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post #1 of 9 Old 06-06-2016 Thread Starter
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Looking for rig tension numbers on a Crown 34

Hi Guys and gals,
I'm looking for rig tension numbers for our Crown 34, can anyone help with where to go fro this??

Keeping in mind that the last Crown 34 was produced in 1979.

Thanks, Pete
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post #2 of 9 Old 06-06-2016
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Re: Looking for rig tension numbers on a Crown 34

I think the tensions are based on wire size, not necessarily boat design. Do you have a loos gauge on hand?

Ron

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Re: Looking for rig tension numbers on a Crown 34

Selden tuning manual, available online as PDF.
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Re: Looking for rig tension numbers on a Crown 34

Wire tension is based on wire size. Here's 2 reference sources for the direction of 'how to', including 'how to' without a tension gages but by using a yard/meter stick:

THE most definitive rig tension 'guide' available on the internet ... download/copy it: http://www.riggingandsails.com/pdf/selden-tuning.pdf

and a summary of 'manual and without a tension gage' rig tuning from that above link
https://www.sailnet.com/forums/gear-m...-your-rig.html
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Re: Looking for rig tension numbers on a Crown 34

The Selden wire tension guidelines are what many people use. I have tried tensioning my rig to those specs but have backed off, thinking they were WAY, WAY too tight. Maybe for racing, where you want to fine tune sail shape, these specs are good but for cruising I believe they are unnecessary. The tension is such, with wire stretched that tight, that deck distortion under the mast is a real possibility on any surface the mast unloads upon. I use the old method of tuning my rig under sail, adjusting the stays and shrouds so that there is no slack on the lee side during a beam reach in a good wind. I really can't see the purpose of any more tautness than that. If the mast is straight under a good load, why overstress the entire structure, fittings, swages, wire, deck, and chainplates by applying excessive tension.

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Re: Looking for rig tension numbers on a Crown 34

FWIW -
Please consider that the 'set' and 'shape' of your sails, especially those that are on a forestay, or headstay, etc. entirely depend the tension in that wire. Just about any loft will, 99% of the time, build your sails to these 'expected' tensions for normal routine sailing in 12-15kts of wind based on the normal 'sag' of the wire under those conditions; ..... unless one specifies other than this accepted 'normal' wind speed range for normal conditions of your sailing venue.
If the headstay/forestay tension are not 'close' to the 12-15%, when sailing in 12-15kts, don't expect to be able to 'point' as well as with a normal/spec. tensioning.

Also, just about 'any' sail loft will also consider the amount of normal expected 'pre-bend' of the mast .... if no pre-bend; then expect a mainsail that's s-l-o-w-e-r while causing greater heel than 'normal' - a 'cranky' boat thats more 'easily set on her ear' when in gusts, than with sails attached to 'spec' wire tensions, etc.

hope this helps
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Re: Looking for rig tension numbers on a Crown 34

Quote:
Originally Posted by RichH View Post
FWIW -
Please consider that the 'set' and 'shape' of your sails, especially those that are on a forestay, or headstay, etc. entirely depend the tension in that wire. Just about any loft will, 99% of the time, build your sails to these 'expected' tensions for normal routine sailing in 12-15kts of wind based on the normal 'sag' of the wire under those conditions; ..... unless one specifies other than this accepted 'normal' wind speed range for normal conditions of your sailing venue.
If the headstay/forestay tension are not 'close' to the 12-15%, when sailing in 12-15kts, don't expect to be able to 'point' as well as with a normal/spec. tensioning.

Also, just about 'any' sail loft will also consider the amount of normal expected 'pre-bend' of the mast .... if no pre-bend; then expect a mainsail that's s-l-o-w-e-r while causing greater heel than 'normal' - a 'cranky' boat thats more 'easily set on her ear' when in gusts, than with sails attached to 'spec' wire tensions, etc.

hope this helps
Yes, I agree that the head/backstay tension has a great effect on pointing ability. It needs to be close to wire spec. There is no way to get a headsail shaped correctly with a loose headstay. It is the inner/outer shroud tension I question. When I tuned my shrouds up to spec using the wire stretch m/m method it seemed that over time there would be so much force exerted down that the boat structure would eventually HAVE to deflect even with the additional laminations I've added to the header. Something had to eventually give, whether it be the chainplate thru-bolts, the deck stepped deck surface or the supporting header. I suppose if you were to loosen turnbuckles when not in use it would suffice to eliminate the long-tern stress but that's just too time consuming.

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Re: Looking for rig tension numbers on a Crown 34

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Originally Posted by smurphny View Post
I use the old method of tuning my rig under sail, adjusting the stays and shrouds so that there is no slack on the lee side during a beam reach in a good wind. I really can't see the purpose of any more tautness than that.
You are correct.

I am ever skeptical of pre-loading to some percentage of the wire breaking strength without more input from the designer. In fact I no longer use a tension gauge but rather "do what works, what gets the job done, and not a turn more." Different designers use different wire size safety factors. Wire sizes get altered after manufacture. Rigs come from various spar builders. Etc etc. The proper tune is what gives the proper result.

Tension gauges might be handy for returning to some previous setting. However measuring the gap in the screws is easier and more accurate.

Preload on shrouds doesn't bend (most) boats much. It is the preload on the backstay that bends boats and cracks the furniture. Thus the utility of an easily adjustable backstay, or whatever tensions the forestays.

"...there are two kinds of opinions, those based upon tradition ... and those having something in their favor." B. Russell
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Re: Looking for rig tension numbers on a Crown 34

Thanks guys for all the input, suggestions, caveats, et al. Very much appreciated.

The rigging loads were all on the light side, but OK. I had a friend come with an older Loos gauge.

More importantly, a meeting with the repair shop foreman about the mast step and deck to mast connection alerted me to some other potential problems. We may not have a "mast to deck" connection, so that needs to be investigated further. There is evidence of a previous connection. There are no wedges!?!? The mast is located with some thick teak collar pieces, ceiling mounted, that are through-bolted to the mast collar, with all the halyard pulleys on deck. So far, no evidence of any connection of mast to deck. This seems to be an odd method of locating the mast in the deck hole. At least not in conformance to current wedging practices.

Certainly, I will not be tensioning the rig until these anomalies are resolved.

The mast step is a bit odd was well. There are two 1/2 inch thick pieces of 6061-T6 stacked to make a bridge from hullside to hullside. These plates are bedded into an epoxy slurry, either side of center. This creates a bridge that is unsupported directly below the mast step.

This aluminum bridge has deformed slightly, and should be supported under the bridged area. We cranked up the hydraulic backstay to 1500 lbs and although the plates did not deform or bend, I'm sure with the rig under sail things would be different.

Anyway, I suppose it will always be a work in progress, ....Oh dear, the main bilge pump just failed..... another day, another Boat Unit$$$

Thanks again guys, Pete
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