Mast Tuning Guide - Pearson 10M??
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Peter Trunfio
Aug 9, 2016, 1:35:45 PM8/9/16
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I need to re-tune my rig. All the mast wedges have fallen out...and the mast is "floating" between the mast partners.
I need to loosen everything up, reinstall the mast wedges, and then tune the rigging.
I have a Loos gauge. Anyone have any specs or thoughts on the proper rigging tension for a 10M mast?
Dan Pfeiffer
Aug 9, 2016, 2:17:16 PM8/9/16
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On 2016-08-09 13:35, Peter Trunfio wrote:
> I need to re-tune my rig. All the mast wedges have fallen out...
> and the mast is "floating" between the mast partners.
>
> I need to loosen everything up, reinstall the mast wedges,
> and then tune the rigging.
>
> I have a Loos gauge. Anyone have any specs or thoughts on the
> proper rigging tension for a 10M mast?
>
> PMT
> I need to re-tune my rig. All the mast wedges have fallen out...
> and the mast is "floating" between the mast partners.
>
> I need to loosen everything up, reinstall the mast wedges,
> and then tune the rigging.
>
> I have a Loos gauge. Anyone have any specs or thoughts on the
> proper rigging tension for a 10M mast?
>
> PMT
If you think the rig is in proper tune now you could make measurements with your loos gauge and then restore to those tensions when you re-tune. That will get you back close to where you are. I would not worry much about headstay/backstay as that is less critical especially if you have a backstay adjuster.
This info may be helpful as well...
From the Pearson Current VOL. 6, #3 fall 2000
Tuning The Rig
by Bill Shaw
The following generally applies to cruising boats where once the rig is set to maintain a straight mast, no further adjustment is necessary.
Preparation
Make sure:
weights, sails, anchors, rodes, life rafts or dingys are in their normal place while sailing;
all halyards are set up tight;
fuel & water is either full or nearly empty;
the main boom is secured so that it cannot move. Locate it on the boat’s center line;
bilges are pumped out.
In addition, the mainsail and jib can be in a sail bag located F&A where their cg is located.
Tuning the Rig
The objective is to adjust rigging so that the mast is straight under most conditions. Shrouds and stays need not be tensioned beyond this amount.
Step l. Choose a day when wind is minimum and waves are small. Slack off the main halyard so that the mainsail shackle just clears the deck or cabin top. Measure the distance from the shackle to the after side of the mast and compare this with the number noted on the sail plan (most often found at the top of the mast on the drawing). If this dimension is missing, then a figure of 6" to l2" may be used. If the boat has a strong weather helm, the mast needs to be straightened up. If it has a lee helm, more rake is necessary. You should have a weather helm (not too much), at all times except in gusting conditions. Avoid too much weather helm—it slows the boat and when beating to windward, produces too much leeway. Under moderate conditions, the rudder angle should be about 3 degrees. As you see, this is an exercise in trial and error. Adding to the problem, adjustments of rake may make the headstay too tight or too slack. If either occurs, you need to match turn for turn. For example, if you slack the backstay 3 turns, then tighten the headstay 3 turns, etc. If possible, get a sailmaker to assist.
Step 2. Check that the mast is vertical. Again, using the main halyard as a measuring device, bring the main halyard shackle down to the deck at the upper shroud. Have someone cleat off the main halyard when the halyard is taut and the shackle is just touching the deck. Now toss the halyard over to the other side and without touching the cleated halyard, measure the distance from the bottom of the shackle to the deck. If the shackle touches the deck with ease, you will have to tighten the turnbuckle on the opposite side. You may have to do this several times until you get the same amount of tension on each side.
Step 3. Now it’s time to go to sea and adjust the shrouds so that the mast will remain straight on both tacks under moderate conditions (8-12 kn. of wind). As you sight up the aft side of the mast, it should appear straight on either tack. If it falls off to leeward at the top of the mast, tighten the windward upper shroud. If the top hooks to windward then slack the windward upper shroud. You may have to do this several times. Remember not to add more tension. If you tighten one shroud, then slack the other. Too much tension will cause the mast to bend.
Once you have a straight mast near the top, you may find it necessary to adjust the lower shrouds in a similar manner. When at rest the aft lowers should be quite slack and the forward lowers should be firm (but not overly so).
Step 4. The headstay sag should be done with your sailmaker on board. Designs which are raced, like the l0M or P30, really need an adjustable backstay with limits in order to avoid too much tension.
This info may be helpful as well...
From the Pearson Current VOL. 6, #3 fall 2000
Tuning The Rig
by Bill Shaw
The following generally applies to cruising boats where once the rig is set to maintain a straight mast, no further adjustment is necessary.
Preparation
Make sure:
weights, sails, anchors, rodes, life rafts or dingys are in their normal place while sailing;
all halyards are set up tight;
fuel & water is either full or nearly empty;
the main boom is secured so that it cannot move. Locate it on the boat’s center line;
bilges are pumped out.
In addition, the mainsail and jib can be in a sail bag located F&A where their cg is located.
Tuning the Rig
The objective is to adjust rigging so that the mast is straight under most conditions. Shrouds and stays need not be tensioned beyond this amount.
Step l. Choose a day when wind is minimum and waves are small. Slack off the main halyard so that the mainsail shackle just clears the deck or cabin top. Measure the distance from the shackle to the after side of the mast and compare this with the number noted on the sail plan (most often found at the top of the mast on the drawing). If this dimension is missing, then a figure of 6" to l2" may be used. If the boat has a strong weather helm, the mast needs to be straightened up. If it has a lee helm, more rake is necessary. You should have a weather helm (not too much), at all times except in gusting conditions. Avoid too much weather helm—it slows the boat and when beating to windward, produces too much leeway. Under moderate conditions, the rudder angle should be about 3 degrees. As you see, this is an exercise in trial and error. Adding to the problem, adjustments of rake may make the headstay too tight or too slack. If either occurs, you need to match turn for turn. For example, if you slack the backstay 3 turns, then tighten the headstay 3 turns, etc. If possible, get a sailmaker to assist.
