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.

Rudderless

This is the forefoot of the rudder. I was going to glass in that bottom piece of oak, and round and glass the end grain on the leading edge below the bottom pintle. I accidentally sat on the rudder when it wasn't flat. I'm glad it happened now and not at sea!

Water got in. Glue not waterproof. Wood rotting.

Water entry could have been from the prop damage, or could have been from a break in the epoxy in the end-grain on the edge of the rudder, which didn't have glass over it.

Glass Tape Fillets

Today I taped & filleted the port side of the cabin/deck joint, all the way back to the transom along the cockpit coaming as well, with one length of 2” tape. Also, the port dagger board opening on the deck got tape around its edges.

Using the WEST system pumps sure makes it easy! I started out by brushing resin on the whole length of the corner, then mixed up a batch of thickened resin using wood flour and pushed it into the corner with the round end of a stir stick. I’m using “craft sticks” from the dollar store, which are like tongue depressors and come in a pack of 30 or so.

An important thing about epoxy is that it needs to be well stirred. It’s not like polyester resin, which you can apply hardener to afterwards and it will kick off—or even put it in the sun and it will kick! No: epoxy needs the actual molecules of the resin and the hardener to be together or it won’t get hard. So you need to stir it well. And part of stirring it well is making sure the sides and bottom of the container you’re stirring it in get scraped regularly. To this end, I shaped the stir sticks to conform to the cups I’m using, which are 10 ounce paper hot drink cups that I bought in a package of 50 from the Wholesale Club. I found the angle of the bottom and side by laying one stick across the top of a cup and resting another stick on the bottom of the cup and against the side of the cup, and striking a line on the standing stick:

Then I transferred that angle to near the end of another stick, and used that as my pattern to mark other sticks with. The ends were cut off with garden shears, giving me sticks that connect with the sides and bottoms of the cups perfectly, so the resin is constantly scraped off and mixed in.

(I don’t work on top of the stove; it just happens to be the best spot to set up on around here.)

I used the round end of a stir stick to make the fillet curve, not pushing the curve of the stick right into the corner, but just loosely passing it over the thickened epoxy to make a fairly robust fillet. One pump of resin and hardener made enough thickened epoxy to do about 18" of fillet. Then in another cup, another pump of resin and hardener (well stirred!), which was flooded onto the fillet by brush with a light touch. The tape was laid over and more resin brushed onto it.

One needs a light enough touch with the brush that the curve of the fillet remains, but firm enough to straighten out the cloth tape. Once the tape is wetted out, you can push it around with the brush by poking it with the end of the bristles, as if you were stippling. Little pushes move the tape well. I’m talking about sideways, across the width of the tape here, so that it comes out more or less straight in its length. The length doesn’t get moved, except that it gets pulled constantly towards the yet-to-be-done end as it gets stroked with the brush.

By the time I was done I was feeling like I had too much sun, and didn’t think to take more photos. Maybe the starboard side will be good for that; that’s the sunny afternoon side anyway. I’m finding it interesting that I’m even taking photos; this blog is good for that. Usually I just forge ahead and take pics later, sometimes wishing I’d documented my build. And most often I’m feeling like I’m rushing to get the thing done before the resin goes hard. I did go through two brushes, as the first one started to get hard about half-way along.

But I think this is the only way to do a long continuous piece: by mixing up small quantities as you go, and doing the whole thing with little batches, rather than making one long fillet and coming back to the beginning to lay the tape down, only to find that it's started to kick already.

I didn't think to mention this until now, but this method of putting the tape right on the freshly made fillet is so much easier and faster than making a fillet, trying to sand it smooth, and then applying glass to it. Very little sanding is needed now; mostly just taking off the tape edges.