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Old 13-04-2010, 08:09   #1
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Ketch Rig Tuning

The main masthead rig is keel stepped, double in-line spreaders, split back stays, with a tratic to the mizzen.
The mizzen is masthead rig keel stepped, single swept spreader, with triatic to main.

Have a Loos & Co. PT-3 tension gauge and I know this is a "at the dock" base and the finial tuning is done under sail.

Could you suggest the tuning sequence of the shrouds? any suggestions would be appreciated.
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Old 13-04-2010, 09:43   #2
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I would tell you how I learnd to do it from Brian Toss but its better if you just buy his DVD....Best 20 bucks you'll ever spend!

Tuning Your Rig Dvd, Brion Toss
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Old 15-04-2010, 08:07   #3
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There's a great write up on this forum, do a search for "HOW TO ADJUST AND SET YOUR RIGGING"

The nutshell version is:
1) Tighten by hand the upper shrouds till the mast is straight.
2) Adjust mast rake with stays and backstay/triatic.
3) Tension upper shrouds to 15% breaking load
4) Adjust mast pre-bend
5) Adjust back stay movement to not more than 2% mast length
6) Adjust lower shrouds while sailing
7) Adjust intermediates observing while sailing and adjusting at dock
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Old 15-04-2010, 10:33   #4
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Quote:
Originally Posted by Mango Bob View Post
There's a great write up on this forum, do a search for "HOW TO ADJUST AND SET YOUR RIGGING"...
All culled from the pages of the CruisersForum:

Hall Spars “Essential Rig Tuning Manual:
http://www.ycp.org.uy/tech_rules/hall_spars.pdf
www . ycp.org.uy/tech_rules/hall_spars.pdf

Seldon Mast “Hints & Advice on Tuning your Mast”
http://www.riggingandsails.com/pdf/selden-tuning.pdf
www . riggingandsails.com/pdf/selden-tuning.pdf

Loos “How to Use Tension Gauges”
How*to*use*Tension*Gauges*|*Loos*&*Co.*-*Cableware*Division
www. loosnaples.com/how-to-use-tension-gauges-pg-11.html
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Old 15-04-2010, 13:17   #5
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Okay, not so easy to find... I can't take credit for this but it's a great write up!

HOW TO ADJUST AND SET YOUR RIGGING:

We will do 3 basic adjustment types:

• Lateral Adjustment
• Longitudinal Adjustment
• Sailing (done later) Adjustment

1) Lateral Adjustment.

(NOTE: this has to be done in a day with no wind with the boat perfectly horizontal, shift weight if you have to, to balance the boat).

a) Install the mast, and make sure the intermediate and lower shrouds are lose, but attached.

b) Make sure the stays and back stays are attached but not over tightened. At this point you want the mast as vertical as possible.

c) Remove the boom, or lower it so its not pulling on the mast, we will need the topping lift.

d) If the mast is keel stepped, remove the centering thru deck bushings at this stage.

e) Once the mast is up and vertical by eye observation, take the topping lift or the main halyard and measure the distance from the top of the mast to the boat’s toe rail on port side. Repeat on starboard side, make sure the location of measure is symmetrical and at the same distance from the bow.
f) If the distances are not the same, tighten the side with the longest measurement.

g) Tighten the upper shrouds to a snug fit the same number of turns on each side, until the mast is perfectly centered.

2) Longitudinal Adjustment. (Rake)

(NOTE: this has to be done in a day with no wind with the boat perfectly horizontal, shift weight if you have to balance the boat).

Rake will help increase or decrease Weather helm. Aft Rake increases weather helm, improving pointing, forward rake does the opposite.

Normal rake is 1 to 2º degrees aft for cruiser boats and up to 4º deg aft for high performance racers.

a) Install a bucket with water under the boom by the mast.

b) Attach a heavy object to the main sail halyard and dip it the bucket but it should not touch the bottom of the bucket. (The bucket and water are used to dampen the swinging of the halyard.)

c) Measure P, which is the distance from the boom to the top of the mast.

d) Measure the distance from the halyard to the edge of the mast, at the gooseneck.

The distance should be as follows in the table:

Note, if you have a T shaped masthead, for halyard sheaves, add the distance of the T leg to mast to the above calculations.

