# How much Backstay?



## xuraax (May 3, 2007)

Hi,

I race on an Elan 37 equipped with a good set of tape drive sails. Although we do well at lower winds, as the wind gets above 15knots we get control problems, with the boat constantly broaching into the wind with full main and even jib no 3.

We are trying all sorts to flatten the main including maxing out the outhaul, cunningham and the backstay but although matters have improved it appears not to be sufficient.

Now I am wondering if we are pulling up on the backstay hard enough. When i do still at the mooring and look up the mast I note that the very top is curving significantly but the middle part of the mast is hardly changing shape. Therefore we may not be flattening the main enough to maintain control.

How does one gauge the maximum amount that the backstay can be tensioned before risking trouble?

I get the impression that the inner stays may be set too hard and therefore they are stopping the mast from curving forward when tensioning the backstay. Is there any advice out there on how hard to set these what is the limit before one can cause damage?

thanks.

xuraax


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## Jeff_H (Feb 26, 2000)

I suggest that you talk to your sailmaker. A good sailmaker will design their sails for a specific range of mast bend and headstay sag. The old rule of thumb was that the aft lowers should just begin to go slack in heavy air with max backstay applied but this varies with rig and sail design.

As a mainsail trimmer on a Beneteau 40.7 with a similar rig, there is one other point here, as the wind comes up into winds over 15 or so knots, its not hard to end up being overpowered with a #1 genoa. As you approach those windspeeds it is not all that hard to be overpowered, and end up using too much helm.

It becomes incumbent upon the mainsail trimmer to aggressively pay attention to the position of the helm, (the mainsail trimmer often needs to mark the centered spoke of the wheel so you can monitor it. I carry blue masking tape in my seabag which works well as a temporary marker), heel angle, pointing angle, and boat speed. If the traveller is too high and the mainsail too powered up, it makes it very hard to for the helmsperson to bear down and keep the boat moving. If it the traveller is too low and the mainsail is too depowered its hard to point.

In winds approaching the limit of the genoa the key is that the jib needs to be set properly, (its head slightly open with the sheet lead slight aft so the upper teletales break slightly ahead of the lowers) and the boat needs to be sailed off the jib teletales without using too much helm. It is perfectly alright to carry as big a bubble in the main as it takes to keep allow the boat to sail off the jib and still be able to point. This takes time to learn out on the water watching the knotmeter and wind angles (or the windex which is actually a very precise instrument if you read the box that a windex comes in). It is important that you can very quickly shift gears because on gusty days at the upper end of the windrange the boat is ideally steered as much with mainsail as it is with the rudder and quick reactions and constant adjustments (as much as 3 to 6 times a minute) can result in huge gains upwind. (There is a reason that I need to work out att the gym during the winter)

One more point, there is a windspeed where using a #2 or #3 genoa can result in real gains in speed and points. (winds that are consistently over 15 knots on the 40.7 but I don't know what it would be on the Elan) and so it becomes critical to watch true windspeeds before the start and during downwind legs so that a change down can be made if it is needed.

Good luck out there, 
Jeff


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## jimmyb116 (Feb 20, 2007)

Great post jeff there is nothing I can add to that.


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## Giulietta (Nov 14, 2006)

Xura...sorry but I have some bad news....

in a way, you guys are victims of the boat you sail...it´s not you or the sails or the crew, is the boat..these boats are designed, as many so called cruiser/racers in the proiduction series, (and I am assuming the boat in question still has original keel, rudder and has not gone thru a "weight loss program" to race), to be sailed as coastal cruisers with friendly multiple rating races schedules against other same type boats, and not One design or box rule type races......this to say that the type of mast adjustments, keels, sail, CofG, CofE etc. are all designed to be sort of neutral to provide confort to a regular coastal sailor, as that boat is a fast cruiser, that can be raced... 
Therefore, mast trim, shroud tension, mast bend, sail plan, keel weight, draft and shape etc. are all designed for a lower band wind speed, and somewhat limited in the range of adjustment...and to the assumption that the "average" sailor will reef, douse, furl etc. as the wind increases.

However, and in your case, if you feel you need more bend, there are several things you can do, even with the present sails, these include, 

1) adjusting mast tension with a loos gauge, based on the winds before departure to the race, this is a thing where the more you do it and the more you become expereinced, the better you become at it..select only one person in the crew and only him should do it to avoid arguments..I do it myself, but I have a hydraulic jack under my mast, to do it on the go. The advantage is I adjust shroud tension based on the winds.

