[alberg30] White Squall

[Chester & Jan Koop]

From: "Chester & Jan Koop" <cjk at tir.com>

>From my experience, you probably had a "heeling experience" of around 55
degrees.  Generally speaking, I don't believe wind alone will result in an
Alberg doing a 360 degree roll. However high winds and squalls could cause a
knock down of 75-90 degrees, particularly in a broach under spinnaker.  From
what I have read on heavy weather sailing roll-overs are generally result
from a combination of high winds and big waves.  Yves Gelinas, who
single-handed an A 30 around the world in 1985-1986 experienced one knock
down of 90 degrees+ and one of 360 degrees, both in the South Pacific
(Roaring 40s).  The roll-over resulted in being dismasted, however the boat
(and Yves) survived.

As a result of the 1978 Fastnet Race, where a significant number of boats
capsized/sank  and 13 or so lives were lost, considerable research was
directed at deterring what design factors impacted a yacht's ability to
recover from sever knock downs and roll overs.  Out of this research came a
number of findings including a formula/calculation for determining a boat's
"inverse stability co-efficient."  While I can't remember the formula or all
the factors impacting the calculation (beam/length ratio, cockpit volume,
displacement/length ratio, etc.), boats with a co-efficient of 2 or less had
the ability to avoid achieving inverse stability and safely recover from a
roll over.  The rule of thumb is boats with a co-efficient of 2 or less
should be consider, all other factors being equal, blue water capable.
Albergs 30 have an inverse stability co-efficient of around 1.9

As the co-efficient rose above 2, it became more likely that the boat would
achieve "inverse stability" (i.e. the ability to remain up-side down ).
Generally narrow beamed boats had lower co-efficients than broad beamed
boats, with catamarans and trimarans having the highest.  I would suspect
that all these new cutting edge "aircraft carrier" type race boats (i.e. BOC
boats etc.) have a very high co-efficient.

If you want more info on this subject, read Fastnet Force 10.

Chet Koop
Tangaroa  #445


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