Does anyone out there have any experance converting two kayaks into a catamaran?

I'm going to Home Depot tomorrow to buy some hardware for the boat, does anybody have any recommendations as to what glue I should buy to laminate the Redwood I'm going to use to make a centerboard and rudder. And while I'm on the subject of the centerboard, what would be the best material to seal the wood from the water?

I inspected the knot in a 4x4 crossbeam more carefully, and I think it is close enough to the edge of the wood that even when I rounded the sharp edges so it will not damage the kayaks there will be sufficient wood to carry the load I expect to put on it.

The 2 x 4's in the photo that I posted, are not the 4x4's I am going to ultimately use. The 4x4's are much heavier, and significantly stronger. I'm actually thinking I may be over building this thing. But better too strong than not strong enough.

Tomorrow I'm buying a spoke shave at Home Depot and shaping up the 4x4's and the mast connection.

I'm not sure exactly how I'm going to connect the windsurfing rig to the kayaks support structure. I have a few different ideas some are very strong, others not as strong but much lighter. One way would be to shape a wooden spar that will just fit inside the carbon fiber mast, this would allow me to have a sail that I could allow to trail directly down wind by simply freeing the sheet. The sail could rotate through 360° quite easily. With the wishbone bloom keeping the sail shape constant and because I am unable to reef the sail this may be my best option. It is definitely the lightest option. But it is also the weakest, because that Spar would only be about 2 inches in diameter and its base I don't think the wind will be blowing much more than 2 inches of wood could handle, but I cannot swear to that.

But if I choose to go for strength I have some other ideas. One of which, using PVC pipe fittings, I could still get treated and 60° rotation of the sail but there would be some unsightly fittings disrupting the airflow right in front of the mast! Maybe I will draw them up and scan them and post them on the web so you can see what I'm planning. Well, that's all for tonight I have some artwork to do.

If anyone can recommend a good adhesive, be it proxy or other, please let me know as soon as possible, as I'm going to Home Depot tomorrow at about one in the afternoon West Coast time.

Thank you in advance, Good night, Amy

 

Epoxy for all underwater joints, definitely. Epoxy is tolerant of joints that are not perfectly fitted as well, because it is gap filling. Other glues that claim to be waterproof are OK above the water, such as PL Premium or Titebond III. Not Titebond II or I, or white glue or other cabinet maker types glues.

I am not sure about mounting the mast, depends how the mast was intended to be mounted; be careful not to damage the carbon tube. A 2" wood stub does not sound adequate. A canoe sail I made long ago had a short length of iron pipe called a nipple http://plumbing.hardwarestore.com/52-331-galvanized-nipples.aspx scewed into a floor flange http://plumbing.hardwarestore.com/52-331-galvanized-floor-flanges.aspx and bolted to a thick ply plate. The nipple should be quite long; I used a 4" nipple but it was only 3/4" pipe so you would want to use a longer one. I wrapped a thin sheet of Aluminum around it to prevent wear on the inside of the mast which was also Aluminum, and to form a reasonable fit as a bearing. It worked very well for a couple of years. All of the above can be had from any hardware store, but you could probably buy the proper part from a boat store, which would be the thing to do for the long run.

 

I have a windsurfing mast for my Ulua outrigger sailing canoe. It is held up by a stub mast and secured to the mast about the windsurfing boom height. For a catamaran, I'd put a regular mast step from your board on your front crossbeam and clip it to your mast extension. To raise the sail, I'd use a pair of lines to the bows of the kayaks like an A cat or the Escape playcat. For the sidestays, I'd bring them back 20 degrees or so on both sides. make sure your attachment pieces are solid as it's easy to rip that plastic without some sort of backing plate. Your main sheet need not be too many parts as the sprit boom makes the sheeting stress pretty low.

Have fun and be safe!

Dan

And yes the sprit boom looks a bit long with the sail reefed.

