Saturday, November 27, 2010

Gluing the bulkheads

We left the hull dry assembled overnight and began the epoxying of all the bulkheads this morning.  Rather than working hunched over on the floor we elevated the hull onto a sawhorse and a folding table.  This worked well and gave us easy access all around the bulkheads.  I noticed that a couple of the bulkheads somehow, despite all our precautions, crept up by about 1/8 of an inch during the dry fit.  This is not a big deal but it opened up the gap between the chinelog and bulkhead cutout making it look bad.  Because of the wedge shape of the bulkheads they really want to move up.  We repositioned the misbehaving bulkheads and screwed them back in place using new screw holes.  To epoxy everything together we started at the stem and removed the stem then each bulkhead, one at a time, smeared it with thickened epoxy then slid and screwed it back in place.  I was worried that this would be a nightmare with the hull sides spronging apart while I'm trying to drive screws into place with the screw gun slipping out of my epoxy coated hands.  It turned out much less traumatic than that.  Removing any one bulkhead does not cause the hull sides to move significantly and when they did, like at the transom, the ratchet straps prevented significant springback.

Hull blocked up off the floor, ready for epoxy.

Still have a couple ratchet straps from chine to chine to keep the hull sides from springing back too far when each bulkhead is removed for epoxy application.  This was not absolutely necessary but I was worried that some of the screws would strip out going back into the same holes in the soft cedar

My theory that a lot of the stress at the stem is relieved once all of the bulkheads are in place is proven by this picture.  I was pleasantly surprised that the hull sides did not spring far apart once the screws were removed.  In the picture above, the red clamp is holding the gunwhales from spreading further but there is very little tension on it.  The bottom of the stem is completely unclamped!  The two blue clamps are just holding the gunwhales to the hull sides.

Today Clamp Girl became Epoxy Vixen and helped tremendously by taping, mixing, squozing and generally getting into the thick of the assembly. 

The hull sides wanted to spring apart a bit too much for my liking, once the transom was unscrewed so we used two ratchet straps, top and bottom to keep things under control.

Total time to date: 201hrs


  1. Another question for you Simon. In retrospect, was pre-drilling the bulkhead screw holes worth it? Any idea how the bulkheads slipped overnight? I'm thinking of using the inwale spacers as anti-slip braces, at least for BH3. In fact, I'm thinking of gluing all the spacers in place in advance, so I can pre-coat the sides panels and the spacers before going 3D.

    My chinelog lumber is getting scarfed tonight. Then I'll rip it and glue it and epoxy the sides. I'm doing as much in 2D as I possibly can. I think I'm scared to go 3D...

  2. Dave, Hard to tell if pre-drilling was worth it since I have not assembled the boat without pre-drilling. I want to say that it helped because, as you now know, everything becomes a lot harder to align when smeared with epoxy. Having two screw points sticking out of the hull side and corresponding holes in the bulkhead framing worked pretty well. Remember that the squeezout hides your bulkhead alignment line or masking tape edge.

    I think the slippage happened due to the screws chewing through the ply a bit during tightening with a significant shearing force applied to them by the bulkhead wanting to move up.

    The only downside to installing the spacers in 2D, that I can think of, is that you can't use them to hide the gunwale clamping screws. I used a lot of them to pull the gunwales tight and fair the hull sides while the epoxy set. Using the spacer as a stop for the side arms is a great idea but it will only help you on the midseat bulkhead as the other sidearms are installed after the seat tops.

    Going 3D is really rewarding and not that hard other than that first bit where you have to coax the bow into shape. Dry fit till you are confident it will go together well.


  3. Correction, to hide the gunwale clamping screw holes not screws. There ain't no stinkin screws in this boat.