we replaced our 9/32nds uppers, headstay, backstay and 1/4 lowers and cutter/inner forestay with 5/32nds. What would be a suggested begining tension for this setup with the new shrouds having a higher breaking load.
advice needed,Dock side tension for larger/oversize shrouds
- Thread starter Water Bill
- Start date
Just because you increased the size of the standing rigging would be no reason to increase the load on the boat... that would over strees the boat as well as diminish any "overkill" you wanted by going to bigger rigging....
The answer would be to tension the rig to the spec of boat rather than tension the rigging to its spec.... or, tension the new rigging to the spec of the original standing rigging...
After rereading your post, i must modify what i said earlier... accordint to what you wrote it would seem you went DOWN in rigging size.... not sure what to say about that other than you have weakened the rigging...
I tend to agree with Centerline about not increasing the load on the boat.
FYI, here is tension recommended by Loos Scale for the sizes you had, which is what I have. Using the Loos gauge I have been setting mine a tad under the scale and have had no issues whatsoever.
Shroud Diameter Ft/ lbs LOOS SCALE
Lower Shroud 9/32’’ 1200 46/47
Middle & Upper Shrouds 1/4‘’ 1060 40/41
Forestay 9/32’’ 1200 46/47
Backstay 9/32’’ 1200 46/47
Backstay / 2 1/4‘’ 1060 40/41
FYI, here is tension recommended by Loos Scale for the sizes you had, which is what I have. Using the Loos gauge I have been setting mine a tad under the scale and have had no issues whatsoever.
Shroud Diameter Ft/ lbs LOOS SCALE
Lower Shroud 9/32’’ 1200 46/47
Middle & Upper Shrouds 1/4‘’ 1060 40/41
Forestay 9/32’’ 1200 46/47
Backstay 9/32’’ 1200 46/47
Backstay / 2 1/4‘’ 1060 40/41
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Re: advice needed,Dock side tension for larger/oversize shro
I agree with Claude. The Loos Scale is probably one of the wisest investments you can make for boat. Not only for proper "dockside" tension, but once you get the tuning just right (performance-wise) you can make a note of the tensions and repeat the settings every year.
I agree with Claude. The Loos Scale is probably one of the wisest investments you can make for boat. Not only for proper "dockside" tension, but once you get the tuning just right (performance-wise) you can make a note of the tensions and repeat the settings every year.
I would love to have a Loos Scale. But on the West Coast we don't need to take down the mast every winter and put up again every spring. And the guages from what I remember are somewhat pricey. Particularly for the models needed to accommodate larger diameter wire.
An alternative for achieving the appropriate tension is "the folding rule" method which is described in detail on page 29 of this pdf by Selden:
http://www.seldenmast.com/files/595-540-E.pdf
On the page is a listing of wire diameter and breaking loads for each diameter. Use the table on the page 29 to determine how to use the folding rule method for your desired tension for each size wire. Essentially the folding rule method is that after tensioning hand-tight, then using normal turnbuckle hand tools from there, each 1 mm of stretch over a two meter length of wire corresponds to 5% of the breaking load. So for your oversize wire installation, you may need for example 2mm stretch over two meters to achieve the same lbs (or kgs) of tension as would require 3mm of stretch for the smaller diameter wire. You can do the actual calculations.
An alternative to a folding ruler, is instead simply cut a strip of (say) quarter round molding to exactly two meters length. Tape that to the shroud. Making several of these two meter sticks and taping on to the various shrouds being tensioned will save time of constantly removing and replacing as shroud tensions are being tweaked.
The rest of this PDF includes all sorts of other very useful stuff about rigs and tuning.
