Toed-in Leeboards?

[DeanWhitlock]

I'm adding a sailing rig to a 13' Nordic pram that I built at WoodenBoat School (great course, great instructor [Bob Elliot], take it!). I plan to use leeboards but have been agonizing over the placement fore and aft. The point of widest beam, where the boards will naturally lay parallel to the keel, is probably too far aft for proper balance (haven't tested it yet, but that's what it looks like). I'm using the Shellback sail plan, borrowed from a friend (and sail kit from Sailrite - also very well done). It would be hard to change where the mast will go (through the forward seat). Moving the leeboard forward and having building in wedges to straighten it out will require some potentially ugly additions (and add weight). I would prefer to leave the hull as unchanged as possible.

Here's the issue: A friend told me that some boats with twin keels or boards had them toed-in slightly. Something to do with hydrodynamics. Seems to me like it would just increase drag. On the other hand, moving my boards a bit forward would naturally toe them in, so...

Has anyone any advice to offer? (ho-ho)

Thanks,
Dean

[Walcheren]

I remember reading about this. In the index you find that there are articles in W.B. 22 and 38 about leeboards. Maybe they are of help to you.

[imported_Conrad]

There are two things you can do to improve the windward performance of your boat- either "toe in" the boards, or make them asymetrical, so that the lift is maximized in one direction only. If you opt to toe them in, cant them no more than about 5 degrees to the center line, with the leading edge in. Remember that you should be sailing with only the leeward board lowered, if you sail with both down, drag will be increased significantly, even for freely pivoting boards (i.e., up/down, and in/out).

There's no reason why you can't attatch spacing blocks to the boards instead of the hull to provide the proper orientation, thus freeing the hull from ugly additions.

[DeanWhitlock]

Conrad, many thanks for the info about toeing-in and even more for the suggestion about putting the wedges on the leeboards themselves. Should have been obvious (or, to put it in the vernacular, duh!). Both of those should solve the problem.

Any suggestions on the best way to attach the boards? I have the Canoe Rig book (which is beautiful and filled with tons of great info), but I don't have the capability to manufacture the cam-locking bolts it shows. I'm trying to come up with something I can put together with off-the-shelf parts. Last time (on a small canoe) I used a large bronze bolt and a wingnut. Not bad, but I constantly worry about losing the nut!

Thanks again,
Dean

[htom]

Look at the rope scheme used in the Marco Polo pram (LFH's Sensibe Crusing Designs p125.) Leeboard has two holes, a rope goes through the holes, one end over the gunwale, the other through a hole in the sheerstrake. Both ends tied off inside. (He actually shows two ropes, but I see no great reason for that.)

[TomRobb]

It's hard to imagine a leeboard installation that isn't ugly. The best case spin might be homely :D
Phil Bolger has experimented w/ leeboards as much as or more than anyone else. You might profitably read up on his take on them. IIRC, he advised against toe-in because it's too easy to over-do it - a degree or two comes to mind, but I'd check to be sure. Asymetric foils might be a better way, and the wedge on the board rather than the hull, as has been said here.

[ 03-07-2003, 09:34 AM: Message edited by: TomRobb ]

[DeanWhitlock]

Thanks all for the advice and even the aesthetic comments. I agree that almost all of the leeboard installations I've seen have been "quaint," if not downright ungainly. However, they do work (I've used one on a canoe) and there's even a very nice looking design in "Canoe Rig, The Essence and Art," by Todd Bradshaw, available from WB store. Check out page 155. This wouldn't be the most efficient leeboard in the world, but it has a wonderful "classic" look to my eye, quite suitable for a traditional boat like my Nordic pram, which will be sporting the standing lug rig designed for the Shellback dinghy.

Anyway, thanks again. I appreciate all the input.

