Epoxy Questions

Discussion in 'Boat Tips' started by turtle1173, Oct 4, 2005.

  1. turtle1173

    turtle1173 Member

    Mayfield, KY
    Hi all,

    I've been putting off re-doing my boat because it seems like the more I think about it, the more questions I have. I want to have the least amount of down time.

    My "current" concerns have to do with epoxy. I've read about everything Mark J has posted about this subject but can you believe it, I still have questions, LOL. Thanks Mark for all you've written on this subject but here's a few questions I have.

    1) What is the difference between Epoxy and Polyester Resin? Polyester Resin seems readily available but I know it isn't supposed to be as good.

    2) When I go to coat my plywood with Epoxy, do I need to thin it out? If so, how do I do this?

    3) How much epoxy will I need to do 2 or 3 sheets of plywood?

    4) Will any "local" stores carry epoxy or do I need to buy it online?

    Thanks again.
  2. bigflathunter

    bigflathunter New Member

    Lawrence, KS
    I too learned how to do a boat from Mark J as well as many other sources. I'm glad to hear you've decided to do it the right way. It's much more expensive to do it right the first time in the short run, but long term you'll have a boat that, if done right, should last as long as you and won't require more money to fix again and again.

    Here are my answers to your questions. I'm pretty sure they're right. :p

    1) The difference is that polyester is not 100% waterproof. Water will eventually make it through the polyester resin, it will delaminate from the wood, and your project will start rotting all over again. Chances are good that's why your boat rotted in the first place. That's why mine rotted.

    On that note, the fiberglass mat commonly used with polyester resin is no good for using with epoxy. There is a bonding agent used to hold the mat together that dissolves in poly resin but not in epoxy. This makes it virtually impossible to wet out the mat using epoxy resin. Stay away from this or any cheap fiberglass. That's what I was told.

    2) When I coated the plywood in my boat, I did not thin the epoxy. I am using SystemThree's general purpose epoxy. It worked just fine for me using a 6" squeegie to spread it with. I think if it was too thin it would soak into the wood easier, resulting in using more epoxy used in the first coat when the wood is still really dry and thirsty. Don't get me wrong, you want the wood sealed well, but if it is epoxy soaked to the core, IMO, it just adds weight and wastes epoxy. If the surface is 100% sealed you will be fine. The exception is the end grain on the plywood: keep brushing coats of epoxy on until it stops soaking it up. You want no water wicked into the edges of the plywood.

    3) Here is the general idea given by system three in their catalog: for softwood plywood or veneer, you'll get about 250 sq ft of coverage for a first coat per gallon, and 400 sq ft of coverage for subsequent coats, per gallon. Meaning that one gallon will cover 250 square feet of bare soft plywood. One gallon would do 400 square feet of previously coated soft plywood.

    For hardwood plywood or veneer, it's 325 sq/ft per gallon first coat, 400 sq/ft per gallon for subsequent coats.

    For four sheets of plywood, you'll be coating 256 sq/ft of plywood with a first coat. Remember you'll have to coat both sides. That's a gallon just for the first coat on all sheets. And you'll most likely do at least two coats on everything.

    Remember that's system three talking. For us amateurs it could be a whole lot different. :D

    4) I buy my stuff from boatbuildercentral.com. They've had all the epoxy stuff I need so far. You can shop around a little, some places will sell one thing cheaper and another thing more expensive, but you'd spend more in shipping to order from two different places. They seemed to have a good balance, and shipping is quick. About 4 days to get to me in KS from FL. Should be about the same to you in MO. I searched thier site for a dealer close to you and nothing came up.

    I would stick with a good name brand epoxy, but it's up to you. I went with system three because their web site is helpful, and the epoxy trial kit they sent me was easy to use and as long as I mixed it right gave good consistent results. Another good reason is that it's what Mark J uses, and I figure he knows what he's doing. I wouldn't order direct from them, though, because they are a lot more expensive to buy direct from. Regardless, I'm 100% satisfied with how their product has worked for me so far.

  3. Mark J

    Mark J New Member

    Four Oaks, NC
    Aaron, you covered it well.
    Now when you going to build a whole boat?
    Epoxy is somewhere around 99% waterproof which is just enough to aid in preventing dry rot. polyester resin is not anywhere close to being wateproof. This is where hull blisters come from in glass boats, particularly in boats that stay in the water for extended periods of time. Polyester resin does not bond to wood. This is why most fiberlgass boats suffer transom rot or sole rot.
    There is absolutely nothing wrong with wood in a boat if installed correctly.
    Any time a boat manufacturer touts... no wood in our hulls. All they are saying is ..We aren't willing to install wood properly in our hulls which makes me wonder what else aren't they willing to do properly.

    They are now selling E-poxy which is just another brand of epoxy. Many builders like this brand for its low blush characteristics. It is a little cheaper then systems 3.
    The thing I really like about system 3 which may benefit a beginner that has encountered some type of problem is their support.

    You'll find many generic epoxies or epoxy look alikes on shelves in boat dealerships and such. Learn the product before you attempt to buy anything epoxy or glass related at such places because finding someone knowledgeable on staff is a rarity.
    West Marine offers epoxy but it is a 5 to 1 mix ratio and way too expensive.
    5 to 1 mix is actually stronger but not necessary. Using 5-1 mixes you'll no doubt encounter more batches you measured wrong that will not cure.

