Pontoon Boat Conversion to Sailboat

[lowe210]

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.

[Stumble]

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.

[ancient kayaker]

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 ...

[Stumble]

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.

[PAR]

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.

[sandy daugherty]

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!

[Stumble]

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.

[ancient kayaker]

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.

[PAR]

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.

[eponodyne]

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.

[PAR]

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.

[ancient kayaker]

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?

[sandy daugherty]

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.

[ancient kayaker]

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.

[benobo]

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.

[GOTTABSOMEWHERE]

HERE'S AN IDEA FROM 100 YEARS AGO

Go to www.gundalow.org

Check out that sail................it works..........I did it

Go to stabiliyty section here and check out photos

[ancient kayaker]

Scaling that down to typical pontoon boat size gives you 100-200 sq ft so the previous posts are on the right track. Leeboard need not be very large if upwind work is not intended, say 3% of sail area. The only problem I can see is the starter of the thread appears to have gone away; only one post!

[souljour2000]

I say go for it... sometimes you just want to have fun and you know pretty much what you can get away with and what you can't. Who is going to take a friggin square-rigged former Sunray 24' pontoon boat out in more than say 12-15 knots of wind which is way more than enough to get this thing going good anyway? If one did then they should be a fairly experienced sailor with some different boats and lots of miles under their belt, not to mention a good basic understanding of physics. In the meantime I say lots of fun with this project and consider putting an A-frame mast or a "stump" mast on it with a real big lateen sail hangin off it or in the case of the a-frame mast "between it".Some slots welded against the insides of the each pontoons and toward the rear...and then with slots in the deck above these lower slots will allow for two big keelboards to be raised and lowered...let us know how it turns out...you'll have to make some adjustments after the first trial I am sure but sounds like a hoot!

[danerandall314]

http://apacolypso.files.wordpress.com/2010/01/dsc01204.jpg

In November of 2009 a friend and I bought a 20ft old pontoon for $150. For the last 2 months we have been converting it into a sailing tri-meran. We used the pontoon flanges to install deckboards, Iako mounts, storage containers, and a paddle seat. We built Iako's out of PT 2x4 (rather use aluminum tubes but too expensive). We built the outriggers out of four 6'' thin walled PVC piping. The ends were heated and bent upwards and we installed two saddle mounts using PT wood to each outrigger. They were eventually capped, painted, and we installed drain plugs on each one. We used bamboo for a lot of applications on the boat. We split 5' bamboo into four sections and built 5'x8' platforms to set up our tents on. The stubmast, mast, and boom are all made out of spar varnished bamboo. The sail was made out of using thick polytarp. It was cut, taped, sewed, and grommets were mounted on the luft. The centerboard was created out of laminated red oak, sanded and varnished, and installed with a swing mount to one of the pontoon flanges. There is no rudder, we used a 11ft 2x6 piece of black locust, cut, routed, sanded, and varnished as our steering oar. If you want to check out our boat and designs go to www.apacolypso.wordpress.com, and yes we know we spelled it wrong. Check it out!

[souljour2000]

Cool...nice pics..those oars are stout-looking..I miss my old rowboat now...well I am in the market for a dinghy...either to build or buy..anyways...let us now how she sails...the main thing is you have something that will get you onto the water.... so you's can have FUN....

[GOTTABSOMEWHERE]

Looks like you are having fun..............I have no idea if that will work but I would comment on is your choice of sail.

Take a look at these pics of my "tridory"

[sharpii2]

http://apacolypso.files.wordpress.com/2010/01/dsc01204.jpg

In November of 2009 a friend and I bought a 20ft old pontoon for $150. For the last 2 months we have been converting it into a sailing tri-meran. We used the pontoon flanges to install deckboards, Iako mounts, storage containers, and a paddle seat. We built Iako's out of PT 2x4 (rather use aluminum tubes but too expensive). We built the outriggers out of four 6'' thin walled PVC piping. The ends were heated and bent upwards and we installed two saddle mounts using PT wood to each outrigger. They were eventually capped, painted, and we installed drain plugs on each one. We used bamboo for a lot of applications on the boat. We split 5' bamboo into four sections and built 5'x8' platforms to set up our tents on. The stubmast, mast, and boom are all made out of spar varnished bamboo. The sail was made out of using thick polytarp. It was cut, taped, sewed, and grommets were mounted on the luft. The centerboard was created out of laminated red oak, sanded and varnished, and installed with a swing mount to one of the pontoon flanges. There is no rudder, we used a 11ft 2x6 piece of black locust, cut, routed, sanded, and varnished as our steering oar. If you want to check out our boat and designs go to www.apacolypso.wordpress.com, and yes we know we spelled it wrong. Check it out!