Here is an example:

Our friend’s mast is 42 feet long, or 12,8 meters, therefore for:

0,5º Deg rake = 11,52 cm = 4,33 Inches
1º Deg rake = 22,4 cm = 8,66 Inches
2º Deg rake = 44,8 cm = 17,3 Inches
3º Deg rake = 67,2 cm = 26,3 Inches

He also had a mizzen mast, and in his case, the mizzen mast has 21 feet, or 6,4 meters, therefore, for:

0,5º Deg rake = 5,76 cm = 1,96 Inches
1º Deg rake = 11,2 cm = 4,33 Inches
2º Deg rake = 22,4 cm = 8,66 Inches
3º Deg rake = 33,6 cm = 12,99Inches

e) Measure the distance from the halyard to the edge of the mast, at the gooseneck.

f) Adjust the rake as needed, using the above table, using the stays and triatic also, (should you have a triatic), don’t forget that, ok?

g) Once all is where it should be, and the mast is where you want it, I would go with a rake of 1 º Deg for both masts for cruisers and 3% for racers.


h) Later on, once you sail, if you "feel" you need more rake use above numbers and adjust all again.

Note if you have a mizzen, for the triatic, you need a little help to get up there, but try to do it once with only one climb.


3)Dynamic Adjustment.

This will be obviously done later, if you feel you need more bend or better mast flexibility. See note further down, as at this stage we need to talk about tension in the rig.

The next step is therefore set the right shroud tension.

RIG TENSION
1) Shroud tension

We now need to tension the upper shrouds, so let’s tension them.
The values I calculated for our friend in the example are as follows:

a) All shrouds, including the upper, intermediate and lower are to be tensioned to 15% of the cable breaking load which in his case was:

3/16 cable the breaking load is 4850 lbs, so 15% of that is 727,5 Lbs

1/4 cable the breaking load is 7054 lbs, so 15% of that is 1058 Lbs

5/16 cable the breaking load is 12566 lbs, so 15% of that is 1885Lbs

b) The stays and triatic are to be set at 20 to 25% of the breaking load.

Use the same calculations above, to calculate the setting values, if you have a LOOS gauge, use it to set these tensions.

c) Now for the main shrouds, if you don’t have a Loos, or are just a cheap person, you can use a measuring tape. I did for many years.

You will need to attach a tape of at least 2 meters to the shroud, so that the zero or the beginning of the tape starts at the turnbuckle.

The rule is simple each 1mm of stretch means 5% of the breaking load, and that is valid for ANY CABLE IN A SHROUD, no matter what the diameter is!!!

So you want to have at least 3mm of "growing" or 0.11 inches stretch when you’re at the right tension, for 15% tension…cool huh??

Simple. Repeat the other side. Don’t do all 3 mm in one go. Do 1mm on each side and measure and adjust slowly so you don’t throw the mast off alignment.

Once the upper shrouds are tensioned, go to the next step.

2) Mast Pre bend

Once the masts are where you want them to be, and before we tension the shrouds, we need to set the masts curvature, or pre-bend.

For this attach the halyard that was in the bucket so it ends at the mast foot.

Now adjust the baby stay and or forestays so that the belly of the mast goes forward. Takes a few tries.
The max bend at rest should not exceed half of the mast diameter.

3) Max Mast bend (back stay and or triatic if you have one)

Tension the back stay on the mizzen first, (if you have one), so that the distance from the vertical halyard to the mast is half of the mast’s diameter (IMPORTANT - DO NOT EXCEED)

The mast bend when the back stay is pulled should never ever be more than 2% of the height of the mast from the top to the deck (not cabin). In our friends case with a 42 foot mast, at full back stay pull the mast top should not move back more than 10 inches. OK?

NOW IN THE WATER!! Dynamic Adjustment continuation of chapter 3 above.

OK so where are you going to set the intermediate and lower shrouds??

LOWERS

Easy. At dock, adjust the lowers so they are just tensile to the finger, use the Loos to set them equally port and starbord, they should be almost flexible at rest. Hard but not too much. These can only be adjusted once you sailed to measurel.

INTEMEDIATES

also at dock, Should have a flex of about ½ inch when at rest.

