ssb insulator

[30boat]

I am installing a ssb(icom m700) in my boat and the antenna is proving to be a problem.I was advised to use a whip antenna but cost aside, I don't fancy the idea of a 5 meter tall thing on a 32ft boat. Backstay insulators are also expensive.Instead I was thinking of using lashings to insulate the backstay .I would use spectra rope and since my boat has a 3/4 rig and the backstay is only 5mm in diameter it would'nt be dificult to achieve the same strength as the wire.There is a tackle at the bottom so that end is already insulated . Any ideas?

Thanks

 

[zephyrsailor]

we used backstay insulators
just bare in mind u not want to be touching the ariel bit of backstay
u will fry!

 

[Guest]

Post deleted by danfoley

 

[kgi]

A friend of mine actually takes his coax straight to his backstay and uses the whole rig as the aerial of course every one has to be aware that your transmitting as it could ruin your day, and before anyone scoffs at it he designs aerials for a living

 

[HaraldS]

can't see a reason why your idea shouldn't work just fine. Spectra or Vectran lashings would be quite a bit stronger than the wire. But where were you going to tie the lashing to. The codder pins? You need to make sure you have no sharp edges and no chafe. Also I'd replace the lashing once a year as this stuff degrades quite quickly from UV.

 

[jfkal]

Is your antenna then running parallel to the backstay? Wouldn't that influence the performance?

 

[Guest]

I have made a backstay for someone out of vectran and inserted a wire into the vectran for the SSB antenna, this is fairly difficult to do so would suggest using a rigger if you choose this method. For my own boat (when I get an SSB) I am going to try running the antenna cable parallel to the backstay using cable ties through pieces of tube to hold the antenna away from the backstay as I have seen done on other boats.

Cheers

Lash

 

[Guest]

Post deleted by danfoley

 

[jfkal]

Thanks Brian )

 

[Guest]

Post deleted by danfoley

 

[Strathglass]

Re: advancement of the plot

I am a retired profesional RF engineer and I have the same problem as everyone else on how to solve the insulated backstay issue.
This is the cost of rigging insulators and a reluctance to compromise the single backstay on the boat I am building. Reading the forums I have come up with this idea which is reasonabely cost effective and will not compromise the backstay or the RF efficiency.
My backstay (masthead rig) was to have been 8mm 316 stainless wire.
The first thing is to replace this with a modern synthetic backstay of the same strength, Vectran?. I do not know the cost of this and the required end fittings.
We can now add the aerial. This does not have to be integrated into the backstay, but it is advantageous to segregrate it, typically by fitting it between the top of the mast and the pushpit.
As there is now no rigging stresses on the aerial, for insulators we can now use low cost ribbed plastic insulators available from non marine sources and can use wire optimised for the RF performance.
The lower end can be fed to a through deck insulator to the coax under the deck.
I have not gone into the safety aspects of preventing human or animal contact with the wires or the grounding requirements for correct operation. Those are separate issues which can be addressed separately once the initial problems have been overcome.

The method described will give good RF performance but my main question is.

What diameter and type of COST EFFECTIVE synthetic material can SAFELY replace 8mm 1x19 316 SS wire rope for my backstay?
I have heard about PBO but also read reports of dramatic effects of breakages. Is there a less exotic matiral which will do the job? and how do you terminate it?

Can someone add this info please?
Thanks

Iain

 

[30boat]

Thanks to you all.I think I know what I'm going to do now.I'll rig a separate wire insulated by lashings and running more or less paralel to the backstay.Length won't be a problem ,my mast is 13m tall.An expert I talked to said I should not have any paralel wires in the vicinity but I'll have a go anyway.

 

[HaraldS]

Don't run it too close to your backstay if the backstay is grounded. It will eat some, maybe a lot of your transmit energy. It's kind of like a short circuit.

 

[vyv_cox]

Re: advancement of the plot

Would a Vectran backstay be strong and reliable enough? Replacing an 8 mm wire backstay with a non-metallic one sounds somewhat risky when the only benefit seems to be to save a bit on the insulators. I don't have SSB but I see many insulated backstays around and they seem reliable enough.

 

[Strathglass]

Re: advancement of the plot

I don't know VYV. That is why I asked the question.
It must be better SSB wise than having the aerial parallel to a grounded wire. It is like having a TV aerial sitting just a few centimetres above the ground.
Unless I was certain about an alternative backstay material I think insulators on the backstay are currently the best option.

