Gas spring replacement (boom vang)

Tim Good

Tim Good

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Selden Rodkicker Gas Spring Replacement?

My boom vang has suddenly lost pressure so I can only assume the gas spring inside has died.

It is a Aratron G28-300-2500N. It seems the company is still about and makes that model but in Germany. Are these things common and if so is there a UK company that could supply a replacement?

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I needed a pair of gas springs for my vang. The old ones were ordinary steel and had corroded badly so I specified stainless ones and had them made by a specialist maker. To get the force rating for the springs I used a load cell on the main halyard, it would be possible to use a bathroom scale and some basic mechanics to work out the force needed. Remember it needs to be higher so the boom lifts and allow for ageing. PS from your photo your spring is 2500N or 250Kg force but it's worth making sure that is enough.
 
Happydaze said:
Got myself an adjustable pressure stainless strut from these people last year and works great.

http://www.sgs-engineering.com/gas-struts/stainless
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Thanks! According to their page the GSSV14-300 is exactly the same as the Aratron one which is supplied via Selden. Ok here goes for the price comparison. Selden want £300 for their Ararton and the SGS version is £100.

Hmm what to do :rolleyes:
 
Interesting thread. I am thinking of fitting one to my Selden rodkicker, and would be interested to know what sort of end fittings are used. I have a 36 ft boat, and from memory the rodkicker is about 1500mm long. The strut seems to come with an m10 thread at each end as standard, but how does it attach internally to the rodkicker?
 
Finbar said:
Interesting thread. I am thinking of fitting one to my Selden rodkicker, and would be interested to know what sort of end fittings are used. I have a 36 ft boat, and from memory the rodkicker is about 1500mm long. The strut seems to come with an m10 thread at each end as standard, but how does it attach internally to the rodkicker?
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Well I just found that out tonight. They use the same fitting as on the other end oddly. Must have done it to save making a purpose designed part. See photo of how mine just burst through pushing the threaded m10 fitting out of the plastic.

The Selden part number is 319-587 and retail for about $15 in the states. Awaiting to hear what two will cost me here. I'm going to modify the one that going internally into the rod kicker so it can't force the threaded fitting out again. Maybe a plate on the back or a large washer.

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Finbar said:
Interesting thread. I am thinking of fitting one to my Selden rodkicker, and would be interested to know what sort of end fittings are used. I have a 36 ft boat, and from memory the rodkicker is about 1500mm long. The strut seems to come with an m10 thread at each end as standard, but how does it attach internally to the rodkicker?
Click to expand...

From memory, on my Kemp one, the bottom end of the strut screws into a 12mm wide disc the diameter of the tube and that pushes against the bottom fitting when compressed and the top fitting is a 30mm long tube that is riveted into the upper moving section of the rodkicker with a solid end which has the M10 thread in it.
 
I have had the gas struts in my vang fail. When you replace the strut make sure it is the right way up. These gas springs are loaded with compressed nitrogen and a small amount of oil. They must be fitted the right way up so that the oil stops the seals drying out, otherwise the gas will leak out. It can go quite suddenly, in my case the boom just fell when I released the topping lift. It could have killed anyone underneath. I found a firm in Sheffield who make springs and they made me two out of stainless steel, wound opposite ways to fit inside one another to replace the gas struts. It works very well with the springs calculated to balance the weight of boom and sail when the boom is a little above its normal working position.
 
I fitted a heavy cloth fully battened main for charter use on my Jeanneau 43DS and since then the sparcraft solid kicker has failed every year.

Interested in uprating it. One rigging company is suggesting going to a selden one but wonder if fitting a new inner from sgs would solve the problem. How do I start to establish the rating needed though?
 
Sailfree said:
How do I start to establish the rating needed though?
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Difficult to say but I have just ordered this:

http://www.sgs-engineering.com/gas-struts/stainless/adjustable/14mm-rod/gssv14-300

It is adjustable unlike the Selden ones by Aratron. I know mine needs 2500n but the boom is huge and heavy but a small allen bolt can be released in increments. Sp for the above I don't need to adjust.

I think a good gauge is to install one highly rated, crack the kicker down so the boom likes horizontal and then hang off the end of the boom. If your body weight can just pull it down then that's about right. If you can hang off it with it dropping then the pressure is too high. If you can pull it down easily without really applying your own weight then maybe too little pressure.

This is a very rough guess based on what my current setup was like before it broke. Someone might have a better suggestion.
 
northcave said:
Difficult to say but I have just ordered this:

http://www.sgs-engineering.com/gas-struts/stainless/adjustable/14mm-rod/gssv14-300

It is adjustable unlike the Selden ones by Aratron. I know mine needs 2500n but the boom is huge and heavy but a small allen bolt can be released in increments. Sp for the above I don't need to adjust.

