Wooden boat building.

I see , ok yes that makes sense especially being a 12 footer more strength...If I am to make an 8 footer would 1/4'' be sufficient for the bottle and sides and was thinking to make the seats 3/8''..Trying to go as light as I can..Here is a design I like but i cant understand why they say the 8 footer calls for 3 sheets of ply.. http://www.boatdesigns.com/products.asp?dept=738&val=4

Can you see why the reasoning is for 3 sheets of ply for the 8 footer?



Terry

 

I guess that has double transom and bottom!?

 

I dont think it does but maybe, I think I will email them to ask why it takes 3 sheets.

 

Hi again Terry , very impressed with the idea of building without the stitch and glue method. Would you know of any plans out there that dont use the stitch and glue method? Seems all the plans are calling for the stitch and glue and would really like to stay away from that if possible. This is a far cry from boat building but I build wooden boxes of varies sizes and I use a very strong outdoor glue and then finish off with varathane and never had any problems with them..They stand up really well. Understandeably with boats you would need fasteners but I think you know how i can relate to what your saying.


Terry

 

I know Par has some nice plans as I bought one for a taped-seam 10 ft sailing skiff which I am in the process of building.

Any stitch and glue or taped seam design can be adapted to the chine log method provided it is fairly small; it is not suited for larger boats because the sheers become too stiff to bend around the forms. It is similar to the build method used for pirogues, which you can find with Google. The plan has to provide the plank developments, which is the shape they have when flat, unless you know how to generate plank developments. I cheat by feeding the lines into software like Free!Ship which will generate developments in a New York second.

Basically I start as for S&G by cutting out the developed sheer planks from ply. On the inside I glue chine logs along the bottom and inwales along the top, my rule of thumb for thickness is 4x ply thickness for logs and 1/2 the designed overall thickness for gunnels, since I will add an outwale later which adds the other half. this makes the thin ply pieces stiffer and easier to handle IMHO. Then the assembled sheers are bent around forms and secured to the transom, stem and bulkhead(s) more or less in the traditional boatbuilding way. Naturally I have developed some tricks that suit me but it is not hard to figure out. The boat is built upside down, usual practice, and the sheer edges are planed flat for the bottom which is glued on for a canoe or pirogue: for a sailboat with its higher stresses I use glue and screws, and the bottom joint is one of the few places where I use epoxy. The canoe ply is so light I can simply wrap it while the glue sets.

For the sailboat I use regular roundhead screws to hold the bottom until the glue sets then replace those with countersunk brass or bronze ones, as the steel ones are less easy to damage during the rush to clamp the glued joint, and cheap. After the outwales are put on the joint width for gluing the deck is the same as if I had put the more usual one-piece inwale or clamp.

Ply usage for this boat is as follows, with the sheers and bottom assembled together with bulkhead and transom. I have used a sheet of 4 mm ply for the sheers and a sheet of 6 mm (1/4") ply which was for the bottom. The transom is 3/8 Baltic Birch that was lying around. I figure it will take another sheet for the bouyancy tanks which aslo serve as side decks and seats (I changed Par's design here), and I have a piece of 3 mm ply left over from a canoe that will just do the foredeck. say 3-1/2 sheets total. So I'd guess 3 sheets is about right for an 8 ft boat, plus some solid wood for chine logs, battens and gunnels. I could save a sheet by leaving off the tanks/seats but it would be rather basic then, and I would have to add more structure as it would be too flexible.

One last note: I use softwood for the logs and 'wales. That's because the strength of the glued joint is limited by the weakest wood in the joint, which is the Okoume of the ply. Hardwood would just increase weight but the joint would still fail at the ply. That might change if hardwood ply were used, and of course if fasteners are the primarly method of jointing that would change things because of the hardwood's superior fastener retention.

The main reason for this approach is, I am lazy and cheap: no technical advantage that I know of.

 

Wow such a mouthful of tips lol...You have the knowledge thats for sure..I will check with Par about some plans and take it from there. I plan on making as demo and then selling them in my area as there is a demand for them..Worse case scenerio is if they dont move then I have a demo for myself.