tuning a single spreader, fractional rig.

floater

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admittedly not the best picture - but between the deck and the forestay attachment this rig appears ever so slightly inverted. This can be cured by adjusting the backstay (it is rigged with a decent block and tackle) - but still. If you let go the backstay, it doesn't seem right that the rig inverts.

this boat is new to me, and none of the rigging feels super tight. it seems to me that if I tighten the uppers - perhaps problem solved - but how should this relatively simple rig be properly tuned? the po did leave me with a rigging tension gauge - apparently he was goofing around with it..

Note that the spreaders are swept back. The uppers terminate near the forestay attachment, and the lowers right beneath the spreaders.

single spreader fractional rig.jpg

 
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SloopJonB

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Set it up with the tension gauge according to the instructions and see where you end up first.

If rigging feels a bit loose it's actually a lot loose. The old rule of thumb for wire was 15% of breaking strength - that's really tight.

Is the gauge a Loos? I've used them a time or two and they work pretty well - way better than doing it by eyeball and/or feel.

As an illustration, I once bought a cutter that had 13 stays in total. The rig looked good and the stays felt fairly equally tensioned but when I checked them with the Loos I found they varied from less that 5% to over 24%

 

mgs

canoeman
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If you really think the mast is inverted, tighten the shrouds. 
 

lowers will pull the mid section back. Uppers will help tighten the headstay

you might also be able to tighten the headstay if needed. 

 

floater

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If you really think the mast is inverted, tighten the shrouds. 
 

lowers will pull the mid section back. Uppers will help tighten the headstay

you might also be able to tighten the headstay if needed. 
its almost like I want to ease off on the forestay - oddly enough, the inverted section (it is quite slight) is right where the spreaders are..

 

floater

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Set it up with the tension gauge according to the instructions and see where you end up first.

If rigging feels a bit loose it's actually a lot loose. The old rule of thumb for wire was 15% of breaking strength - that's really tight.

Is the gauge a Loos? I've used them a time or two and they work pretty well - way better than doing it by eyeball and/or feel.

As an illustration, I once bought a cutter that had 13 stays in total. The rig looked good and the stays felt fairly equally tensioned but when I checked them with the Loos I found they varied from less that 5% to over 24%
um. instructions?

fuck. did I not ask the po for those? shit me. ;)

 
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SloopJonB

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Look on the Interweb.

Loos gauges have them right on them - just select the size of wire you are checking to see how much deflection is correct

 

floater

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Look on the Interweb.

Loos gauges have them right on them - just select the size of wire you are checking to see how much deflection is correct
so. tuning the rig is just about tension - is this possible? Somehow I assumed that geometry also played a role - as in length of stays..

 

SloopJonB

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A wire that is tensioned to 15% of B/S is at 15% whether it's 20' long or 40' long.

A longer wire will stretch more distance to get to that same 15% because stretch is a percentage of length.

So the longer wires will take more turns on the screw to reach that tension.

 

neuronz

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Rigs are tuned from top to bottom.

1. Connect the wires and set mast rake with the forestay. Hand-tighten the shrouds and make sure the mast is centered/vertical.

2. Tension the backstay to induce some bend and start tightening the uppers symmetrically by counting turns on the turnbuckles. Release the backstay if you want to check tension with the Loos and re-tighten before working in the turnbuckles. The mast should have significant prebend after this step, because you are going to remove bend in the next step.

3. Release the backstay and tighten the lowers symmetrically (same number of turns on each side). Make sure the mast stays straight athwartships. Correct sideways bend if necessary by releasing one and tensioning the opposite side. Continue tensioning for desired prebend. If the mast inverts at the spreaders there is too much tension in the lowers relative to the upper shrouds.

(4.) On your rig the shrouds control headstay tension since there is a long and bendy piece of mast between the headstay and the masthead. If you want more headstay tension you need to tighten your shrouds. Limiting the bend with the lowers is important to keep the mast from bending under compression from the headstay which will decrease your headstay tension.

 

mgs

canoeman
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its almost like I want to ease off on the forestay - oddly enough, the inverted section (it is quite slight) is right where the spreaders are..
Slack the headstay off then.  If you think it’s forward at the spreaders tighten the lowers up. 

 

Gouvernail

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Wow!!! We rig boats virtually every day and as I read all the posts above I didn’t see ANYTHING like I would write. So here goes...

Quick response.

If that rig is inverted, I suspect the lowers are too tight (.... with respect to EVERY other factor)

-//

How to tune that rig?

