Hidden downside in beefing up new shrouds?

[skipmac]

Originally Posted by valhalla360

Can you provide a source for the 15% breaking strength?

While we have a much different boat, the manual for ours states a load in pounds of tension, not a percentage of breaking strength.

Are you maybe confusing an idea that you don't want to "exceed" 15% of the breaking strength?

Have to agree. Do not recall seeing any rig adjusting instructions that mention the breaking strength of the wire, just the lbs of tension. I think this is more likely a design consideration to address the correct wire strength in choosing the size to use for a certain size boat.

Likewise the claim that larger wire has to be tensioned more than smaller wire. A mast does not know what size wire is attached, only the lbs of force applied to the tang. Doesn't matter if that force comes from 1/4" or 1/2" wire. Now much larger wire that is run horizontally over a long distance, will contribute a downward force from the weight of the wire but in this case I think that factor would be insignificant.

Originally Posted by valhalla360

To the origianl question: It sounds like the original spec was overbuilt and no one has brought up a history of failures on these boats, so it's likely a waste of money.

Just guessing but that sounds good to me.

[ahun]

Very useful thread, indeed. I was considering to go up one size on my boat, when I am replacing the standing rigging next time, but not any more, I think. Just came to my mind that story I heard, when the boat owner was running around the boat in every gust to tighten up the leeward shrouds, backstay etc. until the hull cracked at the keel from the pressure on the mast.

[Dody]

Originally Posted by valhalla360

Can you provide a source for the 15% breaking strength?

While we have a much different boat, the manual for ours states a load in pounds of tension, not a percentage of breaking strength.

Are you maybe confusing an idea that you don't want to "exceed" 15% of the breaking strength?

To the origianl question: It sounds like the original spec was overbuilt and no one has brought up a history of failures on these boats, so it's likely a waste of money.

Hi Valhalla, definitely no confusing, there is plenty of books of course, but online-info for example from Selden, page 31 and 32: http://seldenmast.com/files/1416926327/595-540-E.pdf

Cheers Dody

[Dody]

Originally Posted by valhalla360

Can you provide a source for the 15% breaking strength?

While we have a much different boat, the manual for ours states a load in pounds of tension, not a percentage of breaking strength.

Are you maybe confusing an idea that you don't want to "exceed" 15% of the breaking strength?

To the origianl question: It sounds like the original spec was overbuilt and no one has brought up a history of failures on these boats, so it's likely a waste of money.

Hi valhalla360, definitely no confusing! I was using KG because I'm in Europe and we're more familiar with the metric system. You can do the same maths yourself in lbs: 3/16 has a max breaking strength of 4000 lbs, 1/4 has 6900 lbs in general.

There is plenty of books around, (my earlier post didn't get published, why ever...). Online information can be found on the website of Selden for example, have a look at page 31 and 32 "the Folding rule method". Will send the link in an extra post as this might have been the problem that it didn't get published.

Cheers Dody

[Dody]

and here's the link: http://seldenmast.com/files/1416926327/595-540-E.pdf

Cheers Dody

[Dody]

sorry, the thing with the links doesn't seem to work for me. Have a look at Selden's website. It's Seldenmast.com, klick the technical Information-button, there the Rigging-Instructions and Sailmakers Guide, then hints and advice and the manual comes up.

Cheers Dody

[Cadence]

Originally Posted by OrangeCrush

I'm working on replacing the shrouds and backstay on my Pearson 26 and I'm wondering if it makes sense to go up one diameter for overall strength and longevity, from 3/16 to 1/4. It has nearly twice the breaking strength but it's not that much more expensive.

A friend advised against it on the theory that you don't want the "weakest link" to move elsewhere on the boat, like the chainplates or bulkheads. I get this, but standing rigging is not like a shear pin and losing a rig is not exactly a small deal. Additional weight aloft and windage seem like they would be relatively insignificant on a rig this size.

I sail my boat a bit harder and farther than most P26s probably are. The original designers wanted 3/16 for a reason of course, but if part of that reason was cutting costs, would it make sense to beef them up bit now?

Any thoughts? Thanks in advance.

If the 3/16 has served you even though aging why change when replacing? Hopefully you will get years before it needs it again.

