ribrage
Well-Known Member
I want to check the tension of my rigging, anyone any tips etc
Thanks in advance
ian
Thanks in advance
ian
tensioning rigging ?
- Thread starter ribrage
- Start date
chewi
Well-Known Member
get a "loos" guage and follow its advice.
Salty John
Well-Known Member
VicS
Well-Known Member
Download and study the "Hints and advice" pdf from Selden Mast AB from http://www.seldenmast.com/page.cfm?id=55...ename=595-540-E Hints & Advice.pdf
It's over 3.5 Mb so takes a while even on broadband.
It tells you all you are likely to want to know and how to tension the rig based on % elongation without a tension gauge. Probably quite adequate unless you are a sh*t hot racer.
It's over 3.5 Mb so takes a while even on broadband.
It tells you all you are likely to want to know and how to tension the rig based on % elongation without a tension gauge. Probably quite adequate unless you are a sh*t hot racer.
bobgoode
Well-Known Member
Good advice given above. Agree totally,
ribrage
Well-Known Member
thanks all
William_H
Well-Known Member
Well I'll stick my neck out and say don't take any notice of the advice in the above links with regard to static tension of wires.
People involved with metalurgy and rigging will tell you that to minimise the effect of fatigue on metal when it is periodically stretched that you put a prestretch into the metal. This correct science seems to have neen carried over into the advice on static tension of the rigging of a yacht. So taken in isolation if a wire has a max working load of 1000Kg then you should have it under static minimum stress of 10 to 15% of that or 100 to 150Kgs. And this will give the very best resistance to fatigue failure of the wire and associated fittings.
However we have our wire on a yacht. The load path for a cap shroud includes compression of the mast mast support and spreaders and tension in the chain plates through to the hull down to the mast support and including compression inwards of the hull.
A hull particularly f/g is quite flexible and so if you start to pply those loads especially to a backstay then the hull will often give a little. Your static tension will be on the hull 24/7. It is sometimes seen that a wooden hull will hog or start to bend upwards a the chain plates from too much static tension.
So my argument is that those who advocate such high static tensions are looking at the wire itself. Especially if the wire has been increased in size as appropriate to the boat the tension can be too much even damaging.
Basically static tension need only be enough to keep the rig from flopping about in other words tight bu easily able to be deflected by hand. The lee shrouds will always seem very loose when sailing. As I said the load path is long and has a lot of give in it.
So on a simple mast head rig the cap shrouds forestay and backstay should be adjusted to primarily locate the mast. ie vertical and with a susitable small rake. Use a spirit level for sideways adjustents and a halyard dropped vertically or by eye from a distance to set it fore and aft. If the backstay is adjustable under way then set for min tension.
The inner sidestays are then adjusted to make the mast straight (middle left or right) These should be reasonably tight then the inner forestay is tightened up enough to make the mast straight or with a slight bow middle forward. Some boats have the innner forestay adjustable under way. The idea is to increase the pull forward at the middle while also increasing the backstay tension to put more tension on the forestay but also to pull against the inner forestay to increse the mast bend. (flattens the mainsail)
However the amount of bend you can achieve is often quite small on a mast head rig.
Now a classic fractional rig is a complete load of interactions of stays. Again static load is just to keep the rig tidy.
The upper shrouds assuming aft swept spreaders are tensioned to make the mast vertical sideways and in conjunction with the forestay sets the rake. The upper shrouds are also tensioned enough to give the mast quite a lot of middle forward bend. This is because they bring pressure on the tips of the aft swept spreaders to force the middle of the mast forward. The inner shrouds are then tensioned to make the mast straight both sideways and fore and aft.
All this is done with no backstay tension which we hope is easily adjustable underway.
In stronger winds the backstay is pulled on. (the tension doesn't increase much simply the rig bends) this bends the entire length of the mast to give a gentle suitable bow from top to bottom. The extrra load on the top shrouds haelp by pushing forward the middle of the mast.
