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Sail slugs


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A friend of mine was observing the EC 2020 start and took these photos of one of the Cores Sounds that had a hard jibe shortly after launching. I know these plastic sail slugs can fail and that is certainly preferable to damaging some other parts of the rig. I don't currently carry spares but I'm going to get some. My understanding is that sufficient halyard tension takes most of the potential load off the sail slugs. Something to be mindful of in high winds when raising, lowering sails.






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I am stunned. I have used nylon sail slides for the better part of 50 years and a lot of sea miles and do not recall ever braking one. Carlita has a lot of miles and age with the identical batch of slides. Because it is on the main and the broken slides are from the top down I think that they came under unreasonable abuse. My only thought is that because the main is in a tabernacle which means that mast cannot rotate. If the main was over tension-ed by the snotter when close hauled, the sail tightens as it is let out. I have to ease the snotter from close hauled to a run especially if I ease the main past 90 degrees. In fact in light airs the sail will not go out without easing the snotter.


Not to be pedantic, slugs are cylindrical and are meant to go into a track designed for a boltrope.

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I talked to Bones briefly about the headache this caused him in key largo. They had to go to 3 west marines to find replacements after they broke the slides and returned to the start beach.  I assume his sail was reefed when the gybe that broke the top slides happened as i can see in the picture. I think i see the issue. With the sail reefed there is a lot more pressure on just that top slide because although the luff curve of the sail is still present, the lower part of the mast is larger and stiffer so the top slide then takes almost all the loading and when it popped the load moved down, pop, down, pop, etc like a zipper. The solution would be a double slide at the top or swapping it for a stainless slide which they do make. Here is a picture of them testing with a reef in and I can see what looks like the luff curve taking the leech load off all but the very top slide. 


Another note is that I think the downhaul should be nice and tight to stretch the luff so that the snotter tension pulls more evenly on the luff slides. If you imagine the luff tension was slack, then the snotter pulls all the load onto the top and bottom slides only. At least as i see it. 


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2 hours ago, Alan Stewart said:

I can see what looks like the luff curve taking the leech load off all but the very top slide. 

My mind gets a little overloaded trying to follow you,  but there is a beautiful gymnastic flair to your thought process that I can admire, as you nail your landing.

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With a conventional boom, you have a tack connection that is a separate piece of hardware.  What about a guide for the down haul through a fairlead so that it acts similarly? That leaves just the peak slide/lug/slug/car to worry about. I had considered in in mast block instead of the hardware block we all use. But this only helps with a full sail, not reefed. I have no issue, but will consider adding a doubling car if it ever seems a prudent idea.

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Is the main snotter location on the mast high? When double reefed the angle between the clew and the main snotter increases. Would this focus more of any excessive sprit tension on the top of the sail?


I have stretched some of the lower main sail track by neglecting to ease the snotter when easing the main sheet.

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I have been thinking about this a lot today and after seeing the last picture I think that Joe's last comment is exactly right coupled with an overtight snotter for the strong wind gybe.


If you look closely at the reefed main, you can see that the clew grommet is a lot further above the sprit than on the mizzen. If the main snotter was released and the reefing line was tightened until the clew grommet was close to the sprit, the downhaul is eased 6", the halyard re-tightened and the snotter tension set for the right sail shape the sprit angle would be close to the same angle as the mizzen sprit, there would be a lot less load on the top slide.


Alan is also correct with the zipper effect. Once the load went above the breaking strength of the top slide it would fail, passing all of the load to the next slide for it to fail and so on. By the time the rest broke there may have been enough slack introduced into in the sail for the next slide to quit breaking.


This is not to beat up on Bones because he just proved Murphy right again. "If it can happen it will".


Here is my first shot at solving the problem. The drawing on the left shows a cross section of the sail track with a standard slide like Bones and the rest of us have. The one on the right shows my heavy duty top slide. It is thicker and has an eyestrap screwed into the slide. Harken rates that eyestrap at 1600# breaking strength with 2 # 10 screws.


I intend to make a couple and test the breaking strength of a standard slide and then test the new one. We happen to have plenty of track, slides and eystraps.




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Umm. I have feelings about being the first ever to break sail slides or slugs on a Mk 17-3.   I rather have the euphoria of reaching Key Largo first in class or in fact the satisfaction of simply reaching there. 


Instead I will share with you what I can about the incident that forced these slides to break.  But first there are a couple of comments in preparing to make a couple of comments. While seemingly unrelated, in my thoughts, they play a major part in our boat prep and handling.

First, the picture Alan posted, one of my personal favorites, was staged at Pickwick Lake on the Tennessee River at the launch ramp which is well protected from wind. We had been out in gusty 20 mph winds and happy to test our reefing abilities.  In the photo the mizzon has not been taken down yet.  The main however had been lowered and then re-hoisted for purposes of the photo.  That may distort some of the ideas about tension on the sail et.al.


Second, I carry a lot of different spare parts but never considered sail slides.  As an aside sail sides from West Marine come in packs of four.  St. Petes only had one pack in the correct size.  Bradenton had another pack or two, but we wanted enough in spares so, my crew, Capt Kyle, also stopped at Sarasota to buy enough that we could have a sufficient aboundancy.  Fortunately we were planning on re-launching for the EC 2020 in Englewood.


Third, last year I wanted the boat to be halfway pretty.  This year I consider I am Groot as a tool. 


 Fourth, Capt Kyle and Capt Bones both come from a line of boating experiences from trawlers to running replica ships the Nina, and the Pinta around the country and many other experiences.  None however, have prepared us for anything like the CS 17 Mk3 nor the EC until 2017.


