Kayak Trimaran Concept Help...

Oh Ok, i think understand now where you're coming from better. thanks for that eye opener i would have never looked at it that way but it makes scenes now that you summed it up like that.

I'm going to see if i can get my kayak tomorrow and take it down to the metal shop around where i live. maybe they can melt it down into a few lawn chairs or maybe even a table. And to hell with ever going into the ocean again :/ not even going to touch the beach again. or go out side.... just going to watch videos of stuff for the rest of my life :'(

 

Ermaclob,

Others have made something similar, the guys at this web site do something similar with canoes. http://www.songofthepaddle.co.uk/forum/forumdisplay.php?135-Canoe-Sailing-and-Sailing-Canoes
One of the contributors builds add on parts for canoes professionally at http://www.solwaydory.co.uk/ and has plans for add on floats.

There is a guy who built a 10' boat into a trimaran after making a kayak trimaran. Perhaps you can find it if you search for Kayak trimaran or kayak sailing on this forum or http://forum.woodenboat.com/index.php in the design sections.

The real problem seems to me to be adding the high load points to the plastic kayak where the mast sits, and the crossarms attach, and where you attach a rudder and the main sheet for the sail. Plastic kayaks just are not designed for high load points. I had seen one guy run a strap underneath the boat so that clamping down the crossarms spread the load over the whole bottom.

13' is too small for more than one person. The weights you are talking about will sink the boat almost completely, then each little wave will roll over the top and fill up the boat.
Any small boat can be overwhelmed in bad weather, lots of good examples above. It would not be just your kayak trimaran in trouble, but in your inexperience don't you think you might have problems breaking the boat in rough weather? Nothing I do the first time works as I thought.

Check out the Drifter series of trimarans by Mark Grumprecht at http://www.duckworksbbs.com/ProductDetails.asp?ProductCode=mg-Drifter-12L-download I believe your list of tools would almost be good enough to make this boat. If I was building it I would increase the size of the crossarms a little for heavy weather.

Good luck, if I find the 10' boat again I'll provide the link. Actually I found it: http://forum.woodenboat.com/showthread.php?153256-Converting-N-Schade-Great-Auk-to-Sailing-Kayak look down a little ways.
Have you just googled Kayak sailing or kayak trimaran?

 

Your statement of requirements is a bit odd. I don't see 3 mile range for one person in open warm ocean being unreasonable capability of your SOT kayak with a reasonable amount of skill, care and safety equipment. It was all the stuff you were adding (engine, gas, ill conceived appendages and holes +extra bodies) that make an accident waiting to happen.

What skill, care and safety equipment do you need? I will refer you to your local Coast Guard, and the British Canoe Union training and materials (they actively pursue safe kayaking in pretty ridiculous conditions). BCU has skill level guidelines for various conditions and ranges. You can discuss how appropriate these are with the CG when you file your first float plan.

What you should be adding to PFD, appropriate clothing (whatever that is for a SOT) and first aid kit are a day's worth of water stowed low in two separate containers and or a RO watermaker (everything rough weather accessible and redundant backup where possible), a waterproof VHF with weather radio, a waterproof smart phone (GPS & radar weather is a lifesaver), flares, waterproof GPS, a compass, a bilge pump mounted so you can pump out without opening the hull to waves, a chart with currents and tide schedule, spare paddle, tether, and I would rig an emergency cover out of a solar blanket (in Miami heat stroke is as likely as hypothermia) and drogue so I could lay down under it. An EPIRB might be problematic since your boat is so wet in normal operation -maybe consider a SPOT. With this equipment and some skill you should be safe to distances you can paddle in one maybe two hours in fair conditions (but refer to GC and BCU guidelines). With a good sail you might reach the Bahamas.

 

If you are interested in open water capable kayak sail conversions (like I am) look at watertribe.org everglades challenge. Very similar conditions to yours and a 300+ mile race to show strengths and weaknesses.

 

Take a look at this sailing rig. They show it mounted on a plastic kayak. I actually looks good for something without outriggers.

Perhaps you can figure out how to mount a sailrig on your boat

http://www.topkayaker.net/Articles/SurfSail/kayaksailor.html

 

a partner and I built an 18 ft, two man, skin-on-frame sailing trimaran in 9 hours using a cordless drill, a hand held jig saw, a staple gun and scissors (to cut the fabric skin), a few bungee cords and a hand saw, and paint rollers. that includes making the sails, masts and rigging from scratch materials. Total materials cost was about $100 all purchased from a big box store. It was part of a contest, we won the race but came in second place in total points because we took longer to build it than most of the other teams. The total weight of the tools used was about 6 lbs (part of the score).

It does not take a lot of fancy tools or costly equipment to build a decent performing boat.

 

As far as payload, your center hull (the kayak) should be large enough to displace the expected payload at a reasonable, safe sinkage. The added stability of a trimaran comes from what's left of the floats ABOVE the waterline in the upright condition. Sink them and there's no reserve bouyancy to compensate for an overturning force.