 

Hi,

last night I made a model of the boat and trying to build. It is a representation of the configuration of wooden blocks supporting the stub mast. These blocks are not to scale. If they were they would be 8" x 8", obviously this would be far too heavy and sink my boat. The true dimensions of the wood used in the boat is 4" x 4".

I chose to make this model with such large timbers because I wanted it to be easily seen in the photographs. Not because I'm stupid. I laid out several different configurations of wooden blocks supporting the stub mast while attempting to avoid excess weight, and still maintaining sufficient strength to keep everything standing in heavy winds should they occur.

After you look at the photographs, if you have any suggestions that may be helpful, please let me know. I wish to maintain sufficient strength to be safe while losing as much excess wood weight as possible. My kayaks can each support between three hundred and 350 pounds. I don't want to use all that up in excess wood. I would like to have some extra flotation remainingf for passengers and supplies.

I look forward to hearing any comments you may have and your suggestions as well. Thank you in advance ..............Amy

 

Catamayak under construction

Hi,

sorry to keep making so many posts but I said I would give you a look at my vision for a Cataraman made from two kayaks, as it occurs. So here is the first photos of the rough lumber laid out in the approximate positions it's going to be used. This gives you a sense of dimension. It looks heavy now, but I'm going to cut it down further and shape these 4x4s into a more appropriate size. I'm currently working on a scale model of this boat and will post pics when ready. I hope this gives an idea of what I'm trying to do. If you have any sage advice warnings or helpful comments, including constructive criticisms, please let me know. Thank you in advance Amy

 

Hi Amy, it would be better to build it up over the beam instead of underneath. As is it will drag in the waves. I also think it is too heavy. Why not look at some of the smaller cat setups at James Wharram's website for ideas? A maststep box of ply and timber reinforcing (think upside down flowerbox) attached to the for and aft timber fitting over the beam would work. Say 3/4" ply for the sides and top and 2x2 framing. It would be more usual to have the fore and aft central timbers on top of the beams so the load isn't just carried by the lashings.

 

Kayamaran

Hy Amy, here is another approach. May be, it is helpful for you.

 

Manfred,thouse rigs look great, but was that rig strong enough? Did you take it out in any high winds? I'm going to be in san fran bay, can easly reach 25mph on these waters, and it gets bumpy!

 

You are right, Amy,

I did not test the rigs on the pics and I have never been sailing in the San Francisco bay. I am living minutes from the coast of the Baltic Sea and have built and sailed a lot of boats (monos and multis) in my life.

From my experience I would choose the lightest possible rig for the two sit on tops as the buoyancy seems to be very limited. Might be you will end up with a raft.

 

Very interesting thread.

I had no idea there were so many people with pairs of canoes or kayaks laying around, begging to be turned into catamarans.

 

Those beams seem pretty massive to me. I would agree with Manfred that you will want the lightest beam system that can do the job. On Slider, my rather heavy 16 foot cat, I use 2X6 beams, and they are plenty strong. On my 14 foot cartop cat, I use ply and timber laminated beams-- still plenty strong, and much lighter than solid timber beams.

 

Don't forget that redwood is a very light wood; it's also somewhat brittle. Given those facts, I think that not only can she get away with using beams that look pretty bulky, she might be safer doing so....

And don't forget this is a prototype, built mostly with found materials to try out some of her ideas.

 

End of the line

Hi guys,

Thank you to you all, for all your help with my kayak catamaran idea. But This boat is dead in the water as of 09/23/2010. That was the lucky day my dear sweet husband realized I ment it when I said I'm going to go sailing again even if it kills me.

So he helped me buy a Hobie Adventure Island trimaran!!!

I have already taken it out for a shake down sail ane I love it! It is as much as I dared to hope for.

But this is it for my catamayak I'm afraid, I have no further need of lt.

Thanks again, you've all been great. Amy

 

amy's new boat!

Hi again,

I just thought you might like to see what killed my catamayak.






www.youtube.com/watch?v=sqYxKTBOs1I

 

I'd say you're design accomplished a lot! Congratulations