The plans for Farrier's new kick-up, daggerboard style rudder arrived. I'm surprised at their complexity, so I've decided to build to the original kick-up rudder plans. I never saw the point in a daggerboard rudder, since I'm not planning on sailing in 2 feet of water, although I suppose the ability to tune the surface area of the rudder could be useful.  I also don't plan on ever beaching the boat, unless the bottom is completely barnacle-encrusted.  Seems to me that it would just sand off all the bottom paint (at least).

I've often thought that you could make a daggerboard-style rudder that's pinned in a case, where the rudder pivots up if it hits something, and where you can remove the pivot pin and slide the rudder up if you need to navigate in the shallows. Until I ponder that some more, I'm going to make the blade, the easy way. This rudder will use Ian Farrier's design and scantlings, but the building technique is from Kurt Hughes.

11/17/03
First, I download a NACA foil spreadsheet. It looks like Farrier's rudder is closest to a NACA 0015 section. I recreate this section in the CAD program, draw a box around it, and email it to a plastic company on Canal Street in NYC. They cut the curve with a CNC router for $28.

I trace the template and rough-cut 7 pieces of 1x4 pine. Then I screw the template to each piece and route the exact curve. I assemble the 1x4s in a ladder frame with 1x6s for side pieces.

I'm going to make the mold from a piece of tileboard, which is just 1/8" hardboard with a smooth, waterproof skin on one side. While it's stiff enough to bridge the 12" gap between templates, it's too stiff to form the 1.5" radius nose. So I install pieces of cove between the templates to support the nose, then form the nose itself from two layers of 1/16 x 2 x 24" basswood, glued to each other and clamped to the frame.

The duct tape is to give the nose, from the tip to 2" back on either side, a rebate for a 4" wide strip of glass or carbon tape around the front, after the sides are joined.

After the mold is built and sealed, I attach a trial vacuum bag to make sure it's airtight.

The trial works, so I wax the mold several times and prepare the laminates: 2 layers of carbon (at 45 degree bias) plus many layers of unidirectional. To lay the carbon at 45 degrees requires using a lot more fabric than for a 0-90 layup.

I bag the first (port) side and the results are outstanding. Far smoother than I could have expected without using a mold, and almost perfectly fair.

Next, I lay up the starboard side. This side sticks to the mold a bit so I should have used more wax. I then glue a 1x4x48 strip of aspenwood along the strip of unidirectional, as additional reinforcement.

I build a router frame from lumber and steel angle. The router will sit in this frame and cut the inside of the rudder to a flat surface, ready to glue to the other half. I glue my foam core to the outer skin, using a vacuum bag to squeeze the foam into shape.

Now it's time to route the inside of the rudder half with a 3/4 inch bit.

It takes about a half hour to make a complete mess and trim the entire side. If I were more clever, I would route only the wood core and use a hot wire on the foam, but I'm not quite there yet. Maybe for the second pass, if it turns out too thick.

Before I glue the sides together, I cut a 2.5" hole in each side of the foam and fill with a plug for the pivot hole.

By the way, if you decide to use expanding foam sealant from a can, keep in mind that it needs air to cure. Clamping a board to the daggerboard half to keep the foam from growing too thick doesn't work.  Eventually I scrape the mess out and replace it with foam.  My only concern with using foam that's not 6 lb.-density core-cell is that it has almost no shear strength.  On the other hand, almost all of the load is going to be carried by the hardwood insert, so I shouldn't have to worry too much about shear strength in the rest of the board.

12/7/03
Finally, after 3 days of screwing around with the foam core in the forward section of the second half, I get it right and can glue the two halves together. The only part I'm not happy with is the trailing edge. It's ragged and too thick. I might have to add a fairing piece.

The next step is to sand the nose, and add two layers of glass tape in the rebate.

In the meantime, I built a sheet for the case side plates. While Farrier has devised a clever system for attaching the new rudder to the boat, it's too complex for me. I'm simply going to fabricate the plates from carbon and use the old method of gudgeons and bolts.

After a bunch of fairing, I chop off the top forward section of the blade to make the rudder balanced.

