Lee shore. These two words have struck terror into the hearts of sailors for centuries. And justifiably too, since it is generally not the sea that kills sailors but the hard bits around the edges.
Surviving A Lee Shore
Reading Time: 4 minutesThe Offshore Voyaging Reference Site
Lee shore. These two words have struck terror into the hearts of sailors for centuries. And justifiably too, since it is generally not the sea that kills sailors but the hard bits around the edges.
As I was reading this I was thinking “in-mast furling trysail?” However, I guess the vertical slot could make it difficult to retain rugged mast strength.
John, the antel track you are referring to; is it the 316ss track?
Hi Clint,
No, it’s their aluminium mast track designed for full battened sails and using cars with slippery plastic inserts, not ball bearings. Not sure of the model, in fact I don’t think they make it any more, but the system we have is very like what they now call the HS system.
I am specifying the slides on a storm Trysail for 1″ T-track. Paul Savage of Hathaway, Raymond and Reiser wanted to make them every 24″ with doubling at the head and tack. Boat is a 40,000 lb Trintella 47. You used slides webbed every 12″. What should I insist upon? Any recommendations?
Thanks.
Hi Charles,
I’m going to guess that 24″ should be just fine. Having said that, there is probably simply no way to know for sure—just too many variables to calculate properly. How strong are the slides? Will they use pressed in rings, or just pounded in eyes to attach them? How thick is the tabling at the luff? How will they be attached? (Should be webbed on, not shackled.)
One difficult to quantify variable is that each slide is subjected to a hell of a battering when the sale is being hoisted, before the luff comes tight, when loads are better distributed…but then again, when the sail is being hoisted it’s not drawing…
This highlights a big problem specifying storm trysails: Few people have one, and fewer still have ever used one, so the sample size to determine appropriate specification is vanishingly small.
So, the bottom line is, it all depends on how anal retentive you are. Me? I have slides every foot and a trysail that is as bomb proof as I can make it. I guess the ultimate question to ask yourself is “what am I going to do if a slide pulls out”.
It would seem the most ironic item of the sail inventory on which to take a shortcut.
No shortcuts are intended by me. I specified 12″ as per John, but the sailmaker, John Savage, insisted strongly on 24″. (And compromised on something in between. I’ll let you know what I get and how it looks and works.)
I insisted on 1″ track. One boat nearby put a fitting up the mast and one at the deck with wire stretched between and he runs his Trysail on the wire with hanks. This is meant to comply with Bermuda race requirements. But the loads on the ends, because of the geometry, are going to be tremendous, and it’s exactly the time not to have these fittings fail.
I concur concerning the end loads. I am not going for a trysail but rather a very deep reef on the main and a reefable staysail, a relatively rare choice, but one I feel comfortable with in a steel motorsailer. I look forward to hearing about your results, although I’m not sure how you’re going to test a trysail before you need one…perhaps in 30-40 knots?
The deck to mast wire sounds convenient, rather than correct, like a Highfield lever as a shortcut to make a sloop a cutter with a wire luff. If the point is to spread the enormous loads of a 60 knot wind on a scrap of taut sail, two points isn’t much of one.
Any experience using rivnuts to fasten hardware (trysail track) to aluminum mast?
Small boat (Contessa 26)
Thanks
Justin
Hi Justin,
As a general rule I like to see a trysail track attached to the mast with carefully threaded (sharp tap, right size sharp drill) stainless machine screws. I also like to see an aluminium backer plate bonded with plexus. So that would be my default recommendation
That said, with a small boat like this that has a thin walled mast, and assuming the backer plate is a problem due to access, I’m just not sure whether or not a pop rivet or rivnuts would be adequate. Just too many variables for me to have an opinion on that.
Also, I really don’t have any expertise in relative fastener strength. I would suggest seeing if Practical Sailor has any testing data on this (subscription required for their best stuff).
Anyone else have any solid knowledge on this. (No guesses please, a storm trysail track that fails is really bad news.)
