Introduction: One Day Ndrua

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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.

If you haven't already done so, I highly recommend you use the "view all steps on one page" function.

Step 1: Idea Generation Phase

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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

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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.

Step 3: Add More Sticks

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Keep tying on more stuff until things are a bit rigid and there's somewhere to sit. I made some mats out of palm fronds as well, bamboo poles aren't very comfortable.

Step 4: Rigging

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I had a nice piece of bamboo for a mast but a windsurfer mast or aluminium tube would have been better. The point where the diagonal braces cross looked about right for a mast step.

Step 5: Painting

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I had a half dried up can of acrylic house paint with the following properties:

-Fast drying time
-Water clean up
-Poor adhesion to most surfaces
-Low water resistance
-Delightful nautical grey shade
-In my shed

All in all, perfect for a one day ndrua.

Step 6: Put It Back Together

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Everthing was lashed back together and I added a few extra bits and pieces to attach sailing stuff to.

Step 7: Sailmaking

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For simplicity we decided to go with a shunting staysail rig, however there are many other optionsoptions for a shunting craft.

Basically I bought a cheap tarp and cut in some slightly rounded edges to give it some camber. I folded these edges over and taped them with low quality duct tape to create a sleeve for the luff/leech wires to run in.
I had some stainless steel wire around which I used to make the mast stays and the luff/leech wires.

Step 8: Float Test

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It may seem ridiculous, but the whole time I we spent working on this boat we were not completely sure that the little hulls would have enough bouyancy to float a person. As you can see, the ndrua definately floats, but not by a huge margin. You had to be very careful to keep your weight centred over the hulls evenly so as to not submerge a hull or pair of bows. Due to this fact and all the bamboo everywhere paddling the craft was fairly awkward.

Step 9: Sailing Trial

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Up went the mast and the sail was hoisted (yes I even had a halyard). Unfortunately the wind was very light and I couldn't get the sail to fill properly. Nonetheless, I slowly made it across the river on a close reach, fluked a shunt and made it back again, this time on a broad reach. Due to the massive influence of shifting my own weight, I didn't need to use a paddle to steer.

Step 10: Rig Modification

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It may have been partly due to the lack of wind, but I never could get the loose footed sail to set properly. A long stickish object was laced onto the foot of the sail which improved things considerably.

This is about as far as experimentation ever went with the One Day Ndrua. The boat was just too small and difficult to sail to be very good for anything much, but it was still heaps of fun. More boatbuilding Instructables are on the way.


surftechnologist (author)2013-01-15

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.

b1scff34 (author)2009-05-31

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,

woofboy111 (author)2008-04-17

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...

HoodedRanger (author)woofboy1112009-05-15

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.

CrispFlows (author)woofboy1112009-05-14

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)woofboy1112008-04-18

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.

Jaycub (author)2009-05-14

How do you make the hulls?

Leon Close (author)Jaycub2009-05-15

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.

tdem (author)2008-10-12

Just curious, does this boat sail upwind very well?

XEFrontier05 (author)2008-07-19

Nice work. How do you build the hulls?

meddler (author)2006-12-13

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 Tarzia (author)2006-12-21

All right! Further proas on Instructables! Nice minimalist design! Great palm weaving in homage to native technology!

leevonk (author)2006-12-13

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)leevonk2006-12-13

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.

leevonk (author)Leon Close2006-12-14

good idea, thank you very much

Jacob S. (author)2006-12-13

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!

TimAnderson (author)2006-12-13

Nice project! Good location to be doing it in too!

Leon Close (author)TimAnderson2006-12-13

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)2006-12-13

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.

chuckr44 (author)2006-12-13

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.

pinski1 (author)2006-12-13

It does seem to be very low in the water, possibly fine for lakes and the like, but not for seas.

meddler (author)2006-12-13

I wonder how the boyancy would be affected if you stuffed the hulls with styrofoam??

Leon Close (author)meddler2006-12-13

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 (author)theRIAA2006-12-13

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.

sumguysr (author)2006-12-13

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.

meddler (author)2006-12-13

sorry, pontoon

IdahoDavid (author)2006-12-13

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.

admanrocks (author)2006-12-13

That is Awesome!

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