wooden boat building/hull questions

I want to cover the outside for water protection abrasion and strength. I will have to glass all of the outer joints. I have seen that hulls have been completely glass for protection and waterproof the outer hull. I don't want the thing to rot away. Is there a more cost and weight effective option for waterproofing and protection of the outer hull I direct contact with the water.

 

The Gougeons once said it is better to glass the inside rather than the outside to stop rot. They were talking about boats with a cabin or closed spaces.
That is because a closed space with a tiny bit of water will heat up in the sun and the water evaporated to vapor which penetrates thru paint quite well.

If the boat is totally open that doesn't apply.

I encourage you to read the Gougeon book.
It might take you a while, but the first chapter tells you most of the theory.

 

What Mead and Jan were talking about is sweet water does more damage to moored and berthed yachts than anything else, hence the suggestion of inside protection. The simple reality is if you want abrasion protection an external sheath (set in epoxy) is ideal. Unless this sheathing is quite thick, you're not going to get much strength or stiffness over the existing plywood planking.

If you don't want it to rot, then use rot resistant species (not PT) and epoxy encapsulation techniques. Additionally, maintenance is a huge consideration, after it's built.

The book mentioned is a free download, so have a look (> http://www.westsystem.com/ss/assets/HowTo-Publications/GougeonBook 061205.pdf <)

 

This is the typical mistake of amateurs of trying to produce a masterpiece on the first try. You have no experience designing and building. It makes more sense to use cheaper materials to learn and see if the design even makes sense and floats.

 

I live aboard a wood 83' former USCG built in 1942. This boat was built for ocean patrol, and heavy enough to carry depth charges,20mm and 50 cal guns and rescue gear. The planking is 1.25" thick with ribs on 1' centers and 6 stringers each side. Your initial plan is heavier.
I am also a former shipwright and built and repaired many wood boats and ships. You're way overbuilding. A 20' boat would be best served with thin plywood skin and a epoxy fiberglass cloth coating. Or just fiberglass. Forget poly resin. As others have said, it's cheap for a reason. If used as a sealer and exposed to UV your lucky to get a couple years before it flakes off.
When younger, I use to do a lot of decks on commercial boats. 1/2" plywood over the original decking and 2.0 rsm with epoxy on heavy built boats. It will last 20+ years with proper care, maybe forever. I never had a deck come back, so I don't know. On the other hand, occasionally I would redo a poly deck someone else did. Once I got under a corner, I could pull great patches (sometimes the whole deck) with one pull.
I'm 67. The only resin I use now is West. It's the easiest to get a good mix and has a number of hardening options for different working temperatures. But, there are other good epoxies out there. I don't use poly even for fills.

 

lotronuts,
How long to you expect this boat to last? I'd give some consideration to just build the boat and paint it. Your boat will be a lot lighter and even cheap resin is expensive. Paint the first coats in the bottom w kerosene turpentine and a bit of paint gradually increasing the amount of paint till your'e at 100%. Some fishermen paint w house paint. They point out that it lasts 10 to 15 years.

Are you designing this boat yourself?
The Spira plans don't cost that much. Just follow the plans on scantlings.

When I was a young man I designed and built a 28' plywood boat and went a bit too light. In 3' waves the bottom flexed too much IMO so I just added another piece of plywood and it took care of the flex. She withstood some very rough going for quite a few years and more painting was all that was needed. I'm not the kind of guy that slams a boat up on the beach though.

 

I can't understand this. The epoxy resin I use costs less than either a decent polyester resin or decent house paint. I get all of these at a commercial discount, but the % is about the same and wouldn't change the result. It's been this way for 20 years or so now. Epoxy is cheaper and lighter than any of the other stuff.