Having said that, a kayak or canoe made more stable with floats is a wonderful thing. If sailing isn't a big part of your agenda, floats the size shown in your trimaran images are overkill. Our BOSS stability kit, however, would be a near ideal solution. Please take a look here: http://www.bsdsails.com/boss.html, and contact me if you're interested.

 

Their work here is done - great decision.

Everything they said is spot on, and may save a few lives.

Its a well known fact that boats shrink the further from the building shed they get. In the garage, the boat looks like an ocean liner. Once in the water, it has shrunk by 50%. 200 Meters off the beach with an offshore wind, it has shrunk to the size of a deckchair. 1 kilometre off the shore, with small waves, tired paddle arms and adverse winds for a small sail, it has shrunk to the size of a plastic bucket, and feels about as safe.

The trick is not to build a boat with your wallet.

You need to state on 'paper' the operating conditions you expect to encounter, then get advice on the hull specs to cope. Once you have a clear picture of a solution, then you worry about increasing the size of your wallet.

 

I've become a canoe advocate because I have friends and kids and want to take them with me. Popular as kayaks have become, they have their limitations. Canoes do to, but they can be partially decked or enclosed with a skirt tight to the paddler's waist and/or made into a sailing trimaran just as a kayak can. Stay light but go big!

 

Don't let the small (and extremely negative) minds get you down. I own a Hobie Tandem Island. There is a giant community of people who use their AIs and TIs to do exactly what you wish to do. OF COURSE, you need to be extremely careful, but that is patently obvious. I'm new to boatdesign.net, but I've been surprised by how much posturing takes place in these forums. I'm routinely shocked to see members treat questions as if they were posed by idiots. The minority but prevelant attitude is distasteful, uncivil and downright small minded. Routinely relpiers take a superior, condescending and sarcastic attitude. Feel free to "slag" me.

Addressing the question. Take a good look at the Hobie Tandem Island and try to replicate it as close as possible. Again, people routinely use this craft in big water. Safety first, but an ocean going kayak with outriggers can be fairly stable. My TI is over ten feet wide and 18.5 feet long. It's center of gravity is about 3 inches off the water even with the twenty foot sail. Of course the ocean is a dangerous place. But the couch is just as dangerous and much more boring.

Stay strong in the face of the small and mean.

 

Lonepine;

it is not that his concept was not viable, it was that he wanted to use a rotation molded 13 foot sit-on-top kayak to do it. and to make it large enough to carry two people, this is just not a good starting point for such a craft. He should pursue it, but to either scale it back or start with something more suited.

I had encouraged him to do it, but to keep it simple, small sail and for solo use only near shore or inland waters. that would have be reasonable and safe, and would have given him some good experience to build something more suitable later. Trying to make it into something it is not suitable for is not doing him any favors, he will end up ruining a perfectly good sit-on-top and have something that will not sail well at all, and he will likely abandon it. Not to mention waste a lot of time and materials.

An 18.5 hull length as you have, designed as a trimaran, is a completely different hull than a plastic 13 SOT more suited to fair weather lakes and swimming pools.

The native skin-on-frame kayak builders made seaworthy cargo hauling kayaks and traveled long distances in arctic seas with their kayaks. They were built with "found" materials washed on shore with very minimal tools (an adz, a knife, and awl or hole punch). With just a few inexpensive hand held power tools we can replicate their craft for less than $100 in materials, even less if salvage lumber and other materials. this is a good place to start if you want to make a sailing trimaran, at least you have a seaworthy craft to start out with. If it was built to be a trimaran from the beginning it would be easy to adapt the traditional kayak hull into a great center hull, made strong enough for the sails and outriggers, and the ourtriggers would be inexpensive and light to make in the same way. Yes it will take more time to build, but it will be a purpose built, and need not be costly to make.

there are some on this forum that are materials snobs and will always recommend expensive materials and costly construction methods. I think for a first time build this is unnecessary and perfectly good boats that will give several seasons of safe and enjoyable use can be made with stuff purchased from the big box stores, if chosen carefully and the design is suitable for low cost materials. It can be done, and it need not be costly or time consuming.

There is one way to build a small sailboat with his 13 ft sit-on-top, get two of them and make a 13' catamaran. It will than safely carry two. It will not perform very well, but it will not sink either.

I do not see how your advise would help him make his 13 ft SOT kayak viable as a powered two person sailing trimaran either.

 

The advice given on these pages is good advice. Unless there are conditions which I've overlooked such as being able to disassemble and carry on foot for a distance or being able to cartop the main hull on a small vehicle, a larger main hull would be a better starting point.

The SOR of two adults, an outboard motor, cooler, gas, miscellaneous gear, crossbeams, and possibly a sail for 3-4 mile offshore use will overburden a 13' sit on top kayak hull. The PVC amas will be dragging lower in the water and it will be less than ideal in reserve and comfort, in my opinion.

Selling the current 13' hull or trading for a larger hull would be a better starting point.