2) Preset intermediate inner shrouds to limit mast bend. You can ease some the inner shrouds to allow more belly in the mast. How to adjust..in a calm day hoist the main, so you can look at camber, tension the BS and release slightly the intermediate inner shrouds as you bend the mast backwards, with the BS..with this method the inners will be almost completely loose when mast is at rest..I have mine set like this..I provided maximal bend and the limit is set by the inners intermediate that tension at full BS tension..be carefull you need to know what you´re doing..

3) Check angle between genoa and main, and if needed open the gap between them, or close as needed, with the installation of barber haulers.

4) don´t be affraid to release some the main sheet until the portion of the sail along the mast actually cambers the other way, this will help even the boat, and it will actually accelerate. The cunningham plays an important role here..



I have a formula that allows you to measure maximal mast bend at the tip of the mast and how much belly you can induce, based on mast height, that I will provide to you by private pm, should you require so.

These will do for now, should you want to pursue this discussion further let me know..Jeff´s points are 100% right on..he knows main trim for sure.

Alex


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## Faster (Sep 13, 2005)

Two excellent posts above from Jeff and Gui. I would just reinforce the idea of aggressively playing the traveller in the conditions you describe. Easing the traveller will keep the helm under control (watch the helm angle as Jeff pointed out) and be ready to power up in the lulls.

If the traveller is already all the way to leeward, then the vang should be on hard so that when the mainsheet is eased further the boom can't lift...and it has a similar effect to further easing the traveller if you could.


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## Giulietta (Nov 14, 2006)

Actually Faster brings a good point...the vang...and it´s use.

In fact in some settings and with certain sails and configurations, releasing a little the vang can help open the roach and spill wind aloft..

Like I said, it really depends on ther boat, system and sail..

With mine, releasing some vang tension helps spill wind aloft, but If if I need with other vang tensionings I can also prevent that from happening...

Faster is right...the vang..

Experiment with your boat with tension and mild tension. Play with the vang and see.


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## Faster (Sep 13, 2005)

Thanks G..

Another thought, xuraax.. This boat looks very similar to the Bene 36.7 we sail on a bit. Often you can do well in heavier air by not fighting the roundup quite so hard, let the boat feather up into "pinch" mode (a bit - you don't want to backwind the jib). 

You may find some heel coming off, and the helm easing at that point. In puffy conditions on our former 24' frac rigged racer we went into what we called "survival pinching" in puffs and often gained a length to weather each time.

The Elan may be too heavy for this to work, but it may be worth a try.


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## xuraax (May 3, 2007)

Thanks one and all for your quick replies and sound advice.

Perhaps there is one point that I did not explain very well. When our boat rounds up, it does so quite violently to the point that we loose rudder control and we end up pointing almost straight into the wind. Picking up speed again is QUITE SLOW. Although I sail normally on multihulls I have sailed on other monos and although all monos tend to round up, it is only here that the rounding up is so damaging. I do not think the problem is the boat itself since, from what I here the Elan 37 does well in club racing. On this boat I am in general the main trimmer and I can assure you the traveller is continually on the move. 

To keep the boat on its feet we find that many times the traveller is all the way down and the main reversing. This surely can only mean drag.

This is why I am asking the question of how much bend is allowable in a mast for this size of boat.

On another point, in all the advice I get, I wonder why nobody ever mentions reefing the main before reducing the jib. I believe theory tells us that the force on the jib is acting to push the boat away from the wind and the main the reverse. Therefore when, to reef, we reduce the jib before we actually reduce the main we are in fact increasing the possibility of rounding up into the wind. 

I know that in practice this is not done but why?

Giuletta, I will try to send you a pm to get the formula you mentioned if you don't mind.

regards

xuraax


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## xuraax (May 3, 2007)

Giulietta,

I have tried to send you a PM but was not allowed by the forum because I have to send 10 messages before I am allowed to PM.

This is my number 3.

xuraax


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## Faster (Sep 13, 2005)

Reefing is, of course, an option but on short course racing many boats will want to avoid the work of shaking out the reef for the off wind legs, and so will invert part of the main to try to get by.

Having the ability to fully flatten the main helps here, of course.

