Rudder placement

[persephone]

Hello,

I'm wondering how critical the location of the rudder pivot (and with it the entire rudder) is. To be more specific, the rules allow the pivot point to be 9" from the transom, but it also needs to be 1" above the projected line of the hull bottom. As I see it the two factors are longitudinal location vs. the submerged surface of the rudder. As the rudder moves aft from the transom (increasing it's leverage) it must also come up (decreasing it's submerged surface area). So has anyone experimented with the placement to see if there is a discernible difference?
I am working on a new aluminum head for my rudder. I'd rather not figure out after the fact that the pivot could have been better placed. The stock fiberglass head I have has the pivot at 7.5" back and 1.5" up, but I haven't had a chance to sail yet (just bought the boat a few weeks ago) so I have no idea how that feels.

[Phill]

Welcome to the DS family and forum.

First, the 9" and 1" measurements you referenced are Maximums. You may put the pivot closer than 9" and lower in the water than 1" above the extended hull line. ( See DaySailer Association tab, Handbook, section 3 rules 6.5 and 6.6, i think)

I builit my rudder to be very close to the transom so my pivot is about 6 1/4" from the transom, and about 1/2" above the hull line. Our rudder is small enough and looses area very fast when you heel up, so I wanted as much blade in the water as possible. Also, by not pushing the limits, I have no measurement hassles when measuring.

As for angle, best preformance will probably be straight down. When you angle it up, the weather helm gets very strong.

Hope this helps. and happy DS'n
phill

[persephone]

Oops!
I was thinking backwards on the vertical measurement. That makes things a bit easier. Thanks.