Bionic Broomstick
Something about seeing the proa for the trees… 😉
Looks great is an understatement. Looks fantastic! I think we will all be keeping our fingers crossed for Tuesday.
Looks great Skip! Fast work too.
Do you have a counterweight on the wing?
Mal.
No counterweight yet, there’s provision for one at each tailboom but ran out of time and 3/4” alum tubing. I’d be concerned but Tom Speers experience with the landsailer wing leads me to think it will be OK, don’t expect to have near the acceleration issue and shouldn’t heel that much either.
Skip
No counterweight yet, there’s provision for one at each tailboom but ran out of time and 3/4” alum tubing. I’d be concerned but Tom Speers experience with the landsailer wing leads me to think it will be OK, don’t expect to have near the acceleration issue and shouldn’t heel that much either.
Skip
I once saw a model catamaran with a similar style of wing. It didn’t have a counterweight and the sail didn’t work at all well. The reason was that wave motion caused the wing to oscillate wildly. Land yachts don’t have waves to deal with so I can imaging that it’s quite possible to do without a counterweight in that situation. On the other hand, Bionic Broomstick is not a model, the wave motions where you sail may be quite different and possibly negligible, the CG location on your wing may also differ and these things will affect how the wing behaves. But I suspect that in light wind situations on open water you will need a counterweight.
Tom speer made a good point about placing a lighter counterweight higher up the rig, but I imagine that may require a bit of tuning to get it right and may even need to be adjusted for different wave profiles (short chop vs long swells).
In any case I eagerly await your sailing report after your test sail. Exciting stuff.
Mal.
I once saw a model catamaran with a similar style of wing. It didn’t have a counterweight and the sail didn’t work at all well. The reason was that wave motion caused the wing to oscillate wildly. Land yachts don’t have waves to deal with so I can imaging that it’s quite possible to do without a counterweight in that situation. On the other hand, Bionic Broomstick is not a model, the wave motions where you sail may be quite different and possibly negligible, the CG location on your wing may also differ and these things will affect how the wing behaves. But I suspect that in light wind situations on open water you will need a counterweight.
Tom speer made a good point about placing a lighter counterweight higher up the rig, but I imagine that may require a bit of tuning to get it right and may even need to be adjusted for different wave profiles (short chop vs long swells).
In any case I eagerly await your sailing report after your test sail. Exciting stuff.
Mal.
The joy and despair of piddling with proas centers around the lack definitive guidelines. There’s great promise in this minimalist offbeat corner of the universe but most of it hasn’t been realized yet in this society. A lot of that promise was realized long ago in Polynesian societies but with far different materials.
I’m excited about finding some of the contemporary answers. I’m convinced that the end rudders are a viable simple solution for a shunting craft, still some details to develop, haven’t come up with a good solution for maintaining adequate tension in figure 8 style hinge.
It’s not yet been in the water yet but have already learned a lot about wings in this size range. Biggest is that it is would be worth the effort to set up and hot wire the wing, the flap is foam covered with 4 mil mylar drafting film; is the best part of the whole deal. The Scotch “Tough” packing tape is expensive but worth it for hinges, is different than similar Scotch tough duct tape. Aluminum tubing pieces, tail booms and stub mast want to be bigger.
Will know a lot more after some sailing trials, suspect you are right about the counter weight. Tomorrows wind forecast keeps creeping up now 13-15 mph, any more and we may not get wet, in which case it will be a couple of weeks or more before we try again, lots of friend and family commitments on the horizon.
Thanks for the comments and interest.
Skip
What’s the news Skip? Did you sail, or was it too windy?
Mal.
What’s the news Skip? Did you sail, or was it too windy?
Mal.
Too windy to sail, 17-20 mph w/ wind gust 20-27 per nearest wunderground station.
Not too windy to put it together and break something, will get a report out later today when caught up with work.
Skip
Wingsail Report
Tuesday,May 6 was supposed to be least windy day this week, was also supposed to rain later in the week. So arrangements were made to meet John Wright, the only other retired proanut in Texas, at Birch Creek Park on Lake Somerville about 9:00 AM. Susie was going to come up also, leaving an hour or so later than me since she would cover the 88 or so miles quite a bit quicker than me pulling a woobly contraption on a trailer.
We came from opposite directions but John arrived at the Ranger check in just as I was leaving. Birch Creek Park is a pretty good place to trial new sail type craft, besides a couple of boat ramps there is a good beach adjacent and not too far from parking. Prevailing SE summer winds blow pretty much directly onshore. This particular day the winds were more from the SW and stout. John and I agreed that it seemed to be 20 mph gusting to thirty. After the fact the nearest wunderground station recorded winds of 17-20 mph gusting to 20-27 mph for the same time period.
