Leeboards and swing rudders

[RHamel]

I recently removed the leeboards from a 33' Herreshoff Meadowlark at the owners request and replaced them with fixed bilge keels. The bilge keels are much shallower (15"), but longer (5') and seem to be working well tracking with minimal slipage. The rudder still has a 5' swing tail with about 80 lbs of balast. I would like to remove this tail and replace it with a fixed rudder. The owner has posed several questions: 1) Does the balast actually help to balance the boat or is it just there to assure that the rudder will swing down when you release the rope? and 2) Does the rudder swing deep only in order to work with the leeboards? If this is true and the leeboards are no longer there, why would we still need a deep rudder? Advice,opinions, or further discussion is greatly appreciated. Thanks.

[Thad]

1) the rudder ballast is primarily to keep the rudder down but will have a minimal stability function (probably not involved in stability calculations). 2) The rudder swings deep to give good steering "grip" and swings to lift when she take the ground, as that boat is designed to do. If you can get the rudder deep enough to steer in a sea with the rudder bottom level with the bottom of the bilge keels you could probably go with a level bottom rudder but regret it later. LFH calls for a 3' long hinged blade. He shows a small lead insert but does not specify a weight or mention it in the discussion. I think 80# excessive and no more than 20# necessary, but would also think the depth of the drop rudder a good thing.

[sailboy3]

I would stick with the drop rudder also.

[Jay Greer]

Were the lee boards built to the original design? The boat proved to need a higher aspect ratio for the depth of the boards, although LFH never corrected the problem on the drawings. I would be interested to hear how it performs with the bilge keels going to weather. There is no need to ballast the rudder but there is need for the aspect ratio to favor the depth in order to have adequate control.
Jay

[kenjamin]

The Meadowlark seems like one of the few designs where the leeboards look "correct". I'd be curious also to hear how the new bilge boards perform.

http://ford.physics.fsu.edu/meadowlark.jpg

[Ian McColgin]

What's done is done though why anyone would want a boat that could dry out in 12" of water to suddenly require over two feet is beyond me. This person has never dried out on a sandbar with any sort of current and then had to dig the bilge keels free of swirled in sand in order to have any chance of floating off as the tide came back. Not restful.

But anyway, a longer shallow rudder could take the place of the deeper drop rudder. It would require more force to steer, create more turbulence and less lift on the wind. And its length makes it more vulnerable to banging into stuff. The drop rudder can be raised and held up a bit if you don't like it dragging on a shoal and that will give a feel for the shallower longer rudder. In other words - you already have the option built in with the advantage that in deep water you can go to the narrower deeper blade. Why fix something that's not broken?

[RHamel]

As far as I know the leeboards were built to the original design, but one was damaged and replaced before I got the job of restoring this vessel. When I removed them I was curious to find one weighed 95lbs and the other 125lbs, a bit lopsided for sure. We were concerned that if we replaced them with fixed bilge keels that one would always be dragging while the other one worked. The owner was willing to sacrifice this possible mal-performance for the ease of not having to work the leeboards. He is not a young man anymore and they are a lot of work. However, this did not seem to pose any problem at all. I constructed the fixed keels with 316 stainless, 1/2" thick, 15" deep and 5' long tapered at each end. Work great! But now back to the rudder issue... it's seven feet deep in the water and 80lbs hanging off the transom! The torque on it has twisted the stock and busted an Edson heavy duty cast bronze rack and pinion steering mechanism. I need to cut at least some of it down. Question is how much?

[JimD]

The Meadowlark seems like one of the few designs where the leeboards look "correct".

The only reason they look "correct" in that photo is because you can't see them. ;)

[Thad Van Gilder]

I believe I know the meadowlark in question... Its at Gregg Neck Boatyard in Galena, Md, and last summer when I talked to the owner, he said she sailed the same with or without the leeboards.

I thought that was bogus, but who knows.

-Thad

[RHamel]

Yup, that's her.

[Ian McColgin]

I grow more concerned about this project. As I am sure RHamel has noticed from his own copy of the Meadow Lark plans, the rudder he describes bears little resemblance to the 4' long blade, maybe 3' depth rudder I recall on the Meadow Lark I've sailed. It had a light helm on the tiller and I can't see why anyone would clutter such efficient and inexpensive simplicity - hallmarks of LFH designs in general and this one in particular - with an expensive R&P and monster blade.

