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Old 13-06-2007, 04:37   #16
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Ok...

I got the seals replaced at a local hydraulics shop. Now I am looking for a place to recharge with Nitrogen. The first attempt was with a big gas supplier that carries nitrogen. But they requested the technical manual or instructions for the equipment. Is there a way to get that info? If anyone has that kind of info pleeease let me know. Still I will continue my search.
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Old 13-06-2007, 05:18   #17
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They used a Autoclave to fill mine.
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Old 13-06-2007, 07:16   #18
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Just contacted a local fire extinguishers service place on the phone. They do have the nitrogen. I will take the unit to them and see if they have the appropriate fittings etc. Wish me luck. I was wondering. What do you do if your hydraulics fail in the middle of nowhere. There must be a service manual available on how to repair these units. In some cases it might be a life and death situation. Lets say for example your backstay seals fail. With the appropriate service manual and a spare set of seals one could get out of trouble and probably save your life.
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Old 13-06-2007, 13:41   #19
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Is there a fitting that allows you to charge the unit???

The vang is a gas strut, not a ram.
An hydraulic ram on a back stay is a different animal compleatly. They are not charged with nitrogen. A seal leaking will start of very slowly as a weep. At that stage you send it for service, not once it fails compleatly. The gas strut is under pressure. Once again you should have noticed the seal failing. The first problem that occurs is the strut no longer holds the weight of the boom. At this point the ram should be serviced. It should not be left to fail compleatly. So service at sea is not and should not be an issue.
If you do not have a charge fitting on the strut, then there is no way to recharge it with gas. This is done in a special chamber as Gunner has stated. If there is a fitting, then I would have it charged on the boat in place. Charge it till the boom is held in the correct position. Without knowing the exact factory pressure, this is going to be a suck and see exercise. But if you overcharge, you could run the risk of blowing the seal again. Honestly, I think you should have sent this to Navtec.
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Old 13-06-2007, 15:42   #20
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Alan, I think there's a way to use logic rather than guessing on the pressure. After all, hydraulics is just math. If you know the weight of the boom that the vang is supposed to be able to accomodate (i.e. 200 lbs, 500 lbs, whatever) and you know the size of the piston in the vang, it should be simple math (ha!) to figure out the amount of pressure needed to keep the vang extended against that pressure.

Something like...if it is a 2" diameter piston, that's an area of pi*r^2, or 3.14 square inches? And if it needed to support roughly 300 pounds, it would need a gas pressure of just under 100psi then, no?
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Old 13-06-2007, 20:12   #21
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When I talked to Navtec I was told the nitrogen pressure is suppose to be 600 psi. If it needs more pressure to hold the boom up then one needs a bigger vang unit.

And yes, the back stay tensioner has to be charged also, at 100 psi, if it has a fitting. Mine does.

Here's a picture of my charging unite. The big end goes in the bottle and the small end goes on the cyl fitting. The other alum. block is for larger cylinders that I work on....................._/)
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Old 13-06-2007, 21:36   #22
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So can you use that high pressure nitrogen bottle to make good supercooled ice cream at the same time then?<G>
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Old 14-06-2007, 05:10   #23
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Ok......Guys

What I have is a Boom Vang unit that requires the 600 PSI of nitrogen in it. The seals have been replaced already by a local hydraulics shop. I witnessed the process and is NOT complicated at all. Basicly the original seals were pretty bad. They were replaced with industrial quality seals. As a matter of fact the guy at the shop had done several of these units before because some of the local rigging shops take the units to his shop for the seals replacement and then go to a local Fire Extinguishers Specialist to have them pressurized with nitrogen. After seeing the disassembled unit I can see how simple it really is. The loads on these units are just minimal compared with industrial applications which handle HUGE repetitive loads. When I wrote about the fitting I was refering to the correct thread and pipe/hose that would fit between the two pieces that hold the pin. I have already found the correct thread fitting. Basicly what I ended up with is very very close to what Delmarrey shows in his photo. What if the seals of your backstay unit fail in the middle of nowhere in a remote island? One should be able to at least replace the seals......
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Old 14-06-2007, 10:21   #24
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Nitrogen can be had at large industrial equipment/truck shops. Rather then using return springs these days, nitrogen cylinders are preferable. They are quiet and there's no dangerous spring to reload.

A lot of the new car/truck (motor) hoods use the throwaway nitrogen cylinders to hold them up.

As for loosing at back stay at sea, one can use their main sheet with a topping lift or even the mainsail to tighten up the rig. Then put in a temporary block-n-tackle or tie in a line to the backstay to get your self back to port.

As you now see the seals are not all that hard to put in. It's just knowing what problems to look for during the tear-down. Like the condition of the bore, head, ram/rod, piston and it's attachment. If all is well, the new seals should last 10-15 years with the right oil. If there is damage or corrosion they may only last a few days.

Now the seals on the hand pump, that's a whole different story. I had to heat (real hot water) them to get them to stretch over the piston/ram that was only 3/8".
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Old 14-06-2007, 11:10   #25
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I agree, the hand pump is a whole different story. I had it refurbished at an authorized Navtec facility. But that is a small unit and shipping costs are not an issue. When I talk about the failure of a backstay Navtec component, the point I am trying to get across is that the Service Manuals and spares should be available to all of us. Just like in any other component of your boat. Actually, this weekend we are going to replace the backstay and forestay in my Frers First 456. What the rigger is suggesting and has done before is to either install a long enough turnbuckle on top of the backstay hydraulic unit so that if it fails you can just adjust the turnbuckle and continue sailing. Or the second option is to leave a fitting at the exact length where the mechanical backstay adjuster used to be, so if the Navtec unit fails you can replace it with the mechanical adjuster. Maybe a combination of both solutions.
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Old 15-06-2007, 04:37   #26
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Mission Accomplished

Well finally the Boom Navtec unit is back in my sailboat. I took it to the Fire Extinguishers Service company with the fitting and they added nitrogen to 600psi. I bleeded the line and filled the unit with the appropriate oil, connected the line and IT WORKS. Total cost $170.00.
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Old 15-06-2007, 11:38   #27
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Another successful internet repair job!


At quite a savings..........................._/)
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Old 15-06-2007, 11:43   #28
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Thank You - To All

I guess this is what its all about. To make this lifestyle affordable and fun. Thanks to all of you for the help.
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Old 08-08-2007, 14:42   #29
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I also just repaired my vang with a seal kit I bought for $106 from my local authorized navtec repair agent. Now I need to recharge it with nitrogen. What fitting do you use for this. I know it's close to 1/8" pipe thread but not quite. The local navtec guy wants $100 for the recharge.
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Old 08-08-2007, 18:53   #30
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If you look at the picture in post #21 you'll see the fitting. It's much like a tire stem fitting but stronger for the higher pressures.

The fill tools are around $125 for the cheap ones. Unless you plan on using it often, you would be better off paying the $100.........................._/)
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