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  #1  
Old 11-15-2008, 06:39 AM
lowe210 lowe210 is offline
 
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Pontoon Boat Conversion to Sailboat

I know this is an out-of-the box type question, but has anyone had any experience with or have any ideas or comments on the thought of taking a standard aluminum pontoon boat and rigging sails on it? I know it would be slow, but sort of looking for that old Spanish Gallion effect (slow, steady, using no fuel). Any thoughts on how to rig it, connect masts, and how it might sail? Thoughts on a keel(s) or other method of allowing it to tack properly against the wind? Is this even a possibility given the physics? Boat would be used on a large lake in Texas.
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  #2  
Old 11-15-2008, 12:56 PM
Stumble Stumble is offline
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I have never heard of something like this, but my initial concern would be reinforcing the mast base to handle the compression loads of the stays. I think there was a discussion on here about those loads, but I couldn't find it.

Other than that I would probably recommend a Cat rig with the mast as far forward as you can and the boom running back across the hard top (if you have one). This is a relatively easy rig, and while it may not be as efficiant as a modern sloop should work for your purposes.

You also will not need a keel. That is actually one of the advantages of a multihull, they don't need the lead swinging around. But you will need to find a place to install two rudders, one on either side.
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  #3  
Old 11-15-2008, 04:06 PM
ancient kayaker ancient kayaker is offline
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Aren't pontoon hulls usually constructed with a more or less circular cross section? I recall renting one, and it was difficult to manouver into the last space alongside the dock as it wanted to skid sideways. I did not have time to learn the technique so was forced to tie up the bow and haul the backside in. If that is common to the breed it would not auger well for sailing in any direction except downwind, so you may find you need a centerboard or leeboard.

As Stumble says, the platform may not handle mast forces, but perhaps you can try an A-mast across the hulls: see this link provided on another thread by Rick Willoughby:
http://www.sail-works.com/KOLIKA/html/kolika_20.html

I did some sailing in my kayak; at first I experimented with small square rigged sails to establish what area I needed and generally explore the issues. Might be a good idea for you; at least you have an engine to get back home with ...
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Old 11-15-2008, 05:03 PM
Stumble Stumble is offline
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I am thinking that twin rudders with lee boards on either side would help to control slippage. The boat will never do very well upwind I don't think, but should be ok reaching or on a run. I would really think about retractible lee boards rather than skegs however, since the skegs would likely add a lit of drag while in power mode. Though they may help the boat track better while running at low speed.
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  #5  
Old 11-15-2008, 05:26 PM
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There's no reason a pontoon boat couldn't be rigged with sails, though it wouldn't do especially well. Leeboards, daggers or centerboards could be fitted to provide lateral area, with rudders at the end of each pontoon.

Of course most pontoons are set up as power boats, with their sterns deeply buried and a heavy outboard dangling off her stern. Neither of these things are desirable for a sailing craft, but just about any rig could be employed. Initial stability would be quite high, and if the aspect ratio was kept low, a reasonably save craft made.

In this vain, a rig that placed less strain on the boat would be a wise selection, say a gaff sloop. The compression loads aren't as high as other rigs and the aspect can be kept low.

She'd sail upwind, but you really couldn't "drive" her hard as she has nearly zero reserve stability, which could result in an easy capsize.

Of course it's a lot more "engineering" then you might think and you'd be well advised to have a designer work out the details, such as board placement, rig location, sail area, etc.

A heavy beam under the mast, some stays and shrouds, possibly a small sprit would be all there is to the rig. A single centerboard hung under the deck could be used, saving the difficulty of building two lee or dagger boards. Retracted, it shouldn't interfere with power operations, nor would it require a case to house it, just some hefty brackets.

A square sail is an interesting option. You wouldn't be as close winded, but that's what the engine is for. This would provide the most bang for the buck, in off wind ability and it could be carried well into a close reach with such a wide sheeting base. I don't think anyone would mistake a sailing rigged pontoon boat, as anything close to resembling a Spanish galleon, but it would be unique and save considerable fuel even when the engine was running.
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  #6  
Old 11-16-2008, 01:00 PM
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sandy daugherty sandy daugherty is offline
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Sounds like fun! With your reasonably low expectations, you will be delighted with any results. Let me echo some of the suggestions above: A pivoting centerboard located near the center of the sail area will probably be easier than lee boards, especially if you can weld it to the existing framing under the floor. While you're under the boat, reinforce the mast base. Try to find a mast with at least a 12" circumference and two halyards. Then call the Used Sail places (Like www.baconsails.com )and tell them what you are trying to do. They will probably get a kick out of the idea. You could steer with a schull oar, or get carried away with twin rudders. Take Pictures!
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  #7  
Old 11-16-2008, 01:11 PM
Stumble Stumble is offline
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Sandy,

I am thinking the problem with a centerboard is that it will require aditional reinforcement of the span between the pontoons. Since they wern't built originally to handle the side loads created by this. I don't know a lot about pontoon boats, but I still think it would be easier to add a retractible lee-board to each side and just pull them when under power.

