Reversing a balanced lug rig

Two balanced lug rigged barges lost in an experiment.
Don't worry, they were very cheap models.
I was testing if the standard looking balanced lug sail would be more efficient if set up backwards to act as a vectoring airflow chute, with the longer luff forward gathering wind, and the shorter leech rearward, concentrating and directing airflow, and the yard pointing upwards forward. It was a thought experiment gone practical. Or impractical?
A jib and a lateen both do essentially the same thing, with a long luff collecting, and a shorter leech releasing / directing wind.

Boating Public Service Announcement:
Wear UV protection when on the water. I have time to mess about with model boats due to recently having a pterygium removal operation on an eye, and not being able to work, or go sailing. It involves taking an eyeball skin graft, cutting away UV damaged eyeball skin, and stitching the graft patch over the damaged part. It's hard to explain the pain and discomfort of stitches scraping under your eyelid for a week or two. Believe me it's not fun. This is after about 60 years of water based fun without UV protection. Be Warned. Makes me wonder how the ancient mariners fared after a lifetime at sea, if they survived.
Back to the experiment.

Starting in my sophisticated engineering workshop (my kitchen) with 2 identical sardine tins from the same company, used as donor hulls; two lid colours - yellow, and blue - for one lot in oil, and one in water - (they all tasted the same); standard rectangular hulls with radiused corners, almost vertical sides and ends, with flat bottoms, except for the slight ribs factory pressed into the aluminium hulls for added strength for stacking/transport. Identical length fat plastic straws for the masts, super glued vertical to the hulls bottoms at about 1/4 WLL from bows. Some of you may recognise their origin, a burger supplier. Super glue (cyano-acrylate) turns white when cured in water. No rudders, but identical extra long lee boards glued in the same positions on the windward sides, (not exactly 'Lee' boards then), acting as keels, straight ahead rudders, and as slight counter balances; cut identically from one lid panel, and straightened out the same.

Low aspect sails were cut, identical in area and shape from thin card, 200 gsm, and bent oppositely to get the difference I was testing for; 70mm foot lengths; luff / leech - 60mm / 90mm; 90 deg tacks and clews; Both were affixed to the masts 20mm back from the luff, with the same boom angles, same sail curvatures, and both the clews lodged at the gunnels. Sails affixed identically with identical amounts of white plasticine, (I couldn't find the blu-tack, and super glue was getting awkward). No additional ballast or buoyancy was installed, they were just simple open small sardine tins with no modifications except those described above. I'm sure some nit pickers may find slight differences between the two boats in the photos, but they are extremely minor differences. I did most of the work using one eye, so not a bad effort I thought. Not advertising anything here.



Taken to a local large-ish artificial lake near Port Adelaide, Australia, a special hole dug in the coastal mud and filled with sea water, with overpriced housing surrounding it, for people with too much money. The lake is only good for canoes due to low bridges, and power boat bans; it has some small sandy beach sections bounded by rocky or concrete edging, and it harbours many deadly Blue Ringed octopi. I wasn't going swimming.

Small ripples 2 inches high max crossed the water from a light breeze against a fetch of about 50m, and the boats were released at the same time, and at the same angle, just clear of some small rocks (which I was standing on), with the wind on their stbd quarters. I was hoping for them to be blown along the sandy shoreline, racing each other, to be retrieved when they grounded on the sand where the lake edge angle came around in a curve to the right hand side.
I shall call the 'normal' balanced lug sail configuration, boat 'A', with its yellow gunnel highlights; and the reverse configuration boat 'B', with its blue gunnel highlights. Blue = backwards!

On release from the slightly lee shore, Boat 'A' immediately took off at 45 deg to the shoreline, and about 45 deg to the wind direction, and headed diagonally across the lake maintaining approx 45 degrees from then on, at a seemingly steady speed, (hard to tell from a distance). Retrieval of it from this side of the lake seemed unlikely.
Boat 'B' with the bigger balance forward sail, and smaller leech, followed the shoreline for a few seconds, got hooked up by a small rock and some weed for a few seconds, self released, and then found its natural angle of making way about 15 deg less than boat 'A', sailing about 30 deg to the shore, seeming to go a tiny bit faster than 'A'. It then maintained this angle of making way from then on, and should have grounded eventually, given some side slip. Maybe the 'vectoring' made an improvement to velocity; or was it the different apparent wind angle making it slightly faster; or the hull's angle to the waves? And maybe the larger area forward of the mast reduced the wind cock effect, giving more sail balance across the mast, thus causing the difference in direction of making way, and thus the apparent wind angle. Differences noted, but not definitively accounted for.

