Fully battened main - effect on weather helm ?

[Boo2]

Hi,

I have read lots on these forums about the dis/advantages of fully battened mainsails and am not looking to restart that general discussion in this post.

I am specifically interested to know if they have any effects on weather helm, particularly whether they can bring about a reduction in this ?

Many thanks,

Boo2

 

[simonfraser]

more like an increase in weather helm.
however the sail is easy to trim, provided you have a traveller.
i can adjust mine to balance to boat with a furled genoa or a code zero asymetric on a tight fetch.

 

[Cariadco]

Fully Battened....

My current boat is the only one I've had, that's got a fully Battened Main.
It might be the design, hull shape, keel, mast size etc etc, but this one's fantastic!! No weather helm at all! Not a drop of it!!
A couple of Years ago, we did the south Ionian regatta, which blew up into a solid 30 Knot headwind. We passed loads and loads of boats that had masses of churning white water from the weather helm, and we had none!!,
My old Bendytoy was a Bugger for weather helm, and I don't miss it at all!!

 

[rudolph_hart]

Only in as much as battens can be tensioned, which flattens the sail and reduces its draught.

Racers flatten & reduce the Main's draught with the Cunningham on the luff, and the leech 'flattenning reef' as the apparent wind increases. This reduces heel and weather helm, though 'dumping' the mainsheet in the gusts is necessary as well. If the windspeed increases further they start putting in reefs.

IIRC, catamaran racers tension their full-length battens if it's windy.

My current boat has neither Cunningham nor 'flattener', and I don't miss them because the full battens keep the sail flatter, even when reefed.

Hope this helps.

 

[TradewindSailor]

I can't see why a full-battened main should effect weather helm. Weather helm is created by poor aeodynamics and/or unbalanced sails.

Fully battened sails would tend to retain their shape better than conventionally battened sails. As for altering the camber of the sails ..... that effect is the same on both types, although batten tension in the former is pretty important.

 

[michael_w]

Put a big elliptical roach on it and it will reduce your weather helm owing to the reduction of induced drag. A narrow triangle is very inefficent, one of the reasons why boats with in-mast furling mains are slower than their regularly rigged sister.

 

[Lady Campanula]

A narrow triangle is very inefficent.....

Aspect ratio? Marchaj' 'Aero-Hydrodynamics of Sailing'.....?

Dare I say 'Bolleaux'?

Woo-hoo! A whole new argument for us to play with!

 

[dt4134]

Aspect ratio? Marchaj' 'Aero-Hydrodynamics of Sailing'.....?

Dare I say 'Bolleaux'?

Woo-hoo! A whole new argument for us to play with!

The same bloke does also favour big roaches. (In fact he seems most keen on elliptical leading edges with very bendy upper portions of the mast).

Note that IRC heavily penalises roach too, so they must reckon it does something major for performance.

 

[LostinFrance]

Punch the battens in and the sail does NOT get flatter.

 

[Bosun Higgs]

I am specifically interested to know if they have any effects on weather helm, particularly whether they can bring about a reduction in this ?

Many thanks,

Boo2

Comparing like with like ie new fully battened sail with a new half battened sail, same cloth same boat etc I can't see any reason why it would make a material difference. Nothing you couldnt achieve by increasing mast rake.

 

[William_H]

Weather Helm

IMHO weather helm comes from heeling the boat. The amount depends on the shape of the hull. Beamy flat bottomed hulls showing more savage weather helm. The only answer is less heel.
This can be achieved by flatter sails and more dumping of mainsail pressure in gusts. But mostly it is achieved by sail reduction. A full length batten mainsail may help here but not necessarily. (A smaller jib will often reduce weather helm which is the opposite effect that you might expect from the logic of boat balance. It shows that "balance" is only evident when the boat is flat.

