Looking for something different

Discussion in 'Sailboats' started by SailorAlan, Jun 12, 2017.

  1. sharpii2
    Joined: May 2004
    Posts: 1,986
    Likes: 151, Points: 63, Legacy Rep: 611
    Location: Michigan, USA

    sharpii2 Senior Member

    I agree with your reluctance to save weight with the steering system. I knew of a Pearson 26 which hit a huge rock with its spade rudder. The solid metal rudder shaft bent back about 15 degrees but the boat was still steerable.

    I believe cruising boats are inherently different from racing ones, in that even performance cruisers need to be durable even when such durability compromises performance.

    I have designed a number of scows, intended to sail in brown, stump infested waters, and so came up with two simple kick up rudder systems. The first has a typical two piece rudder, with a blade that can pivot fore and aft (see attachment)


    It has a long shock cord which connects to the leading edge of the blade. The other end connects to the bottom of the boat. If the blade hits a stump, it pivots back far enough to ride over the obstacle. The shock cord then pulls it back down, once the obstacle is passed. The twin side boards (which are not true lee boards because they can only pivot fore and aft) have a similar system.

    On another design, I wanted a rudder which could swing entirely clear of the water. The two piece rudder was not going to work with this requirement, so I had to come up with something else. And simply unshipping the rudder was not going to work either, because this boat had an aft deck and a narrow Beam. It would probably capsize if I tried to sprawl across this aft deck to pull the rudder out, or put it back in.

    So I came up with a false transom, which has a hinge on its top edge (see attachment).

    Boxcar 12ea.png

    The same shock cord arrangement is used as was on the two piece rudder system, but the shock cord must be longer. As with the two piece system, the shock cord length must be twice as long as its maximum stretch, with the rudder pivoted as far as its going to go.

    The false transom idea might be applicable to your requirements, if the mechanism holding it down is a breakable line, rather than a shock cord.

    Attached Files:

  2. SailorAlan
    Joined: Jun 2017
    Posts: 13
    Likes: 2, Points: 3
    Location: Panama City, Panama

    SailorAlan Junior Member

    I could go for a variation of either rudder setup.
    With the fuse idea for the false transom, I would want some way to easily and quickly reset it.

    The risk of hitting something hard or heavy at speed is something i want to really keep in mind with this boat. I kind of think equal weight should be given to speed and safety. Then comfort, ease of handling, sutainability and simplicity and lastly cost.
  3. jorgepease
    Joined: Feb 2012
    Posts: 1,614
    Likes: 48, Points: 48, Legacy Rep: 75
    Location: Florida

    jorgepease Senior Member

    SailorAlan likes this.

  4. sharpii2
    Joined: May 2004
    Posts: 1,986
    Likes: 151, Points: 63, Legacy Rep: 611
    Location: Michigan, USA

    sharpii2 Senior Member

    Fuses cannot be reset. They are sacrificial by nature. But it may be possible to design a sister fuse which can be screwed in after the other one blows.

    This would be a second sacrificial line which would not be cleated. It would have to have a long tail, so that when the false transom kicked up, there would be some of it to grab to pull the transom back down. This would all likely happen in somewhat wild conditions, so replacing the original line would probably have to wait. The routing of both lines would have to be aft across the deck, over the false transom, then to fitting on the real one. Each line would need its own fitting, so now there would be two lines running aft on the aft deck. Each line would require two rollers mounted on the false transom, one on the top and one near the bottom. These would be intended to reduce friction, so most of the line tension goes toward holding the false transom down. The second line had better have access to a winch, as this system would the mechanical disadvantage of a third class lever.
    SailorAlan likes this.
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.