Next begins the long process of making a sleeve for the top part of the rudder. This is necessary because the rudder is tapered, but I want the case sides to be parallel, and obviously they have to be as far apart as the thickest part of the rudder. Since the pivot hole is aft of the thickest part, I would have to put a couple of long (about 3/4") bushings or a stack of washers, but this wouldn't give very much bearing surface for the pivot pin, which would be especially bad if the rudder kicks up while turned. So I do the Kurt Hughes process again. First I laminate a sheet of light glass as tightly as possible around the blade, followed by a 3/4" thick section of balsa. Since I want to sleeve to be removable, I use a barrier between the blade and glass, although it would have been a lot simpler to just glue the balsa on. The sleeve is removable just in case some time in the future I decide I really do need a kickup daggerboard rudder. I'll be able to remove the sleeve and glue back on the top forward section, to have a completely symmetric blade. Finally, I slice the two balsa sections apart, tape one at a time back onto the blade, put the blade back in the mold, and run the router over the balsa to give it a surface that's parallel to the plane of the rudder. I can laminate over this so the sleeve will have two sides that are parallel and as thick as the blade.

Next time, I will try to make the plastic barrier between the blade and first layer of the sleeve smoother, and use release film, and wrap a strip of glass around in a spiral, rather than trying to just pull the glass over the blade, because the inside of the sleeve isn't very smooth. However, it slides on and off the blade just fine, so it will do.

After trimming the sleeve to size, I put a piece of basswood on the front and back of the sleeve, and laminate a layer of carbon over the entire thing.

The problem of having to drive or take PATH to the workshop is that when you're working on a small project like this one, you often only get an hour or two of work in before you have to wait for the epoxy to cure, so I've been making a lot of short trips. Sometimes twice a day. I would start another small project to work on at the same time, but the next project is setting up the form frames for the floats, which is going to take up the entire shop.

1/20/04
I'm finally seeing the light at the end of the tunnel. I trimmed the sleeve to its final shape today, drilled the pivot hole, and bolted the case sides on, to see what it would look like. I'm going to put a piece of balsa or basswood over the top of the sleeve, and cover it with a layer of carbon, and glue some tows over the exposed balsa on the bottom, then the sleeve is done.

2/14/05 postscript: I end up discarding the sleeve because it appears that I don't actually need it.  Once I assemble the rudder on the boat, it appears that there's plenty of bearing surface between the side plates and the rudder itself.

To make the mold for the rudder brackets for the case, I going to glue together 6 layers of 1/2" fiberboard. This gives me a mold that I can put into a vacuum bag without worrying about it collapsing. The inside two pieces are shorter than the outside 4, so I have a channel for the G10 tube that's parallel to the sides.

1/22/04
I follow Farrier's plans for the layup of the brackets (lots of carbon unidir with a single layer of BD) on the outside. I want the rudder brackets to be slightly weaker than the transom brackets, since they are removable and easier to repair. Note for when you make a mold for the transom brackets: make the mold a couple of inches wider than the carbon, so it doesn't creep around the edges and make the bracket difficult to get off the mold. Also, plug the ends of the G10 tube so epoxy doesn't seep into it, and figure out a way to prevent the inside peel ply from being glued into the corner between the tube and the carbon.

I'm really glad I'm building the rudder now. It goes on the end of the boat so I bet most people build it at the end. I'm probably going to spend as much time building the entire assembly as I would spend building a small kayak. I would hate to have a nearly complete boat sitting in the yard and have no way of steering it for a month as I build a rudder, in which case I would probably slap something together just to get sailing. Of course, building every part from carbon takes a lot longer than buying or machining aluminum parts would.

Building the brackets has been a HUGE pain in the ass! First I glued the rudder brackets to the mold, then resin seeped into the tube. After I wrestled the brackets off the mold and cleaned out the tube, I had to sand the peel ply from the back of the tube. I filled in the hard corners with putty and laminated the unidirectional on the inside. This was the toughest vacuum bag I've ever done, since I had to make sure the bag wrapped all the way into the bracket, or bridging would prevent any pressure from being applied to the parts of the laminate near the tube, which is probably the most important part. I ended up gluing the vacuum port to the laminate, but fortunately no resin got into the port or stuck to it since it's aluminum.

I cut the bracket to size and sanded it, and it started to look acceptable. Then I cut it into two parts, rounded the edges, and bolted the whole assembly together to check the fit.

I've started on the transom brackets, and I think I'm not going to have the same problems. The mold is much wider than the laminates, and the tube is firmly plugged. I'm using release film in the tube area since it's easier to remove than peel ply. I'm also using 2 extra layers of uni on the outside and 1 extra on the inside, since I want the transom brackets to be stronger than the rudder brackets. I don't think this will be a problem anyway since the rudder brackets have such a hard edge where the tube meets the rudder case.