No guts, no glory, but I’m not in this for glory, the Broomstick and I are not going sailing today. But we are here and one of the purported advantages of wing sails is the aero drag is less than bare poles and rigging of a conventional soft sail so reefing or other methods of shortening the rig is unnecessary. let’s see.
With everything rigged with boat on it’s side it’s time to lift boat into the wind. The rig dances around a little bit but the boat stays on its 80 pound or so feet untouched. John and I agree that conventional rig would probably blow over in these conditions under bare poles and definitely with a handkerchief or burgee attached anywhere on the rig.
The wing is dancing around a little bit, John thinks it is because the wind is turbulent coming over a little rise rather than across the water. I suspect it is mainly due to flexibility in the tailbooms and lack of torsional stiffness in the wing. There’s also some flex in the alum tube stub mast.
I walk back up to the car to get my camera to get some video and hear a fairly loud ‘crack’ as I get to the car. I don’t look back but get my camera and take the attached picture.
Postmortem analysis is fairly conclusive that the glue joint between the plastic plug at top of alum tubing stub mast failed and the plug along with top support popped out of mast and that was that. Fortunately Susie did get some video even though she didn’t get the moment of failure.
What’s next? Nothing for a little while, there’s a number of other commitments in the next few weeks followed by some more deferred honeydo’s left over from shoulder rehab. Probably a new foamcore wing covered with 3-4 mil mylar. Either same area or slightly less span/area. Reuse tripod, mast tube, tail and tailboom. Some of these aren’t really optimal but I’m still in search of ghosting efficiency, not likely to seek out any strong winds. Am still debating going to a torque tube/pushrod style mechanism for the cam follower rudder control. It makes a lot of sense but I’m not comfortable making inaccessable bits in down and dirty prototypes. OTOH cable system is prone to stretch even in spectra.
Here’s some videos
The mechanism
At the lake
http://youtu.be/_cBb62Jt5zg
http://youtu.be/sYB8Bnn8Iss
Skip
Coolness! Very impressive stuff, Skip.
Is it me, or does it look like the wing’s bearings are too loose or too close together? It appears to be knocking around, which is probably what produced the impulse that broke it.
That’s the caveat with that whole feathering in the wind thing. Once things start bending or flopping around, its not feathering properly, right?
Huge thanks for sharing your experiments, as always!
chris
Skip:
Really good effort - you are breaking a lot of new ground and those of us in the cheap seats appreciate it.
Interesting that it broke without the boat going over. Either the ama was to the leeward and it was in “Atlantic” mode or there is more here than meets the eye. Since the boat didn’t dry capsize, the drag induced must have been pretty low and the failure/breakage was localized to the area affected.
To bad you didn’t catch the failure on video.
—
Bill S.
Coolness! Very impressive stuff, Skip.
Is it me, or does it look like the wing’s bearings are too loose or too close together? It appears to be knocking around, which is probably what produced the impulse that broke it.
That’s the caveat with that whole feathering in the wind thing. Once things start bending or flopping around, its not feathering properly, right?
Huge thanks for sharing your experiments, as always!
chris
Wing bearings ‘were’ separated by 30” +/- top bearing, a 1” dia plastic ball on top of stub mast fit into a bored hole in a plastic block well secured to wing structure. What broke first was the glue joint between the plastic plug the ball was attached to, plug fit into top of stub mast and should have had a mechanical fastener also.
Feathering into the wind appears to be a lot more viable than I had thought. The problem with my homebrew iteration was general flexibility, primarily tail booms and torsion in the wing proper. Some of the flexibility in the wing was from transport damage to the D tube foam leading edge (area covered w/gorilla tape in videos).
Will know more in the next iteration.
Skip
Skip:
Really good effort - you are breaking a lot of new ground and those of us in the cheap seats appreciate it.
Interesting that it broke without the boat going over. Either the ama was to the leeward and it was in “Atlantic” mode or there is more here than meets the eye. Since the boat didn’t dry capsize, the drag induced must have been pretty low and the failure/breakage was localized to the area affected.
To bad you didn’t catch the failure on video.
—
Bill S.
Failure was local joint event. You’re right drag was surprisingly low, might have been smooth beach sailing if things had been a little stiffer. There was a lot learned, wing was easy to carry even in the high wind but we were really careful to keep it low and trailing edge up wind. I think that adding tail boom and rudder best done after wing mounted on boat, not what I’d originally intended. Also think the scotch extreme packing tape is really tough stuff. The two flaps still attached to the wing flapped back and forth at highway speed all 88 miles coming home and seem fine.
Skip
A shame the day went pear-shaped but we always learn something, don’t we? I would add my support to others—you are doing good science here. Keep it up!
