Mobile cradle help

[Guest]

I've recently bought a Colvic Watson 26' motor sailer, weighing I believe around 5 tonnes deadweight.
My club allows winter storage on the club's site and this will save loadsamoney over parking on the hard at the Marina next door. The Club has a tractor and a concrete slip to pull the boats up from a high-tide float onto the cradle.
So, I need to get a wheeled, steerable cradle made, capable of safely carrying the boat's weight and being stable.
I've looked at the 2 or 3 adverts for boat "legs" but there appears to be nothing such as I describe.
I've also looked around and photographed a variety of strange welded steel things with what appear to be lorry or large van axles/wheels grafted on, in all sorts of strange ways - but they seem to do the trick.
Can anybody suggest how to go about getting the wheels and steerable axles, checking their safe loading capacity, and is there anywhere to look with ideas for designing such a cradle??
I can get the steelwork done OK..... I've even made a few steel things in my time, but the design of this, to take this sort of weight and be safe and stable is a concern. Also, I dont really want to spend a fortune getting Harland & Wolff to design & build it.
Any suggestions are welcomed or perhaps where else to look for ideas ?? Any body suggest things to do / not do in such a cradle ??
If you can help, thanks.
MalcDavis, Kent.

 

[Avocet]

A typical Transit van can weigh up to 3.5 tonnes fully loaded so a pair of transit axles would barely be enough (given that it won't be going very quick). You might be better off with something off a 7.5 tonner (a Ford "Cargo" or Leyland "Roadrunner" but these will be pretty difficult and big things to handle!

Good luck!

 

[MedMan]

The marina where I over-wintered in Croatia last year had 200+ boats on the hard, most in cradles which were trundled to and from the travel-hoist bay. Before the boats were lowered into them, the cradles were lifted onto four 'dollies' (my word - not theirs!), one for each corner. Each dolly comprised a plate of, I would guess, 8mm steel about 500 mm long and the width of the main beams of the cradle (around 100mm square section) with short side plates going upwards to keep them in position. Two cheeks were welded on the lower side of each plate through which ran short axles on which turned steel wheels of arond 200mm diam. I would guess the axles were around 20mm diam. When the boats arrived at their allotted spot on the hard each corner was jacked up in turn using a hydraulic jack, the dolly was removed and the cradle lowered onto a wooden or concrete block. It was all somewhat agricultural but it was strong and it worked - boats of up to 10/11 metres were handled in this way.

You would not need removeable wheels, but this experience shows that you certainly do not to involve Harland & Wolff.

Good luck,

David.

P.S. All the measurements I have given are approximate and from memory - I have not put a measure to any of it - so don't take them for gospel!

 

[yoda]

I have seen apermenant arrangement of what Medman has described work very well for a Sigma 36. Esentially small diameter solid steel wheels on each corner of a solid steel frame. Have seen on advertised, I think on the Cruising Association Web site for sale section but have lost web address.

Yoda

 

[dickh]

I have also seen trolleys as medman describes, but with 2 fixed wheels and 2 swivelling wheels so they can be roughly steered. Large(12" dia) castor wheels with either rubber/plastic treads or cast iron. Some have a triangulated towing bar. Work well if you don't have to go over rough ground. Have often seen them advertised second hand, but are often not easily transportable if all welded construction.
Also try Ex-MOD trolleys, our boatyard has one with v heavy inflateable tyres and proper (low speed) steering and towbar - but would need suitable support arms fitted.
Most seem to be home made to suit a particular boat, try talking to a local small engineering works or trailer manufacturers to see if they can supply something. As you say, all you need it for is a short distance tow and to take the weight, plain bearings are OK as is solid rubber tyres. If you work on 1½ tonnes per wheel you won/t go far wrong. If jacked up off the ground when positioned the wheels/tyres should last a long time.


dickh
I'd rather be sailing...

 

[chippie]

I agree with the previous posts re solid wheels sometimes with solid rubber tyres. The drawback of using van or truck axles is that the centre of gravity of the cradle is much higher, although this may work in pracice.
There are some local cradles near where I go boating that have solid wheels about 12'' in diameter with a steering yoke arrangement much like a child's trolley that has the drawbar fixed to that.

 

[oldsaltoz]

G’day Maldavis.
Welcome to the forum. We built a cradle for a 28 footer some years ago; we used truck parts for the axles and wheels, railway line for the main base frame and RSJ for the support frames. A fully welded construction; we had a fixed ‘H’ frame at the front with a timber cut to fit the hull form on the crossbeam.
This allowed us to drive the boat into the frame and secure the front end. At the back we had 2 arms on pins supported by short but heavy chains that crossed over under the boat; these were pulled up after the keel had passed onto the cradle and a webbing was secured to the top of each frame and passed under the boat. This was replaced by a steel crossbeam after the boat was clear of the water.
Steering was a simple set of arms from the draw bar to the front wheel steering arms, adjusted with a bottle screw. The outside or the wheels was about 2 feet past the widest point of the boat. When located we jacked the wheels off the ground and let down 4 short legs and locked them with pins. We later added ladder steps to the “H” frame for easy access. Worked a treat and was still in use when I last saw it about 6 years later.
Don’t use box section as you cant paint / protect the inside and it will rust. 95% of the material will be available at your local scrap yard. Give it a good paint job before it gets wet and put a grease nipple on each moving part and wheel bearing, pack them just prior to use and again when finished. You don’t need an engineer to design the thing if you over engineer the whole thing, this will also mean more steel to rust away before any failure.

Avagoodweekend Old Salt Oz……

 

[WayneS]

What club are you at. Sounds a v-similar setup to where i am.