16ft,4.8m Catamaran

This spring I'm planning to build a sailing catamaran. It will be 16 feet long 8 feet wide, and the mast will be 30ft long. It'll have a plexiglass hull and bamboo internal structure. It should be pretty light weight.

Draft=six inches
Waterline to transom=1.8ft

Im using hobie 16 sails. I have a concern about the mast. Im not sure what to use. Ive been thinking 4" PVC pipe but i don't know if it will hold. Should i just buy a mast?

Ive included AutoCAD drawings and a rough sketch. I haven't included any hardware on the AutoCAD drawing because I don't have any experience. Im only thirteen and have had no lessons. Please give me feedback and/or tips. Thanks

 

4" PVC pipe will NOT work. Buy a Hobie 16 mast-they're are plenty of them around. Good Luck and have fun with your boat!

 

Thanks. Im sure in strong winds i will greatly appreciate that choice.

 

Plexiglass or Lexan planking for the hulls will be much heavier than more conventional materials. A small cat needs to be as light as you can make it consistent with structural adequacy.

 

From the information its saying it'll only be about 100 pounds per hull

 

I have a hobie wave now thats 250pounds so this should be lighter to proportion

 

Hmmm... let's take a look at your materials, Deppari.

How many sheets of plexiglass or lexan will it take to do each hull? What thickness are you using?

Also, what amount of bamboo?

We can then take a look at the total weight of all that stuff and see how it comes out to see if messabout has it right or not.

I have my own random question: How will you do the joining of the plexiglass to each other? Not saying you can't, just curious.

 

1/8 inch plexiglass. Its 48" by 120". Ill need about 7 total pieces. Im going to screw them into the bamboo. Ill use about 2 to 3 sheets a hull.

 

Yeah, I'm going with Deppari on this one. I came up with 204.4 lbs if he uses 7 sheet of 4' x 10', 1/8" plexiglass. Good work.

Don't forget the frames and mast will add too, probably putting you closer to the Hobie you already have.

http://www.eplastics.com/Plastic/Plastics_Library/Plexiglass-Weight-Per-Square-Foot

I am assuming you are using the .118" stuff, since that's probably what they sell as 1/8" in the store. The actual measurement for 1/8" is .125, but it doesn't come in that size, exactly, according to the link above.

I guess didn't ask my question well enough:

How will you seal the edges of the plexiglass so it is watertight? When you seal one piece to the other? or.... do you plan to bend them around in the shape you need? I'm just very curious.

 

After i screw the plexiglass into the bamboo im using that white sealent i forgot what its called but theres tons of it in home depot. Ill seal everything with that. The bambo is very light so the boat should stay light including the mast.

 

Don't forget to post pictures of the boat building project for us!!

 

Im starting in late febuary, ill start to post then! Thanks for the feedback

 

I don't think you are going to like this boat very much. Drilling and screwing plexiglass is the best possible way to crack the glass. It is also very brittle, once cracked it will continue to crack as you use it.

100# per hull is really heavy. The old Tornado (20' cat) has fiberglass hulls that weight 60# each, and the total boat weighs 235# at minimum class weight. That's comparing a 20'er to your 16'er.

You would be a lot better off buying a Hobie 16 for the mast, sails, and rigging and sailing it first before designing your own just to understand the heavy forces on a cat.

Good Luck

 

Wow--slow ahead here--believe it or not plexi is a little on the brittle side and more so after being subject to any amount of UV attack. The other problem is it's temperature expansion/contraction factor. Ask anyone who has tried to use it with mechanical fasteners.(which you are using) If the fastener hole does not allow for this the plexi will crack like an automotive windshield hit with a stone. The hole has to be some two drill bit sizes greater than the diameter of the fastener and always a good idea to install with a rubber sleave and washer set up. I have a fair amount of experience with this installing frameless windshields and wheel house windows in the motorsailers i build using the stronger less brittle UV resistant Lexan. The other problem is standard house caulking will not bond well with this very smooth surface. A special formulated clear silicone will (fish aquarium glue) do the job but is expensive. I do not want to discourage you from building your own boat but i recommend you don't use this un conventional non boat building product.

 

EDIT: Again I posted this before seeing the two previous posts (which I agree with)

Conventionally you'd home build a 16ft catamaran in 3/16 gaboon ply. That weighs about 15lbs a sheet or 1/2lb/sqft

How do you plan to make the crossbeams? I'd suggest something as stiff as 3in OD aluminium. Certainly not bamboo or pvc pipe. And how will you attach them?

A 30ft mast is pretty long for a 16ft cat. 26ft would be better, less still if you are a lightweight and singlehanding.

I suggest you practise cutting the plexiglass on some scraps first. It's not easy. Use a slow speed jigsaw, if you cut too fast the plastic will melt and rejoin itself.

I guess you won't have any heat expansion problems in New York, but it might be an idea to have a breather in the deck. Lots of plexiglass windows crack when people don't make oversize screw holes.

Having said all that, its going to look great on the water (I assume you will use clear plexiglass). A see through boat. All you need is clear mylar sails and you'll be invisible.

Seriously though, that may not be a good idea, most people want to be seen (at least by their parents). Furthermore a transparent boat isn't very photogenic

Richard Woods of Woods Designs

www.sailingcatamarans.com