Instructables
This Instructable documents how my girlfriend and I built a sailing ndrua in one day. A ndrua could very arguably be described as a double-hulled sailing canoe which has hulls of unequal length, the leeward hull being marginally more voluminous. The craft shunts rather than tacks and gybes, so some people will call it a proa. I don't bother with these names much and call it a boat instead.

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Step 1: Idea Generation Phase

This step is made easier if you have a few half finished long term projects lying around as I do. The smaller hull here is from a now deceased 4.2 metre proa I built in 2003. The other one was intended to be used for my 6.8 metre current proa project but I wasn't happy with its design for this purpose so it too was available.

I saw these two hulls lying beside each other and half jokingly thought that they could be lashed together to create a ridiculous sailing craft of some sort.

Basically if you have some ingredients similar to these (unlikely), sit them a nautical distance apart and lay some sticks between them. Now you have the choice of either convincing anyone who is around that this idea could work, or just ignoring the laughter and getting on with it.

Step 2: Let the lashing begin

This step involves what is probably the best combination of building materials yet devised my humanity. Of course I am speaking of seasoned bamboo and discarded bicycle inner tubes.

This fantastic system allowed us to quickly get the crossbeam and deck structure worked out to rough dimensions, while the flexibility and ease of adjustment allowed for fine tuning. The structure we came up with is fairly simple and the photos explain it well enough. Anything with reasonably substantial crossbeams between the hulls and a bit of diagonal bracing would probably work.
Brilliant! Thanks for sharing. Old sailboards make good pontoons, too. If they are the 9 ft fiberglass variety they are also easy to attach stuff to. If they are the larger plastic hulls you can just strap some crossbeam hardware to them with $10 car-top tiedown straps from Walmart. I run the straps all the way under the sailboard hulls and ignore the minor drag created by the strap against the hull. Works great at non-planing speeds. I'll post an instructable about it someday.
b1scff345 years ago
Enjoyed the experience with you through your pictures! I made a sail for a 1' canoe in 1976 and we sailed in the St Lawerance Que many times and never went over. Thanks for your fun,
woofboy1116 years ago
Do you have any more details on weaving the palm frond seat? I don't know, but when I've tried to make stuff out of palm fronds, after a few months when the water all evaporates out of the leaves, they become very brittle and tend to crumble...
you could instead use leather thats been soaked in water to weave with, then when it dries it will be nice and tight from shrinking. just an idea, i forget the name of the leather that works good for this tho. i saw this method on "How It's Made", they were making a canoe, so im guessing its water-worthy.
I'm just guessing here but I think you need to seal the leaves before weaving or most especially when the project is done... The leaves become brittle and dry simply because it does dry out. When it's sealed by laquer or something, There's no place for the moisture to go and it remains locked in. But, as I said - It's a guess.
Leon Close (author)  woofboy1116 years ago
I've had the same experience. I just don't think they're ever going to last very long, it's the nature of the material.
Jaycub5 years ago
How do you make the hulls?
Leon Close (author)  Jaycub5 years ago
Standard amatuer boat-building techniques. They're thin cheap plywood, epoxy resin and some fibreglass. Look up "stitch and glue" boatbuilding for a description of the project.
tdem5 years ago
Just curious, does this boat sail upwind very well?
Nice work. How do you build the hulls?
meddler7 years ago
So if i wanted to make a pomtoon with buckets stuffd with styrofoam it woulden't float or bear weight?
What was meant is that it wouldn't bear any MORE weight than the same buckets, sealed and full of only air.
Wade Tarzia7 years ago
All right! Further proas on Instructables! Nice minimalist design! Great palm weaving in homage to native technology!
leevonk7 years ago
so the mast is just lashed with an inner tube at the X junction and then held straight by three wires? How strong a wind can that stand? (I'm not being critical, just curious)
Leon Close (author)  leevonk7 years ago
It's not just lashed on, I attached a forked stick to the base of the mast and this holds the base in position over the x juntion. This is the same basic concept used by most sailing craft, other than those with freestanding masts. The boat would definately capsize before anything to do with the mast broke.
good idea, thank you very much
Jacob S.7 years ago
you're my hero!!! I went sailing in the Bahamas last summer and it had to be the greatest experience of my life, I've been absolutely obsessed with the Idea of building my own boat (even a small one like yours) but the practicality of a boat for me, if expressed on a scale from one to ten, would be a negative number, I envy you for being able to do something like this. Great job!
TimAnderson7 years ago
Nice project! Good location to be doing it in too!
Leon Close (author)  TimAnderson7 years ago
Why don't you sail your Piver over and check it out? The river I sail in seems to have an abundance of strange multihulls. Just yesterday I wantched the second "Harry" model HarryproaHarryproa having its mast stepped from the verandah of our little sailing club. There's a beautiful Wharram Tanenui for sale in the area as well.
Leon Close (author) 7 years ago
By the way, the bamboo you see growing in some of the photos is not what I use for boatbuilding. That species is very pretty while it is alive but does not grow particularly straight and has very thick walls. I have to go a bit further afield to get the bamboo I use for spars. I think it is called "moso" and is a vigorous runner, as opposed to a clumping variety. The culms grow very straight and without many side branches. Many are in excess of 20 metres tall, with only slight taper along this length. These pictures show the grove where I cut bamboo from, and the small supply I have at home, now seasoned for over 2 years with no cracking at all. These few pieces are destined to be spars for my unfinished 6.8 metre proa project, assuming I decide on a crab-claw rig.
Moso.jpgseasoning.jpg
chuckr447 years ago
IdahoDavid, There are some bamboos that will survive -20F winters. I just got some, 2 clumps of one kind from the internet, and a free clump of another kind from a friend. But they will not get much bigger than 1 inch diameter (or arond 20 feet high). Do a search on the internet for "bamboo" and "-20F" and see what pops up. Expect to pay $20-30us per clump plus shipping.
pinski17 years ago
It does seem to be very low in the water, possibly fine for lakes and the like, but not for seas.
meddler7 years ago
I wonder how the boyancy would be affected if you stuffed the hulls with styrofoam??
Leon Close (author)  meddler7 years ago
Wouldn't make a difference, bouyancy is determined by volume and weight, i.e density. The air in the hulls is considerably less dense than foam.
well, actually, it would make a difference, as you said, foam is denser, so the hulls would actually sink deeper. Now you could use contact cement to skin the outside of the hulls with "blue foam" (whatever that stuff at the big ox stores is properly called), and that will increase the bouyancy.
....and increase the drag
leevonk theRIAA7 years ago
I think there are certain paints you could use to reduce drag. Painted blue foam ('bluecore') is used to make homemade RC airplanes. I'm not sure how well the paint does in water though.
sumguysr7 years ago
foam would make very little if any difference to the craft. The reason foam is used in some boats and rowboats is incase the boat springs a leak or otherwise is filled with water it will continue to float as the air that is trapped in the styrofoam can not be displaced by water at normal pressure.
meddler7 years ago
sorry, pontoon
IdahoDavid7 years ago
Great food for thought. I envy your access to bamboo. Up here in the northern climes the closest thing we have is Schedule 40 PVC. Willow works for some applications. Looking forward to more boatbuilding ideas.
admanrocks7 years ago
That is Awesome!
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