New Rudder 2

In the first photo below you may be able to see the bolts in the bolt holes of the pintles. I cut them off so that they're just pins now, going through only the pintles and the ¾" core, not the whole rudder. Because the rudder blade will be right against one side of the rudder head, I didn't want pintle bolt heads or nuts to be sticking out and getting in the way. I'm confident that the assembly will be quite strong without having the pintles bolted through the cheeks, what with all of the epoxy that will be in there.

Thank God for John Booth and his shop! John showed me how to rout out the channels for the pintle arms and set me to it. I think I did a good job for first time routing! But I think I put the bottom pintle on the top. I have an idea that the bent-out one is supposed to be the one you find the bottom gudgeon with. Too late now!

Below, the port side of the rudder head is being glued on (the bottom layer wasn't glued up at this point):

You can see how the pintle disappears into the wood.

The rudder head is finished now, except for some filing and sanding. I'll post a photo when I've smoothed some of the rough edges...

Starboard Sheer taping

This was done on Wednesday. Two layers of 3" cloth went on at the same time. The hammer is there because I put some silicon-bronze ring nails in to bring the deck and side back together in about that spot I'm stopped at in the top photo.

Boat bits

It's a rainy night. I finished gluing the starboard cheek onto the rudder blade core. Port one will be done tomorrow. Thought I'd check my cleat collection, since Godfrey just gave me a cleat. It's the same design as the one that was the bow cleat, and he says it's not chrome, it's white bronze. It cleaned up well.

For the bow cleat, and anything on the deck or the cabin top, I'm going to drill an oversize hole, fill it with thickened epoxy, then re-drill for the fastening. This is so no water will travel into the wood from the fastening as it gets stressed. Same thing with the transom.

I know the new bow cleat is ugly, but it's strong like bull and that's more important to me than how it looks.

Rudders compared

As the photo shows, the new rudder profile is quite different from the old. The copper patch is where the outboard prop is, so this rudder won't be getting chomped so much. Hopefully.

I haven't done any math on it, but it looks to me like they'll both have about the same area underwater. I placed the ruler where I think the waterline will be.

The difference will be that a smaller percentage of the new blade will be out of the water when the boat heels. The foil shape will hopefully boost performance. And the rudder won't be acting like such a brake when turned hard over.

New rudder

I wanted the rudder parts to be 1½" thick, and thought I'd make it out of two layers of ¾". Then I thought there might be an advantage in making it out of four layers of ⅜". I chose exterior fir ply because the whole boat is that, so no point in adding fancy.

One reason to go with the ⅜" ply was the number of plies per sheet. At the lumber yard I looked at both ¾" and ⅜". The ¾" had six plies. The ⅜" had four. So 1½" of ¾" ply would have 12 plies, whereas the equivalent thickness in ⅜" (four layers) has 16, a third more.

Another factor that decided me on the ⅜" was that the pintles from the old rudder are for ¾" stock. If I wanted to use them and also have the rudder stock be 1½" thick, I'd have to install them on a core ¾" thick, and put a ⅜" cheek on each side. I needed either a half sheet of ¾" or a full sheet of ⅜". Simpler to go with the ⅜", even though it meant more cutting and gluing. And stronger, because of the additional plies. I had it cut in half at the yard so that I could manage it, another reason to go with the thinner wood.

The reason for such a thick rudder blade is to be able to make it into a foil shape. It's an empirical fact that making blades foil shaped improves sailing performance and boat handling. The official foil shape is NACA 0012, apparently. I tried to figure out how to make the correct shape, but it was too complicated for my little noggin, so I grabbed a jpeg of a NACA foil and adjusted it in my illustrator app to fit my rudder. If mine isn't a true NACA foil, it will still be way better than a straight-sided blade. The above drawing shows how I can get a jump on the shaping by making the outer layer of plywood shorter in the right places.

Another good thing about making the blade with four layers is that I can have a groove in the top for the uphaul and downhaul lines to travel in. Here's a view looking at the round top part of the blade, from in front or behind it:

The two core layers (⅜" + ⅜" = ¾") are shorter and the outer layers taller. The outer plies will be rounded and the inside corners will be filleted so it can all be glassed and sealed properly.

Yellow is the downhaul, green the uphaul.

Here's a picture of my bathroom floor. I chose it to glue on because I wanted to make sure the core layers were straight and flat, and I'm pretty sure my bathroom floor is good. The orange/red circle shows where the top of the blade is on the other side of the stock, and also shows the minimum contact area of the two pieces. It's a 12" diameter circle. I was working out how tall the whole rudder will be (53"). It will extend 12" below the skeg on the Firefly.

It takes almost as much time to illustrate and describe what I'm doing as it takes to actually do it! Much less mess and back ache, though. So far I have all of the rudder pieces cut out and the core two layers glued together. Next is to carve out recesses in the stock cheeks for pintles, install the pintles and then glue on the cheeks. The bolts attaching the pintles will not have heads or nuts: I'm going to cut them flush with the pintles, to make the recesses simpler and because the cheeks will serve the same purpose; those bolts won't be going anywhere.

Transom prep

The transom is made of the same plywood as the rudder was, so I'm sealing it as much as possible. Any fastenings will be in oversize holes filled with epoxy and re-drilled for the fastening, so that the fastening is not touching the wood, but surrounded with epoxy.

Before today:

Today's work:

Engine cut-out before:

Engine cut-out after:

Tomorrow we glass!

Possible rudder design

I want to keep it simple. Bolger's way of having two big pieces with a big connecting bolt makes sense. I had a rudder like this on my Windsprint.

If the blade is on the opposite side to the tiller, it can swing up until it hits the tiller pivot bolt. It would probably interfere with the mizzen boom before that, though, so it wouldn't be up there often.

I'm thinking of making the stock and the blade both with 1½" thick ply, and shaping the blade in a naca foil shape—at least, as much of a foil shape as one can get in 1½" ply and still have strength.

Here's the same concept on the rudder of one of Matt Layden's Enigma designs:

He must have recessed the bolt heads for the tiller, 'cause the blade goes past them on the other side. This rudder is huge because it's used as part of the boat's lateral resistance, since it doesn't have any other board or keel, just chine runners.