Cruiser vs racer multis, a discussion of righting/heeling moment

Discussion in 'Multihulls' started by marshmat, Mar 6, 2010.

  1. marshmat
    Joined: Apr 2005
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    Location: Ontario

    marshmat Senior Member

    After the last few threads on proas and small cats, I've been thinking about what seems to have become a pretty well-defined barrier between racing and cruising multis. Namely, that the racing variety are usually seen flying a hull (or nearly so), while the cruising variety tend to keep both (or 2 of 3) hulls firmly planted in the water.

    Flying a hull is a function of righting moment versus heeling moment; RM peaking at the point where the windward (or central) hull begins to fly. Racing cats and tris obviously operate at around a 1:1 ratio of RM:HM when they're pushing hard. But what about cruisers?

    Few cruisers seem to be comfortable flying a hull, for obvious reasons. Some cruising cats and tris appear to be unable to do so, even in strong winds.

    I think it would be interesting to hear some perspectives on:

    - RM to HM ratios for cruisers; by how much should peak RM exceed peak HM, and how much of a stability margin should a cruiser have (compared to a racer) in any given set of wind conditons?

    - The middle ground between "cruiser" cats/tris/proas (the Caribbean/Med charter fleet comes to mind) and "racer" cats/tris/proas, specifically, what ranges of the usual performance ratios tend to work well, and what results in a pig? I know we have at least a handful of designers around who are working in this middle ground of relatively well proportioned, well-performing cruising boats.
     
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