Friday, June 1, 2018

Drilling the keel and transom knee

Soon, it will be time to attach the keel to the frames. 

That will involve bolting the keel to the stem, bolting the transom knee to the transom, and finally — bolting the keel to the transom knee.

This week I ordered the bronze carriage bolts from Glen-L, as well as some more epoxy since I'm almost out. Glen-L is currently in the middle of the company's first-ever move from their original 1953 building into a new facility in San Clemente, CA. That's a pretty big undertaking, so it's understandable if there turns out to be a little delay.

Meanwhile, I've started drilling the holes for those carriage bolts. It sounds simpler than it really is.

Let's take a look at the transom knee first.

In order to drill the holes as straight as possible, and on the centerline, I decided to use my drill press instead of a hand drill. This will also keep the holes at a 90° angle to the knee's flat contact surfaces.

Here's the complication. My drill press has a two-inch travel, which is not enough to go all the way through the knee. Not impossible, but I had to get creative to make this work. 

First, I started with a small drill bit for the pilot hole. In order to keep the hole as clean as possible, I used progressively larger-diameter drill bits to enlarge the hole toward my goal of 1/4". None of these initial drill bits went all the way through.

Finally, it was time to run a 3/16" bit all the way through the knee. The problem was, how? The bit itself was long enough, but the two-inch travel wasn't. 

I drilled the 3/16 as far as it would go. Then, I loosened the chuck and pushed the bit as far upward as I could and tightened it in place temporarily.

Then, I raised the table of the drill press as high as I could & still get the knee under the drill bit. With the knee in place, I loosened the chuck, and pushed the drill bit downward into the hole. I re-tightened the chuck, held the knee firmly in place, and turned the drill press on. 

Thankfully, it didn't bind and spin the knee right out of my hand.

With the drill press running, I finished drilling the hole all the way through the knee. Of course, I had to do all this in reverse in order to move the knee for the next hole. Then, I had to repeat the whole process for the other 3 holes. 

Then, all over again with the 1/4" bit. 

Time-consuming, but it worked. At one point, the drill bit ran into one of the bronze screws holding the knee together. I was concerned that might happen. Fortunately, the drill bit cut right through the softer bronze, and little shavings came flying out of the hole along with the sawdust.

Now, for the other end of the keel.

I started by drawing the centerline on the keel, and lining it up with the centerline of the stem. Then I clamped the entire keel into place, end-to-end.

Since the stem is now permanently attached to Frame 5-1/2, I had no choice but to use a hand drill. The challenge was finding a way to drill straight downward through the centerline so that the hole was centered and straight.

To help with this, I took a block of scrap wood that was roughly square, and close to the same width as the keel. I marked the centerline on this piece, then drilled a pilot hole through it with my drill press. This would be my drilling template.

I aligned the centerline of the template on the centerline of the keel, and clamped it firmly into position. Then, I drilled downward through the template, through the keel, and into the stem.

After I drilled two pilot holes using the template, I removed it. The full length of the keel was still clamped firmly into place.

As I did with the transom knee, I used increasingly larger drill bits in the hand drill until I had 1/4" holes all the way through. The resulting holes weren't perfectly on the centerline on the other side of the stem, but they were close.

The next step was to fit the transom knee.

I clamped it into place, firmly pressed against the keel and the transom.

The fitting was really good against the keel, as well as the bottom frame member of the transom. However...

The fitting against the motor board wasn't so good. Apparently, the motor board is thinner at the top than it is at the bottom, leaving a wedge-shaped gap.

Time, once again, to make another shim.

After a lot of careful sanding on a scrap strip of mahogany, I had a thin and long wedge-shaped shim.

After some meticulous fitting, re-fitting, and more sanding, it fit into the gap nicely. 

The next step will be to trim the shim and epoxy it to the knee.

No comments:

Post a Comment