Fifth, and most important to Kyle and I is the boat itself.  This boat itself is like a professional third member of the crew.  We can always count on Groot to be there, to guide us and protect us--as long as we do nothing grossly stupid.  We have found, compared to our other experiences, this vessel requires a soft touch, a finesse of its sixteen little lines.  Now let's get this part right.  I am talking touch and finesse like a jockey on a 1500 lb thorough bred race horse at Church Hill Downs.  A fine touch here and there to let the horse know what to do and mostly accepting feedback from the horse that tells you what it needs.  My CS 17 mk3/1- Bones is like that.  Easy to sail fast and safely, but it takes a bit more knowledge and an easy hand to sail it FASTER, HARDER, HIGHER. I am in the learning stages and of course, in all things boat, the more you learn the less you know.


I am Groot is so strong and light it feels like I could run it into a brick wall and it would just bounce off and keep sailing.  Well WTF,  WE DID!  We tacked it into the concrete railroad trestle house just south of the Boca Grande Bridge due to a sudden gust curling around that small channel. The crew got re-positioned in the cockpit, but Groot shook it off as to say: "Please sir, may I have some more."


Here is how we broke the sail slugs.


We had a hard time this year getting off the beach and into the water at the start due to inefficient rollers. Once in the water I held the boat as Capt Kyle hoisted the pre-reefed sails.  The boat sails off and I am trying to get on board by holding on to the stern ladder but the boat was moving faster then I could get my foot, ladened with five layers of clothes, on the ladder.  Eventually I roll, fall, ooze and snake onto the boat.  Since I came over the stern, Capt Kyle slide into the crew spot in front of the mizzen and I took the helm.


The start of any sailing adventure for us involves a certain amount of controlled chaos.  This start may have been less controlled and more of a cluster____ then others due to the increasing wind as we got further away from the beach.  Having said that we also usually get what we called "settled" within the first five minutes or so with everything under control.


We are running directly downwind not caring so much the direction until we reach that mental and physical "settled" state. Part of being in our" non-settled" condition is to strap everything down pretty hard--OK, very hard especially in higher winds.  Since we are going directly downwind, while getting our stuff together, the only lines not tight are the running backstays.  The mizzen is out at about 90 degrees and the main is past the mast, hard on the relaxed running backstays, and spilling wind but not flopping or flogging--it is controlled. We feel settled enough to  take up a proper course for the end of Anna Maria Island.  We know we have to either tack all the way around or gybe to our new heading. We elect a controlled gybe since the boat handles so easily in a gybe.  Our  gybe consists of the crew taking a handful of sheet below the attachment on the sprit to dampen its swing across the centerline then release it into its new position in a continuation of reduced and controlled force.


I throw the helm over and have no visual memory until the sail comes up hard slowing quickly on the running back stay and a startling,  louder than normal, pop or snap but not as loud as a bang--but still loud.  we feel the boat is not accelerating properly.  We are slower.  It takes a couple of minutes for us to see the loose sail at the top.  We immediately start to work our way back to the beach Our progress is very slow and far off the wind.  We ended about a mile west of the starting beach.


 I do not know the specifics but what I have read on the previous posts are quite consistent with what we felt happened.  Everything was strapped down.  In a few more minutes of being settled we would have been re-evaluating our line tensions as we always seem to do and no doubt made adjustments.  I have learned much from this and the most obvious is to keep things moderately loose until we get our zen going.


Please feel free to comment on any aspect.  We are big people, we can handle the corrections and the disbelieving comments that we could be so ignorant of sailing such a wonderful vessel. 


I say it again. 


This is the best boat I have ever depended on to keep me safe.  This wonderful little craft will continue to teach me how to properly sail it.  I welcome all of your suggestions on how to sail my Core Sound 17 mk 3 also.  Thank you B&B for this boat that seems to want to be a part of me.


I have pictures of the sail slides I will try to enter in a following note if not here.

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Graham and Alan.  Based on your surprise at my breaking of slugs suggests to me you have insufficient experience for destruction testing of sail slides.  Perhaps you should send samples to me, a professional destroyer of slides, for a full range of trials.  :)  Bones

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  • 4 weeks later...

I may be a bit late for a contribution here but I had the same problem a few years ago. It turned out hat the shackles, which attach the sail to the slide, slid inside the slides eye to windward, thus gaining some leverage, which caused the break. As I had problems back then to buy replacement slides, I made one - to have at least the most important one - from aluminium. Later, I fashioned thin bolts going across the shackles that prevent the shackle from slidig too far. No breakage since then.

2020-03-18 00.17.45-1.jpg

2020-03-18 00.24.48.jpg

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  • 2 months later...


On 3/17/2020 at 3:28 PM, Alan Stewart said:

Here is a test slide Graham just made. Destructive testing to follow. 


Hey Alan- Did you guys ever do this testing, reach any conclusions, release new sail slides, etc?


If newer, beefier sail slides are recommended, would be happy to buy some of them 

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Sorry about not wrapping this up sooner. My shop built slides tested worst of all even though I had a larger cross section.  After I looked up the mechanical properties it was obvious why as it was nowhere near as strong. 


I was surprised that the slides that come on our sails tested better than the ones that we buy domestically. Who knows where any of this stuff originates from anymore?


We then searched the web and found the perfect slide right under our noses. It is a slide made out of stainless steel and coated with teflon for low friction. It looks exactly like our regular slides but black. It is a bit pricey at around $12.  I am not going to rush out and change Carlita's slides, as I have said bfore that I have never broken one. On bigger boats like Jays MF246 with larger sails and forces I will use them at the head and tack and at the reef points.




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While fiddling with some hardware I discovered that a Harken 073 eyestrap fits and slides surprisingly well in our sail track. I always have a couple of them in my handy repair kit and with a bit of lashing cord I can quickly make a repair and be back on my way if I should ever have a slide or two fail.


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