I love its 'Flight of the Pheonix' look.

I just wonder if its going to be a bit under canvased with only 80 sf of sail.

It looks to me like you have 300 to 400 lbs of boat here. Add to that two 200 lb sailors and maybe 200 lbs of provisions and equipment and you're around 1000 lbs., giving you an S/D of 12.8, or there abouts.

That would be like a modern trimaran reefed down. A lot of them have S/D's in the high teens or low 20's. Of course, Polynesians did not have any way to reef.

Still, I think its kinda cool. An alternative for the multhull concept, to the stressed out, hyperlight, over sparred, don't ask the price, speed machine.

It will be interesting to see how it performs.

[kalalaukind]

Thank you for your feedback. I imagine it is quite obvious that this is the first boat I have ever designed and built. She was designed as you have described, "an alternative for the multhull concept, to the stressed out, hyperlight, over sparred, don't ask the price, speed machine." We wanted a slow, stable coastal cruiser that you could camp on if need be and that cost less than $1000. If she breaks 4 knots I will be thrilled!

As you also mentioned, Polynesian rigs were not built to reef and my greatest concern was putting up too much sail area and being accidentally caught in heavy gusts. I would rather cruise slow for two months than paddle back to the land onetime with a busted sailboat. We have incorporated a spiller/brail line for spilling some wind in those conditions. However, the natural strength of our large diameter bamboo mast, yard and boom are essentially untested and the last thing I wanted to do was build a sail that might shred them in gusts.

Luckily our 11 oz polytarp sail(stuff is strong), material and labor only cost us $75. At less than a $1/sf I would be happy to replace it later with a larger one if the rigging can handle it. A hint for budget sail builders, common automobile upholstery shops will sew a sail with heavy duty UV treated thread for a fraction of the cost per hour of a sail shop and they will do a good job if you tape up the seams and show them where you want it sewed.

I will update this thread when we have 'flown this phoenix' in the waters of South Florida.

yaarrrggh!

edit: This boat is more of a prototype for exploring the use of pontoons in affordable, trailerable and durable sail boats. The ultimate design of which is sketched out our site. A pontoon tepuke, in the style of the island of Taumako could be built with two pontoons secured stern to stern. This would make a double ended, single outrigger proa, driven by an enormous crab claw rig. As I see it, a welded aluminum box frame could be fabricated to span both the sterns of the pontoons and simultaneously provide an elevated tower to connect Iakos to and ample storage space for supplies.

Link to my pontoon tepuke sketch: http://apacolypso.files.wordpress.com/2009/11/tepukepontoonboxdeck.jpg?w=510&h=265

Link to a video of an actual tepuke from Taumako underway: http://www.youtube.com/watch?v=KXt4PL2R1aU

[souljour2000]

Looks like a fun project...I do have a few words of advice. If you are not used to sailing South Florida in the winter...it would be good to know that it can get dicey out there when the winter cold fronts occasionally get further south. Frankly,the water will be cold whether a front comes down or not and you guys will be in a wet boat.....I would bring alot of wet weather gear and extra dry clothes .......It is an El Nino year so things are a bit screwy.Be safe...consider hunkering down somewhere if a cold front approaches..The winds are generally highest Before the rain actually arrives...Make sure you have at least a handheld VHF radio...keep it someplace where it wont fall overboard easily and have extra batteries...aarrggh! Okay..I'm done...Have lots of fun...let us know how your trip went..or we will check the website!

[kalalaukind]

Thank you for the advice, it is well appreciated. I just now noticed you are from Sarasota. I was born and raised in Venice by a family of true crackers. In fact, I have considered launching from the house my great grandfather built in Nokomis near Casey key. I am familiar with the variable winter weather down there, but what type of affordable wet weather gear would you recommend for such an adventure? Shorty wet suit maybe? Lots of wool?

Last year danerandall314 and I took a bicycle camp trip from Tampa to Punta Gorda where we got a taste of those fronts moving south. We did as you suggested and hunkered down for a few days at what we thought was a hidden public beach park between Siesta and Casey Key. It turns out we had been camping in Stephen King's backyard, whom we met the day we left as we traversed his palatial estate at 7AM. We had been pushing the call button on his private gate which was separating us from the public road with no idea who lived there. We both got a laugh when we realized we may have in fact startled Stephen King himself.

The beach camping bans and the ridiculous permitting process common to all of Florida is the number one reason we designed and built a vessel of this type. So, we can pitch tents on the boat when we have to and avoid statute and ordinance violations.

