Jump to content

Balanced Rig?


Howard

Recommended Posts

Not to stir the pot or anything, but I had to toss this out for Garry's benefit.  ;D

http://www.garryhoyt.com/id32.html

Ya think two of em would work on a Princess?

Actually, two balanced lugs might work. I think folks have concluded that offset deal isn't that important as far as performance of the sail is concerned.

Just for grins, I would like to try a balanced lug on the Spindrift, except that with the mast forward as it is, the center of effort would be out of whack.

Link to comment
Share on other sites


The fertile mind of Gary Hoyt is at it again.  Hoyt comes up with a novel idea at regular intervals.  Some have caught on and some have not.  This looks like an advance on the usual balanced lug rig, based primarily on the offset idea.  The rest of his ideas on the sail are less interesting or not really new.  I see the hoisting and adjusting as probably more involved than other sails.

The theory about square/elliptical headed sails as being better than pointed headed ones is open to argument. Some soaring/gliding birds take the long pointed wing approach.  Prime example is the albatross which lives on the open ocean and seldom lands except to feed or breed.  The reason is that the long pointed wing requires a less strong wing root structure and less energy and muscle mass to operate it.  The longer- higher aspect wing more than pays in greater lift over the greater efficiency per area factor of the shorter-square tip wing.

**NOTE: Like the albatross which seldom flaps its wings, we don't flap our masts and sails.  Liz is an avid birder so I get to think about some esoteric stuff once in a while she is identifying birds through her binoculars.  The same thing holds for many other birds such as gulls, swifts, swallows and falcons.  There are other things at play here but just though I'd muddy the water a bit.

It would be easy to try this rig in the reefing position of Graham's cat ketches like the CS or BRS boats.  Hey, I got one of those. ;D

Link to comment
Share on other sites

I'm not sure what "induced drag" means.  I've long imagined that the square-headed sail was less efficient because of the long edge along which you'd lose pressure difference--like a low-aspect centerboard.  --the sort of problem Bolger fixes in a shallow rudder by adding an end plate.  The other place I've see a square head lately is in Matt Layden's Paradox, in which it is made necessary by his system of raising and reefing from the interior of the boat.

Link to comment
Share on other sites

Induced drag is disturbed air coming off the edges of the foil (greatest at the tip, decreasing toward the root), back "feeding" the low pressure side of a foil in flow. It is calculated as a coefficient and is equal to the square of the lift coefficient, divided by the quantity, times an efficiency factor, times the aspect ratio,

An elliptical foil tip would have a 1 efficiency factor, while a square tip possibly 30% less. This is substantial, but you also lose a percentage of effective area with the elliptical tip, so square tips are most often used (in spite of the WWII Spitfire example often used to warrant implementation). The lift gain, of the additional area in a square tip, can partly offset increases in tip vortices. This is particularly true when you incorporate "washout" into the tip, which all sail makers do. It would be interesting in this vain (sail top shape) to know how he wants the sails cut and how much wash out is expected. I would think these would be pretty flat with a minium of washout.

The affects of induced drag are primarily an increase in the angle of attack, caused by the disturbed flow, backing around the foil. It was often called "drag due to lift" in the old days (when I learned these things) and it differs with the square of the lift component.

To see this effect in action; watching high speed aircraft on landing in rain, light fog or high humidity days, will produce curls of whitish vapor at the wing tips. Watch any Space Shuttle landing and the effect is clearly visible.

Jeff you're correct in that higher aspect foils have less induced drag then lower aspect versions.

I've always enjoyed Gary's innovations over the years, he's been a major contributor. I didn't spend much time on he's site, as I'm familiar with this latest idea of his. I suspect his efficiency assertions are more likely a result of the mast free luff, the lack of head twist off, a fully battened sail in a balanced lug configuration. I'm not sure how well he'd do against a 3/4's sloop of modern design going to windward, where I guess he'd be at a slight disadvantage, but with sheets freed up a bit, he'd have the cards in his hand, until a downwind sail was hoisted on the sloop. The free standing rig, streamlined mast and clean luff would help the lower aspect ratio issue to windward, but I still think he'd lose against an equal hull and a conventional gennie/full batten main Bermudian rig. In a tacking duel, he would have a clear advantage, but a fair sloop driver would only fall for that ploy once on the upwind leg.

Link to comment
Share on other sites

Hoyt's HBR looks to be a high tech version of the balanced lug, which in many ways is the same design as the Chinese junk rigs from way back when. So yes, not entirely new. :) I imagine it will be settled the old fashioned way......they will build and race them. No clue when that video was shot, so perhaps it has already been settled?

But I find it interesting that he is coming up with that, along with another designer of freestanding rigs that Garry referenced in a thread back in December:

http://www.sponbergyachtdesign.com/StateoftheArt.htm

Different design....this one having the high aspect profile, but again, advocating something other than triangular shaped sails. Actually, something pretty similar to what Graham used on the EC 22 Southern Skimmer. Certainly these are not the only guys using this stuff, it's just the ones I'm aware of...examples I can point to.

Unless I got it wrong, it was my understanding that the British used mostly balanced lugs on their small boats. Simple rigs to hoist and stow and they worked on all points of sail. That was my interest in trying one for the Spindrift. An efficient, low profile rig that would be simple to rig and to sail, so something you could do easily on the water.......to get you around the anchorage to avoid rowing. Opens up a bigger anchorage area and other areas for exploring. Perhaps not the best for racing, but that only matters if you are racing.

