Understanding Lifting Keel on the Hard or Trailer

Discussion in 'Boat Design' started by CloudDiver, Aug 7, 2014.

  1. CloudDiver
    Joined: Jun 2014
    Posts: 148
    Likes: 7, Points: 18, Legacy Rep: 40
    Location: San Diego

    CloudDiver Senior Member

    I'm wondering how lifting keel boats sit on blocks or on a trailer. As I understand it on fixed keel boats most of the wieght rests on the keel while the boat stands provide 4 to 6 points of stability, not really supporting actual wieght. So how does this work for a lifting keel design? I mean, with the keel retracted you can still set the hull down on blocks or in the trailer, but is it pushing the bulb up against the deadwood to support the hull wieght? Does this have the potential to mess up your bottom coating/finish?

    To illustrate here is a video of a Nordship 430 on a trailer, operating the lift mechanism. Now, you can see the lifting strap still around the hull and the crane in the background so I think we can assume the crane is supporting the hull vice the stands on the trailer.


    I think this is a hydraulic mechanism on this design, so it pushes down on the fin keel as well as pulls it up. So when the bulb is down on the trailer blocks and the crane lets go, then what? Are the stands supporting more wieght or no? Is the wieght is supported by the keel still because the hyraulic system keeps it locked down, disrtibuting the load like any fixed keel? So what would be the case if it were a smaller boat with a manual hoist for the keel and a locking pin? I'm guessing the hull design and thickness come into play, placing the stand pads over frames, using longitudinal bunks on the trailer vice pads, or an athwartships cradle like on the Ultimate 20.
  2. PAR
    Joined: Nov 2003
    Posts: 19,133
    Likes: 494, Points: 93, Legacy Rep: 3967
    Location: Eustis, FL

    PAR Yacht Designer/Builder

    Typically, you support the boat on the centerline, with stands used just to keep it from flopping over, regardless of appendage type.
  3. jehardiman
    Joined: Aug 2004
    Posts: 3,517
    Likes: 903, Points: 113, Legacy Rep: 2040
    Location: Port Orchard, Washington, USA

    jehardiman Senior Member

    I concur.

    I have always seen keels wedged up to take "some" load when the boat is shored up or on the trailer beds ( a Mull Ranger 26 I owned or my brother's Wiley Wabbit trailer sailer). For lifting or swing keels, I have always stored the boats with the keel resting on a support. Right now, the Catalina 22 sitting in the driveway has the keel resting on the trailer support. Prior to launching, I crank it up housed to lessen the float-off draft.

  4. PAR
    Joined: Nov 2003
    Posts: 19,133
    Likes: 494, Points: 93, Legacy Rep: 3967
    Location: Eustis, FL

    PAR Yacht Designer/Builder

    I have ballasted board on my 23, not a lifting keel, but still heavy. Currently it's in the yard, getting a new paint job. When I pulled it off the trailer, I blocked the centerline, leaving the slot clear, then let the board down a bit, so it too could rest on some blocking. My thought is to relieve the hoisting tackle the 500 pound load. Just under the turn of the bilge are the stands and they have hardly any weight on them. I can rock the boat on the centerline blocking with my shoulder easily.
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.