Iain

 

[HaraldS]

Re: advancement of the plot

Many racers seem to use high tech fibres for part of the rigg to safe weight. Very typical on runners, and most don't have any other backstay!
But I also think they replace the stuff quite often, and I would be worried about UV degradation.

I did look at this a bit for my running backstays, they are less critical, really only needed when there is a big seaway and a high load on the cutter-staysail.

So here are the numbers:

1x19 wire 8mm breaking-load 5380 DaN
Vectran 8mm BL 1650 DaN; 10mm BL 3000 DaN, very low stretch
Dynamix 8mm BL 3000 DaN; 10mm BL 5100 DaN; a bit more stretch
Dyna-One 8mm BL 5000 DaN; 10mm BL 8500DaN; very low stretch;

Dyna-One is 1/8 the weight for strength relative to 1x19 wire.

8mm Dyna-One is Euro 4.20 per meter. So you could figure out what it would cost to replace once a year. Not sure that's necessary, but ...

 

[RacePassage]

Prior to going offshore I installed an Icom 700 pro SSB together with the recommended Icom automated tuner . The tuner was installed in the quarter berth as close to the thro' deck fitting as poss.With respect to the antenna I went to Radio Shack( I live in Vancouver) and bought an inexpensive kit . about $12. canadian, which consists of 2 small plastic insulators and a length of strand copper type wire. After talking to all the 'experts' decided on the following installation.
the antenna was strung from the back stay fitting at top of mast with the top insulator about 4 ft from masthead( to keep antenna away from mast & fittings) and led more or less parallel to backstay to fitting at base of mizzen mast. (A triatic arrangement would have interfered with the wind generator) with the wire cut to a set length.
The wire used from the tuner to to the antenna was GTO 15 and is used in the neon sign industry(recommended by Ocean Navigator magazine) which may be available in the U.K and was sleeved in 1/2 in plastic tube from the thro' deck fitting to the antenna, not necessary but a precautionary measure. It was then crimped and soldered to the antenna at lower insulater and joint taped.
As I was told the important point is that there is a set length for the entire antenna, that is- from the TUNER to the top insulator. On my boat I think I used a total length of 14M. A learned friend of mine with a much bigger boat, and taller mast, used 18 M. From tables I gleaned that as 20 M band length is widely used then antenna lengths of 20.91-21.43 M should be AVOIDED.
In any event in my year long passage Vancouver-La Paz mexico the SSB has performed very well as we have used the Pacific nets frequently.
By the way the reason for installing the cheapie antenna was if the length was wrong it would be inexpensive to replace There is more than enough wire provided in the original kit. As it is the length appears to be right and when it breaks it will just cost another C$19.00- So far all is well!!

 

[Guest]

Re: advancement of the plot

Exotic synthetic fibres for backstays are ussually only used on fractional rigs. UV damage is not a problem as the cover is purely a cover and doesn't contribute to strength, obviously they are more suseptible to physical damage.

Ends are often soft eyes. Tension is by block and tackle or any method you prefer.
Getting the length right due to constructional stretch can be a problem.
Vectran is suitable for backstays.

Personally I wouldn't use rope on a masthead rig of a cruising boat or a block and tackle adjustment.

Cheers

Lash

 

[SimonJ]

Re: advancement of the plot

I fitted a cheap simple and extremely effective aerial to my Sadler 34. I obtained a suitable length of cored braided rope (10mm Od) and removed the core. Into the core I threaded (much easier than it sounds) an 8mm sheathed copper wire stopping about 3 ft from what became the upper end. I also sealed the exposed wire end with self amalgating tape and gunk. I secured the top (rope)to a spare fitting at the mast head adjacent to the backstay fitting using a thimble and a shackle. At the bottom after suitable measurement I arranged for the aerial wire to emerge from the core and fed it to the tuner which was close and in a locker. I tensioned the lower end of this new aerial array to a convenient U bolt on the quarter. This aerial behaved amazingly well with the following advantages:
1 Cheap 2 Does not weaken backstay 3 More effective than a backstay as filaments of aerial wire are straight not twisted as in the laid wire backstay 3 Aerial is well clear oif backstay.
Incidentally my radio is an ICOM 706 which is very compact with an excellent performance but needs simple (by an expert) modification for SSB as well as Ham use. I c an supply details of a Florida supplier if needed.

 

[Guest]

Re: advancement of the plot

I can see where you are coming from from, sounds like a good cost effective solution

cheers

Lash