Since it seemed that boat 'A' would hit the other shore before boat 'B' landed, I walked around to the other side of the lake, and waited on the beach for it to land. Noting that 'B' had made up for its delay, and seemed to have traveled further and quicker than 'A' through the same breeze and same very small waves. Boat 'A' got to about 20 metres away from the windward shore, and then suddenly disappeared (sunk apparently), and so as my plans changed and I aimed to collect boat 'B' when it grounded, it also disappeared, within a few seconds of boat 'A'. They both must have caught a small gust which overwhelmed them, and they became submarines. No ducks were in their vicinity when they went missing. Prior to that, they both rode the waves, and bobbed, and waggled in similar fashion, as you would expect a flat bottomed barge to do on waves.



No harm done, except for my guilt at polluting a (already well polluted) lake with small amounts of aluminium, plastic, plasticine, super glue, and cardboard.

Conclusions:
0) Inconclusive so far, but interesting and fun.
1) there was no radically different behaviour between the two sails; they both performed about the same apart from angle to the wind.
2) the reverse balanced lug boat 'B' may have been slightly faster due to the vectoring; or due to the wind angle; or due to other local influences unseen, eg. tidal flow variations, (the lake slightly drains to the sea at low tide).
3) boat 'B' may have been more directional to the 'keel' due to less of a wind cock affect.
4) model building should be improved by adding buoyancy to increase chances of capture and re-use / re-test.
5) I need to repeat the experiment after eating bigger sardines from bigger tins.

Before my experiment I did a search, and found no mention of tests regarding the efficiency of orientation of lug sails and their yard's vertical angles, with my vectoring concentrating air flow idea in mind. If anyone knows of any related studies, please let me know.

Another experiment is being planned, after another supermarket visit. Intending to try larger hulls, including expanded polystyrene foam buoyancy, taller masts, more acutely angled yards on balanced lug sails, maybe a little ballast, and maybe an extra boat for wider testing parameters, and more test samples.
Just purchased 3 tins of herring fillets; testing to be continued after a minor feast.

 

Interesting, a worthwhile endeavor IMO, though Reynold number scaling effects are an issue. Decades ago slightly larger test models were retrieved by letting them go trailing some very lightweight fishing line from an inexpensive rod and reel. I've made some small models testing different bladeless paddle wheels more recently which satisfied my curiosity re the approach (not viable).

Next would be a horizonal fin drive but there are too many little projects ahead of it at the moment.

Hulls are hotwired from XPS foam, I've been faithful to my oath to never again use beaded foam except for a diversion to wingsails a few years ago.

 

A noble experiment Seasquirt. I have also participated in homespun engineering, I confess. Bathtub testing and later a long wooden "test tank" in my back yard. A while back I was at a local lake "testing" some small RC skiffs that I had built. A man approached and asked if I was in my second childhood. I replied; Yes I am, and enjoying it thoroughly.

I suspect that a wooden plank might be a more practical boat than the sardine tins. A one by six board about 14 inches long (25 mm x 140 mm x 350 mm +/-) would be cheap and not likely to sink. Also easier to attach the parts for sailing. If you lose interest in the project you could give the boats an honorable Viking Burial.

Your advice about UV protection for ones eyes is damn good advice. I have some Macular Degeneration that is being treated periodically by jabbing a hypodermic needle into my eyeball. Not as miserable a thing as you are enduring but not at all pleasant. I suspect that my condition may have been influenced by a lifetime of Messing about in boats.........without eye protection.