1. Loosen EVERYTHING until the mast is standing as a straight pole. (If the mast remains bent with everything sloppy, the extrusion is bent . For these directions, I will assume it is not bent ) 

2. As I have ZERO idea how much rake this particular boat needs to balance the helm, I would start out with the assumption it ought to set up like most other similar boats. I would would hand tighten their uppers and forestay so the mast  is centered side to side and leans back a little(I am going into this knowing I will have to take the boat for a ride to see how it sails but I would lean the mast back so the top is 15 to 30cm back from the base ( six inches to a foot for USA sailors) 

For centering I would cleat the main halyard so I would have to push down the shackle with about a couple kilos of force to touch the top of the gunwale. 
Then I would  try touching the shackle to the same spot on the other side if the boat. I might try touching two or three pairs of symmetrical spots on the boat until i would convince myself the tensions are about equal. 
(This is accomplished to perfection is you and a friend Each check and AFTER you have checked tell the other what you think. When you agree it is the same on both sides, it is) 

3. I would tighten the Uppers to about 200  kilos or 400 lbs or until there is about 3 to 9cm (2 or 3 inches)  of pre-bend. I would check by holding the bottom of  the main halyard  against the mast. The gap at the spreaders is the amount of pre-bend. (That  tension should be safe for eventual testing in about ten knots of breeze) 

4. I would tighten the lowers to bring the pre-bend back to about 2/3 of where it was with totally sloppy lowers. This might be about 150 kilos (300 lbs) but the function is the key NOT the tension number. 
The function of the lowers is to keep the middle of the mast from going further forward. When you load the forestay, the pre-bent mast will want to continue to bend. That bending would make the distance from the deck to the forestay attachment point shorter and the forestay would never get tight.

**The lowers control the tension of the the forestay 

5. The backstay ... it really has no function on this to until it is used to depower the rig. Pulling on the  backstay bends the mast ABOVE the forestay attachment point. (Yes, it does tighten the forestay a bit and it bends the mast a bit more forward at the spreaders...  and I could go on all day about the various subtleties including varying the rig tune for various wind conditions) 

Anyway, the backstay flattens the top section of the sail and opens the leech at the top of the sail and gets rid of the healing force when there is too much wind to effectively use the  full power of your sails. 
 

what do you do?? You see a puff coming and you grab the backstay line. As the puff hits you tighten the backstay to keep the boat upright. The rest of your sailplane stays trimmed for ultimate upwind sailing and you charge forward blasting past those fools who eased the traveler, closed the slot,  and quit pointing. 
 

The testing: Go for a ride. 
* If the leeward shrouds becomes horribly sloppy, tighten the rig. Rule of thumb ?? Tighten the uppers two full turns and tighten the lowers one and a half turns and try it again.

*If the boat has Lee helm, go back to step two. Your rig is already centered but you are going to lean the mast back some more and try again 

*If the boat has too much weather helm, AND YOU ARE KEEPING IT FLAT ENOUGH, you may wish to stand the mast up more vertically. 
 

Tension settings: A fractional rig set up to properly perform in 25 knots will be absurdly over tight for winds under 12 and will sail horribly.

A fractional rig set up loosely  enough for ultimate performance in five knots will be horribly overpowered and may even fold up and fall in big breeze. 
 

We generally set up our customers’ boats for 12 to 15 and give them instructions about how to mess with the rig to make it work better in other conditions. 
 

Whoever makes sails for your boat will usually be happy to give you a chart of rig tensions for various conditions. They want you to have great performance with their stuff and proper rig tension helps a lot. 
 

—- Left out... while sailing upwind, stand by the front of the mast and look up. The mast should not bend sideways. You may have to adjust the relative tensions between the uppers and lowers to straighten the mast.

If the mast bends to weather at the spreaders, tighten the uppers a bit and loosen the lowers a bit. 
It the mast sags to leeward at the spreaders, tighten the lowers a bit and ease the uppers a bit 

And.... check EVERYTHING on both tacks 

phooey... I was going for a sail an hour ago ... outta here !!! 

 

SloopJonB

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Gouv, I don't see anything in that where you use any kind of tension measuring tool on the wires.

Is that the case - are you saying thumb and eye is all you use?

If that's the case do you also tighten keel bolts with a wrench and a piece of pipe "until the suckers scream" or do you use a torque wrench?

 

Wright Way

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Gouv, I don't see anything in that where you use any kind of tension measuring tool on the wires.
Read 3 and 4 again, and the rest of the post for that matter.

Its all about setting the rig up to perform and bend like it should, different wind strengths = different tensions.

If you want to go ahead and tension your rig to xxx because the wire is yyy thick, good luck getting your mast to do anything useful. If you up your wire size what you going to do then? Bit like torquing your keel up as the hull material is crushing because you reckon the bolts can handle a higher torque.