So on simple fractional rig the sidestays and forestay are kept somewhat tighter than a mast head rig as it is largely self supporting without backstay tension. Some racing yachts at my club have a highfield lever in the forestay to release static tension on the frational rig when the boat is not sailing.
Rigging adjustment is not a matter of cranking it on to a specified static tension it is a matter of adjusting stays in relation to one another to support and bend the mast as desired under sail.
And two other points SS rigging will stretch when warm and shrink in the cold. So love who believe in 15% of max load might like to check the rigging on a frosty morning. And it is far better to rpelacee rigging wire after 12 years than to try to minimise fatigue failure which to my understanding doesn't happen. (failure is from corrosion in strands or under swages)
There is my rant. Perhaps I have said it so many times people are becoming tolerant of the exentricities of olewill
Feel free to show me wrong but don't just quote ...... because he has written a book on sailing.
People involved with metalurgy and rigging will tell you that to minimise the effect of fatigue on metal when it is periodically stretched that you put a prestretch into the metal. This correct science seems to have neen carried over into the advice on static tension of the rigging of a yacht. So taken in isolation if a wire has a max working load of 1000Kg then you should have it under static minimum stress of 10 to 15% of that or 100 to 150Kgs. And this will give the very best resistance to fatigue failure of the wire and associated fittings.
However we have our wire on a yacht. The load path for a cap shroud includes compression of the mast mast support and spreaders and tension in the chain plates through to the hull down to the mast support and including compression inwards of the hull.
A hull particularly f/g is quite flexible and so if you start to pply those loads especially to a backstay then the hull will often give a little. Your static tension will be on the hull 24/7. It is sometimes seen that a wooden hull will hog or start to bend upwards a the chain plates from too much static tension.
So my argument is that those who advocate such high static tensions are looking at the wire itself. Especially if the wire has been increased in size as appropriate to the boat the tension can be too much even damaging.
Basically static tension need only be enough to keep the rig from flopping about in other words tight bu easily able to be deflected by hand. The lee shrouds will always seem very loose when sailing. As I said the load path is long and has a lot of give in it.
So on a simple mast head rig the cap shrouds forestay and backstay should be adjusted to primarily locate the mast. ie vertical and with a susitable small rake. Use a spirit level for sideways adjustents and a halyard dropped vertically or by eye from a distance to set it fore and aft. If the backstay is adjustable under way then set for min tension.
The inner sidestays are then adjusted to make the mast straight (middle left or right) These should be reasonably tight then the inner forestay is tightened up enough to make the mast straight or with a slight bow middle forward. Some boats have the innner forestay adjustable under way. The idea is to increase the pull forward at the middle while also increasing the backstay tension to put more tension on the forestay but also to pull against the inner forestay to increse the mast bend. (flattens the mainsail)
However the amount of bend you can achieve is often quite small on a mast head rig.
Now a classic fractional rig is a complete load of interactions of stays. Again static load is just to keep the rig tidy.
The upper shrouds assuming aft swept spreaders are tensioned to make the mast vertical sideways and in conjunction with the forestay sets the rake. The upper shrouds are also tensioned enough to give the mast quite a lot of middle forward bend. This is because they bring pressure on the tips of the aft swept spreaders to force the middle of the mast forward. The inner shrouds are then tensioned to make the mast straight both sideways and fore and aft.
All this is done with no backstay tension which we hope is easily adjustable underway.
In stronger winds the backstay is pulled on. (the tension doesn't increase much simply the rig bends) this bends the entire length of the mast to give a gentle suitable bow from top to bottom. The extrra load on the top shrouds haelp by pushing forward the middle of the mast.
So on simple fractional rig the sidestays and forestay are kept somewhat tighter than a mast head rig as it is largely self supporting without backstay tension. Some racing yachts at my club have a highfield lever in the forestay to release static tension on the frational rig when the boat is not sailing.
Rigging adjustment is not a matter of cranking it on to a specified static tension it is a matter of adjusting stays in relation to one another to support and bend the mast as desired under sail.
