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Sail & Rigging - Servicing vintage hydraulic cylinders with Sixten Sandström
14 May 2016 - 17:37
Join Date: 01 July 2010
Posts: 48

Servicing vintage hydraulic cylinders with Sixten Sandström


Hi folks. I‘d just like to tell everyone here on the classicswan forum about a successful repair job on our NAVTEC integral backstay adjuster, done by Sixten Sandström in Finland. 

Our issues with the NAVTEC backstay adjuster have been coming up a few times, on and off over the years, since we (my wife and me) own 47/013. Back in 2002, we were already told by Reckmann / NAVTEC in Palma de Mallorca that our old integral adjuster was not serviceable anymore, offering a new one instead for some serious money… in 2008, we had the old one serviced successfully in New Zealand at Mc Rae hydraulics Whangarei, after a catastrophic failure between Galapagos and the Marquesas. In 2015 then, last summer, the integral pump failed with the cylinder still holding pressure. Bleeding the unit from air, as described in the manual, did nothing to cure the problem. After inquiring around unsuccessfully at a variety of professional hydraulic shops in Berlin / Germany, I contacted Matteo and Lars about this issue, and received the e-mail address of Sixten Sandström in Finland:

One mail later, I received the following reply:

»Thank you for your mail with a service request for the NAVTEC cylinder. It is still possible to service these cylinders as long as they are otherwise in good condition. I normally have the seals available so as long as there are no missing pieces or mechanical damagers it will be possible to do the service. Sometimes I find NAVTEC cylinders that have been repaired using incorrect seals or methods and thereby causing detrimental damage. I suggest that you send the cylinder to our address that you have correctly noted and then I will first do an inspection and let you know the status. I will insist on replacing all seals, including a complete disassembly / assembly as this is the only way to achieve a good and lasting result.«

OK. This sounded reassuring. I did send the NAVTEC adjuster to Finland, hoping for the best. With the lively e-mail exchange following the delivery to Finland, we learned quite a few things about these old hydraulic cylinders:

»I have just opened the cylinder and found that all relevant mechanical parts are in good condition and it can be serviced as planned. I note that the oil inside was contaminated with both particles and also mixed with a small quantity of water. Also, the piston seal was quite worn. The cylinder has been serviced before as the seals were of a different type and also some small damages and scratches from tooling…«

When I asked about any do it yourself methods with a spare set of seals from the locker, Sixten wrote:

»The service procedure is quite difficult for this model and suggest it is not be attempted without previous knowledge and experience of this particular design. There are many different seals, different non return valves, springs, etc and some special tools are required. The cylinder you have is in good condition and it is not expected to develop the same fault in the near future. For your information, during the final test procedure I have adjusted the pressure release valve to 3000 psi as it is the standard setting.«

Then we received a very reasonable invoice (especially as compared to a replacement), with this note:

»I have surely spent too many hours on the service, and the materials become expensive as they are not available as a kit but have to be collected separately.«

Shortly afterwards, we held the package in our hands. The cylinder inside was beautifully padded. Before delivery, we received this e-mail:

»I have tried to protect all the sensitive parts for the transport and hope it will arrive well and without any damage. Once you open the package, you will note that the handle for the pump still needs to be installed and locked in place with the small locking screw. I have replaced the locking screw for the handle with a metric M5 grub screw so please use a metric allen key for this. Also for the release valve knob there is the same type of M5 grub screw. The cylinder piston is currently pumped all the way in for the transport and as you know it takes some effort to manually extend it open all the way again. The reason for the slow extension is that all the oil has to pass thru long steel tube with a very small hole of approx 1,5 mm.«

Yesterday (May 10th / 2016), my wife and me finally reassembled everything on board the VERA, and tensioned the rig to the max for quite some time. The cylinder holds the pressure 100%, and the manual pump works perfectly smooth now. The unit is clean, polished and shiny, has a new valve knob and a new manometer. A great service job, done to the highest standards on vintage NAVTEC hydraulic equipment, 35+ years old.

When I asked Sixten, if he would accept similar repair jobs from other vintage Swan owners, he wrote a few words about this:

»Not sure how many owners will be interested to do a similar service but I will be pleased to continue to do this type of service from time to time. In case there would be a larger number then there would be a need to improve the profitability somehow. It is better and preferred to do this type of work in the off season and not as urgent repairs, which tends to involve expensive shipments and some stress for all involved. I can suggest that if you know of similar old NAVTEC cylinders that are no longer used, I will be pleased to accept them as donations and have them as part of an exchange service program for other Swan owners. An exchange program would be replacing one that is repairable with a similar that has already been repaired.«


Sixten Sandström

Sector Technologies Ab

Nabbskatavagen 57

68570 Larsmo


Tel  +358 (0)40 5933519



Kind regards, Michael / SY VERA / 47-013


P.S. Below, you can see a pic with the NAVTC integral adjuster on VERA, taken in 2012...


14 May 2016 - 17:43
Join Date: 29 January 2007
Posts: 1018

Dear Michael,

wow, thanks for such a detailed description and congratulation for your commitment not to change the tensioner for a brand new one, I am not sure I'd had your patience!

Yes, I agree with you, Sixten is just terrific!

Fair winds!

matteo (47/069 Vanessa)

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