Carrying a bubble in the main does not really slow you down, the leech is still driving, and keeping the boat upright more than makes up the "bad" trim.

For longer legs a reef (or two) would clearly be a good idea.

btw - go to the song chain to build up your post count!


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## xuraax (May 3, 2007)

Faster said:


> btw - go to the song chain to build up your post count!


what's that?


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## xuraax (May 3, 2007)

xuraax said:


> what's that?


ok got it. but what a waste of time.


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## Jeff_H (Feb 26, 2000)

Those slam round ups can be prevented by the helmsman and mainsail trimmer's quick actions. All boats have a heel angle at which they begin to airate the rudder and stall the rudder. That heel angle is different for each boat, but that angle is usually between 35 and 45 degrees. The boat should have an inclinometer (heel angle guage). I suggest that your crew should spend some time sailing in heavy enough winds to experiment and find that angle watching the inclinometer. Your mainsail trimmer and helmsman need to completely understand that angle and keep the boat safely below that angle of heel. That's easier said than done in big shifting gusts. 

In big gusts, as the gusts hit the helmsman needs to instantly move the helm towards the center and take a big bite to windward, and the mainsail trimmer needs to drop the traveller to the stops and if necessary then blow off the sheet going into vang sheeting mode, which does a collection of things, first of all, it unloads the low pressure side of the rudder and reduces the amount of air being sucked down the rudder blade and allows the rudder to bite again , it reduces heel angle and places more of the rudder to be in the water. Only as the boat flattens in those conditions can the helmsman begin to slowly and steadily load the blade again and the mainsail trimmer slowly apply more mainsail. 

I may be wrong but I seem to recall that some of these boats came with cabin top mounted travellers. There's not much you can do with a cabin top traveller. The kinds of quick traveller adjustments and sheet trimming is pretty much out of the question given the high frictional loads and difficulty in getting adequate sheet tension without excessive boom bend. 

On most boats it can also help to move the crew weight aft in those conditions, allowing you to use the higher stability of the stern more aggressively and pushing the rudder deeper into the water. 

You should be carrying just enough sail for the steady state condition and then be prepared to shift quickly to gust survival mode. That said, people who grew up sailing masthead rigs tend to carry way too much jib (#1's) far longer than it is needed on a fractional rig. You should be able to shift to your #3 at around 14-15 knots of true wind (20 plus knots apparent upwind) and be much more controlled and faster to boot. A modern #3 on a fractional can have a very wide range (8 knots to as much as 25-30 knots) and so offers great flexibility in those conditions. I have a flat and a full #3, both kevlar, and the full #3 works great in very light winds rounded up with massive backstay ease and great in heavy air, bladed out with massive amounts of backstay tension. 

Racing on most fractional riggers, you almost never want to reef until the steady state winds are well up over 20 knots. The mainsails on these boats are so trimmable, that they have wildly wide wind ranges. Your question about keeping a genoa up for balance ignores the fact that the leech of a #1 genoa moves the center of effort aft relative to a number 3, even though the sail itself is at the forward end of the boat. Of course opening the leech of the genoa helps move the center of effort forward a small amount but moving the car too far aft risks powering up the head of the sail. 

One minor point, I think that Alex (Giulletta) is being too hard on the Elan 37. These boats generally look like well designed IRC/IMS racer/cruisers. This is not part of Elan's goofy Impression raised salon series or their earlier IOR based series. I have always been a fan of Rob Humphrey's race boats, and the deep lead keel version looks to be one of his better designs. It may not be as sophisticated as state of the art IRC boats, but it is still a very raceable design under PHRF and probably under IRC. 

Jeff


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## xuraax (May 3, 2007)

Jeff_H said:


> I may be wrong but I seem to recall that some of these boats came with cabin top mounted travellers. There's not much you can do with a cabin top traveller. The kinds of quick traveller adjustments and sheet trimming is pretty much out of the question given the high frictional loads and difficulty in getting adequate sheet tension without excessive boom bend. Jeff


This boat has a proper traveller just in front of the wheel so this cannot be the problem. The only gribe I have is that this version has the standard keel and not the racing keel so this cannot be helping.



Jeff_H said:


> and great in heavy air, bladed out with massive amounts of backstay tension.


That was in fact the original question: How much is massive backstay tension?