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Re: advice needed,Dock side tension for larger/oversize shro
Thank's for the needed advice. the shroud are 5/16 (my mistake). Strange that there is not much useful info about this scenario on the net. I bought a PT-3 Loose Gauge after a local rigger advised to "just" pull on the schroud, you'll know when they're tight enough. I invisioned leaking ports and non-opening doors or launching the mast through the keel. The final adjustment will be under sail. Thank's again
Thank's for the needed advice. the shroud are 5/16 (my mistake). Strange that there is not much useful info about this scenario on the net. I bought a PT-3 Loose Gauge after a local rigger advised to "just" pull on the schroud, you'll know when they're tight enough. I invisioned leaking ports and non-opening doors or launching the mast through the keel. The final adjustment will be under sail. Thank's again
Re: advice needed,Dock side tension for larger/oversize shro
The uppers on Midnight Sun were 1/4". I replaced them with 9/32" discontinous rod, and added 1/4" intermediates. ( from the spreaders to the attachment point where the runners used to go) I retained the 1/4" lowers. My rig is a rock. I know that rod for the same size is much stronger than wire, but 5/16th sounds like way overkill. We fly a 1460 square foot spinnaker in 25 kts and the rig doesn't move. Before the change, the masthead would fall off 2 feet which was VERY scary. The heavier the wire the less the stretch. You might even be able to lessen the static loads on the boat. One thing we do is to loosen the back stay to where it is floppy to unload the boat when we are not using it.
The uppers on Midnight Sun were 1/4". I replaced them with 9/32" discontinous rod, and added 1/4" intermediates. ( from the spreaders to the attachment point where the runners used to go) I retained the 1/4" lowers. My rig is a rock. I know that rod for the same size is much stronger than wire, but 5/16th sounds like way overkill. We fly a 1460 square foot spinnaker in 25 kts and the rig doesn't move. Before the change, the masthead would fall off 2 feet which was VERY scary. The heavier the wire the less the stretch. You might even be able to lessen the static loads on the boat. One thing we do is to loosen the back stay to where it is floppy to unload the boat when we are not using it.
Loosening the rigging so the boat an relax between uses is not conducive to a sound and tight boat.... the allowed flexing is not good for it....
The rigging and boat is meant to be and should be tensioned and left that way.
It sould only be unloaded during hull or rigging repairs or when unstepping the mast..
Basically, by relaxing it, rhe retensioning it, you are inducing the same effects as "oil canning"..... which is unnecessary and unwanted flexing and stress in the hull....which is also the exact same effect caused by someone sailing the boat with the rigging that is too loose....
A happy boat is a tight boat that remains tight....
Re: advice needed,Dock side tension for larger/oversize shro
I have to respectfully dissagree with Centerline. Leaving a rig loaded, will in time bend the boat into a banana. Many boats from Thistles to two tonners are built with ways to unload the boat between hard sailing. Fiberglass will and does take a "set". There is a reason that they make backstay adjusters and hyfield levers.
I have to respectfully dissagree with Centerline. Leaving a rig loaded, will in time bend the boat into a banana. Many boats from Thistles to two tonners are built with ways to unload the boat between hard sailing. Fiberglass will and does take a "set". There is a reason that they make backstay adjusters and hyfield levers.
I suppose if you have a weak and unsupported hull it can bend into a banana... if the hull is strong, the liner and bulkheads tabbed properly and the deck is sound, the hull should be more like a large fiberglass football... and nearly impervious to distortion.... the boat is designed to withstand a constant load, but loosening and tightening causes stress...
Skippers sailing around the world for a couple of years at a time have no desire for their boats to be banana shaped, yet they still dont see any need or reason to loosen their rigging. and yet, neither are they constantly taking up slack in the rigging to compensate for the banana shape.
do you feel this is hard on the boat for them to treat it like that...
EDIT.... I see you mention thistles and two tonners.... smaller boats.
you are very correct that some of them DO need their standing rigging loosened during storage, some of the owners manuals will give this instruction, but this is not true of bigger boats.....
You will now have a 'conundrum' of head sail shaping errors - principally on the headsail. Long winded diatribe follows:
The 37c does not have 'intermediate' stays (from cap rail to 'hounds' of cutter stay attachment, nor running backstays, to react/support the 'cutter-stay' connection; and you only have ONE backstay ... a backstay that is supporting TWO sail loaded wires: cutter-stay & forestay.
9/32 = 10,400 lbs. breaking strength
5/16 = 10/32 = 12,500 lbs. breaking strength
Run your new rigging for caps and lowers, etc. at the 'old' tension levels that was for 9/32" ... adjust the new wire in accordance to POUNDS not % load, those POUNDS load should be the exact same as what you had for the 9/32. Your boat's chainplates and mast attachments werent designed for the extra 2500lb. load (at maximum breaking strength of the wire).
