How to equip a dingy with a leeboard?

[overland]

I've seen references to a Bolger leeboard but I can't find instructions on how to make or install one. Can someone point me the right direction?

[johngsandusky]

I have some of his books, there are likely diagrams.
An internet search "leeboards" shows lots of images. My canoe uses a clamp on thwart to hold the leeboard, my kayak too. I plan to use a similar system on my dory tender.
Good luck, keep us posted.

[overland]

Yes, I've noticed that there are a lot of pictures on the internet--some commentary, too--but I couldn't find instructions on how to make it or mount it. But I'll keep looking.

[Dave Hadfield]

I made one for each of my plywood dinghies as per the directions in Bolger's Elegant Punt. Just slide-on over the gunwale. The inside guides/arms bracket the midships thwart, so the thing can't pivot.

It's amazing how well they work, even on the "wrong" tack.

[overland]

That's very clever. The inside bracket goes all the way to the bottom of the boat, or just partway? How long is the board--and what did you make it of?

[Breakaway]

Another method: http://www.jimsboats.com/webarchives/1998/15jun98.htm

And another: https://www.simplicityboats.com/summerbreezetemp.html

Kevin

[Dave Hadfield]

That's very clever. The inside bracket goes all the way to the bottom of the boat, or just partway? How long is the board--and what did you make it of?

Yes, pretty much to the hull bottom. The dimensions are specified on the EP plans, which are free online in various places.

I think I glued together 2 pieces of 1/4" plywood, hoping there would be less warp or twist. It worked.

Dave

[rgthom]

Martyn Long in UK made a leeboard for his Walkabout. Not to any plans, but it looks a lot like Michalak's pivoting design. He gave me permission to post his photos, they are in a Flickr album here: https://www.flickr.com/photos/ricks_...57634273016114

[Brian Palmer]

I made one for each of my plywood dinghies as per the directions in Bolger's Elegant Punt. Just slide-on over the gunwale. The inside guides/arms bracket the midships thwart, so the thing can't pivot.

It's amazing how well they work, even on the "wrong" tack.

I built one of those when I was 14. Somebody who thought they knew better guilted me into building a second leeboard. Completely unnecessary.

[Brian Palmer]

Some folks have added a lee board to a small dinghy that is just held to the side of the boat with a lanyard running from the top of the board to the center of the middle thwart. Water pressure holds it in place and it is switched side to side.

[stromborg]

Iain Oughtred's "Feather Pram" uses the lanyard. I haven't tried the sailing rig yet so can't comment on how well it works.

[jpatrick]

My old Sabot had a leeboard held by a bronze fitting. All the Sabots were rigged like this as I recall. This is a modern version that I found on the web. I suspect that a bronze one could be found somewhere.

iu.jpeg

Jeff

[dutchpp]

This is the traditional Dutch way for large leeboards. Simplified and scaled down it could be used for a dingy.
zwaardconstructie.jpg
In real life it looks like this on my own boat.
IMG_0242.jpg
I saw someone on a small dinghy once who made a kind of locking mechanism ( similar to removable tow bar's on cars) so that he could use 1 leeboard only but still could use the advantage of the dual axis mounting system as shown on my boat ( you can adjust for lee worthiness etc.). I'm afraid I don't have pictures of this clever construction.

[overland]

One problem I have is that there's no thwart amidships, where the boat is widest. The nearest thwart is a little forward of that, where the gunwale turns slightly inward.
Also, I don't know how to determine my sail's center of balance.

[Etdbob]

You said your sail was nine feet on a side?

That's a little smaller than a Snark sail, I have no idea where yours came from.
Finding the center of effort is easy.

Lay the sail out flat on the lawn. With a tape measure find the center of one side and mark it with tape.
Do the same for the other two sides.
Use string, and stretch a line from the center of each side (that you marked with tape) right across the sail to the center of the opposite side.
Where the lines intercept is the center of effort - Mostly anyway, and good enough for our purposes.

