Plywood Question

I have been looking for a project that I could do with my kids and they wanted to build a boat, so here I am after looking at numerous designs I decided to purchase the plans for Devlin’s Candlefish 16. I am currently trying to get everything together that I will need to build it then I noticed the price of marine plywood. I spent about 20 years working on and running fishing boats in So Cal and I understand the need for marine plywood but I do not have much experience with smaller boats.
I guess my questions is-
Where could I cut some cost? Could I get away with buying higher grade plywood for the hull and use the lower grades (or non-marine) for the bulkheads and other places that will not be submerged in water?

The boat will be kept on a trailer most of the time and only be in the water maybe once a month or ever other weekend for a day at a time. Looking at the cost and comparing it to spending about the same to buy small used aluminum boats in my area I think I just need to be talked into or out of building this thing.

Any comments or experiences in this situation would be greatly appreciated.

 

first of all, buying a nice condition used boat is almost always more cost effective than building the equivalent boat. It is a false economy to think you can build it for less money than buying a used existing boat.

there are only two reason to build it yourself: you enjoy the creative act of the building process, or you are building something (a specialized or custom design hull) you can not buy. Neither of which save you money.

If is far faster and less costly to buy a boat than to build one, even buying a project or boat that requires renovations are almost always cheaper than building from scratch. Though there are many projects that are best left alone, there a saying amoung boat owners: there is no boat you can afford less than the free one.

If you are bent on building your own boat just for the joy of building it yourself, you ideas have merrit with the following caviates; you can use hardware store extiror grade plywood without too much problem if you take the extra effort to fill any voids around the perimeter and seal all of the end grain before you install it. The other is if it is stregth crtical installation, you might consider going up once size in thickness when using the lower grade plywood.

There are many designs that are intented for using ACX exerior grade plywood, the problem I think is that voids can trap moisture and it will rot from the inside sooner than marine grade. Marine grade also has few voids and defect, usually more veniners and is stronger that construction rated plywood.

List member PAR has suggested using two layers of 1/4" ACX plywood laminated with epoxy to make 1/2" plywood suitable for use in boats, not a bad idea if your design calls for 1/2" plywood. Also, if the design has you covering it with fiberglass and epoxy resign, the wood core strength is not as critical as a pure plywood boat.

I have often used exterior grade plywood on quick build small boat projects, but I did not expect to last very long, even so they usually hold up for five or more season of boating. So it just comes down to your long term plans for the boat. The extra cost of the plywood is actually not that large compared to the overall cost of building the boat, and if your hard work and effort is to last longer, the better quality materials are usually justified.

I have built something like 19 small boats, all of them wood and none had motors (kayaks, canoes, small sailboats), some I have used quality materials when I can get it at a good price, but most of it was either salvaged lumber, or the best I can pull out of the pile at a Home Depot or Lowe's. I think if used carefully the hardware store plywood is perfectly good for knockabout boats, there are others that disagree and will tell you otherwise (I call those people "materials snobs"). But they often do have a point, but I enjoy building as much as using them, I consider each one I build an experiment since I am trying out new ideas, construction methods or design changes, not so much concerned that it needs to last 20 years. Some the experiments I took home and dismantled after one or two uses to make changes, so I lean towards less costly and less durable materials anyway.

Take your pick and take your chances. It just depends on what your long term goals for the boat are going to be, only you can answer that question.

 

It's really about how strong the boat needs to be, and how long you want it to last. This probably depends on how old your kids are, and how much money you have to throw at a new boat in, say, 5 years.

Chances are, this is not a "fun is in the building" project, given that kids generally have a pretty short attention span. For a really nice build it will take at least a few months, particularly if it's your first. Consequently, I'd go for a quick build, and be happy to save money on the materials a bit, while compromising the longevity. You can beef up the structure a bit (but don't add too much weight) to counter the deficiencies in non-marine ply. Ultimately you'll get a boat that's fine for a few years (for your usage), but will start to show it's age more quickly than if you'd used marine spec.

The expensive bit, though, is not usually the hull (unless it's very exotic (ie. very thin skin on frame, or Carbon, etc.)). The engine, fittings, and all the other stuff will cost a lot more, unless you can pick up a donor boat or an old engine cheap. And at that point, you ask why not just buy a second-hand boat.

On the other hand, you may want the boat to last for the next 20 or 30 years, long after the kids have stopped using it to take their freinds out, and you can get back to using it to go fishing. In which case, skimping now will cause you major problems.

The trailer can also be pricey if you're not careful. You can build your own, very successfully (I've done it). Though I would advise you to get a fabricator to do the primary, structural welds. I think my cost was about £350 in parts, about £400 all-up, and "pro" trailers start at £800 upwards for the same size, and the blocks to take the hull aren't anything like as nice on the pro trailers.

The best advice I can give is that you price the whole job in terms of time and money (get the kids to help in this, as it's all good for their development), then decide whether you can commit. It may not be practical, but if not, at least you will have tought them about sizing a job, so it won't be a total waste.

When working out times, remember that everything takes twice as long as you think, and you only get 8 hours of work done over a weekend (not 16 as everyone thinks). Be pessimistic about times, particularly for the fit-out, and remember to include time for fitting buoyancy bags, hatch covers etc. and time for painting (which will also take longer than you think, and can be a bit weather dependant).

Finally, if you don't have a big enough workshop, rent a big enough workshop. You'll save so much time and grief in comparison to building it in the back yard!

Good luck,

Tim B.

