rudder

[HakimKlunker]

Originally Posted by alan white

I didn't miss what you said about the rudder post angle. And regarding your having mentioned a breakaway rudder, I noted that too. I only suggested the idea of a rudder plate that breaks further down, leaving a portion of the rudder still viable.

I agree with that. We lost our rudder on a race recently and there was only 15 cm left.
Angled R/stock: you need to consider the change in balance of the rudder blade while angled to prevent reversed forces in steering or having too much pressure.
For balancing the rudder - I would say - that the position of the stock in the blade makes it un-necessary to angle the stock.

I suppose that makes me the expert on foil rudder design - and I've never built one! Post plans going to machinist in morning...thanks.

[PAR]

Mark, I believe you're over thinking this thing. First, I wouldn't damage the laminate just below the shaft to "help" it sheer at this point. Just make your armature fairly big along the shaft (the welded ears), so the laminate has plenty to grab onto. If left short as your drawing shows, it will naturally break below the shaft and armature contact areas.

I also wouldn't venture too far out onto the design limb, by trying too many things at once. This is a great way to not be able to figure out what wrong, because you've done too much to pin down issues.

I'm not sure what type of boat this is, but I wouldn't cant the shaft. If you feel like you need to, then a small fence at the top of the blade will be a much easier thing to do. It's also something that could be easily retro fitted, once you've sorted out the rest of the rudder redo. Ditto and end plate on the bottom.

Also don't go crazy with balance. If your previous rudder worked well then I'd use what was there. It's real easy to screw up a rudder with balance, so don't over "play with it" thinking you're making things better. Either know you are making it better or "sneak up on it".

"wouldn't venture too far out onto the design limb" I have a propensity towards that. Not doing production, where one can evolve a design feature, I have one shot at making something right and tend to do exactly what you said, "over-think". Alright, then. Keep it simple. Thanks.

Hey, I watched the machinist finish milling the flats on my rudder post today(I'll sure get another hour on my bill for that!). Three inches is BIG! I said it was going to be a 3cm plate across the back of the boat but I made it 4 - by the time I get it glassed in, they'll be able to use it as a model for Chobham armor.