Does size matter?

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SteveA

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Recently we had a meeting with the developers for Barrow marina - before I go on for those wishing to throw abuse because I'm going on about Barrow please go eslewhere - anyway, they are proposing a tank 20mx8mx3m to transport boats into the marina.
I thought this would be able to move the majority of boats but several people in the area have voiceds their concerns that it wouldn't be big enough; whay do people think?
 
Obvious question, will that cope with the biggest boat that the pontoons are designed to take? If so, then it is big enough. I am still however doubtful about the whole idea. I am well aware that the idea is an old one and that boat lifts working either vertically or on inclined planes have been made and used for well over 100 years, but I just think it is an over complicated and expensive way to get boats in and out of a marina.
 
The main reason they wish to use this idea is to give the marina 24 hour access - I can't think of any other one on the NW Uk coast that gives this. Using a lock system would loose too much water out of the dock
 
But running this monstrosity, with all the HSE nightmare that goes with it will be cheaper?
It'll still need to lift and move a volume of water sufficient to float a boat (or several)
I think someone's calculator came out of a Lucky Bag.
 
If we assume that the pumps would have to lift the same amount of water as is contained in the tank, then surely (given the efficiencies of the system) you have lifted mass x distance just the same. Therefore theoretically taking the same energy to achieve the same job.
It probably isnt as far apart in running cost as you might think.
In addition, the berth holders will be made to pay the costs wouldnt they? The system chosen should be reliable and have some system redundancy in case of pump or mechanical failure anyway.

Is there a link to this project, would be interested in looking!
 
have you had a look at the falkirk wheel ? seems to work ok.
you should get a link to it on british waterways board site.
 
I have seen large inland barges being moved on an inclined plan in France. It was quite fast and, being counterbalanced, the energy required seemed to be reasonable.
The scheme really sounds interesting. As most AWB are not over 54 feet, it sounds like the tank is big enough. But to speed up the procedure, a tank of 25 meter being able to take two 40 footer at a time might be a good idea?
 
Re: time

What I don't understand is, once the tank is out of the water, how do you get the boat out? You would still need a crane, wouldn't you? You would also still need to wait for that before you can drive the tank back into the water.

I've gone through the Inclined Plane at Ronquieres (B) as well as the giant lift in Strépy-Thieu (B) and while moving the tank/lift is easy, preparing is lengthy. With all sorts of security mechanisms, closing doors etc. this takes the longest time.

Also, you do need a lot of energy, because a boat in the tank vs. no boat in the tank means not the same weight in the tank. With two tanks the heaviest is not always moving down; with one tank, the counterweight needs to be adjusted or you constantly have to adjust the power for moving it.

A simple ramp and boat lift is the way to go, in my opinion. They do this in Nieuwpoort (also B) where the lift just rides in and out of the water.

Victor
 
I think the point made about pontoon size is a good one. Leisure craft are getting larger of course - ours is 9.1m and is relatively small - what sort of traffic are you expecting - if its mostly small seafishing boats (15footers) then it sounds ok - if the cruising yacht market is proven then perhaps it isn't big enough?
 
Re: time

The concept of this tank is to get yachts into and out of a marina that is to be developed in 2008 so there is no need for a crane. The yacht(s) would sail into the tank, this would then be raised to ground level, moved on a bogey to the dock where it would be lowered into the water.
It's been estimated that the difference in transit time between this and the alternative canal/lock proposal would only be about 5 minutes.
It is intended for cruising yachts. most in this area are in the 25' to 35' range, but at a recent meeting we had with the developers some voiced their concern that this tank wouldn't be wide enough for catamarans. Although the total width is 8m the door opening will be less.
 
Re: time

I don't know if I like the idea of my boat being moved in a tank laterally.... surely the speed would have to be incredibly slow to avoid it slopping.......

Interesting idea though....

I still find it hard to believe that a pump would cost more than the energy expended in moving that volume of water......
 
Archimedes priciple?

[ QUOTE ]
Also, you do need a lot of energy, because a boat in the tank vs. no boat in the tank means not the same weight in the tank. With two tanks the heaviest is not always moving down; with one tank, the counterweight needs to be adjusted or you constantly have to adjust the power for moving it.

[/ QUOTE ]

Erm Archimedes might disagree with you on that one /forums/images/graemlins/smile.gif

The displacement of a yacht is how much water it displaces, so if you have two tanks they would both weight the same, whether one is full of boats or not....(That's if the water level and volume is the same in each tank of course)

So it seems that two tanks would be the way to go as long as they are connected so as one goes up the other comes down
 
Counterweights and energy requirement.

With the tank in position at the seaward end, the water level and hence the weight of the load (with or without yachts) will vary with the tide.

Therefore, unless there is a complex system to vary the point of loading to ensure the weight is constant, there will be a huge variation in weight to be moved.

A half metre variation of contained water would change the weight by 80 tonnes, and no doubt at certain points of the tide, that variation could occur during the time taken for some hapless user to get organised, get in and get secured to the tank.

Alternative, to vary the counterweight by pumping water.

Other alternative, to have a lock, a far more mainstream solution, along with back pumping as time of year, tide and demand dictates.
 
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