Thread: Lug Rig Heaven Part 2010.1

Originally Posted by Glug

"It is would be theoretically possible to do a completely straight sided sail and put all the draft in by broadseaming. In which point the broadseaming would come back from the luff to the deepest point of the sail camber - in which case it would go to the head.!" MIK

I think that this is the case with my sail, it has a nice camber all the way up the yard to the head.

"However if this was the case a small amount of mast bend would put creases in the sail as it pulled the sailcloth hard between the point of maximum mast bend and (usually the clew)." MIK[/QUOTE]

Some rigs tend either one way or the other ... but either way ... the head doesn't have much broadseaming normally. "

But you see the crease in light winds when there is no mast bend. I wonder if it has something to do with the point of attachment of the halyard. If it is attached at say 30-35% there is a lot of leverage by the sheet along the leech, pulling down the head and by leverage at the halyard attachment at the front end of the yard pulling the throat of the sail forward and up, making the crease. Particularly if the yard is highly peaked. It might go away if the halyard is attached at 40%. And it might only appear if the sail is cut rather flat at the luff.
Peter[/QUOTE]

Some creases are just "go fast" creases. The one on this sail would probably disappear with some more downhaul tension, but think that this is deliberately not applied in this case because a baggy sail is desired for these light conditions. The slight curve in the luff is evidence of this. It also looks like they are trying out a combination downhaul and kicker, so could be a shakedown sail.

I just can't find an example of "go fast" creases on a bermuda right now, but will try later.

EDIT:

OK, here are good examples. http://www.wb-sails.fi/news/WBlines/...Trimguide1.htm

What you have to do is look at the overall sail shape, and importantly the leach. The flow and exit looks pretty good on Harvey's boat, which is more important than trying remove that crease which is secondary to a good overall aerofoil shape. Sometimes people stress too much over such creases and the one on Harvey's boat. It's a completely different story for "bad" creases where a sail's aerofoil shape (ie. drive) is being badly damaged. I have being trying to sort the bad ones from my sail lately.

Hi guy's
very interesting discussion!

I do have a McNamara sail too, similar as Richard Harvey. Second one made by Michael McNamara. I have a pictures attached with this sail that shows the shape very well.
I do have a quite stiff yard, so you need lots of downhaul tension to get any curve in the yard.

few remarks based on my experience:

You see that little "crease" in my sail too, that disappears if you increase the downhaul tension. There is a similarity with a gaff-rig; if you have low peak tension there will be a crease. If you put more tension on the peak this crease disappears.
In general; in light winds you do not want that much tension on the leach to have a better air-flow around the sail. With a balance lug this means you need to lower the overall downhaul tension and this little crease is not really an issue for speed.
I agree that moving the halyard position forward will increase luff-tension versus leach-tension and will have effect on this crease. But more downhaul will finally eliminate that.

The second picture shows the effect of the downhaul tension when the wind decreased; the peak of the yard is too high. Downhoal tension needs to be decreased.

NB: Mast bend does not have effect on the balance-lug sail, since there is no "connection" with any of the sides of the sail.

NB:I do not really understand why broadseaming should not have effect in the top of the sail? As you see in the first picture, this top has a curve that's mainly based on broadseaming.

I find my yard a bit too stiff now ( I did not follow MIK's plan, but overspecified the size ). You see that I need lots of downhaul tension to have the right curve matching this sail. Works very well when there is plenty of wind, but does not give the right shape in light conditions ( when you want to be able to lower your downhoal / leach tension ) .
I am planning to make another more flexible yard this winter to be able to play with this and get the right flexibility.

Best Regards

My sailmaker tells me that the curve in the head needs to be cut to the same curve the yard will assume under 'normal' sailing loads, and that the shape in the sail is provided by the broadseaming.

I think Stewart Dabler has a formula for estimating the bend of the lug rig yard under 'normal' sailing loads - a support under the peak and throat attachment points on the yard then one third of the square foot sail area in pounds hung off the halyard attachment point.

We're going with this - cutting the head curve to the curve determined above, so my sail will (hopefully) be cut to match my (much stiffer) carbon yard.

McNamara may be cutting his sail to match a more flexible yard than Watermaat's -he has been out in Richard Harveys Blanche and commented that the yard bent more than he had anticipated. If McNamara has cut the sail with edge round based on a quite flexible yard, it presumably won't benefit from a stiffer one.

