What joint to use in bulkheads??

2 total or 2 per hull?

 

2 per hull.

 

Thanks. Will talk later. Off to do stuff for a while.

 

Here's a picture of the Payson Butt Joint in real life:

 

It looks very strong. Good job.

 

We’re talking about a bulkhead here. You don’t need the kind of resistance to every conceivable form of stress that you need in the skin. It just sits there, attached around its etnire circumference to the hull, subjected to compressive forces at the most, unless it forms part of a buoyancy chamber. Don't over-think it.

 

Agreed. I just needed something easier than a scarf (i already cut for a butt). I also wanted a flat surface because this is finish work.

 

Biscuits

 

Seems like we're down to beating a dead horse here; apparently what cat's doing is working just fine.

 

Also true, Troy. The bulkheads don't need too much strength, but they need to be as strong as the surrounding plywood in case anyone falls into them. Probably stick with the Paysons because they are quick, easy and can take someone falling on them.

 

Cool joint!

Did you grind out the bevel, or power plane them?

 

The Payson butt joint is well covered on the net. I've posted here on several occasions, as well as others. Terry biscuits don't hold anything, they just maintain alignment. In fact they rely on the biscuit swelling from water based glues to work properly. This is fine with PVA's and the like, but worthless with epoxy.

Zack, the Payson butt joint can be made with a bevel or ground out. It doesn't really matter, so long as there is sufficient material (read thickened epoxy and fabric) for the thickness of the pieces being joined. The width of the joint is important too. 6:1 will work, though is a bit "steep". I use the eyeball method which usually works out in the 10 or 12:1 range on each side of the butt. So, a 1/4" plywood butt joint would have a 5" wide scalloped out area. The ideal joint has 1/2 to 2/3's the joined pieces thickness removed for the filling materials (1/4 to 1/3 per side of course).

 

I used a power planer and boy, was it fast! I did two bulkheads (using fast epoxy, phenolic microballoons and colloidal silica) in about an hour. They were fully set up by the next morning and were installed at that time.

I started by grinding, but I realized I was about to make the place very dusty. The planer worked better because it just left shavings.

Thanks, PAR.

I think I did 6:1 or whatever was shown in the diagram PAR had put up on the site originally. Since this is a bulkhead I didn't feel it needed anything more than 6:1.

 

Picture?!

 

Microballoons makes for a lousy adhesive mixture. When mixing up an adhesive mix, always use a "fibrous" material, such as wood flour, cotton flock (West 403), calcium metacilicate (West 404), cab-o-sil or milled fibers. Balloons, be they phenol, quartz or 'glass don't have much surface area, which is why they're easy to sand and also why they truly suck as a adhesive reinforcement.