Make and Make Do

By Rob Rohde-Szudy - Madison, Wisconsin - USA

 

Living With Daggerboards

Bolger’s Light Schooner is drawn with a simple daggerboard arrangement that I did not want to mess up. Of course daggerboards do not kick up. They kick the boat. An answer is provided in issue 164 of WoodenBoat. On page 44-46 Lang Warren describes a rotating daggerboard. The “cap” is held in by a pin and the board is held up into the case by buoyancy. A shock cord holds the board vertical, but stretches when it hits something, automatically returning to full down when the obstruction has been passed.

The more I thought about this, the more it seemed like a pain in the butt to insert and retrieve. It would try to fall apart every time. Not only that, when running onto a bar, you could get it stuck under the boat with no way of retracting it! Now THAT would be bad. Then it occurred to me that the shallow mudflats we call lakes in the middle of the country are totally different from the essentially deep water full of granite shoals off Maine. I didn’t need to take THAT much stress off the hull, just reduce the impact to keep the board from slicing right through a bulkhead. Difficult when hitting granite. When hitting mud or sand, I think I might get away a simple shock absorber.

So I figured I’d make rubber bumpers. I cut a couple pieces from a large rubber stopper – lab surplus – and screwed them to the top edges of the daggerboard. Then I opened up the entire top of the daggerboard case, which allowed an extra 2” travel both fore and aft. This space was taken up by the rubber bumpers mounted to the daggerboard. Yes, I could have mounted them to the case, but it was easier to mount to the board. And easier to replace them if I managed to ruin them.

Well I did ruin them. Almost immediately, too. Knocked them right off when stowing the board on the floor of the boat! (Another disadvantage of daggerboards!) But guess what… the daggerboard still stays in place from gravity unless I hit something! When I run into shallows with a muddy bottom, the board lifts a little and bumps against the for’d bulkhead. It bumps a little harder if I hit sand or rock, but it’s still not terribly hard. I suppose wedging the rubber back in the slot would still gain me a little shock-absorption when I’m going really fast, though.

Either way I can still yank the board up and out of harm’s way – not possible with the WoodenBoat system in a steadily shoaling situation.

An interesting note, however: In the same issue of WoodenBoat on page 47 Robb White describes a PIVOTING daggerboard that could be useful to those with short boats. I will not attempt to describe his board, except to say that it can shift its area forward or aft of its center detent. Very cool. Very handy in a dink, I should think. The system would apply easily to Michalak’s double-braced leeboard system. What was especially cool to me, though, are what he calls “Bernoulli Bumps”. As his daggerboard case is open at the top, it tends to turn into a geyser underway, a problem shared by my motor well. He tried many things to seal it and none really worked, so he switched tack to reducing the pressure. Bernoulli’s principle is well known to any sailor – when a fluid is forced to move faster, its pressure decreases. This is why sails draw, wings lift and carburetors suck. The clever Mr. White put two strips of wood maybe 1/2" x 3/8” on the bottom, one about 1/4" to each side of the daggerboard slot. Underway, this works like a dinghy bailer and creates a suction that reduces the water level in the daggerboard case when underway. Clever fellow, that Robb White.

Draft control

It turns out the most annoying part of a daggerboard is the inability to sail away from shallow piers. That is apparently the only kind of piers there are in southern Wisconsin. I knew this was a problem for sailing, but it is also a problem for motoring sometimes.

This was driven home for me one day when I tried to launch in 15-20 mph winds. The water at the pier was only three feet or so deep – shallow enough that I couldn’t put the board down. I tried to motor out to deeper water, but the windage of the masts well forward of the rudder would not allow me to steer anywhere but downwind. Even full motor power, full rudder AND opposed oar strokes could not turn the boat. There was just too much force on two masts forward pulling against the resistance of one board (the rudder) aft. I might have done a little better by steering with the motor, but I still don’t think it would have come all the way around.

Reversing the motor would just hold us against the wind at full throttle. Unfortunately, I was testing the motor after a repair. The repair wasn’t quite done, I guess, so it decided to quit. And my anchor wouldn’t grab in the weedy bottom and we fetched up on a private pier of one of those expensive waterfront houses. Fortunately nobody was home. Even more fortunately, the schooner is light enough to fend off by hand with little way on. I started taking the rig down in anticipation of a very hard row. My wife, being the smart one, suggested we simply stepped out in the four feet of water and walk the boat back to the pier. We did.

Clearly I needed some lateral resistance forward to be able to motor across a strong wind. At least with the masts up. And that resistance had to be shallower that the daggerboard. After I identified this as the problem, my wife asked why I didn’t just put some holes or notches in the board, to support it at different levels. Like I said, she’s the smart one. In a grand total of ten minutes including painting, I drilled one hole and cut a metal pin.