Full length battens when tensioned up force a camber in the sail which is ideal for light winds. I think when you start putting a lot of tension on the sail as you do in stronger winds, that the power of the battens becomes insignificant and camber is reduced. I don't change the batten tension in my main from year to year. Should I? olewill

 

[michael_w]

Copied from Dashews' Cruising Encyclopiedia:

MAXIMUM ROACH
So far we’ve been talking about mains (and mizzens) that reside within the triangular confines
of the mast, boom, and standing backstay. Now onto the next phase.
Would you like to make a quantum leap in your cruising performance? Does the idea of sailing
faster with less heel sound appealing? Does your conservative (by today’s standards) cruising rig
leave you wallowing in the wake of your more highly powered neighbors? If the answer to any of
the above is yes, read on.
First, a little theory. Sailing to upwind, sail area generates lift and drag. To improve performance
the objective is to reduce drag as much as possible while increasing lift. In most cases,
within a fixed set of rig parameters, there’s little you can do toward this end.
Of the various forms of drag you deal with, induced drag is the most harmful. Reducing induced
drag allows you to sail in a more upright fashion, closer to the wind, and faster, too. (The less
efficient your hull and keel are to windward, the more important this becomes.)
Short of replacing your entire rig with a taller, more efficient spar section and putting on a new
deeper-draft keel, there’s been little you can do — until now.
On the other side of the equation, boat speed (in light-to-medium airs) is pretty much a function
of sail area. More area equals more drive, and as long as you’re not overcome with drag (in the
form of heeling), more sail area is better.
In the last ten years, as the full-batten sail has come of age, I’ve seen dramatic proof that reducing
drag and increasing area really helps cruising boats to perform. In six cases I’ve been directly
involved with, hollow-leech mainsails have been replaced with full-batten conventionally
roached sails. The 10-percent increase in sail area has been, as expected, beneficial.
96 MAXIMUM ROACH
But more surprising
have been the
other results: significantly
less heel while
going faster, with
reduced weather
helm.
Counterintuitive
as the preceding
statement may seem,
there is sound basis
in theory.
When I asked John
Letcher, a highly
experienced aero/
hydrodynamicist
about our observed
results, he wasn’t at
all surprised.
“Induced drag is
inversely proportional
to span (luff
length) squared,
divided by sail area.
The closer you can
get to an elliptical tip
shape, the better off
you’re going to be.”
And of course, what
we’d observed with
the added roach area
was an effective step
toward an elliptical
tip shape.
I asked John just
how much better the
drag might be. “The
difference between a sail built to IOR maximum dimensions and a hollow-leech sail could be as
much as 40 percent,” he told me.
This is even more important on a cruising boat, with its relatively inefficient (compared to a
racing boat) hull and fins.
Peter Schwenn at Design Systems added that “the extra area, up high, works better because the
wind is stronger aloft. And even though the center of effort in the sail is higher and there’s more
area, the reduction in induced drag could result in less heel.”

Sorry about the page layout!

 

[oldsaltoz]

I found this item some time ago, some good tips fro trimming your main.

http://www.uk.northsails.com/SailBetter/MainsailTrim/tabid/7031/language/en-US/Default.aspx

 

[boatmike]

Hi,

I have read lots on these forums about the dis/advantages of fully battened mainsails and am not looking to restart that general discussion in this post.

I am specifically interested to know if they have any effects on weather helm, particularly whether they can bring about a reduction in this ?

Many thanks,

Boo2

A FBM will probably have more roach and move the centre of effort of the sail aft if it has any effect at all. This will in fact increase weather helm not reduce it.

 

[Scotty_Tradewind]

My Twister has in the past had a little more weather helm than I've felt comfortable with and this season I'm sailing with an adjustable forestay having had a new furler fitted.
With a shorter forestay and with the masthead rig my mast is at present upright and straight and the weather helm is now very comfortable.
She does have a set of 4 full battens which tend to keep the main powered even when the mainsheet is let off to spill wind, which has the effect of levelleing up the boat and keeping the speed.

 

[Monique]

My old Bendytoy was a Bugger for weather helm, and I don't miss it at all!!

Bendytoys are known for this problem. Friend has a Celebration 411 ... he loves to helm my boat. I hate to helm his.

