New To Boat Designing

Hey all,

I am currently planning a wide-body flat bottom design. CDX ply on pine frame. the seams will be taped and glassed, and I plan to spread epoxy on the surface of the hull without fabric.

Am I nuts, wasting my time or does this seem viable?

Thanks!

 

I think you will need to give more information. Like are you planning an 8ft long boat, or one 80ft long?

What are you building it for - what is it's "SOR" - statement of requirements

Richard Woods

 

Considering the low cost of fabric, there is no sensible reason to remove this invaluable part of the hull protection - especially as you are planning to use such a non waterproof structure.

 

Welcome to the forum.

CDX is the absolute worst plywood available. If it's marked "Exposure 1" it'll delaminate in very short order. In fact, finding true marine or "Exterior" grade CDX is usually a special order from the local lumber yard. CDX is just one step away from particle board and designed for static loading, not the dynamic loading seen in boats, especially powerboats that might see considerable slamming loads at speed.

Epoxy on the surface of the hull will not do much, except provide a brittle plastic coating, that will easily be breached, trapping moisture in the wood. Fabrics, set in epoxy are what offers abrasion protection.

A taped seam build requires at least some fabrics on the seams at the very least, or it doesn't work.

All of these topics are well covered here and on the net. Some research is in order on your part, so you can get your head around the materials and techniques used.

What design are you building?

 

From the title of the thread I gather you are planning to build your own design. As PAR pointed out it is not likely to be a durable boat, and you will have to fill the surface defects of the plywood so it won't be all that pretty either.

However, given the risks it's not a bad idea to use the cheapest possible material for this first design attempt, and presumably your first build too. Are you going to share with us your intentions for the design?

There's a lot to learn and a lot of mistakes to be made, I made a few of them myself, but if you intend to work your way through several designs until you know more-or-less what you are doing, then good luck and don't be afraid to ask for help. On the other hand, if you seriously intend this boat to be a success and to last for some time you re going about it entirely in the wrong way. Once we know your long-term plans we can offer our best advice . . .

 

^ AK has given words of wisdom. It is in your best interests to accept both his and Pars advice and council.

 

short answer: yes, you are nuts and wasting your time.

now that we got that out of the way, how about more details about what you are planning on building.

CDX is really a bad idea unless you are building a one season "disposable" hull. It has a lot of voids that will eventually get water seeping in it and it will rot from the inside. AC plywood would be a better choice, or of course marine grade. if the cost of the materials are a concern, you can always use strip built method. ripping the wood strips your self would yield some really inexpensive hull material. You will have to fiberglass the whole outside and inside of the hull.

 

Petros, stripping would add some time to the build. I would really like to see what he was planning, a rough sketch would be OK, it may not suit a strip-built approach if it is wide with a flat bottom. On the other hand your SOF sailboat would certainly minimize costs and build time and as I recall it was fairly wide too. May be just what is needed here . . .

 

you know I love skin-on-frame, but we need to know more information. It is not really suited to hulls that have large flat panels, nor for something designed to beach. It can be made to work, but using plywood would be just as easy, and more durable when the routine use is to run it up on a beach or rocky shore. It could be one of the reasons he wants to use thick CDX, it is cheap and tough.

If the OP would come back we might learn something more of what he had in mind as far as usage, size, etc. These kind of posts are like the ones that go; "how much does it cost to build a sailboat?"

 

A "wide body" flat bottom boat suggest a flats style powerboat, which is way outside the SOF spectrum. Who knows what he's thinking, but I'm betting he was figuring "how hard could it be", just before posting here.