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(click images to enlarge)

Now I can set my draft to about two feet and motor easily across the wind. I can even sail under reduced sail without too much leeway. Anything is better than the 100% leeway I was making before! As if to drive the point home, we went out on the same lake without the motor and launched, sailed and re-docked. All this was under sail and only possible because of the reefed daggerboard.

But that pin needs a lanyard! I lose it all the time. I really must get around to drilling a hole in it.

But I still haven’t ruled out getting rid of that daggerboard and switching to the Michalak leeboard setup. Michalak’s system looks unwieldy, but in operation it’s the most convenient, foolproof system I’ve ever had the pleasure to use. The disadvantage is it’s more stuff out there to catch the water and induce roll when motoring. But for sailing I could gain a performance boost by putting one on each side and optimizing the foil shapes and angles. Like the bilge boards in those fast racing scows, but easier to get to. Hmmm…..

Delamination

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I should mention another problem I had with this daggerboard. It started delaminating in the first couple months. The boat was made from the same stuff, but had few problems. I suspect this is the unprotected endgrain on the board. Paint does little to keep water out. So I sanded it down and encased the entire below-waterline part with glass cloth and polyester resin. No more problem, even after taking a beating.

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Motoring

Another annoyance with a daggerboard occurs when motoring. When the board is not in the slot, the forward motion of the boat sloshes water directly upward. The only spray coming aboard is most often from that slot, which is quite annoying to me. Stuffing a sponge in the aft end of the slot helps a little, but only a little. So I set about fixing this.

The most obvious approach would be to make another daggerboard, but cut off so it just plugs the hole. But I was afraid some of that water would still spray through. And it seemed to me that the drag of the slot benefits nobody, so why not plug it from below?

My approach used a 2” wide strip of 1/4” plywood to cover the slot on the bottom, with a “plug” of 1x4 lumber extending up into the slot to keep the plywood located. These are simply nailed and glued together. The 1x4 also gets some holes drilled into it for some light line, which cleats up on the deck. This keeps the plywood tensioned against the bottom. I suppose shock cord would be even better, but more expensive and difficult to work with. 1/8” Dacron line seems to work. Nylon would probably be cheaper and better, since the stretch would tend to pre-tension the plug against the bottom. But I had the Dacron line on hand.

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I was prepared to add a gasket of silicone caulk, but it works well without it. A little water gets into the slot, but there’s no pressure to make it shoot upward, which is all I needed to prevent. I also notice this makes the boat quieter under oars, since there’s no gurgling in the slot.

Admittedly, this plug could be inconvenient to attach. I’m fortunate that the slot lands between trailer bunks, so I can put this plug in when the boat is still on the trailer. I just drop the line with the bit snap down through the slot, clip it to the loop on the plug, and guide the plug into place a s I pull on the line. Cleating it is simple, of course. It would be trickier if my trailer didn’t accommodate this method. But on the trailer it takes me like 20 seconds. It works well too. No more wet decks!

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You may have noticed I have three holes in the plug. I thought I’d need lines at each end to get it tight enough, but I didn’t. Practically speaking, this plug doesn’t even need to be all that tight. We’re only preventing bulk water flow, not sealing it out entirely.

I even got extra fancy and made a similar plug for the top side, to avoid dropping anything into the slot.

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click to enlarge

I figured I’d never use this since it’s not like I’m playing marbles up there. But I was wrong. I almost hate to admit that it keeps the deck just as dry as the lower plug. I suspect the lower plug does more to prevent slot turbulence, but it’s not like I’m racing. I wouldn’t be surprised if in a year I’m only using the top plug.


Kick-up Daggerboards

This one is not my trick, but I think it’s a good one, so I’ll include it here. Duckworks publisher Chuck Leinweber came up with a nice way of dealing with a daggerboard on the first boat he ever built. He make the board unweighted, so it was buoyant enough to float up. Then he held it down with some magnetic strips on each “cheek” at the top of the board. These stuck to steel strips screwed to the top of the daggerboard case. This was just enough resistance that a bump on the bottom would send the board floating up, where it would wait to be shoved down again.

While I’m glad it worked for Chuck, I’m not so sure this would work in every case. The forces are greater with a huge board like the light schooner has, and particularly when going to windward, the board can be pretty forcefully pinned to the side of the case. I think I might improve on Chuck’s system by raking the reverse-daggerboard case. That is, the top of the case would be aft of the bottom, so the board would angle forward. The good part is that the board would raise itself easily when it hit something, even if it didn’t float. The bad part is that the board would tend to collect weeds. But it might be a good strategy for those who sail where it’s rocky and no very weedy. But that ain’t me!


Summary

Daggerboards are still a mixed blessing, but now they’re a little easier to live with. Maybe even easy enough that I’ll leave it as a daggerboard. And maybe not.


Rob Rohde-Szudy
Madison, WI
robrohdeszudy@netzero.net

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