And two other points SS rigging will stretch when warm and shrink in the cold. So love who believe in 15% of max load might like to check the rigging on a frosty morning. And it is far better to rpelacee rigging wire after 12 years than to try to minimise fatigue failure which to my understanding doesn't happen. (failure is from corrosion in strands or under swages)
There is my rant. Perhaps I have said it so many times people are becoming tolerant of the exentricities of olewill
Feel free to show me wrong but don't just quote ...... because he has written a book on sailing.
VicS
Well-Known Member
[ QUOTE ]
Well I'll stick my neck out
[/ QUOTE ] well Selden masts are a major spars supplier and I would regard their advice as sound.
Fractional rigs are complicated and the setting up depends on the extent to which the spreaders are swept back, I think you will find. Its all covered in the Selden manual.
Regarding your comments about the expansion and contraction of the wire in warm/cold weather. One point usually made is that aluminium has higher coefficient of expansion than stainless steel so the argument goes that with an ally mast the rig will actually slacken in cold conditions and tighten when warm! However I looked up the relevant figures recently and did the calculations concluding that the expansion and contraction involved over normal temperature ranges is insignificant compare with the extent to which the wires are stretched to give the normal tensions.
You'll find the figures HERE on the National Physical Laboratory website if you feel like doing the calculations yourself!
Well I'll stick my neck out
[/ QUOTE ] well Selden masts are a major spars supplier and I would regard their advice as sound.
Fractional rigs are complicated and the setting up depends on the extent to which the spreaders are swept back, I think you will find. Its all covered in the Selden manual.
Regarding your comments about the expansion and contraction of the wire in warm/cold weather. One point usually made is that aluminium has higher coefficient of expansion than stainless steel so the argument goes that with an ally mast the rig will actually slacken in cold conditions and tighten when warm! However I looked up the relevant figures recently and did the calculations concluding that the expansion and contraction involved over normal temperature ranges is insignificant compare with the extent to which the wires are stretched to give the normal tensions.
You'll find the figures HERE on the National Physical Laboratory website if you feel like doing the calculations yourself!
mikejames
Well-Known Member
Get either the Loos gauge or another similar.
Setting up rigging at 10% of load will bend the boat if its old, floppy or indifferently put together and new. I had to beef up inside my then 20 year-old Westerly GK24 which has a fractional rig, and the shrouds pull the deck up.
But what is worse is if the tensions are wrong is the fact that the mast will bend into an interesting S shape if the lowers are not setup properly. I saw a very interesting shape at the instant that the Storm 33 alongside in a race lost its mast in a squall and the sea came up to the cockpit coaming on the downhill side ..
If you combine this with almost-slack leeward shrouds -- that bendy hull will not help, then the shock-loads on the mast as the boat bounces the shroud loose and slack again are not healthy. Something has hammered the aft end of the spreader bases into Forethought's mast leaving small dimples. Probably flapping around with low rig tension before I had the boat.
I like the gauge because it lets me make the tensions similar to port and starboard, although I tend to aim lower than the 15% limits because of the bendy hull. So upper shrouds are almost twice as tight as lowers with the boat upright. Then the mast bend goes nicely forward with the backstay and the mainsheet.
The gauges could be DIY'd as the one I have could be made out of two strips of stainless, some bolts and a spring balance and a ruler.
Basically you pull the shroud sideways and then measure how much force it took to bend it a certain amount.
Setting up rigging at 10% of load will bend the boat if its old, floppy or indifferently put together and new. I had to beef up inside my then 20 year-old Westerly GK24 which has a fractional rig, and the shrouds pull the deck up.
But what is worse is if the tensions are wrong is the fact that the mast will bend into an interesting S shape if the lowers are not setup properly. I saw a very interesting shape at the instant that the Storm 33 alongside in a race lost its mast in a squall and the sea came up to the cockpit coaming on the downhill side ..
If you combine this with almost-slack leeward shrouds -- that bendy hull will not help, then the shock-loads on the mast as the boat bounces the shroud loose and slack again are not healthy. Something has hammered the aft end of the spreader bases into Forethought's mast leaving small dimples. Probably flapping around with low rig tension before I had the boat.
