J/44 backstay pressure

[Chris Campbell]

The pressure gauge on my hydraulic panel is no longer legible (can't even see the red indicator line, let alone the numbers), so I have no idea of how much pressure I'm putting on the backstay or vang. The vang I figure is a matter of common sense - don't tear the leech of the sail and all will be well. The backstay, though, I'm not used to the boat, so I don't know how much is a lot or even a little. There is a batten taped to the cylinder so that I can see where the stay end fitting is - but any lines or number that used to be on that batten are gone now, so it's another source of meaningless information to me.

I have looked up breaking strength for the back and forestays: 17,500 lbs., so I know not to exceed 4,500-5,000 lbs., but not how to know where that is. The last thing I want to do is break something from not knowing!

The only solution I've come up with is to borrow or buy the appropriate Loos gauge and measure it and mark the batten. Anyone have any other suggestions in case I can't find one to borrow?

Thanks,

Chris

[Bernie Coyne]

Chris:

 

The maker of the backstay is most likely SailTech https://www.sailtec.com/  It is a family run business by Bob and Judy Brehm in Wisconsin.  Call them  (920) 233-4242 and they can replace the gauge and refurbish the unit.

 

Bernie

J/46 #10 Mystic Rose

 

Bernie Coyne

Email: bernie...@outlook.com

Cell/text: 781-789-0762

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[Ed S]

+1 on Sailtec.  They are fantastic to work with.

[William Stellin]

 Early on I asked Rod Johnstone why my J/42 didn’t come with a backstay pressure gauge. He said they don’t tell you much. Better to tape a small ruler or stick to the unit and measure how much backstay bend you want. Bob at Sailtech told me there is a pressure relief feature that prevents you from breaking anything. I’ve never confirmed that. The taped stick with marks on it works great and everyone can see it from a distance. The gauge as I recall is quite expensive so I’ve just been happy with a marked stick. 

Bill #6

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From: j4x-owne...@googlegroups.com <j4x-owne...@googlegroups.com> on behalf of Ed S <esi...@gmail.com>
Sent: Saturday, May 21, 2022 4:36:06 PM

To: J/4X Owner's Group <j4x-owne...@googlegroups.com>

Subject: Re: [J/4X-owners] J/44 backstay pressure

 

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[William Stellin]

One personal note about Sailtech. They are very easy to work with albeit a little slow on rebuilds and very expensive. 

Bill #6

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Sent: Saturday, May 21, 2022 5:03:57 PM
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[Frederick deNapoli]

Ditto that

The J105 folks used different colored tapes which we’ll use on the 42 as well

Fred

Sent from my iPhone

On May 21, 2022, at 5:11 PM, William Stellin <wste...@hotmail.com> wrote:



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[Robert Kowalski]

I myself was told by a rigger “why not? If it breaks it was because you needed a new one.” Talking about how much pressure you give the back stay. With that in mind on one of my trips back up north, I hit the fastest I had ever sailed into the wind, with a jib and full main and the backstay pumped to the bitter end. Now I didn’t say it wasn’t scary.
I’m not a gauge man myself I find them to be liars and really what are they telling you? I’m a more looking at the sails type guy, watching that top telltale, and how much twist I have, and the mid section of the forestay, and what those middle telltales are saying.

just my two cents...

Bob

Sailing a course less traveled
Delightfully typed on a full keyboard on a mac

> On May 21, 2022, at 7:19 PM, Frederick deNapoli <phred...@gmail.com> wrote:
>
> Ditto that
> The J105 folks used different colored tapes which we’ll use on the 42 as well
> Fred
>
> Sent from my iPhone
>
>> On May 21, 2022, at 5:11 PM, William Stellin <wste...@hotmail.com> wrote:
>>
>> 
>> One personal note about Sailtech. They are very easy to work with albeit a little slow on rebuilds and very expensive.
>> Bill #6
>>
>> Get Outlook for iOS

>> From: j4x-owne...@googlegroups.com <j4x-owne...@googlegroups.com> on behalf of William Stellin <wste...@hotmail.com>
>> Sent: Saturday, May 21, 2022 5:03:57 PM
>> To: j4x-owne...@googlegroups.com <j4x-owne...@googlegroups.com>
>> Subject: Re: [J/4X-owners] J/44 backstay pressure
>>
>> Early on I asked Rod Johnstone why my J/42 didn’t come with a backstay pressure gauge. He said they don’t tell you much. Better to tape a small ruler or stick to the unit and measure how much backstay bend you want. Bob at Sailtech told me there is a pressure relief feature that prevents you from breaking anything. I’ve never confirmed that. The taped stick with marks on it works great and everyone can see it from a distance. The gauge as I recall is quite expensive so I’ve just been happy with a marked stick.
>> Bill #6
>>
>> Get Outlook for iOS

> To view this discussion on the web visit https://groups.google.com/d/msgid/j4x-owners-group/03455883-0989-4759-9220-A89CF6686847%40gmail.com.

