Question about daggerboards

[bigfatguy]

Hello all:

I've read a couple of times now about the occasional need to limit the daggerboard or, in some cases, pull it up completely when sailing on a drop keeled boat. Could someone please explain to me when and why this is useful? I understand the whole "beaching" thing, but otherwise I'm confused as to why it's sometimes efficient to sail without a good grip on the open water.

Respectfully,

BigFatGuy

[sailingdog]

Umm... I think you're a bit confused, since a drop keel and a dagger board are very different things.

Daggerboards are generally only found on small sailing dinghies and multihulls. When you're sailing downwind, pulling up the dagger board, especially on a multihull, reduces the drag, and lets the boat go faster. Since you're going downwind, leeway isn't as much of an issue, as it would be if you were sailing to windward—so a good "grip" on the water isn't really necessary.

[Jay2]

I have a question which comes to mind. On a swing board if you run in to something does the board give and ride over the object? a dagger board would break, yes, no?

[sailingdog]

A swing keel or centerboard would usually kick up, a dagger board may break or more seriously it may damage the daggerboard trunk and cause a serious leak.

Originally Posted by Jay2

I have a question which comes to mind. On a swing board if you run in to something does the board give and ride over the object? a dagger board would break, yes, no?

[bobmcgov]

Another reason to partially raise a daggerboard or centerboard is to reduce heeling when pointing in strong winds. Reefing is preferred, but on some boats that isn't possible or takes too long. Reducing your underwater surface can prevent the boat from rounding up or capsizing -- at the cost of greater leeway. On centerboard boats (swinging foil), you can also trim the center of lateral resistance by raising or lowering the board. In strong winds, the center of effort moves back on the sails, inducing weather helm. Partly raising the board moves the 'pivot point' aft, inducing lee helm and re-balancing the sails.

One other factor: on planing hulls like dinghies, there can be a tendency on high-speed deep reaches or runs for the boat to 'trip' over its keel -- it will suddenly veer off to one side and roll. Sailboards and Sunfeesh are famous for this trick. Kickin up the board helps keep the pointy end forward.

Good question, tho.