We do have a handheld VHF, USCG 2 mile Scotty Sea Light for night time mooring, flares, preservers, a horn, and enough fishing supplies to open up an outfitters shop.

Anyhow, thanks for the time. This site rocks!

[troy2000]

Getting back to the original question, how about a standing lug rig for a motor-sailing pontoon boat? Short spars that can be stowed onboard, simple rigging, reasonable efficiency, no boom as a potential headknocker on a party boat. And a pontoon boat is certainly wide enough to set a loose-footed sail at a good angle...

[souljour2000]

That story about meeting Stephen King is great...that area is strangely enough called...well..Midnight Pass....Rather apropos eh? The Pass was "closed" in the early eighties by an area artist who owned the first house on the north side of Midnight Pass.(Stephen King's is the first house on the south side of the old Midnight Pass.)Anyway..the artist-guy rented a bulldozer after getting permission from the County (my..my.. alot has changed)and shoveled sand until the tiny pass was closed...it changed the biology of the back bays along the ICW that were now isolated from the regular saltwater mixing. Ever since...many locals have been calling for it to be re-opened but last year the state DEP pretty much ruled out that ever happening...because alot of sea grass has grown in that back bay area now...and the Feds don't play with "established" passes anymore unless it's a federal channel...They still call the area "midnight Pass" and its a cool place to explore and chill out...with access for boats on the bay side and gulf...and trails winding amongst the sand dunes...
It's going to take a direct hit hurricane to re-open that pass now...

I can't recommend any rain gear or cold weather gear except I have heard hollowfill is good and probably gore-tex and so forth...I really don' know though honestly...anyone?

[ImaginaryNumber]

Here is a catamaran made with steel tubes.

http://www.duckworksmagazine.com/04/s/projects/biplane/index.cfm

[ThomD]

I always figured that the low hanging fruit with pontoon boats was creating them with better hulls rather than using bad hulls for other projects, though one works with what one has. I did a small cat with that idea in mind at one point. Pontoon boats can be pretty useful, though they sorta depend on low gas prices... Have fun with the project.

[troy2000]

Getting back to the original question, how about a standing lug rig for a motor-sailing pontoon boat? Short spars that can be stowed onboard, simple rigging, reasonable efficiency, no boom as a potential headknocker on a party boat. And a pontoon boat is certainly wide enough to set a loose-footed sail at a good angle...

Bump....

[sharpii2]

I just got done doing some meatball math.

I calculate a 20 ft pontoon boat should have a righting moment of around 9,500 ft lbs max.

I came up with this number by the distance between centerlines of the pontoons multiplied by the max weight of the craft.

16 ft * 3.14 sf * 62.4 lbs/cf * 6 ft Beam / 2 = 9405 ft/lbs

The 6 ft Beam came from the pontoon boat being 8 ft wide, to be trailer legal in all states, minus the two foot width of a pontoon, which equals half the width of two pontoons.

If its loaded down any more, the lee pontoon will go under. If it's loaded down less, the windward pontoon will come out of the water.

Using stays to hold the mast up, I calculate the mast will have about one ton of compression at the step.

The two windward stays will have around 1500 lbs of tension each.

Its fascinating to see how fast these numbers build up.

Just for the fun of it, I sketched a pontoon boat rigged with a single gaff main. Getting a jib to stand on anything this loose could be more than a challenge, so I did away with it altogether.

Part of the fun of all this is to see if I could come up with a real sailboat that could, by definition, make decent windward progress and be able to shorten sail, if need be.

For lateral resistance, I drew a centerboard case placed under the deck, next to the motor well. The case is lengthened provide a place to hang a rudder on. The whole business would bolt onto the deck from underneath and hopefully re enforce it there under the mast. Up front it would be kept upright with a pair of large gussets. Aft it would be supported with a pair of guy straps.

The odd looking rudder has a disk like rudder extension which is supposed to 'roll over' any logs or stumps it might meet. The pintles would be arranged so the whole thing could drop about 6 inches deeper.

My guess is that it could do maybe 6 to 10 knots reaching or running and maybe half that, made good, going up wind.

The range of conditions it could sail in would be quite narrow. About 12 to 24 knots of wind. More is too much. Less is simply not worth the trouble.

A 6 to 10 hp outboard would be used when the wind is light.

When the wind is too strong, it stays tied to its slip.

See attachments below.

