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Re: Epoxy: Gummy epoxy
By:JohnAbercrombie
Date: 9/16/2014, 12:18 pm
In Response To: Re: Epoxy: Gummy epoxy (aikijay)

Jay-
I think your questions were directed toward folks who have more experience with foam builkheads than I do, but a couple of thoughts:

I was thinking the foam would be more lightweight and flexible in the event of some crash or compression of the hull on a rock. (Although it is unlikely since I'll be using it in a lake!)

The bulkhead 'no hard spot' aka flexibility argument is certainly correct if the hull is flexible. I saw one example of a very flexy glass-kevlar hull with a fracture line (not all the way through, but the resin and possibly some of the glass were fractured) immediately forward of the aft bulkhead- the result of sliding over a rock, apparently . (Boat was from a well-known boatbuilder). With a very stiff wood-core glass/epoxy boat, I think the hull is so stiff that a flexible bulkhead isn't necessary. I prefer a glass bulkheads, bonded with a good sized fillet on both sides. I don't worry about kicking the forward bulkhead in a re-entry or jamming gear against bulkheads.
I haven't done a lot of testing, but I don't think there's much weight difference between bulkhead materials. Glass bulkheads can be pretty thin and light and do their job. I also like the translucent nature of glass bulkheads- it helps a little bit to light up dark corners.


How do you determine the exact shape of the bulkhead to fit water tight, if the hull and deck are assembled already?

I use cardboard or a combination of thin ply/masonite and card and fit by trial and error. I start with the shape of the form near the bulkhead location and hot glue small pieces of card around the perimeter while holding the 'pattern' in place. A short stick screwed to the middle of the 'pattern' gives something to hold. Fit, trim, etc. - it takes 15 minutes or so;perhaps longer for the first one you do. A good light on 'the other side' of the bulkhead will reveal the gaps. The epoxy fillet will take care of small problems with the fit.

A thick (I'm assuming you are using something pretty thick..) foam bulkhead may need some taper to fit at both faces. Foam will also compress and fill gaps, so I'd do some experimenting to determine how much oversize you need to cut the foam. I know that the Mariner foam bulkheads they used in the Coasters had a 'slot' cut around the edge, in the middle of the foam thickness - I think the idea was to provide an area for sealant, and possibly a bit more 'spring'. I'd be careful cutting that.

I'd worry about silicone contamination from the sealant, so a vigorous cleanup would be my recommendation. I think some builders use Lexcel (sp?) instead of silicone.

Messages In This Thread

Epoxy: Gummy epoxy
aikijay -- 9/8/2014, 12:18 pm
Re: Epoxy: Gummy epoxy
howard -- 9/8/2014, 10:02 pm
Re: Epoxy: Gummy epoxy
aikijay -- 9/8/2014, 10:46 pm
Re: Epoxy: Gummy epoxy
Allan -- 9/8/2014, 11:11 pm
Re: Epoxy: Gummy epoxy
Jay Stallman -- 9/8/2014, 11:40 pm
Re: Epoxy: Gummy epoxy
Allan -- 9/9/2014, 12:16 am
Re: Epoxy: Gummy epoxy
howard -- 9/9/2014, 7:14 am
Re: Epoxy: Gummy epoxy *PIC*
Etienne Muller -- 9/9/2014, 7:15 am
Re: Epoxy: Gummy epoxy
Rob Macks/Laughing Loon CC&K -- 9/9/2014, 7:39 am
Re: Epoxy: Gummy epoxy
Robert Horstmann -- 9/9/2014, 9:03 am
Re: Epoxy: Gummy epoxy
Jay Stallman -- 9/9/2014, 11:43 am
Re: Epoxy: Gummy epoxy
Rob Macks/Laughing Loon CC&K -- 9/9/2014, 12:34 pm
Re: Epoxy: Gummy epoxy
Etienne Muller -- 9/12/2014, 3:45 am
Re: Epoxy: Gummy epoxy
Jay Stallman -- 9/12/2014, 12:47 pm
Re: Epoxy: Gummy epoxy
Etienne Muller -- 9/12/2014, 2:27 pm
Re: Epoxy: Gummy epoxy
Jay Stallman -- 9/12/2014, 4:09 pm
Re: Epoxy: Gummy epoxy
Etienne Muller -- 9/12/2014, 4:45 pm
Re: Epoxy: Gummy epoxy
Bill Hamm -- 9/12/2014, 6:40 pm
Re: Epoxy: Gummy epoxy
JohnAbercrombie -- 9/12/2014, 4:55 pm
Re: Epoxy: Gummy epoxy
Jay Stallman -- 9/15/2014, 5:55 pm
Re: Epoxy: Gummy epoxy
JohnAbercrombie -- 9/15/2014, 6:45 pm
Re: Epoxy: Gummy epoxy
Jay Stallman -- 9/15/2014, 8:53 pm
Re: Epoxy: Gummy epoxy
JohnAbercrombie -- 9/15/2014, 10:14 pm
Re: Epoxy: Gummy epoxy
aikijay -- 9/16/2014, 7:35 am
Re: Epoxy: Gummy epoxy
JohnAbercrombie -- 9/16/2014, 12:18 pm
Re: Epoxy: Gummy epoxy
Jay Stallman -- 9/16/2014, 1:25 pm
Re: Epoxy: Gummy epoxy
george jung -- 9/16/2014, 2:53 pm
Re: Epoxy: Gummy epoxy
JohnAbercrombie -- 9/16/2014, 4:01 pm
Re: Epoxy: Gummy epoxy
JohnAbercrombie -- 9/16/2014, 3:59 pm
Re: Epoxy: Gummy epoxy
Jay Stallman -- 9/16/2014, 5:24 pm
Re: Epoxy: Gummy epoxy
JohnAbercrombie -- 9/16/2014, 9:00 pm
Re: Epoxy: Gummy epoxy
JohnAbercrombie -- 9/15/2014, 6:50 pm
Re: Epoxy: Gummy epoxy
Jay Stallman -- 9/15/2014, 8:48 pm
Re: Epoxy: Gummy epoxy
howard -- 9/15/2014, 9:37 pm
Re: Epoxy: Gummy epoxy
JohnAbercrombie -- 9/15/2014, 10:19 pm
Re: Epoxy: Gummy epoxy
Allan -- 9/15/2014, 11:04 pm
Re: Epoxy: Gummy epoxy
Jay Stallman -- 9/16/2014, 12:07 am
Re: Epoxy: Gummy epoxy
Allan -- 9/16/2014, 12:45 am
Re: Epoxy: Gummy epoxy
Allan -- 9/16/2014, 12:53 am
Re: Epoxy: Gummy epoxy
JohnAbercrombie -- 9/12/2014, 4:42 pm
Re: Epoxy: Gummy epoxy
Bill Hamm -- 9/10/2014, 12:49 am