Adding horizontal bulkhead to beach cat

Hi, on these old P19s they first had no longitudinal reinforcement. Later they had stringers and eventually I heard they had a horizontal bulkhead because the bows were still tearing off.

I've taken the deck off mine. I have some .5" rigid foam to make a bulkhead out of. Few questions:

-For the bulkhead, should I do one or two layers of 6oz cloth on each side?. If 1 should I orientate it 0/90 to the hull or bias? If 2 layers I'd assume I would lay one each way.

-When I glass it in is it enough to just attach it with glass tape on the top side or should I cut holes in the bulkhead and turn the boat upside down so I can glass it in on the other side too?

-There's an additional vertical bulkhead in front of the beam. Should I cut a slot in it so the horizontal bulkhead is one piece or can I just cut a piece to fit in that space?

I've repaired tons of beach cats before just never worked with rigid foam for construction. Thanks for any help

 

Hello Morris, how thick is the hull itself? How long x deep x wide is the cavity?

 

Its about a foot wide and I can get it in there where it tapers to a few inches. It's probably about 2 feet deep and 8 feet long

 

Perhaps some 8' long, .5 x 4" stringers fastened to the hulls and more and evenly spaced vertical bulkheads, with limber holes at the bottom?

 

No need to glass the thing upside down with holes.

So, let’s assume you need a longitudinal (a big assumption). There are various levels of effort you can go.

You could glass tapes of 1708 to the side of the hull on each side, something like two staggered 6” tapes and a 4” tapes, using epoxy; this would really do a lot to stiffen the boat.

The second way would be to take a rigid foam and make tophats. You’d bond maybe 3 pieces of foam together say 3” wide and radius the edges of two of the pieces creating a glass former and then bond that to each side of the hull and glass it in with 1708 and like a 3” and 2” bonding area on the hull. So, the first piece of glass would be a bit bigger than 3”+3” + 1.5” + 3” + 3” or say 14” and another piece about 12” over that about an inch shorter each edge. This would be stiffer by a great deal than now and the first option.

Bonding a locker base, if that is what you would prefer, is harder to do, and would require marine pvc cores. There are about two methods, again each with varying degree of added strength.

The first method would be to make foam cleats. The foam here should be marine foam, not big box pink. The cleats get shaped with an angle on the bottom about 45 minimum or for 1/2” foam, a 3/4” landing. This foam is bonded to the hull in the perfect location so it is level all around. You bond it with an epoxy putty. After bonding; you apply a 1708 tape to it. The tape would be about 4” wide, but keep it below the top of the cleat. After it all sets up; you template and cut out the marine foam locker base to fit. Then you glass that with db1200 each side or the 1708 if you really want to go nuts or only buy one fabric. Make an epoxy putty and glue it down to the cleats. Bond the top using a nice fillet with a single 4” tape.

If you want it to be even stronger you can add more tape to the bottom and top and I can tell you how, but it gets complicated. You do NOT hole the base to bond it. You use a pre-release method where there is a piece of sacrificial base made no glass with a hole in it and shipping tape on the bottom and you bond a tape about 8” wide over the shipping tape and then pull the sacrificial foam out after curing for a larger bonding area, but it is really major overkill here as the part is not taking the sea alone.

 

Bonding the tophat method is a bit tricky to do perfect. I’ll add, they will be very hard to glass well as the fin roller for the hat side must be rolled one direction which is toward the hull sides and the roller for the hull side only rolls toward the hat. You will have a hard time doing it super well, but it won’t need to be perfect. Thinking it thru, I may build them at 2” wide as much easier; reduce tapes accordingly.

 

The sides of the hull would be like the flanges of an I beam with the horizonal bulkhead acting as a web. I'd lay the glass at 45 degrees and tape it on top only. Do it on both sides of existing forward bulkhead. Consider having an access hole in both pieces for inspection.