You can read up on the subject here -

http://www.jimsboats.com/webarchives/2013/15nov13.htm


Mark the center with tape on the sail.
When it's set up in the boat the center of effort should be somewhere from just behind the leeboard, to maybe in the center of the leeboard. .

The leeboard MUST be in the center of the boat, at the widest part, and perfectly parallel to the hull. Move the mast step to get the center of effort in the right place.

The Bolger clip-on leeboard is 4 feet long and a foot wide. It can seaily be made from 1/2 plywood as specified, but I'd make it from two pieces of 1/4 inch plywood laminated together. Titebond II or even III is fine glue for this purpose.

You'll need to fasten a horizontal stringer onto the outside of your boat to support the lower part of the leeboard. I't intended to rest on an external chine, which your boat probably doesn't have.




You can see what I mean in this photo of a model outrigger I made that uses this leeboard. The fact that you don't have a thwart in the center of your boat makes it ideal for this leeboard.

SAM_8933.jpg

[overland]

Thanks. I think the sail is from a super snark. Could I re-use an old aluminum centerboard for the leeboard?

[Breakaway]

^It is probably not long enough....but sure, you could.

Kevin

[Etdbob]

You could use almost anything thin and rigid enough. I know of one sailing canoe with a leeboard made from an aluminum traffic sign.

The centerboard you have may not be big enough. Can you measure it?

As a very general rule of thumb, I'd say you'd need about two square feet of leeboard under the boat with that sail.

Say something a foot wide and two feet deep, more or less.
Technically speaking, leeboards are the least efficient lateral plane so they probably need to be bigger than a centerboard or dagger board. The boat would likely sail best with a daggerboard case glassed into the boat at the right location, but there is no reason you can't experiment with a leeboard to get you going.

This is an example of a very simple pivoting leeboard -







https://www.simplicityboats.com/summerbreezetemp.html

The Bolger style clip on board has the advantage that it doesn't add clutter or weight to the boat when you are not going sailing.

[YukonHarbor]

This old thread is interesting to me because I'd like to build a small pram to row and sail that has maximum room inboard, including the room a centerboard would take up. And related, I'd like that pram fitted with a sprit rigg that could be brailed and stowed easily inboard in a moment.

Philip Bolger's clip-on leeboard design is intriguing; but at a glance it seems hazardous in a shoal crash. Maybe that could be improved by giving it the ability to swing up, with the clip inserting into a sort of cam shaped constraint between frames--so as it swings up and aft, it simultaneously rolls forward on the gunwale.

A few points that can be seen on the sample picture portions of Bolger's plans (i.e. Nymph, Teal; www.instantboats.com) with clip-on leeboards: The tangent of the widest part of the hull is parallel with the keel, exactly where the leeboard mounts so it's also parallel. The leeboard mounts nearly in line with the sail centroid (Having to do with tacking?). And for the leeboard to drop straight into the water, the topsides are near perpendicular to the water line.

This constricts Bolger's designs quite a bit. If changing the sail, say to a spritsail, the centroid of the sail would need to be kept aft of the leeboard. Moving the leeboard forward would entail either moving the widest part of the hull forward (which would verge on weirdly bulbous), or greatly modifying the mount abeam of the topside. Also the greater the flair of the topside the more the leeboard would slant inward unless a really wide rub rail were mounted to the hull.

So here I am still looking around. There's a lot of gray physics there. Does anyone know a small pram/leeboard design that really encompasses an all-around solution? If so I'd like to hear about it.

[Ben Fuller]

I wrote up the lanyard and leeboard for a recent Ash Breeze, the magazine of the Traditional Small Craft Association. It lends itself to exprimentation as the only mod needed on the boat is a hole in the center thwart.

[MushCreek]

I'm toying with the idea of adding a modest sailing rig to a rowboat I'm building. It would be self-contained, supporting both the mast and the leeboard(s). The only permanent piece in the boat would be a mast step on the keelson. It would clamp to the rails in 4 places, two per side. The hard part is making the part that holds the leeboards strong enough to handle the considerable stresses of a leeboard supported at the top only. Placement in the hull wouldn't matter as much, as the part holding the leeboards would keep them parallel to the keel.

