Trying to design a homemade catamaran..

[cavalier mk2]

Hi Richard, I sail on the sea and the canoe rig passed all sorts of blue salt water tests, beyond expectations in fact. The lake reference is for Alex who is in South Africa pondering trying out ideas on inland waters (I hope) first. If people didn't test some ideas affordably they might waste money when it comes to the real thing. I do advocate safety which is why the canoe in question can be easily righted etc....My winter testing was done wearing an immersion suit. If they sink how can they upgrade to your plans

[Richard Woods]

So we agree then. Try out ideas on a lake first, where you can always drift to land when things go wrong

And I suspect you are a more experienced sailor than Alex

Richard Woods of Woods Designs

www.sailingcatamarans.com

[KSONeill]

Originally Posted by Alex.A

Hi - also building a cheap/small test bed cat.... looking for cheap alternative ropes/sheets/stays etc - non "marine" ie from the local hardware store?
Also cheap sail material - see a lot of people using polytarp - is it ok and are there any other alternatives?
For 14' cheapie.

Look for lines and used hardware on ebay. I've bought rope from Milwaukee Rigging:

http://stores.ebay.com/Milwaukee-Rigging

and from Discount Rope and Line:

http://stores.ebay.com/Discount-Rope-and-Line

Both are good quality stuff, honest and very cheap by West Marine standards.

For blocks and so on, just troll through the used offerings looking for something that will work for you. You can also look at Duckworks:

http://www.duckworksbbs.com/hardware.htm

for simple low cost hardware. Not as light as used Harken stuff off ebay, but still pretty good.

I don't use polytarp for a boat that's intended to go over ten knots, it stretches too much and you end up with a bag. Polytarp is fine for a small monohull, but not for a multihull. Look at Baconsails:

http://baconsails.com/sailsearch

You can often get used sails very cheaply. Much better for a year or two than something you make from polytarp that stretches.

K O'N

[junkman]

http://www.polysail.com/lufftie.htm
I haven't looked at lately but they make sails and give instruction on poly sails. Many use darts to shape poly rather than the regular method.
I thought this page to be cool for a test boat. From this page you can click on there home page.
As above Ive herd they are more for cruising around.

[Petros]

I build "test" boats from lumber yard materials all the time. They are cheap and fun to build. Any exterior grade plywood works just fine, I have even used the very rough CDX in 3/8" thickness, though 1/4" AC plywood is better (costs about twice as much). They last from 2 to 4 years of regular usage, and either I rebuild it or salvage the parts for another project.

The best cheap sail material I have found is Tyvek house wrap, it can be sewn or taped with two sided duck tape (cheaper than the Tyvek tape, which also works). The blue tarps also work, cheap too, but they are not very durable. There is a nice filament reinforced white tarp material I want to try out too, it is much heavier and more durable than the blue tarp, and cost more too.

I often gather up left over materials from a construction site, or where they are tearing down old buildings.

I have also built real inexpensive skin-on-frame kayaks and sailboats, search the internet for good sites for information on SOF construction. The last one I built took about 14.5 hours for two people to build a 17' 2-man kayak. All of the frame materials was build from a 16' 2x8 and a one 4x8 sheet of plywood, and about 6 yards of polyester fabric to cover it. I have been wanting to build a small catamaran using this building method.

Most of the small boats I build cost well under $100 in materials, sometimes next to nothing if i can salvage the materials from trash or construction sites.

BTW, here are some free plans for a pretty decent looking catamaran you can build with all lumber yard materials (no fiberglass!). I think it would be better than what you were thinking about. I would not mind building it myself, it is based on the Hobi 16.

http://www.svensons.com/boat/?p=SailBoats/Hobby_Kat

have fun with it, just get started building and do not get hung up on using expensive marine materials. Use the lumber yard stuff, latex paint, Tightbond III glue, etc. for your first few projects. Once you get good building boats than you can move up to the better quality materials.

[junkman]

Petros Will Tyvek house wrap, Just looked at the DuPont site and they use same material to cover cars boat etc(not house wrap stuff). Would it last very longer , longer than tarp ?
found a little info here
http://www.messing-about.com/weekender/sails.html

[Alex.A]

Dont worry guys - i have a dam/lake 10km away and have a wetsuit and lifejacket etc etc. Lived by sea for 20 yrs and am a good swimmer .
Have built wood houses and am bout to build another... but not a boat - but hopefully sinking/falling apart wont hppen
The hulls will be sealed on top with plenty bouyancy - have done my math!
Just want to test hull shape, crab claw rig and a few non standard idea's for feasibility - without spending too much.
Thanks for the replies.
May even post some pics - if its not too embarressing .

[upchurchmr]

Alex,

No one has responded about hull shape. I suggest almost anything but triagular hulls. Look at Richard Woods hulls for Pixie. At least make a square box and put triagular shapes under. Multihulls need a good bit of freeboar because they sink under sail load. generally you have to pay close attention to where you sit, to keep from sticking the nose under water and making a great show of yourself - when you fly thru the air since the boat stopped before you did. It is also possible to go over backward, and sideways - don't make the boat too narrow. A full 8 feet wide is a good start for the catamaran.

Best bet is to go watch some local beach cats sail, and talk to the guys when they come in.

Marc

[nimblemotors]

indeed, unless of course you just want to build something.
what about building a concrete boat? I have some epoxy garage floor paint, will that seal it up?

Originally Posted by redreuben

Buy a second hand one !