Rudder Efficiency

[Peterw11]

Here ya go:

http://www.youtube.com/watch?v=pgBoAD8LBMI

Filmed on the Charles River, Boston, BTW.

[seandwyer]

Wow - I feel better knowing that my question was something other guys wondered about too. I thought a while before posting because I thought it might sound silly. I've been sick for several days and not checking in and am both astonished and intrigued with the discussion.

I think I am convinced that the correct placement for the rudder is in the fully down position for a few reasons - one, someone mentioned the bit about racing boats always using the fully down position - also, KC I think mentioned the soft wood pin being used to fix the rudder - I actually now remember being told to do that once by a DS racer. The hole I use to tie the rudder in the up position when taking the boat off the trailer is the hole he told me to put a piece of dowel in.

However - just because I'm convinced, doesn't necessarily mean I understand why, it just means that I recognize that people that know much more than I are doing things this way for a reason.

All things consider though, I am still wondering if anyone has a system they would like to share that keeps the rudder in the fully down position (other than the dowel pin). I think I'd like to find something, especially if it might make holding onto the rudder easier when the boat is going quite fast for extended periods of time, because - yes, it gets a lot more difficult to hold onto the tiller when moving along nicely if you are staying on one tack for 30 minutes or more.

Thanks to everyone for the info - I'm off to watch Peters posted video on rudderless steering!

[GreenLake]

There are two main solutions to this problem. A soft dowel, or a line from the front of the blade. The latter comes in two theoretical variations: a very thin line that's calculated to break precisely when needed, or a bungee of some sort, that would stretch far enough. Either one would lead to a clamp on the rudder head or even the top of the tiller.

Thin lines that break on demand used to be employed on traditional sailing ships for a number of purposes, but with modern fibers as strong as they are, it might be rather difficult to achieve that. Hence "theoretical".

I'm almost sure I read about a bungee solution in the forum, or on the site, or in one of the articles that are linked from the forum. But it's been long enough that I don't know any longer where I saw it. The technical problem with that approach is to get enough stretch.

The solution with a line or bungee should have advantages if you need to launch from shallow waters a lot. In a situation like that, I usually push off first and fix the rudder as soon as I'm in deep enough water, so I haven't had the need to lower the blade. And, so far, the friction in the hinge has been enough to hold my rudder down.

[GreenLake]

Ah, used the "search" with "rudder bungee" searching for "all terms" and found kokko had linked this article.

Several others mentioned using a bungee on a DS, but nobody provided specifics (e.g. means of attaching the bungee to the rudder).

The comments in the article above mention a special clam cleat set up to release under load. That would be a third alternative which could be used with an ordinary line. It would have the advantage over a bungee in that the pull would be with maximum force, but 0 after hitting the first obstruction hard enough to release the line.

[Peterw11]

I saw a pretty clever setup on a larger cruising sailboat that allows the helmsman to set the blade in the full down position and hold it there, and also allows for it to be lifted to horizontal when in the shallows, all without leaving his seat.

Essentially, it's a pushrod type device, about 2' long, with a T handle on one end (think plunger on a bug sprayer) and a clevis on the other. The clevis attaches to the trailing edge of the rudder, and the rod extends up to a slotted bracket located on the same edge, just below the tiller. The pushrod has a pin which intersects it just below the bracket, to hold it in the down position. The bracket is angled in such a manner that when the rudder strikes an object, the pin slips off the bracket and lets the rudder pivot upwards on it's own.

When approaching shallow water, the helmsman can pivot the rudder manually, by simply moving the pushrod out of the bracket and yanking the rudder up to horizontal, holding it there with a second cross pin. When back into deep water, pushing down on the pushrod forces the blade back down again.

I don't know is such a device is commercially available, (I would think it is), but it's simple enough to be easily fabricated from stock aluminum tubing and a few proprietary or fabricated parts.

As an alternative to the cross pin fixation, a simpler, friction style bracket, tensioned correctly, could be used to hold the blade in different positions.
It could also be tensioned is such a way that the blade would stay down against the force of the water but then would pop up automatically, when it strikes an underwater object.

[ctenidae]

I just took the bungee of my rudder last night to take it apart to strip and repaint, and I'm trying to remember what I had it attached to (must be getting old...) I'm pretty sure I hooked one end to the wing nut on the swivel, looped the cord around the rudder, and hooked the other end to the wing nut.

I think. I remember hooking it up and thinking "There's no way this will provide enough pressure, and there's no way it'll stay," but it did. Elegant? Absolutely not. But, effective.

[dannyb9]

if your rudder bolt is set just loose enough to let the blade drop when its not side loaded, then it could be a non issue. if youre reaching or running, a partially raised rudder is not a big factor, hull balance is more important: trim to unload the rudder (heel to windward etc) in fact the extra leverage of a partially raised rudder may help inform that the hull could be better balanced.... when tacking upwind speeds are not so great, the rudder can drop to vertical every time you tack and be held in place by side loading for maximum 'lift'. so i say get loose, dont worry, be happy : ) !