schroud tension

[winethief]

I have just purchased a PT-3 Loos & Co. tension gauge. Does anyone know what the shroud tension should be on a passport?

Many thanks,

George

Wind Thief

[psherwood]

Interesting question. I don't know that there is a single number that is
"right," although I think the Loos gauge includes some little document
that suggests tightening a certain shroud or stay to X percent of the
wire's breaking strength. Racers will tune their rigs tighter than
cruisers; some will want a little mast rake or bend and others won't. I
think P40s are designed for a vertical mast, no rake and no bend.

Adapted from something Matt Sponer, formerly of Mary Frances, wrote a
few years back:

- The mast should nearly always be straight. In stronger winds, maybe
a near gale, it's OK if the top of the mast falls off slightly in
the gusts-- so little that you have to sight up the mast to see it,
but can't see it when just looking at the mast.

- The mast should not flop forward and aft when pitching.

- The mast should not ever show any sort of S curve or curve between
spreader sets.

So: loosen the rigging up but keeping the mast straight and vertical.

Tighten everything round robin, counting turns on the forestay and
backstay and uppers and alternating between them, keeping the mast
straight. So 2 or 3 turns on the left side, then 2 or 3 on the right
side, and etc, keeping it all evenly tensioned, sighting up the mast
each time to make sure it's still straight.

Tension the uppers until they feel "about right," giving a couple inches
of deflection when pulled just so. Definitely not bar tight but tight
enough that all of the shrouds would vibrate with a low note if
you hit them with a tool.

Tension the intermediates to about 2/3 of the uppers.

Tension the lowers to about 1/3 of the uppers

The Loos gauge will help you see in the course of working through the
above steps how the tensions are increasing and changing as other
shrouds and stays are tightened.

If your floorboards start to stick and cabin doors don't close right,
you probably have too much tension on the shrouds.

Then go sailing, ideally beam reaching in a 15-knot breeze. Check the
leeward shrouds -- they should be looser than the windward shrouds, but
not so loose that they flop or swing or would produce a shock load when
you tack.

Run the reciprocal course and do the same thing.

Run back and forth beam reaching and checking the leeward shrouds until
you're satisfied that things are right.

Back at the dock again check the mast for vertical and straight.

Since you have the gauge, measure everything again and see what numbers
you get. If the mast is straight and you like the way the boat sails,
voilà, those are the magic numbers for your boat and your style of sailing.

Maybe there's another, hipper way to tune a rig. But that's what I know.

Phil
s/v Cynosure
on the hard, Marina Seca San Carlos

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6

[CAZ]

George,

I do not think shroud tension numbers exist. It comes down to common sense and using a safe loading well below the breaking strength of the cable. I have heard that the working load should not be more than 1/5 of the breaking strength. I had a rigger retension my shrouds and I found them to be way too tight. Why/ I was getting so much hull distortion that my bulkhead doors below would not close. And, Separation in teak joinery started to appear. I backed off each shroud to 1 - 1.5 inches of flex standing at shoulder height on deck. guess what? my doors began to close properly and the teak separations went back to normal. I believe the Passport is not a racing machine and should not emulate the tensions often found on race vessels. I would return the Loos Gauge.

thanks,

Bill Caz

P40, Beau Navire

Austin, TX  

[Donal Botkin]

Too much tension will bend your boat. P40's are relatively 'soft', so go light on the tension on the shrouds--particularly the lowers. I use a backstay tensioner as needed to keep the mast with a little bend for upwind work.
Donal

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View[+]Finder

Donal B. Botkin
1 Peninsula Road, Gate B
Belvedere, CA 94920

415 497-5411

[Steve Binari]

Hi George,

 

I also have a Loos gauge.  It would seem that the pros don't use them though.  The rigger that I used set the tensions under static conditions.  He adjusted the tensions by feel and eye to achieve a straight mast, with no bend.  He wanted to do a dynamic tune, but the stars never aligned to allow this.  The rigger's comments to me were that under high stress conditions (20 kt wind, full sails), the leeward shrouds should be a little slack, but not so loose as to be rattling.  The forestay should have 1% bow, or about 6" for the P40. 

 

I have a P40 with 5/16" rigging.  The rigger's static and my dynamic Loos values are listed below.  You can convert to pounds if needed. 

 

From bow to stern with the first column the port side.

 

Rigger's static tune:

Bow

18        19

25        22 (Cap)

18        22 ( Intermediate)

19        20

Backstay = 22

 

After doing the dynamic tune using the rigger's guidance:

 

Bow

22        21.5 

26        23.5

21        23.5

24        23.5

Backstay = 22

 

Please let me know what you measure.  Have fun!

