J 34 we extended rudder

Discussion in 'Boat Design' started by J 29 Guy, May 22, 2020 at 11:16 PM.

  1. J 29 Guy
    Joined: Feb 2012
    Posts: 14
    Likes: 0, Points: 1, Legacy Rep: 10
    Location: United States

    J 29 Guy Junior Member

    We have a old IOR boat at our club a J 34 and it got noticed it has a deeper rudder then OEM. It has been measured and 7 inches has been added to it. What kind of performance gain could be gained from a deeper rudder? I understand why they did it ,these old IOR boats could get wobbly going down wind. I would have to think it there would be a performance gain on all points of sail for this boat but what kind of gains?

    J 29 Guy
     
  2. Ilan Voyager
    Joined: May 2004
    Posts: 1,229
    Likes: 149, Points: 63, Legacy Rep: 758
    Location: Cancun Mexico

    Ilan Voyager Senior Member

    The main and lone purpose of this rather common modification on old IOR is yaw stability downwind while being with a spi. Most of the SORC and IOR boats were notoriously unstable while sailing with the round balloon spis and just one spinnaker pole. I remember very thrilling times when the boat suddenly made a half turn towards the wind, the mast almost in the water and the spi dragging in green water like a fishing net while being in the middle of the herd during a regatta. You could hear a lot of screams.
    Before deepening the rudder you have to check if the shaft would be strong enough. There are surprises on very light built boats...
    You won't gain a lot directly on speed, as the IOR boats, because of the philosophy of the jauge, have never been very fast (the joke in the seventies clubs: the purpose of the IOR jauge is to make to make win a boat a bit less slow than the opponents by adding well placed bumps at the points of measure), but surely in handling and safety thus a bit in mean speed as I said already the IOR were not brilliants in yaw stability downwind.
    The rudder deepening maybe changes the rating of the boat, that depends on what rule you are racing now. The jauge has to be recalculated.
     
  3. J 29 Guy
    Joined: Feb 2012
    Posts: 14
    Likes: 0, Points: 1, Legacy Rep: 10
    Location: United States

    J 29 Guy Junior Member

    We race under PHRF, I wonder what perforce gains would be accomplished? I understand why it was done on days where we round up going down wind on our J 29 they seem to just keep going with out any issues.
     
Loading...
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.