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Old 02-01-2010, 08:35   #16
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Join Date: Jan 2006
Location: North Carolina
Boat: 44 footer
Posts: 861

I think your square footage will work out about right, probably on the high side by 20% or so on account of the taper as the keel sweeps up to the stem.

Your math is mostly right, with the exception of how the fiberglass is weighed.

It depends on the glass, but cloth is not named by its weight to the square foot... that is what is throwing in the huge numbers for you.

1708: 17 ounces to the yard, and 3/4 ounces to the square foot.

9 square feet to the yard = 6.75 ounces of mat. 17 + 6.75 = 23.75 ounces to the yard.

2.63 ounces per square foot. X 600 = 1567, or 97 pounds.

Call it 100 pounds per layer, 2 layers = 200 pounds of cloth. 200 pounds of resin...

Weight addition to the hull = 400 pounds.

It'll be more than that, on account that a gallon of resin with microballoons fills the weave and fairs between 80-100 square feet. Call it 7 gallons of extra resin at 9 pounds a gallon, and 5 pounds of microballons. 68, round up to 70lbs.

So... tipping the scales at right around 500 pounds before the bottom paint goes on.

1 Roll of fabric at $650 or so. (Will probably need to pull 10 yards or so off the next one to tab the keel. Depends how much they want for it, 3-4 bucks a yard a lot of places around here.)
30 Gallons of Epoxy. Say 50 bucks mixed a gallon at or around wholesale for West. Find someone with an old drum that will dip some out for you... costs less! $1500
You'll want a half a bag or so of Cabosil, which is around 70 bucks at wholesale for the full one. Pretty easy to find a new home for.
5 gallons of acetone 63...
5lbs of microballons. Not sure on pricing, I'm still working through the last of ten pounds from the fall.

I'd say he'll push 3,000 after the bottom paint is on in materials if he has to buy a grinder, and respirator. Maybe less if he doesn't want a racing bottom, less sandpaper.

Extra info: I dip out resin into 5 gallon buckets. You have to make sure that you get lids with a rubber seal so the cans are air tight. Otherwise if you let them sit, the hardener will get contaminated with water as it pulls the moisture out of the air, it goes cloudy white when you mix it. Then takes twice as long to kick off, into bubble gum. You can cook it out with a heat lamp, but it's best that it never happen. Pour the hardener into smaller cans.

Last post I said to lay the cloth so it overlaps at the hump, forgot to add a warning with that... it's the fastest way, but if you don't microballon it immediately, you'll grind into glass. If you do top sides you'll want to lay 2-3 pieces, then go back and add on top of them butting at the seams as best you can so you are fairing a low spot rather than deciding to grind through half a layer to take down a high.


36 degrees and windy here... need to go fire up a grinder, but brrrr!

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Old 02-01-2010, 08:45   #17
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Oh... as far as thicknesses go, in a hand layup 1708 works out to be just shy of 3/16 for 2 layers. Just shy of 1/4 for 4.

When you build up an inch thick with it, the just shy starts stacking up and you end up with a voice in the back of your head saying "when will it ever end!?!" But then again, boats are crowned anyway so the math says it'll take 16 layers, 22 later you are still dragging a batten across...

Oh... Also, how long will the boat be out of the water prior to the repair? The bilge needs to be dry. Dusty. If she isn't and you grind through the glass to the wood hull on something that isn't coated inside and out she may weep. If you absolutely must stick to your 2 week time table, I had a battle royale with a rudder post last fall that dripped just often enough to bugger up the glass going around it. (Even after the boat was out for 4 months..)

West Systems makes an epoxy that will set up underwater. Its got the viscosity to stop a drip, if you mix it up with a load of cabosil, after blasting a heat gun to the crack long enough for it to be dry. Expensive stuff, but on a plywood sheathed boat it came in handy.

Here's the boat in question: Noel

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Old 02-01-2010, 09:47   #18
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Location: Dover, UK
Boat: Ex liveaboard, now grounded.
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Oh woops! What a mistake to make - only out by a factor of 9 on the weight. Oh boy... Okay thanks, Zach, and apologies to you, r moore, for causing confusion.

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Old 03-01-2010, 07:00   #19
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Steave , the scantlings for foam are only 1 layer 17oz biax with mat both sides. If you use just one layer 1708 you will lose a lot of your load carring cap, the mat sucks up a lot of epoxy. With flared option my 31 will have 810sq ft hulls. Yours should have 15% or better, 950 + or -, 9 to 12 oz 45/45 biax is your best option over ply, silver tip epoxy for easy wet out. Fiberglass supply in WA, or OR.? has the products you need at good prices. I would stroungly advice you to contact Ed before you decided on your fix, no harm no foul.

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