Disassembling old hydraulic backstay tensioner

[BlueCanoe]

An old hydraulic backstay tensioner came in a box of parts with my boat. I am going to need to replace the rigging anyways which was last done in the 2000s and was wanting to add this. I am wondering if anyone can point me to a manual for how to disassemble these things or if you have a recommendation on a shop that can rebuild them that would also be great.

I did remove the cap (unscrewed easily with a pin wrench). But can’t get the piston out and don’t want to try to force it. The rod doesn’t turn more than a few degrees side to side.. I think it may unscrew the inner sleeve tube.

The unit is an old Navtec unit but the data plate is missing.

 

[peaman]

A rigging shop could probably help with that.

 

[phildogginit]

Just a thought you may want to not put that back. I had a leaky one and the rigger removed it completely. It sits in box. We dont miss it. Something more to break that can also inflict damage on the rig if not used carefully .

 

[ConchyDug]

I've rebuilt a Sailtec adjuster and have the manuals. I can email them to you if you think it'll give you any insight how Navtec might've built theirs. The manufacturers don't like to freely give out the manuals but if you're persuasive they might. High strength loctite is used in them and has to be essentially burned out to undo the piston, unless there is something physically restricting it from sliding out. Pretty much standard practices for rebuilding a strut is all it takes.

I'll counter and say if you know how to use a backstay adjuster it's a huge performance enhancer for a sailboat. Yeah it's another maintenance item but what's another drop in the bucket of "maintenance items" on an old boat.

 

[Loren Beach]

In March of '25, I sent our leaking (external drips starting last year) to Lew in Seattle. He works independently rebuilding BS Adjusters, usually for Navtec, but will work on others as he finds time.
This was our SailTec adjuster, dating from well over a decade ago. Prior reference here: https://ericsonyachts.org/ie/ubs/servicing-a-sailtec-back-stay-adjuster.113/

This time it needed disassembly on a professional hydraulics bench by someone knowledgeable. Lew Townsend is one of the few guys doing this work, and when done I drove up to pick it up. It holds pressure now. It was interesting to observe his pressuring equipment and how he could demonstrate it holding 3K #. Scary numbers for an armature like me to contemplate, as we normally only run it up to about 1800 to 2K# when sailing to weather.

SailTec site: https://sailtec.com/products/hydraulic-integral-adjusters
Navtec: https://navtechydraulics.com/

Also, Lew told me that he considers the Navtec design to be slightly superior in some ways. (Navtec was the original BS adjuster on our Olson and on some larger Ericson's I have seen.)
So perhaps I should have had the old OEM Navtec unit rebuilt, oh so long ago. It's just more water (hydraulic oil?) under the bridge at this point.

If anyone wants Lew's number for texting, contact me privately.

 

[HerbertFriedman]

several years ago, I had my local boatyard rebuild my Navtek backstay adjuster, $400.

 

[toddster]

Last year, I had a mechanic "fix" my leaking Sailtec and he just changed it from "dripping" to "not working." I was able to get it working again with a lot of back and forth with Sailtec. They want you to send it back to them, but that wasn't a good option from Mexico - might as well have in the end, for all the time and money I spent getting parts shipped in. And now it's leaking again, but at least I have parts.

Sailtec manuals are... a bit special. They have completely different procedures for different variations of the same model, and limited communication skills.

For a 25+ y/o unit, biting the bullet and just getting a new one may be the best option. Although that may also involve a new backstay.

 

[Seth]

Just a thought you may want to not put that back. I had a leaky one and the rigger removed it completely. It sits in box. We dont miss it. Something more to break that can also inflict damage on the rig if not used carefully .

Respectfully disagree on this. They make a BIG difference in performance. Without an adjuster you probably need to keep the rig very tight to avoid excessive headstay sag in windy conditions. This not only hurts performance but the constant movement of the headstay and mast in waves creates wear and tear on the rigging and furling gear. Your only option to minimize this is a rig which is very tight all the time and will definitely slow you down in lighter conditions and reaching/running. Yes-hydraulics require some maintenance, but add safety and performance. Of course you could always rig up a mechanical backstay adjuster (the wheel style)-maybe that makes more sense but I wouldn’t sail a boat like this without some kind of adjuster which is powerful enough for the loads generated. 2 cents in the bucket. Happy holidays!

 

[TimTimmeh]

I had my navteck backstay rebuilt at a local hydraulic shop, they rebuild hydraulic rams for heavy equipment all day long and had no problem with it I think it was $200. I called the rigging shop previously and the didn't seem to confident.

 

[Slick470]

we use our sailtec adjuster pretty much every time we leave the slip. It's another useful tool for sail shaping that I'm glad we have. I primarily race, but even on day sails, it's allows me to de-power the rig to keep the boat a bit flatter depending on who is on board.

When we bought our boat the adjuster occasionally dripped and would slowly loose pressure. I called Sailtec and they recommended a certified repair shop on the east coast. We ended up sending mine and a friends adjuster to that shop at the same time. His came back fine and mine sprung another leak in a few months. Sent it back to the shop and after a bit he called and said he was sending it back to Sailtec. He told me that they can be finicky to repair and decided that he'd had enough issues with them that he asked Sailtec to stop recommending his shop for repairs.

For the Navtec ones, I have heard, but have no personal experience that a competent hydraulic shop can repair them.

 

[BlueCanoe]

I took another look at this thing and was able to get it apart very easily without tools. I was of course taking the wrong approach initially. The overall condition of the metal components is good but the oil is frothy and contaminated and the seals are junk.

 

[ConchyDug]

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This stuff is expensive but I'd definitely find something like it so you don't nick the seals/o-rings on reassembly. The one I did had some pretty thick o-rings that had to be slid over the threading on I.D. of the strut. I also use that same brand at work... pretty much the only way to "glue" seals/o-rings in place.