How much epoxy?

I'm restoring a 17x54 framed boat. Maybe a Don Hill kit(?). I'm planning on glassing with 6 oz. Cloth on the sides and 20 oz. cloth on the bottom. I will either paint or oil the inside. What I'm trying to figure out is how much epoxy I'll need.

I'm interested in what brands people prefer and where the best sources are too. Brad Dimock's blog has me interested in Resin Research, but I'd like to hear other opinions too.

Thanks

Jim aka Rojo

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Permalink Reply by Terry E Walsh on May 2, 2013 at 8:25pm
If you use west systems epoxy you should only need one gallon resin and one quart hardener, that should do it,or it will be really close.You might need more though depending on how thick you put it on.
Permalink Reply by tungsten on May 3, 2013 at 5:08am

I don't think you can go wrong with any of the epoxys that are available.You can calculate how much it  takes to wet the cloth,the unknown is how much the bare wood will soak up.

Permalink Reply by Rojo on May 3, 2013 at 7:54am

Thanks Tungsten. If I thought before I asked, I probably could have figured out there is a formula.

For future reference, West System has a page that explains the formula. Here is the link: http://www.westsystem.com/ss/estimating-epoxy-amounts/

I'll need to sharpen up the 'ole pencil and work up some math.

 

Permalink Reply by Terry E Walsh on May 3, 2013 at 8:55am
Man I had no idea West systems had that information, that's awsome! I was just speaking from my experience, I used a little more then one gallon doing my sides and bottom. Thanks for sharing that page T.
Permalink Reply by chris towles on May 3, 2013 at 10:07am
a gallon will not get you there.

For a hand layup you will want a 50/50 resin to cloth ratio. Get your pieces precut, then weigh them on a kitchen scale and you will need need that much resin. I am building a foam stitch and glue 17x54. I just laid up the side panels the other day. One full layer of 9 oz glass on a side panel weighs approx 2.5 lbs.. Times 2 panels: So you need about 5 pounds of mixed resin to get there. The 20 ounce glass will take 2x the resin plus a little, and you are talking a surface area probably 1.6-1.7 times as big as a side panel. I could easily see you using 18 lbs mixed resin on the bottom. That's a good bit of epoxy. 23-25 lbs (fully mixed resin plus hardener) worth to get there. Epoxy is approx 9 lbs per gallon depending on manufacturer. Three gallons would get you there with plenty to spare to fix things that will inevitable get broken, you may be able to save money by getting 2.5 somehow, but you get better price breaks when you buy in even amounts. Alot of the modern epoxies are 2:1, so 3 gallon kit is standard. 2 gallons resin, 1 gallon hardener. also Fwiw, on my 16x48 with 7 oz on the sides, 18oz biax on the bottom, and some extra resin for small bonding jobs I used around 3 gallons.

As per manufacturer, I have used west in the past. It is pricey and brittle. I have sworn off the stuff now for better cheaper alternatives. I am using resin research 2040 on this boat. I've seen brads blog and the tests don't lie. I spoke at length with Greg loehr and he is a super knowledgable guy, really nice, funny...the kind of guy you want to give your business to. He's very prompt answering questions and sofar I have been really happy with the service and the product. 2040 is super flexible. Totally different animal than any other epoxy I have worked with prior. When the cups kick off, you can almost peel the kicked epoxy off the cup in one piece. West is brittle and cracks into a 100 tiny pieces if you do that. The resin research stuff is way more pliable and stays together. It's also very reasonably priced and the cost on the website for kits includes shipping. They ship from either side of the country too. Depending on where you live, When you factor that in, it may be the cheapest epoxy out there. Raka is slightly cheaper but once you pay to ship it, it probably ends up being more expensive. Probably depends on where you live and how much you buy. I do know that shipping was really expensive from raka for the 4-5 rolls of fabric I ordered, cost about $100 from fl to Wyoming. Sofar I have been happy with my rRNA resin and ill probably continue to use it in the future.