When I first specified my yard, I tried to pick a carbon section matching the stiffness of the original 40 mm dia round wooden oned which bent about 50mm with 10kg. The sparmaker objected and said it needed to be at least twice as stiff, I went with his judgement, but my sailmaker will know exactly it's bend characteristics when he cuts the sail.

A sail such as Woodeneyes may have been cut on the assumption that the yard is stiffer than his is, in this case it would benefit from a stiffer one.

Question would be, is his new alu yard now too stiff for the edge round on his sail?
This picture shows the sail with the boat on a trailer but with downhaul tensioned, it looks as if the edge round is more than the yard bend (but not by that much, it might be exactly right when on the water under sailing loads)



Here, also Watermaats yard has less bend than the sail edge round in light conditions, leading to that crease.



It would seem that critical is matching edge round to yard bend under the range of sailing loads, complicated of course by the variation in loads due to wind strength and crews weight/ability to hike.

Beyond that, the question becomes, is a more flexible sail matched with more edge round a better proposition than a stiffer yard matched with a sail with less edge round?

Obviously extremely flexible even with lots of edge round wouldn't be ideal, also absolutely rigid with no edge round, the question is where is the happy medium, and what are the plusses and minuses of being either side of it?

Ian

Originally Posted by IanHowick

My sailmaker tells me that the curve in the head needs to be cut to the same curve the yard will assume under 'normal' sailing loads, and that the shape in the sail is provided by the broadseaming.

Yes I agree. The problem with my bendy one was that it reached the limit of the sail's curve too quickly and the tip continued to bend which caused the leach to flap and fall away to leeward.

Originally Posted by IanHowick

We're going with this - cutting the head curve to the curve determined above, so my sail will (hopefully) be cut to match my (much stiffer) carbon yard.

My gut feeling from playing with the sail on its trailer in about 20knots of wind is that 20mm of bend using our "GIS standard" of a 10kg weight is about right. Presumably your carbon spar will start getting stiffer from then onward as well which is what you want as the tip will continue to control the leach.

Originally Posted by IanHowick

McNamara may be cutting his sail to match a more flexible yard than Watermaat's -he has been out in Richard Harveys Blanche and commented that the yard bent more than he had anticipated. If McNamara has cut the sail with edge round based on a quite flexible yard, it presumably won't benefit from a stiffer one.

When I first specified my yard, I tried to pick a carbon section matching the stiffness of the original 40 mm dia round wooden oned which bent about 50mm with 10kg. The sparmaker objected and said it needed to be at least twice as stiff, I went with his judgement, but my sailmaker will know exactly it's bend characteristics when he cuts the sail.

A sail such as Woodeneyes may have been cut on the assumption that the yard is stiifer than his is, in this case it would benefit from a stiffer one.

Question would be, is his new alu yard now too stiff for the edge round on his sail?
This picture shows the sail with the boat on a trailer but with downhaul tensioned, it looks as if the edge round is more than the yard bend (but not by that much, it might be exactly right when on the water under sailing loads)

Attachment 150434

My sailmaker makes the sails for Denman Marine's boats and is experienced with them. His own boat has a balanced lug so he is well qualified in this type of sail. He wasn't happy with the amount of bend in my original yard and told me to make a much stiffer one. Well, the alu yard I now have closely matches the flex of your carbon one so with some more trialling we'll know more.

Originally Posted by IanHowick

Here, also Watermaats yard has less bend than the sail edge round in light conditions, leading to that crease.

That crease is easily removed by adjusting the tension along the yard. I start with about 25mm of slack and then go from there. I've seen systems that make the adjustment possible while sailing, but really they are just a complication as our sail is quick to lower and raise again. I've added a clam cleat to the peak of the yard to make the adjustment quick and easy as this is quite critical. A lot of lug rigs, especially the PDRs seem to have the head way too taut.

Originally Posted by IanHowick

It would seem that critical is matching edge round to yard bend under the range of sailing loads, complicated of course by the variation in loads due to wind strength and crews weight/ability to hike.

Beyond that, the question becomes, is a more flexible sail matched with more edge round a better proposition than a stiffer yard matched with a sail with less edge round?

