Tuesday, April 9, 2013

New HF/SSB Backstay Offset

Solace HF/SSB antenna cable ran down the backstay with a two inch off set as shown in the photo to the left.

The problem was, what to do about the cable as it ran pass the backstay turn buckle. Ordinarily, I might have fashioned something up to keep it tidy, but with the boarding ladder in the middle of the pushpit, people were constantly reaching up and grabbing anything to help themselves get aboard. Mostly they grabbed the back stay and HF cable. Eventually it became loose and pulled out of the deck fitting. (The ladder here is part of the pushpit, but when needed folds down and steps are formed over the railing.) Yes the back stay is right in the middle of the boarding area!

So I came up with another idea. I used two tubes. Pressure PVC  pipe; one 50mm and the other 20mm. I made end caps which can be viewed here.
for the 50mm pipe and some 32mm for some shroud antichafe rollers. (Another project)
The 20mm pipe has some strategically placed holes placed in the tube along one straight line. These were big enough just to fit my pop riveter. The length was assessed to allow the tube to move up the backstay to gain access to the turn buckle. The 20mm pipe was pop riveted to the 50mm pipe.
The back stay was marked for it's present tension and the turnbuckle was then undone.
The first end cap was placed on the back stay and held in place with some self amalgamating tape. A small rope was thread through the 20mm pipe by which later we would draw the HF wire through.
The combined pipe was then placed over the back stay and the top endcap engaged into the 50mm pipe. A small hole was drilled each side and a small SS screw inserted through to engage and hold the top endcap.
The bottom endcap sat on the very bottom part of the turn buckle, just above the swivel  The inside hole here is large because the "T" bolt that makes the bottom part of the turn buckle is larger in diameter than  the backstay cable. This bottom end cap does not slide up and down.
The tubing was slide up the back stay and the turn buckle re connected and tensioned. The top wrench, which holds the top swage at the turnbuckle and prevents the backstay from twisting, supports the tubing while tightening the turnbuckle. Once the turnbuckle is tensioned and the split pins applied, the tubing is allowed to to slide over the turnbuckle and engage the lower endcap. The same two holes with screws to secure the endcap were applied to the lower endcap as done for the top endcap.
The HF cable was then threaded through the 20mm tubing and attached appropriately.

Hint. As you undo the HF cable above the backstay isolator, place a small rope around the isolator so that later you can have a companion pull down on the back stay, which will help with re connecting the turnbuckle. Also, if you buy pressure PVC pipe, it may have black writing on the pipe. A paint thinners on a rag usually wipes this off so you have a nice white tube.
How to stop the pipe from turning? I'm trying some heavy self amalgamating tape at the bottom end, which at the moment has a little give, but seems to hold everything in place. Another method might be to place a bolt through the 50mm pipe and through the turnbuckle openings.
To access the turn buckle again, it is a simple case of talking out the small screws at the bottom endcap and sliding the combined assembly (minus the bottom endcap which stays in place) up the backstay to gain access.
In the photo to the right you can see that there is just enough room to slide the 50mm pipe up the backstay. The HF wire is cable tied to the isolator and gradually moves away from the backstay until it enters the 20mm pipe.
The holes which were made for the pop riveter will later have some 20mm rubber bungs inserted to tidy the whole thing up

1 comment:

  1. Hi, my name is Connie and I am married to your #6 follower, Steve. I came over to check out your blog, and have decided that this is a place for me to learn more about the technical side of sailing. We are presently restoring a Glen-L Fancy Free. It is our fourth sailboat, so I am pretty comfortable being a first mate, but when it comes to the technical stuff, I'm pretty naive. I think that following your blog and reading your posts will be a great way for me to smarten-up :)
    I would love to take this opportunity to invite you over to follow me back, too :)
    Smooth Sailing,
    Your new blogging sister, Connie :)


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