Link to comment
Share on other sites

Hoyt's rig is interesting, but seems a bit much for the kind of boats we build.  I tend to think that the work Michael Storer has done with the balanced lug on his Goat Island Skiff (http://www.duckworksbbs.com/plans/storer/gis/index.htm) is more in line with what we enjoy.

Bill

Link to comment
Share on other sites

Storer is another one I was aware of.

When comparing the two videos, looks like the GIS skipper his hands full, and that isn't much wind. Boat design has a lot to do with that I'm sure. The GIS sail also has a lot more twist, looking a lot like the traditional gaff rigs shown in Hoyt's video. On the GIS, not much sail forward of the mast to balance it.

BTW, this is how Storer sets up the GIS rig:

http://www.storerboatplans.com/GIS/GISRigging.html

I should point out I only posted this as I found the design interesting. Fun stuff to think about. And it occurs to me this thread has swerved into nothing to do with B&B designs, so Frank may want to move it over to the main forum.

Link to comment
Share on other sites

I don't think I would be tempted to try Michael's rig.  The only reason I mentioned placing Hoyt's rig in the reef position of our B&B boats is for experimental interest.  I think the cat-ketch sprit-boom sails we use are the best general purpose sail rigs that I have run across in many years of sailing all kinds of boats and rigs.

Not only do they perform well in comparison to other rigs but maintaining control in iffy conditions is superior to most other rigs.  Not to mention that no other rig is so easily and quickly set up and launched.

Link to comment
Share on other sites

  • 3 weeks later...

The theory about square/elliptical headed sails as being better than pointed headed ones is open to argument. Some soaring/gliding birds take the long pointed wing approach.  Prime example is the albatross which lives on the open ocean and seldom lands except to feed or breed.

Howdy Tom,

It is even more open to question than you suggest.  The "square top" sails are usually tall and elliptical with the top lopped off.  Garry Hoyt's is not "square top" - it is much closer to just square.

A bit of getting caught up in marketing hyperbole in the video.  (not Tom's - Garry's)

For those who don't know this is what a "square top" looks like.  The first class that used it to my knowledge was the Leander "R" class skiffs in New Zealand circa 1980 (bit over 12 feet long with big sails).  The following image shows the current Americas Cup version on the right and the even more square topped one of the AC class that was proposed by Schnackenberg (hope I've spelt his name right)

acc5_vs_ac90_design_saved_for_pc_big.jpg

and performance cats have been big users - the first main group I am aware of after the R-class

2038777944_d2a0b376c4.jpg

cf ...

BR01.jpg.w180h298.jpg

The other question of course is whether the swings and roundabouts employed make it worthwhile.  He talks about the drag "from wire rigging" but doesn't really extend it to the extra bits of permanent wire in his rig  compared to the conventional balance lug.

Plus that the "yard" doesn't appear to come down as the sail is reefed (or does it) - if it does come down I can't see the point of the blocks and lines at the throat and peak and can't work out what you do with the wires.  And if it doesn't come down you can't reduce its windage as the sail is reefed.

This could be a real problem in the sizes of boats that are mostly built on this website and mine.

Also reefing you have four sail corners to adjust if the "yard" doesn't come down.  And the yard not coming down might be very problematic in a small boat as the wind comes in.

Then from cost - while it would compare VERY favourably with the cost of a conventional stayed rig and so makes a lot of sense from a production boat point of view, it doesn't really compare with the 5 bucks of rope that do the job of the yard and boom pivots on a conventional balance lug.

My sense after doing more than a few races against boats like Lasers in my sailing canoe and others in the GIS is that the difference in performance between mast to windward and mast to leeward is hugely overstated except for the caveat mentioned on my webpages about extremely light winds.

So I think it has three marked advantages

1/ It will be much cheaper in a production boat context compared to conventional rigs

2/ It is patentable

3/ Depending on how it is done it may produce less chafe of halyards etc for passagemaking purposes.  I've never had a problem with small boats, but once you get up toward the size of boat that does passages the lug can be vulnerable.

As far as whether the Balance Lug (storer style is actually very traditional so is not really "my" method) should be used on B&B designs ... I don't think it is worth it unless you want to reduce the mast length or lower the centre of effort of the sails.

When I choose a rig I generally focus on the performance for the buck.  The way to maximise performance is to control twist.

The three rigs that control twist without extra gear are the balance lug, sprit rig and the lateen.

The sprit rig is what we chose for our OZ PDRacers and is on most of the B&B boats - so I don't want to change what anyone is doing - the boats look fine as they are.  For the OZ it was a question of 2 spars rather than 3.

If the mast on a sprit rig is designed to bend and depower the sail then the rig has the heeling moment of a much lower rig anyhow.

I don't like the lateen quite so much as it does restrict the aspect ratio and area quite a lot and forces a lot of sail area way back in the boat.  Excellent rig for some boats though and a piratical feel beyond any other!

Best wishes

Michael Storer

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...

Supporting Members

Supporting Members can create Clubs, photo Galleries, don't see ads and make messing-about.com possible! Become a Supporting Member - only $12 for the next year. Pay by PayPal or credit card.




×
×
  • Create New...

Important Information

By using this site, you agree to our Terms of Use.