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Thread: To design a ballasted daggerboard? Reply to Thread
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  Topic Review (Newest First)
03-25-2011 10:09 PM
Bene505 If the water is deep enough, make a long daggerboard with the bottom part made out of 10 pounds of lead. With a long board, that will provide a lot of stability.

If you can't go with more weight, go with more depth with the weight you can use.

03-25-2011 05:58 PM
PaulfromNWOnt What Faster said.

It would be a simple matter to make up a small set of adjustable outriggers, and turn the Opti into a sort of trimaran. The idea is to set them so they extend at an upward angle so the boat will still heel somewhat, and simply "clamp" them to the gunwhales. Yes, it will interfere with the normal handling, but as you adjust them inward this effect will be lessened along with the stability. Just like training wheels.
03-25-2011 05:10 PM
bljones I am not a physicist, or a mathematician or even a rocket surgeon, but i figure to make the daggerboard compensate for the movement of crew and resistant to heeling, the daggerboard would have to weigh as much as the crew on board, which would make it impossible for aforementioned crew to raise it.

The low-buck solution is to bundle six- eight pool noodles together for each side, wrap in a sling of sunbrella with grommets sewn along the edge, then screw the floatation to the gunwales through the grommets. Much more stable, and still sailable.

Like this:
Dinghy Dogs - A Better Inflatable

03-25-2011 02:48 PM
Faster I really doubt you can add enough 'ballast' to make an appreciable difference in how an optimist would behave without adding enough weight to seriously compromise the boat, esp in the event of an accidental gibe/wipeout.

Also if flipped now these weighted boards could slide towards the hull making righting from the water more difficult.

I think both Paul of NWOnt and ftldiver are talking about the same thing... turning the opti into a trimaran.

My understanding was that Optis are already one of the most inherently stable training dinghies.
03-25-2011 02:44 PM
aimee0742 Thanks CaptKermie!!

Yeah, I've been reading a few blogs on the hollow daggerboards being modified. I assume these are all permanent fixtures within the boards? I would like the board ballast to be adjustable to some degree i.e. I could remove the stabiliser once I've gained enough confidence. I haven't found anything else on the web like it?
03-25-2011 02:37 PM
aimee0742 Really appreciate all of the suggestions!

@jcalvinmarks; I don't intend to completly avoid a capsize at all, as its a huge part in sailing, and creating something that could do this would also put huge forces on points in the boat also. The main aim would be to keep the boat in control and stable as much as possible especially in heavy weather. I'll look into the detachable or a possible retractable bulb.

@PaulfromNWOnt, what do you mean by a 'set of amas?' It definitly sounds like something I should be looking into!

@ftldiver, had looked into pontoons! Thinking maneuverability may become an issue? Outriggers sounds like it could be viable, but, would you need on on each side, because it would only be effective on a certain tack?
03-25-2011 02:29 PM
CaptKermie It has been done and still is being done. I am seriously contemplating it myself, just a matter of making the time and taking the effort. I have a MacGregor 26M and they have daggerboards about 72" long but only 57" go below the hull bottom. They are hollow and fill with water to provide neutral bouyancy, but several owners have plugged the holes and filled the board with a 50# mixture of leadshot and epoxy and even added a steel rod down the length for added stiffness. The downside to this was having to beef up the pulley system to raise and lower the board because it is now much heavier. Those who have done it report good results but it does entail a bit of work and resources, which is why everyone does not do it.
The extra weight does not sink the boat anymore than adding an extra battery would or adding an extra person.
Adding weight to a dinghy daggerboard would not prevent a capsize completely but it would delay the point of capsize to some extent, enough to prevent 30% of them. It is not a crazy idea, but it will change the sailing characteristics to some degree, especially in a dinghy.
03-25-2011 12:20 PM
ftldiver pontoons/outriggers ?

Sure you can add 20-30# to the daggerboard, but will that really STOP a wipeout ?

and of course the boat might sink since its now heavier.
03-25-2011 11:18 AM
PaulfromNWOnt Why not a removable/adjustable set of amas? If they are of sufficient angle, they wont create drag when running, and they will still allow some heel when reaching. Since they are adjustable, you can leave them at their widest setting, or retract them to reduce the amount of stability while still providing piece of mind to younger sailors. Come race day, simply remove a couple of clamps and you're class ready.
03-25-2011 11:06 AM
jcalvinmarks If you aren't already, you might start including a capsize drill at the very beginning of the class. Capsizing is pretty much an unavoidable part of dinghy sailing, so if the kids are so spooked by a capsize that they quit, perhaps disarming some of the trauma and stigma that goes with capsizing will help that.

As for the weighted daggerboard, when I owned a Daysailer, I heard of some pretty jerry-rigged contraptions to add some stability, so it's certainly on people's minds. Everything from casting the centerboard of lead to drilling a hole near the tip and lashing dumbell weights to it. There's a real limit to how much weight you're going to be able add to a relatively thin foil like that. I think a detachable bulb may be the best bet, as BH posited. Something like a beefy solid metal rod, ripped in half length-wise, with through-holes that match up with holes in the board. Simple as two bolts to attach it, and it comes nearly flush so it can still be beached; it just leans more to one side than previously.
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