That's a nice lookin boat there. Careful with that orbital sander. I like a block myself, orbitals leave wierd marks and can go too deep real easy. Get that top stuff off and oil the crap out of that thing. Don't cover that old beautiful wood up with paint. Oil will make that glow, smell good, and people at the boat ramp will come running to look at your beautiful boat.
Permalink Reply by Richard Elder on May 3, 2013 at 12:19pm

Hi Chris,

If the WEST resin is "cracking into 100 tiny pieces" you must have drastically missed the ratio of catalyst to base resin when you mixed it.  I say that based upon having used hundreds of gallons on many projects over the years, including a 40,000# sailboat that didn't have a single bolt or screw used in its construction.  Sounds to me like you are talking about polyester resin.

Resins that are highly flexible like you describe are not suited to structural applications where they are used in matrix with stiff material like fiberglass, to say nothing of kevlar or carbon. However for a framed drift boat the structural strength comes from the frames and plywood, held together by screws and bolts.  For this application the resin is a waterproof coating and wood preservative, and a more flexible resin is appropriate, although the yield characteristics of WEST are perfectly suitable as well.  

Permalink Reply by Rojo on May 3, 2013 at 12:33pm

Oil on the interior is the plan (at least the plan today). I was relatively gentle with the sander. The boat already has a lot of "character" so some funny looking swirls won't make too much difference either way. She's not going to look like some of the beauties I saw at the Wooden Boat Festival last weekend.

Thanks for the primer on how to figure out how much epoxy to use. Your thumbnail of 3 gallons lines up with the math I worked out. If I can figure out how to use paypal, I'm going to order the epoxy from RR today. I need to figure out a cloth source too. I was looking at Raka the other day.

Permalink Reply by chris towles on May 3, 2013 at 4:31pm
I've used west system for fiber glassing since the late 90's. over the years the only resin that ever was messed up was when I tried to measure using pumps instead of measuring by weight. I ran out of hardener mid layup and had to run across town to borrow some that had a pump, and i didnt double check on the scale. few hours of scraping and acetone later and i learned my lesson.I always measure resin by weight usually to the exact ratioWest system is by nature a fairly brittle resin. It's high modulus yes, but when it fails it does not like to stay together. I am talking about how I can easily ply the resin research stuff off the mixing cup, usually in one big pliable piece. West system was always more stiff and tending to come off the cup in flakes. It's just different materials...while I certainly respect your expertise, Greg loehr who sold me the resin has made like 30,000 surfboards and that dude is a chemist. hes mixed a bit of epoxy himself, and He has some interesting ideas about impact resistance and flexible resins, and if you read brads blog they did several impact tests where the flexible resin outperformed west. I've used west for years, but this new resin is a different animal and I think for the application I am using it for it will perform well.
Permalink Reply by chris towles on May 3, 2013 at 4:38pm
Rojo, for 6 oz or 9 oz cloth ranks has the best price. They also have good prices on heavier glass. If you want the 18oz biax, you can get it form raka also but it's cheaper at fiberglass supply. You only need like 5 yds tho so just do the math and see what price is best. If your boat is a standard side panel size 24" at the locks one 6yd sheet of 50" material will cut into 2 panels perfectly. Look for deals on close outs, also eBay can be a good place to buy I 6 yd scrap for cheap. I bought a whole bunch of 8-9 foot 8 oz scraps for next to nothing for glassing my bulkheads.
Permalink Reply by Mark Stuberr on May 3, 2013 at 2:15pm

Rojo,

There is a book out there that can answer all your questions. The Gougeon Brothers on Boat Construction. I think you could get a cheep copy from amazon. If you don't have a copy of this book and your using epoxy, well your just pissin' in the wind ; ), ha!

Permalink Reply by tungsten on May 3, 2013 at 9:45pm
Permalink Reply by lhedrick on May 4, 2013 at 7:59am

I have been using RAKA epoxy/glass/fillers for years.

I really don't think it worth a lot of time trying to figure out how much resin you need.  The more you buy, the lower the per gallon cost.  My recommendation with RAKA epoxy would be to purchase a 3 gallon kit.  2 gallon resin 1 gallon hardener. You and split the hardener to 1/2 gallon fast and 1/2 gallon slow.

I say, get plenty partly because I never seem to have enough.  I bet I have used somewhere around 75 gallon of the stuff over the years.  It has so many uses we just can't list them all.

Unlike paint and PVA glues epoxy has an indefinite shelf life.

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