Wednesday, September 1, 2010

Head Scratched - Protection Added

After some discussions with my fellow boat builder Ted, it would appear that the side wood strips at the rear of several boats like ours have been added not necessarily as splash rails but as protection against bumps. The shape of the side of our boats at the rear makes bottom edge of the boat prominent and susceptible to getting bumped and marred. A rubstrip along the shearline would be ineffective at the rear. However, since the boat side twists, getting something to fit takes a bit of head scratching.

I decided to build some stationary assists for fitting these bumper strips. I used the 2x6's from the forms and cut vertical pieces at the planned front and rear height and connected with a stringer at floor level. I then split them in half on the table saw so I could make one for each side of the boat. They were attached to the ping-pong table and then belt clamped underneath the boat to bring the verticals tight to the boat.

A 2" wide board was cut to rough length and placed up to the side of the boat. It was placed so it gapped about 3/8" at the front and a like amount at the rear. Then using a scrap piece of wood about 1/4" thick and 1 1/2" square, I sanded a chisel edge so it would ride up against the boat along the board. I drilled a small hole 3/8" in from the edge to allow a pencil point to project through. I laid this piece flat on the board and pushed it up against the boat side and traced a line on top of the board, and then repeated this on the underneath side.

I then took the board to the band saw and cut a line in from the edge every four inches and rotate it as needed to cut to the marked lines top and bottom. Then I set the band saw table to the initial angle needed and cut off four inches at a time and readjusted the table angle as I went along. This cut a spiral shaped surface along a curved line of sorts. Then a trial fit and some filing - some more filing - sanding - filing - and it got close to fitting - sort of.

Then duct tape was put on the side of the boat so epoxy would not adhere. Some scraps were put underneath with more duct tape to catch any epoxy drips. A batch of well thickened epoxy using the brown fairing filler was put on the board and clamped to the boat and allowed to cure. It took some mallet hits to get the board lose after cure but it appears to now have a surface that matches the boat. Filing of top and bottom sides of the board should clean up the excess epoxy.

This last picture shows the epoxied surface, which is now a curved line with a spiral twist - you can kind of see that in the photo.

I'll do the other side and then determine the final shape or line to cut the outside of the board. It will probably end up being a straight taper - narrow at the front and gradually getting wider toward the rear of the boat. I decided to reinforce the sides at each screw attachment point with another piece of 1/4" plywood. To keep it simple and light, a flycutter was used to cut some 1.5" diameter "washers" from 1/4" plywood. These were epoxied in place on the inside of the boat and held in place with a screw and a temporary duct taped block on the outside of the boat. I am not going to permanently attach these rails until the boat is out of the basement. Hate to add any unaccounted for width.

After a bit a trying different lines, a straight line did not work as it made the forward foot or so look like it bulged out due to the shape of the boat side. So I used a strip of plywood to create a curved line and cut it on the band saw and sanded out the bumps and saw lines it until I had a smooth surface.

I plan on putting a 1/2" or 2/4" wide stainless steel rubstrip along the outer edge.

1 comment:

  1. Art, attaching my splashrails was probably the most difficult task in building my boat just for the reason you're pointing out; nothing to clamp the wood to while bending. Your system looks pretty good, though like many of the tasks involved in boatbuilding, it's tedious and time consuming.

    In the end, I drilled holes in the splashrail and corresponding holes in the shear, then inserted long threaded rods between the two and tightened the nuts on each side to pull the splashrail flush with the hull.