[hamburking]

I sail a Pearson 30. IMHO, the pearsons came with a robust rig to start with, no need to improve on a good thing. The strength of the cables is massive...its the fittings, pins, plates, etc that are suspect.

[rognvald]

Crush,
Since your boat was designed by a naval architect (Bill Shaw), I'm sure his measurements were properly sized for the intended use of the vessel--daysailer/coastal cruiser. If you intend to sail your vessel beyond its theoretical limits and intent, then you must do as Roger Taylor did with his Ming Mings' and completely rebuild the boat from the bottom up to be able to sail at greater physical limits. Very few sailors are capable of this type of construction and you'd be better to buy another boat to suit your new level of sailing.
A second thought concerning your original question is why do you have to beef up your shrouds if you are properly reefed? There is no point in over canvassing your boat unless you're a hard core racer with big pockets and prepared to pay dearly for your transgressions. We sailed our first "big" boat-- a small 25 foot prodiction daysailer in conditions on Lake Michigan in which 40 foot plus boats wouldn't sail. But, the vessel was structurally sound, well maintained and properly reefed for the conditions. There were no undue stresses on any part of the boat since it was properly tuned and its light displacement and aero-dynamic hull created a stable yet exciting platform on the water. Many times the boat you think you want is actually the one you own after you understand what it needs. Good luck and good sailing. Here's the link to Roger Taylor: www.thesimplesailor.com/

[Cadence]

Originally Posted by GordMay

1/4" wire will be about 70% heavier than 3/16".

Amazing! I had to check it myself and came up with near 80% I may have rounded nos.. Who would have thought.

[hellosailor]

It's a Pearson. Overall they built good strong boats.


I'd stick to the original, and just worry about doing regular inspections on the entire rig, including all the fittings that people mistakenly think will last forever.


And while you're at it...your rudder & rudder post is past due for some serious inspection, too. Stainless steel parts underwater never get enough attention.

[valhalla360]

Originally Posted by Dody

Hi valhalla360, definitely no confusing! I was using KG because I'm in Europe and we're more familiar with the metric system. You can do the same maths yourself in lbs: 3/16 has a max breaking strength of 4000 lbs, 1/4 has 6900 lbs in general.

There is plenty of books around, (my earlier post didn't get published, why ever...). Online information can be found on the website of Selden for example, have a look at page 31 and 32 "the Folding rule method". Will send the link in an extra post as this might have been the problem that it didn't get published.

Cheers Dody

Lbs/Kgs, I can work in either and the size of the stay makes no difference with either unit.

Yep, you are confusing things. They are saying how to measure 15% of breaking strength. In reading thru it, those are typical values.

I guarantee if you ask selden if the stays are doubled in strength, they won't be recommending you maintain 15% of breaking strength.

[Reefmagnet]

You could go 5 mm metric stuff if available. Just a little bigger diameter for that bit of extra strength and no other fittings should need changing.

[GrahamHO]

I understand that most rigging wire failures are due to corrosion in older wires. So if you are replacing with standard size wire you have eliminated that problem for several years. The others have said it all especially that the standard wires should support the weight of the boat. I haven't done the math on that but it is easy enough to look up safe working loads and the boat weight.

[roland stockham]

Can be good or not. Don't know your particular boat. Ideally the decision should be based on real numbers. You may want to increase rig size for two reasons. One is that extra weight aloft increases the role momentum. That means the boat gets knocked around less in a seaway. Basically it means that if you get hit by a breaking wave it will take more energy to knock the boat down. This can improve offshore performance but does need to be considered with the keel wt and other factors. If you overdo it you will loose stability and the ability to carry canvas. It is a modification from the designers speck to change the boats intended use.
The second factor is durability, particularly for offshore sailing where the bigger seas impose significant cyclic loads. Most stainless steel will suffer fatigue if loaded to more than 10% of break load so if your loading from roll pitch and sails exceeds 10% in typical offshore conditions you are going to get shorter rig life. If it doesn't you wont. The difference is why lots of heavyweight cruises are sailing around with 15-20yr old rigging with no problems while race boats need to replace it ever 3-5years and still get failures.
Both of these need a good understanding of boat/rig design, the particular boat and what the designer intended and designed for. It can, and often is, a good move in upgrading a boat for longer passages but unless you are comfortable with the design ideas you probably want to talk to a good professional rigger or better still the boats designer before deciding