[smurphny]

Some pix would help. There's no way to venture any advice on structural elements without some kind of picture or specs. Those temps are great for epoxy work. I wouldn't use fast or slow hardener unless I wanted to speed up the process but that sometimes results in a smoldering can of gelled resin before you can use it all. Working inside, I hope you have a good organic vapor mask. Most bulkheads I've ever seen in 30-40' boats are 3/4" ply.

 

[smurphny]

Forgot the specs guys, apologies:

Boat Make: Laurin Koster
LOA/LOD: 28' / 26'
Displacement: 6600 lbs
Mast: 33' / 160 lbs
Link: LAURIN 26 sailboat specifications and details on sailboatdata.com

Yes, I have a $50 3m paint/organic respirator (with many replacement cartridges & prefilters), goggles, and tyvek suit.

I used MAS Epoxy on a kayak kit years ago and liked it, but we can't get it easily up here, so I was going to go with West System since it's available.

I'll get some recent interior photos posted later today.

The attached line drawing gives the basics, but my my boat was retrofitted with a 2' bowsprit.

Thanks.

That's the respirator I use and have not had any problem. Have never used epoxy other than West System because it has always worked so well. Epoxy, as you probably know, can be nasty. When I forget or am too lazy to dig for the respirator, even for a small job, it can give me a wicked headache. Same with 2 part paints.

I'd probably redo the stringers where they've cut away. They were put there for a reason and it's no big deal to do it now. I'd also use 3/4" ply for bulkheads. It gives you some meat to work with as far as framing openings. Certainly use it if you're going to put in any watertight bulkheads, which might be something to consider. It's not as if a few pounds is going to make much difference.
Nice looking boat. Good luck with the refit.

 

[smurphny]

Think I'd probably find some dense foam like some polyisocyanurate insulation to form the substrate. I'd just shape it and stick it to the hull inner surface with some contact cement. Then you could glass it in immediately. Don't forget to feather the adjoining glass at a 12:1 ratio. If the glass is 1/4" thick, taper back approx. 3". The first glass layer needs to be the biggest pc.

 

[smurphny]

That's a very good way to go but shaping it can be labour intensive. Cutting PVC tube in 1/2 and tacking it in place with hot melt glue is quick & easy, Doesn't weigh anything really and the round shape is easy to glass over. It also holds screws when you fasten a wood ceiling over it - the glass alone is too thin to do it well and foam does nothing.

It doesn't look like the stringers and "ribs" are 1/2r. in the pix. They look somewhat rectangular but it's hard to tell. If they are, PVC tube would work fine if the right size. I thought some pipe insulation foam might also work if they were 1/2round. The size has got to pretty much on the money to make the layup come out matching. That's why I thought some insulation foam would work. It's easy to shape, unlike a styrofoam, but does make quite a dust mess. It would also bend to conform easier than pvc.

 

[smurphny]

The 4 stringers (2 each side) do look rectangular, but up close when ground-out, they are about 2.5" wide x 3/4" thick, and either edge was chamfered at 45 degrees before glassing.

The foam type used on this boat was Divinycell, and appears to only have been used on these stringers and the coach roof. The stringers still in the boat do not appear to have been used for mounting hardware of any type from the factory.

My only internal debate with using foam (and I'd like to), is will it and the tabbing provide enough bite for the screws over the wear and tear of time. The foam would definitely be easier to place and conform to the hull for a professional looking install. The wood will be a bigger challenge.

Relief cuts in PVC (to get it to conform) seems like a tempting compromise, though I may want to pre drill to avoid cracking.

If there are any pieces of hardware screwed into it, I'd glass those spots solid. That would be much stronger and keep water from eventually getting in. Neither foam nor PVC will hold screws with enough strength. Foam has no strength at all to hold a screw. How are the deck-hull screws/bolts? Being open, it's s great time to check them.

 

[smurphny]

So you're saying that tabbed wood is the only way to go for ribs?

There are no deck/hull fasteners, it appears the deck and hull were glassed together at the factory.

If it's only light interior, unstressed items attached to the new parts, the PVC would be great but if you're attaching any stressed exterior hardware like grab rails or bases for blocks, solid glass would be essential. One thing I wish my boat had are some conduits to run wires through rather than just snaking all over the place through the bilge. Wiring, plumbing, water tank(s), and access are things you can customize. Also copper foil for an SSB counterpoise is a lot easier as is a grounding system. All that kind of sub-interior stuff is easy to do with the bare hull and difficult afterward.