Tuesday, February 23, 2010

Fairing the Frames and Longitudinals

The process of beveling and smoothing all the surfaces that the plywood "skin" mates to is called fairing. It is inherently a bit confusing to the new boat builder as its hard to know where to start, what tools to use, and how much material to remove.

The picture shows the tools I ended up using from top to bottom in the picture: 1) power 3 1/4" hand planer, 2) small belt sander Porter-Cable 2 1/2"X 14", 3) 1" Stanley hand plane, 4) 8" Jack plane, 5) Rasp, 6) Disston Abrader, 7) Long sander (made from 1/4" scrap wood to fit a 3x21 belt from a belt sander).

After filing some notches at the frames to set the angle of the longitudinal pieces, the major wood removal starts to blend the shapes from one spot to the next along the longitudinal pieces. I found the power planer a bit aggressive and hard to see what was happening until after a pass was made. The hand planes turned out to be quite effective at removing material quickly on the curved surfaces. They were a pleasure to use since they are quiet and they allow the surface to be seen as you work which is reassuring . The small Porter-Cable power sander was a great tool as the vacuum pick-up removed the dust effectively and it was fairly easy to see what was being removed. It was great for putting the contour on the frames.

The bottom piece on the right side of this picture is called the shear. It has not been faired yet and is still a square section. The idea is to angle it so the outer surface points towards the member above it (the chine). The trick is that the angle is constantly changing and it turned out that my chine surface was not sufficiently angled to have a prayer of getting a piece of plywood to lay on it and the shear at the same time. So the chine had a couple more laminations of material added to get the bottom angled out enough to "point" towards the shear below it.

In this picture, the bottom piece (shear) is faired so that its surface points toward the chine above. This area of the boat probably took the most time as quite a bit of wood needed to be removed. You can see a lot of plane shavings and dust on the floor.
I think I'm done with fairing, but it seems to be a task that could be done to infinity because with every new look it appears that a surface could be sweetened a little more. I think its good enough to move on and I'll fix something if I see the need as I prepare the plywood planking pieces.

Friday, February 12, 2010

Chines Part II

After completing the shears, I went back to the chines. Since I had ripped my original 3/4" thick material into two layers, the total thickness was only about 5/8". So I decided to make a mahogany sandwich and add in a 1/8" layer in the middle. So I cut an 8' board to the width of the chine (1 3/4") and then resawed into 1/8" thick pieces on the tablesaw. Since the rough chine length is about 12', I used 8' length towards the front of the boat, put a 45 degree mitre on the end and mated it to another piece long enough to complete the whole length. The middle layer was thin enough to bend to whatever shape needed. The pieces were all epoxied together on the frames using just about every clamp I could find in my shop. The grand total was 90 clamps for each chine lamination. Since I did not have 180 clamps, I could only do one at a time.

After completing the lamination on both chines, the epoxy squeeze out was planed off with a hand plane. I found this easiest to do in my shop with the chine in a vice and moved it along in the vice as I progressed. Then the chines were fit to the boat, epoxied and screwed into place. After all the consternation about the fit to the stem, the chine ended up looking too straight in the forward area and without enough twist so it did not angle nicely toward the shear. I ended up making a long tapered section piece about 3/8" thick at the bottom and 1/8" at the top and laminated it onto the chine from stem to about 8" forward of the frame. Using the small belt sander, it was blended into the chine.

Bending the Shears

The first step to the shears was getting the length down to about 18" longer than what I measured to be required. Since the fit of the shear to the breasthook is a set angle, I cut some scrap material on my mitre saw until I got it right and then cut an angle on the front of each piece to mate with the breasthook. The four shear pieces (two layers each) were then soaked in the stairwell soaking tube for a couple of days.

I worked on the one side of the boat where I had the most room between the boat and the wall. To support the shear while bending into place, I clamped long boards to the form or the frames over to the wall, just below the level where the shears would meet the frames. This provided a resting place for the shear while bending into place. I then wrapped a bath towel around the shear along the area of the stem and another in the area between the front and middle frame. I then poured hot tap water over the towels (buckets underneath).

To start the bend into the breasthook, a 24" Bessy bar clamp was clamped to the shear to provide leverage and the leading end was bent while the remaining length of the shear pushed up against the wall about 3' away from the boat. After shoving it into place and the breasthook clamp board squezzed tight, the rest of the bending took place at the rear end of the boat. A pipe clamp was put on the shear near the transom and used to gradually bring the shear towards the boat. After pouring another pitcher of hot tap water on the towels, the shears were gradually moved into place up against the frames and clamped in place. Towels were removed and the shear left to dry. After a day of drying, the first shear was removed and moved to the other side of the boat where I did not have as much room to work. I repeated the process for the next two shear pieces. Unfortunately I did not take any pictures during this process.

While pulling the third shear piece into place, I heard a loud crack and looked up to see a distinct sharp angle forming inside the towel, just aft of the breasthook. Another crack or two later and several expletives, the break was complete. I backed off on the bending process because this shear was toast. I removed the towels, the clamps, and put the shear aside for later analysis. I grabbed the last shear piece out of the soaking tube and bent it into place without incident. Analysis of the broken shear showed a severe grain run-out in the area. I thought I selected all pieces to put the staightest grain towards the front of the boat, but I got this piece backwards. I decided to make a scarf cut in the broken area and mend this piece back together putting the scarf joint at the back of the boat. After the piece dried, I made a jig for my chop saw and made about a 5" long scarf joint in the shear and epoxied that sucker back together. After curing, joint clean-up, soaking and bending, I was back on track with all four shears bent.

Prior to gluing the first layer of shears to the frames, I made a mid bow area temporary "spreader board" to ensure the contour was similar on both sides. One side measured wider from centerline and the curve did not look as smooth as the other. The way my stem support was made, I had a level surface to center and mount this board. The first layer of shears was glued to the breasthook and frames using clamps to the temporary spreader to force the curve in place on the one side. Then the second layer was epoxied to the first layer and clamped into place. Screws were only used in the breasthook.

Thursday, February 4, 2010

Chines - Part I

After learning of Ted's broken chine when attempting the bend, I decided to laminate the chines to make for easy bending. So I cut my chine material to rough length, about 12', and then ripped them to 3/8" thick. The cutoff pieces were about 1/4+" thick. I then soaked all four pieces in the 4" soaking pipe, stem end first, for a couple of days to noodle them up a bit.

I borrowed the soaking pipe from Ted. By hanging it in the stairwell, it can be loaded with long pieces of wood, filled with water and not get in anybody's way. Also, it's a lot easier to keep the water in it if it's not horizontal.

After soaking, the chine material was put on the boat and bent into place. The two layers of thin material bent easily into position on the frames and up against the stem. They were left to dry for a couple of days while I did other things like work for a living.

When it came time to figure out how to fit the chines at the stem, I decided that without having the shears in place, it was hard to judge how much twist to put into them. I decided that procrastination was a good approach to the question, and bending and installing the shears first might answer the question or provide enough time to figure it out.

The picture shows the chines held in place and the one layer of the shears bent and clamped in place. On the left is a previously bent shear just resting in place waiting for the glue-up to take place.