Finer Points of Sail Trim for the Cruiser...

[s/v Jedi]

Originally Posted by barnakiel

in the book you were so nice to quote (although probably in the other thread), what are they trying to teach us .... (picture attached ;-)))))

I feel to lazy to get it.... but half the book is rig tuning and half is sail tuning.

cheers,
Nick.

[barnakiel]

Originally Posted by s/v Jedi

I feel to lazy to get it.... but half the book is rig tuning and half is sail tuning.

cheers,
Nick.

;-)

According to Selden, driving a screwdriver across the barrel of the turnbuckle is a first class ticket to destroy it (the screw, not the screwdriver).

We do it with two wrenches instead.

b.

[sapster77]

Originally Posted by barnakiel

;-)

According to Selden, driving a screwdriver across the barrel of the turnbuckle is a first class ticket to destroy it (the screw, not the screwdriver).

We do it with two wrenches instead.

b.

Agreed! They are not designed to be adjusted that way.

[s/v Jedi]

I agree too, so I checked the book. It's a thin book and they don't explain how to tension a turnbuckle; it's to the point on how to trim/tune and why. The illustration is used to tell that it is not possible to over-tighten wire with short hand tools like showed on that picture. Hmmm... I can understand the reasoning to show a screwdriver too when you want to show short hand tools but the picture does show a method that isn't so good.... I wouldn't have put that picture in.

cheers,
Nick.

[Ex-Calif]

I just read an article about rig tensioning and how it can go wrong.

I have heard "old salts" say, "While sailing snug up the unloaded shrouds until the tension is taken up." This is wrong for so many reasons (primarily mast alignment) but the article talked about one I had not thought of.

With the shrouds unloaded it is possible to shorten the shroud so much that when it does go under tension it can overload the boat and fail the hull! Remember the load goes through the shrouds, into the chainplates and into the boat structure. Depending on the design these loads are transferred to the hull sides or in many designs into a "stronger" part of the boat. Do you understand how the loads are dispersed on your boat?

The other thing that happens is excessive compression loads on the mast, step and compression post if a deck stepped mast.

It would never occur to me to tension the rig while underway. Find a tuning guide for your mast/boat and follow it.

[s/v Jedi]

Hi Ex-Calif,

Indeed, the cap shrouds should be tensioned precisely using the percentage of the wire breaking strength. That percentage is different for each type of rig. The most important reason for that tension is to keep the masthead in position and preventing shock loading without overloading anything. It is indeed easy to over-tension a leeward shroud with normal handtools and when you tack and do the same thing on the other side you can go into that danger zone. But I think the old salts know how much too tension that leeward shroud so it is the people copying that practice without exactly knowing how to do it that get into trouble.

I always do the tensioning by measuring the wire stretch of a 2 meter section like explained in all the books. It's a bit more work, but only a couple of minutes extra.
The intermediate shrouds can only be done right while sailing. When I asked my rigger in Trinidad if the tension he put on the intermediates was correct, he asked me if I wanted to bet on that. I didn't of course but then he explained that he lost the bet 50% of the time because the best he can do is an estimated guess. So I had the tools at hand during the test sail and was happy I didn't bet because they were tensioned perfectly ;-)

ciao!
Nick.

[Eleven]

"Indeed, the cap shrouds should be tensioned precisely using the percentage of the wire breaking strength."
Caution there, all the rigging wires on my boat are the same size. That's sounds a bit over simplistic.
I did have one going slack when close hauled. From midships to cross trees, I tightened both (port and starboard) equal turns, struggling with the double threaded tie between swaged buckles to ensure even and equal turns. Now they don't go slack and the mast is still straight.
Does any one know a Prout experienced rigger? I have doubts that the set up I've got has ever been tensioned properly. And enough doubts about my own abilities to start fiddling.

[Joli]

We set the cap shrouds to (20 tons? I would have too look for sure in the log) with a hyd ram, shim it and forget it. From there we tune bottom to top d1's, d2's, d3's till it's straight.

[bastonjock]

im coming up to my third season as a sailor,im learning to sail on the Opposite bank of the North sea from Nick,I go out sometimes just to enjoy moving over the water then other times i will aim to improove my knowledge of sail trim.

from a relative newbies prospective and i dont have an experienced sailing buddy close to hand ,i learn from books.The last book that i bought on sail trim was so technical,it put me off learning the subject,it was more of an aeronautical engineers hand book than a book that learners could improve from.

It still gets confusing for me,i manage to get the ballance feeling okay yet the tell tails are not as they should be

Im looking out for a book that helps the "clueless" i dont want to learn aerodynamic principles,i just want to sail my boat with the sails properly trimmed.

[s/v Jedi]

bastonjock: well, you are on the right path because when you trim for balance, you rarely end up with the tell tails okay. In other words: trimmed for balance isn't the same as trimmed for optimal speed! I think on a racer they might get that right after weeks of tuning.

So you have to find that compromise where you are still balanced enough and go fast enough...

p.s. You can cross that North Sea and you will find Holland but not Nick because Nick is too glad to be out of that frozen misery and is in the tropics! ;-)

ciao!
Nick.

[bastonjock]

Nick,i am aiming to sell my current boat,its been a great boat for learning the basics but its not so good for crossing the North Sea.Then im going to test myself a bit more before making the run over,the dutch coast is about 150nm and ill probably be singlehandling.

Its all part of the build up to when i hopefully cast off the dock lines and head for warmer climates,ive also had enough of the cold

Btw I used to work as a diver on Smit Lloyd boats out of Denhelder

[barnakiel]

Well, to me, if the rig is pre-tensioned at the dock to the right tension and then the lee shrouds go slack in the seaway then something gives. But maybe this simple rule holds only for simple rigs like mine (one spreader, one top, two lowers, top forestay and a backstay.

I remember once met people on a boat with swept spreaders and a fractional rig, they swore by the fact (?) that the aft lowers had to be nearly slack when at the dock. Indeed, these boats made it around the world. Still, I read on in Selden's manual and failed to find any confirmation of the 'fact'.

Which makes me think that rigging is a science cum art.

b.

[s/v Jedi]

bastonjock: I would recommend you do the first crossing from Lowestoft to IJmuiden. It's exactly 100nm and exactly east and you don't have to compensate for currents because they cancel each other out magically.
My first crossing was from Oostende, Belgium to Harwich, which has more navigation difficulties ;-)

cheers,
Nick.

[s/v Jedi]

Barnie: you mean slack to relieve pressure while moored? That's a lot of work to do before heading out again!

cheers,
Nick.