Joint type for bottom planks of a sailing dory

[Little River]

I am building a Cape Ann Sailing Dory. The Bottom planks are 1 1/4” northern pine. On the joints between the planks what is the best joint to use.



Butt the planks with a planned caulk joint (1/8”) on the water side with cotton packed tight under the caulking. Traditional, my preference.
Or spline the planks together with a ¼” strip of marine plywood. Glue the joint and make a 1/8” caulk joint on the water side. My partner’s choice.


Thanks


Doug

[Thorne]

Traditional solutions for trad materials and designs. You can always modify things later if they don't work out as they should.

[adampet]

The Dory Shop uses ship lap for their bottoms. It's traditional, still allows for caulking and even when it opens up doesn't leak as much as a traditional butt and caulk seam. That Northern(White) pine is going to undergo a lot of movement as it shrinks and swells.

Adam

[TerryLL]

Little River,

Welcome to the Forum.
Go with the caulked joint. The splined and glued joint will eventually result in split planks.

The Cape Ann. What a boat! Here's one I built some years ago, from Chapelle's lines. This one is plywood.

http://i325.photobucket.com/albums/k365/TerryLava/cape_ann3.jpg?t=1245097040

[James McMullen]

Caulk the joint if you are going to build the boat traditionally with a traditional solid lumber bottom.
(Of course, if you wanted an actual watertight bottom, you would have built the boat out of marine plywood with modern epoxy glued-lapstrake techniques. :p)

[Little River]

Terryll, Your Cape Ann Dory looks sweet!

Yes, I was worried about glued joint splitting the planks as well over time. I will do the traditional caulk joint.

Thanks to all for the input.

[nedL]

Splined or shiplapped, dry - no glue. Let it move.

[Daniel Noyes]

Caulk the joint if you are going to build the boat traditionally with a traditional solid lumber bottom.
(Of course, if you wanted an actual watertight bottom, you would have built the boat out of marine plywood with modern epoxy glued-lapstrake techniques. :p)

Yeah if you are going with a traditional build start that way, other wise might as well close the boat shop, get out the icing bags and start frosting a cake... err, I mean building a glued lapstrake boat!

for a dory bottom on the North Shore of Mass bottom planks were tight fit on the inside with one of the two planks at each joint having a 5 degree bevel which left room for a thread of cotton on the out side.
Make sure your planks a put on to cup inward toward the frames and cleats.
Dan
http://dansdories.googlepages.com

[James McMullen]

I was teasing, Dan. I build both kinds of boats.

[Daniel Noyes]

I know

I build both kinds too...unfortunately :)