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Old 05-05-2009
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Specific Bulkhead replacement Qs

Okay, although I have done this before, what are your guys advice on some bulkhead replacement questions.

I will be using 3/4 inch Mahogany plywood. I will be putting closed cell foam between the bulkhead and hull and will angle the edges of it for a slow radius for the cloth at the corners. I will be sealing the ends of the plywood with epoxy prior to installing.

My Questions are:

1) What weight fiberglass cloth to use,6 oz or 10 oz?

2) How many layers of cloth; I was thinking 3.

3) Should I brush some epoxy onto the plywood face to wet it a bit where the cloth will be laid down?

4) Should I put the cloth on and then brush on the epoxy or should I wet the cloth in the epoxy tray and tranfer it? Any tricks to avoid major messes here?

5) If I am putting on 3 layers, can I just go one after another, or should I wait for it to set up a bit?

6) will epoxy adhere to polyester resin? Looks like the old bulkheads were put in with polyester. I will grind off as much as humanly possible, but do not want to risk grinding gouges in the hull, so there may be some polyester still on the hull.

Any other tricks/tips are appreciated, as I said I have done this before, but better to plan thoroughly now rather than regret poor decisions later.

If it makes a difference, the boat is a Shark 24 from 1961.
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Old 05-05-2009
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Quote:
Originally Posted by Finallybuyingaboat View Post
Okay, although I have done this before, what are your guys advice on some bulkhead replacement questions.

I will be using 3/4 inch Mahogany plywood. I will be putting closed cell foam between the bulkhead and hull and will angle the edges of it for a slow radius for the cloth at the corners. I will be sealing the ends of the plywood with epoxy prior to installing.

My Questions are:

1) What weight fiberglass cloth to use,6 oz or 10 oz?

2) How many layers of cloth; I was thinking 3.
At least three of 10 oz. or four of 6 oz.

Quote:
3) Should I brush some epoxy onto the plywood face to wet it a bit where the cloth will be laid down?
Yes

Quote:
4) Should I put the cloth on and then brush on the epoxy or should I wet the cloth in the epoxy tray and tranfer it? Any tricks to avoid major messes here?
You can do it either way... the trick is not to oversaturate the cloth. You want just enough resin to wet out the cloth, but no more... I would recommend putting the cloth on the wetted out bulkhead, and then using a foam roller to add epoxy and help wet out the cloth. Rollers work better than brushes IMHO.

Quote:
5) If I am putting on 3 layers, can I just go one after another, or should I wait for it to set up a bit?
It might be wise to wait a bit between layers, since doing all the layers at the same time might cause them to sag. This is especially true if you're using too much resin to wet the cloth out.

Quote:
6) will epoxy adhere to polyester resin? Looks like the old bulkheads were put in with polyester. I will grind off as much as humanly possible, but do not want to risk grinding gouges in the hull, so there may be some polyester still on the hull.
Epoxy will stick to pretty much anything... that's the reason it is used for high-strength structural repairs, and polyester/vinylester resins generally aren't.

Quote:
Any other tricks/tips are appreciated, as I said I have done this before, but better to plan thoroughly now rather than regret poor decisions later.

If it makes a difference, the boat is a Shark 24 from 1961.
Get and wear a full tyvek bunny suit with hood, gloves and use a good full-face respirator, like a 3M 6000 Series, with a plastic cover for the faceshield. This will help prevent you from turning into a sticky mess, and help keep you from itching from the ground fiberglass, or reacting to the epoxy.



A good source for epoxy is Progressive Epoxy Polymers, in NH.
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Last edited by sailingdog; 05-05-2009 at 02:17 PM.
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Old 05-05-2009
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If you haven't figured this one out already, a cold shower is best after a day of grinding glass. It closes up the pores in your skin so the glass dust washes away = no itching at all.

Citrus & pumice hand cleaner works pretty well for cleanup too, not sure why.

One option to wet out the cloth is to fold up each piece and put it in a ziploc freezer bag. You can add a precise amount of resin, close the bag, and roll it with a paint roller to wet it out.

To add to SD's comments about not doing the layup all at once: doing so can also produce too much heat which will give you bubbles in the laminate.

Are you planning on doing the glassing with the bulkhead laying flat on a table and then moving it into the boat ?
If so, Interlux Epiglass HT9000 is a great resin for this - it's runny enough to penetrate the wood, wets out really well and (if you want to leave the b/h bright) it cures without an amber tint.
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Quote:
Originally Posted by sailingdog View Post
You can do it either way... the trick is not to oversaturate the cloth. You want just enough resin to wet out the cloth, but no more...
just to emphasize this point a bit. as counter intuitive as it may seem, glass cloth is stronger with just enough resin to saturate, then with a thick layer of resin.
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The glass also stays in place better with less resin..and sags less... All excess resin does is add weight, without really contributing to the strength of the layup.

Quote:
Originally Posted by rrgane View Post
just to emphasize this point a bit. as counter intuitive as it may seem, glass cloth is stronger with just enough resin to saturate, then with a thick layer of resin.
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Thanks for the responses everyone.

Looks like I am just going to use Marine grade plywood. I phoned the place that "sells" the mahogany plywood, guy on the phone said that they do sell it, and to come to their outlet. Drove 45 minutes, and it turns out they sell it, but do not stock it! 6 weeks special order item! Dude couldn't have mentioned that on the phone? MORON!

Anyway, I hope to take some pictures as I go through this process and post them once done.
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Oh yeah, for the foam between the hull and bulkhead, is it better to glue it to the bulkhead or to the hull when installing? We all know that when old boats were built, the put the bulkheads in with the decks off; putting bulkheads in once the deck is on can be a bit of a tight squeeze and 3/4 inch plywood does not really bend all that well.
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my simple addition is when you have all the glass wetted out hit it with a spreader to squeegee out the extra epoxy. if you want a smoother finish put a plastic drop cloth on it then squeegee with the spreader, when cured peel the drop cloth off
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It doesn't have to be glued to either... but gluing it to the hull makes installing the bulkhead simpler, since it gives you a really good idea when the bulkhead is lined up properly...

BTW, you could always cut the bulkhead in half, and epoxy the halves back together once you got it in the boat... One of my friends did essentially that... the area adjacent to the cut was routed down to 3/8" thick, for 2" on either side of the cut and a piece of 3/8" plywood was scarfed in with thickened epoxy and a a couple layers of fiberglass on either side when the bulkhead was reassembled.

Quote:
Originally Posted by Finallybuyingaboat View Post
Oh yeah, for the foam between the hull and bulkhead, is it better to glue it to the bulkhead or to the hull when installing? We all know that when old boats were built, the put the bulkheads in with the decks off; putting bulkheads in once the deck is on can be a bit of a tight squeeze and 3/4 inch plywood does not really bend all that well.
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You know what the first rule of sailing is? ...Love. You can learn all the math in the 'verse, but you take
a boat to the sea you don't love, she'll shake you off just as sure as the turning of the worlds. Love keeps
her going when she oughta fall down, tells you she's hurting 'fore she keens. Makes her a home.

—Cpt. Mal Reynolds, Serenity (edited)

If you're new to the Sailnet Forums... please read this
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Last edited by sailingdog; 05-05-2009 at 02:36 PM.
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