Hi Justin, I generally try to avoid rivnuts if I can but acknowledge that they are sometimes the best solution. The beauty of them is that they provide threads in a surface that is too thin to otherwise thread. Of course, it is still effectively a blind rivet so if a similarly sized rivet would pull out of the material, this will pull out also. The real annoyance to me with these is that if the bolt ever corrodes/galls, then you can easily spin the rivnut in the hole and it is a real bear to drill one out, much worse than a rivet usually. Loctite is in order here for a few reasons but if you pick something too strong, you will find that you have to drill everything out just like rivets but that it will be even harder. If you decide to look at drilling and tapping or also looking at the bolted part of the rivnut installation, there are 4 failure modes that you need to consider: – The first one to check is always bolt tensile strength. This is simply a matter of the shank strength of the bolt versus the load on it. Bolts in stable joints are typically torqued so that they are at ~75% of shank yield strength. To prevent fatigue, you then need to make sure your maximum load is below this point (tension from torque is a bit inexact so you should leave some room here). There are times where you torque to lower values but it is because of one of the other factors. – Bolt thread strength. A good rule of thumb is that on a coarse bolt, 5 threads engaged is enough (3 is actually usually full strength) and on a fine one, 7 is enough. This is easy enough to calculate too based on tension, thread stress area, number of threads and material yield strength. – Mating thread strength. This is usually a much bigger deal as the mating threads are typically made out of a weaker material. If the material is the same or stronger, then the same rules of thumb apply but if it is weaker, you need to calculate it. On a mast, this is going to be your limiting factor, the wall is just too thin and it is a weaker material so you will be limited on the torque and corresponding tension you can apply. In these situations, you ideally have a locally thicker area of material or thread into something behind the material such as a nut with a proper backing plate. – Head strength which can mean a few things. For something like a socket head cap screw, this is not a worry in a properly designed joint but for something like a low head, button head, or flat head allen drive, this is a big deal. Sometimes the head is too weak for the tension applied and basically snaps off. More commonly, you are limited in how much… Read more »
Hi Eric,
Thanks very much for the fill on that. I learned a lot, as I always do from your comments. Confirms that me guessing would be a very poor thing to do.
Thanks for the link to the bolt torque calculator. However, the link is broken, since, as always seems to happen these days, the website has moved things around. The correct links are now:
https://www.futek.com/bolttorque/american
https://www.futek.com/bolttorque/metric
No experience, just some guesses (sorry John) and considerations.
When thinking on rivet nuts you are basically using rivets – regardless if there’s a second-level thread with bolts or not. The whole unit is a rivet that is blind-riveted to your mast.
As your mast is most probably aluminum the question of rivet material comes into play, you will most certainly avoid steel or SS as this is more noble on the electrical scale, and by time will eat your rivet holes (it doesn’t seem possible to me to place a blind rivet and successfully use an electrical isolator). So you are confined to aluminum and monel rivets.
You may want to compare the material characteristics of aluminum and monel, e.g. here: https://www.makeitfrom.com/compare/5052-H32-Aluminum/Monel-400-NiCu30Fe-2.4360-N04400-NA13 which will show that monel would be the superb alternative.
Then there is the issue mentioned by Eric that rivet nuts tend to spin when the bolt is somehow corroded/galled within the threads, so you might use a rivet nut with a hexagonal body but as far as I found out these are only available in steel…
If it were my mast I’d either go with the backer plate John suggests, or if not possible for what reason ever use the fattest monel rivets available. There really is no advantage to use a rivet nut in this case IMHO, you most certainly would not want to remove your trysail track again?
Hi.
I did not subscribe to the thread. Oops. First time posting a comment and my apologies for the late reply. Secondly, sorry for asking this same question somewhere else, when I went looking for answers again, now that I am involved in my spring commissioning.
Thanks Eric, Ernest, and John for your insights. It appears the large monel blind rivet approach will win out (, thoroughly coated in Tefgel. I had thought perhaps I could used a chaser line to pull a backer plate into place lining up top and bottom holes, but the curve of the extrusion would mean a possible gap.
Justin
The only other thought I had
The only other thought I had was relating to fastener spacing. Is there a tool for calculating the number of rivets needed based on expected load?
I have no intention of being out in 45+ knots, but after my 3rd reef, or if my main blows out, I like the idea of a redundant option in strong winds. I have yet to test the theory, but Carol Hasse argues the trysail makes for a more forgiving stabilizer sail too. With its highvis and lack of boom to flog around, I suspect that might be a sane alternative in light winds to, perhaps for motorsailing.
Justin
Hi Justin,
Spacing is all about how well the fasteners load share. Load sharing is based on relative stiffnesses of the mast and the track. Think about a stiff mast and a floppy track, in this case the load will be shared by somewhere between 1 and 2 fasteners. Then think about the track being super stiff and the mast being super flexible, the load will share very well across a large number of fasteners.
One of the workarounds for the issue of poor load sharing is to temporarily stiffen a section of the track. In practice this is usually done with a car that is stiff and of a significant length. An example of this is what is done with jib cars, the cars are often on the order of 2X the distance between fasteners. meaning that the load is well shared over 3+ fasteners (if your deck is flexible, it can actually be quite a few). On older wooden masts, I have seen the attachment of the track to the mast beefed up just in the area of the head of the sail where each reef will go but I don’t get the impression this is common.
Unfortunately, I don’t know of a quick and easy to use resource for this. I would start with the track supplier and see if they have installation guidelines, hopefully they have done some calculations that are relatively conservative that can be applied. I have not bought track often but it is usually predrilled and if it is marketed for the purpose, I would hope that they would have calculated the spacing with conservative assumptions but I can’t guarantee it.