[silverbear]

I just joined this forum due to this thread. I am no sailor, but have lived on lakes in northern Minnesota for the past sixty some years. Next summer I intend to rebuild a 20' pontoon boat into a kind of cabin version of a houseboat... able to go for week long cruises for a week or so at a time with my dog Aaniimoosh (Ojibwa for 'dog')... Huck Finn days on the lake, fishing, swimming and lolling about. Since I live on social security I want to use little gasoline for getting around. The cabin will be small, 8' wide X 8' to 10' long depending on the length of the boom and steering setup... will know about that next summer after rebuilding the deck. Cabin will be at the rear of the deck with access to the motor from a hatch at the rear of the cabin. The heavy 40 hsp motor now on the boat will be replaced with an old 10 hsp Evinrude from the 1960's which will be modified by removing the two stroke engine and in it's place will be a flat plate with a vertical shaft 4 stroke 5.5 hsp motor bolted to the flat plate and it's crankshaft joined to the original lower unit by means of a coupling. Exhaust will go out the lower unit under water as the original engine did. The motor comes up on sale now and then at Harbor Freight for around a hundred bucks. Steering and gear selection will be normal. No electric start, just pull start with a kill switch at the controls forward of the cabin. At the bow will be the mast and sail from a Grumman canoe sail rig. This will be used mostly for downwind sailing to save fuel. Slow is fine as I will already be where I want to be, on the lake, and going to another anchorage for some different fishing can take all day for all I care.
Some years ago I had an 18' pontoon boat and rigged up this same sail, again using it downwind. I just used the motor for steering, which was not very effective. No, it was never fast, but what great fun that was running silently with wind power. I recall a day when several bald eagles were riding the thermals directly above me... my sail was full and it seemed like I, too, had a "wing" and was flying with the eagles. Beautiful memory. Different boats have different purposes. The one I will be building will suit my needs and budget, allowing me to spend much of my summer on the water and at least part of the time moving along by wind power. Perfect.
From reading this thread I'm already getting some ideas on how to improve the sailing aspect of this boat, allowing me to use the sail more often and more effectively. All I know about sailing is that it is fun.
Why couldn't I add more rudder area onto the outboard motor and steer that way? Should be easy enough to make up an aluminum plate affixed to the lower unit. I would not be using this rig in rough water and in a big wind would use the motor to get behind an island or into a protected bay to wait it out.
Many thanks for past comments and for sharing your knowledge with an old newbie.
Silverbear

[sandy daugherty]

This is an intriguing challenge. Here's my WAS (wild-assed suggestion. Since your cabin structure will have a lot of windage, I suggest you attach a rather large rudder surface to your outboard. Perhaps a 1.5 square foot flat plate. At the bow you will need a centerboard or daggerboard of the same size that can be raise or lowered from the helm. Consider letting it drop down on a hinge pin to keep you vessel amphibious, at least the bow, for those morning visits with Dog (english for Aaniimoosh) This will allow you to use the sail in a larger range of wind directions. But don't go for much more sail area; there would be stability issues.
I suggest the forward board go near the bow, Like a Chinese Junk because your trim under sail will vary wildly because of the cabin. being able to vary how much lateral resistance it produces will help a lot.

Unless you have access to a fairly sophisticated machine shop, I would advise against your engine plans. The cooling issues alone would require some very expensive trial and error. Far better alternatives exist.

[Wavewacker]

Yes, I think a junk rig would be more appropriate.

We make more pontoon boats within a hundred mile radius of me than any place on earth! Bass Pro, Lund, and a bunch of others that slap different brands of a plate. Few such boats weigh anything near 9,000 pounds, if they do they are high dollar I/Os. All round pontoons are mounted with a flange at the decking that is not designed to hold the boat at an angle beyond about 20 degrees. I have seen pontoons snap while sitting on the hard sideways at a steep ramp. With a 2' tubes you have 4 to 4 1/2' distance between the tubes and the decks are usually wider extending beyound the tube and all of that is within 8 or 8 1/2 feet. Some are fitted with planing hull plates on the bottoms, not just round tubes and I doubt you can take them off without messing up the pontoon, it would be alot of work and welding to remove them. And some have skeggs as well.

If you must use aluminum tubes, take them off the pontoon and build a proper frame, hanging the deck lower, widen the beam and provide support for what the sail rig might require, then you'll have a cat that might get a few scratching their heads instead of laughing.

You can put a tarp up on the awning and catch enough wind to move a pontoon boat, they are really bad anyway with air draft with the deck fence. You can't take the fence off a pontoon boat as it is a required safety feature, unless you replace it with safety lines, that is if there is any kind of motor on it. And, you can't take the seats off unless there is a cockpit, or with hand holds somewhere for passengers, again, if there is any motor on it.

I'd agree with others, pull a sailboat and sail when you want to sail and leave the barge as it is.

But try it out, good luck with it, I'm no expert.

