Bulkhead materials and chainplates

Im rebuilding an old soveral 30, Im haveing to gut the int, and replace everything. I plan on useing pvc foam core for just about everything. I have a 12ounce biaxle glass which will be on both sides. Im not sure if this stuff will hold up for the chainplates. Is there a better core material for chainplates? Should I use wood, solid glass? foam with lots of glass? Honeycomb? Im kinda at a loss here.

[Eric Sponberg]

The interior chainplates should be either solid fiberglass or fiberglass over plywood. PVC foam core is very weak. You should consider other marine grades of foam core for the balance of the interior structure, such as Divinycell or Core Cell. Airex will also do, as will balsa. Balsa has to be really well sealed against any water ingress, including the time it sits in your shop. But handled carefully, it will work.

Eric

Ok the foam I have is corecell I beleive. I used it to recore the deck of my merit 25. I have since forgotteen the name of the foam. Its yellowish, has a mat on one side and has the squares cut into it. Im not a guru at the core type or the diffences between them.
This project is a 77 Soverel 30 hull#3 with the tall frac rig. The raceing version Mark had designed for the 77-78 MORC and SORC.
I am planning to make all the bench and seat verticals tie into the bulkheads, thinking this will act as long ribs throughout the boat. I plan to add 2 extra bulkheads from the orignal Int design. one forward of the mast, one in the aft section under the cockpit. also I plan to move one of the currnt BH's a foot or so further aft. Which pushes 2 bulheads closer together,which I am hoping will secure the loads of the jib tracks. This will also give me more leg room in the bunks for the odd chance of sleeping on board. Im hunting the right type of core for this project. Balsa is not an option I want to get into as this boat will be raced hard and put away wet. Ive been trying to find more info on the divinycell and the corecell, and the differance of the pvc foam. I havnt had much luck in that area. I am going to use epoxy with the glass being of 12 oz biaxle and in some areas 5 oz Mat. I suppose I can can use 2 sheets of fir or marine grade plywood for the chainplate bulkheads. But Im not a fan of wood and I am trying to get rid of as much wood as possable. In fact That will probably be the only wood on the boat after Im finished. Any advice you can give would be great. I know my way around a yard pretty well, but I am allways searching for better ideas and better ways to tackle these large projects I seem to get myself into.
Thanks

[Eric Sponberg]

The reason for using wood or fiberglass in the chainplate bulkheads is twofold: Plain tensile and shear strength, and also, the torque of the chainplate bolts is pretty high and will compress soft cores when you tighten them. If you don't want wood, then you can make up your own panels with fiberglass to an appropriate thickness, say 1/2" or so, then laminate over with tabbing to bring up to 3/4" or so. More detailed engineering would determine the correct thickness.

Also, you can use G-10 fiberglass. G-10 is really dense molded fiberglass that comes in sheet panels. You can buy it in sheets from most plastics suppliers. Look in your yellow pages for plastics suppliers. Cut out the correct shape for the chainplate bulkheads with a carbide saber saw, circular saw, or table saw. You can get G-10 in various thicknesses. Install the G-10 in the boat and glass it over with an appropriate amount of tabbing. Drill the bolt holes to match the chainplates themselves. The solid fiberglass will not compress at all, and it is stronger than wood.

Eric