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

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

  1. marshmat
    Joined: Apr 2005
    Posts: 4,127
    Likes: 149, Points: 63, Legacy Rep: 2043
    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.
Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Your circumstances or experience may be different.