[sandy daugherty]

My inpression of Silverbear's question is that He isn't going to spend more than a couple hundred dollars on this lake raft, and sailing qualities aren't even on the list of considerations. A Huck Fin raft with a canoe sail and a motor is a hundred years ahead of the technology of Mark Twain's youth, and that places us somewhere in the Fifties, I think. I believe we are talking about a floating camp that is somewhat self propelled.
I doubt Silverbear is worried about deck fences or lifelines, or even going to weather. If he wants to go somewhere he will probably wait for the wind to change.

[Wavewacker]

My inpression of Silverbear's question is that He isn't going to spend more than a couple hundred dollars on this lake raft, and sailing qualities aren't even on the list of considerations. A Huck Fin raft with a canoe sail and a motor is a hundred years ahead of the technology of Mark Twain's youth, and that places us somewhere in the Fifties, I think. I believe we are talking about a floating camp that is somewhat self propelled.
I doubt Silverbear is worried about deck fences or lifelines, or even going to weather. If he wants to go somewhere he will probably wait for the wind to change.

Yep, and that's why I said go for it, it should be fun and funny too. Infact, I'd do it too, put on a straw hat, some Big Ben's wear my army boots and get a corn cob pipe! We know how to do things up right in the Ozarks!

Tires off an old lawn tractor make great bumpers at the dock. ;)

[silverbear]

Thank you guys for your responses. Yes, it would in fact be something like a glorified raft with some creature comforts. I think of it as a pontoon 'cabin boat'rather than houseboat. I do want for it to look respectable even if it is a little on the oddball side of the lake. I'll polish up the pontoons some to make them new looking. I did that on a sidecar I made for a light motorcycle. The sidecar was made from a former 17 ft. Grumman canoe (much modified) and I was astonished at how well it shined up.
The cabin will be sided in cedar shakes and there will be shutters inside the windows which will have stained glass panels of cat tails, wild iris, that sort of thing. I had a stained glass studio onceupona and still love the stained glass. So a little bit of elegance mixed in with funky. Heat will be from an elegant Petit Godin wood stove I used to have in an old Airstream. It is air tight, has a small footprint and can burn either wood or coal. I'd like to be able to be on the water until snow is in the air around the beginning of October.

Regarding the power for the boat. The sail is only about 50-55 square feet. I've given a lot of thought to the air cooled engine conversion and think it will work fine. I do have a friend who works in a machine shop if something special needs to be made up in a coupling. But I think something can be made up from standard parts.

Yesterday I picked up a 177cc 4 stroke Predator vertical shaft engine from Harbor Freight for $99.00 on sale and paid another $20.00 for an extended two year warranty beyond the two year warranty that came with it. It is intended to replace 6 hsp engines. I imagine it will put out more than that by a bit by opening up the air intake with better breathing. There are also better carbs available from the go kart racing folks which will fit on there if I want to goose the power, which I don't anticipate. So, if the engine blows up I return it with no questions asked. But I don't expect it to blow up. I don't see a cooling issue, either. The engine shrouding is designed to cool the engine from the flywheel blades and it is designed to either run a lawnmower all day or a stationary industrial type of use. Also, northern Minnesota tends to be on the cool side even in the hottest part of the summer. And I don't foresee running the engine for great lengths of time continuously. That's where the sail comes in to play. Speed is not an issue, as slow is good. Heavy winds will drive me to a secluded bay or the protected side of an island. This boat will never see big water. I'm mostly interested in the motor power to get me where I want to go and for being able to idle way down for trolling while fishing.

I will retain deck railings for the open portion of the deck and run the railing right up to the cabin.

Now, I have a question. I have yet to measure the length of the boom, but it must clear the cabin and may mean that I need to extend the front of the deck a bit. I have a good idea how to adequately support the mast and deck extension, especially with the small sail size I don't think that is going to be a problem. I am wondering about the sail filling and wanting to dig the front of the boat down in a strong wind. I'm hoping that the weight to the rear where the engine, gas tanks, batteries (for solar electric) and cabin are will be enough to counteract that digging effect, but I'm just guessing about that. Any opinions? I know this is an odd project and the budget will be low and tight, but just the same, I want to think it out well, have a good and workable plan and end up with a nice pontoon cabin boat which has some sailing ability. I'd like for when a fishing boat goes by for someone to say out loud... "that's cool" and ask some questions about it. Don't want an eyesore.
Thanks for the tips on the size of the rudder affixed to the engine and the forward mounted centerboard to improve handling under sail.
Silverbear

[Chase_B]

interesting

[CatBuilder]

This is a great thread and great idea. Very interesting. I hope to see pictures of this project at completion.