Dean

[brian.cunningham]

CLC's uses leeboard on thier canoes and SailRig setups. http://www.clcboats.com
http://www.clcboats.com/images/millcreeksailrig1.jpg
The float hide it on the trimaran setup.
http://www.clcboats.com/images/sailrig2.jpg

EpoxyWorks ran a nice article on sailing canoes so equiped
http://www.westsystem.com/webpages/images/epoxyworks16/04-Modern.jpg
Modern decked sailing canoes - By Hugh Horton (http://www.westsystem.com/webpages/epoxyworks/16/modern.html)

But, the best looking leeboards installations I've seen are on Thame's river barges
http://www.thamesbarge.org.uk/barges/active.html
http://www.thamesbarge.org.uk/barges/barges/centaurhalf.gif

[Todd Bradshaw]

Dean,
Keep in mind though, that the leeboards on page 155 of Canoe Rig are presented and suggested as a shallow water system, mostly for people who want to do a lot of thin-water gunkholing. For those who haven't seen the book, they are fairly short and teardrop-shaped, like some of the Dutch boats had and the suggested construction is wood strip/fiberglass, similar to a beefed-up version of an early Ralph Sawyer marathon canoe paddle.

Most of us aren't crazy enough to go screaming along in a blow in two feet of water assuming that there is nothing down there to hit, so my general assumption was that their typical use would be in light wind conditions at reasonably slow speeds. The boat would be fairly level and probably have both port and starboard leeboards down and working. Putting the same type of boards on a wider hull and heading off into deep water in higher winds and at greater angles of heel, it is fairly likely that you might find that they lacked sufficient "bite" to do the job.

It might be possible to stretch the shape, elongating it for more depth or just up-size the whole board and it's scantlings. The Dutch boards that I've seen were generally quite large compared to what most of us are used to. One good thing about leeboards is that there is no limit to how many of them you can build. Changing to a different size or shape is pretty simple compared to making most other hull or rig modifications on sailboats.

[ahp]

If you use assymetric boards, the flat side goes out. Rather than any old convex curve on the inside, do some reseach on foil cross section. From my model airplane days I remember the "Clark Y" was widely used.

[DeanWhitlock]

Hi Todd, Thanks for joining in. My compliments on your book! It has been a great resource for this project.

Regarding the Dutch-style leeboards, I did plan on elongating them a bit. I have more freeboard on the pram than on a conoe so they need to be longer just to reach the water, but also wanted to get a bit more depth below the hull. (Am I right in assuming that the only effective part of the leeboard is the part that extends below the keel?) However, I will occasionally be sailing in shallow water on the Connecticut River, and also whenever I put the boat in and take it out. Our local lakes are deep but most of the boat landings don't have floats so I'll be running off the beach (or rocks, as the case may be). So shoal draft is not a bad thing in this instance. As for construction, I'll probably go with solid lumber, splines, and good glue. I'm allergic to epoxy hardeners (suffered through building a stripper canoe) and don't like messing with that much chemistry anyway!

Regarding the concept of shaped asymmetrical foils (did I spell that right?) that ahp mentioned, it seems that on this particular boat, which I never plan to race, the gains in efficiency wouldn't really be worth the effort of determining the proper shape and then trying to carve it into the boards. Any thoughts on that anyone?

Thanks,
Dean

[RCullison]

Dean,

I seem to remember a comment by Phil Bolger that the effective plane of a leeboard is from the waterline, so they don't have to be as deep as an equivalent centerboard. It seems reasonable, especially on a boat with a rounded bottom where the board stands away from the hull below the waterline.

[DeanWhitlock]

Now that you mention it, I vaguely remember that, too, though I'm not sure which Bolger book it was in. It does seem that a flat plank would put up more resistance than a rounded hull. If so, that will make my job easier (and a little cheaper). I had calculated the "below-keel" area of the Shellback daggerboard and was planning to make a leeboard that gave me the same area, also below the keel. Seems as though I can now make that be the "below-water" area, or maybe halfway in between. As Todd said, if it doesn't work too well, I can always make another one. Thanks.

[N. Scheuer]

A few quick thoughts before work:

American Small Sailing Craft discusses toed-in leeboards in a chapter about Scow Schooners.

Contrary to the above that leeboards are for very shallow draft, and therefore not suited to "speed"; tell thet to the Meadowlark ketch I was chasing on vineyard Sound ten years ago in my Dovekie, the Pilgrim Pelican. I believe the Meadowlark was headed for Nantucket. Both designs have leeboards, of course.

Phil Bolger would disdain assymetricic (lifting foil) leeboards, as well as any toe-in. He's said as much many times, believing both tricks lead mostly to increased drag under any but optimum circumstances. Tell that to the ?Shearwater yawl, Ardea, which will outrun and outpoint my Shearwater, the True North.

I am now making a set of assymetric leeboards so I can keep up with Ardea.

believeing leeboards to be attractive, Moby Nick