Wood or metal, that is the question.

[MalawiMD]

I would like to build a small flat-bottom boat. I want something light enough that two people can lift it to the top of a 4 runner. I would use this boat for fishing and goose hunting. I think it needs to be 12' X 4' or smaller. I would like to be able to put a small trolling motor on it and also ores.

Anyway, I was wondering if I should build it from plywood/epoxy or go with aluminum. I don't know that much about welding, but my dad has a tig he would let me use. Is this too big of a project for a beginner? Also, I am pretty sure I could build a wood boat for under two hundred. How much would a metal boat cost?

Thanks,

Aaron

[yokebutt]

Malawi,
Since you have the welder available, try burning a few scraps of the right thickness together and see if you can do it, it's not easy for a beginner. Plywood/epoxy would definitely require less skill to produce a good result.

Yokebutt.

[MalawiMD]

Would a half gallon of epoxy be enough to cover a small flat bottom boat?

[marshmat]

A 12-foot boat, with half a gallon of epoxy? Probably not....

My own boat is glass-over-ply construction. It's not hard to do, and a LOT lighter than welded aluminum.
No, it's not too big a project at all for a beginner. So long as you have good plans to work from, a 12-foot flattie skiff is about as simple as boatbuilding gets. I'm a fan of the Bolger/Payson boats ( http://instantboats.com ) in this size; there's plenty of other designs out there.
I'd agree with Yoke- do some little test pieces of aluminum, and then do the same of glass-over-ply, see what you like. Al is harder to work with (for most people) and heavier, but stronger if you know what you're doing.
Happy building!

[cyclops]

Aluminum boats are sealed and built all at 1 time. Scuff the finish, clean cloth and solvent wipe down, Zinc Chromeate primer, color paint. Done. Aluminum boat builders may find it cheaper than a epoxie wood boat over 3 years.

[PAR]

I can't think of any 'glass over plywood boat under 20' that would be lighter then aluminum.

Steel in this size range could also be heavier then a plywood. Steel doesn't come into play until you get near 30'.

Cost for an aluminum boat would be considerably higher then the plywood boat, steel, possibly slightly cheaper. Aluminum welding has a pretty steep learning curve to get good welds for marine use.

Pound for pound it will be very hard to beat, embalmed in epoxy, plywood construction, in a 12' craft. There are many designs for boats in this size and use, quite a few are free on line.

[MalawiMD]

Thanks guys! Well, I wrote up my own plans and started construction on my plywood boat yesterday. Now I am ready to epoxy. I built a real small jon boat. I noticed there is a considerable difference in epoxy prices. I found 1.5 gallon thin 2:1 epoxy kit for $50. Does you guys think this would do it? I have seen a lot more expensive epoxies. Do I need the expensive stuff?

Thanks,

Aaron

[cyclops]

My goal on light weight plywood boats is 1/4" EXT. AC Home Depot stuff. Simple vertical bows, double bottom seperated by 4--1' apart, 1" fore & aft runners to hold a load better. Glued & screwed. Then epoxy in any open seams. 4 coats of spar varnish and the thing looks pretty good as a woodie. I get some Hom. Dep. aluminum 1/2" X 1/2" angle for all the wood edges and bend it to hug the seams. Then you can slide it on any thing OK. You have to protect the plywood edges or they chip and soak up water. That is why I say, Aluminum, is cheaper if a welder is free.

[marshmat]

Quarter-inch AC exterior is indeed pretty nice boat wood- my own boat,Sunset Chaser is built largely from that. In a three-ply sheet you'll usually get an A, a B and a C grade ply- the difference between AB and AC is that in AB, the crappy layer is int he middle where you can't see it; in AC it's easily reachable to patch if you want to. After taking a few chunks out of the spray rails I've done the aluminum-angle thing too, works great.

[PAR]

For a Jon boat with little shape to it, AC grade will do fine, but it will have a substantial number of voids, construction defects and likely will break down faster then a better grade of panel. As a general rule, the better lumbers and construction used in the higher end panels will greatly out last typical construction grade lumber.

Epoxy is a difficult ball of wax to nail down. I has two general uses and does both well. It's used as an adhesive and as a coating to lock a fabric into a plastic matrix for abrasion resistance (thin fabric laminations) and strength (much thicker laminations) Typically the lower ratio epoxies are "unrefined" formulations (hence the price) and the lack of refinement causes issues, like narrow working environment variables. Some folks will have you thing the higher ratio resin/hardener mixtures are diluted some how, they're not. These are the refined epoxies, a more complicated formulation to address short comings of the less refined stuff. As a rule, the less refined stuff is more difficult to work with, for the beginner, as they need a product that is more forgiving, especially in the pot life and workability areas.

So the selection of an epoxy is dependant on the need. Are you just skinning the hull with a light weight cloth or are you looking to put in fillets, which can dramatically increase joint strengths? What kind of environment will you be working in? Temperature, outside construction, need a good finish, subsequent coats, etc.?

What brand are you looking at and what are you looking to do with the epoxy?

[MalawiMD]

Well, I am going to use it outside in my garage. The temperature is about 70 degrees in the day and 65 at night. I would like to use the epoxy to coat the boat and also run filllets. Here is the page I found it at: http://www.shopmaninc.com/epoxy.html

I noticed they have 1:1, but it is listed for table tops.

Thanks,

Aaron

[PAR]

Just coating your hull will offer little protection. Very quickly the un-reinforced coating of epoxy will become breached (nicked, scratched, etc.) and moisture will get in, which will start rot.

Epoxy almost always needs some sort of reinforcement. This could be a fabric like cloth or mat, it could also be a filler material like milled 'glass fibers, acting as the reinforcement. Typically, a sheathing of light weight cloth, set in epoxy, is applied to the outside of a hull for abrasion resistance.

The table top stuff is not what you need. The 3:1 goo, plus fabric and some different fillers will get you going. Log onto www.westsystem.com and have a look see at their resources. They have lots of information and free booklets on epoxy use. Of course the info is geared towards their products, but the methods and techniques apply to all epoxy use.