Saturday, February 22, 2014

B3 hatch openings cut and backing plates installed

After completing the installation of bulkheads 4 through 7, the next order of business is to install B1 - B3.   However, I wanted to install access hatches in B3, and decided I should do that before installing the bulkhead, as it's much easier to work on now.

I needed to cut out the hatches, manufacture a backing plate for the hatch to seal against, and make hatch stiffeners to reinforce the hatch itself.  I decided to make a router template to make all the cuts.

First I did some paperwork to figure out the template spacer diameters I would need.  I used a 1/8" bit to cut out the hatch, a 1/4" diameter bit to cut the groove for the gasket, and a 1/2" bit to cut the inner rim of the backing plate.

With dimensions in hand I moved to the lathe to cut out the spacers.  I used a template guide with no spacer for the first cut, so just needed to create two.  I used 1/4 aluminum.  In the photo above you can see dimples on the spacer where I hit it with a ball pein hammer to snug up the inner diameter.

I then drew out the template.  The opening size I decided on was 12" x 18", and I needed a line outside that to account for the first template guide.  I then cut out the template with a jig saw, and smoothed it with spokeshave and drum sander.

Then clamped the template to B3, took a deep breath, and cut out the hatches.

As I was cutting out the backing plates, I realized I could also cut the hatch stiffeners from the same piece of ply, using the same template, by making a big spacer (about 6" diameter).  I cut that spacer out of plywood, and it worked fine.

 After cutting out the backing plates, I checked for fit.  Looks about right.

Next I laminated the hatch stiffeners.  I am using two layers of 1/4" baltic birch plywood.  Nice wood.  I would have bought 1/2" thick if it was available.

And then laminated the backing plates.

After cleaning up the glue squeeze out, rounding over the edges, and an overall sanding, I 
installed the backing plates in the bulkhead and cleaned up the glue squeeze-out.  

I had to clampea board across the bulkhead to keep it from sagging from the weight of the clamps!

Nice to have that job done.  There will be a little followup work on these to coat with epoxy, but I can do that after the bulkhead is in the boat.

I'll be able to use this same technique for the seat-top hatches and the cockpit sole hatches.  I can use the same router bits and template spacers, I'll just need to make a new template for different sized hatches.  Should go a lot quicker next time.


  1. Dave, What kept the router from veering off when cutting the inside opening in template BH3 shown above in the fourth photo from the top in this post? Just trying to understand how to do this. Also, where do the router spacers mount under the router? I've never done this type of work, so I'm a little lost. Brent

    1. Brent - right - the template guides only one side of the cut, and there's nothing keeping you from running wild into the inside of the template, so that's a little scary. The secret is in the direction of cut. If you go one way, the action of the router bit tends to keep you pressed against the template. If you go the other way, it tends to climb away from the template, and that's bad. So pay attention to that!

      Notice that I'm not saying which way to go right here, in case I remember it wrong. But look at which way the bit rotates and it's not hard to figure out. You want to move in the direction where the bit is cutting away from the template, thus forcing the tool toward the template.

      In response to another comment, I have just added a couple photos showing how the template guide mounds on the router base of my router, and you can see that at:

      Hope that helps. -- Dave