I have the same feeling about the rudders which is why i suggested the twin rudders. By having them on each stern you should be able to just add some pindle mounts and because the area is already reinforced for the engines should be able to handle the loads.
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  #8  
Old 11-16-2008, 07:31 PM
ancient kayaker ancient kayaker is offline
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Quote:
Originally Posted by Stumble View Post
Sandy,

I am thinking the problem with a centerboard is that it will require aditional reinforcement of the span between the pontoons. Since they wern't built originally to handle the side loads created by this. I don't know a lot about pontoon boats, but I still think it would be easier to add a retractible lee-board to each side and just pull them when under power.

I have the same feeling about the rudders which is why i suggested the twin rudders. By having them on each stern you should be able to just add some pindle mounts and because the area is already reinforced for the engines should be able to handle the loads.
Hm, I'm thinking now of a two-master, sort of a schooner rig; the large mast at the stern in the reinforced area where the engine weight is to carry a driver and a smaller mast close to the bow to carry a small jib. Movable leeboards so you can balance the rig.
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  #9  
Old 11-16-2008, 08:33 PM
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PAR PAR is offline
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A schooner rig wouldn't be a wise idea, nor would any divided rig. Doubling the step requirements on a small boat just isn't reasonable, let alone a make shift motorsailer. Windage will be high enough as a cat or sloop on a pontoon boat.

The same would be true of the centerboard, rather then leeboards. Twin rudders would likely be necessary as most small pontoon boats have a centerline mounted engine pod that carries the outboard, then the actual pontoons themselves, which typically are just capped with an end plate and fitted with a drain plug. Since the engine lives on the centerline, the rudders have to go on the pontoons.

Again, it's a job for someone with the skills necessary, to insure the structural engineering and sailing dynamics can be reasonably accommodated. Speculation of mast diameters and rig selection should also be left to the designer, with an understanding of the clients desires and the limitations of the platform.
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  #10  
Old 11-17-2008, 12:32 AM
eponodyne eponodyne is offline
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Man. Every time I open the index, this thread comes up. I've held off opening this thread, but it's just as I feared: The combining of two fairly bad ideas. Idea #1, the pontoon boat: Great concept done very poorly in almost every case. Slow, hydrodynamically inelegant, and heavy as a lead wedding band.

Idea #2, converting a boat too far outside its design envelope. Yes, people convert boats all the time, and even Picton Castle started her life as a Diesel-fired fishing boat.

For the time and effort and cost you'd incur getting this all to work right, you could probably build a stitch-n-glue plywood catamaran and come in at around the same budget.
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  #11  
Old 11-17-2008, 07:35 AM
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Agreed, but you don't have to make a sow's ear a silk purse, just a hand bag will do and this will be the case with this idea. Though for the purchase price of sails, mast, hull reinforcements, plus standing and running rigging, you could just find a used sailboat and stop fooling around.
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  #12  
Old 11-17-2008, 11:00 AM
ancient kayaker ancient kayaker is offline
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Well, the enthusiasm your idea received has been qualified to say the least! being of the "go for it" personality type myself, I would want to give it a try. The biggest risk I can see is from embarrassment, you can limit that by carrying out the early experiments on a weekday or at night. There will have to be experiments, as you are breaking new ground and that's the only way to establish the parameters.

To do a good job that would yield a tacking craft is going to need all that top-hamper to be stripped off the pontoon to get down to the bare deck, structural alterations to support the mast and rigging, removal of that big mother engine so it sits in the water like a sailboat should, and lots of work below the waterline to install a keel, rudder(s) etc. For safety and convenience you will need a new, lightweight motor. At the end, IF it works, you will have the clumsiest, most uncomfortable cat on the lake. Or you can spend about the same amount to buy a comfortable motor cruiser, which would leave you with the pontoon as well.

OK, forget that option.

What about sailing on a reach? The sailing rig can be much smaller and simpler, you can get away with a leeboard and you could leave the top stuff in place. You will still need a proper mast, sail and rigging though, and the big engine will probably be a pain when sailing.

