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Old 24-12-2007, 08:21   #1
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Can we lift our catamarans? idea.

It's getting harder and more expensive to have our boats lifted, not to mention the rules and regs the nice people at the yard put on us, So, Why can't a giant air bag lift the boats? Not a engineer but it seems doable to have a square bag made of the same material as the blow up play yards the kids have. Float it under the bridgedeck and inflate, only need to raise the boats 4' plus. Now you have the boat raised on a raft and tow it to a shallow shore where we can work on it for as long as we want. I wonder how much air pressure is needed to raise a 10ton boat?
Any thoughts?????cpt.craig
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Old 24-12-2007, 08:45   #2
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Quote:
Why can't a giant air bag lift the boats?
There are boat lift companies that make them. You can get air powered lifts as I have seen them for power boats. The issue gets to be the size of the bag. You don't need one big enough to fit totally under the boat, just two big enough to fit on each side. So it can and is done for smaller boats.

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I wonder how much air pressure is needed to raise a 10ton boat?
Just a bit more than 10 tons It was a trick question..

Just look at the volume of air you currently have doing the job when the boat is floating. That should give a clue as to how large a bag you need. You could suspend the boat between straps and two floats. The problem is what a pair of 10 ton lifting straps cost. Now fabricate bags that hold 5 tons of pressure each without leaking. Now what does it take to deploy and retrieve all this from salt water since the barnacles will claim it if you don't. Add a compressor and hose to the rig.
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Old 24-12-2007, 09:33   #3
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Just a bit more than 10 tons
Try again, Paul.

You'd need to displace 10 tons of water. The air pressure required in a bladder float to do this would be substantially less. Just a couple psi in your inflatable dinghy will float you, several friends, an outboard, and a few cases of beer, right?

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Old 24-12-2007, 10:46   #4
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10 tons

12.5 sq.ft. of air bag @10 psi (12.5x144x10)on hard ground,
or 313 cu. ft. of displaced salt water (313x64),
that would be 17.7' x 17.7' x 1' @ .45 psi. (313 x 144 x .45).
Rough figuring.
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Old 24-12-2007, 10:48   #5
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You'd need to displace 10 tons of water.
That only floats it as it is now and so you don't need anything more to do that. It's the getting it totally out of the water part that gets hard.
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Old 24-12-2007, 13:27   #6
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One thing that is being overlooked are the pollution regulations. It is illegal to dump anti-fouling paint directly into the water. Yes, I know it does slough off over time but still, it is illegal to dump it. Modern boatyards have catch basins where the loose stuff blasted off the hull with the pressure washer is collected, dried and hauled off as toxic waste...which it certainly is. I don't think I would want anyone doing that along any shoreline that I visited.
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Old 24-12-2007, 14:50   #7
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bottoms

It is becomming more applealing to think a smooth painted non anti fouled bottom is more the answer with a run over the botom using a hookah when required. Has any one gone down this path?

regards Bill Goodward
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Old 24-12-2007, 15:10   #8
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Quote:
Originally Posted by craig boorman View Post
It's getting harder and more expensive to have our boats lifted, not to mention the rules and regs the nice people at the yard put on us, So, Why can't a giant air bag lift the boats? Not a engineer but it seems doable to have a square bag made of the same material as the blow up play yards the kids have. Float it under the bridgedeck and inflate, only need to raise the boats 4' plus. Now you have the boat raised on a raft and tow it to a shallow shore where we can work on it for as long as we want. I wonder how much air pressure is needed to raise a 10ton boat?
Any thoughts?????cpt.craig
Cool.

It would only cost 5k for two of the 12200 lb ones.



Subsalve Salvage Pontoons - Amron International

But would 5k pay for a trip to a place with a 5ft tide?
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Old 24-12-2007, 16:34   #9
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Heres a couple

HydroHoist Floating Boat Lift PWC Lifts and HydroPort Jetski Platforms - Official Web Site

Sunshine Coast Boat Lifts

AirBerth Boat Lift Storage Systems - The Number One Choice for Boat Lifts


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Old 24-12-2007, 16:41   #10
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It is becomming more applealing to think a smooth painted non anti fouled bottom is more the answer with a run over the botom using a hookah when required. Has any one gone down this path?

regards Bill Goodward
Hi Bill,

Some of the ferries going from Redland Bay to Straddie were trying Lanocote (lanolin) on the bottoms and I heard that initially the results were good.

Might get some more info here.

antifoul lanolin - Google Search

Dave
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Old 24-12-2007, 17:08   #11
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Is Lancote just lanolin??

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Hi Bill,

Some of the ferries going from Redland Bay to Straddie were trying Lanocote (lanolin) on the bottoms and I heard that initially the results were good.
Does that mean that Lanocote used to prevent reactions between dissimilar metals (ie:stainless steel screws in an aluminum mast) is actually just lanolin grease? If so I am in good shape here, I have a massive tub of the stuff. Don't ask why!
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Old 24-12-2007, 18:44   #12
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It is becomming more applealing to think a smooth painted non anti fouled bottom is more the answer with a run over the botom using a hookah when required. Has any one gone down this path?

regards Bill Goodward

I have a friend who does exactly this. Although his cat is just a 28 foot JBE so it does not take much scrubbing but he does live aboard and just gives it a wipe down every couple of weeks. No antifoul has been on the boat for around 2 years as i know. the other advantage is in beaching as a lot of places especially national parks here have said it was fine for him to be on the beach but they would have fined him had it had antifoul on the bottom. Not sure if this is an actual law or just the individual national parks officers discretion.
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Old 24-12-2007, 18:57   #13
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Does that mean that Lanocote used to prevent reactions between dissimilar metals (ie:stainless steel screws in an aluminum mast) is actually just lanolin grease? If so I am in good shape here, I have a massive tub of the stuff. Don't ask why!
I've never used lanocote for disimmilar metals before, but yes, from what "I heard" they polished lanolin grease into the hulls (alloy).

I used it on my dinghy for a try and it seemed to work, but in all fairness, the longest it spent in the water was a couple of weeks at a time while anchored.

I am not recomending this method, it is just something that I heard and will investigate again when I am closer to that stage.

Dave
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Old 24-12-2007, 19:16   #14
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. No antifoul has been on the boat for around 2 years as i know. the other advantage is in beaching as a lot of places especially national parks here have said it was fine for him to be on the beach but they would have fined him had it had antifoul on the bottom. Not sure if this is an actual law or just the individual national parks officers discretion.
I have found no online evidence of this and am of the belief that no one can really do anything as no one controls the area between High and Low water.

This is how those boats used to get away with parking on the beach out front of Airlie for so many years.

I had arguments repeatedly with the powers that be regarding a multihull facility needed in Manly Brisbane.

There isnt one for the public, only one for visitors and members at RQYS.

My argument was that one should be supplied (user pay) as at the moment, people go to the pristine waters of Moreton Island to scrub the bottom and dry out.

The powers that be did not care.

Dave
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Old 25-12-2007, 06:00   #15
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One thing that is being overlooked are the pollution regulations.
We overlook a lot of things from time to time. Bottom paint was overlooked on purpose because it is OFF TOPIC to this thread. We already have a lot of threads about bottom paint. Please join one of those as it is a very worthwhile topic of discussion just not here.
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