J/30 Class Association Forums J/30 Forum The Boat, Sails and Equipment Rudder(s)

This project is now well underway. Started with buying 3 large slabs of plain sawn white oak, 37.5 board feet for about $270 worth here in the NW, I may have as much as 10 bf. leftover after ripping these down. While the boards were plain sawn when you rip them and turn them 90° they become quarter sawn or rift, which is exactly what you want for this large lamination. These slabs were 8/4 (about 2" thick") and I surfaced them slightly bringing them to 1-7/8". Then I ripped them to several different widths depending on where they were going in the lamination. I could have easily ripped them all to 2-1/2", but I am cheap and I hate turning lots of good wood into sawdust. The tradeoff for ripping to different dimensions is messing with these different thicknesses in the glue up, since they have to be centered relative to the next piece. So I am doing this in four steps, gluing similar sized bits together first and then joining the combined sections.

I chose white oak because of its strength and the ease of milling it. I see some builders are concerned with rot, but using epoxy and barrier coats and a couple of extra construction steps I think I can mitigate that problem well. I do think it would be possible to use a less dense core material and rely more on the glass skin for strength, but I just decided to overbuild this thing.

There are lots of good videos and information out there on doing these rudders and centerboards and I have decided to go a hybrid route with a jig that will let me slide the router up and down the length of the slab and then fix the jig into place and carefully work the nose of the rudder.

In my wood shop I had already made a setup to mill large wood slabs that I can use part of for this project. It consists of two 2/4's that I have milled to be straight and true. They have a provision to allow me to clamp these rails to my work table and then using a bridge with the router mounted to it, I slowly move the bridge assembly back and forth over the slab and flatten it. So for this project I will use those same rails and smaller bridge that has the NACA0012 foil shape offset from the final shape by 40mm.

I started this project with some info from Duckworks that has a form you can fill out to create NACA foil shapes to your dimensions. But when I worked out my basic dimensions and printed it the offset line did not extend nearly as far as I wanted it to at the trailing edge. So I asked a friend with engineering experience to see if he could improve the plot and he did. Then the next trick was to get the print from my printer to match the actual dimensions I was going for and that took some messing around (that is why I included two slightly different spreadsheets). An actual plotter would be the way to go if you had access to one. In any case I got a print that matched the 18-1/2" width I wanted. Then using another highly sophisticated method of laying some carbon paper over some hardboard I traced the shapes, cut them on the band saw and faired them with a sander.

Next step was to cut these offset rails and I did that by using double sided tape and cutting the first pair of rails together and fairing them to match the template. I used some leftover plexiglass from my companion way to make a large oversized router base to ride on these rails. I purchased some aluminum right angle channel and made the two guides to attach to these offset rails and then added some flat aluminum to make the entire frame rigid. In one of those happy mistakes I built this fixture 24" wide since the aluminum I purchased was 4' and I needed two rails. Then when I sat the big new router base on the fixture I realized that when you slid the router to one side it would drop off the support rail. So I just made another wood offset rail and added it to the fixture. Now I can easily slide the router base over the fixture side to side or fix it in place and slide the entire fixture and router up and down the rudder blank.

So that is where this project is today. The blank has one more thin piece for the trailing edge to be added tomorrow. Then I can layout the overall shape and position of the hardware and the hole for the tiller. I am doing video on this project so there is much more to come. While I am a more advanced woodworker I really think this project can be managed by most garage type woodworkers once they know the steps.