New Rudder for my Montgomery 17 #369 "PUFF"

tim@timtone.com

Late last season I was in my usual spot for recycling beer back to the lake when I noticed the wake or whatever you might call the movement of the water directly behind the rudder.

The wake was 'irregular' in it's shape and movement. Kind of undulating you might say. This caught my attention and I made a point of having a much closer look at the shape of the rudder when I had the boat back on the trailer.
The effective area of the rudder (under the water) was shaped in a very non symmetrical and warped way. I am not suggesting that it was shaped this way originally, but because the rudder was one piece of flat sawn Mahogany that it had both cupped and warped in the 24 years since it was constructed. This would explain a few odd quirks of my boats sailing qualities.

Over the winter I made a new rudder. I should mention that at this point in my life I have been a professional woodworker for 31 years. A few of those years were spent working on, repairing, renovating and building boats. Some of that work was on rudders and I also made a new rudder for my previous boat.

For this rudder I used 8/4 flat sawn Alder, ripped off 2" pieces, joined all these and glued (epoxy) them back together to make a very stable perfectly quatersawn blank. The outline of the rudder was basically duplicated from the original. I should mention I did make the rudder 3/4' shorter because I have attached a sacrificial UHMW shoe to the bottom. It is shaped exactly like the foil. It is bedded in polysuphide and held on by four SS screws.
I used Alder because it is light, it's strong for it's weight and I had some.

I designed the foil section using some material out of an old book I have around here. I shaped the foil (this time) with a weird jig I made up using two forms and a laminate trimmer in a contraption. This gave me the base shape that then required some fairing and detail work.

I used some new high tech poly urethane sealer and automotive urethane colour top coats. I was able to have the paint made to match the colour of the hull/deck gelcoat.
It turned out alright. Good enough to go bash about.
Yesterday was the first sail using the rudder and as luck would have it, it is the first time I can recall ever grounding this boat. The water in our lake is very low this time of year normally....but not as low as I discovered yesterday. I did a little underwater farming when leaving the dock...it was just sand for the most part but it did mess up the rudder a little.

The performance was immediately evident. Kind of like the difference between driving an old truck and a modern good handling car. Even with very little forward movement the boat will respond quickly and precisely. The boat also sails the same on both tacks now....go figure.
(the next day) I was out again today and got some spirited sailing in. The wind really showed up this time. I have come to the conclusion that my Tillerpilot likes the new rudder, the boat tracks far better, and my imagination is telling me we are sailing faster. ~:0)

Cheers, Tim Diebert
April 13, 2008.
Kelowna BC

Here are some images:

You can just see the UHMW shoe on the bottom of the foil. It is much more white than the paint colour.

Trailing edge of foil.

Leading edge of foil.

UHMW shoe.

The metal (brass in my case) support for the tiller.