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Go Back   SailNet Community > General Interest > General Discussion (sailing related)
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  #31  
Old 03-07-2007
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Tartan34C will become famous soon enough
Did you look at the small fishing boats designed by a UN commission that were designed to be built by third world labor on the beach so to speak. Look at their program to see what they decided fishermen needed and they might be a source of development money. Interesting boats and well thought out in terms of how to build with unskilled labor.
All the best,
Robert Gainer
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  #32  
Old 03-07-2007
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Quote:
Originally Posted by zmfmd
The difficulty im having is with selfrighting issue.
The RNLI in the UK carry an emergency inflating bag on a goal post over the stern of their rescue ribs. It does what you suggest,
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  #33  
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Quote:
Originally Posted by Idiens
The RNLI in the UK carry an emergency inflating bag on a goal post over the stern of their rescue ribs. It does what you suggest,
Nice idea and I had forgotten about them. I wonder why you don’t see them more often on a offshore multi-hull. But can you use them twice or is it a two strikes and your out type of thing. The Rolf Eliasson solution is nice because it solves several problems all at the same time. It gives you a nice roomy dry place to be and raises the height of eye for visibility and because it’s a built-in by design you can roll the boat as many times as necessary to get the job done. Sometimes it's nice to know you can roll three times and still enjoy coffee.
All the best,
Robert Gainer
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  #34  
Old 03-07-2007
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Quote:
Originally Posted by Tartan34C
.... I wonder why you don’t see them more often on a offshore multi-hull. But can you use them twice or is it a two strikes and your out type of thing.
I suppose it is one thing to right a rib and another a multi-hull. Upside down with the mast and sails up, it must need a crane to right a multi-hull. I thought multi-hulls do have an option for an emergency airbag up the mast to disuade them from totally inverting, then with a lot of luck and some wave motion they might self right, but I am no expert. The RNLI air bag is intended for emergencies and is very big compared to the rib when inflated, so it would have a lot of windage, if it were left inflated. If they carried spare CO2 cylinders the bag would be reusable, but probably isn't reused by the RNLI.
Talking of airbags, I have seen articles about mono-hulls fitted with emergency airbags inside attached to the keel bolts - to prevent the boat sinking, but I have no idea were to buy them.
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  #35  
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Most multihulls don't have an option for the emergency airbag up the mast, since it adds considerable weight aloft and windage. It would be a good idea... but rarely implemented.
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You know what the first rule of sailing is? ...Love. You can learn all the math in the 'verse, but you take
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  #36  
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Quote:
Originally Posted by Tartan34C
Did you look at the small fishing boats designed by a UN commission that were designed to be built by third world labor on the beach so to speak. Look at their program to see what they decided fishermen needed and they might be a source of development money. Interesting boats and well thought out in terms of how to build with unskilled labor.
All the best,
Robert Gainer
Thanks for your pointers..i tried to find info re the above in the site www.un.commission..a lot of data but what not what you ref. to..am i looking in the right place?
Also re Rolf Eliason solution, sorry, but what are you talking about?..
Your suggestion of an electric motor/generator/backup batteries is a good suggestion. particularly using the wt. to provide part of the ballast...( this made me think of a small deisel inboard (low CG) instead of the the outboard (high CG)...BUT, these would be expensive for the targeted users (the affordability criteria)..and again this made think that maybe i should think also of another category of people who can afford extra expences.
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www.fao.org/docrep/003/t0530e/t0530e00.htm
www.fao.org/docrep/007/y5649e/y5649e00.htm

Just to get you started and give you a way to get in touch with the group that did the work for the UN. I don’t know much about the project but one of the people at work is familiar with the project and I will ask him about it tomorrow.

Rolf Eliason is the author of the article in Professional Boatbuilder. He did some work on designing self righting into boats and may be a good source of information.
All the best,
Robert Gainer.
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  #38  
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Most wet lead-acid batteries are effectively destroyed if immersed in water. If the batteries for an electric-motor-based backup propulsion system were in the bilge, and water entered the bilge to above the vents on the batteries... chlorine gas would be released, and the batteries rendered useless. Not exactly ideal.... This doesn't occur with sealed AGM or gel-lead-acid batteries, but they are considerably more expensive.

The only, really cost-effective, alternate propulsion system is probably sail-based. Having redundant engines/transmissions/motors is an awfully inefficient, heavy, and expensive way to provide alternate propulsion capabilities.
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You know what the first rule of sailing is? ...Love. You can learn all the math in the 'verse, but you take
a boat to the sea you don't love, she'll shake you off just as sure as the turning of the worlds. Love keeps
her going when she oughta fall down, tells you she's hurting 'fore she keens. Makes her a home.

—Cpt. Mal Reynolds, Serenity (edited)

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  #39  
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Sailingdog,
That is a problem and it was dealt with in earlier projects by storing the batteries in a dry box with a self closing vent system or by using sealed batteries. I am not familiar with the details but you could talk to someone at Elco and they will fill you in on how they do it nowadays. Or get in touch with the “Electric Boat Association” in England.

Having sails is definitely a possibility. But depending of what you want to use the boat for a sail may not give you the maneuverability you need and if you want to be storm capable during rescue work a sail would not be a good choice. For a fishing boat a sail might be a great back-up or in fact a sail might be the primary propulsion on the fishing grounds.

Lots of twin engine boats out there. A twin engine boat has redundancy for everything except fuel problems. A twin diesel electric with batteries would have redundancy for generation, drive motors and a back up of some number of hours power at slower speed by using the batteries so even a fuel problem might not be dangerous.
All the best,
Robert Gainer
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  #40  
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Good points Robert...

Part of the real problem is that no one design or solution is really going to be applicable to every use of a boat. Boats are generally designed for the function they are going to be used for. Tugboats are designed with oversized engines, transmissions and props... which would be totally ridiculous on most other boats their size, but completely necessary for them to perform their function.

Most boats do not need to have self-righting, self-bailing, unsinkability, and alternate forms of propulsion as a general rule. Affordability would be a nice feature, but it is often excluded by the design and function of the boat. You can't really design an inexpensive tugboat, since any boat that is sturdy enough and powerful enough to function as a tugboat, is going to be relatively expensive.

This is true of most designs... and it just seems to me that zmfmd has an unrealistic idea that there is a perfect boat, in the Platonic idea of perfection. No boat is perfect, and no boat can be perfect for all purposes. Different functions will have different requirements, and some of those requirements are less useful for boats with other functions as their priority.
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Telstar 28
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You know what the first rule of sailing is? ...Love. You can learn all the math in the 'verse, but you take
a boat to the sea you don't love, she'll shake you off just as sure as the turning of the worlds. Love keeps
her going when she oughta fall down, tells you she's hurting 'fore she keens. Makes her a home.

—Cpt. Mal Reynolds, Serenity (edited)

If you're new to the Sailnet Forums... please read this
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
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