Kite Powered Land Proa

Inspired largely by this Instructable, here is my rough, quick and dirty attempt at building a sailing beach toy.

Step 1: Frame

The photos explain this fairly well. Some scrap Pinus Crapiata and 9mm exterior plywood make up the basic frame. I assembled these parts using self drive wood screws, a couple of roofing screws and some horrible, sticky, black polyurethane adhesive.

When you build yours, either go with a triangular structure or the same Tee shaped frame I have done, but with hollow box beams of larger section than I have used here or just better timber. While this frame seems adequate for my weight and mild conditions, the torsional stiffness of both the longitudinal and lateral members is slightly lacking. It is mildly disconcerting to have your seat twisting around as you sail along. I reckon probably the best way to go for most people would be a triangular structure welded up from steel RHS.

Step 2: Leeward Forks

This is the complicated part. The most important aspect of this part is the pivots where the forks attach to the frame. These have to take loads both from the weight of the frame and rider, but more importantly, the significant side loads produced by the kite. The vertical section with the tillers at the top sould ideally be in the same vertical plane as the pivot axes, but mine were a little bit off and it hasn't been a problem so far.

I built my forks from scrap 20x20mm galvanised RHS. A couple of extra pieces got drilled and welded on to the forks to take the pivot bolts. The uprights that the tillers are attached to need to be a comfortable length, depending on your size and the geometry of your seating arrangement. For axles, I simply welded some pieces of ø16mm steel bar into notches cut into the ends of the forks. This was simple but means the wheels are not easily removable.

I got lucky and found some steel bushes in my junk box. I welded these to some pieces of RHS, which I had drilled to allow bolting to the frame. Pretty rough, but good enough.

To make use of the way the wheels and bearings were designed, ideally I should have arranged things so the tops of the forks were inclined to windward.

The flexible linkage between the two tillers is a piece of ø25mm PVC electrical conduit I had lying around. It's about the right stiffness.

Step 3: Windward End

Here we have the windward wheel and the frame where a small polypropylene school chair is mounted. This is the standard steel frame from the chair with the legs chopped off. Its held on with tie wire at the front and welded to the fork at the rear.

The fork is pretty simple, just some more 20x20mm RHS with some little notched plates for the axle to sit in. This axle was threaded like a bike wheel so attachment was pretty easy.

Step 4: Go Sailing

Thats about it. So far I've only had the proa out twice, both times using a pretty horrible kite. Its a 2.4² metre NPW5, made from stretchy, porous fabric, bridled with stretchy line and flown on Dacron flying lines. Still, I was able to get upwind slowly. Besides, when the wind is straight onshore it's reaches all the way anyway.

A few things I've discovered:
-Using these wheels on this sand in these wind conditions, I found after a while that I could steer very adequately just by moving my arms fore and aft. This makes one of the leeward wheels slide more than the other but it's easy to control how much. It feels sort of like steering a large windsurfer.

-Making radical carving turns to windward is fine, it feels like the whole thing just pivots around your body. In the other direction however, all your weight is on the outside of the turn and it is surprisingly easy to flip the whole thing over with painful results. I heartily recommend the use of helmets, wrist pads, protective footwear, kneepads and any other safety gear that seems appropriate. It's easy to go dangerously fast and sand is hard.

Comments

[The nerdling]

10000\5 awesome

[teslafan100]

cool 5/5 im try to make one :)

[TSC]

Cool!!!!!!!!!!!!!!

[AngusNotSoYoung]

Where do you find a kite big enough to pull it and how much does it cost?

[kd1uc]

There are probably more than 100 kites you can buy over the counter to power such a rig, however, many are not cheap. To list a few Quadrafoil, Flexifoil, Revolution and others I cannot think of right now. You would be surprised how small of a kite you need if the wind is right but a six to eight foot wing span has quite a bit of pull. I go sand-surfing with a 6 foot Quadrafoil in a 12 MPH breeze. Into The Wind kite company is one source but look around, you might do better.

[AngusNotSoYoung]

thanks

[Leon Close]

I sewed the kite myself, it's really easy and fairly cheap if you have a sewing machine. A decent set of lines is the expensive part. Search for nasawing or NPW or NPW5 or NPW9 for instructions. The kite I used here is actually pretty small, only 2.4m^2.

[your dog]

 could u use paracord?

[Leon Close]

Not sure, I've never used paracord. If it's polyester braid then possibly, but the strength of it is probably overkill for kites like this. That makes it heavy and draggy, which means the kite won't fly well. Most people prefer the lightweight and low-strech fibres like spectra and dyneema.

[AlexTheGreat]

you should make a kite propelled air cushion vehicle.

[ak49er]

It would only go down wind. It needs wheels to move cross wind.

[BorisTheSpider]

Wonder if you could use a single (or a row, like from in-line skates) wheel on a caster in the middle of the underside. It wouldn't technically be riding solely on the air cushion, but it would allow better steering (including cutting cross-wind) and I assume only the purists would take offense.

[maxpower49]

how big of a kite do u use

[The BeastSpawn]

OMG i would LOVE to make one, maybe I will. I wud make mine of alluminium I have everywhere, then I would do jumpys. I dont have a kite tho... That wud be so kwl. Im gonna start designin right away.

[Leon Close]

Definately do it, you'll be glad you did. But have a go at making a kite, it's not that hard. Try a nasawing for your first kite, probably about 3 square metres.

[BobertXXL]

how fast does it go

[Tool Using Animal]

I'd love to see an NPW construction tutorial.

[Leon Close]

Good idea, though that's pretty well covered elsewhere. Search for "nasawing" and "npwbill" for some good info.

[Tool Using Animal]

Actually, in the last three days, I've read myself to death on the subject, and downloaded all the programs. when I've finished my wifes bookcases, a smallish npw9 is my next "big" project. Def. "big" have to buy something. "small" all the parts are in my junk box.

[Leon Close]

Sounds good. I have a 4.3 metre NPW9 on the go at the moment. All my others have been npw5 so it should be interesting to see the difference.

[wombat7]

cool

[theRIAA]

whats you longest/fastest run?

[Leon Close]

Dunno exactly, no speedo on this thing yet. I'd guess I didn't get much past about 25km/h but I had a clear reach for over 800 metres which was nice.

[Wade Tarzia]

Definitely neat. I was once published a science story whose end featured land proas (though I didn't know they were proas way back then), and I've been fascinated with land proas ever since. So wheels that size will go through hard sand, OK, good, but do they dig in and capsize you in the soft sand, should you be blown onto soft sand unavoidably, or should you need to veer away from romantic walking couples?

[Leon Close]

The wheels are pretty marginal really. They're fine on hard, wet sand but bog down quickly if I leave the narrow strip near the water. It's just going to stop in really soft sand rather than capsize. Bigger wheels would help but I wonder how far this can go? A more efficient kite would be useful to provide a bit more vertical lift to get past soft spots. As far as romantic walking couples go, the best plan would be to see them coming a long way off and land or park the kite. Kite lines are by far the most dangerous part of this setup to bystanders.

[PetervG]

Neat