In the rebuild, my general suggestion is not to change very much; rather improve, patch and reuse first, if only to gather more real-time flight data to better inform yourself for the next iteration. Perhaps don’t even think of going sailing; just fix and fly the “old” wing more? I’d ask questions like “how much more torsional stiffness is required?” Could the (lighter) d-wing be improved upon and retained? (over on RC groups they do a lot of foam bending—both hot and cold. You might be surprised at just how tightly they can smoothly roll even very thick foam)
On the other hand, I began with formed and “planked” foam wings, too, then built a wire-cut solid section—and was transformed. So neat, so clean, so ready-to-fly!
Probably a new foamcore wing covered with 3-4 mil mylar. Either same area or slightly less span/area. Reuse tripod, mast tube, tail and tailboom. Some of these aren’t really optimal but I’m still in search of ghosting efficiency, not likely to seek out any strong winds. Am still debating going to a torque tube/pushrod style mechanism for the cam follower rudder control. It makes a lot of sense but I’m not comfortable making inaccessable bits in down and dirty prototypes. OTOH cable system is prone to stretch even in spectra.
Don’t discount bowden wires. They’re low tech and can be low-ish friction—and so easy to route and maintain! The RC guys have plastic versions based on a splined inner “wire” that are very low friction and pretty good sized—(not really “splined” but more like a torx screwdriver cross section. The point is, they only rub on the sheath at the sharp spline ridges—minimal contact surfaces). I bet these could be ginned up in larger sizes from some easy to obtain plastic extrusion and some form of flexible sheath—like the stuff they used to use on pay telephone handset cords (sounds out of the blue, but skydivers sometimes use this as bowden cable sheaths for their ripcords)
Dave
A shame the day went pear-shaped but we always learn something, don’t we? I would add my support to others—you are doing good science here. Keep it up!
In the rebuild, my general suggestion is not to change very much; rather improve, patch and reuse first, if only to gather more real-time flight data to better inform yourself for the next iteration. Perhaps don’t even think of going sailing; just fix and fly the “old” wing more? I’d ask questions like “how much more torsional stiffness is required?” Could the (lighter) d-wing be improved upon and retained? (over on RC groups they do a lot of foam bending—both hot and cold. You might be surprised at just how tightly they can smoothly roll even very thick foam)
On the other hand, I began with formed and “planked” foam wings, too, then built a wire-cut solid section—and was transformed. So neat, so clean, so ready-to-fly!
Don’t discount bowden wires. They’re low tech and can be low-ish friction—and so easy to route and maintain! The RC guys have plastic versions based on a splined inner “wire” that are very low friction and pretty good sized—(not really “splined” but more like a torx screwdriver cross section. The point is, they only rub on the sheath at the sharp spline ridges—minimal contact surfaces). I bet these could be ginned up in larger sizes from some easy to obtain plastic extrusion and some form of flexible sheath—like the stuff they used to use on pay telephone handset cords (sounds out of the blue, but skydivers sometimes use this as bowden cable sheaths for their ripcords)
Dave
Thanks, not sure how scientific it is, more applied tech.
Need more torsional stiffness than I had, a little pre-applied strapping tape might have saved the day.
Bottom line, I think mylar skinned hot wired foam is the answer, first iteration a blend of do it down and dirty plus what was at hand.
A part of the learning is discovering the difference in these size ‘wings’ and R/C stuff, there are similarities but transport and assembly are a little different. I’ve got some of the R/C bowden cable type stuff, used 1/4 scale fittings for some of the linkage but it’s all just a little larger scale than what those guys use.
I’m going to repackage my old variac and order a few bits and continue as time allows.
Cheers,
Skip
As a suggestion for increasing both the torsional and bending stiffness for the wing, you could add a spreader at the top bearing (which could also double as the bearing mount) and run stays out to four points on the wing, I have used this method on a model wing and it works very well. Not as clean as a wing without stays, but adds a lot of stiffness without resorting to exotic materials.
Mal.
As a suggestion for increasing both the torsional and bending stiffness for the wing, you could add a spreader at the top bearing (which could also double as the bearing mount) and run stays out to four points on the wing, I have used this method on a model wing and it works very well. Not as clean as a wing without stays, but adds a lot of stiffness without resorting to exotic materials.
Mal.
Thanks, it looks like your model is better built than my reality 😉
That’s an elegant solution for torsional stiffness that I’d not seen before.
In retrospect there really should have been some diagonal strapping, the heat shrink window film covering I had on hand wasn’t as stiff as the mylar that I’d used years ago.
Foregoing exotic materials does seem proaish, it helps in this case to have a really thick wing section. Current debate is about the stub mast, The current 2"OD section is of questionable quality and pretty thin, no more than .050 wall (damn just realized if I’d have weighed the thing would have been able to calculate the wall thickness).
Replacing current stub with a 2” .083 wall piece wouldn’t be that hard and probably worth the cost. Future iterations will probably start with 3” dia pieces.
Skip