I'd back away for a moment, take the lines off the boat, study the rig as provided, and figure out in exactly what ways this still resembles a Meadow Lark. It may take a bit more refiguring than first thought.

One stray thought though, when the blade is raised back to horizontal for very shallow cruising, it will exert a lot of torque. A blade 125% designed length -- if my memory is right which it might not be -- will generate considerably more than that porportion added torque when used horizontal.

G'luck

[ahp]

Not only will the rudder be more effective when it is down (vertical), the pull on the tiller will be much less.

[RHamel]

Thanks Ian. We'll study our options carefully.

[Thad Van Gilder]

IIRC that boat was built in the backyard by the current owner's father.

-Thad

[donald branscom]

As far as I know the leeboards were built to the original design, but one was damaged and replaced before I got the job of restoring this vessel. When I removed them I was curious to find one weighed 95lbs and the other 125lbs, a bit lopsided for sure. We were concerned that if we replaced them with fixed bilge keels that one would always be dragging while the other one worked. The owner was willing to sacrifice this possible mal-performance for the ease of not having to work the leeboards. He is not a young man anymore and they are a lot of work. However, this did not seem to pose any problem at all. I constructed the fixed keels with 316 stainless, 1/2" thick, 15" deep and 5' long tapered at each end. Work great! But now back to the rudder issue... it's seven feet deep in the water and 80lbs hanging off the transom! The torque on it has twisted the stock and busted an Edson heavy duty cast bronze rack and pinion steering mechanism. I need to cut at least some of it down. Question is how much?

One inch thick STEEL swing down keels get bent all the time.
Your stainless one in more malable than steel, and if it does get bent it will then be work hardened and will be impossible to straighten out.
I would get rid of that stainless drop board pronto before it damages your boat.
About your rudder design.
For every foot that sticks out from a pivot or anchor point the force is multiplied times 1000. So if there is 80 lbs pressure and the rudder is 5 feet then that is 5000 X 80 lbs or 40,000 lbs. force! otherwise the breaking point of a 3/8 bolt!
You can look up all this stuff online too.
At least with wood it can be repaired or replaced. Swing down keels usually work best when 1/2 depth in most situations.

Another concept. Sharpies had swing down keels made with white oak but the swing keel was in the center of the boat and was basically a triangle presented to the water with the point sticking down so the boat would just spin on its axis at will when the board was down.

When using bilge keels one is supposed to be down and the other one UP. Never both being used at the same time unless you want something broken. The forces being applied are supposed to push on the hull of the boat, NOT pull on the side of the boat.

[Ian McColgin]

Twin bilge keel boats are a dime a dozen in England. Great for harbors that dry out. Twin bilge keels are fixed. Twin bilge boards are, like centerboards, retractable into a trunk.

This job has elements of both. The length is akin to twin bilge boards. One important reason for bringing the weather board up, quite beyond skin resistance, is that the leading waves from the two boards are likely to meet ahead of the boards' trailing edges and produce dragging turbulence. Even moderately high aspect twin bilge keels - not deep but sort of short, must be very carefully designed or the boat will be a slug.

I'd love to get under this boat with her anchored in a strong current (and also be well tethered) with a bag of marsh mud to twiddle into the current stream and watch what happens.

In the usage to which I'm used, a swing keel is distinguished from a centerboard by ballast. A sharpie's wooden swinging appendage is a centerboard. It's absolutely true that a properly made wooden board can take abuse no tin fin can withstand. I've told before of ramming the beach on a hard beat with Goblin and feeling her 12 tons basicly flick her buttocks as the drifted oak board deflected and came straight. A friend's sloop with a steel centerboard (heavy but still a centerboard, not really a swing keel of significant ballast) bent his board the same way and it was a major pain to get the plate out, build a fire to heat it, and bang it straight.

I don't follow Donald's musings about added force but, extrapolating from a simple lever, it looks to me that adding about 25% to the blade length should, in the horizontal position, add about 50% to the overall torque on the rudder post.