I think a good gauge is to install one highly rated, crack the kicker down so the boom likes horizontal and then hang off the end of the boom. If your body weight can just pull it down then that's about right. If you can hang off it with it dropping then the pressure is too high. If you can pull it down easily without really applying your own weight then maybe too little pressure.

This is a very rough guess based on what my current setup was like before it broke. Someone might have a better suggestion.
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I used this one for replacement three or so months ago. Just let a bit of pressure out (2 or 3 secs in total I seem to remember) and boom (just over 5 metres) is be help up fine, yet not too rigid.
 
dgadee said:
I used this one for replacement three or so months ago. Just let a bit of pressure out (2 or 3 secs in total I seem to remember) and boom (just over 5 metres) is be help up fine, yet not too rigid.
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All this is new to me.

Can I make sure I understand it.

1. Remove sparcraft rod kicker

2. Drill out pop rivets at end.

3. Unscrew end from inner gas strut.

4. Unscrew gas strut from other end

5. Get number and rating from existing gas strut.

6. Measure internal dia to see if bigger gas strut can be fitted

7. Speak to SGS technical department and agree a heavier duty gas strut that will fit.

8. Fit new gas strut pumped up to max pressure.

9. Get boom horizontal with kicker then hank off it to gauge any drop. Not sure this is anything more than a guide as my heavy cloth sail (fully battened Jeanneau 43 Deck Saloon) may weigh more than me.

10. Fit sail and see if strut copes - if necessary undo allen screw to release some of the gas until it appears correct.

Any observations /guidance on this appreciated. Diagrams/Drawings /instruction sheet (even if for another make) would help.
 
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I can't say on a Sparcraft one. You don't need to drill the rivets on a Selden one as the two sections come apart from the middle and you just pull out the gas rod.

Then measure it up and see what it says in terms of force. The Selden ones have the same M10 fittings as the SGS so I just need to unscrew the old one and re screw the new one in. 10 min job literally to do the whole thing.

Whilst I'm there I'm replacing the plastic bits that the rod screws into and renewing the rivets but it isn't necessary if the general rodkicker is in good shape.

Not sure if this will help but: http://www.seastream.co.uk/?page_id=211

P.s. I'm saying all this but I am fitting it back together tonight but I don't envisage any issues.
 
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Useful information. I have a Selden rodkicker which never had a gas strut. I have taken it off the boat and taken it apart. The bottom section is 1500mm long, not counting the end fitting, and the top section has a base to take the gas strut. The bottom section has no such fitting, but simply has the wire cable which I think is connected to the cast aluminium bottom fitting. My working assumption is that the gas strut is screwed into Selden part no 319-587 which then slides into the bottom section until it bears against the cast aluminium bottom fitting, with the top end screwed into the same 319-587 which fits neatly into the base of the top section. Can anyone confirm?

I would also like to know if the GSSV14-300 strut fits my size rodkicker.

Thanks in advance
 
Finbar said:
Useful information. I have a Selden rodkicker which never had a gas strut. I have taken it off the boat and taken it apart. The bottom section is 1500mm long, not counting the end fitting, and the top section has a base to take the gas strut. The bottom section has no such fitting, but simply has the wire cable which I think is connected to the cast aluminium bottom fitting. My working assumption is that the gas strut is screwed into Selden part no 319-587 which then slides into the bottom section until it bears against the cast aluminium bottom fitting, with the top end screwed into the same 319-587 which fits neatly into the base of the top section. Can anyone confirm?

I would also like to know if the GSSV14-300 strut fits my size rodkicker.

Thanks in advance
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Basically right yes. Bit the length of the rod is not long enoug to reach down all the way to the end fitting at the mast. Therefore the bottom section in mine has a long aluminium tube which measure half the length of the bottom section inside. It only acts as a stopper which the rod sits against 319-587.

I think.... When you buy the proper Seldon gas strut replacement for £300 they give you ally tube which is the right length. My bottom section is 1700 long so you'd either want the same inner tube and a gas rod 20cm shorter or a tube 20cm shorter and the same gas rod. You'll notice SGS have ravious sizes so it would be easy to sus out.

The tube insider the lower section acts only as a stopper so nothing to say you couldn't find a length of tube yourself and out it in. Might not need securing but I'd probably drill a hole through the lower section and rivet it in place.

Does that make sense? In hindsight I should have take a photo when it was all apart on Friday night.

I can confirm the SGS rod is great though. And the adjustable function is excellent. I found the default 2500N was too powerful as I could hang on the boom with it barely lowering. I let out about 300N and now just right.

Letting out the air is a rough guess. Instructions come with the strut.
 
Many thanks, very helpful. I think I can make the SGS strut work ok. I can make up a tube of the right length and fix it in place easily enough. Is yours a round tube, or is it the same profile as the top section?
 
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