 

As for the reversed lug rig, there are some statistical tid bits that could lead us astray. It is known that the center of lift for an airfoil is normally forward of mid chord. depending on the foil, I am told that the CL is often something like 33 to 40 percent of the chord aft of the leading edge. So if that point on a sail is wider, has more area, than the traditional rig, then will the sum of the lifts be greater? Other than that reach of theory, are there any other reasons to contemplate backward rigs?

Another area for tinkering, could be the use of "turbulators". Some sailplanes use a simple spanwise bump near the leading edge of the wing. The bump can be something as simple as a rope glued spanwise to the skin of the wing. Has anyone experimented with any such gadget for a jib or main ?????? I will suspect that that notion has been debunked for sails.

 

Once the centre of lift is determined on the sail, it could be aligned with the mast, or keel, by using the parrels, and the rig become well balanced, until a direction change of anything happened.

I suspect that the traditional forward dipping balanced lug rig (not dipping lug), is the easiest to tack through the wind, from all other possible attitudes of the yard, including square / horizontal. It was developed over a long time by practical testing at sea while fishing and trading, and would not have endured if it was less useful than other methods and materials. Why ? Knowing the poor tacking behaviour of my plywood boats under a balanced lug rig, a thickly planked well loaded lugger likely wouldn't get enough speed up to get about through the eye of the wind with a larger sail area forward of the mast, and would likely need to gybe instead, which isn't efficient. The under slung rudders of the time wouldn't have helped, virtually putting the brakes on and pulling the stern down when turning hard. In the races out to the fishing grounds, then back to market places quickly, all round speed and safety and ease would have been the winner. Otherwise they could have stuck with a viking rig.

I have made 3 new boats to test, slightly bigger - herring cans, but similar, made sails: forwards, backwards, and square; but storms and rain has prevented me from testing them so far. I'll update here when testing is complete.

A whole new department of sail measurers would be needed if people started sewing ropes to sails for aerodynamic enhancement; another can of worms; red flags. Maybe get away with having strategically placed rougher creased or fuzzy panels and smoother panels, like shining half a ball to get spin. I'm sure the latest broadacre sails used on huge racing yachts have some tricky textile combinations that are not common knowledge.

 

The hull of the boat has a profound effect on the tacking ability of the boat. Difficult or slow tacking problems are not to be blamed on the sail exclusively. A bow down stance will cause sluggish tacking among other things. In the case of a dinghy, the boat pivots, to some extent, around the board. The aft end and the front end of the boat have to swing around the board all the while sailing a small quarter circle. Bury either end of the boat too far and tacking will be sluggish. The amount of draft the boat has is another determinant of course.

It would be well to consider all that stuff when experimenting with herring tin boats or other floating objects. To be sure the positioning of the sail is key to tacking efficiency. A rig with a lot of helm is a misery to tack. The stronger the wind the worse the difficulty. As you do not intend to tack the herring tins, none of that other stuff matters as much.

The sail layout does make a significant difference in the behavior of the boat. My 16 foot flattie skiff will snap tack when rigged with the sprit boom rig that I usually use. Sometimes I use a lateen sail that interchanges conveniently with the sprit boom sail. The lateen pulls the boat as well as the sprit, but it does not tack nearly as quickly and it is not as close winded as the sprit. For whatever reason the Lateen is noticeably faster than the sprit on a dead downwind run.

One of my friends, also a member here, is a competitive sailor in the all class category at regattas. He is an enthusiastic proponent of the lug rig on his 14 foot dinghies.. He is an accomplished sailor and he uses the lug rig to put pressure on some very good boats such as Finns, RS Aeros and others of that sort.

 

My herring minor feast (imagined above), was much smaller than I thought it would be, since the cans were mostly full of sauce and not much actual fish. I like to use fish cans due to the consistency of size, shape, and surface finishes, being mass produced in their thousands or millions, they are almost identical. I select dent free ones and am careful not to distort them during my workings on them. I avoid calling them tins, since there is no tin involved these days.

This batch of cans have radiused ends, double ended, with a slight bottom rise at both ends, maybe more boat like this time, smaller WLL to beam ratio, but that shouldn't make any difference to the testing since the hulls are all identical again. 150mm LOA, 82mm beam, 25mm high gunnels, 41mm bow / stern radii, almost vertical sides and ends, approx 2mm chine radius - all around. Not sure of their weights, prob 10 - 15 gramme each, rigged.