I wonder if the Bennies racers are as bad...? Been thinking about a 45f5...

 

[Bosun Higgs]

Comparing like with like ie new fully battened sail with a new half battened sail, same cloth same boat etc I can't see any reason why it would make a material difference. Nothing you couldnt achieve by increasing mast rake.

Wrong way round of course! Make the mast more upright to reduce weather helm.

 

[charles_reed]

Hi,

I have read lots on these forums about the dis/advantages of fully battened mainsails and am not looking to restart that general discussion in this post.

I am specifically interested to know if they have any effects on weather helm, particularly whether they can bring about a reduction in this ?

Many thanks,

Boo2

If the question you're asking is "Will a fully battened mainsail reduce weather-helm on a boat suffering from it with a conventional main?", I think not.
In fact, because a fully battened sail requires a wider sheeting angle, it would appear, at first sight, to have the opposite effect.

I think you need to have a look at mast rake and/or rudder balance.

 

[William_H]

Full battened mainsail

Copied from Dashews' Cruising Encyclopiedia:

MAXIMUM ROACH
So far we’ve been talking about mains (and mizzens) that reside within the triangular confines
of the mast, boom, and standing backstay. Now onto the next phase.
Would you like to make a quantum leap in your cruising performance? Does the idea of sailing
faster with less heel sound appealing? Does your conservative (by today’s standards) cruising rig
leave you wallowing in the wake of your more highly powered neighbors? If the answer to any of
the above is yes, read on.
First, a little theory. Sailing to upwind, sail area generates lift and drag. To improve performance
the objective is to reduce drag as much as possible while increasing lift. In most cases,
within a fixed set of rig parameters, there’s little you can do toward this end.
Of the various forms of drag you deal with, induced drag is the most harmful. Reducing induced
drag allows you to sail in a more upright fashion, closer to the wind, and faster, too. (The less
efficient your hull and keel are to windward, the more important this becomes.)
Short of replacing your entire rig with a taller, more efficient spar section and putting on a new
deeper-draft keel, there’s been little you can do — until now.
On the other side of the equation, boat speed (in light-to-medium airs) is pretty much a function
of sail area. More area equals more drive, and as long as you’re not overcome with drag (in the
form of heeling), more sail area is better.
In the last ten years, as the full-batten sail has come of age, I’ve seen dramatic proof that reducing
drag and increasing area really helps cruising boats to perform. In six cases I’ve been directly
involved with, hollow-leech mainsails have been replaced with full-batten conventionally
roached sails. The 10-percent increase in sail area has been, as expected, beneficial.
96 MAXIMUM ROACH
But more surprising
have been the
other results: significantly
less heel while
going faster, with
reduced weather
helm.
Counterintuitive
as the preceding
statement may seem,
there is sound basis
in theory.
When I asked John
Letcher, a highly
experienced aero/
hydrodynamicist
about our observed
results, he wasn’t at
all surprised.
“Induced drag is
inversely proportional
to span (luff
length) squared,
divided by sail area.
The closer you can
get to an elliptical tip
shape, the better off
you’re going to be.”
And of course, what
we’d observed with
the added roach area
was an effective step
toward an elliptical
tip shape.
I asked John just
how much better the
drag might be. “The
difference between a sail built to IOR maximum dimensions and a hollow-leech sail could be as
much as 40 percent,” he told me.
This is even more important on a cruising boat, with its relatively inefficient (compared to a
racing boat) hull and fins.
Peter Schwenn at Design Systems added that “the extra area, up high, works better because the
wind is stronger aloft. And even though the center of effort in the sail is higher and there’s more
area, the reduction in induced drag could result in less heel.”

Sorry about the page layout!

