Hydraulic Backstay Adjustser Use

jviss

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Feb 5, 2004
6,745
Tartan 3800 20 Westport, MA
I'm posting in this forum as I think more racers would care and know about managing backstay tension than casual cruisers.

I have a Tartan 3800 with a Sailtec integral hydraulic backstay tensioner. I have no idea how to use it! I searched, and only found maintenance and troubleshooting docs from Sailtec, like this:

https://www.sailtec.com/images/docs/Hydraulic_Integral_Owners_Manual_10_Pages_2019_SAILTEC.pdf

There's a pressure gauge on it. (Hard to read, because of location.) I can't get my Loos tension gauge onto the backstay proper, as it's too high up; this has a split backstay, and the tensioner os on one leg.

I'd like to be able to tension the headstay in a blow, relax it going downwind, and so on, but at the same time, I don't want to break the rig.

Any help is much appreciated.

Thanks,

jv
 
May 20, 2016
3,014
Catalina 36 MK1 94 Everett, WA
Tighten up going to wind, let it off going down. How much?? You’ll have to play with it at different wind conditions.
 

Ted

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Jan 26, 2005
1,254
C&C 110 Bay Shore, Long Island, NY
I have a Harken integral hydraulic backstay adjuster on my boat but the principles of use are the same as the Sailtec unit. Even though you are having difficulty reading the gauge, try to get a good look at it at least one time while you make some adjustments.

Measure the diameter of your upper backstay and the split portion too. Look up the breaking strength of both of them. For calculating maximum loads, use the figures for the weakest part of your backstay. You can safely apply 20-25% of the breaking strength to your backstay. Since you have a split backstay, the maximum force applied by the hydraulic backstay adjuster should only be half of that figure. Pump up the adjuster until the gauge reads half of the breaking strength number. That will be the maximum amount of tension you should safely put on the backstay. After doing that, you can duplicate that setting by looking at how much of the hydraulic adjuster rod is exposed. You can fasten a reference batten to the stationary portion of the hydraulic adjuster with marks on it indicating maximum tension and other settings so you don't have to look at the gauge any more. The Harken adjuster has a built in pressure relief valve that prevents you from over tensioning the backstay but I’m not sure if the Sailtec unit has one.

If you have a very flexible mast, you may never want to apply maximum backstay tension. Your mast may bend more than you want it to before you achieve a tight headstay. You have to look to see how flat your main is getting as well as how much sag you have taken out of the headstay. From here on it's a matter of tweaking the rig to achieve proper sail shape as the designer intended and the conditions demand.
 
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jviss

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Feb 5, 2004
6,745
Tartan 3800 20 Westport, MA
What do you think the range would be, form a strong blow, close hauled (tightest) to a lazy, downwind run (loosest, I guess)?
Adding @Jackdaw , the racer, to see if he might contribute to my education on this.
 
Oct 26, 2008
6,045
Catalina 320 Barnegat, NJ
This is a masthead rig, right? I might be wrong but I believe that the tension on your fore stay is going to equal the tension on your backstay at every setting of the backstay adjustment. You can use the loos gauge on your forestay to determine the backstay tension. If the stay diameters are equal, then you have direct correlation. If the backstay is a different diameter, then you would need to determine the percentage of breaking strength by calculation.

But also, if you have a pressure gauge on one of the splits, I think you can determine the tension above the split. The splits will be equally loaded at half the load above the split. Then just calculate based on wire diameter.
 
Nov 8, 2010
11,386
Beneteau First 36.7 & 260 Minneapolis MN & Bayfield WI
I would use your forestay as a guide.. shake it in a circle with the sail furled to measure sag. On a boat your size I'd expect to be able to shake it so it made a circle of probably a foot (sag) in the middle. That is your light airs setting. In expected breeze, down to a few inches. As others note, experiment. But never rod tight. The size of your sail and how it was cut will factor.

To measure and create repeatable settings, attach/tape a thin fiberglass wand (like a modern tent pole) to the cylinder, extending upwards. Place a tape mark on the moving part of the backstay, and mark the range on the wand. This is your visual indicator of adjustment range.
 

jviss

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Feb 5, 2004
6,745
Tartan 3800 20 Westport, MA

jviss

.
Feb 5, 2004
6,745
Tartan 3800 20 Westport, MA
I would use your forestay as a guide.. shake it in a circle with the sail furled to measure sag. On a boat your size I'd expect to be able to shake it so it made a circle of probably a foot (sag) in the middle. That is your light airs setting. In expected breeze, down to a few inches. As others note, experiment. But never rod tight. The size of your sail and how it was cut will factor.

To measure and create repeatable settings, attach/tape a thin fiberglass wand (like a modern tent pole) to the cylinder, extending upwards. Place a tape mark on the moving part of the backstay, and mark the range on the wand. This is your visual indicator of adjustment range.
Perfect, thank you. I plan to do all you suggest. Funny that these adjusters don't have a wand, as this is what others have suggested, as well.
 

