Proper way to tab bulkheads on a fiberglass boat

Thanks par, a very helpful post. Two questions though:

What should be used for the fillet? Are we talking insulation foam or real marine foam? If making a fillet, is epoxy filled with microballoons soft enough or should some other filler be used?

I have never worked with bias before. What would be an adequate layup for a 25', 4000# boat like mine?

 

Real foam is required, as the whole point of that extra foam is to create a sturdy cushion to keep the bulkhead from digging into the hull. Alternatively, you can float the bulkhead up away from the hull so it doesn't touch the hull in any point instead of using the foam.

Epoxy should be more than just microballoons. Microballoons are good for fairing and for non-structural bulkheads (walls - not stiffeners or load carriers). Because you need so much silica anyway when doing a fillet, that mix is good for non-structural stuff.

For a real bulkhead, it has to be a structural fillet/cove, which means you need chopped glass fibers in it and of course, to keep it from sagging, you will have a fair amount of colloidal silica as well, which is strong, but brittle by itself.

I don't know the loads, so PAR will have to step in, but using biaxial tape is a good way to secure a bulkhead (in addition to your proper fillet).

 

Cat, you've come a long way my friend. Peter, what he said is right on. You'll want at least a 5 pound foam, preferably heavier. If using Q-cells or other light weight material, you'll want a moderately high percentage of silica and/or milled fibers to make a good fillet mixture. I use milled fibers on all 'glass boat bonds, typically mixed with silica to control viscosity. Milled fibers seems to work better than anything else and is commonly called liquid 'glass when mixed, for this reason. For a 2 ton boat bulkhead, you'll want biax, the laminate schedule is dependent on what and where.

 

Slight tangent...

I have just found this thread and most of it applies to my situation.

I have a glass 16ft VistaCraft with an outboard, that is a 36 yr old hull and has over time had various average quality "glass" jobs done on the interior of the hull to seal and strengthen it. One of those, someone used car bog to add a cap to the wooden keel edge that came up into the boat [thin bit of wood] and when I belted the bog off a few days ago it all came off in big chunks in my hand, and the inside of it was sodden with mud, sand, water. The keel wood was then exposed, i touched that and it moved, pulled it, and I was holding it... about 18" long bit of wood not ply, wet, and rotten.

It has been suggested by a Marine survey bloke, that I grind out all the edges of the boat interior, back to solid glass, cove them all, and glass them all back up to give the whole hull strength. Which I am launching into. Starting with this keel area... grinding it away to expose what I might find. Someone else told me that the metal keel strip has been added to the boat keel and the screws they used might be too long, water runs up them, and gets into the keel wood. His solution, remove them, and cut out anything wet, replace with thinned epoxy to fill the void. I'm not confident in that, both in that it sound like a hell job, and like ill be adding a liquid UP wards, unless i flip the boat. Never done that before either !

Bulkheads or only one should be added in suggested the marine survey guy, just aft of the centre console position and he mentioned the gap with a fillet but didn't give much advice there, so your comments helped alot. And thanks Sam on the WR ideas as I will be going there when it comes to glassing that in.

I happen to live about a km from the largest Fibreglass supplier in NZ. So I went there and spoke to them for a few hours today. As my knowledge of glass is or was z e r o. They were able to call a boatbuilder staff member of theirs, but its the boat show this week and he is there "talking". He will come and visit my boat next week to determine if we are going to be using poly or epoxy as I want this job done right and perfectly, and I am going to be doing it and have plenty of time before I NEED to be landing kingfish over the summer approaching.

Phase 1 for me is the removal of everything crappy out of the hull corners anyway, and that was kicked off with a 2 hour covered head to foot in a moon suit, two pairs of latex gloves and a 3M 6200 respirator which worked a charm. I wear glasses though, and they got covered in glass dust. As goggles would be a bit tricky.

Many thanks
Guy