yoh wrote:
Glad to hear the lead is gone. But why the oak? I understand that you use the oak in an area where you are concerned that the rudder casting might compress the foam core to a point where the outer composite shell would fail. What I do not like about the oak idea is the weight, the tendency of the material to rot, and the risk that the blade would fail right below the area where the wood ends.
Hey, sorry for the delay in responding! Actually the necessity of the oak is questionable. We could probably have just gotten away with using foam and injecting thickened epoxy into the areas where the bolts mount, but everything is a learning experience. The oak should never rot becuase it's totally encased in waterproof epoxy, but I concede the possibility the epoxy might crack. Still, I think the time necessary for the oak to rot away would far exceed the lifespan of the boat. I also don't think the blade would necessarily fail where the oak ends because the vast majority of the strength is in the glass fibers. The oak isn't doing much.
Quote:
I am suggesting not using a solid piece of wood in the head of the rudder blade. Instead I would recommend laminating more or thicker cloth layers in the upper 8 to 10 inches. A stringer might be an idea if you would run it from top to (at least almost) bottom.
I see what you're saying, but like I mentioned above, the oak is really just providing a rigid structure for attachment to the rudder casting, not for longitudinal rudder strength nor for resistance to twisting - what our plastic rudders really need so they don't snap off. Make sense?
Here are the first set of pictures:
Here's the foam and oak for the second rudder. You'll note the oak is smaller, and it probably could go away altogether.
Me & Steve laying up the first side. I think this is either layer two (bid) or three (uni.) The green color comes from the epoxy hardener, which is sort of emerald-colored.
Here's the layup for the first side, completed.
Below you can see 3 of the 6 layers of glass used. The order (inside to outside) was Uni, Bid, Uni, Bid, Uni, Deck. (Wick's Aircraft Supply has several types of fiberglass - the last layer (deck glass) is thinner and finer. This should result in much less work when "finishing" the rudder and making it glass-smooth.)
Some time in the next few days I'll trim off the excess glass and prepare for laying up the other side (which will probably be next weekend.) I'd like to finish this project before I go on vacation in 3 weeks.