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post #29 of Old 01-19-2014 Thread Starter
captain jack
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Re: why so long?

Originally Posted by Faster View Post
Jack that sounds like a typical balanced rudder.. Balanced rudders don't split the blade area 50/50 across the rudder post.. the forward balancing tab is typically 20% of the chord or less, so that sounds good. Rudders that become hard to control at times typically have the stock right at the leading edge like barn door rudders on full keels.

Too much balancing tab and you'd have no 'feel', and also with an inboard propwash can act on the balancing tab with enough force to make it hard to hold the tiller straight under power. Too much area and it can be a problem (similar to trying to hold a tiller straight when you're backing up with speed).
i have seen rudders with the stern post a little farther towards the middle than mine. maybe 1/3 of the way in. that's what i was thinking about. actually, this will be my first boat with a balanced rudder. the holiday is transom hung, like the dinghy.

a 50/50 set up wouldn't really work.

it's like a motorcycle front end. if you draw a line through the neck of the frame, where the bolt that the front end pivots on passes through, and you drop a perpendicular line through the center of the axle, the line through the axle should touch the ground after the point where the line thrugh the neck does. this is called positive trail. it's much like the 'crazy wheels' on an office chair. the wheel is litterally being pulled along by the force from the rear wheel, which is passing through the frame to the neck. this force must lead to a point farther forwards than the point where the tire touches the road. if it doesn't, if these points are reversed even a little, you get negative trail. the bike will not track in a straight line. what i like to call the death wobbles.

if you have too much trail, as in a poorly designed chopper front end, you get a bike that goes straight, well, but is hard to turn at low speed. my chopper is raked out pretty far; around 50 degrees. however, i know a bit about front end design and i took steps to counter this and reduce the trail. it has very little trail, even with the long front end, so it handles low speed turns like a stock bike while maintaining high speed straight line stability.

a rudder is like that. the force of the boat needs to be forwards of the center point of the pivot. if it is very far forwards, like a transom hung rudder, you get a lot of trail which makes it harder to turn. too little trail and it loses stability; what you would refer to as 'feel'. if you had no trail or reverse trail it woud be hard or even impossible to go straight because the boat would be pushing the rudder, rather than pulling it, through the water. imagine turning a crazy wheel backwards and then trying to push the chair across the floor. the wheel would immediately snap around so it was trailing the pivot point.

btw.. with the tiller 'longish' and sailing alone, I'd really give some thought to moving the traveller to the front of the cockpit as shown in your other thread.
i won't be sailing alone, most of the time. the outboard equipped versions of this boat do have the traveler behind the companionway. really don't know that i would like that set up...although you aren't the only person to suggest that. i am used to having the main rigged to the stern. it's something i will give consideration to, since so many experienced people have suggested it, but i won't be changing it til after i have some time sailing it, as is.

The only rules that really matter are these: what a man can do and what a man can't do.---Captain Jack Sparrow

1971 Cal 27

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Last edited by captain jack; 01-19-2014 at 12:25 PM.
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