Filleting with Polyester Bonding Paste?

[mishnish]

Hi all,

Recently joined the plastic classic owner society (tm!) with a Vivacity 20 - puchased for the princely sum of £1. Needless to say, this is a total restoration, and to that effect, I have chopped out the interior liner, all the structural top hats (which were too flimsy for my liking) and I am now digging my way down into the stainless steel scrap filled bilge keels, as they were saturated with water and were probably going to come back and haunt me, so out it comes, and lead shot and polyester resin mixed up in 20kg batches (slowly slowly - not keen on big exotherms!) is going back in.

Now I have been planning the new interior, and although I feel always the push to do the right job, I like to consider possible ways to get a quality job for a saving. Here in the UK epoxy costs a fortune. I know I am probably going to go down the route of epoxy/silica/microballoon mix and then overlamming with glass tapes and epoxy to fix in my new interior structure, but I was wondering if anyone had ever tried using polyester bonding paste to do the filleting (with suitable surface prep of course), then overlamming with tapes and epoxy? I would love to know if anyone has had any mileage with this...

Kindest Regards all,
Chris

[Quetzalsailor]

You shouldn't be filleting with polyester bonding paste, unless you're buying some product made for the purpose. Plenty of boats are built with bonding foam or pastes; they're usually bonding substructure or structural grids to a hull and I think, usually the hulls are 'green'. Go online and read Professional BoatBuilder Mag on the subject and look at the adverts. What you can do, as an amateur, is use the pastes/fillers as a way to get a nice smooth transition for tabbing from the hull if the bulkheads or whatever are not well fitted. Boatbuilders usually did not bother.

Loads will not be high in a 20' (or is that meters?) boat so you need not do much better than the original builder. I doubt you'd be filleting for structure in a 20' keelboat, anyway. Think tabbing and think MORE tabbing width than was originally done.

Bear in mind that polyester was used, is used for tabbing wood parts to polyester hulls, but that the bond and the waterproofing effect of the polyester is nowhere near as good as epoxy. So take more care than the original builders to devise structures that will stay dry (examples: no end grain standing in water; no trapping of water next to tabbed wood)

[mitiempo]

Hi Chris
The Vivacity is a cool boat, used to see quite a few around Vancouver and Victoria (Canada).
My suggestion is to use a closed cell foam cut in a trapezoid shape, wider against the hull and narrower against the bulkheads. If you're careful with the cutting, and it's easy to cut foam with a razor knife, you won't have to fillet much. The foam will protect against hard spots and let the glass tabbing take the load evenly. The angle you cut will need very little or no filleting and therefore less epoxy. Make sure the foam is closed cell so it doesn't suck resin and leave the cloth resin starved. Good luck.

[stone]

Exactly what I did . I removed and replaced everyone of my bulkheads and did all of my fillets with a cabosil/microballon mix in polyester resin. I did all of my glassing with Vinylester resin and three layers of 1708 .

[Zach]

One thing about foam fillets... I've used some foam weather stripping to keep from generating hard spots around bulkheads. A lot of weather stripping foam is not closed cell. I was displeased about this, even though I epoxy coated the endgrain of all the plywood it would be touching... When and if a deck leak ever saturates it, there would be standing water against wood.

So... make sure the foam you use is closed cell stuff so it won't be moist...

Zach