In order to ease the construction of my 18' pocket cruiser, I built a pair gantry cranes. I dismantled them at the job's conclusion, so I built models to illustrate them here. While the size and materials may be adjusted to the builder’s needs, my full-sized gantries had 12' 2×8 horizontal beams, 10' 2×6 vertical supports, 8-1/2' 2×4 angled upright braces, 18" 2×6 top spacer blocks, 8" 2×6 top beam supports, and 4' 2×6 bases. The handles for winding the winches are inserted here. This exploded detail shows the arrangement of the corners of the frame. Omitted for clarity is the diagonal brace running from the ends of the beam down 4’ or 5’ to the vertical support to prevent side sway.
Photographs and models by the author
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What weight and beam of boat did you lift?
Locally at the Apprenticeshop, Dale Young rigged tall boat stands to do this. A beam goes across them after the pads are removed. Sling is rigged, then the screw on the boat stands cranked up, one person on each side.
You said you used 5″ webbing – do you think 4″ would work or if not what about doubling the webbing? I have four trailer winches and do you think they will work? How much weight would you guess that one crane with chain fall would work to lift out V-8 engine from boat?
John
Question- what about relocating winches down lower so you wouldn’t have to use ladders . You could use steel shaft with roller at corner to allow webbing to go down to the lowered winches. Standing on ladders is not my idea of safety especially when you are talking about four ladders. The longer webbing with rollers would help ease weight distribution. Would suggest boat trailer rollers?
An eloquent description enhanced by excellent illustrations and a model which is a work of art. I was captivated by the ingenuity of the use of the webbing winches and the construction of the the gantries.
Thank you,
Rob
I have something similar done from 4 logs 16x5cm and one 16x8cm for the top. As diagonal stringers I use tensioned rope, it is not good for long term hanging, but for turning boat it was ok. There are also groves in the top log for the legs, this stabilize the crane a lot.
I wanted to create something that can be easily assembled and disassembled (and stored for later use).
It is used for my 600kg Jollenkreuzer. The size of the construction is around 3x3m. The greatest issue while turning the boat was that it is around 2m wide and there were not much space left, but it passed.
Great to see a practical way of safely handling your boat. An essential item with the Flying Fifteen weighing in about the 500 kg (1000 lbs) mark. When maintenance requires close attention to the fixed keel right the way around, many hours of 6000 wet-and-dry sanding to get a very slippery keel. A gantry is essential.
I question the use of ladders. A few turning blocks can lead belts safely to the ground. Secondly, if “rated” belts and slings are used, you may be surprised how small the belting is that you actually need. Always use tested and rated belts and slings. Use of modern cordage is also recommended as the Spectra range of cordage is rated well within the loads of boats up to 20′ or 6m, this gives scope for the use of a wide range of winches that may be secured to the sling.
Please keep your feet on the ground and never work under or on the vessel unless it is well and safely supported by heavy timber, which is usually at hand and is relatively inexpensive—often available as off cuts from your local timber supplier.
Lastly, crawling around under a boat is not wise. Having access to a safe hoist makes maintenance, and building for that matter, much safer and easier. Ask anyone with a fixed-keel boat that they trailer from home!
Very nice! I did something similar using two chain hoists and webbing with spreaders to lift my boat off the build frame and slip the trailer under. This made adjusting the trailer to suit the boat really easy.
You mention “truck winches+ as an alternative. Do those differ from common boat trailer winches with a webbed strap from the winch drum to the boat?
The winches noted in the article are truck tie-down winches. Here’s an example. Unlike a trailer winch, this type doesn’t have a hand crank.
Editor
But what’s the load rating?
Earl,
Thank you to responding to the requests for an article on gantry cranes.
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