This is the story of the Sail Bike, a tandem sailing bicycle. Built with limited resources and time, it actually worked pretty well, and gave me a few ideas on how to improve it next time. It was a lot of fun to sail, and also a lot of fun to bike. Got a lot of great feed back from interested people at burning man. Sailing it by myself at dusk across the open playa, was like being on a martian desert, and one of the most incredible experiences of my life.
Note: I have included hotlinks to definitions to words the layman might not know, if you see a highlighted word/link.
What was the sail bike?
Two cheap beach cruisers bolted to a custom metal frame. Steering linked with ackerman steering.
A rotating windsurfing mast mounted between them. A dinghy jib cut down and used as the loose footed roller furling main sail.
Why make the sail bike?
For years i had been to burning man and wanted to sail across the desert. As an avid sailor, the freedom and expansiveness of the playa as well as the constant wind made for great conditions. At one point last year i sat down and drew a sketchup of what i thought it might look like, and actually pretty much stuck with that vision. I had a much bigger much more time consuming project going this last year for the burn and built the sail bike as almost an after thought, so i didn't put as much time or energy or resources as i would have liked, but it turned out pretty well regardless. I actually built a good percentage of the project actually on the playa in the dark with an angle grinder and a little 110 mig.
How did it work?
My goals were to be able to sail on a broad reach, and bike anywhere I wanted, if it could go upwind that would be awesome, but I wasn't holding my breath. Mostly I was hoping for any sort of "sail assist". In the end, it would go to weather pretty well, could fly a "hull" both upwind and down, and generally hauled ass. Flying a hull down wind was incredible, as i could go lower and faster, the more the apparent wind came forward.
With two people I had to reef the sail half way so my friends could keep up on regular bikes on a reach. I was very happy with the performance. The brakes built into the bikes, as well as just general boat handling kept it safe, and it actually felt very stable while flying a hull. If you're familiar with catamaran sailing then you know the feeling of playing the main and tiller to keep it flying. I would absolutely build another and improve on this design, it was so much fun.
A note on Burning man regulations regarding sail craft.
Some people might be wondering about Burning man regulations regarding sail vehicles, and how mine fit in to those rules. Lets just say that I saw and talked to hundreds of police and Black Rock Rangers and interested burners, and not a single person even hinted that they thought it might not be safe or allowed at the burn. I did my utmost to sail it safely, and took the responsibility of being an ambassador of sailing very seriously. I would love to see more sailing vehicles on the playa, and I think as long as they are piloted safely and responsibly it would be a match made in heaven.
Ok on to the tech!
Step 1: Material List and Design Philosophy
60'x 3/4" steel square tube
20'x 3/4" steel round tube
20'x 5/8" line for main sheet
20'x 1/4" line for down haul and traveler
jam cleat for down haul
corresponding misc blocks and cleats for main sheet and traveler
Wind surfing mast and universal mast step
old sail (i used the jib from an I14 and cut it down)
hose clamps for mast step and hardware for bolting cleats to frame
3/4" closed cell insulation foam strips for protecting the frame and reducing vibration.
optional piece of pvc for mast step
bolts and nylock nuts for steering arm
Ubolts for attaching the frame to the bike frames.
I chose to use traditional bicycles because I wanted to have the normal "bike" experience, in hindsight, a recumbent bike probably would have been a better choice as it would have lowered the center of gravity and gained clearance for the sail, but I think the recognition factor for normal bikes was little higher and more fun looking. I simply prefer to ride a normal bike as well.
Another reason i used normal bikes instead, was i wanted to try and reduce the material cost and welding time, by keeping the bikes intact and making the frame removable. Well, i ended up welding a relatively elaborate frame anyway, and while the bikes were indeed removable, i Think a custom recumbent frame would have been just as easy to do, Oh well you live and you learn!
So i went with 2x beach cruisers. I got them from target, they were about 100$ which is a little expensive, but they were nice, reliable, and it made it easier when both bike are identical.
The wind surfing mast was because I wanted the mast to rotate and the sail to furl. If i had used a fixed mast i would have had to have a jib or asymmetrical spinnaker rotating on a forestay like a traditional boat, but i thought that would put the center of effort too far forward and make it difficult to go upwind. So I opted for the main sail, and the rotating non-stayed mast. The windsurfing gear was the cheapest (free) and easiest solution I could find and ended up being pretty strong.
On to construction!
Step 2: Welding the Frame
First thing i did was get my lady to sit on the bike so i could get an idea of where the mast would start and how much clearence was needed for the sail, and how far apart to put the bikes. I figured that the sail should start 3 feet up from the stem to mostly clear the riders head, and that 4 feet apart was good enough to not be to wide, but to provide good righting moment.
Next i decided i wanted the bikes to be removable from the frame, as much to save space in transportation and storage, as incase it failed miserably and wanted to use the bikes separately!
The rider's legs and pedaling action dictated where the cross beams would go, so i put them at the top of the steerer tube, just down and back on the down tube, at the seat post, and eventually on the chain stay. This gave the bike lots of lateral support, something i was very thankful for when i started to fly a hull!
So the first thing i did was cut a piece of the square tubing to about 4' and then welded the flat washers from the ubolts to the outsides of the tubing.
