Foam bulkhead fillets

[Figment]

Tim,

My own cockeyed attempt to use a trapezoidal foam cushion/fillet at the bulkhead edges is still fresh enough in my mind to give me good appreciation of the work you did on the Daysailor last week. Bravo!

Hot Glue!! DUH!! Why the heck didn't I think of that? That would've made my process a lot easier, particularly with regard to fitting to the overhead.

Side question... your bulkheads are cut flat at the sheer height, correct? What's your plan for infilling up to the deck/coachroof?

[dasein668]

Mike, I think that's an optical illusion in the photo. When I was at the barn during the templating phase, Tim and I talked about running the bulkheads wild so that the crown of the deck could be scribed onto the bulkhead at after the deck beams were in place. Since the crown of the deck isn't going to be too dramatic, I'm guessing he didn't run the bulkheads TOO wild.

On the other hand, maybe he changed the plan between Thursday and Friday!

[Dave, 397]

Those pre-cut trapezoids really do rock! Saves a ton of time making goofy fillets, for sure.

I will readily confess that I suck at bulkheads! Tick stick for me all the way! A good friend of mine who unfortunately for me has moved some distance away, is a wood-boat resto guy...makes these partial templates, holds his mouth just so, and starts cutting...and they always fit perfectly!
Drives me nuts!

One variation on the foam trapezoid fillets, is that my buddy glues them to the bulkhead itself before putting it in place...the bulkhead does indeed have to be a perfect scribe to do that, but it makes the whole affair even slicker if a guy can do that. I sure can't!

Neat deal, for sure!

Dave

[Tim]

Side question... your bulkheads are cut flat at the sheer height, correct? What's your plan for infilling up to the deck/coachroof?

The two small bulkheads are actually run slightly wild above the eventual deck line. In this particular case, the bulkheads do not need to extend much beyond the side of the hull, since they do not extend inside the shelter cabin. The end point on the bulkheads--the inside vertical cut--represents the deck edge, where a carlin will be installed signaling the beginning of the trunk and cockpit. Each of these bulkheads is a few inches higher than the side of the hull, to allow for a probable 5 degree (or so) deck angle, in as far as the 21" width of the deck at that exact point. There's plenty of extra bulkhead at the moment to accommodate even double that deck angle, if I wanted.

The bulkhead I built today is a monster--full width (over 8'), full depth, and extending, for now, nearly 2' above the deck edge. This bulkhead, located 4' aft of the chainplate bulkheads, represents the aft end of the cabin and forward end of the cockpit, and will eventually form the basis for the aft cabin bulkhead. Hence the need to run it so high. I went higher than needed to be safe, and to allow plenty of room to visualize what my actual cabin height and shape will be.

One variation on the foam trapezoid fillets, is that my buddy glues them to the bulkhead itself before putting it in place

That would work fine too, though for me I think it's more convenient to glue them to the hull, since it helps align the bulkhead when wrestling it into place. I think I would damage the foam on the larger bulkheads if it were glued to the edge first, since I work alone despite the large size of some of the pieces. Working alone requires resting large sheets of plywood on too many adjacent surfaces, so I'd worry about ripping the foam up.

Another cool idea I saw on another website, and which I had originally hoped to copy, was to bullnose the bulkhead edges and to rout a cove into the foam fillet. Then the two fit very nicely together, with the cove making up for any slight variations in the hull or bulkhead. Neat idea, but frankly, I simply couldn't be bothered when push came to shove. I'll save that idea for my next "real" boat.

[JetStream]

Tim,
Maybe a dumb question, but what do you use for foam? There are so many variations in material and compression strength that I have been at a loss.

[Tim]

I think you can use just about anything, really. Airex, Corecell, any of the higher-tech foam products, whatever's lying around. Mine is blue insulation board--decidedly low tech. Obviously some foams are stronger than others, and for highly compressive loads that could be important. For your run of the mill bulkhead, I think the tabbing is more than strong enough that the foam becomes essentially irrelevant once all the tabbing is in place.

Besides cushioning the bulkhead from the hull, one of the most important things the foam does in this application is spread the loads over a wider area. And the tabbing is very strong because of the gentle angles of the fillets.