.
As far as the number of layers to use for each layup? With the thicker reinforcements I would use laminating polyester resin and limit things to 2-3 laminates per layup. After that has kicked, then I would do the next set of 2-3. If you're using a laminating resin, there's no need to sand between layups (within a certain period of time).
As far as the width to prevent two edges, are you referring to the skin or the core sections? Skin sections I would do 1" per side (2" taper total) and do that tabbing with 1.5oz mat. Core sections I would butt up to one another.
These are just my opinions, hopefully other glass guys will weigh in.
