CNC core blocks for hull form and less filler in kerfs.
Hi guys just curious about your thoughts for a build technique.
Im day dreaming about building a 40ft multihull (proa) out of end-grain balsa. The traditional method of filling the kerfs with bog adds weight and is brittle at those points and require a fair bit of fairing.
As a alternative I'm looking at "knitting" the core.
Essentially I'll have a female frame/jig ( CNC cut frames and battens.
Then looking at using a CNC machine to cut core blocks of end grain Balsa (300mm X 300mm x30mm) the inside and outside surfaces machined to the hull surface and lap-joins with finger joints cut on the adjacent joining edges. A big puzzle. The frame/ jig is essentially for supporting the weight. Starting from the middle and working to the ends 1st to establish a center the blocks are glued in place, then repeating the process out to port/stb at the same time. This should make a Balsa hull form that's relatively accurate to its design. Then the inside will be laminated and bulkheads/ stringer's. Could possibly do the deck with temp stringers but for now ignoring the deck. The hull flip and outside skin laminate is pretty standard. The build would be in Indonesia ( I know they grow alot of Balsa, not sure how much of the manufacturing of end grain sheets is done there.
A 4x4 CNC machine will be used so multiple blocks can be cut at a time by cheap but trained Labour (I'm not slave master they will still be paid above and locked after).There will be alot of block's.
I'm aware that balsa dosnt like moisture and this will be mitigated.
Also ideally I would like to vacuum bag so if anyone has experience with vacuum banging Balsa core that isn't in a sealed mold I would like to hear ya thoughts could look at infusion. ATM I'm thinking of going above the gunnel. Having a strip of malone to bag onto and having a bag under the core to envelope, the glue getting on the bag going hard / sharp blobs would probably require the hull to be lifted ( pre glass) and a quick sand before placing the bag and the hull back down.
I'm also curious if the glued joins would be enough to make a acupuncture hull shape and strong enough to hold it.
The cut files will be outsourced to avoid inaccuracies.
Happy to hear the community's thoughts.
I have 3 years experience boatbuilding nearly 20 years ago, we made plugs- molds and infused foam core. So I have a little experience but understandably a big project.