How to taper a foam core plywood joint for maximum strength

I am in the process of recoring most of the deck on my Sweden Yachts 34.

When I cut out the old top skin I made the mistake of not leaving room for a proper bevel between existing skin and the new laminate. The plan is to rebuild the deck with biaxial cloth, epoxy and Divinycell or Airex foam.

I'm trying to correct the mistake I made by putting a 3" wide marine grade plywood strip along the cabin. I would love some input on how to make the transition between the foam and ply.

I've attached a picture of the area and a cross section sketch how I envision it.

Should I glass over the ply before setting the core?

I'm suspecting that it might be better making a shallower bevel on either side of the ply/foam and glassing over it.

 

I don't understand what you are trying to accomplish with the plywood. There is enough width for a good overlap on the new laminate.

 

According to the West Systems manual the minimum bevel should be 12:1. The skin is 5mm thick, it should therefore overlap 60 mm on either side. Unless I want to glass over my portholes and cabin, I'll only get a 10-20 mm taper on the existing skin.

As I see it this will be a stress point, and the foam core won't give me much in terms of tensile nor shear strength. Using ply here would strengthen this area. Am I wrong?

I'm not worried about the new laminate, I'm worried about the whole side breaking up and departing from the cabin, so to speak.

 

Skip the plywood and use all laminate, transitioning from the cored area to the solid 'glass areas. You bulk up the transition areas, so you have enough "purchase" on each side.

 

I was thinking of that, it might be a better option. Should be stronger anyways.

 

some things never change

put a layer of glass over the foam core then fit 200 density foam core instead of the ply wood ! Its able to be bolted through for tracks etc and totally disregard the ply that will rot over time and you're back to repairing again