Jeff_H said:


> Your question about keeping a genoa up for balance ignores the fact that the leech of a #1 genoa moves the center of effort aft relative to a number 3, even though the sail itself is at the forward end of the boat.


It is true that a genoa has a center of effort further back than that of #3 but surely it should still be in front of the centre of resistance of the boat. Otherwise there would be nothing to balance out the main and you would always have weather helm.


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## Jeff_H (Feb 26, 2000)

_"It is true that a genoa has a center of effort further back than that of #3 but surely it should still be in front of the centre of resistance of the boat. Otherwise there would be nothing to balance out the main and you would always have weather helm."_

My point was that a changing from a #1 genoa to #3 genoa will move the center of effort forward nearly as much as reefing, but the boat will be easier to handle and if that sail is made to be low stretch and take advantage of differences in headstay sag, will have a wider range of windspeeds than a reefed mainsail. 

Originally Posted by *Jeff_H*  
_and great in heavy air, bladed out with massive amounts of backstay tension. _

_"That was in fact the original question: How much is massive backstay tension?"_

That varies with the boat, but your helmsperson should be able to feel when there is too much helm, too much heel, and so either need to reduce sail area or increase backstay tension, or by the same token feels too depowered and should be eased out. There needs to be communication between the mainsail trimmer and hemsman with both able to provide input. At least on modern boats, your not going to break the boat with any amount of backstay that you are likely to put on. The bigger problem is undersized backstay adjusters and stretchy forestays. 

Jeff


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## Giulietta (Nov 14, 2006)

Xuraax, sorry I was not responding earlier.

I am away from home but for now this will do.

To answer your question...the max safe amount of mast bend, by action of a backstay, in any normal mast should not be more than 2 to 3% of the distance from the mast base (for keel steped and cabin stepped) to the mast top. ie. The lenght of the whole mast.

So if the mast is keel stepped, the distance inside the cabin counts too..


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## xuraax (May 3, 2007)

Giulietta said:


> Xuraax, sorry I was not responding earlier.
> 
> I am away from home but for now this will do.
> ..


Don't worry about it. I have just returned from abroad myself.



Giulietta said:


> To answer your question...the max safe amount of mast bend, by action of a backstay, in any normal mast should not be more than 2 to 3% of the distance from the mast base (for keel steped and cabin stepped) to the mast top. ie. The lenght of the whole mast.
> 
> So if the mast is keel stepped, the distance inside the cabin counts too..


Ahhh!!! indeed it is good to finally have some numbers on which to work on.

I will do the actual mast measurements this weekend but for now, doing an estimate based on the I specifications and adding 2m for the part of the mast inside the cabin I estimate that the total mast length is 16m. This would mean a maximum allowable bend of 32cms(2%) to 48cms(3%).

Does this sound about right?

regards


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## Giulietta (Nov 14, 2006)

xuraax said:


> I will do the actual mast measurements this weekend but for now, doing an estimate based on the I specifications and adding 2m for the part of the mast inside the cabin I estimate that the total mast length is 16m. This would mean a maximum allowable bend of 32cms(2%) to 48cms(3%).
> 
> Does this sound about right?
> 
> regards


Yes it does. However, and to play it safe, because I don't know what mast you have, start with the 2%.

In Europe Elans come with Sparcraft  (click here) masts.(Charleston Spars in the US), and of the preformance series. Click here

Some Performance masts, like the Sparcraft Performance series, will allow up to 3%, but you need to assure that pre bend is EXCATLY right. DO NOT EXCEED. My mast is a Sparcraft Performance series.

Another thing you need to check while youre at it is the pre bend.

The pre bend or "belly forward" the mast has in the middle, with the mast at rest, in the neutral position, should not exceed half of the mast diameter.

Another thing you can check is rake, wich as you know is the aft tilting of the mast, or longitudinal Adjustment.

I once wrote a procedure to help a friend Sailneter adjust his mast because he was away from a place where a rigger could do the job.

I am going to post that procedure today in another thread.

Hope I helped, and if you have any more quaestions, ask

Alex


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## Giulietta (Nov 14, 2006)

Xuraax...I made it, see if it can help you, ok?

go to the search bar and type RIG...there is a thread called 'adjsuting your rig".

Hope it helps


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## xuraax (May 3, 2007)

Excellent thread and a "must read" for everybody.


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