You could go for sailing downwind and accept whatever you get off the wind with a much simpler arrangement. The square rigged sail is simple and a good physical fit for this type of boat. A folding rig is advisable since the return trip upwind will be under power. I'm thinking of of a larger scale version of the umbrella I carry in my kayak for the downwind stretches. For what it is worth, here's what I would try for Vn. 1.0 :

I'm guessing a typical pontoon boat is about 20 x 10 feet, so I would get a 10 x 10 tarp to experiment with a hinged 2 x 4 mast (widest dimension fore-and-aft) on each side of the bow, 16 ft high, tied together with a 2 x 4 crossyard (widest dimension vertical) supporting the tarp, arranged so the crossyard drops down between a row of seats flat on the platform if possible. Have braces between the yard and masts. A prop on each side can hold it up with a simple backstay on each side; you won't get heavy forces downwind if you don't go out in anything heavier than a breeze. Ensure the backstays cannot tangle in the prop. Have 4 or 5 ties to secure the sail before erecting the masts, with a release cord, then haul in the sheets on each lower corner of the sail and secure to the masts. It should give you a few knots in a light breeze, and give you a better idea of the forces involved for a bigger or more complex rig. You can drop the whole thing and furl the sail at leisure; if it gets a bit too hairy in a blow cut the backstays (and your losses) if you can't let the sheets fly quick enough.

Afterthought: why not sell the advertising area on the sail?
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  #13  
Old 11-20-2008, 12:55 PM
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sandy daugherty sandy daugherty is offline
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The last partybarge I looked at had a structure under the deck that looked like an aluminum version of roof girders, lots of triangulation with thin sheet. Thats why I suggested welding up a hinge mechanism for a centerboard, something like the arrangement on a Stiletto 27 catamaran. You would end up with a line to swing the centerboard out of the water, and another line to hold it down. I agree that twin rudders are in order. They do not have to kick up when you are using the motor. I think an "A" frame for a mast would be the simplest way to go, and a single used jib for a sail. If you retain the 'fence' around the boat and the seats, you would mount a 50 square foot sail to fly above the rails. This would triple the adventure factor by virtually assuring you it will tip over. If, on the otherhand, you are just trying to squeeze a few more giggles out of an old wreck, take everything off, including the big engine, and build your "A" frame to fit a 100 square foot sail. There's no harm in using bilge boards, they could simply hinge off the deck, and flip up when you don't need them.
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  #14  
Old 11-20-2008, 01:47 PM
ancient kayaker ancient kayaker is offline
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Originally Posted by sandy daugherty View Post
I think an "A" frame for a mast would be the simplest way to go, and a single used jib for a sail. If you retain the 'fence' around the boat and the seats, you would mount a 50 square foot sail to fly above the rails. This would triple the adventure factor by virtually assuring you it will tip over. If, on the otherhand, you are just trying to squeeze a few more giggles out of an old wreck, take everything off, including the big engine, and build your "A" frame to fit a 100 square foot sail. There's no harm in using bilge boards, they could simply hinge off the deck, and flip up when you don't need them.

Agree on the A frame but could you really flip one of these monsters with a sail? They gotta weigh a tonne or two at least, to get that kind of force from100 sq ft you would have to be out in a force 12 breeze. not a good situation for any boat let alone a pontoon.

A 50 or even 100 sq ft sail is not going to provide much excitement; 50 sq ft is routine for a sailing canoe. The only risk should be if the rig fails and hits you on the way down. Stand to windward.
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  #15  
Old 08-04-2009, 01:30 PM
benobo benobo is offline
 
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sailing a pontoon boat

I've sailed my old 24' sundeck pontoon boat twice. I created a sun shelter on the front end with an 8' X 10' tarp using 2X2 uprights set in u-bolts along the side with 8' 2X2 cross members fore and aft to span the beam. The forward lentil was set back about 6' from the tips of the pontoons. Loosening the aft tie-downs of the shelter and tying them off to points on the front deck created a square sail that could be trimmed enough to sail a good beam reach using the outboard to steer. One had to be careful on the close reach or it would nose into the wind and one would have to use the motor to come about.

On another occasion I brought along a 6.5 meter windsurfing sail and sailed it back into the mouth of the river against the tide by standing the sail up on the front deck using the carpet as a friction step. It was slow going and got slower as the river narrowed. It was also good exercise, and it made for nice, quiet travelling while the sun set.
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