    Now for an economics lesson I know you dont need but it may benefit someone else sometime.

    Aaron picked his project and stuck with it without if I recall an ideal place to work on it. He spent a nice sum of money restoring a boat he obviously liked.
    I have no doubt it is 10 times better built then from the factory even as a beginner. This stuff aint real hard to do. Intimidating at first, yes.

    If you got an old rotten to the core boat but a decent engine on her the best thing to do money wise is to build one and reuse the motor and trailer.
    About 3 months ago I purchased all the materials to build an 18 foot center console minus sand paper, rubber gloves, paint and other expendables for less then 1500.00 and that was with some extras.
    I stripped what I could or wanted to reuse off the old hull to save a little rigging money on the new one.
    If people just knew how little skill it takes to build a darn good boat of the sizes I'm talking about and have been amazed how good a job some folks have done on them without ever running a skilsaw in their life the boat manufacturers would be out of business and outboard motors would be 1/2 the price they are now.
    Have doubts about a plywood composite boat?
    The hull bottom and sides according to the plans are 1/4" thick ply on mine with 12oz biaxial glass on the exterior.

    Here is how much I doubt because I've built before.
    Pick any fiberglass boat and any aluminum boat and park them beside my plywood composite 1/4" hull.
    Let me take my 22 oz straight claw framing hammer and have two wacks at your boat and I'll give you 5 on mine.
    Then we'll move up to the 2 pound pound hammer.
    We'll then see 3 things. The extensive amount of damage, the lack of damage, and how much the cost is to repair each boat.

    We've got plywood epoxy composite yachts that have been sitting in saltwater for 25 years and get used daily.

    Cheaper, lighter weight, and more economical to tow and use.
    It's a win win situation with a little sweat equity invested and a lot of fun to go with it.

    Now Aaron, I think your next cat boat should be the CS25. What do you think?
  4. bigflathunter

    bigflathunter New Member

    Lawrence, KS
    The problem with building your own boat is trying to decide if you want to spend your free time working on the boat or going fishing. Short term fishing seems logical. But the more you work on that boat, the more you'll enjoy fishing when you get to it. And even though it seems expensive, as long as you don't mind a hobby other than fishing, it's extremely cheap. People who collect stamps might have $5,000 in paper collected. At the end of spending $5,000 on building a boat you actually have something useful that doesn't decline in value if you get it wet. :D

    The CS25 sure is a nice looking boat. I added up the bill of materials for it and it looks to be around $4,500 in materials. 34 gallons of epoxy, 38 sheets of marine ply, and all that biaxial glass adds up quick. Of course if I could call in I'd probably get the epoxy and glass a lot cheaper in a bulk order. But then I'd have the problem of a motor for that beast. Even after 5 g's I would still have a 1600 pound rowboat. Not to mention it would be on a stand in the barn without a trailer. It sure would be fun to build though. That is a long ways down the road for me though.

    Did you see the picture of the CX 25 in the guy's driveway with a front end loader hoisting the thing with tie-down straps? I'll be he had the neighbors' attention that day.

    Right now I'm thinking about doing something more practical like the GF16 for using on the river and maybe in the shallow tree infested water at Clinton for running lines. A boat like that could probably be stitched together in the garage over a weekend or two. It's between that and the GV15 in the open layout so I could get the ride of the slight v hull. How about that, I'm not even done with my current project and I'm planning the next. I put the floor in over the weekend. The 5200 is drying. It actually kind of looks like a boat again.

    What was the first boat you built?
  5. Mark J

    Mark J New Member

    Four Oaks, NC
    That CS25 in NC is ready to launch.
    I'm pretty sure he has launched and is probally debugging it before he reports back.
    I think he last reported he had $60,000 in it but it has a genset, air conditioning, and some nice electronics to boot.
    He is also running an inboard outboard diesel I think. 320 horses
    I imagine the engine, controls, and hardware were 25-30G's.
    He has saved probally in the neighborhood of 40 thousand and got exactly what he wanted in his boat.

    Sure you dont want to go with a GF-18? I got a new set of never been built off of plans for it and will work you a deal. it's a license to build one boat. Half price?
    That is a really big boat with tons of room. I have built one of those and sold it right as I was flipping it over to work on the interior. A 40 horse is the maximum engine size for it. That boat paid for this one.

    My first boats were many of the creek boats. Boats like the pirogues or one man stump jumpers you commonly see in these parts.

    To be honest, that 25 foot Panga would be an awesome cat boat.
    Imagine that, A 25 foot boat that maxes out at 125 horses.
    Economical and efficient hull design and they run them suckers way offshore.

    There are many of those plans that can be altered say from a cabin cruiser to a center console. The Novi 23 is one of those that I think would make a brute of a center console :cool: .

    My goal is to upsize every few years which means I'll almost constantly be building. I want a 25 foot Novi or something very much like it.

    All my projects that have held me up or should I say other people's projects are winding down. I have continually been working on my barn here and there when I can grab the time and materials. My first concrete pour is going to be in the barn itself. That way I can get in there and throw some heat in it and atleast get the transom and some panels built over the winter. If everything works out I may have a hull by spring.

    That reminds me, i got to get our resident turd herder Keith Sword to do some plumbing in the barn before the concrete goes down.
    We'll document his boat's extensive repairs also. His will include a major transom repair.