How does a Bottle screw work when adjusting rigging?

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Hi everyone,

I know this is something every self respecting sailor should know however, it's time I owned up and admitted I've not got a clue how the bottle screws work, after hunting around all the rig tuning info assumes you know this!

I understand what I need to do in order to tune my rig, what I don't know is whether you use the bottom screw to tighten your rig and the upper to loosen or vice versa or both!

I'm assuming the less thread you see the tighter the load on rig? if this is so do you have to tighten both ends of the screw?? /forums/images/graemlins/confused.gif

BTW I'm using closed screws so I can't see how much thread is remaining in the screw, the last thing I want to do is unscrew too much and something pings off and I lose my shrouds/stay, hence my seeking clarification of the screws operation.

It would be much appreciated if someone could enlighten me as to how they work when tuning standing rigging.

Many thanks!
 

Gunfleet

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They should be opposing threads. When you turn the body of the bottlescrew one way top and bottom both tighten, the other way they both loosen.
 

john_morris_uk

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Capabar is right in his description of how they work.

One word of warning. The enclosed type are sometime all stainless and you run a risk of 'galling' the threads if they are not greased. As the screw tightens, the s/s sort of 'drywelds' itself together and locks the whole screw up. You should be able to loosen them all off enough for the rig not to go 'ping' whilst you take each one apart in turn to grease them. Back up each cap shrouds/forestay/backstay with a halyard when you undo the final part of each one in turn and apply lubricant/grease.

Hold the wire end with a suitable spanner (there are flats for doing this on the wire end fitting) and use a suitable bar in hole in the body to tighten/loosen.
 

William_H

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You have all the information but I just have to have a go. One of the threads of your bottle screw is a left handed thread. These are fairly rare but sometimes found on gas bottle fittings or some drive axlews where normal drive would tend to unscrew the nut. So to tighten the bolt etc. on a LH thread you must turn it in the direction you usually loosen a normal thread.
if you look at your bottle screw threaded parts you will see the thread on one is strange ie LH. If you undo the bottle screw completely you will see that only one end of the bottle will mate with the LH thread end and then only if screwed backwards. The other end is normal. Now because bottle screws have no up ior down you will have to identify which way to turn it to tighten the rig. If it has lock nuts you will see the LH thread nut works opposite also and with lock nuts you can see easily the gap getting bigger or smaller. Note that the length of the bottle screw varies by twice as much as would with only one screw. As some styles are.
I dimantle my bottle screws each year. They have SS threads a in bronze bottle and can easily corrode and seize. This is often the end of the bottle screw although heat and lubricqatio can sometimes release it.
When reassembling the bottle screw. I offer both screws into the bottle at the same time so that the amont of thread at each end into the bottle is equal. If you measure the length of the threade part before you start then you will know how much is inside. A minimum of twice the diameter of the thread inside would be a good standard although the more the better. If you don't have enough thread inside use a shackle to extend the chainplate or stay.
finally they must be locked. If there are no locking nuts then fit stainless steel lockwire through the hole in the middle wrapped around the bottle so that it is pulling the whole thing tighter and attached both top and bottom This will ensure that it can't work loose. good luck olewill.
 

fireball

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Depends on the shackle used and the rig it is used on .... I've used shackles for the last 20 years on various types of masts, and not one has come down due to shackle failure ....
 

roger

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Adjustment and lubricant

I got a bit twitchy when you talked about turning the screws. THis means you are winding up or unwinding the riggin itself which will not do it any good. The advice to use a spanner etc to hold the end going to the rigging wire is very good.
On lubricants for stainless steel. Other members of the forum may differ. I use copperease from a Motor Accessory shop. IIt is intended to be used to prevent galling. There is a risk (possibly theoretical) of it encouraging galvanic corrosion). I have used lanolin (wool fat) but the stainless/stainless thread galled up and I had to replace the backstay which cost over £100. Using the right grease has to be cheaper.
 