Then i bolted the single beam to both bikes, made sure the bikes were straight and vertical, measured another place and repeated the process. By working as fast as i could and just eyeballing it it actually came out pretty straight.
Then i sort of willy nilly reinforced by eyeballing and compound cutting more tubing to stick between the beams, taking care not to obstruct the riders legs.
Next mast step!
Step 3: Mast Step
I figured since the mast step could rotate and bend, i would bolt it down at the bottom, but them also need some way of keeping it pointed upright. I resolved to fix this problem by welding a vertical bar above the mast step and deciding to use a pvc tube to fit the mast through. I figured id hose clamp the tube to the frame. More on this later...
Step 4: Cut the Sail
I didn't really know how i was going to hold the sail out yet, but i didn't have time to worry about that stuff... :)
I did know how much space i had to have from the bottom of the mast to the top of the riders head, by measuring from the base of the mast step, so i used that by un rolling the sail and physically putting the mast on it to mark where to cut and sew.
I ended up having a huge bag in the foot, more on that later.
Basically i thought 5 feet back from the mast would be plenty of sail, so combined with the max mast height i could work with, i pretty much just cut and folded the sail and sewed it over into a sleeve in such a way that i thought i would have a flat sail.
Next steering and working at burning man!
Step 5: Steering and Working at Burning Man
I eventually did find a welder and I had an angle grinder I used to cut, and made it happen. it was certainly not idea conditions and made the compound cuts pretty difficult, but it worked out.
The steering was pretty straight forward, just Ackerman steering system. Basically you draw a line from the stem back to the center of the rear axle and extend that out forward then connect them. Ive attached a diagram i made from an earlier instructable that had six wheels, but the same principal applies here.
I used some rubber sheeting strips in between the steering posts and beam and bolts which worked really well. the steering was right on the money and felt great.
I also used nylock washers through-out the build to minimize loss through vibration.
Next was sail control!
Step 6: Sail Control
So i was going to need a relatively wide angle for the sail. If i had a single point in the middle, the sail would have to twist out to work and it wouldn't be as effective. So i realized i needed a traveler to pull the sail out to the side.
I ended up welding these long arms reaching out backwards and a fixed circular tube between them to act as the traveler. The clew would have a block on it, and another compound block on a carabiner would slide along the traveler bar. Then id have a line that would let me manually move the traveler from side to side, or set it at the middle for upwind wen you want a flat sail.
This was absolutely necessary to the success of the craft, regrettably i didn't do a great job thinking it out, and yet it still worked really well. What happened was i was quickly running out of material welding flux and energy, and without stepping the mast and actually checking against the sail, i decided that i had designed the sail to be pulled 5 feet out, and a certain height above the riders head. So I figured i could just mount the bar where that point was and id be fine.
Well it turned out that the bar was too far forward, and too low, so when it pulled the sail out going upwind, there was a large bag in the foot. Meaning it pulled tighter along the leech then the foot, so the top of the sail was relatively flat but the bottom wasn't. this isnt the best sail shape for going upwind, but for a broad reach it was fine.
Since the traveler bar was straight as well, when i pulled the sail out to the edge of the traveler, it actually pulled it a little flatter since it had more distance to go.
Good things that worked were the continuous traveler, kept the lines clean and nothing in the wheels, also worked really well on the fly, so i could position the traveler nicely. The main sheet cleat was really nice as well. i tied the end of the main sheet into a basket and let the tail fall into there, which kept the only two lines clean and out of the wheels.
As the week went on I ended up fixing the sail shape which really improved upwind performance more on that later...
Step 7: Furling!
I also hadn't given the system a whole lot of thought, but figured id make it up as i went a long, which is pretty much what happened.
I figured I'd mount a pvc tube to the fram to keep the mast upright, and let it rotate, but unfortunately in my last min search for material, I could only find a tube that was the exact same size as the mast at the bottom (since it tapered) so i was a little SOL as there are no hardware stores on the playa!
So i ended up cutting the pvc pipe to try and just protect the mast from the frame and using hose clamps to keep it upright against the vertical part of the frame.
I then mounted a jam cleat to the mast and attached a downhaul line to the tack in order not only hold the sail down but to give it some purchase to rotate around.
There ended up being really the perfect amount of friction in the system to let me rotate the sail with one hand while riding, letting me furl and unfurl easily, yet also it would hold in its postion and not rotate on its own. So no line was ever needed to secure the rotation.
Later as the PVC started to get out of position, then actually fell off while night sailing, i just put some rubber against the frame and used hose claps alone. which also worked pretty well.
Next Disaster! De-masting and happy coincidences...
Step 8: Disaster! De-masting and Happy Coincidences...
This turned out to be a good thing though.
I remounted the mast, now a little shorter, moved the down haul jam cleat on to the frame, (which meant i had to remove the down haul to furl, oh well) and immediately saw that the clew was in a much better position relative to the traveler bar. It let me pull it flatter which gave me much better sail shape and allowed me to go upwind much better as well. Good stuff!
Next wrap up...
Step 9: Wrap Up
Sailing it out on the desert at dust across the empty open playa was life changing. Sailing at night with my lady and friends in tow from party to party, was incredible. Biking with out the sail was also really fun, and it made a great ice hauler.
I highly recommend building one.
Hoep you enjoyed my instruct able see you on the playa!
video coming soon.