The conundrum will be that the heavier wire at the forestay and cutter-stay, running at less than normal 12% load (10,400/12,500 X .12) = 9-10% will now have a bodacious SAG both a sag aft and a sag off to leewards when beating. Youre NOT going to be able to 'point' very well with such a SAG in your forestay and cutter stay wire.
Simple solution:
Run your new 5/16 for caps and shrouds at 10%
Run you new 5/16" headstay at 10-12+%
Run your new cutter stay at 5% when flying a staysail 'under' any topsail/jib/genoa.
Run your new backstay at 18-20%
Reason: Wire tension is vitally important to head-SAIL SHAPE.
Heavier new wire will hold the rig upright at the lower tensions (~10%) for the caps and lowers. You dont want to overload the 'fore' wires nor the backstay; at 20% backstay tension you still have 10% 'cushion' before the wire 'yields' / permanently stretches (@~30%).
Reson cont'd.: The alternative is to have the luffs on both the headsail AND the staysail recut to fly on a headsail/staysail combo being flown on 10% tensioned wire. OR simply run both headstay wires at 12% ... and routinely WATCH those chainplates and their attachment to the hull for signs of premature 'breakage'.
FWIW - most cutter rigged boats NEED the headstay to be VERY tight and the 'cutter-stay' to be slightly slack. Only tension-up on the 'cutter-stay' when only the staysail is being flown (no 'headsail'/topsail). If both forestay and cutter stay are equally tensioned, 'most' of the combined 'strain' of sail loading will be in the cutter-stay and the HEADSTAY will begin to 'unload'. The unloaded headstay will cause the wire to SAG off to leewards and the boat will increase its heel, slow down, will begin to skid to leewards .... and the skid will mimic 'weather helm'.
Suggested Rx:
caps and lowers - 10%
Forestay - 12+% !!!!!
'cutter stay' - 5%, except when flying staysail only then 'tight'.
Backstay - 18-20% (but, attach your tension gage to the backstay and validate that its tension does not come close to 30% when the boat is heeled over to ~45° !!!! 30% is where such wire begins to permanently stretch - yield !!!!!)
Cutter rigs are a PITA 'bytch' to rig tune and have the boat still 'point'. Cutters 'point' miserably when the headsail luff and the headstay wire is grossly sagging off to leewards.
Here's how to adjust backstay/headstay tension on a cutter rig ... or any other sailboat. Just dont let the wire get close to or exceed 30% tension when 'sailing':
http://www.ftp.tognews.com/GoogleFiles/Matching Luff Hollow.pdf
Re: advice needed,Dock side tension for larger/oversize shro
To my friends RichH and Centerline,
First, The 37c does indeed come equiped with running backstays. Second, the average length of a two tonner is 42 feet. I was crew on the two tonner "Agressive", an aluminum boat designed by Carter, and we were instructed to unload the boat with the headstay and backstay adjusters whenever we put the boat away, whether we sailed to for an afternoon or a week. I have seen Hinkleys bent so badly that interior doors no longer shut.
To my friends RichH and Centerline,
First, The 37c does indeed come equiped with running backstays. Second, the average length of a two tonner is 42 feet. I was crew on the two tonner "Agressive", an aluminum boat designed by Carter, and we were instructed to unload the boat with the headstay and backstay adjusters whenever we put the boat away, whether we sailed to for an afternoon or a week. I have seen Hinkleys bent so badly that interior doors no longer shut.
Re: advice needed,Dock side tension for larger/oversize shro
Thanks for the further advice, but let me add that the chain plates increased from 1.5" by .25" to 2.0" by .375" with .50" bolts.The terminals are norseman. The mast tang/plates for the uppers and lowers are 3/16th as well as the mast head toggles with 5/8th pins.
Thanks for the further advice, but let me add that the chain plates increased from 1.5" by .25" to 2.0" by .375" with .50" bolts.The terminals are norseman. The mast tang/plates for the uppers and lowers are 3/16th as well as the mast head toggles with 5/8th pins.
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