I'm workinging on Paul's barndoor rudder upgrade for the Vacationer. I've got the three layers of 1/2" plywood epoxied together. Now I need to taper the rudder. Paul says to keep the foreward 33%-40% straight, then taper down to 3/8" at the trailing edge. Paul: Is the green tape in the photo about the right line to start the tapering aft?Â
Dave
Sort of Dave. Maybe it would be easier to just measure along the top, where the seam is and mark the 35% point, then draw a line from the balance portion directly aft to the trailing edge and mark the 35% point on this line. Connect the dots between the two sections of the blade. This will be the average 35% point along these two angled edges. Below this line, just drop straight down, rather then attempt to angle it.
Attached is the rudder drawing with two additional lines added. The blue line is the actual 40% point along the blade, which zig zags around because of it's shape, This isn't practical to smooth out, so you have the right idea Dave, and just strike a complimentary arc. The red line shows how I'd make this, which is a bit "fatter" than yours. The important part is the area below the LWL of course, so stop the tapering above the waterline as soon as practical, so you don't lose too much blade "meat", because of the tapering.
I see you've simplified the shape a bit. I hope you add some style back into the cheeks. I've recently made a similar rudder (top photo) and of course just had to add some sort of flourish to the cheeks, if just to spruce things up.
Thanks much for the reply, Paul! I am planning to spruce up the cheeks to add a little flourish to the rudder. I'm anxious to try it out!
Dave
Paul: In building this rudder, I drew out the outline on some scrap 1/4 plywood. I then transfered the lines to the 1/2" ply that formed the finished product. I just now realize I made a big error. Although all the angles and measurements seemed to check out correctly, the bottom edge on my rudder is parallel to the top edge of the "tongue" of the rudder forward of the gudgeons and pintles. The part responsible for easier rudder control. It is not at an angle as on the plans. How big an error is this? Can I leave it, or is there a way I can fix it without starting over?
Dave
No big deal Dave. I assumed the balance portion of the rudder would fit as closely as practical to the slightly modified deadwood assembly, so the angles weren't printed. Just cut off what you need to at the top of the balance portion, so it fits tight (1/8" gap or so).
I've attached the dimensional drawing and did offer some angles for you, but with home builds, everything is "build to the work", so the less dimensions the better usually. Simply put, your transom angle will be slightly different, the buttocks aft the deadwood follows will also be slightly different. This is normal and the nature of home builds, none being the same.
Leave the bottom as is and whack off the top of the balance as needed to clear the deadwood.
Thanks Paul. The main rudder body and the balance portion of the rudder forward match the line of the keel bottom and transom exactly. No trimming needed! The shape of the rudder overall is a little different than the plans, as I mentioned. The bottom of the rudder and the top edge of the balance portion are paralelle, not at a small angle as on the plans.
Any tricks for tapering the 3 ply meranti plywood rudder? Using a 40 grit belt sander, and working for what seemed like hours only took off a few millimeters of stock!
Dave
great looking project! im intersted in hearing how
it impacts handling, ive been thinking about a rudder
change for my super skipjack as im not real happy
with how the boat turns especially through a tack.
keep the pics comin'
I'm surprised that meranti is so tough. When I cleaned up the foils for the scamp camp they seemed kind of soft to me. I just made a rudder for the latest foolishness I've undertaken and shaping it took only 10 to 15 minutes. I used a block plane and a bench plane followed by a long board with 80 grit. What are the core layers of your plywood made from? I've always been afraid to use my belt sander on a shaping job because I always end up making big gouges that I have to fill later.
Al
Meranti is 9 plys thick, with the hardest waterproof glue between each ply. I used a smooothing plane and a block plane and about 2 hours of elbow grease. I finished the smoothing with my belt sander. I'm going to have to resharpen the plane irons now!
Dave
I usually employ a power plane for the rough in, fine tune with a belt sander than fair to shape. I also try to incorporate a subtle curve in this taper, so the veneer lines at the forward end will be tighter than the ones nearer the trailing edge. In fact, I use these lines as a guide to how much more the whack off or areas that need fairing.