S/V Johanna Rose: November 2015

Selden Rodkicker Type 20

The Selden Rodkicker Type 20

It may have been coincidence, but I recently started to attached the main halyard to the end of the boom to lift the boom like a toping lift. The idea, as I read on the C&C list, was to relieve stress on the boom vang when not in use. At the time, I did not know the brand of ridged boom vang which was install. And shortly after doing so, the boom vang spring failed (while reefing the main in 20 KTS gusts single-handed). Ok, so I had a broken boom vang to repair. After I little research, I found out the vang system was a Selden Rodkicker type 20 with a gas spring rated at 2,500N.

Everything I read stated that removing and replacing the gas shock in the Rodkicker was a simple task. Never the less, I was unable to easily separate the Rodkicker to access the gas shock. Examining the online Rodkicker diagrams, I realized that the problem was due the wire cable being too short. Apparently someone prior cut the cable and swaged an eye on the end such that the only way to disassemble the Rodkicker required cutting the wire. This also meant that the old wire rope needed to be replaced with new 7x19 1/4" stainless steel wire rope. The two ends of the gas spring screw into plastic end plugs. The same plug is used on both sides. On the upper side, the end plug fits into the inner extrusion tube and snaps in place. On the lower side, the plug sits on top of a cylindrical tube spacer. There was a problem in that this smaller tub cuts into the lower plug causing the gas shock to twist off and eventually break. This seemed like a poor manufacturing design.

To correct for the lower plug design flaw, a new lower plug was made out of solid HDPE. Using the old plug as a guide, the new plug was cut to size on a table saw and sanded to match the rounded edges. A central M10 hole was drilled and tapped for the shock to screw into, and a wire slot, like as in the original plug, was cut along one side. Photos below show the manufacturing of the new lower plug.

The original gas shock was an Aeration G28-300-2500N-02. This is a gas shock for a Rodkicker type 20 hard spring. Selden sells replacement gas shocks, and this replacement lists for $300. I came across a discussion online where someone in the UK found a replacement by matching to specs from an industrial supplier for about 100£. I was able to find the exact replacement gas shock at McMaster-Carr (item# 9416K52) for only $86.

McMaster-Carr also sell a stainless steel version of the gas shock for about twice the cost. I ddecided not go with the stainless steel version as from what I read, the internal seals are what fail first. The Selden (Aratron) replacement is a standard version (not S.S.), and the original failed shock which I was replacing looked like new (i.e. it was an internal seal failure).

Below are the specs for the new gas shock:

Gas Spring with Threaded Ends (McMaster-Carr item # 9416K52)