Best way to join two plys when making a stringer??

[Darren Nemeth]

I have my stringers cut for the Batboat and coated with polyester resin.

The longest of the two originals I pulled out of the boat are 12 foot and my ply is 8 foot long so I had to cut them out in two parts. One section is 8 foot and the other 4 foot. Both have about 4 inches overlap.

What is the best way to join these two plys together??

Can I fiberglass and stainless steel screw these overlaps together? The first picture shows what I am talking about. Or do I need to cut them?

The second picture shows how Glastron originally joined the stringer sections.

Which of the three illustrated below is the best or is there a better way?

 

[TheWoodCrafter]

Re: Best way to join two plys when making a stringer??

The proper way to join 2 pieces is a scarf joint.
You taper the piece about 7" to a sharp edge. You do the same to the other piece but on the opposite side. This gives a lot of glue surface.

 

[Darren Nemeth]

Re: Best way to join two plys when making a stringer??

The proper way to join 2 pieces is a scarf joint.
You taper the piece about 7" to a sharp edge. You do the same to the other piece but on the opposite side. This gives a lot of glue surface.

Like this?

 

[fishrdan]

Re: Best way to join two plys when making a stringer??

Nope, on the face of the board, the wide part of the board, not the edge of the board.

Instead of tapering the scarf joint (which is best, but difficult to cut) you can also cut the joint area of the 2 pieces to 1/2 the board thickness, then glue them together. Kind of like to huge rabbet joint.

 

[TheWoodCrafter]

Re: Best way to join two plys when making a stringer??

Nope, on the face of the board, the wide part of the board, not the edge of the board.

Instead of tapering the scarf joint (which is best, but difficult to cut) you can also cut the joint area of the 2 pieces to 1/2 the board thickness, then glue them together. Kind of like to huge rabbet joint.

Face to face, right.

Lap joint is the next best thing.

 

[Mark42]

Re: Best way to join two plys when making a stringer??

Seeing as you alreay have the stringers cut, lose the 4" overlap by removing 4" from one piece of the stringer. Then cut two 24"x7" pieces and sandwitch the two stringer pieces between. Epoxy and screw or use water proof wood glue and screw.

Since the stringer is only 12 feet long, you don't really need a high tech joint, just a strong one. This joint will outlive the boat.

 

[Darren Nemeth]

Re: Best way to join two plys when making a stringer??

okay. thanks .

 

[drewpster]

Re: Best way to join two plys when making a stringer??

I agree with Mark, a scarf joint is best if a single long board is needed for aesthetic reasons or if there is no room. Since the structure is unseen a "sandwich" like Mark suggests will outlast the boat. I would use epoxy to glue up the joint then cover everything with poly and glass.