Inflatable hull lifters. Does such a thing exist?

[Valiente]

Marina side Coffee conversation of a mix of knowledgeable pple and armchair sailors in pre ARC days:

One guy talked about inflatable hull lifters being able to haul out of water the rear or fwd of a catamaran hull, so allowing sail drive works without putting the ship to shore.

My google search has not provided me any evidence of existance.

Has any1 used/seen/heard of such a thing?
Thanks in advance.

[hellosailor]

Not designed as a portable drydock, but there's no reason you couldn't just use conventional lift bags for that purpose. Or for that matter, a truckload of empty used oil drums or polythene drums.

IIRC about 5-10 years ago someone built an entire catamaran, or large raft, out of liter pop bottles. Purpose being something about highlighting recycling perhaps.

[serendipitous]

I have seen this done in Le Marin, Martinique. It seems that careful placement of straps would be required to ensure that the bags do not shift.

[Valiente]

Originally Posted by serendipitous

I have seen this done in Le Marin, Martinique. It seems that careful placement of straps would be required to ensure that the bags do not shift.

Was a whole hull lifted or just the stern?
Given the bouyancy of the bow, the geometry needed to have Sail drive out of water seems difficult to achieve.
Thats why i am moderately skeptical.

[Lepke]

Heavy duty rolling lift bags are made. I've only seen larger ones made for launching or retrieving very large boats or ships from a slopping bank. The bags work like a series of logs. They are placed under new construction and inflated. The vessel is allowed to roll down the bank in a controlled manner. As a bag emerges from the uphill end it is re-inserted at the down hill end. For hauling out the bags are placed in the water and on the bank. The ends have places for line to hold them in position. Otherwise the same as launching.
The bags are expensive. You'd be ahead to pay for a haul out.

[Sailmonkey]

Simple google search.....and I’ve seen it done

https://www.google.com/search?q=cata...iw=320&bih=454

[Valiente]

Originally Posted by Sailmonkey

Simple google search.....and I’ve seen it done

https://www.google.com/search?q=cata...iw=320&bih=454

Jesus!
What went wrong in my Google search!
I dont recall what terms i used. I found the rollers but not this.

So, aparently easy haul out of the rear section of both hulls, this time likely to be cheaper than travelifting!

[belizesailor]

Originally Posted by serendipitous

I have seen this done in Le Marin, Martinique. It seems that careful placement of straps would be required to ensure that the bags do not shift.

Ive seen them there too and a few other charter bases. Very handy thing if you need to service a sail drive between charters.


A friend of mine also had custom lift bags built for his Shuttleworth 65.

[Valiente]

After re reading "Google search for dummies"
[emoji20]

[Mango51]

Having all the bouncy in the center is great but you waste a lot of material and money in the gap between hull and water line. Maybe some sausage style fenders chained in the middle and tide on he sides. 321 cu. in. Equales a gallon and a gallon has approx 8 lb of flotation. My be one side at a time would be cheaper. Good luck.

[rbrentp]

I bought a set of "emergency Flotation Bags" for keeping a 20,000 pound lead keel from dragging down a boat. They can be slid under the hulls and strapped or placed in the bridge space. They tie to a scuba like tank via high pressure lines and when in place you turn the knob and up it goes.

One end or one side is easier for obvious balance reasons, but it has the lift to clear the whole boat. Was thinking of a floating dock when I got it but it is only serviceable for a limited time as the bags aren't really barnacle proof.

Still tinkering with the idea of enclosing the bags in some kind of finger that could stay in the water and act as a lift.

Brent

[bigman1]

Google turtle pac Aussie firm all sorts inflatable bags.Including yacht bouyancy
kits.

[nhschneider]

When we were in Pangkor, Malaysia, we were hauled out by a 'Travel Lift' that used inflatable bladders instead of slings. It turned out to be one of the least stressful haul-outs we've ever done.

[john2445]

Correction to Mango 51: 231 cubic inches = 1 US gallon.

[hellosailor]

The bladders on that travel lift appear to be for cushioning, not for "lift" like the OP wants.

While putting a lift bag under the bridge of a cat might seen like a waste of good buoyancy, it also allows the hulls to keep the bag in place. Allows the whole thing to stay in balance without the need to rig straps over the odd shape of the cabin.

Likewise the bladders on the slingless travel lift, allow for the whole structure to be lower and have less need for clearance versus the boat's superstructure.

Gallons, ounces, cubic feet...this is where the metric system is the flat out winner. Liters, kilograms, cc's...all neat and simple conversions.