TIM WEBB wrote:Interesting design!
Simplicity itself. Getting the shape roughed out and assembled was really quick. More than half of the effort went into fairing and painting. Getting the pintles on was a bit fiddly, as they needed grooves chiseled for them.
TIM WEBB wrote:1. Does it keep the blade at the same depth as stock? Your drawing doesn't show pintle locations, and your pivot hole is 1" above the bottom of the head, but I can't tell where that is in relation to the waterline? My design has the blade about 5/8" higher than stock (when down). Didn't want to go any higher than that as the DS needs all the rudder in the water it can get! ;-P
It's absolutely stock compatible, and that means class legal. Although it would be simple to change the dimensions (make the blade a bit longer, head a bit shorter) if that's what you wanted. My main concerns were to
- get a better foil shape
- get the head above the waterline
- reduce weight
The pintle locations are such that the pivot is a the same place it was before. None of the hardware is shown.
The rudder has:
- 1/2" SS carriage bolt with washer and wingnut
- a nylon bushing for same
- a HDPE wedge as a tiller stop in front of the neck
- 2 pintles
- a springy blade to prevent the pintles from slipping out of the gudgeons
- and a 3/16" or thereabouts carriage bolt with washer and wingnut for the tiller
- nylon bushing for same
TIM WEBB wrote:2. What material is the center headpiece made of, and how are the flanges attached to it? Epoxied? With or w/o fasteners? One of the main differences between my design and John's is that he used a wood core for his, whereas I used spacers. Didn't want any wood or fiberglass involved at all ...
I started with a single board, laminated from 2 planks of .5" plywood. I then shaped the foil first (having a long flat part made that easier). Then I cut the outline of head and blade with a jigsaw. So, the head is made from the same material as the blade. The flanges, or cheeks are as described earlier and simply epoxied to the head. With that much area for the glue joint there seemed little point to using fasteners. (All I would do differently about the head would be to make the 'neck' a bit narrower in the back, because the tiller no longer folds all the way).
I know I added a sheath of fiberglass to the rudder blade. Normally wouldn't need that for the head, but I may have added one there, too, simply to keep the dimensions the same (so the blade would fit between the flanges). I also made a diagonal cut to slice off the front tip of the blade and glued it back on. That adds a glue line as defense against any water getting in from a grounding.
TIM WEBB wrote:3. Are you using a stock tiller? A 1" wide headstock would seem to accommodate one just fine ... ?
that was the idea. For the blade, a slightly thicker stock would have allowed and even better profile, but I liked the .5" plywood because of how many plies it has. If you read my original post (or article in the DS) you will find that I used the pattern of "banding" revealed when shaping the blade as a depth guide for getting the rough shape.
TIM WEBB wrote:I would imagine that if the cracks didn't open when under load in your test, that it may be possible that the cracks are not stress cracks, but rather from expansion/contraction or something like that?
At this point, I'm not sure that they extend beyond the paint.