What joint to use in bulkheads??

Before proceeding, check with local supplier and see just what is available.

 

What stops the timber in your rabbet joint breaking across the grain?

At least with ply you get an 0* 90* orientation
And in easy thicknesses, no ripping down stock to suit

 

I'm going to have to agree with sabahcat here.

I was looking for something easier than a scarf that would take less time. Nothing seems as easy as just doing a scarf. When the designer said "gussets" that sounded easier so I figured id be able to do some kind of gusset butt joint.

I guess ill just scarf it in the morning.

I already cut for butt joining.

Can I do a double scarf with an insert of full thickness ply strip, where the strip has a couple mating scarf joints on it as well? As in... my bulkhead would have a V shaped valley with two scarfs in it, then I would lower a strip into that V shape, such that the strip has the matching V shape to lower in?

The idea there is to save wood because I cut for butting already and don't have the scarf overlap.required.

 

Cat, when we form a wall for concrete we stand the ply and add walers and strong backs. The waler transfers the load across the ply and controls deflection depending on spaceing. Bottem line is the ply is as strong at the joints as it is at mid point of the ply, deflection will be the same on a leval line between the walers. I would not be afraid of a but joint with ply running vert and biax, and stiffners , straingers , walers , what ever you want to call them running hor with biax tape. rick

 

Ditto. I also agree, but I think you meant splitting along the grain.

 

I agree with Sabahcat also. CatB if your trusting one scarf, you can trust two although you've increased your work in the joint, usually you would leave the scarfing allowance extra on the smaller piece & just fold it back over the larger piece on the scarf line, clamp & electric plane/hand plane off the steps- but you know that. All the best from Jeff.

 

How about just butting the pieces together, dishing the joints out a little with a disc grinder, then taping and epoxying them up flush again (a la Dynamite Payson)?

 

Remember----------------------------KISS---------------------------------

 

Ah yes
Like this here

in a thread started by catbuilder

(****, thats a big picture)

 

Dyno - mite!

I'll give that a try. Looks fast and flush.

 

Ive joined plywood using a biscuit jointer (easy to use and a good fence), using the jointer as a saw to make a hull lenght groove on both sheet's edges and inserting a right thickness ply strip to join the two. In a boat it makes sense to add FG tape over the seam.

That payson thing looks interesting, should work fine also. Just a bit more work.

Lurvio

 

Well you have seen it before

 

Sure have. PAR put it up a while back.

Doesn't mean i'll remember it 6 months later while in the middle of a build. Too many things too learn and think through to remember every tiny thing. Some stuff is bound to need reminding.

 

PAR offered the use of written instructions here.: http://www.boatdesign.net/forums/boat-building/how-do-you-scarf-12mm-ply-bulkheads-37001-2.html

 

Thanks for the reminder to where PAR had put up the Payson joint.

Here is the joint, all done and under some pressure. I used fast hardener today with 85F/ 29.4C degree temps already in the shop and highs of 93F/33.8C expected today. Should set up quick enough to do them both sequentially on top of each other. (both bulkheads stacked on top of each other) I only really have one good, level surface for this that I can trust.

The speed of setup is something I am thankful for, working in Florida. If you use fast, you can usually get stuff to be cured enough to move around in a matter of a couple hours. Pretty neat.

Once this single Payson sets up enough to work on top of, I'll go and do the other bulkhead (I only had two that required a joint owing to my long, slender hulls).

Thanks for the input and reminders.