Trick Cradles

[aitchem]

Hi,
Anybody seen any trick yacht cradle designs.?
I was going to buy an off the shelf one, but, having deep pockets and long arms, it's difficult.
I'm just looking for better ideas/suggestions/pictures of a fully adjustable/dismantleable/lightweight cradle fabrication a home welder can manage.

thx
H

[Shife]

A friend of mine had this cradle built for the DB1 he owns. Sorry I don't have a better pic. It can be unbolted and transported in the back of a pickup. A good friend of ours who used to own a sheetmetal shop built it.

[D'ARTOIS]

Very easy to make one. Shall drop tomorrow a drawing.

[aitchem]

Thanks,

That's more like it, very tidy.
If the steel is in compression, you don't need the 50mm scaffolding pipes most cradles are made from.

H

[nero]

I used beam support jacks from the local hardware store. $28 each. they were 3 inch diameter pipe with a screwjack in one end.

[Andy]

There is a retired engineer who sails at the Royal Forth Yacht Club on the Firth of Forth in Scotland who has developed a cradle far superior to anything above or indeed that i have seen anywhere else. It is dismountable, and most usefully, can be levelled with the boat ON the cradle. In a crane-out a couple of years ago I watched while many owners of other cradles spent 20 minutes plus each attempting to adjust their cradle legs and pads as the crane repeatedly lifted and lowered their boats, trying to get a good level fit. The people using Willies cradles had their boats in place and perfectly levelled in 5 minutes flat. The RFYC might be able to put you in touch with him - I suspect that if his design ever gets properly advertised, every other cradle company in the world will go bust.....


Andy

[asathor]

The lifts use straps - wouldn't that be better for the hull?

[Shife]

Originally Posted by asathor

The lifts use straps - wouldn't that be better for the hull?

The keel is supporting the majority of the weight. The pads are just there to keep the boat upright.

[aitchem]

Hi, er,
I've forgot how to calculate bending moments.
Can some nice soul tell me the minimum "I" beam for minimal deflection
when point loaded 3 metres from one end by 2500kg.
Total beam length 8 metres.

[the_sphincter]

minimal deflection? define minimal. what kind of steel?

[aitchem]

Ordinary Structural Steel from a regular steel stockholder.
Its called Grade 46A here.
I am thinking of a Beam "I" Section or Rectangular Hollow Section.

Deflection, about 3mm max.

thx
H

[aitchem]

Heres the bare bones of my cradle.
3 feet gives easy adjustment, chocked up once set level to stop it tipping.
It needs some bracing and the adjusting screws adding, Work in Progress.
Fully bolted construction so it can be tossed down the side of the Garage.

critique.?

[SuperPiper]

Elegant!

But, most cradles in this area have a rectangular base and enough ground clearance for a boat mover's hydraulic trailer to lift and transport.

[Shife]

Originally Posted by aitchem

Heres the bare bones of my cradle.
3 feet gives easy adjustment, chocked up once set level to stop it tipping.
It needs some bracing and the adjusting screws adding, Work in Progress.
Fully bolted construction so it can be tossed down the side of the Garage.

critique.?

I'll take some better pics of the cradle I posted above that may help you this weekend. Why so long and narrow at the bow?