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Discussion Starter #1
Hi All,

Some of you may remember my posts last year asking about a main I thought didn't fit my boat. I put up the original main (yep, 35 years old), measured the luff and the foot. Laid out the full batten main in the front yard and measured it, exactly the same. BUT, here's what I saw on the ground that I did not see on the boom. The bottom of the foot where the slides are is NOT straight. The seam of the foot is straight with this arched bottom where the slides are, which can't help but have a "pocket" looking effect when you raise the sail, (the extra material hanging around on the boom that I was seeing). Any ideas what this is?

Dave
 

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Once known as Hartley18
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Some of you may remember my posts last year asking about a main I thought didn't fit my boat. I put up the original main (yep, 35 years old), measured the luff and the foot. Laid out the full batten main in the front yard and measured it, exactly the same. BUT, here's what I saw on the ground that I did not see on the boom. The bottom of the foot where the slides are is NOT straight. The seam of the foot is straight with this arched bottom where the slides are, which can't help but have a "pocket" looking effect when you raise the sail, (the extra material hanging around on the boom that I was seeing). Any ideas what this is?
Dave, it would really help if you posted some pics of what you're seeing since your post could refer to a number of things - all of them quite normal - and one or two that aren't.


:worthless:

(I've always wanted to use that smiley and never had the opportunity 'till now.. :) )
 

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Mainsails have a curved foot in them so the sail bags a bit in light winds which helps performance as soon as you reef the foot tightens up as you dont want a baggy sail in strong winds.
 

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Dave
What you might be seeing is a natural camber or pucker built into the foot to help create the bagginess that you want in lite winds. This would be drawn out as you apply out haul in heavier wind conditions, flatting the sail. Just my .02
Peter
 

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If this curved foot section has sail track slugs attached, is 'curved', its probably what is known as a 'shelf foot'.
Its purpose was to allow for full draft to be carried down well into the lowest panel sections of the sail and to lessen air flow across the foot from the high pressure side to the low pressure side.

Shelf footed mainsails are from a time when it was thought by most racing sailors that FULL draft was beneficial in light winds and from a time when most racing sailors sailed dead down wind (on purpose and with all sorts of auxiliary downwind sails - bloopers, tall boys, spinnaker staysails etc.) - in effect its a mainsail that is optimized for sailing dead down wind.
(Modern aerodynamics theory as applied to sails (~mid 1970s) has proved this to be very inefficient. Most of what most folks learned in a high school 'science' class about what creates lift and how wings/sails work is ... dead wrong!)
Such sails usually were also constructed with a flattening reef ... and there may be reefing cringles a foot or two above the foot on the leech and luff.

It's still useful and just as efficient as a modern 'loosefoot' mainsail; although its more difficult to tension and adjust sail shape in the foot section, usually needs a multipart block system on the outhaul.
 

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Discussion Starter #8
Thanks Rich,

The 1st owner of the boat was a "racer" and your description makes sense. Both of these sails are very old by most standards and really need to be replaced. My wife's biggest question is "if the 30+ year old sails work, why get new ones"? I'd like to hear from someone that's been in my shoes. Will a new set of sails (other than look good) really make a difference on a 5 1/2 ton 31' cruiser?
 

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if it works dont fix it...

now if you were about to set off on a cruise long distance or start racing then you know your answer

all I would look at closely and a tip mentioned on here is try to poke a hole on a non essential part of the sail material, if its really easy, flaky and brittle you know your on borrowed time, however if your stitching is all good, no rips or anything why change it

spend or save money elsewehere

having said that new sails are something awesome and yes youll see a noticeable difference especially tacking and how the sails set initially...your max speed will probably improve in the .5-1knot range, especially light air sailing.
 

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I think I may agree with your wife.

This is probably a 'boltroped' woven dacron sail - has a 3-strand 'rope' inside a sleeve along both the foot and the luff. These boltropes usually shrink over time and use; and, are the cause (the chief cause) of why such mainsails get 'baggy' - rarely FLATTER.
If the sail cloth looks as if its in good shape and is not UV burned and weakened, a sailmaker can usually 'ease' that boltrope back to original length or replace it .... and with the sail regaining its proper shape - all at a fraction of the cost of a new sail. Sailmakers dont like to do this as they sell less 'new' sails, so look around for one who will do this.

Here's how to evaluate the need to have the boltope 'adjusted' ---- and also how to properly RAISE a DACRON mainsail that has a 'boltrope': How to properly RAISE a woven dacron mainsail - SailboatOwners.com - see post #1
For the foot section, when easing ask the sailmaker to set LESS boltrope preload for the foot section for a 'flatter' and 'less draft' sail .... if you sail typically in venues in the 'higher wind ranges', say 15-20kts also consider to have the luff boltrope 'pre-load' set 'looser' and then this sail then can be carried 'full up' into those higher speed winds and with less need to reef. This 'overall draft reduction' will be beneficial also in 'very light' wind venues. You really only need full draft when in steep WAVES and need POWER to punch-through.

Note: if the boltropes are NOT in a sleeve but are hand sewn directly to the sail's luff and foot (this is expensive craftsman-like construction and the boltrope will be totally exposed and you will see the rope strands totally exposed), ...... if they are shrunken, then consider a new sail as such boltrope replacement for such a sail is 'expensive'.
 

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Thanks Rich,

The 1st owner of the boat was a "racer" and your description makes sense. Both of these sails are very old by most standards and really need to be replaced. My wife's biggest question is "if the 30+ year old sails work, why get new ones"? I'd like to hear from someone that's been in my shoes. Will a new set of sails (other than look good) really make a difference on a 5 1/2 ton 31' cruiser?
Good sails make a massive difference compared to blown out sails. We can't tell just based on age and without any photos how well your current sail is working.

New sails will be able to be flown flatter, which gives you less heeling in moderate to high winds and better pointing in all winds. For some reason there is a myth some places online that only racers care about such things, but as a cruiser I also want my boat to be comfortable (reduced heeling) and to perform better (because that allows me to sail instead of motor).
 

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S/V Wyndwitch - Morgan 24
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If this curved foot section has sail track slugs attached, is 'curved', its probably what is known as a 'shelf foot'.
Its purpose was to allow for full draft to be carried down well into the lowest panel sections of the sail and to lessen air flow across the foot from the high pressure side to the low pressure side.

Shelf footed mainsails are from a time when it was thought by most racing sailors that FULL draft was beneficial in light winds and from a time when most racing sailors sailed dead down wind (on purpose and with all sorts of auxiliary downwind sails - bloopers, tall boys, spinnaker staysails etc.) - in effect its a mainsail that is optimized for sailing dead down wind.
(Modern aerodynamics theory as applied to sails (~mid 1970s) has proved this to be very inefficient. Most of what most folks learned in a high school 'science' class about what creates lift and how wings/sails work is ... dead wrong!)
Such sails usually were also constructed with a flattening reef ... and there may be reefing cringles a foot or two above the foot on the leech and luff.

It's still useful and just as efficient as a modern 'loosefoot' mainsail; although its more difficult to tension and adjust sail shape in the foot section, usually needs a multipart block system on the outhaul.

Nicely said!
One of my mains is built this way....the "shelf" was often offered with a zipper to dump air when wind strengthened...
The flattening reef is actually a nice feature particularly when the sail is older ...im looking forward to the new loose footed main on the way!....
 
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