Daggerboard size

[CaptainAhab]

I've been coaching a squad of Laser 4.7 boys this past year. We've had a windy winter here in South AU. Watching these guys working their asses off upwind while doing all the right things(vang sheeting, properly adjusting the rig, etc). It got me thinking that the entire boat is out of balance. The daggerboard was designed for the full rig(7m2). It was actually oversized slightly, so the boat would point well in light winds. If you drop the sail plan 33%, then the daggerboard/centerboard size should drop as well. I believe that as soon as you get excessive heel/weather helm in a 4.7 you should lift the board a minimum of 1". Depending on conditions and size of sailor it could be 2". It allows the sailor to keep the rig & foils vertical which increases lift, Also by going a bit faster you will generate more lift. Between the two it will easily make up for a little less board(which is the wrong size based on very basic yacht design). Anybody out there lifting 4.7 daggerboards to increase performance?

 

[Zhankz]

I've been coaching a squad of Laser 4.7 boys this past year. We've had a windy winter here in South AU. Watching these guys working their asses off upwind while doing all the right things(vang sheeting, properly adjusting the rig, etc). It got me thinking that the entire boat is out of balance. The daggerboard was designed for the full rig(7m2). It was actually oversized slightly, so the boat would point well in light winds. If you drop the sail plan 33%, then the daggerboard/centerboard size should drop as well. I believe that as soon as you get excessive heel/weather helm in a 4.7 you should lift the board a minimum of 1". Depending on conditions and size of sailor it could be 2". It allows the sailor to keep the rig & foils vertical which increases lift, Also by going a bit faster you will generate more lift. Between the two it will easily make up for a little less board(which is the wrong size based on very basic yacht design). Anybody out there lifting 4.7 daggerboards to increase performance?

There was another thread similar to this (I can't remember if on here or Sailing Anarchy) where they did the math and found it actually reduced performance IIRC. I will try to find the thread.

 

[Zhankz]

Lo and behold, it was you!

Laser daggerboard

The Laser daggerboard was designed for the size/righting moment of the full rig. Ian Bruce stated in one of his C2 YouTube videos that Bruce Kirby designed the Laser to go upwind well in 10kts. Ian Bruce said that at hull speed you can raise the board an inch with no side slip(paraphrased). It’s...

forums.sailinganarchy.com

I haven't read this analysis of Laser performance properly yet and I can't find a definition of the terms used in the hull drag chart, but it seems to indicate that centreboard and rudder induced drag is 20% of the total hull drag in a big rig. If you lift the board that would increase the total hydro drag by over a quarter.

So from what I gathered in this thread is that in a 4.7 rig if you bring the board up it reduces performance?
That doesn't make total sense to me so I'm going to stick with your logic on this one.

 

[Gummore]

That's some interesting insight! Adjusting the daggerboard size for the Laser 4.7 makes sense given the smaller sail area. Lifting it to optimize performance sounds like a smart move, especially in windy conditions. Have you tried it out yet?