Bodach na mara

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Re: Adjustment and lubricant

I can speak with bitter experience about galling. I was renewing the lifelines and testing that all screws worked as some had been stiff on dismantling. I had sprayed with WD40 or similar and one stuck when I screwed it on to the threaded end by hand. When trying to unscrew it became stuck to the point that it was un-movable. Someone told be that the WD40 type of stuffis no good for SS. You should clean with white spirit (or better diesel), dry off thoroughly then grease lightly with silicon grease. I have reservations about the grease as it can trap dirt and cause more problems.
 

aitchw

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Re: Adjustment and lubricant

Have been trying bike type dry lube (silicon + teflon) and it looks promising so far. It leaves a waxy film and doesn't appear to trap dirt.

Peculiar stuff stainless. Whilst using small (4mm) bolts on the pintles of one of my dinghies which were rather too long the nuts would accasionally seize before they were half way down the thread and could not be undone.
 

oldharry

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One point nobody has mentioned: which end is the 'top' of the screw? It is clearly a good idea to get all the screws the same way up, and personally I set mine up that tightening the rig is acheived by turning clockwise - same as tightening a nut on a bolt. But I find it surprising how many boats have them set the other way. I suspect riggers 'always do it clockwise'- to coin a phrase! But what does the panel think?
 
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Many thanks everyone for the information, I'm going to give this a whirl at the weekend.

Roger, I was turning just the top screw and hence I must have actually been turning the backstay wire itself. I did return the top screw to more or less the position it was in so I don't think I've done any damage (Fingers crossed).

Knowing what I know now, I'm pretty sure I'll be able to adjust the stay properly and put the pre-bend in.

I think I may also invest in a rig tension gauge just to make sure my rig isn't to loose or to tight.

What got me thinking about all of this is my mast has just gone up and I know the boat yard hasn't tuned the rig. It's whilst I was sat in the cockpit I could feel a small amount of vibration in the boat every now and again due to the mast oscilating in the wind.

I went to the foredeck, lay down and looked up at the mast, I could see some movement in the middle of the mast from side to side where the spars are. Slack Cap shrouds?
 

Vara

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Now you know how a bottle screw works down load THIS SELDEN GUIDE
An idiots guide to rigging.
Not being rude but I understand it so it must be simple.
Outlay to get your rigging right about £2 and 3 or 4 hours on a day with wind strength 3/4.The Vernier gauge I use to do this cost 99p from Wilkinsons.Offcut from old tape measure and some tape and your off.
I've tried using tension gauges and find it difficult to get consistent readings.But that could well be operator problems.
 

oldharry

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Re: a better way than crossed fingers....

[ QUOTE ]
Roger, I was turning just the top screw and hence I must have actually been turning the backstay wire itself. I did return the top screw to more or less the position it was in so I don't think I've done any damage (Fingers crossed).

[/ QUOTE ]

... when a rigging wire has been twisted, is simply to slacken it, take out the clevis pin or shackle, allow the assembly to take the position it wants, and tighten down again, this time holding the top screw in position. Half a turn either way will do no harm.

To check the stay for damage after twisting it like that, while it is slackened off, look along it for any sign of a kink or 'snail' having developed in the wire that was not there before. If there is the wire is damaged. Next, check carefully at the terminals - use binos for the masthead if it is up. If there is any evidence at all that the wire is either unlaid - forming a rather jolly little 'parrot cage' effect, or there is any sign that even a single strand has fractured - then the wire is damaged and needs replacing.

Stainless wire is funny stuff though and even if it looks OK - fingers crossed is the only alternative to replacement, but the odds are more in your favour. /forums/images/graemlins/crazy.gif
 

oldharry

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Re: Shackles in the rig

Hundreds of boats (many of mine included) sail quite happily with shackled rigging. However, using shackles does produce a weak point in the rig. 99.9% of the time it doesnt matter, but if the rig is subjected to violent shocks, like in an uncontrolled gybe, or a knockdown situation, the use of shackles MAY just tip the balance to a dismasting.

Rigging toggles and clevis pins simply have much more metal so are correspondingly stronger. Also from the engineering point of view a close fitting clevis pin is a much stronger assembly than a loose fitting shackle pin. If the pin fits its hole snugly, then as load increases and the metal begins to deform, the load spreads across the pin surface. A shackle can only ever give a point loading which will inevitably fail sooner. As there is much less metal in a shackle, early failure is unavoidable, and can only be compensated by using oversize ones.

Having said that, for most of us the chances of ever loading the rig to that extent in one lifetimes sailing is virtually nil, so the thing is largely academic anyaway, unless your name happens to be Ellen McA!
 
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