| Re: Rudder Alignment
[Re: PeelSkid]
#146099 06/18/08 09:43 PM 06/18/08 09:43 PM |
Joined: Aug 2007 Posts: 190 lesburn1
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Posts: 190 | Lash the tiller cross bar to something so that the rudders appear to be straight ahead. Then with a pencil draw a line parallel to the waterline down X inches from the bottom of the hull. (this presumes that the rudders are locked in the down position, right <img src="http://www.catsailor.com/forums/images/graemlins/laugh.gif" alt="" /> ) Now measure the distance between the center of the leading edges at the line, and also the trailing edges. If the rudders have no toe in than the distance should be the same. 1/8th inch of toe in would mean that the leading edge is less then the trailing edge by 1/8th inch. You can check your Ackerman steering in pretty much the same way just move your tiller over half way and measure again. For the basics, go to http://www.rctek.com/handling/ackerman_steering_principle.html
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| | | Re: Rudder Alignment
[Re: Ventucky Red]
#146100 06/18/08 10:39 PM 06/18/08 10:39 PM |
Joined: Jul 2001 Posts: 1,200 Vancouver, BC Tornado
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Posts: 1,200 Vancouver, BC | Old Skool T drivers used to setup 1-3mm of toe-in. Theory was that you wanted the windward blade at zero angle when flying hull/blade nearly all the way out. Typically haveing some weather helm applied, putting the leeward blade angled to weather a few degrees, placing the weather blade dead center (due to ackerman effect).
Nowadays, most of the fleet goes with zero toe in.
Mike Dobbs Tornado CAN 99 "Full Tilt"
| | | Re: Rudder Alignment
[Re: Tornado]
#146101 06/19/08 06:39 AM 06/19/08 06:39 AM |
Joined: Jun 2001 Posts: 12,310 South Carolina Jake
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Posts: 12,310 South Carolina | Old Skool T drivers used to setup 1-3mm of toe-in. Theory was that you wanted the windward blade at zero angle when flying hull/blade nearly all the way out. Typically haveing some weather helm applied, putting the leeward blade angled to weather a few degrees, placing the weather blade dead center (due to ackerman effect).
Nowadays, most of the fleet goes with zero toe in. The ackerman angle is due to the fact that the rudder arms, as they leave the head of the rudder, are bent inward toward each other. When turning, this makes the outside rudder turn less and the inside turn more (in theory because the outside hull is going to need to sweep through a larger radius). Ackerman angle doesn't have anything to do with alignment (EDIT: when pointing straight ahead). The explanation I've always heard is, as you say, when flying a hull if you watch the windward rudder enter the water; with toe-in, it enters the water cleanly...with them both aligned perfectly straight, you see the rudder enter the water with a degree of misalignment. My feeling, is that I want both rudders working to steer the boat - not just one. The fact that they both point in the same direction should be a good thing. When flying a hull, the one rudder has to carry the load of the whole boat (imagine what it would look like entering the water)...I would rather have both of them working together resulting in a (slightly) lower angle of attack for both.
Jake Kohl | | | Re: Rudder Alignment
[Re: Ventucky Red]
#146102 06/19/08 07:24 AM 06/19/08 07:24 AM |
Joined: Aug 2005 Posts: 2,921 Michigan PTP
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Posts: 2,921 Michigan | I aim for about 6 inches of toe in, I get scared if I go too fast. On the 31 I go with about 9 inches. <img src="http://www.catsailor.com/forums/images/graemlins/grin.gif" alt="" />
Last edited by PTP; 06/19/08 07:48 AM.
| | | Re: Rudder Alignment
[Re: Jake]
#146103 06/19/08 01:53 PM 06/19/08 01:53 PM |
Joined: Jul 2001 Posts: 1,200 Vancouver, BC Tornado
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Posts: 1,200 Vancouver, BC | My point about ackerman was that with a toe-in angle setitng, while the leeward blade is slightly angled to weather countering boat wanting to turn off wind (ie weather helm), the windward blade is at the dead center/zero angle...the blades don't turn equally at the same angle due to ackerman angle settings of the tillers. Otherwise, I think we agree... <img src="http://www.catsailor.com/forums/images/graemlins/laugh.gif" alt="" /> Old Skool T drivers used to setup 1-3mm of toe-in. Theory was that you wanted the windward blade at zero angle when flying hull/blade nearly all the way out. Typically haveing some weather helm applied, putting the leeward blade angled to weather a few degrees, placing the weather blade dead center (due to ackerman effect).
Nowadays, most of the fleet goes with zero toe in. The ackerman angle is due to the fact that the rudder arms, as they leave the head of the rudder, are bent inward toward each other. When turning, this makes the outside rudder turn less and the inside turn more (in theory because the outside hull is going to need to sweep through a larger radius). Ackerman angle doesn't have anything to do with alignment (EDIT: when pointing straight ahead). The explanation I've always heard is, as you say, when flying a hull if you watch the windward rudder enter the water; with toe-in, it enters the water cleanly...with them both aligned perfectly straight, you see the rudder enter the water with a degree of misalignment. My feeling, is that I want both rudders working to steer the boat - not just one. The fact that they both point in the same direction should be a good thing. When flying a hull, the one rudder has to carry the load of the whole boat (imagine what it would look like entering the water)...I would rather have both of them working together resulting in a (slightly) lower angle of attack for both.
Mike Dobbs Tornado CAN 99 "Full Tilt"
| | | Re: Rudder Alignment
[Re: Tornado]
#146104 06/19/08 03:36 PM 06/19/08 03:36 PM |
Joined: Jun 2001 Posts: 12,310 South Carolina Jake
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Posts: 12,310 South Carolina | I dunno if we agree or not <img src="http://www.catsailor.com/forums/images/graemlins/smirk.gif" alt="" /> ... and it's a silly little point but you can align rudders perfectly straight even with ackerman built into the rudder heads. Only when you start to turn do the rudders become "mis-aligned".
But I think I see what you're saying in that even when you do align them straight (on dry land), when sailing, you have to turn them slightly to maintain heading...which then gives you a slight toe-in when under sail. I hadn't thought of that...hmmm...perhaps a little toe-out is in order <img src="http://www.catsailor.com/forums/images/graemlins/grin.gif" alt="" />
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