Obviously extremely flexible even with lots of edge round wouldn't be ideal, also absolutely rigid with no edge round, the question is where is the happy medium, and what are the plusses and minuses of being either side of it?
Ian

We seem to be getting closer to knowing these answers! We already know that a yard that can flex beyond the point where the maximum head round is taken up is very bad.

Thank you all for your helpful comments regarding creases and bendy yards. When I was building my boat 4 years ago, I came across this book:
W. P. Stephens, Canoe and Boat Building for Amateurs 10th Ed. 1903. “The Forest and Stream” cruiser.


http://dragonflycanoe.com/stephens/index.html
In a small boat the sail must hoist and lower easily, surely and quickly; it must be readily removed from the mast for stowage or in rowing, and it must be so placed as to balance properly in connection with the keel or centerboard. In all of these particulars the sail shown is better for sneakboxes, yachts' yawls, rowing and sailing boats, and other small craft, than the boom and gaff. The former has no mast rings to jam in hoisting and lowering, as they are always liable to do; it can be quickly
removed from the mast; the latter is stepped much further from the bow, keeping the weight aft and being easily reached and unstepped, while before the wind the sail is not all on one side of the mast and boat, but a large portion is so placed as to help balance the outer end.

The head of the sail is cut with a round of 9 in., 1 in. per foot, for the following reason: A straight stick, like a yard, is very elastic, even if of considerable size. and will bend greatly at the ends. If, however, it be curved in the first place, it then requires some force to bend it further. The principle is well shown in the common bow, which is easily strung, but then requires a heavy pull to bend it. Another important advantage follows this form; the yard or bow is first curved in a vertical plane and held there by the sail. Now, with this tension on it, it resists powerfully any lateral strain that would throw the peak to leeward. This is aided by the peculiar cut of the sail. The yard is brought far down the luff and a large part of its length is forward of the mast. When the luff is properly set up a very strong leverage is put on the yard, holding the head well to windward. The sail is approximately square in shape, as this form gives the maximum area with a minimum average of spars, mast, boom and yard.

A lug sail can hardly be set taut by a halliard, but a tack tackle must be employed, and a very powerful one is rigged

Thought that the bendy yard was just like the bendy top mast of modern skiffs so made one, but did not tell the sailmaker how bendy it was. Hence the problems I have had getting the yard and sail to match. At least I am not alone in this.

Thank you all for your helpful comments regarding creases and bendy yards. When I was building my boat 4 years ago, I came across this book:


W. P. Stephens, Canoe and Boat Building for Amateurs 10th Ed. 1903. “The Forest and Stream” cruiser.


http://dragonflycanoe.com/stephens/index.html

In a small boat the sail must hoist and lower easily, surely and quickly; it must be readily removed from the mast for stowage or in rowing, and it must be so placed as to balance properly in connection with the keel or centerboard. In all of these particulars the sail shown is better for sneakboxes, yachts' yawls, rowing and sailing boats, and other small craft, than the boom and gaff. The former has no mast rings to jam in hoisting and lowering, as they are always liable to do; it can be quickly
removed from the mast; the latter is stepped much further from the bow, keeping the weight aft and being easily reached and unstepped, while before the wind the sail is not all on one side of the mast and boat, but a large portion is so placed as to help balance the outer end.

The head of the sail is cut with a round of 9 in., 1 in. per foot, for the following reason: A straight stick, like a yard, is very elastic, even if of considerable size. and will bend greatly at the ends. If, however, it be curved in the first place, it then requires some force to bend it further. The principle is well shown in the common bow, which is easily strung, but then requires a heavy pull to bend it. Another important advantage follows this form; the yard or bow is first curved in a vertical plane and held there by the sail. Now, with this tension on it, it resists powerfully any lateral strain that would throw the peak to leeward. This is aided by the peculiar cut of the sail. The yard is brought far down the luff and a large part of its length is forward of the mast. When the luff is properly set up a very strong leverage is put on the yard, holding the head well to windward. The sail is approximately square in shape, as this form gives the maximum area with a minimum average of spars, mast, boom and yard.

