I think Renn has you build the forward sheer deck at this point, but I haven't used my 3D CAD model to design my cuddy and cabin yet, so I decided to go ahead with the interior components of the cuddy ...starting with the f'w'd flotation tank / collision chamber. The flotation chamber is made from the several components: the 'doubler' as Renn calls it, the aft bulkhead, a 2-part deck (top), a 'stirrup' to carry a support beam, and the support beam for the decking. The doubler reinforces the top 2/3rds of the aft bulkhead and also (with the 'stirrup') carries the aft end of the support beam.

Since I do have the 3D CAD model that I developed for my boat, I skipped a couple of Renn's fitting steps and let the computer loft the aft bulkhead. From this lofting, I rough-cut a template piece from 1/4" hardboard. With Renn's "frog" (not shown) to hold it, I used clamps to hold the template in place. The hull form was transferred to the template as Renn describes. You slide the little block of wood along the hull and use it (top edge) to guide your pen on the template. To mark the shape onto the wood that will go in the boat, you just clamp the template onto your ply, reverse the block, then follow the line on the template to make marks on your ply.

PS: I finished the doubler just as I was running out of shop time, so rather than hold it in place with screws like Renn suggests, I went ahead and installed it with epoxy. I'll need to coat it well before I install the rest of the components (no problem.)

With the center support beam fit and level, I marked where it went and glued it in. To glue in the top pieces, I marked the hull with a felt pen so I'd know where their top surfaces were, then I just ran a medium bead of epoxy along the hull (and top of aft bulkhead and support beam) to get ready. Then I ran a medium bead on the lower edge of the top pieces where they'd meet the hull so that the hull and top piece beads would squish into each other when the top was installed. Finishing up was just a matter of filleting all the seams, filling the minor gap between the two top pieces, then putting 9-oz by 4" glass tape on all the seams. On the aft bulkhead, I only tabbed-in the inside and outside sections between the stringers and didn't bother with the outboard sections. I'm ...pretty sure... this is what Renn said was OK.

Notice the hole on the starboard top piece for my 8" Bomar deck plate that will go there. Since my stainless screws would 'barely' poke through the 1/2" ply that I used, I went ahead and made a 1/4" thick doubler ring (installed on the underside of the top piece around the deck plate hole). It's hard to inspect inside this chamber, so I figured a bit of caution on making things waterproof now would safe headaches later.