Saturday, 8 March 2014

Hull Turning

I've had a few requests for further explanation on how I turned the hull, while the lead keel was attached.  I had some reservations about doing this - wondering if the hull itself was strong enough to carry the keel upside down - but an email to the designer, John Brooks elicited a swift reply to say that it would be fine.  I had seen where Dave Johnson in his building blog of the SS 12.5 also had taken this approach and Dave also confirmed to me that it was quite straightforward.   So, armed with these encouragements, I decided to take this approach.

To recap, I installed an I-beam spanning wall to wall running perpendicular to the hull.  This carries a rolling beam trolley
onto which I attached a relatively light 1-tonne block and tackle.  This allowed me to lift the lead keel onto the hull by simply letting the chain loop through the centreboard slot in the lead around a short length of flat steel underneath and attaching the eye to itself above the lead keel.  Once, I found the balancing point, the keel was docile and easy to manoeuvre.  I simply lifted it off a small trolley on the ground beside the hull and used the beam trolley to position in directly over the keel on the hull.
 This trolley proved very useful at various stages for manoeuvering the keel, and I am hopeful that I can use it also to wheel the finished boat out from the the garage.

Here you can see the keel being lifted onto the hull, with keel bolts ready, prior to epoxying the keel.  Before setting the keel onto the hull, I placed additional timbers from beam to beam to support the extra weight on the hull.  Once in place, extracting the flat steel plate from underneath the lead keel, I used a garden root cutter to pry the lead off the hull, while spreading the load across the cutting blade. A flat wide spade would probably work just as well.  You need to have some system figured out in order to remove the flat steel, as the weight of the lead will cause damage to the keel, if you try to pry the lead up with a narrow tool.

Next step having secured the keel and faired it into the deadwood, paint the hull etc., was to create a set of slings to support the hull while turning it over.  I used ratchet straps for the slings.

It's quite important to have the fixing points for the slings far enough apart so that when you turn the hull on its side, the narrower profile on its side doesn't allow the hull touch the ground. I have a small loft over the workshop, so I just drilled holes in the loft floor, positioned lengths of timber perpendicular to the joists over the loft floor to run the straps around and back through the holes.  When I first turned the hull around (before the lead was installed), we had quite a hard time, as we had made slings from ropes which were positioned over the hull approx 6ft apart (same size as the beam).  This proved troublesome as the hull dropped too low when on its side.  We were able to manhandle our way out of trouble, but that would not be an option when the lead is installed.  By comparison, I reckon the anchor points for the slings when we made our most successful turn was about 14ft apart, from an 8ft height.  (yes it's a small tight workspace!) On a different occasion we had the slings even wider apart and this also proved difficult as the hull was not inclined to swivel as easily.

Here you can see the hoist having been threaded through the centreboard slot.  To protect the top of the trunk we took a 4ft length of 2x6 stock and drilled a 30mm hole through it.  The chain loop was put through the hole and a length of steel bar placed through the chain loop which then was pulled tight against the 2x6, which in turn rested against the top of the trunk.  The hoist eye was too wide to pass down through the centreboard slot, that's why you can see it looped back onto the chain outside the lead keel.

My friends Brian and Brendan were on hand to help with the turnover - as it transpired they ended up having to complete it themselves, as I rushed off to a forgotten appointment!  No drama, apparently the hull rotated in its slings, while the trolley for the hoist was moved across the I-Beam and locked in place to one side with ViceGrips.  This allowed them to use the hoist to pull the hull around in its slings, and when it reached about 50deg they propped up the lead keel and released the hoist.  Then they reattached the hoist through the centreboard slot from the opposite side, with the following result.

So the secret to stress free hull turning is to bring your friends along, set up the operation and then make some flimsy excuse about having to go to an important appointment!  Come back 2 hours later to find the hull right side up and sitting it its slings!

I should say that the hull seemed completely rigid throughout the operation.  No sign of any damage or scuff marks to the sheerstrakes.  That said, the hull had both its bulkheads fitted as well as the seat lockers, which provide additional torsional strength to the hull.  Similarly, Dave Johnson turned his hull before any interior fit-out without any damage.  Dave told me he had slight scuff marks from the nylon straps.  He used eye bolts in the lead keel, because apparently they were already installed in the keel for lifting it, but he concurred with my approach to thread the chain through the slot.

Once the hull was rights side up, I was able to balance the hull on the chain hoist, remove the straps and push the hull around so that it sat correctly and evenly on my stands - using the design JohnB prescribes in his plans.    When it comes to the time to take the boat out of the workshop, I will deploy the same approach with the hoist and remove the boats stand and replace with my trolley.


  1. Innovative bit of engineering and well described.
    I have filed it away for future reference . . . in a few years.
    Pete. DownUnder.

  2. You have done great job.
    Thanks a lot for sharing your wonderful experience.