Saturday, February 24, 2018

Sportfisherman 26 - Let the Skin Begin

Since my last post on Kevin Agee's project the 2nd and 3rd layers of the sheer clamps have been laminated onto the first one, to take it up to its full size. These layers were easier to do because the first layer was already in place, defining the twist and giving a convenient surface for clamping. There was no need for a Spanish windlass to pull them in.
Second layer of sheer clamp glued and clamped.
The 2nd layer of the bottom skin has also been glued on. It is secured and pulled in tight with temporary screws and fender washers, working outward from the centre of each sheet toward the edges, forcing air and excess glue out at the edges. A boat like this will sometimes take some hard hits on the bottom when running into rough conditions, so bad lamination in the bottom must be avoided. The screws will be removed and the holes filled with epoxy, inserted with a syringe.
2nd Layer of the bottom glued and fastened with temporary screws and fender washers.
Time was approaching for the side skin to be started. This is being done in bead and cove cedar that was bought in 4" plank widths, then cut down to the desired widths on a table saw. After scarphing to the lengths needed to cover the hull in single lengths, they were run through the router on a router table to form the cove and bead. This was done with a crown molding #3 router bit, using the convex part of it for the cove and the concave part of it for the bead. The two fit together nicely for the bead and cove joint.
Crown molding #3 router bit sourced from Lee Valley.
Fit of the bead and cove strips cut with the router bit shown above.
With a large stock of newly-machined strips scarphed into long lengths and waiting on top of the hull, the pressure was on me to finish shaping the bevels on the stem to to the correct angles to receive the ends of the strips. This is done by holding (clamping if there aren't helping hands available) a strip against the sides of the bulkheads and frames, with the forward end in correct position to run fair into the stem and with the tip just short of the stem. Then a saw cut is made into the stem with the saw running against the upper face of the strip until the teeth are flush and parallel with the inner edge of the strip. This is repeated in a series of positions until representative cuts have been made the full length of the stem where it will be crossed by strips.
The stem is still rectangular in section but has saw cuts to show the bevel angle needed by the skin.
Next, the bulk of the timber is taken out with a chisel to give the rough surface , finished off to the final surface with a plane and/or a Shinto saw rasp.
Using a chisel to remove the bulk of the excess wood. This side of the stem proved tough to break out due to the grain direction, the other side came out much more cleanly. This side needed the Shinto saw rasp to finish it, whereas the other side came in nicely with a plane.
The completed stem bevels, ready for the bead and cove strips.
A decision has to be made by each boat builder where to place that first strip. Some like to start at the chine, then work toward the sheer. Others prefer to start at the sheer and work toward the chine. Still others will start somewhere between the two and work in both directions. This third option was our choice, mostly because the boat has a broken sheer that gives a convenient start line.

We started by clamping the strip with the lower edge flush with the lower edge of the straight aft sheer clamp. Forward of that aft sheer clamp, we slid the forward part of the strip up and down against the framing until we found the line that placed the least stress on the strip. In that position there is minimal force needed to pull the strip against the framing, so fitting is easy and the same should also be true for the rest of the skin.
The first strip glued flush along the lower edge of the aft sheer clamp and the forward part aligned for least stress in the timber.
Starting to look good, with six strips fitted. The strips are run past the ends of the hull, then trimmed back after the epoxy has set.
The strips are nailed to each other with plastic brads that are shot in with a pneumatic gun. Temporary screws and fender washers are holding them to the framing. Due to the low-stress alignment chosen for the strips, hand pressure was all that was needed to hold each strip against the previous one for fastening, no clamps were needed.
With much of the hull skinned both sides, time to stop. The chine flat must be built first from Douglas fir, then the side strips will be finished against the chine.
Scarph joints in the strips to make hull-length strips. The strips are positioned to spread the scarph joints out so that they are not all in the same place on the boat.
Building the chine step will be next, on the program for tomorrow.

This design is not yet complete, so is not on our pricelist or website. See previous posts on this blog about the 26ft Sportfisherman for more info. See our full range of designs on our main website or our mobile website.