 

Steve Binari

s/v Albireo

P40, #57, 1984

--

[Bill Schmidt]

Hey, George! Does the tension gauge work on rod rigging as well as wire? Are the tension values the same? Different?
Billy Manana

On 3/30/2015 7:41 PM, winethief wrote:

[Bill Schmidt]

Deja Vu! It's funny. Years ago, this question came up and I wrote as to
how I tune Wind Witch. Wind Witch is a P 40 with a forward v berth: With
the mast perfectly vertical such that a plumb line from the mast head to
the boom gooseneck hangs perfectly parallel to the mainsail mast track,
I tighten the backstay and forestay turnbuckles until the the door to
the head won't close. Then I back off the backstay turnbuckle about an
inch. Next I tighten both upper shrouds until the door to the forward
compartment won't close. Next I back off both upper shroud turnbuckles
until that door will close. Next I tighten all the lower shrouds until
they all "feel" right and have the same "ping" resonance when struck.
Then go sailing in moderate winds and readjust the lowers on each lee
side so that they are barely slack.
Both doors open (barely) w/o sticking. Under sail, mast appears
straight as sighted up the mainsail mast track on both tacks. I remember
the responses when I posted it.....everyone was hesitant to criticizes.
They were not sure whether I was joking or not. NOT. Some longstanding
member of the POA suggested I was doing it all wrong because I had rod
rigging and was distorting the boat too much. How about that......Michael?
Billy Manana

[Donal Botkin]

The P40 comes with a built-in shroud-tension gauge! Wow!
D

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<bill.vcf>

[Marty McOmber]

I am definitely trying The Billy method when the stick goes back in. We have the forward v birth as well. So should work perfectly.

Sent from my iPhone

[Bob Peahl]

One detail puzzles me- do you need to make sure all the crap in the boat is evenly distributed? And full tanks, right?

Sent from my iPhone

> On Mar 31, 2015, at 4:59 PM, Marty McOmber <mmco...@gmail.com> wrote:
>
> I am definitely trying The Billy method when the stick goes back in. We have the forward v birth as well. So should work perfectly.
>
> Sent from my iPhone
>
>> On Mar 31, 2015, at 1:05 PM, Donal Botkin <wcx...@gmail.com> wrote:
>>
>> The P40 comes with a built-in shroud-tension gauge! Wow!
>> D
>>
>> On Mar 31, 2015, at 09:57 , Bill Schmidt <bi...@windwitch.com> wrote:
>>

>> Deja Vu! It's funny. Years ago, this question came up and I wrote as to how I tune Wind Witch. Wind Witch is a P 40 with a forward v berth: With the mast perfectly vertical such that a plumb line from the mast head to the boom gooseneck hangs perfectly parallel to the mainsail mast track, I tighten the backstay and forestay turnbuckles until the the door to the head won't close. Then I back off the backstay turnbuckle about an inch. Next I tighten both upper shrouds until the door to the forward compartment won't close. Next I back off both upper shroud turnbuckles until that door will close.. Next I tighten all the lower shrouds until they all "feel" right and have the same "ping" resonance when struck. Then go sailing in moderate winds and readjust the lowers on each lee side so that they are barely slack.

[Bill Schmidt]

Yes, absolutely. In fact, if it isn't full of "all that crap", it
probably won't sail very well. As for the tanks, it depends if they are
leaking or not.
B.

[George Louis]

Wow! I can hardly wait to run down this list trying to cofigure a right triangle. Sure glad I have an electric secondary for the main halyard to get up that mast. My wife let me buy it! That’s what I said, my wife. Brilliant, however I am still, I think, goint to do a combination of the two approaches and see where it goes.

Many thanks for your input.

George Louis
s/v Wind Thief

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> <bill.vcf>

[John Baudendistel]

George ask the list how to make the right triangle, I bet there are 20+ ways. Let us know your results

John B

Thanks
John Baudendistel
Jo...@ets247.com
650.678.1459

[George Louis]

Thanks for the info. One question, what are the two columns of numbers. At this point I have tuned the backstay to 22 from 25 and the shrouds are all set at 20 until I can get out on the water and adjust.

Thanks,

George

[psherwood]

Here's what was recently posted.

Phil
s/v Cynosure
San Carlos / Seattle

-------- Forwarded Message --------
Subject: RE: [Passport] schroud tension
Date: Tue, 31 Mar 2015 07:11:20 -0400
From: Steve Binari <sbin....@gmail.com>
To: 'winethief' <glou...@gmail.com>, Passpor...@googlegroups.com



Hi George,

I also have a Loos gauge.It would seem that the pros don't use them
though.The rigger that I used set the tensions under static
conditions.He adjusted the tensions by feel and eye to achieve a
straight mast, with no bend.He wanted to do a dynamic tune, but the
stars never aligned to allow this.The rigger's comments to me were that

under high stress conditions (20 kt wind, full sails), the leeward
shrouds should be a little slack, but not so loose as to be rattling.The
forestay should have 1% bow, or about 6" for the P40.

I have a P40 with 5/16" rigging.The rigger's static and my dynamic Loos
values are listed below.You can convert to pounds if needed.

From bow to stern with the first column the port side.

Rigger's static tune:

Bow

18 19

25 22 (Cap)

18 22 ( Intermediate)

19 20

Backstay = 22

After doing the dynamic tune using the rigger's guidance:

Bow

22 21.5

26 23.5

21 23.5

24 23.5

Backstay = 22

Please let me know what you measure.Have fun!

Steve Binari

s/v Albireo

P40, #57, 1984

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