I figure two on the outside and one on the inside is usually plenty. If you think about it, I'll be bending 16 foot panels only 12 inches ( half the beam) over that length. Not really much in the way of strain.
I didn’t start using glass on a butt splice until the last boat. It broke while I was making it, and I went back to covering each butt splice with a 2” wide piece of plywood. An ounce heavier, and more reassuring to me.
I recognize that a couple of layers of glass on a butt splice is strong, and probably strong enough. But for only a few ounces more, this (overly?) cautious olde farte wanted something stronger than just enough. Here, in the glacially originated Great Lakes region, there are rocks. LOTS of rocks. And most of them come fully equipped with sharp edges.
Not real hard to run right up onto one of those sharp pivot-point producing rocks. Much like a python, they lie quietly waiting. A rounded rock makes a larger pivot point, and a boat can slide back off of it. But - a broken rock makes a pointed pivot point. Being smaller, the pounds per square inch (psi) are greatly increased. The point digs in and just won’t let go. Any movement in the boat makes it dig in deeper - and cause even more damage.
if - when - one of these just happens to dig into a splice, I want to be able to depend on hull integtity. Probably will never happen, and probably not needed. But, there’s a difference between “probability”and “certainty”.
I used a big honkin 6” wide piece of 3/8” ply on the pirogue I built 13 years ago. Plenty strong. On this one, there will be a gunnel, a chime log and 3 layers of glass protecting that joint. I’d guess that is more than enough.
There’s a concept on joints, glued, nailed, stapled, sewn (as like a piece of cloth), wired, etc etc. All joints make the original structure heavier, weaker, or both. And, when bonding two items together, is the bonding joint itself (mating surfaces of materials) (A) stronger than, (B) as strong as, or (C) weaker than the parent material.
A test for joint strength is to tear apart the juncture. What breaks? Does (A) the joint itself remain intact, and parent material on both sides is torn apart? (B) Both the joint and parent material fail similarly? Or, (C) Parent material remains intact and the joint separates rather cleanly?
All in all, joints require an inordinate amount of attention per square inch compared to stuff around them.
Trial run. So far it looks pretty good. Still right at 25" bottom, still 25 degree flair and 1 1/2" rocker.....front and rear. I still have to play around with the bottom shape....maybe a little fuller towards the ends. Maybe put a rib front and rear to splay out the flair towards the ends also.
Looking very nice. Your fiber glassed butt splices looks good. Sometimes if a board/plywood is used for a backing it can cause a problem with the sides not bending into a fare curve. If you want the extra strength of the wooden backing like Jack, the splice could be placed so it lands on a rib or brace. A good idea is to have the floor splices not line up with the side splices.
I had this really wild idea about the butt splices. Instead of trying to hide them, why not celebrate and call attention to them. How about a row of painted on stitches up the butt splice seam... XXXXXXXX. And maybe a row of X's going down and around both stems........like the boat actually was stitched together? I'll bet that would be an attention grabber!
I was going through my wood stash and found these. The pieces all came from one board on a beat up old pallet where I worked. It was gray and rough, but I saw some interesting things going on. I have no idea what kind of wood it is. I had sanded and put several coats of varnish on one of the pieces 5 years ago. I stashed the rest for a later time. From left to right: sanded and 5 coats of varnish.........just sanded and wet down........lightly sanded and wet down ..........and unsanded dry, like it came from the pallet.
Seriously considering working these pieces into my breasthooks.