One the left, the original "high performance rudder for the Potter 19" which inspired the new rudders for the Potter 19's in the early 200's. Designed by Judy Blumhorst, and crafted by Arnie Jonnsen's Boat Works of Alameda Calfirornia
The rudder on the right is a 1997 beaching rudder from International Marine. The rudder on the left is the original "high performance P19 rudder" that inspired the current generation of rudders for the Potter 19.
The rudder on the left is the one I designed in 2001. It is one piece (for greater rigidity), about 30% larger in area, and has a Steener foil. It creates much more greater lift than the existing factory rudder and it has much more "authority".
This is the original "high performance rudder" that International Marine copied starting in 2002. This is the prototype that proved the concept that the Potter 19 benefits from a larger rudder than the factory was providing between 1982 or 3(the year production on the P19 resumed after being discontinued in the late 1970's). Starting in 2002 or 2003, International began selling an optional "high performance rudder" patterned after
With the greater lift generated by this rudder, the P19 can handle greater angles of heeling in the gusts without rounding up. The "feel" of the helm is improved significantly, and the skipper can "feather up" and effectively make the boat point higher.
When Herb Stewart designed the Potter 19, he experimented with several different rudders. My performance rudder is very similar in size to the one he finally chose, with approximately the same area. In fact, my has almost eaxactly the same area as Jerry Barrilleaux's 1970's HMS 18, hull #44. For my rudder, however, the balance point and the foil shape were chosen in accordance with modern foil design.
|To make the lowering function work better, I put a cheek block on the
side of the aluminum plates to give the line better mechanical advantage.
The cheek block a Harken 092 (#10 fasteners, 2 3/16" on center). A Harken 109 is the same dimension, just stronger and a little more expensive, if you can't find the 092.
The holes are 2 3/16" on center, which matched up almost perfectly with the 1/4" bolts thru the aluminum cheeks on my 1997 rudder (a replacement for the original 1985 rudder, which warped). However, you will have to drill out the holes to enlarge them from #10 to 1/4".
You'll be drilling thru some pretty hard Stainless steel - Drill slowly, use oil, don't overheat the drill bit.
Also, you may have to sand the lower blade a few thousandths of an inch, to get any high spots off or built up varnish ,to keep it from binding between the aluminum plates. I wet sanded mine with fine sand paper for a few minutes to get it to lower and raise up smoothly.
After sanding, I assembled and tightened the bolt so there was minmal wobbling of the lower blade. The blade moved up and down without too much friction.
After sanding, the rudder worked fine, and didn't need any wax or lubricant. But you might consider that. Jerry B once told me that vaseline can be used as a lubricant to help the lower blade slide between the plates. (I dont remember if that was a P19 or P15 rudder) Vaseline lasts a long time in fresh or salt water, so it's a good cheap solution.
But I think that vaseline is a "yucky" idea -- a purely emotional response to the idea of wood and petroleum together. (and I don't know what the petroleum in vaseline would do to the wood if it got scraped up and then soaked into the wood). If not vaseline, maybe wax or some spray on super-lube might help. (no silicone in it - causes longterm problems for revarnishing)?
Regarding swelling from moisture: Properly single piece or laminated solid mahogany (when properly selected for nice grain) is VERY dimensionally stable, and both the top and the bottom half should shrink and swell at the same rate. That's why it's the boat-builder's traditional choice of woods for rudders and wooden daggar boards.
If you keep your rudder decently varnished, and don't leave the bottom half sitting for weeks at a time in water, you shouldn't have to worry too much about moisture swelling the wood (hope those aren't "famous last words" )
Fair winds, Judy B
PS. The rudder on the right shows the cheek blocks I added. I don't like having the kickdown line running between the plates. It could get caught and jam. So mine runs on the side of the board. (The rudder on the left is my prototype "high performance" Steener foil, one piece rudder)