A lug sail can hardly be set taut by a halliard, but a tack tackle must be employed, and a very powerful one is rigged

Thought that the bendy yard was just like the bendy top mast of modern skiffs so made one, but did not tell the sailmaker how bendy it was. Hence the problems I have had getting the yard and sail to match. At least I am not alone in this.

here's the picture

One question/important point regarding all this talk of yard stiffness and reported deflections with 10kg hung off the middle:

Where are people putting their supports at each end? The spar is 3.6m long but throat attachment to peak attachment is 3.18 metres.

The span makes quite a difference to the deflection you get as it goes with the cube of span. For example a spar that bends 24mm with supports as close to the ends of the spar as possible will only bend 17mm if the supports are close to where the sail attaches and span is only 3.2 metres. (so a difference of about 40%)

It would be good if there was some consistency to this, or at least an accurate report of what the span was between supports when the deflection measurement was made.

Ian

By the way - I enjoyed the reference to dealing with some of the same issues in 1903! Interesting their take on having the yard so flexible/edge round so much.

Hi Glug,

Brilliant resourcing finding the article from WP Stephens - one of the great promoters of sailing canoes and canoe yawls in the 1800s.

He was one of the big reasons for my first design ... wanted something light, that I could carry myself, looked traditional, was beautiful and was a platform for an interesting but potentially efficient traditional rig.

When i saw pics of sailing canoes in that era ... bang!

Atwood Manley's book "Rushton and his time in American Canoeing" (from memory) provided the first pics and then gave me a follow up for W P Stephens.

MIK

Originally Posted by IanHowick

It would be good if there was some consistency to this, or at least an accurate report of what the span was between supports when the deflection measurement was made.

Ian

By the way - I enjoyed the reference to dealing with some of the same issues in 1903! Interesting their take on having the yard so flexible/edge round so much.

I will amend the list to add a requirement and to mark the measurements that might be doubtful.

Nine inches of round in Stephen's day indicates the problems with using bamboo!

MIK

It's no secret that I harbour a desire to add a kicker to my GIS similar to the setup on Keyhavenpotter's Scow. His worked independently of the downhaul, so the two could be adjusted to give the best setting. I realise it's a bit of an added complication, but this is a forum for discussion about what works best on our balanced lug rigs, so I'd like to see if the GIS would benefit from it or not.

However, I was wondering where it should be attached? There are two obvious places; 1. the mast step, or 2. the mast partner. MIK has already confirmed that the partner is plenty strong enough to accomodate the vang attachment.

Any thoughts?

Originally Posted by Glug

In a small boat the sail must hoist and lower easily, surely and quickly; it must be readily removed from the mast for stowage or in rowing, and it must be so placed as to balance properly in connection with the keel or centerboard. In all of these particulars the sail shown is better for sneakboxes, yachts' yawls, rowing and sailing boats, and other small craft, than the boom and gaff. The former has no mast rings to jam in hoisting and lowering, as they are always liable to do; it can be quickly
removed from the mast; the latter is stepped much further from the bow, keeping the weight aft and being easily reached and unstepped, while before the wind the sail is not all on one side of the mast and boat, but a large portion is so placed as to help balance the outer end.

[FONT=&quot]The head of the sail is cut with a round of 9 in., 1 in. per foot, for the following reason: A straight stick, like a yard, is very elastic, even if of considerable size. and will bend greatly at the ends. If, however, it be curved in the first place, it then requires some force to bend it further. The principle is well shown in the common bow, which is easily strung, but then requires a heavy pull to bend it.

Although not a lug rig, the bowed yard/gaff is a feature of the Norseboats, which originated around your part of the world. I wonder if they pulled their boats up on a beach, removed their yards and went hunting!

Me not reading carefully enough.

It is quite a bit of bend. Most of the spars in W.P. Stephens' book of canoe designs from forest and stream are straight from memory.

But some might have been bent.

MIK

Originally Posted by woodeneye

Although not a lug rig, the bowed yard/gaff is a feature of the Norseboats, which originated around your part of the world. I wonder if they pulled their boats up on a beach, removed their yards and went hunting!

Norseboat (The Saga) (designed by Chuck Paine) is a tradename like Dodge Cougar, and it seems to have little to do with the real norse boats whose descendents are Oughtred's boats. The curved gaff on the NorseBoat is permanently bent and does not flex as I understood it.

Peter