First off, before you do this... go ahead and get some whole sale
accounts lined up. You are talking about 900 bucks easy worth of glass, probably close to double that in resin if you go name brand. A 60 dollar case of gloves, 2 dozen 4 dollar paint
rollers, 25 2 dollar 5 quart mixing buckets, 1 good full face respirator (pushing 160...) 150 bucks in sand paper, 5 or 6 white suits, 5 gallons easy of acetone...
Forget about using mat (you'll just hate life...) or doing a 1/4 inch layup
out of 6 ounce finish cloth.
For hand laid glass, you are going to have 50% of the weight of the layup
in the glass... 50% in resin. As everybody else has stated... you want to use epoxy.
1/4 inch is overkill in all aspects, but the fastest and strongest layup for the money
will result from using biaxial glass. 17 ounces per yard, with 3/4 ounce per square foot of mat stitched to the back. This is pretty much the industry standard called "1708" it is strong enough to tab in bulkheads, and do whatever you want it to... but not such huge bundles of glass that you can't get a fair surface over it for paint
, like roving.
2 layers = 3/16th. 4 layers = 1/4. I think 2 layers is a gracious plenty for the under belly of a plywood
boat, particularly one that has been sheathed since the 70's to no ill effect.
The last roll I bought was just over 600 dollars, 220lbs of the stuff including tax.
You could go without the mat backing to save weight and resin, but its not as readily available. You really want the mat on the first layer to get better adhesion, but then again with epoxy it isn't "really necessary."
What you will need to do, is remove all the bottom paint
. Down to the glass. For speed sand blasting is the fastest. Failing that, get a 7 or 8 inch grinder and a box of norton hard sanding
discs around 36 grit. Or if you are loaded, spring for the extra cash and get your grubby hands on some Norton Blue Mag 7 inch paper in around the same grit.
Don't ask questions, just go buy one... It's a Makita 9227 Circular Polisher that you want. The speed is adjustable so you can dial them back if you run into bottom paint
that wants to melt and turn to bubble gum... and they are light weight for working over head
. You will need a hard black plastic backing pads for the Norton hard paper discs, or a foam backing pad for sticky discs if you go with the Blue Mag. Don't waste your time with hook and loop pads, 5 inch orbital sanders... you have a lot of boat to do, and 2 weeks to do it in. While you can hold 20 pound grinder overhead for 2 days straight, it sucks, i've done it... you can't get a smooth finish with a 7,000 rpm
monster that has an on off switch when you go to fair her. Save yourself the trouble.
Once you have the bottom paint free, get a sharp sharp sharp set of scissors. I have a pair of Gingher pinking shears that make life easy... around 30 bucks, or you can spring for the hundred and something ones that are made for cutting glass.
Once you have your scissors, build a work bench and a roller so you can slide a piece of pipe through the roll and unroll the fabric
without it dragging in the dirt.
Walk down the boat and measure off the pieces you need. Roughly... Do not try to wrap the underside of the boat at her ends if she tapers, as you won't be able to get the glass to curve forward. Looking from the top it will do this ///// as you lay your pieces to the underside. Not a bad thing, but where she starts to splay out, you get a wrinkle and then have to fight gravity to go up the other side. Sucks!
The glory of fiberglass, is that for all intents once you surpass the width of the bevel needed to attach new material it quits caring that it's not one continious piece. Fossilized snot is amazing stuff, but steel
Anyway... you want to build thickness and stagger the seams. So... the easiest way to do that is to cut a piece that is 25 inches wide, and drapes from the waterline to the bottom of the keel
. Then you cut the next 50 inches wide, and let it overlap the full 25 inches... and the next 50 inch peice butts right up against the hump.
Why run up and down instead of side to side? If you are doing this overhead, there is a trick...
First, you'll want a plywood table with a piece of polyethelene sheet stapled over it. Take a 5 quart mixing bucket with lines on it so you can mix by volume. Mix your resin out of 5 gallon drums filled about half full so they are easy to pour. Now, take the cheapest paint roller frame and candy stripe 1/4 inch nap roller cover and pour the resin onto the cloth, rolling it around. Once wet out, roll it up on a PVC pipe long enough to extend out each side about a foot. Walk the roll over to the boat with paint roller in hand, roll resin onto the boat hull where the cloth is going to go.
Have a friend on the other side of the PVC pipe, grab a big plastic squeedgee, unroll the first 6 or 8 inches, push the air out of it. Unroll about a foot, work the air out from under it... Then ditch the pipe (carefully to keep it off the ground.) Have one guy work the air out and get it all stuck down, then roll it with an air roller while the other guy wets out the next piece. Get the aluminum
air rollers, the plastic ones are shot the first time the resin kicks on them. Aluminum
you can burn them off with a propane
While your time window is still there and the glass is still green where you started... mix up a few batches of microballoons and a cabosil. It should spread about like heavy whipped cream, go back and coat your seams and fill in the weave of the cloth.
Keep on going... When you get done put in a big honking tab that goes 6 inches or a foot up each side of the keel and make this stretch your 1/4 inch thick so if you want to ground out... there is a lot there before you get to wood.
After your microballons set up, grab an bunch of 7 inch soft sanding
pads for stick on sand paper and walk down the hull with 60 grit. If you sand up and down rather than walking left to right with the sander you won't put any scars that won't fair out with a screed... A screed is a piece of sheet metal with a straight flat edge. Go to the hardware
store and get a 25 or so inch sheet rock taping knife and use that to spread the ballons on nice and thin. You drag this one up and down and let it feather out the low spots.
2 guys should be able to grind the bottom in 2 days. Each ama should take about a day to glass and microballoon. If you can wait until the temperature will let you use a tropical hardener you will be rewarded when you go to microballon her, and when you get to the sunny side of the boat you'll have as much working time as you need.
If you can beg an air compressor
... its a sweet thing to be able to blow the glass dust off every half hour or so. Also, when grinding a lot overhead, they making cheap
cotton spray socks for painting cars... it'll keep most of the dust out of your scalp and ears. Wear earplugs... grinders are in the territory of permanant hearing damage!
Dang, I think I just wrote you a book... but in any case, have fun with it.