I like the gauge because it lets me make the tensions similar to port and starboard, although I tend to aim lower than the 15% limits because of the bendy hull. So upper shrouds are almost twice as tight as lowers with the boat upright. Then the mast bend goes nicely forward with the backstay and the mainsheet.
The gauges could be DIY'd as the one I have could be made out of two strips of stainless, some bolts and a spring balance and a ruler.
Basically you pull the shroud sideways and then measure how much force it took to bend it a certain amount.
VicS
Well-Known Member
[ QUOTE ]
I like the gauge because it lets me make the tensions similar to port and starboard
[/ QUOTE ] Surely you cant get the tensions different on one side compared with the other, at least not without pulling the mast into a weird shape. The physics just doesn't allow it.
I've often thought about the posibility of making a tension gauge but how would you calibrate it?
I like the gauge because it lets me make the tensions similar to port and starboard
[/ QUOTE ] Surely you cant get the tensions different on one side compared with the other, at least not without pulling the mast into a weird shape. The physics just doesn't allow it.
I've often thought about the posibility of making a tension gauge but how would you calibrate it?
William_H
Well-Known Member
Yes thanks Vic I must have been having a minor brainstorm i forgetting the mast expansion or perhaps I was thinking wooden masts.
Yes certainly a mast must be held well enough to prevent pumping in any direction. The spreaders on a fractional rig must be very robust in the aft swept direction. My little boat lost its first mast due to a spreader base failure.
OK so lets not throw away Mr Seldon's advice but I would still like to urge a note of care in overtensioning. olewill shuffling backwards heading for his boat to lay low for a few hours. 30 degrrees and 15 knots this evening beaut for a twilight race.
Yes certainly a mast must be held well enough to prevent pumping in any direction. The spreaders on a fractional rig must be very robust in the aft swept direction. My little boat lost its first mast due to a spreader base failure.
OK so lets not throw away Mr Seldon's advice but I would still like to urge a note of care in overtensioning. olewill shuffling backwards heading for his boat to lay low for a few hours. 30 degrrees and 15 knots this evening beaut for a twilight race.
chrishelen
N/A
Hi Ian,Dont pay money out to adjust the rigging on your 50ft rusty ketch,go to the Eventide owners site,then open the hints and tips page,then click on "setting up the rig"should tell you all you need to know,hope this helps.Chris.
VicS
Well-Known Member
[ QUOTE ]
30 degrrees
[/ QUOTE ] Alright , don't rub it in. /forums/images/graemlins/laugh.gif
30 degrrees
[/ QUOTE ] Alright , don't rub it in. /forums/images/graemlins/laugh.gif
ribrage
Well-Known Member
thanks guys
the main reason for checking it is that the back stay for the main mast port side ''feels'' slacker than the others i can see no obvious reason for this (yet).
so wanted to retension it and see what breaks, all the chain plates are welded to the hull in 8mm steel which are visible and nothing has moved to my knowledge
??
the main reason for checking it is that the back stay for the main mast port side ''feels'' slacker than the others i can see no obvious reason for this (yet).
so wanted to retension it and see what breaks, all the chain plates are welded to the hull in 8mm steel which are visible and nothing has moved to my knowledge
??
William_H
Well-Known Member
high Vic just to make you feel better the sail was a bit of a disaster. Plenty of wind got out no 3 jib and put a reef in main. One of my helpers seems to have st7uffed up the bowline on the jib halyard. Yes it let go and halyard dissapeared into the mast. Ok says I we will use the spin halyard and yes the little boat went beautifully until near halfway when the spin halyard broke. I did suggest they crank it on to avoid stretch in the poly rope.
So we cam home under main alone and I was pleasantly surprised how well it went to windward with just reeded main.
New job today. Pull mast down and replace 2 halyards....bugger olewill
So we cam home under main alone and I was pleasantly surprised how well it went to windward with just reeded main.
New job today. Pull mast down and replace 2 halyards....bugger olewill
chrishelen
N/A
Unlucky! at least you were warm. /forums/images/graemlins/cool.gif
