Lifting Beams

[Paul H (admin)]

I'd like advice please on a lifting beam, to hoist MilliBee.

Typically off/on the road trailer and rolling her 90 degrees for hull maintenance. I'm the wrong side of 60 for kneeling on concrete, working under the hull with car jacks, blocks and levers muttering "never again".

I'm not sure of her exact weight, but lets aim for 250kg. So the specs are:

1) Typical load 250kg, worst case at the centre of the beam.
2) About 450mm to 500mm lift, for a few minutes.
3) Boat beam is 1.85m, so 2.5m to 3m (max) span between supports.
4) Beam will bolt flat to corner of house brickwork, supported other end by a folding A-frame. Beam will be removed when not in use, stored dry.
5) Two hoists: 1T chain block for slow precision lifts, electric hoist for speed and convenience.


I have various materials for a beam:

a) Aluminium scaffold pole, 5mm thickness. However it seems far too springy.
b) 3m CLS 70mm x 44mm, which I could glue+screw or bolt to be 140mm x 44mm x 3m
c) Sides of MilliBee's old bilge cases. 25mm x 140mm laminated ply, length 1.3m, epoxy + 2 pack paint, 3 available. Overlap butt joint.
d) Pine 140mm x 23mm length 1.93m, 4 available. Frame for a bunk bed bought in America, dense wood. Other lengths 0.83m for an overlap butt joint.
e) Two door frames from a 1920's council house. Strong softwood, coal clinker blocks or bricks notched into the frames. About 95mm x 40mm x 2.05m. The whole house was built like a tank, internal lintels are wooden!

The easy option is to glue and screw the CLS, next easiest is bilge case sides which I doubt have any other use.

A free online calculator estimates 12mm deflection, for 140mm Oak depth, more or less.

cheers
Paul

[The Q]

A quick look up and guesstimate gives a 4in X 4in  pine beam without knots supporting 1000LBS or 450KG, and you'll need at least that for safety.
online calculators say the Ali tube would bend 96 inches.. I think that's a failure..
I don't think you have anything suitable for the beam, I think you're going to have to pay for a 4X4 for the beam, and just at the moment prices are extortionate.
There is enough for the A frame, laminated up from the stuff you have.

[Paul H (admin)]

Q,

Thanks.

195x45 mm floor joists are £10/m at the local Jewsons.

Paul

[The Q]

Wood prices have gone silly at the moment, I was just reading of 8X4 plywood sheets in the USA are $95, they were $30 a couple of months back..

[inwe]

I use two gantries at a time , about 1 tonne capacity a pair , wooden with one cargo strop per. Never had any problem with capacity. Pictured below.



3x3 nominal posts with a 4x2 beam and of course the strops are located over the corner joint NOT off the beam. The beam is only there to keep the props apart. The beam is just bolted through cheeks that are screwed to the upright. The only load bearing is done thro the beam which is in compression. The strops are standard 2 1/2 ton strops ( the pink ones with 5 stitch lines). The feet as seen. One of these will lift Calluna, two provides stability.
Richard

[The Q]

Putting the strops on the corners is a good idea it puts all the timber in compression which is stronger..

I take it they are ratchet strops not plain ones.. (I'm looking at a small screen) How do you cope with the boat wanting to tilt as you tighten them up?

[inwe]

They are ratchet strops. a) the beam stops the uprights from coming together initially but then the distance between the two is adjusted so that they are not too far apart. When I turned Calluna the flat strops made it very easy to rotate the boat -  on my own! Still use them ( uhhh) to lift Winoote. Just lift in stages.

Richard

[The Q]

Blue Moon is effectively round bilged and hoisted on plain strops, and even before adding 180kG of keel she really didn't like being rotated while hanging there..