Bought some new blu-tack. Visited several stores looking for big diameter plastic thickshake straws to make lightweight masts out of, and finding only useless paper straws, which are no good in a wet environment for very long, thanks ocean dumping polluting countries. I then went to a hardware store and got long plastic in ground irrigation risers, after going through heaps to find the straightest ones. Heavier, thicker wall thickness, and smaller O.D. to the previous straws, but they'll do. Trimmed them to identical lengths, minus their plastic pipe piercing ends.

Found some closed cell foam in my stores, and cut hull sized foam fillers, with a hole for the mast, so now they won't sink forever, and will bob up from a swamping, allowing for more extreme conditions in testing. Cut the straightened lids accurately down the middle and glued a half on each side of the boats, making them twin keelers, not quite bilge keelers but more like twin leeboards, so at least one will be in the lee on each hull. All positioned as identically as I could. Again with no rudders, just keels extending rearward for straight ahead directions.

Masts 225mm tall, maybe a bit too high an aspect, fitted over a button shaped wider plastic base, and glued to the inside bottom of hulls, at approx 1/3 of WLL back from the bows, (back 52mm from bows), at a convenient spot within the metal pressings, with super glue. Mast bend direction was found, and all marked for same orientation on assembly. Glued with the bend giving rearward rake of a couple of degrees or thereabouts, adjusted to be very close to the same angles. They were later cut back in height to 150mm above the gunnels to avoid excessive heel, and the high possibility of capsize in a small gust. With no ballast, they wouldn't be self righting.

Cut 2 sails 180mm high peak; 100mm luff; 100mm foot;
and a single rectangular sail 150mm by 100mm for comparison; all tacks and clews at 90 degrees.
Rectangular sail: 100x150 = 15000 square mm
Balanced lug sails: 100x100 = 10000, + (100x80/2 = 4000); total 14000 square mm
Made of the same 200 GSM card as the previous sails were.
I realise that the cardboard luffs aren't pulled down straight as in a real boat's rig, affecting the test results to some extent, but the card sail I use doesn't stretch like fabric, making a compromise necessary due to the materials used. I don't want to spend time stitching micro sails, which would introduce too many variables, and be a PITA. All sails had mast attachment positions marked 30mm back from the luffs.

The card sail's mast attachment sites were hardened with super glue on both sides, and rings of blu-tack were used wrapped around the masts near deck / gunnel level, and at mast heights in positions holding the sails where they all seemed to have the same foot height and curvature. Adjusted by eye, not exactly scientific. Clews were affixed to the gunnels.


New test subjects; Released, rectangular in the lead.
Sails were spray painted for easy identification: red = reversed; yellow = rectangular; green = normal balanced lug sail. Shot glasses seen in first pic were a serving suggestion only; used to balance boats on the hard.

Testing: Released the boats together again, at the same lake as last time, from almost the same location, and sent the boats out at the same angle as previously - 45 deg to the shore line. Previously the wind was about westerly; this time it was north westerly, and a bit less strength, with smaller waves.

The rectangular sail seemed to do better than the others for a while, before it capsized and turned upside down; it had had slightly more surface area than the other sails, and just got unlucky with a small gust, seen by video. The other two boats stayed upright and under way for nearly an hour, before the backwards sail turned turtle close to the shore, too far away from me to see why; and the normal balanced lug sailed to shore some time later, still sailing intact.

Observed results: reversed balanced lug sail again seemed to be faster than the normal, but was sailing at an angle more off the wind to the 'normal' one, so a different comparison. Normal balanced lug sail made way closer to the wind but was slower making way; it was the only one to stay upright throughout, which is a positive. Rectangular sail worked well at the start, but was maybe overpowering the un-ballasted boat. The added buoyancy enabled recovery of all boats, eventually. I think the centre of effort of the sails was too far forward of the lateral resistance, (keels), so they all bore away from the wind more than desired. Future modifications anticipated.


