Cutaway forefoot

[Barquito]

I have been looking over John Vigor's 20 Small Boats book, and have a question about a statement he makes in a number of places. He states that boats with a cutaway forefoot will not be as likely to broach going down steep waves as a full keeler. Is this just a matter of quicker steering vs. full keel, or are there other dynamics involved?

[sailingdog]

The cutaway forefoot will help reduce the chance of the keel catching as the boat moves down the wave and forcing the bow around, causing the boat to broach... a full forefoot would be far more likely to resist the water and force the bow around.

[CharlieCobra]

Where's Jeff? I figured he'd jump on this thread as it's right up his alley.

[Barquito]

Possibly why rockets have fins at the bottom, not the top. OK, maybe a rocket isn't a good comparison.
I think I can picture this now, with the boat skidding down the wave a little bit beam-to, the center of lateral resistance would be further back with less keel upfront.

[CalebD]

Your 'rocket' analogy works pretty well for me. The hull on my T27 has a cutaway forefoot and we even race it. Because of the hull shape it will track well on nearly any course but is more difficult to turn than nearly any fin keel boat. We also have a hard time matching the fin keel boats angles into the wind.
Are there even any 'full keel' recreational boats available other than some of the old schooners etc?
Patrick O'Brian describes the broaching of a full keeled Dutch warship in the angry southern ocean with great effect. Of course this is fiction based upon historical research ...

[sander06]

I would suggest that putting out a sea anchor might be a more appropriate response to surfing down the face of a wave than discussing the merits of a cutaway forefoot keel. Besides, exactly how many of you all have surfed down the face of a wave with your boat? Tis the subject that legends are made!

IMHO

[Jeff_H]

Broaching is one of the downsides of a boat with a deep forefoot, or truly full keel. Basically a wave swings the stern off course and the forefoot is now turned across the direction of travel causes the boat to turn further. It used to be called rooting when I was a kid.

Cutting away the forefoot helps with rooting somewhat but it isn't a cure all. Typically early boats with cut away forefoots and came with keel hung rudders and short waterlines making for boat that were especially prone to broaching but for other reasons not related to the forefoot perse. Fin keels with skeg hung spade rudders were introduced to help tame this tendancy to broach. Unfortunately about the time that fin keels and spade rudders were became popular during the IOR era, then rigs and hull forms began to be distorted in manners that promoted broaching. Today we have boats with comparatively fine entries and narrow waterline beams and while the are easy to steer and will dynamically balance and track, occasionally the fine bow will catch a wave and root a bit.

As to the perhaps rethorical question, "exactly how many of you all have surfed down the face of a wave with your boat?" The tendancy to broach can occur in comparatively small wave trains (my sense is perhaps as little as a wave height as small as half the boat's beam and as close as 1 1/2 boat lengths). Obviously we are not talking about a full blown wipe out type broach, but more the type of broach that requires adjustment with each wave which of course is tiring and uses more power when on autopilot.

Jeff