Fractional rig a bit more technical than a power-pole, its shape and change in shape that matter.

 

mgs

canoeman
1,119
251
maine
Wow!!! We rig boats virtually every day and as I read all the posts above I didn’t see ANYTHING like I would write. So here goes...

Quick response.

If that rig is inverted, I suspect the lowers are too tight (.... with respect to EVERY other factor)

-//

How to tune that rig?

1. Loosen EVERYTHING until the mast is standing as a straight pole. (If the mast remains bent with everything sloppy, the extrusion is bent . For these directions, I will assume it is not bent ) 

2. As I have ZERO idea how much rake this particular boat needs to balance the helm, I would start out with the assumption it ought to set up like most other similar boats. I would would hand tighten their uppers and forestay so the mast  is centered side to side and leans back a little(I am going into this knowing I will have to take the boat for a ride to see how it sails but I would lean the mast back so the top is 15 to 30cm back from the base ( six inches to a foot for USA sailors) 

For centering I would cleat the main halyard so I would have to push down the shackle with about a couple kilos of force to touch the top of the gunwale. 
Then I would  try touching the shackle to the same spot on the other side if the boat. I might try touching two or three pairs of symmetrical spots on the boat until i would convince myself the tensions are about equal. 
(This is accomplished to perfection is you and a friend Each check and AFTER you have checked tell the other what you think. When you agree it is the same on both sides, it is) 

3. I would tighten the Uppers to about 200  kilos or 400 lbs or until there is about 3 to 9cm (2 or 3 inches)  of pre-bend. I would check by holding the bottom of  the main halyard  against the mast. The gap at the spreaders is the amount of pre-bend. (That  tension should be safe for eventual testing in about ten knots of breeze) 

4. I would tighten the lowers to bring the pre-bend back to about 2/3 of where it was with totally sloppy lowers. This might be about 150 kilos (300 lbs) but the function is the key NOT the tension number. 
The function of the lowers is to keep the middle of the mast from going further forward. When you load the forestay, the pre-bent mast will want to continue to bend. That bending would make the distance from the deck to the forestay attachment point shorter and the forestay would never get tight.

**The lowers control the tension of the the forestay 

5. The backstay ... it really has no function on this to until it is used to depower the rig. Pulling on the  backstay bends the mast ABOVE the forestay attachment point. (Yes, it does tighten the forestay a bit and it bends the mast a bit more forward at the spreaders...  and I could go on all day about the various subtleties including varying the rig tune for various wind conditions) 

Anyway, the backstay flattens the top section of the sail and opens the leech at the top of the sail and gets rid of the healing force when there is too much wind to effectively use the  full power of your sails. 
 

what do you do?? You see a puff coming and you grab the backstay line. As the puff hits you tighten the backstay to keep the boat upright. The rest of your sailplane stays trimmed for ultimate upwind sailing and you charge forward blasting past those fools who eased the traveler, closed the slot,  and quit pointing. 
 

The testing: Go for a ride. 
* If the leeward shrouds becomes horribly sloppy, tighten the rig. Rule of thumb ?? Tighten the uppers two full turns and tighten the lowers one and a half turns and try it again.

*If the boat has Lee helm, go back to step two. Your rig is already centered but you are going to lean the mast back some more and try again 

*If the boat has too much weather helm, AND YOU ARE KEEPING IT FLAT ENOUGH, you may wish to stand the mast up more vertically. 
 

Tension settings: A fractional rig set up to properly perform in 25 knots will be absurdly over tight for winds under 12 and will sail horribly.

A fractional rig set up loosely  enough for ultimate performance in five knots will be horribly overpowered and may even fold up and fall in big breeze. 
 

We generally set up our customers’ boats for 12 to 15 and give them instructions about how to mess with the rig to make it work better in other conditions. 
 

Whoever makes sails for your boat will usually be happy to give you a chart of rig tensions for various conditions. They want you to have great performance with their stuff and proper rig tension helps a lot. 
 

—- Left out... while sailing upwind, stand by the front of the mast and look up. The mast should not bend sideways. You may have to adjust the relative tensions between the uppers and lowers to straighten the mast.

If the mast bends to weather at the spreaders, tighten the uppers a bit and loosen the lowers a bit. 
It the mast sags to leeward at the spreaders, tighten the lowers a bit and ease the uppers a bit 

And.... check EVERYTHING on both tacks 

phooey... I was going for a sail an hour ago ... outta here !!! 
I’ll agree with this.
 

It seems from my comments that I thought the mast was inverted the other way. Must be a post solstice mind trick

 
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Gouvernail

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Gouv, I don't see anything in that where you use any kind of tension measuring tool on the wires.