 

Just remember this your project and you will be left with it all by your self !!
For the small amount of use !!!yes buy a secondhand aluminium boat and get the immediate use . The problem making things for kids with kids is they loose interest in just a couple of days and you on your own . dont waste your time get on with living .
I bought a small old second hand boat and we used it one xmas over the holidays once life got back to normal kids in school they wernt the slightest bit interested ,so its mine and i ripped it apart and did a totall rebuild and repaint with all new windows etc etc now i go out by myself and i get the pleasure from my labours kids and mother dont want to know !!.

 

Thanks for the info!
I will spend some time going over the numbers and see where its at. I was not planning on it lasting a long time just wanted it to be safe for the family....so much to think about.

 

ACX plywood has become so poorly constructed in recent years, is can't be recommended for much of anything now. The APA has changed it's grading system again, making it even easier to buy what you might think is suitable plywood, when in fact it's absolute junk. Any plywood with an APA grade has to say "Exterior" only. Don't be confused with "Exposure 1 Exterior" grades. This will delaminate just at the mentioning of a few thunderstorms.

As to economical building: do you want the part that keeps your socks dry to be the place you cut corners? Really? There are many places within the build, where you can use lower grades of plywood (APA Exterior for example), but do you think the very thing that is keeping the great sea from drowning you butt, is the best place for this stuff? My point is, the hull shell portion of the build is a small percentage of the total cash outlay and build effort. Get a used motor and save some bucks, go with house paint instead of LPU's, skip the cloth sheathing, employ used cleats and bow lights, but do yourself a big favor and make the hull shell out of the best material you can get.

Look at Hydrotech and Aquatech brands of plywood. These are first class sheets and usually a lot lower then Joubert or other high end stock. Shop around for good stuff and don't be tempted to use Lowe's/Depot stuff, as absolutely nothing they sell is quality plywood. Every once and a while they have some underlayment stock with higher then average quality, but you have to know what to look for. This stuff is weak, but reasonably quality. For example a 1/4" underlayment sheet from Lowe's/Depot is about $17, but compared to a $35 Aquatech (BS-6566) sheet, not even half as strong. So yes, you did save some money, but you also reduced the strength of the panel, by over half too. If this is the bow panel, bashing it's way through a summer squall, on your way home, well farther from shore then you can swim to, which material do you want between your socks and the wet stuff?

 

Without wanting to be rude Mr Evil - this is only a 13ft boat, that may cost between $850 and say $1200.

Of that, without having the study plans, we have to be looking at about 6 sheets of ply, which say, might cost about $80 each ?

if we save a huge 20% on plywood, we might save .. what, an amazing $150 or so ?

So for such an insignificant amount, why on earth scrimp on dubious quality material, that as Par says, might risk your life ?

Honestly, you will be spending more on life preservers and and paint than this.

My dad used to say of any project "Do it as if you meant it". I think you really need to consider if you mean to own a boat.

 

Thanks guys.

The wife agreed with you guys, she said if your going to do it then do it right. So it looks like I need to start looking for a good source of plywood in my area.

 

1/4" fir plywood should not cost more than 45 dollars per 4' x 8' sheet(U.S.).

My latest boat, http://www.boatdesign.net/forums/boat-design/teotwawki-boat-42752.html#post547721, cost a total of $1260 counting brushes and rollers.

 

http://www.glen-l.com/resources/lumber-suppliers.html

 

Building a boat

I definitely recommend that anyone who has the ability should build their own boat. You can always buy a used boat for less money but it will be somebody else's boat. I would definitely use marine plywood at least for the bottom. I used 3/4" pine boards for the sides and 1/2" ACX for the deck and sealed every thing with epoxy. This was my first boat from my own design and I'll admit I know very little about boat building but after sometime on the water it has worked out real well. Never sacrifice strength for weight and ask the experts like PAR and others on this site if you need advice they helped me. See my thread [A boat, a motor and a trailer] in boat building if you haven't already and good luck with your project.

Dave T

 

I'm with you Dave. Its not the owning a boat so much, its solving the challenges and the learning. It can be a wonderful thing for a family to be involved in - sure beats TV and computer games.

 

I disagree with the comments about kids attention spans. Yes they do tend to be short, but it also depends on their age, and how much they are interested in building and using the boat. If you make this a learning experience for them and involve them by letting them do many of the tasks, then they will feel that it's their project and will brag about it to their friends. There are a lot of tasks they can do. Let them do them and let them help you do the more difficult ones. Many schools use boat building to teach Math (measureing, fractions, addition, subraction, multiplication division, etc) chemistry (glues, resins, paints), Biology (wood types) and so on. So they can learn a lot. Plus that they will take a lot of pride in it. A lot more than in a used aluminum boat. There are positives and negatives to both.

I have recently (the last 5 years) built two small boats, a 12 foot rowboat and an 8 foot sailing dinghy. I used Douglas Fir marine ply on the bottom of the 12 footer and exterior on the sides and for seats. On the dinghy I used all Okuome marine ply (BS-1088). The difference in appearance is significant. Plus that I have already had to replace the tops of the seats in the 12 footer because of the lousy adhesion of epoxy resin to the Doug Fir ext grade, and how rapidly the appearance deteriorated. I replaced with Okuome BS1088. Within 3 years I was resanding and recoating all bare wood, with epoxy resin. The dinghy is a little over a year old and still looks like the day I finished it. So the quality of the materials makes more of a difference than just strength. Of course if you plan to paint and have no bare wood then the appearance issue is based mainly on the how well you paint it.

12 foot rowboat



8 foot sailing dinghy