Paint-
http://www.sherwin-williams.com/hom...=exterior-paint-coatings/primers/&N=530332923

http://www.sherwin-williams.com/hom...=exterior-paint-coatings/primers/&N=530332923

http://www.sherwin-williams.com/hom...r-paint-coatings/paint/&N=106978319+416668465

Polyester (iso) and vinyl resin

http://www.fibreglast.com/product/Isophthalic_Polyester_Resin_just_resin_90/Polyester_Resins

http://www.shopmaninc.com/polyesters.html

epoxy

I can get 3 gallons of 100% solids laminating epoxy dropped on my door step for a lot less than any three gallons of this stuff. Any hardener I want, or some of each. About the same price as a crappy boatyard ortho polyester resin. I order from the factory and the price list isn't online, but they email one to you. Epoxy does have a higher disposables cost, and you end up with a Frankenstein's lab of stuff dedicated just to epoxying. And this does increase the cost quite a bit. Even small jobs take a lot of space - I set up two 3 x 8 tables for mixing and tools. But if you need to actually protect some wood for 25 years, I don't think anything else can compete with epoxy on cost.

 

Who are you getting your epoxy from Phil?

 

Fasco. I have mentioned them a couple times in the past year, and didn't want to look like I was shilling for them. When I started the post, I expected to find their price list online, but it seems to come and go. They have distributors that don't want direct competition from the factory, I suppose. The last time I ordered from US composites because I needed it in the mail right away and it was 3:50pm on Friday. US got it shipped, Fasco was closed. But the price stung a bit. My own fault, I had no time to shop around (I liked the product). With some suppliers, the standard 1 or 1.5 gallon kit is not the cheapest way to go for residential shipping. Three gallons of a 2:1, or 4 gallons of 3:1 makes it easy to for them to can, bag, and box. Everybody I've bought stuff from would sell full cans or jugs cheaper. I don't much care if quantities of hardner and resin don't work out exactly, It'll all get used up one way or another.

 

philSweet,
Wood boats don't NEED epoxy or FG.
Just good and fairly often painting.
I thought this approach should be considered .. especially for the OP.
Looks like he has in mind using Everyday lumber ...... Hemlock 2X4's and 2x6's.
Perhaps galvanized nails.

 

Wood boats that rot apart quickly don't need epoxy.

There certainly are those that are well built and properly taken care of that don't, but there is a massive history of wooden boats that don't exist anymore that were painted.

Why did glass / polyester take over so fast? Cause the wood boats took too much time, effort and cost to keep up.
The most common thread here for 20+ YO wood boats is " my boat restoration" in which half the frames, all the planking below the water line and most of the deck is replaced. Going along with that is the debate - "If you only have a couple of original fittings left is it really a restoration?"

 

I had a wood boat that fell apart in the back yard from too much rain water in the bilges. Not the boats fault. The ice broke a glue line and I could have fixed that too. But if I had taken good care of it it would still be fine. Just need to sand and paint (mostly adding one coat) about half of the boat each year. Not that much work really. FG is over rated.

Almost all the wood boats now are very old. And almost all of them (the ones left) have been neglected. It's the American way. I'll bet there's a lot more good old wood boats in the UK.

 

Even poorly built boats die from the same reasons, that well built ones do - owner neglect.

Taking care of wooden boats is a lost art, with only a few now, that actually make the effort necessary to keep them in good shape. As a kid, I remember my neighbor's morning routine of wiping the dew from his runabouts bright work. He knew the value of this simple act and how many folks do you know that perform this task, just to save a few extra months life in the varnish.

'Glass boats didn't come to be, because of the failings of wooden construction. It was a business decision, based on material and labor costs and had nothing to do with the viability of wood as an appropriate building material. Given the typical "production run" for a popular model, it was cheaper and more profitable to work with 'glass. The materials were cheaper, the labor much cheaper and you could amortize the mold cost fairly quickly with these "in run" savings.

 

Thanks PAR,
Sumed it up well me thinks.
Theres the OMG if you are the least bit smart you will never do that.
And then there's objectivity. People talk like it's imposible to build a wood boat that won't rot away in a few years and the latest plastic miriacle is the only way to go. After all any fool knows wood rots.
Thanks for a bit of reality PAR.