Is that the case - are you saying thumb and eye is all you use?

If that's the case do you also tighten keel bolts with a wrench and a piece of pipe "until the suckers scream" or do you use a torque wrench?
To be honest?? Most Of the boats I handle can be competently rigged using “it feels about right.” I have a variety of gauges including a nifty antique one I like to bust out simply to see the looks on the faces of those observing me. 
 

For  a fractional rig like those on J-24 and J-29 the mast base position adds another layer I did not address above. For some reason I “just assumed” that boat’s  mast is deck stepped. I can’t really see in the photo. 
 

I have no idea how to measure the 200 kilo starting tension guess without a gauge. 
 

If it is a fractional rig, and I have the opportunity to sail the boat for a few hours in a variety of wind velocities, the guage serves a valuable bunch of purposes. 
**I can check to be certain I am not overtightening the rig. It is easy to crank on more tension than the rig and boat structure should be asked to handle. 
( note: on my J-22 and J-24 I have ALWAYS eased off some tension after a windy race day. Nothing good comes from storing a boat with a tight rig) 

** I can record the set up tensions so I can rapidly repeat a known previously successful  set up when the winds look similar 

**I can communicate with other sailors who can tell me why my speed was fine but my pointing was pathetic.. 

**I can write down how many turns I added or subtracted from one setting to another  and how that changed the tension. 

>>>Mostly, I set up the rig  so the mast bends the way I want it to bend so the available sails are most likely to drive the boat. The sailmaker usually provides a chart but the slightest change in luff curve or the relationship of wind velocity to wave height will change the very best tuning guide into nothing more than a general reference. 
 

€€€€€ Torquing keel  bolts. Whenever  I see torque numbers I wonder whether the torque numbers apply to well lubricated threads,  dry threads, a greased washer, boat sitting on keel, keel hanging, and whether somebody has done any real calculations.

The correct amount of torque is enough to keep the keel absolutely firm against the sump and is limited not just by the strength and stretching SS if the bolt but by the pressure necessary to deflect the sump bottom. 
 

translation: I have a few torque wrenches and when someone gives me credible information about torque settings, I use the tools and hope to thereby protect my savings from greedy lawyers and their clients. 

 

Gouvernail

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I’ll agree with this.
 

It seems from my comments that I thought the mast was inverted the other way. Must be a post solstice mind trick
THE DAYS ARE GETTING LONGER!!!! 
and... it was a great Christmas afternoon for an AERO ride. I had to share the lake with a half dozen Opti sailors, two inflatables carrying coaches, a couple coaches on kayaks, two passing runabouts, a pair of J-80s, a Columbia 9.6, a Hunter 31, a Catalina 22, an Ensign, and about three other boats I failed to identify and remember. 

 

SloopJonB

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Read 3 and 4 again, and the rest of the post for that matter.

Its all about setting the rig up to perform and bend like it should, different wind strengths = different tensions.

If you want to go ahead and tension your rig to xxx because the wire is yyy thick, good luck getting your mast to do anything useful. If you up your wire size what you going to do then? Bit like torquing your keel up as the hull material is crushing because you reckon the bolts can handle a higher torque.

Fractional rig a bit more technical than a power-pole, its shape and change in shape that matter.
I was thinking more along the line of port and starboard lowers having the same tension, both uppers equal - like that.

I've had masts that were straight and stayed that way on both tacks but there were big differences in the tension on opposing wires.

That can't be good.

 

floater

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Tension settings: A fractional rig set up to properly perform in 25 knots will be absurdly over tight for winds under 12 and will sail horribly.

Whoever makes sails for your boat will usually be happy to give you a chart of rig tensions for various conditions. They want you to have great performance with their stuff and proper rig tension helps a lot. 
A fractional rig set up loosely  enough for ultimate performance in five knots will be horribly overpowered and may even fold up and fall in big breeze. 
endless thanks for your post. bravo. I'll report back how it goes.

also, the sails pretty much never used Pineapples - but somehow (even) they screwed up on the foresail shape. I'm going to have to twing the clew down as the jib track too far aft. The main a fully battened (and crispy) Pineapple as well - can't wait to see it.. :)  

and I don't require ultimate performance. This is a cruising boat on SF bay (for the children - wink) so definitely sees variable conditions. big breeze prominently among them.

Fractional rig a bit more technical than a power-pole, its shape and change in shape that matter.
Power pole you say? My previous boat a Cal. So yeah, this bendy spar definitely something new. Which brings me to a related question.

Can the masthead support my weight (< 200 lb.) aloft? I have jumar'ed my way up to the forestay attachment. But the skinniness of this rig above that makes me wonder if its safe to climb all the way to the top?

 
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