[Chris Campbell]

Thanks all, great information, I'm definitely closer to having a good understanding than I was. Sounds like if I'm being reasonable I shouldn't be in danger of breaking things, and there's a chance that it's set up to prevent me from breaking things, even. Although my boat has a Navtec system - possibly J/Boats switched suppliers between the J/44 run and the J/42? - and I spoke with a friend who has a Cartwright 44 with the same system yesterday who told me that with this setup (-17 rod, 2" piston on the backstay) I should treat 3,000 lbs of hydraulic pressure (which equates to 6,000 lbs of backstay) as the maximum. So now I'll try to make a thick black "don't go past here!" mark on the batten at that point, just have to find it...

[rers...@netscape.net]

I hesitate to offer my 2 cents on this subject, being a humble cruiser and not a racer,  but on my J42 the mast is raked like a catamaran (easy to spot in a mooring field or marina by the angle of the mast).  The bendy mast means the backstay can be cranked down until you feel the effect.  It's an intuitive measure, you can feel it.  There's nothing to break.  Backstay extended, it's slack and floppy, backstay cranked down tight, the only hazard is the boom can get low enough to whack the top of your head in the cockpit and end your days.  It's pretty simple.

Reed Erskine J42 Cayenne #65

[William Stellin]

I agree, that’s my experience as well. 

Bill #6

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On May 22, 2022, at 11:22 AM, 'rers...@netscape.net' via J/4X Owner's Group <j4x-owne...@googlegroups.com> wrote:



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[Rod Deyo]

My two bits:

Masthead rigs generally use higher backstay tension than fractional rigs, but optimal tension crucially depends on precise sea and wind conditions, rig design, sail cut, etc., and requires going out and tuning the boat under various conditions. 

Adding backstay pressure as the wind rises lets you bend the mast to flatten and depower the main and also tighten the headstay to depower the jib and reduce jib sag. The amount of mast bend at a given pressure is controlled by the rig design, mast stiffness, mast pre-bend and shroud tension, and whether you use checkstays. Note that the  mast rake is typically static and controlled by mast step location, mast partners, and forestay length all being adjusted to achieve a desired weather helm (and resulting foil lift) - JBoats generally like a lot of mast rake!

As said, how much mast bend to use depends on a lot of factors: wind and sea conditions, masthead versus fractional rig, aluminum versus carbon mast, spreader design, forestay and shroud tension, and sail design and cut, e.g., North sails tend to be very different than Quantum sails.

On our racing J/35, with its Hall Spars aluminum masthead rig and straight spreaders, adding 4000-5000 psi backstay with the Navtec hydraulic system would bend the mast like a pretzel, collapsing it more than just bending it, even with maximum lower shroud and checkstay tension applied. We generally used 0-3000 psi in 0-40 knts for setting headstay tension,  with checkstays applied to set the resulting mast bend.

On our cruising J/42 with its Hall Spar carbon fractional rig, swept spreaders, and North Sails, we use significantly less backstay pressure - generally 1000-2000 psi is enough.

We have the mast step set fully forward, the mast centered at the partners with Spartite, and cap and lower shrouds set to 15% of breaking strength using a Loos gauge. The lower shroud tension significantly affects the pre-bend and mount of mastbend achieved at a given pressure, while cap shroud tension affects the the pre-bend and headstay tension. We also have checkstays available if needed, but have very rarely used them since the carbon mast is very stiff.

Hall Spars had a J42 rig tuning guide and North Sails a J/120 tuning guide that are useful staring points.

Rod Deyo

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[Chris Campbell]

Fabulous information, thanks!

Our last boat was fractional with runners and checks, and we never really used the checks since we could use the runners to control forestay tension and the backstay to control mast bend. On the masthead 44 we'll be using backstay to control forestay and bend, and checks to reduce bend in the middle wind range when we have enough power to start pointing higher but don't yet need to flatten the main. It'll seem a little strange to actually loosen a line to depower further (the checkstay), but it should work nicely.

Regarding how much backstay is too much, another friend has pointed out that since I'm coming from a 10,000 lb. boat I'm more likely to underestimate how much strain can be used than overestimate, which is a valid statement (everything on this boat seems high load!), so I'll just keep an eye on things and if I'm ever really scared start reducing sail. I will likely also put a gauge inline on the hydraulic line to the backstay cylinder, just for peace of mind - but there's not a rush for that - there are a bunch of other jobs to get off the list first.

Thanks for all of the input, it is really nice to be part of such an active and thoughtful group.

Cheers,

Chris

[gale...@gmail.com]

FYI: I just had my seemingly original 2001 SailTec unit rebuilt at Buzzards Bay Boatworks. New seals and a new piston for about $1k. Was leaking oil. All good now.

I also have a batten with 1" marks to set backstay tension. I have an aluminum mast and wondering how many inches should I consider as max? I normally do 4-5 in strong winds. Sounds like I could do more??

Galen

Tango J42