Why Aren't Bilge Keels More Popular ?

In England and NW Europe the bilge keel boats are probably a majority.

 

Bilge keels are hard to make strong enough without adding a lot of weight. Also all the conceptions of going aground visualize a nice flat tidal beach but what about other situations like rocky ground or uneven sand bars? On yer ear mate. For some boats and some uses they make sense but not for most, thus the specialized and limited use.

 

They also confer a non insignificant amount of resistance to roll and help move the CG downwards, which was my primary interest. The ability to ground upright, ow as protection of keel coolers, is secondary.

 

The one thing that would keep me away from bilge keels (especially on a power boat) is that it significantly reduces or eliminates the ability of the craft to slide sideways on a beam sea. I once designed a 28' plywood OB that slid sideways down the face of breaking seas very well and this feature (not anticipated or designed for) probably saved my life in seas at least as big as 2 story houses. Boats that don't slide sideways make me nervous. No I don't like bilge keels. Boats w flat bottoms and flat vertical sides can "trip" on their chines and boats w bilge keels can trip and capsize as well.

 

A lot of fishing vessels and displacement power boats here in B.C. have bilge keels or rolling chocks, as they are often referred to. Some of these rolling chocks are of significant area. I had an older wooden 45 foot power boat with a full length keel timber and bilge keels to dampen the rolling, making the ride noticeably more easy. As a recreational boater, I avoided going out in seas large enough to cause me concern or discomfort.
I can understand Mr. Easy Riders point but different hulls need different considerations. His hull, and my current boat will slide sideways, giving away as it were to a side blow from the sea. It works. The flip side is the damn thing also slips sideways when manoeuvring with a cross wind in the marina.
My old 45 foot, 20 ton power boat, despite considerable wind-age tracked true, even at very slow speeds, and the rolling was moderated to an acceptable level without actually reducing stability.
As far as sailing vessels are concerned, I have little experience with twin or bilge keels. I know the conventional wisdom they are slow to windward and perhaps slow off the wind as well. It might be worth looking at an article published by Bray Yacht design suggesting that properly designed they can perform as well, or possibly better than a comparable traditional single keel yacht.
There are the additional advantages mentioned by cthippo above.
I would certainly consider twin or bilge keels for a cruising boat, which is after all what I am most interested in anyway.

 

"The flip side is the damn thing also slips sideways when maneuvering with a cross wind in the marina." Would seem to be a given but my boat would only slide sideways at extreme angles of heel. When not heavily heeled on the face of a wave my boat was EXTREMELY resistant to side slipping. It was a very unusual hull form. In cross-section picture a "W" with the lines at 45 degrees and a third "v" at the bottom a bit lower than the other two.