Epoxy Estimate

[cat_duh_maran]

I'm thinking of building a 15'-16' flat bottom skiff or punt for fishing protected waters. I'll power it with a 5hp outboard. It will be hard chined and planked with plywood. I'm looking at several designs and havn't chosen one yet but I would want to glass it up to the waterline at least.
I'm trying to estimate the material costs. I can figure out just about everything except the quantity of epoxy I'll need. Raka sells a 3 gallon kit which includes 2 gallons of resin and a half gallon each of fast and slow hardners. Would this be enough to take care of my needs for this boat between the bottom and general gluing and filleting?
Bruce

[Hwyl]

Depends on how thick the cloth is and lots of other factors, but at the very least, you'd need two of those kits.

[TimmS]

With Epoxy it is more critical that you get a good even coat and that both the weave of your cloth gets filled, and that it soaks into the wood at the same time, than the 'amount' used. Lately I have been using MAS low viscosity epoxy for my glass work which does a wonderful job of soaking in and sealing, then I recoat with gegular epoxy before it fully cures to fill the weave of the cloth. 3 gallons sounnds like plenty for your project if you do it in small batches and spread it out thin. Good luck, Timm

[David G]

Partly, too, it'll depend on how experienced you are with epoxy. If you can work clean, and have a good sense of how big a batch to mix in various circumstances so as not to be wasteful, and know how to keep the batch cool while you apply it... you can save a lot of material. But that just comes with experience.

We built a similar size boat - the Goat Island Skiff, by Michael Storer:

http://www.storerboatplans.com/Boatplans.html

We used less than a gallon during construction, and I estimate it'll take less than a gallon to glass the bottom. Keep in mind, this is a very simple build. Not a lot of parts to be stuck together. Glassing the bottom would probably be comparable - unless you pick a much beamier design.


"Estimated amount of glucose used by an adult human brain every day, expressed in M&M's: 250 -- Harpers Index

[Lewisboats]

Using enough to fill the weave you shouldn't need more than 1.5 gals for a simple flat bottomed boat. I am assuming using epoxy on the outside only. Heavier cloth than 6 oz or non 'glass cloth may use more. Drape your cloth and let it sit for a couple of days to get used to the shape...mark corners so you can re-align, then wet the wood, let it tack a bit, lay your cloth and smooth, then squeegee on the first coat to wet the cloth. No white spots. For subsequent filler coats after the first has tacked use a thinly filled mixture with microballoons. This will allow you to sand it easily. When you are done, use a light final coat of unthickened epoxy to seal 100%. Your filler coats should be molasses thickness...maybe chilled molasses depending on the temps you will be working in. Keep the thickened epoxy container in a bath of cold to iced water to prolong working time and use a wide shallow container.

[JimD]

Also, different designers have different methods for ply/epoxy/glass boats and list the epoxy requirements on the bill of materials on their websites. Bateau, for example, tends to call for a lot epoxy and glass. His Indian River Skiff 15 calls for 4.5 gallons while a Glen-L boat of similar dimentions calls for a fraction of that.

[Cuyahoga Chuck]

A basic glass lamination for one square yard of cloth requires as many ounces of epoxy as the weight of the one square yard. For instance, 6 ounces of epoxy for 1 square yard of 6 ounce cloth, etc.
But that leaves the weave exposed. Exterior glass must have the weave buried. To bury the weave usually requires 2 more coats of epoxy which will be somewhat less than the initial coat.

[JimConlin]

Estimate how many pounds of glass you'll use. Glass weights are measured in oz. per square yard (9 ft^2). So, for illustration, 2 layers of 8 oz. glass applied to 50 ft^2 will weigh 2*8*50/9 = 89 oz. = 5-1/2 lbs. You'll use roughly twice that much epoxy, or 11 lbs. Epoxy weighs about 10 lbs. / gal., so you'd need just over a gallon for the glassing.

I'd get the 3-gallon kit. It's useful stuff to have around.

[cat_duh_maran]

I figured on using 6oz glass, filleting every stress point, sanding out and recoating and sanding again before painting to a "work" finish. One design I've looked at is Atkin's Sedge. It's like the boat I want but not quite. Does that make sense? The alterations I'd want are interior only so the hull structure would remain the same. It doesn't appear to be a popular boat so any help is welcome. I'm definately building on a budget but I want something I can be proud of and will last. I don't intend to go cheap on the ply and want the glue/resin to keep up with it.
It's tough when one answer says double it and the other says you'll be fine.
More input please?
Bruce

[Steve Lansdowne]

Epoxy doesn't go bad, so likely as not you'll find another use for any extra you might get for another project/boat later on.

[AstoriaDave]

Get more than you think is adequate. You will probably waste some. And, the stuff keeps going up in price, so it is a good investment. Better than anything else in the financial markets, anyway.

[cat_duh_maran]

Epoxy doesn't go bad, so likely as not you'll find another use for any extra you might get for another project/boat later on.I understand what you're saying and totally agree...except, as I said...this boat is going to be on a strict budget. The goal is to get it done on a set budget. I don't want to cut corners on quality to get the boat done. I don't want to have a half done boat in the shop for two years that I can't afford to look at and my wife is mad at me for having started. I'm not a rich man. I want to build a boat and choose the boat that fits in my budget. Extra epoxy would be nice but only if it's "extra". Buying more than I need isn't extra. It's divorce.
Bruce

[2MeterTroll]

with six OZ cloth use the formula these guys gave and double it.
the cloth depending on weave will eat about the formulas worth of epoxy then you need to figure the extra. add for an extra coat or two for sanding and repainting later on down the road. a bit for filling errors in fitting and gluing up various bits.

Imo this is why there is such disparity between amounts for the boats. some plans have the extra built in and others don't.

[JimD]

Raka sells a 3 gallon kit which includes 2 gallons of resin and a half gallon each of fast and slow hardners. Would this be enough to take care of my needs for this boat between the bottom and general gluing and filleting?


To specifically answer this question, yes, that would be plenty enough for most designs you'll be looking at. But perhaps stay away from www.bateau.com (http://www.bateau.com) designs. The designs that will likely require the least are framed plywood, glued and screwed, and sheathed outside only for a tough skin. And RAKA is my personal favourite epoxy.

[PatCassidy]

Check the product spec sheet for square foot coverage of one gallon of product.

[The Bigfella]

The epoxy will be one of the minor expenses. ...

Incidentally, I used a gallon of it fairing the 14'er the other day - and there's more fairing to do...