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Old 12-10-2017, 09:40   #1
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Boat: Tartan 34C
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Overlapping glass sheet joints on deck recore

I am working at a snails pace to recore my Tartan 34C decks. I have a general question which I did a google search and other searches for but not sure I found a direct answer.

How do I go about overlapping joints of the glass? What is proper?

I can't really cut the whole deck area template using my sheets of 1708 so how do I go about lapping the joints when wetting out?

Do I just butt the 1708 sheets up against each other?
Do I overlap them so that in the end, those joints end up being a bit like a ridge and then sand it down?
Tartan 34C #177 "Nova Luna"
Tartan 27 Yawl "Destinada" (SOLD)
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Old 12-10-2017, 11:04   #2
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Re: Overlapping glass sheet joints on deck recore

Assuming at least two layers, you can butt the joints. Just make sure the next layer overlaps the previous layers joint. If only one layer, you could use a thinner cloth to create an equally thick 2 layer layup. If you do end up overlapping 1708 with one layer you might want to use thickened epoxy along the under layers edge to avoid a void.

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Old 13-10-2017, 06:19   #3
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Re: Overlapping glass sheet joints on deck recore

If you have to be on the deck while you are working, make sure your weight doesn't bow anything down. Foredecks are bad about that in that if you work from the bow back and sit on it long enough for the first glass you put down to kick, it'll put a low spot in the bow. Staging is good the wider expanse you have to work.

Buy two 6 inch air rollers, a 3 inch roller, and a 1/4 inch detail roller. Get a gallon bucket with a good lid, fill it with acetone and drop your tools in at least every half hour. Get an acetone squeeze bottle so you can shoot some through the shaft of the roller. I keep an acid brush and a 2 inch chip brush in mine...

I like to start on the side decks and work uphill. Any excess resin or spills doesn't run onto core that that has not yet been fiberglassed. I normally start with a two foot piece on the first piece of the first layer, and put a sharpie mark on each of the ends of the first layer so you can see through the glass work where your high spots and humps should be when you are fairing. It is easier to work the first piece in if it is small so you don't end up making a high spot into the existing deck. Once the cloth is wet out it is tough to peel it back up and move it if you notice something...

If you are working with epoxy, you can put the first layer mat down, and the top layer mat up... not as pretty to look at and fuzzy to work with... but if you have high spots in the second layer, grind down till you see the biax through the mat and you haven't lost anything. Grinding through the biax sort of defeats the purpose of using it. Polyester you need to be mat down against core/biax for a good bond.

Where you stop for the day, you can either run a few layers of masking tape over the core while it is still dry and clean up with rags and acetone prior to pulling the tape for a clean joint, or use peel ply. I like to do two of cloth at a time layers, and leave an area 6-8 inches wide joints rather than 3-4 so I have enough room to grind/clean up yesterdays work on the first layer of glass so the lap joint everyday is not a high spot. I normally grind over yesterdays work so that area is prepped so when I reach the end of todays glass work any extra resin in the bucket can get mixed with filler and troweled. If your butt joints are 6-8 inches apart you can use a foot long sheet rock trowel and go high spot to high spot. 3 inches apart and they are humps that need a lot more grinding.

Grinding is probably a mis-nomer, as you can do a fair bit more damage with a mini-grinder than help... Clean up any nibs that would tear a soft sanding pad with it... then switch over to something like a porter cable 7346 6 inch sander with some 40-60 grit on it. Bigger areas a Makita 9227c... I grind up to the joint from yesterdays work and don't try to float it out... Otherwise tomorrow the new work will be a high spot too.

If you work in 4 to 6 foot lengths +/- you can cut off the roll the maximum width you need and trim on the boat with a rotary cutter to get close to the size you need before dialing in with fiberglass shears. It is easier to keep the cloth together if you cut it long ways from the roll so the stitches stay on the long direction. You can damn near wrap 1708 around a basketball if you do it the other direction.

Cloth shrinks for some reason when you test fit it, roll it up, and put it away... So cut things an inch or two longer than they need to be and you will account for the shrinkage. Something about holding onto things that run on the X-bias means pulling it off the roll lengthens it a bit. Bigger the overlap you give yourself, the less this matters unless the side decks have a lot of taper somewhere.

Working 4 to 6 foot lengths for side decks and such means that you get roughly a quart to do two layers, as you are laying down roughly a yard. Weigh your cloth, then mix the same number of ounces as you need, plus 2-3 ounces per square foot of core you have.

I like to lay the layers I'm working on down dry, and keep some weight handy to keep them from blowing around. With 4-6 foot lengths you can fold back onto its self, wet the core, and the back of the mat, then wet the top a little juicy, air roll the first layer and wet the back of the second and fold down into place. I normally use a 3/8's nap paint roller to wet out... and do the entire length of the side decks in one shot. Which is more expensive in that it costs some resin, but if you use tropical hardener it lasts an hour or so... and if you are to the very end of the bucket of resin and have a dry spot you can smush down a bit on the roller and normally get what you need without getting off the staging.

Keep some old t-shirts and rags handy, as you want to work relatively dry... Once the glass wets outclear, no puddles as the glass can float off the resin... and any resin puddles on the top of the cloth are for the most part high spots and they sand at a harder rate than any putty, so they have a tendency to stay high spots unless you deliberately work them down until you see the weave.

Once the resin tacks up a bit on the area you worked, you can roll a little excess resin over it to fill any weave. If you end up working biax up, mat down, sometimes it is worth a little extra time to fill the weave before you leave for the day. You have 5 hours before the amine blush kicks in with epoxy to work inside the chemical bond window... So working clean, and pulling a very tight putty pull just enough to fill the weave but not change the shape can drastically reduce the amount of time you need to spend sanding the next day to get rid of shiny spots.

6 ounce resin mixes for puttying work pretty well in hot weather, as you don't want to try to fill with putty that is kicking off.

Good luck with the job!

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Old 13-10-2017, 16:45   #4
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Re: Overlapping glass sheet joints on deck recore

I had a yard and have done many decks and repairs. You need at least a 3" overlap, more is better. When doing several layers, I make at least one a 2.0 rsm. It holds more resin. You need a lot of resin in the build. It's better to have a little too much resin than too little. Without enough overlap, you get cracks at butt joints if there is any flexing at all in the deck.
I use West System's high density fill (404) for voids and sometimes in the first and last layer. It also gives an increased bonding to the resin.
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