That is well explained however... The promises are grossly over exagerated. What does 40% improvemnt mean. You go 40% faster? Obviously not.
There is no doubt that an eliptical top is more efficient. The famous spitfire fighter was a one of the first to use the eliptical wingtip for better performance. However I believe it was decided the extra cost of manufacture did not justify the eliptical wing tip on other planes.
Gliders by comparison use a very high aspect ratio to reduce the effect of induced drag. Here the sail (wing is so long (high) compared to the chord that induced drag becomes less significant, compared to drag from lift.
Induced drag is caused by the air on one side of an aerofoil (high pressure side) moving to the other side (low pressure side) via the end of the foil.This movement does nothing for lift but does induce drag.
hence the benefits of a wing keel or a bulb to make this leakage path longer.Likewise some modern jets have small fins on the end of the wings to reduce this induced drag. yes it does help. But again not all jets have them the benefit is just not so great that they have become mandatory.
So if you are all out racing on otherwise identical boats an eliptical shape for top of sail (large roach) may be benefit, although some benefit may be simply from more sail area. Not much advantage when the wind comes up and you want to reef anyway.
So don't get excited a fully battened (large roach) mainsail will not give you hug improvements in a cruising boat. good luck olewill

 

[charles_reed]

That is well explained however... The promises are grossly over exagerated. What does 40% improvemnt mean. You go 40% faster? Obviously not.
There is no doubt that an eliptical top is more efficient. The famous spitfire fighter was a one of the first to use the eliptical wingtip for better performance. However I believe it was decided the extra cost of manufacture did not justify the eliptical wing tip on other planes.
Gliders by comparison use a very high aspect ratio to reduce the effect of induced drag. Here the sail (wing is so long (high) compared to the chord that induced drag becomes less significant, compared to drag from lift.
Induced drag is caused by the air on one side of an aerofoil (high pressure side) moving to the other side (low pressure side) via the end of the foil.This movement does nothing for lift but does induce drag.
hence the benefits of a wing keel or a bulb to make this leakage path longer.Likewise some modern jets have small fins on the end of the wings to reduce this induced drag. yes it does help. But again not all jets have them the benefit is just not so great that they have become mandatory.
So if you are all out racing on otherwise identical boats an eliptical shape for top of sail (large roach) may be benefit, although some benefit may be simply from more sail area. Not much advantage when the wind comes up and you want to reef anyway.
So don't get excited a fully battened (large roach) mainsail will not give you hug improvements in a cruising boat. good luck olewill

Sorry to correct you William, but in experience with two boats before and after fitting with fully battened main, provably improved a boat's sailing performance. That's in about 18 years and 50K odd miles sailed.

Leave aside the big roach question as a separate issue.

Like for like sizes, you get considerably more drive from a fully battened main than an unbattened one and far less heeling moment. I'd put the improvement more at 20%, than the 40% claimed by Steve Dashew.
This improvement comes with several disadvantages.
In light airs the battens will frequently refuse to re-align to a new tack and you have great difficulty in de-powering the main on its sheet in gusts. Additionally you'll find a fully battened main is much flatter cut than a conventional one, so the option of increasing camber in light airs is also reduced. The additional weight of battens and the friction of the batten cars make lifting the main hard work and dropping it, unless head to wind, equally arduous. Chafe, with swept-back spreaders, becomes more of a factor when reaching or running and the thunder of the battens re-aligning themselves when motoring in light airs makes an hideous noise
You also, because of the greater drive of the main, need more reef points than on a conventional sail.
On the subject of roach - an elliptical tip and big roach are only feasible if you can get rid of the backstay. Dashews, apart from being West Coast sailors, started sailing on multihulls with no backstay.
I do have an oversize roach on the current main, it overlaps the backstay by about 18", but above F3 I put in the 1st of 4 reefs. This oversize (by about 20%) main partially corrects the light-air lee-helm this boat suffered in light airs, because the centre of effort has been moved back

You need to reef earlier, and I doubt the benefits of a fully battened main would be very apparent on anything but a fractional rig boat.

Oh! one last point, a fully battened main with boom-bag makes for a much neater drop than the conventional mains used to.

All this serves to remind me that I have to re-PTFE the maintrack, the last lot of torrential rain washed it all away and lifting and dropping have become Heraclean tasks.