Bilge boards

[Sayla]

I don't seem to have found much information or discussion on bilge board use - the +ve & -ve's, and are they used together / individually ? efficiency etc - I know that Iain Oughtred designs them in so I'm figuring that there's probably some experienced bilge board users here.
Thanks for reading / any comments

[DGentry]

There have been a few threads . . . .
Bilge boards are found on many of the racing scows common to the US. {Google A scow, MC scow, etc}They are used individually, and work just dandy - even though many of them are basically just flat plates of aluminum.

These are retractable, like centerboards. Bilge keels are a whole different animal.
Bilgeboards as used on the current crop of open class ocean racers are also retractable, but as daggerboards. They are asymmetrical, and often toed in a bit for highest efficiency when going to weather.

If your boat is not best when sailed mostly flat, then bilgeboards are a great option, IMO - likely more efficient than anything other than lifting hydrofoil systems. And they leave the interior of the boat less cluttered than a center or dagger board. But, there's twice as much stuff to make or buy, it's twice as heavy, and there's twice as much to go wrong.

[Sayla]

Thanks,
I googled some more an seem to find more +ve than -ve according to those who employ them - it would appear that one could even improve performance while decluttering the cabin - I read that the weatherside board is lowered just before tacking and having the two boards helps to reduce stalling in general, and then the opposite board is raised once on the tack.

Users state - easier maintenance access - less chance of fouling with seaweed and gravel etc. It would also appear that rather than the two boards being an inconvienience of build, it actually provides a backup spare underwater plane if one is out of action, even though they are asymetrically performing.

[Steve Paskey]

It would also appear that rather than the two boards being an inconvienience of build, it actually provides a backup spare underwater plane if one is out of action, even though they are asymetrically performing.

Phil Bolger used a single "off-center centerboard" on some of his designs (including Birdwatcher) and even off-center masts. He found that the asymmetry had little or no effect on performance, so long as the off-center board had enough area below the surface when the boat heeled.