Strip planking

Attaching temp bulkheads

Posted by Paul

I found that finishing the forebeam was harder than I thought. After much discussion with various people including Mike in Perth who is also building a 1230 bi rig cat single handed, I have decided to plough on and use my simple U bolt anchor bridle points. Mikes concern is that the outer seal of epoxy will no doubt crack with the stresses the shackles will come under in different directions with a cat swinging on it in the wind and tide at anchor and once the seal is broken salt water ingress is inevitable and even 316 stainless steel will corrode if there is a lack of oxygen around the stainless. I spoke with a few others with experience in stainless and boatbuilding and have decided that the corrosion will be slow enough as to not concern me but as a further safeguard there is another type of resin called Techniglue MPA20 I can use to seal the bolts into the beam that is a little more flexible and may not crack and therefore retain the seal. So until I get some of that resin I will hold off finishing the beam. But that wasn’t the real hold up. I found I couldn’t drill the holes for the U bolt into the 6mm 316 stainless straps that will back the timber blocks inside the beam. I blunted 2 bits and am still not through the first strap. I may have to take it to a metal mill to get the holes drilled. I even had to keep the drill bit wet to try to keep it cool. It didn’t make any difference! So I left the beam for later and got on with other stuff.

As I cut the temp bulkheads down to just the top corners that have the round hull to deck turn inside shape, I cut the rest of the 2 of the temps down into the sides of a set of steps. I cut the rest of the mdf into the steps but fearing that mdf although heavy and strong may not hold my weight I ran 70mm x 50mm rails under the centre of each step to be sure. I glued and screwed it together. It still had a little side to side movement so I attached a leg to the middle that ran past the top that I will clamp to the underside of the bridgedeck. Towards the end of the build when I raise the duckboard height and make the duckboard into a long compartment, I will need to raise the height of these steps but until then these will do.

I attached mdf blocks or tabs to the side and top of the temp bulkhead so that I have plates with which to attach the temp bulkhead in the hull, I can clamp it in place until I have it fully aligned, remember there are 5 different ways that the bulkhead can be out of alignment, then once exactly in place I can screw it to the hull and the hardwood scaffolding plank I have clamped to the bulkheads. I cant screw down into the edges of these bulkheads because they have the uni rope embedded in them and you cant break any of the uni strands with a screw or you severely weaken the rope. To get around this I will have blocks screwed into the side of the bulkhead, (screws below the uni rope) and I will be able to run screws through the strip planks into the mdf. I may also need a third attachment or bracing point, a leg from the inside bottom corner to the chamfer or bridgedeck. The positioning of the temp bulkheads whilst not structural or super critical is important to get right so that the shape that the bulkheads and temps create as a mold is the correct one and the whole thing is fair to the eye.

I have also run a pine 40mm x 16mm x 10 meter (smaller planks joined together) stringer along the centreline and I will strip plank to this temporary stringer. The hull to deck will not be glued to the boat yet, first it needs to be glassed inside and out, so the bulkheads, temp bulkheads, hull edges and the pine centreline mark will all have clear packing tape on them to stop any glue sticking to them. The only glue that will stick is the glue that attaches each strip to its neighbour. But before any glue comes out the entire section will be dry fitted as there will be many strips that will taper or finish shorter or longer than others. Once the entire side is planked then they can be removed one at a time and glued back in again. Then once they are all glued and set to each other, the panel comes off for glassing and goes back on with the glass wet to set.

Tomorrow I will strip down the duracore and perhaps dry fit the first planks. Very exciting. Then we will start to see the trademark hull turn that makes Schionning cats so recognisable and distinctive.

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