Sunday, February 15, 2015

Rudder hardware alignment

The block of laminated plywood shown below, which I call the rudder head, attaches to the transom of the boat and connects the tiller (steering handle) with the rudder.  I've previously detailed the construction of this part and that post is < here >

I have had the hardware (pintles and gudgeons) that attach this to the boat on hand for some time, and recently went ahead and took the time to get them installed.

Because the rudder head is somewhat thicker than the cast bronze hardware, I needed to carve out recesses.  I marked out the outlines and started trimming away with a chisel.

After some work and repeated fittings the bottom part is in place. That wasn't so bad.  

I debated for a while about just where to put the top fitting.  I wanted the separation between the two fittings to be as large as possible.  On the bottom one I had to avoid the recess where the rudder fits.  On the top one I had to make sure the mounting screws would not hit the haul line tubes which run inside. Once the location was decided, I carved away wood so the top fitting would fit.

I then mounted the corresponding parts to a piece of board and checked the fit.  I found that the rudder head did not slip smoothly onto the transom fittings, a sign of an alignment problem.

I thought for some time about how to check the alignment of parts.  Just eyeing things up didn't seem to be sufficient.  Since each half of the fitting has a part with a hole (the gudgeon), and one with a rod (the pintle). I hit upon the idea of putting a close-fitting rod through the gudgeon hole and checking the alignment with the pintle.  I went through my scrap supplies and found that I had an old aluminum arrow shaft that was the perfect size.  Putting this through the gudgeons showed up the alignment problem.

Now that I had a way to check my alignment accuracy I could take steps to get things lined up. Starting with the pintle that mounts on the transom, I put it on a surface plate (very flat surface), and used a taper gauge to check the height of the pin at each end.  I found that the pin was parallel to the surface plate and didn't need any work, so that was good.

Putting the arrow shaft through the gudgeon and doing a similar measurement, I found the rod was not parallel to the surface.  So I put the part in the vice and started filing off the high side.

Without too much effort I got the parts to align well.

With these parts aligned, I knew that if I could do a similar alignment on the rudder head half that my problem would be solved. 

Here's the setup for checking the alignment on the rudder head. 

In this case, adjustment was not so easy, as I had to carve away plywood to get things to line up, but eventually I got it pretty close. 

Mounting the transom half to a test board things now slid together pretty well.  

My next step was to figure out where on the transom to put the parts.  I drew a center line for left/right alignment, and then clamped the parts on and adjusted for vertical height.

I needed to make sure the tiller handle had clearance in the transom opening, and wanted to have my rudder uphaul/downhaul lines clear the edge.

Once I finalized the position I marked the heights of the parts, then removed the rudder head.  I again used the arrow to make sure the fittings were aligned, and drilled bolt holes.  I decided to install fiberglass patches on the inside of the transom to toughen up this surface and keep the nuts from digging in.

When I drilled the holes, I had a little chip-out, so I filled that (the white in the photo below) before applying the fiberglass patches. 

After the epoxy cured, I used a  scraper to taper down the edges, and then applied some fairing compound to blend them in. 

When that cures a little sanding should have this ready for paint.  It's nice to have these parts ready now to install.

1 comment:

  1. Dave,
    Excellent work here. As you know, I had to redo my first attempt at this step. It is rather difficult to get it second attempt went much better and moves friction free. Looks like you got it right the first time.