Rectangular capsizes; Reversed leads, then capsizes; Normal balanced lug survives the ordeal.

Conclusions:
1) reversed balanced lug sail seems to be faster in a straight line, again; with the wind on its beam quarter.
2) normal balanced lug sail seems to sail closer to the wind, again; with the wind on its beam.
3) rectangular balanced lug sail initially beat the other two in speed, before capsizing quite soon.
4) mast heights and sail areas need to be reduced on these hulls.
5) it was fun.

I plan to further reduce the mast heights and sail areas, and make all sails exactly the same area for the next tests. Also attaching the sails more securely, so they can take a beating from bigger wind and waves. And place buoyancy at the mast tops to avoid turtling.

One negative to the reversed balanced lug idea, is that it may hinder tacking through the wind, which can not be tested for in my very basic rudderless models.

 

Same 3 boats as previously made (see above), but a re-do:
Cut the masts 40 mm shorter, now 110mm above the gunnels.
Reduced the sail area for all sails, also making them equal in area: Yellow rectangular sail 100mm foot x 110mm luff / leech = 11000 square mm; Red, and Green angled yard sails 100mm foot X 150mm high peak X 70mm; 100 x 70 = 7000 + (100x80/2 = 4000) = 11000 square mm.

The round foam plugs cut out of the closed cell foam for the masts' access to the hull bottoms, was attached to the mast tops, to prevent them from easily turning completely upside down when capsized. Sails were lowered closer to the 'decks', "sweeping the decks", and attached giving them all approximately the same sail curvatures. All clews attached at the gunnels giving the same boom angle. Red's float was glued on top of its mast due to the sail's height, other floats were impaled on the masts - a minor difference.

Testing, I didn't publish many photos since they look almost the same as before, just a bit shorter.
Same small lake, lower tidal level, light winds from the southwest, and 1 inch waves at max, with the western side of the lake having smooth glassy areas of wind shadow, from lakeside housing. Some occasional minor wind swirling.

Released from the eastern bank, they just grounded continually, so I went to the west bank and released them together in an easterly direction. They hung together for a while before splitting up, and then changing directions due to wind shifts. They started off traveling easterly directly to the opposite shore, then headed south for a few minutes, before going south easterly. The normal balanced lug did the most southerly, sailing closer to the wind, and finally went easterly long after the others had landed on the lee shore and had been collected.

Red reversed sail took off and went further quicker than the other two. Yellow square sail was a bit slower than red, but followed in similar directions. Green normal sail went slow and steady, and was last to land on the other side of the lake by a big margin, but it did go the furthest up wind, probably due to the wind cock affect again.


Shortened masts; Getting going; Quarter way across

There were no capsizes to test the mast top floats, (a bit disappointing), so the lower aspect sails had made them all more stable.
Reversed balanced lug sails seem consistently to travel furthest in a set time, and reach the far shore first, leaving the other sails behind. They can also have high speed bursts when compared to the other sails. I can see a pattern developing.

Next tests I'll leave the sails as is, and mess with the keels I think, to see if green can catch up to red and yellow, with less wind cock affect.

 

Test 4, with same 3 boats again:
Made deeper narrower lee boards out of the removed starboard lee boards, found estimated centre of resistance of them, found estimated centre of effort of all sails, and aligned the lee boards glued back on the starboard sides so both 'centres' should be optimally aligned, (estimated). I probably did it wrong, since I did no research, and used very basic geometry to position the centre boards opposite the sails' centres of effort; as shown by the photos.

Back to the same lake, and in similar conditions as previously, north west light breeze pushing one inch or less wave height from a 50m fetch, later swinging to south westerly, helping to blow the boats back to the same eastern shore as they were released from.
On release the reversed sail and square sail functioned well and sailed off as expected, but the normal sail had issues, getting up to speed then tacking through the eye of the wind, getting back winded on the wrong side of the sail, and circling a 360, doing this a few times in its journey, making way slowly, sailing too close to the wind, and stalling a bit. All the lee boards and rudder sections were set dead ahead similarly, so the new board placement must have been the cause.