Eric
Oddly, this (no holes) track was supplied by my sailmaker so will address the fastener spacing question with them. I’d prefer go with a predrilled track that was then anodized, seems like a sensible alternative so will enquire about this option too. Thanks for describing the forces involved
Justin
Dear John
I was re-referred to this page from your Boreal article today, reread it, and found that I had previously commented and therefore had signed up for notifications. But I see that this article was revised in February 2019, and my notifications were turned off. Would you kindly check to see if a revision in a page turns off further notifications?
It would also be nice to get notified of a page revision.
Thanks and best wishes,
Charles
Charles L Starke MD
s/v Dawnpiper
Hi Charles,
The notifications you are referring to only apply to added comments, not changes to the main text. This has come up before, but it’s hard to figure out how to build a notification system for changes that would not drive people crazy, for example getting an email any time we found a typo and fixed it would suck big time. That said, we are planning some improvements to the site this winter and are thinking about this challenge as part of that.
Dear John
Thanks so much! I also found that a revision turned off future notifications that I had signed up for. Can you keep notifications on a page turned on after a revision?
Thanks!
Best wishes
Charles
Hi Charles,
We can’t get into custom coding. Just don’t have the resources. That said, I’m near certain that the revision of the main text had no effect on the comment notifications.
A boat like our Oysters with in-mast furling with the push of a couple buttons offer infinite reefing options. The main and jibs can be safely furled in seconds from the safety of the cockpit. The DYS tri radial sails are constructed to have added strength as they furl in, so the staysail becomes the storm jib and the main can be furled to act as a storm sail. We’ve used them in this way on several occasions. There’s no need to leave the cockpit to go forward.
HI Kenneth,
That’s certainly one way to get the job done. That said, I prefer the simplicity, reliability and backup of a storm trysail, particularly since experience seems to show that push button complex gear that is reliant on electricity is the first to fail when things get really seriously stormy.
John,
The hydraulic and electric furling systems each have a manual back up system which we’ve needed to deploy on three occasions during an electrical failure over the past 9 years. It’s not a big deal to turn a little hand crank or winch handle. Meanwhile, we have the convenience of push button controls from the helm and cockpit to use the other 99.99 percent of the time.
Hi Kenneth,
That’s certainly true, that said, I still like the simplicity, backup, and reliability of a simple storm trysail.
Hi John,
very good points, thanks!
Do you have by any chance some photos of the track and cars for the trysail the way you had it rigged?
Many thanks
Hi George,
Only the shot already in the article. What was it that you wanted to know?
Hi John,
sorry, didn’t see your answer before.
I am interested how exactly the sail-track for the trysail is set up.
We were planning on a 4th reef to avoid the trysail, but the cost of the 4th reef is almost exactly the same as getting the trysail. Hence packing the main away when it gets nasty makes much more sense.
Many thanks
G
Hi George,
If you ask a specific question about our trysail setup I will try and answer it. And if you need more information on trysail size in realtions to reefs you will find it here: https://www.morganscloud.com/2014/11/26/reefs-how-many-and-how-deep/
This is making me re-evaluate my trysail track(riveted) How did you fit the backer the full length of the track, and ensure sufficient pressure for an adequate bond? It was installed by the first owner of the boat when he was doing the initial rig, and he had a heavy orange Dacron sail built. I recently got in touch and he still remembers (vaguely) having it done as he’s now almost 90 and his memory from 35 years ago is a bit fuzzy. He did note that he’d never deployed it. If I ever need it, I’d like to have full trust it will stay put, I’ll be dropping the mast and will be stripping and repainting/replacing hardware as needed so now would be the time if I need to pull the track and install better.
For Rivnuts. There are MUCH, MUCH better ones. I’d trust these aluminum ones in Aluminum. Per my old Wurth sales rep, they primarily supply them to repair shops dealing with the new aluminium Ford trucks. Not the cheapest, but worth it as quality is good and their sales reps are super helpful and have looked up/contacted manufacturers for unlisted specs upon request.
https://shop.wurth.ca/fasteners/rivets-rivnuts-accessories/rivnuts/knurled-rivnut-large-flange
Hi Star,
For a storm trysail track I would want a backer plate in aluminium preferably bedded in epoxy or possibly Plexus and use machine screws to attach. No question this is a tricky project, and one I have never done since both my masts came with storm trysail tracks installed with aluminium backer plates. Clearly the backer plate will need to be slid up from the bottom of the mast and the tricky part will be getting the first few fasteners in place. Access through halyard exit slots will help.
Anyway, clearly it’s doable given that mast builders do this, although sadly not often these days.