The lower shrouds adjustment

Now, when you go sailing, on the first tack, see if the mast is vertical and doesn’t bend sideways when you are on a tack.
Look from underneath and see if it’s straight.

If the mast bends to leeward, kind of like bellies to the low side, the lowers are too flexed.

Go to the lee side lower, and turn it a few turns, and note how many times you turned.

Then tack to the other side and see if its good. If its still bent, go on the lee side one and do the same number of turns plus a few more, repeat tacking and adjusting till all is good and straight.

The Intermediate shrouds adjustment

It’s the same as with the lowers, except now it’s the top part of the mast that "bends" to leeward if they are lose.

Those only adjust at the marina, ok??? You need to go up there.

So a recap:

1) Tighten by hand the upper shrouds till the mast is straight.
2) Adjust mast rake with stays and backstay/triatic.
3) Tension upper shrouds to 15% breaking load
4) Adjust mast pre-bend
5) Adjust back stay movement to not more than 2% mast length
6) Adjust lower shrouds while sailing
7) Adjust intermediates observing while sailing and adjusting at dock
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Old 28-04-2010, 20:32   #6
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In response to a suggestion, bought the DVD "TUNING YOUR RIG" by Master Rigger Brion Toss. Watched the whole show and really didn't see much about a "ketch" rig. So, I sent him a Email and below is his response. Thought it might help other "ketch" owners.

First, tune that main, ignoring the mizzen. Make sure that the mast is laterally centered, and raked properly. Bend as suitable. Once the main is done, the next trick is to set the mizzen’s rake. If the masts are parallel, they will look like they are leaning towards each other. A trick of the eye. So play with the mizzen rake until the two masts look parallel. You will probably need to slack the springstay (not triatic). This will be okay unless it is the sole forward support for the mizzen, in which case ease away carefully, and monitor mast stability. Especially important since, with almost all springstays, you’ll need to be aloft on the mizzen to adjust the stay. Depending on the stay configuration, you’ll also need to slack or take up on mizzen lower shrouds, intermediates, or uppers. You might want to look at the chapter on mizzen masts in the Rigger’s Apprentice for details of mizzen rigging, including calculating loads.
This brings us to the tune on the mizzen. Everything depends on configuration. If, for instance, you have athwartship spreaders, double lowers, and a masthead springstay, just tune as you would for a mainmast, then finish by snugging – just – the springstay. Remember, all this wire does is to keep the head of the mizzen from going aft. Not much load. Many mizzens also feature running backstays, and all these do is keep the mast from snapping forward, especially in a chop.
If you have a more complex configuration, like single lowers, aft-led uppers over raked spreaders, and forward-led intermediates, with the springstay connecting lower on the mast, backed up by jumper stays, then tuning gets really complicated. If this is the case, a consultation is in order.
It is also possible that you don’t even need the springstay, in which case you can save yourself some weight and windage up high. Don’t just disconnect it and hope for the best, but a lot of mizzens are designed to be independent of the main, and that is the best kind of mizzen, because there’s less weight aloft, and the two masts are tuned independently (see below).
It is also possible that you do need a springstay and that it is the wrong length. This happens a lot. If it happens to you, don’t put up with the mistake; send the thing down and make one the right length. If the mizzen is vital for keeping the mast up, set up some profound temporary stays before disconnect.
The only other semi-basic suggestion I can make is to consider installing a sheave in the mizzen masthead and making a running springstay. This line comes down inside the mast like a halyard, and makes off to a very clearly-labeled stopper. Then put a knot in the line so it can’t run far. The reason you might bother to do this is if you have a backstay adjuster on your mainmast. Without an easily adjusted springstay, tightening the main backstay slackens the springstay. So in the conditions you might want to keep that masthead still (going to weather in a breeze), it is waving about. But with a running springstay you just snug up after you tighten the main, and ease it before you loosen the main. Oh, and this running springstay (or any springstay, for that matter) can be made of high-modulus line, like New England’s T-900. Light, durable, easy to work with.

Ordinarily I would have sent you to “Spartalk” with this question, or set up a consultation, but I have a soft spot for Morgan’s, so I hope it’s useful for your owner’s group.
Fair leads,
Brion Toss
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