Red backwards sail went faster and further again, yellow square sail was not far behind, and normal balanced lug took an extra hour to reach the shore, making way slowly, doing a few 360's, and sailing backwards a few times; clearly not optimal.


Finding centres; Boards in place; Red backwards sail wins again!

I think I'm done with testing the models, and will look at trialing a backwards balanced lug sail on my 10 foot dinghy for real world experimentation. It may be difficult to do, as the sail will need a tight long luff to keep shape, (I kept the leech strength minimal for smooth air flow), and a sheeting rope block attached to the other end of the boom; some minor mucking around and experimentation needed there. Also my reefing system probably won't work when reversed.

 

Test 5 on a real boat:
A 10 foot long sailing dinghy I am very familiar with, with a smallish area balanced lug sail I made, arranged backwards; fairly simple thing to do on a simple rig.
First issue: the mast needs to be taller, since now hoisting the sail by a higher up section of the yard. I had to hoist as high as possible, then set the sail on the boom at second reef at the new long luff / throat, and on the first reef at the new shorter leech, so the boom didn't drag across the decks and gunnels. Setting it so the sail had a decent shape, with maximum possible area available, although a somewhat small surface area anyway, being already reefed. The sail hoisted up ok, and looked ok, despite being the wrong way around. Some boom cleats and other outhaul hardware were now against the mast, restricting some movements and adjustments, but this is a temporary test, so not a big issue for now. The main sheet boom end pulley was moved to the boom's new back end, and seemed to work ok, in no wind.

Next day tested the sail's handing at Garden Island, winds NE - N, 10 - 12 knots, gusting to 16 Kn, swirling, and back winding off the land and over the mangroves. It worked best on a port tack with the sail backing on to the mast, and not so good on stbd tack (the supposed 'good tack'). It was definitely faster on port tack, and faster than regular orientated sail. It sailed quite close to the wind on port tack, with the sail backing against the mast, and was stable in stable winds; stbd tack not as close to the wind, but still slightly better than the regular orientation sail. Going down wind it was the same as the regular orientation sail.
I'd call it the 'Greater Than' rig, (>), since the luff length is greater than the leech length.

The big down side was that in blustery back winding conditions it was an unstable test of human speed and wits, and had the boat lurching from side to side erratically and with force. Fun if you like to be on the edge, and ready to get wet, I wasn't.

After about an hour of testing on both tacks at all angles to the wind, I swapped the rig back to regular orientation and sailed more for comparison. It was definitely slower on both tacks now, but stable, safe, predictable, and controllable; much fewer panics.

The reversed balanced lug rig as I tested it, with about 1/4 - 1/5 of the sail area forward of the mast, (see picture), would work best in light steady winds needing long tacks, and having less chances of back winding or blustery gusts. I also think it would probably work better with much less of the sail forward of the mast, greatly reducing the unpredictability in changing winds, - needing a taller mast and a Gunter style yard support, and maybe an end parrel or gooseneck on the forward end of the yard, like a bermudan boom. That's another project and test for another day. The weather forecast was for sunny 20 deg. C, but after midday, cloud and cold made sailing less fun, and I packed it up, having tested it reversed, and comparison tested using it in normal configuration; also tested it normal with a small jib on the bow sprit, which worked well for long tacks.



A new cut of sail may be more optimal, like an isoscelese trapezoid, with the yard having less angle down to the rear, and with the boom having more angle up to the rear, so the exit stream is directed more horizontally rearward, and less sail 'balance' forward of the mast. As it is now, it is directed angled down, giving the hull some actual vertical lift; I may need to tether the mast down, (joking).
I have proven it works, in nice conditions, and am sure a race between the two orientations would see the reversed sail win, in nice conditions.
In bad conditions, some bad words may be used by the master.
I haven't done any calculations, or used any laboratory equipment, only empirical testing in a real world environment, (with a GPS), to get my results; and it was fun.

 

The fish tins are a novel way to simulate a boat. But they are awful in terms of drag. For that reason, it will be difficult to asses small differences in sail efficiency or sail thrust. Carving a few pieces of wood into a more hydtrodynamicaly friendly shape would probably reveal more about the sail rig than the tin cans can reveal.