[Brian Palmer]

This old thread is interesting to me because I'd like to build a small pram to row and sail that has maximum room inboard, including the room a centerboard would take up. And related, I'd like that pram fitted with a sprit rigg that could be brailed and stowed easily inboard in a moment.

Philip Bolger's clip-on leeboard design is intriguing; but at a glance it seems hazardous in a shoal crash. Maybe that could be improved by giving it the ability to swing up, with the clip inserting into a sort of cam shaped constraint between frames--so as it swings up and aft, it simultaneously rolls forward on the gunwale.

A few points that can be seen on the sample picture portions of Bolger's plans (i.e. Nymph, Teal; www.instantboats.com) with clip-on leeboards: The tangent of the widest part of the hull is parallel with the keel, exactly where the leeboard mounts so it's also parallel. The leeboard mounts nearly in line with the sail centroid (Having to do with tacking?). And for the leeboard to drop straight into the water, the topsides are near perpendicular to the water line.

This constricts Bolger's designs quite a bit. If changing the sail, say to a spritsail, the centroid of the sail would need to be kept aft of the leeboard. Moving the leeboard forward would entail either moving the widest part of the hull forward (which would verge on weirdly bulbous), or greatly modifying the mount abeam of the topside. Also the greater the flair of the topside the more the leeboard would slant inward unless a really wide rub rail were mounted to the hull.

So here I am still looking around. There's a lot of gray physics there. Does anyone know a small pram/leeboard design that really encompasses an all-around solution? If so I'd like to hear about it.

I built and sailed a Bolger Elegant Punt with the clip-on lee board. I am sure I ran aground at least once and never had any damage. The "clips" could be easily replaced. I also used a smaller sail than the one designed with the mast in the original location and it was fine. It was simple. It worked. It was good little boat.

[johngsandusky]

I'm toying with the idea of adding a modest sailing rig to a rowboat I'm building. It would be self-contained, supporting both the mast and the leeboard(s). The only permanent piece in the boat would be a mast step on the keelson. It would clamp to the rails in 4 places, two per side. The hard part is making the part that holds the leeboards strong enough to handle the considerable stresses of a leeboard supported at the top only. Placement in the hull wouldn't matter as much, as the part holding the leeboards would keep them parallel to the keel.

That's how I sail my canoes. The BSD Classic Canoe 36 uses a single aluminum thwart that attaches to the gunwales and carries mast partner and leeboards.

[YukonHarbor]

I built and sailed a Bolger Elegant Punt with the clip-on lee board. I am sure I ran aground at least once and never had any damage. The "clips" could be easily replaced. I also used a smaller sail than the one designed with the mast in the original location and it was fine. It was simple. It worked. It was good little boat.

What happened with the leeboard when you ran aground, did it push up. Do you think the leeboard’s round bottom helps with that?

[Woxbox]

I've tinkered with leeboards a bit and came to prefer the old canoe-style clamp-on boards. This allows you to adjust the board position for best balance, is totally removable, and will kick up if it hits bottom.

The general assembly



One ready for service:

[Brian Palmer]

What happened with the leeboard when you ran aground, did it push up. Do you think the leeboard’s round bottom helps with that?

It was 40+ years ago. I think it pushed up and back, but I don't remember it breaking.

[tri-guy]

I used a similar approach to Dave for several Whisp sailing rigs. They worked fine. The crosswise support is slotted so the inwale clamps can be adjusted to move the whole assembly fore and aft. This version shows a large bronze wing nut on the pivot, but a bent piece of bronze rod brazed to a nut worked better.


whisp5.jpg

whisp and charlotte3.jpg

[johngsandusky]

Some of my rigs clamp onto the gunwale. The canoe one lashes on, which is strong enough to hold the leeboard and mast partners.