Ted

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Jan 26, 2005
1,254
C&C 110 Bay Shore, Long Island, NY
Is the pressure gauge on the adjuster calibrated to stay tension?
The gauge on the hydraulic adjuster is calabrated to measure pounds of tension whereas a loos tension gauge will indicate percentage of breaking strength of the stay that it's connected to. Using round numbers, let's assume that your backstay has a breaking strength of 8000 lbs. The maximum safe working load would be 25% of that or 2000 lbs. The gauge on the adjuster that is attached to one of the legs of your split backstay should not exceed 1000 lbs. because the load on each of the lower legs is half of the load on the upper portion.

The cut (luff curve) of your main and headsail will determine how much you should bend your mast or straighten your headstay. The headstay will always have some sag. It will increase as the wind speed increases.
 

jviss

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Feb 5, 2004
6,745
Tartan 3800 20 Westport, MA
FWIW, my forestay and backstay are both 5/16" 1x19 wire. According to Hayne Enterprises' chart, the breaking strength is 10600 lb. So, at 25% ÷ 2 = 1325 lb.

I don't have the unit in front of me, but my recollection is that the scale is marked in 1000 psi major increments, form 0 to 5000. So, 1350 would be pretty close to the bottom of the scale. Does this make sense?

I can see if the unit was connected directly to the backstay, so you'd max out at about 2500, which is half scale. With the split, only half that, and you're not using a lot of the pressure scale, and hence, suffer lower resolution.

I wonder if I can get a replacement pressure gauge that reads 1500 or 2000 psi, full scale.
 
Oct 26, 2008
6,045
Catalina 320 Barnegat, NJ
Well, first … the cross-sectional area of a 5/16" wire is about 0.0767 si but the cross-sectional area of 19 strands is surely something different. But let's say the area is roughly .0767 si That would mean the tension at breaking strength would be about 138,000 psi and at 25% /2 it would be about 17,250 psi. I doubt the gauge is measuring the tension in the wire (it would need to know the exact cross-sectional area). It must be reading a pressure of some kind that is unrelated. You would need more info about the pressure gauge to find out what it is measuring and how to translate that to the wire tension.

Apparently the gauge is not just measuring tension in pounds?
 
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jviss

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Feb 5, 2004
6,745
Tartan 3800 20 Westport, MA
I think it's indicating force, not psi. It only goes up to 5,000. I also assume it's enough to tension the backstay without a split. I don't know what the relief valve is set for.
 
Oct 26, 2008
6,045
Catalina 320 Barnegat, NJ
The Loos gauge is calibrated to convert the force required to bend the wire over an established distance into a percentage of strength based on the wire diameter (roughly speaking). It can't be all that scientific or accurate, but it is good enough for sailors to get a pretty good idea.
 
Oct 26, 2008
6,045
Catalina 320 Barnegat, NJ
I think it's indicating force, not psi. It only goes up to 5,000. I also assume it's enough to tension the backstay without a split. I don't know what the relief valve is set for.
That makes more sense. Remember that your wire is already in tension. It is probably just able to apply enough force to make a safe incremental change. I'd use the rough parameters that Jackdow established and note the force readings and use that as a starting point.
 

jviss

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Feb 5, 2004
6,745
Tartan 3800 20 Westport, MA
The Loos gauge is remarkably accurate. One can also get a superbly accurate measure of tension by measuring the elongation, over about 1 meter.

Come to think of it, I can calibrate the adjuster with the Loos gauge! Convert the percent breaking back into pounds, compare to the pressure gauge, etc.

Thanks for making me think of that!
 
Nov 8, 2010
11,386
Beneteau First 36.7 & 260 Minneapolis MN & Bayfield WI
That makes more sense. Remember that your wire is already in tension. It is probably just able to apply enough force to make a safe incremental change. I'd use the rough parameters that Jackdow established and note the force readings and use that as a starting point.
Yes and remember; the parameters that I described are the GOAL - creating the correct sail shape via tension. The reading from a Loos gauge is simply measuring that. Unless you know what you actually want, this is the way to proceed. Once you have the range, you can measure it to repeat it, say after you take your rig down etc. But most will use the want and tape method, and put the Loos back in the garage for the season.
 

jviss

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Feb 5, 2004
6,745
Tartan 3800 20 Westport, MA
But most will use the want and tape method, and put the Loos back in the garage for the season.
Makes sense. Now to come up with a nice looking wand design...unless you know of one that can be purchased?
 

jviss

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Feb 5, 2004
6,745
Tartan 3800 20 Westport, MA
Whoops, don't google for images with the term "backstay tension scale wand" at work; you're going to get lots of pics of what were once called "marital aids."
 
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Ted

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Jan 26, 2005
1,254
C&C 110 Bay Shore, Long Island, NY
Whoops, don't google for images with the term "backstay tension scale wand" at work; you're going to get lots of pics of what were once called "marital aids."
I got called out by my wife while doing a google search for snatch blocks.

In my previous example I was using approximate breaking strength figures for a 1/4" diameter wire stay. Your 10,600 lb. breaking strength for 5/16" wire sounds correct.

If you don't want to use the batten method, you can put a piece of colored tape around the movable rod portion of the adjuster at the point of maximum tension. The taped rod should not be allowed to go into the adjuster. It will only indicate maximum tension.
 
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