Step 2. Check that the mast is vertical. Again, using the main halyard as a measuring device, bring the main halyard shackle down to the deck at the upper shroud. Have someone cleat off the main halyard when the halyard is taut and the shackle is just touching the deck. Now toss the halyard over to the other side and without touching the cleated halyard, measure the distance from the bottom of the shackle to the deck. If the shackle touches the deck with ease, you will have to tighten the turnbuckle on the opposite side. You may have to do this several times until you get the same amount of tension on each side.
Step 3. Now it’s time to go to sea and adjust the shrouds so that the mast will remain straight on both tacks under moderate conditions (8-12 kn. of wind). As you sight up the aft side of the mast, it should appear straight on either tack. If it falls off to leeward at the top of the mast, tighten the windward upper shroud. If the top hooks to windward then slack the windward upper shroud. You may have to do this several times. Remember not to add more tension. If you tighten one shroud, then slack the other. Too much tension will cause the mast to bend.
Once you have a straight mast near the top, you may find it necessary to adjust the lower shrouds in a similar manner. When at rest the aft lowers should be quite slack and the forward lowers should be firm (but not overly so).
Step 4. The headstay sag should be done with your sailmaker on board. Designs which are raced, like the l0M or P30, really need an adjustable backstay with limits in order to avoid too much tension.
Guy Johnson
Aug 9, 2016, 2:57:55 PM8/9/16
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Put the wedges back in, tension the rigging making sure the rig is straight.
you can get a feel for how tight the rig is by pulling on the shrouds. set them relatively tight.
Go sailing if the leeward shrouds are loose tighten a bit, tack and check the other side.
Each time you adjust sight up the mast and make sure it's straight.
You can affect pre bend with the lower forward shrouds.
Guy
Puffin 10M #6
From: peter....@gmail.com
Date: Tue, 9 Aug 2016 13:35:43 -0400
Subject: [pearson ] Mast Tuning Guide - Pearson 10M??
To: pearso...@googlegroups.com
From: peter....@gmail.com
Date: Tue, 9 Aug 2016 13:35:43 -0400
Subject: [pearson ] Mast Tuning Guide - Pearson 10M??
To: pearso...@googlegroups.com
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Michael Robinson
Aug 9, 2016, 3:44:56 PM8/9/16
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Pete: Here's one I did for the Pearson Flyer at Rocking the Boat.
You can plug in the 10Ms dimensions and the formulas should work.
Let me know if there are problems.
Regards,
Mike
Let me know if there are problems.
Regards,
Mike
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Peter Trunfio
Aug 10, 2016, 11:55:07 AM8/10/16
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Thanks Mike.
I took the liberty of creating another worksheet in the Excel file for the 10M (see attached).
I updated all the information...except...RM30.
What is RM30? It is not a formula in the spreadsheet. It was "hard-coded" as 30,000 for the Pearson Flyer.
But I have no idea what that is...so I left it at 30,000 for the 10M.
It appears that it is used to calculate the Shroud Load: =(RM30*1.5)/(Beam/2)
On Tue, Aug 9, 2016 at 3:44 PM, Michael Robinson <gosli...@gmail.com> wrote:
Pete: Here's one I did for the Pearson Flyer at Rocking the Boat. You can plug in the 10Ms dimensions and the formulas should work.
Let me know if there are problems.
Regards,
Mike
On 8/9/2016 1:35 PM, Peter Trunfio wrote:
--I need to re-tune my rig. All the mast wedges have fallen out...and the mast is "floating" between the mast partners.
I need to loosen everything up, reinstall the mast wedges, and then tune the rigging.
I have a Loos gauge. Anyone have any specs or thoughts on the proper rigging tension for a 10M mast?
You received this message because you are subscribed to the Google Groups "pearson-boats" group.
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Michael Robinson
Aug 10, 2016, 12:35:06 PM8/10/16
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It's a Righting Moment at 30 degrees of heel number. Look at Brion
Toss' book.
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Dan Pfeiffer
Aug 10, 2016, 2:40:30 PM8/10/16
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Now were talking...
RM30 = righting moment at 30 degrees heel as Mike said. For the 10M that figure should be more like 21,500 lbs, a bit lower than that for the Flyer. Using a higher figure leads to a more conservative rig with a larger safety factor for wire sizes.
How did I get 21,500? I derived it from USYRA data on the 10M. Righting moment is calculated from measurements ( e.g. incline tests) and given in the data for 2 and 25 degrees of heel. I extrapolated that to get a value for 30 degrees. See 10M data here:
http://dan.pfeiffer.net/10m/usyru_mhs.htm
Look at the stability data. I have more data on the 10M here:
http://dan.pfeiffer.net/10m/10minf.htm
And info on what all these numbers are here with a list of useful references:
http://dan.pfeiffer.net/boat/ratios.htm
I have Mikes spread sheet from a while back and tweaked it for the 10M and added some other bits. I also have a bunch of other spread sheets on the 10M rigging that I will attach in one excel file. The spread sheets reference several texts for calculations. Have a look. Lots of stuff, some of it may be right but I make no guarantees. Lots of formulas and cell linkage and weird little excel tricks I use to get excel to display in certain ways. May be confusing. It sometimes is to me unless I added notes which I did in some places.
Dan Pfeiffer
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