Rig tensioning

[Mikedefieslife]

Going to be checking and tensioning my rig soon enough. (Old Prout Snowgoose)

(Un)fortunately, I have 8mm cable which means only the Loos Pro, or Spinlock gauges with fit, and both are double the price of their smaller offerings.

Am I right in thinking that the rig tensioned in relation to the gauge of the cable, at roughly 15% of max breaking strength? So that means there's no manufacturer's of other specs to consider? Which would be just as well as my manufacture went under long ago.

On the Port quarter back stays the cable is broken into three lengths and hooked up to via rubber coated connectors. Are these of any significance, or are they a left over from an old SSB setup?

 

[Norman_E]

That thing looks like an SSB insulator. but on a an inverted Y shape backstay usually only the top piece is used as an aerial. If the backstay is in good shape I would not replace the insulators, which would be expensive. I actually think that my Loos gauge which goes up to 10mm wire was one of my better boat purchases, bought from SaltyJohn of this parish. http://www.saltyjohn.co.uk/product-category/rigtensiongauges/ You certainly do tension the rig to a percentage of the wire rope breaking strain, but on my boat with mainly 10mm wire it does not need as much as 15%. You can see if your cap shroud tension is great enough when sailing. The leeward shrouds should not go slack when sailing upwind or on a beam reach in a decent breeze. Be careful of tensioning the backstay too much as it can put excessive tension on the forestay. You can measure tension with a two metre foot stick, using it to measure how much the wire stretches from a taut but unstressed state to a point where the wire has stretched 3mm over the two metres representing about 15% of breaking strain. The method is explained here http://sail-delmarva.blogspot.co.uk/2015/05/the-folding-rule-method.html but I consider that it is tedious to do, and prone to error in measurement. I thought life is too short to fiddle about that much and bought the gauge.

EDIT: Sorry, I misread your description of your backstay, I now read it as a split stay with each side going right to the masthead, and yes those things are SSB insulators, and if you want to get rid of them you will need a whole new stay.

 

[BelleSerene]

Welcome to borrow my Loos Pro gauge if you're around Hamble.

Yes, you're right about relative rig tension.

Yes, that's an HF antenna insulator.

With your (I think) straight spreaders you need backstay tension to keep the rig up - and the correct tension is similar to that in the shrouds - so if the insulator is staying in situ, you are dependent on the physical integrity of its junctions and wire swages.

 

[Bob_Ranft]

Been going through same problems with a Snowgoose 37 over the last two years. Because the cap shrouds, aft lowers and backstays are 7mm have been able to use the cheaper loos gauge, which just caters for the 7mm wire.

Basically set them up to 10% of breaking strain. At 10% they are tighter than previously set by hand etc.

If you check on the web, many Snowgoose owners state that the rear cabin doors start to jam in their frames if the rig is tensioned any harder than this.

We adjust tension on the aft lowers and staysail to give a touch of forward mast bend, again setting the aft lowers up to approx 10%.

Big problem with the mast aft rig on all Prouts is getting adequate forestay tension, due to the fact that the angle of the backstays means thay cannot exert the same degree of rearward pull as a traditional rig. Seems to me that the backstays produce far more vertical pull down on the mast as opposed to rearward pull.

Generally held that the usually quoted rig tension advice of 15% of breaking strain should not apply to multihulls.

At 10% tension we find that the wires on the lee side of the rig do not go over slack when beating.

Have a word with Robert Underwood at Robert Underwood Multihulls, he normally puts out good advice re the Prouts.

Hope above helps

Bob