Lifting boat for bottom painting

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Lifting boat for bottom painting

Postby talbot » Wed Mar 21, 2012 3:46 pm

Hauled my boat for bottom painting a couple of weeks ago. Thought people might want to see the rigging. The main hauling points are the bow eye and the transom drain hole, with secondary lines going to the chainplates. A completely independent static system (in case something breaks on the block & tackle while I'm under the boat) attaches to the bulkhead drain holes and stern cleats. The point was to get ready to sail by the end of March. Unfortunately, the next photo in my gallery is of the of the freshly painted boat sitting under a load of snow on the first day of spring.

Image
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Postby GreenLake » Wed Mar 21, 2012 11:07 pm

Those trees are handy.

Alternative suggestion for someone with your handy set of trees:

  • Use a 12' pole, or two rings with a 12' rope between them.
  • Attach the ends (or rings) to your lifting rigs.
  • Attach one block to each end or ring.
  • Run an "endless" loop through each block and underneath the boat.


Not only could you lift with that alternate setup, you could also turn the boat around the long axis. (For painting, you'd be able to work on a mostly flat surface, but you'd have to rest the boat on the gunwhales so you could take the lines off while you paint.

The pole (or rope) would make sure the diagonal pull from the trees gets converted to upward pull. The "endless" loop can have a knot in it, just needs to be positioned right to not get in the way during rotation.

Looks like you found a solution you are happy with - so this is just an alternative for anyone with equally handy trees.... :)
~ green ~ lake ~ ~
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Postby talbot » Thu Mar 22, 2012 2:25 pm

"Happy" is relative. I got the boat up to a comfortable working level that let me work on the bottom and fully-extended board with no lines in the way. On the other hand . . . .

I estimated that the boat at ~550 lbs w/o spars, or 275 lbs at each end, which would be liftable with my ~155lbs using two independent 3:1 pulley systems. The theory would work better if the boat weighed the same at each end. In fact, the stern lines carry much more weight. I can raise the bow hand over hand; I can't lift the stern with my full weight hanging on the line with a mountaineering ascender. I ended up bolting a spare trailer winch on the retaining wall below the boat and using that to raise the stern. Moving the bow harness aft (the obvious solution) would push the prow into the tree. Two years from now (next scheduled bottom paint), maybe I'll try a 4:1 on the stern.

I'm not clear on the pole / turning rig idea. Could you diagram it?
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Postby GreenLake » Fri Mar 23, 2012 1:17 am

Imagine you had two hooks in the sky, about 12' apart.

It would be easy to hang a block from each, run a en endless loop of rope through each block and have the DS suspended by the loops (like slings).

After you've lifted your DS, you can flip it over in the slings. As you flip the DS, the loops would run through the blocks. (That's why you use a block and endless loop, instead of fixed slings).

First, nobody has endless loops lying around. So you take whatever strong rope you have and make a knot. Then you need to position the knots so that they start at the blocks and move away from them as you start rotating the boat.

Second, nobody has actual "skyhooks". But if you took your setup with the trees, and the two lines, you could lift each end of a horizontal 12' pole. Even though the ropes pull a little towards the trees, the pole enforces a fixed distance of 12'.

That means, you can use each end of this pole as a form of "skyhook" and attack a sling to it to lift your boat.

A little further thinking and you realize that a pole is overkill, a bit of rope (12') would do, preferably with an eye or ring at either end for easy attachments of lifting ropes and the load (aka the blocks with their slings).

With me? Or do you still need a diagram. 8)

PS: I used 8:1 when lifting my DS from ceiling hooks... A 4:1 block and tackle plus a 2:1 cascade.
~ green ~ lake ~ ~
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Endless Line

Postby UCanoe_2 » Mon Mar 26, 2012 6:15 am

You could make an endless line that would run through the sheaves by long splicing 3 strand rope.

http://stoneycreeker.com/knots/images/fig_2-42.gif

I can't help with the sky hooks.
"George Washington as a boy was ignorant of the commonest accomplishments of youth. He could not even lie."
-- Mark Twain
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Postby talbot » Tue Mar 27, 2012 12:56 pm

OK, I got the rollover concept. I also have a caution about my lifting method. The last time I did it, I used a self-equalizing anchor on some big eyestraps that were throughbolted on the transom (they held my traveller blocks). I took those out this winter because the traveller tangled on the motor. This year I raised the stern using the transom drain hole. In final cleanup and waxing, I noted some new gel coat cracks. Next time I suspend the boat, I am going to distribute the load on the stern (the heavy end) across multiple points. Pulling the transom off the boat would introduce a whole new level of maintenance.

This would be another argument for the hang-and-roll technique of exposing the hull for painting.

You folks who dry-sail your boats from dinghy parks and launch with a crane -- where do you attach the crane hook to the boat?
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