Bionic Broomstick
A preliminary report on yesterday’s splash of the Broomstick with wingsail. Trip to Lake Somerville was non event val, stopped to retie blocks holding wingsail on trailer a few miles into the trip. Got to the lake and signed in at the ranger station and met John coming in as I was leaving. Only damage on the trip up was losing one of the pins that hold rudder assemblies up while trailering and the top flap section was flapping loose since the joint between the foam core and the connector to the center flap section had failed. A little gorilla tape got things reconnected.
Lake level is still fairly high and the nice little beach area we normally used is under water and its a wade through the grass to get a boat launched. Boat goes together pretty quickly and we are about ready to launch when Kevin shows up with his sailing canoe, good to have a rescue boat just in case. Weather is hot, really hot even for old Texas hands. A little cloudy which is nice but careful observation of clouds show that they aren’t moving which isn’t so nice there is virtually no wind and what does stir seems to come from any direction.
Still it is into the water. Not much to tell in drifting conditions. I hadn’t checked the rudders which have been up for a while and one doesn’t want to go down. So I drift in both Pacific and Atlantic mode and discover that the boat paddles fairly well with a forward draw stroke which is fine but would be an asymmetrical killer for a long haul. Paddle also works much better being carried on the hull rather than behind me on the beam, just not flexible enough to comfortably and quickly retrieve and store the paddle.
After drifting around and observing things in the infrequent puffs, one thing becomes clear. Mal was right, mass balancing is important, at least in light conditions. The wingsail isn’t perfectly vertical, a combination of the beam no longer completely seating in the socket (wood in the beam has swelled a bit) and the boat is biased a little to windward (this was by design, the idea that normally the pressure on the sail, or wing sail, would balance things out about level). So the wing is tilted maybe 3-4 degrees to windward and the counterbalance weight isn’t quite heavy enough to balance things out. In these uberlight conditions gravity trumps wind pressure. It’s obvious when you kinda guess where the wing would be and manually twist it around the boat “leaps” (ha) forward. Seriously you can tell the difference. One adjustment made during the drifting sessions was to increase the throw on the flap actuator, considered increasing the elevator throw but that would entail risk of losing some very little bits.
After a couple of drifting sessions and the more productive sitting in the shade and jawing the wind actually picked up to about 5 mph and came more consistently out of the East. Back to the water. Boat actually works pretty well in these conditions, shunted through close to 90 degrees, Kevin said there was a wind shift involved and he’s probably right but the GPS track (will post later) looks nice. Out on both tacks I decide to go back and get my camera. Going downwind seems to work best manually holding the wing out at 90 degrees and we get back to shore. After talking to John for a couple of minutes I go back to head out to Kevin in his canoe. The curent method of getting onboard is to hop up to a sitting position on the hull then on to knees and then crawl into seat. A puff of wind blows the boat back towards the weeds while I’m in the middle of transitioning to my knees and I try to hurry the process too much and tear the tripod mounts off the hull, failure in the plywood deck its self.
Done for the day, John helps me get the sail down without more damage.
Will post more and video links, GPS track later, need to get back to work.
Cheers,
Skip
One quick video
http://youtu.be/KW6bZ7ruJWw
Here’s Kevin’s video of our adventure, haven’t really seen it myself, internet connection at office has gone buggy.
Also posted here is screen shot of GPS track, we went out clockwise only about 0.62 miles total, 1.9 mph moving average speed, 3.1 mph max, in about 5 mph max winds(?!).
What’s next, repair torn tripod base, finish mass balancing wing, consider some sort of fold down stirrup arrangement or other way to expedite getting on the dang thing. Clean up some of the trailering details. I plan on spending enough time getting comfortable with the rig to take it to Sail Oklahoma in October with the idea that someone younger and a bit more limber might want to take it home, though it might also make the Port Aransas small boat festival the next week.
Bottom line I’m getting comfortable with the idea that the wingsail is a viable power source for proas. I think it’s a no brainer in the mid section of wind speeds. With a little stiffer structure I’m pretty comfortable with the idea that I can endure some on shore gale type conditions at least as well as a more conventional rig. In the very lightest of conditions we are also a go. This was the whole idea behind the current rig. Yesterday I wasn’t embarrassed to be out with Kevin’s fairly well sorted out sailing canoe. The image of being pinned to the water like a bug on an entomologist sample board on ACDC while PDR’s merrily drifted by me isn’t ever going to go away.
So my emphasis is going to shift to Nomad and we’ll see where things go from here.
Cheers,
Skip
The video is from our first drift-around, with about 0 to 1/2 mph of wind. Once we got a little breeze the boat sailed great, the wing was really impressive. I’d like to put a similar thing on my little tri, but cartopping it looks like it might be destructive.
Thanks for the update, Skip! I would love to see some footage of it moving along. Do you have any other tests planned?
It seems like the weakness of the wing is in it not feathering when it should. What’s your plan for bringing crusing reliability to what you’ve achieved on BB?
I’m excited to see the next iteration on Nomad.
chris
Thanks for the update, Skip! I would love to see some footage of it moving along. Do you have any other tests planned?
It seems like the weakness of the wing is in it not feathering when it should. What’s your plan for bringing crusing reliability to what you’ve achieved on BB?
I’m excited to see the next iteration on Nomad.
chris
I would love to provide some footage of it moving along 😉 In the fullness of time…..
Plan is to fix what’s broken, come up with a way to mount/dismount easier, complete mass balancing the wing, fine tune some of the trailering. then go sailing some more.
Weakness in feathering was really a lack of torsional stiffness, the stabilizer juked back and forth enough in relation to the wing that the cables controlling the stabilizer jumped off the pulleys and the wing went full power on in close to 30 mph wind. Biggest difference in the next iteration is everything will be started from scratch. Instead of a piece of 2” OD questionable thinwall alum for a mast tube it’ll be a 3” OD piece of 6063-t832 fitted into a 3-1/4” piece of the same, far stiffer. Instead of cables there will be a real pushrod link to the stabilizer with real ball joint links. Tail booms will be at least 50% larger in diameter. Wings will be all hotwired foam w/carbon cap spars and mylar skin.
An important detail I think is to have a way to pin the cam follower in neutral, makes trailering easy and makes things “close” to foolproof when it starts to blow like stink.
Designwise I think it’s important to use a fairly conservative tail volume coefficient which means a fairly small chord wing and long tail booms. It will probably be a while before Nomad really gets going but I am looking forward to the deal.
Skip