Shroud tensions

DrJudyB · Apr 16, 2020

The Capri 22 is a typical fractional rig, with one set of aft swept spreader. For all such rigs, the uppers are tighter than the lowers .

Added on editting: BTW, the cap shrouds s on a Catalina 22 masthead rig should be tighter than the lowers, too. It's physics and it applies to all masthead and fractional rigs.

dfnomad · Apr 16, 2020

2005 TRFK
Does anyone have actual Loos guage numbers that they use on their boats, for the upper and lower shrouds? Reading the Ulman and North tuning guides they both speak of 30 - 32 on the uppers and then tighten a couple of turns for heavier winds. 32 equates to only about 200 lbs of wire load on the 5/32 wire. My leeward upper shrouds would be very floppy at that setting even in 10 kts of wind.

The Selden tuning guide stresses the importance of the cap shrouds always being tight .. and infer guage reading of around 20% of breaking strength; which would be approx 45 on the guage.

Last Fall my leaward upper shrouds were set at about 42. That seemed nice and firm in most conditions. At 42 that is approx 12.7% of the breaking strength of the wire.

Anyone have actual data?
Dave

DrJudyB · Apr 16, 2020

dfnomad said:
Anyone have actual data?
Dave

Here you go, data from two different lofts.

Capri 22 Tuning Guide | North Sails

Thanks for your purchase of North Sails for your Capri 22. We have designed these sails to be fast, easy to use and long lasting. The following tuning guide is... Read More

www.northsails.com

One Design Tuning Guides | Ullman Sails

ullmansails.com

But be aware that you have to set the the amount of prebend you tune into the mast according to how your sailmaker built the sail. Not all Capri 22 sails have the same luff curve designed into them. I usually built my Capri mainsails to fit 1.5 inches of prebend in the mast.

Judy B
Retired sailmaker.

dfnomad · Apr 16, 2020

Thank you for the reply Judy B. I did mention in my original post that I have read those two Guides. And yes .. I am aware of the pre-bend requirement.

The Ullman Guide says: "On the Loos Model-A tension gauge, the lower shroud tension should be around 5." (for our 1/8" wire .. the guage doesn't even show a load reading that low).

The North Guide says 20 for the lowers at the same wind speed.

Wind Speed	Upper Shroud Tension	Lower Shroud Tension	Head Stay
0-5	28	18	Max rake
6-9	31	20	Max rake

So .. what am I missing ?

I welcome all comments of course; but I posted here hoping that someone with an actual Capri 22 FKTR and a Model-A Loos guage could share their actual numbers.

cheers and hope everyone is staying safe ..
Dave

MikeDVB · Jun 20, 2023

JohnK Austin TX said:
UPDATE: Tested both options this weekend.

at the dock:
1- loosened all 4 shrouds (not completely flopping but barely hand-tight) , detached the boom, released split back stay
2- made sure the mast was side-to-side centered + made sure rake was correct
3-a- uppers tighter: uppers:31 / lowers:23 + used split back-stay to bend the mast above the spreaders eye-balling

Sailed:
about 8-11 knots winds leeward shrouds were too tight, loosened all 4 about 2 turns each. tension was right but upwind speed was eeehhh and could not point very well.

back at the dock:
3-b- lowers tighter: uppers:21/ lowers:20 + checked to make sure the mast bend above the spreaders was about the same

Sailed again:
same winds. leeward shrouds were nicely loose, no issues with head-sail sagging. Boat pointed better and faster

Result:
My boat speed was 2-4 knots faster when lower shrouds are tighter than the uppers. Owners Manual, rigging section also calls for tighter lowers. Having looser uppers allowed me to dump air in the upper part of the mainsail when winds were at about or more than 14knots. Less heel and more boat speed.

I will stick with this tune.

I know this is an older post - I happened across it while trying to sort out tuning on my 2007 Capri 22.

Are you using a Loos PT-1 for these numbers? I don't have a 'Model A' and I'm not sure how they compare.

In light winds my boat seems to sail fine but I'm just getting into racing and doing what I can to tune it better.

I'm getting a lot of weather helm that I'm trying to reduce. I do have a wing keel and from what I understand I want no rake to my mast - but I'm not sure if that's before tensioning the upper and lower shrouds or after from the guides I've read.

I took 5 turns off of my backstay and that seemed to help but it's still not where I want it to be. I'm not sure how loose is too loose for the backstay. I do have a CDI Flexible Furler on the front [came with the boat] so if I were to do any adjustments to the headstay I'll have to pull the headsail and raise the furling drum - not a huge deal but ideally I'd like to avoid it.

Roy Briscoe · Wednesday at 8:08 AM

MikeDVB said:
I know this is an older post - I happened across it while trying to sort out tuning on my 2007 Capri 22.

Are you using a Loos PT-1 for these numbers? I don't have a 'Model A' and I'm not sure how they compare.

In light winds my boat seems to sail fine but I'm just getting into racing and doing what I can to tune it better.

I'm getting a lot of weather helm that I'm trying to reduce. I do have a wing keel and from what I understand I want no rake to my mast - but I'm not sure if that's before tensioning the upper and lower shrouds or after from the guides I've read.

I took 5 turns off of my backstay and that seemed to help but it's still not where I want it to be. I'm not sure how loose is too loose for the backstay. I do have a CDI Flexible Furler on the front [came with the boat] so if I were to do any adjustments to the headstay I'll have to pull the headsail and raise the furling drum - not a huge deal but ideally I'd like to avoid it.

Old thread but I didn’t see a response to your question. The back stay should be loose until about 10 knots or so when you start to need to depower the sails. The back stay on fractional rigged boats with swept back spreaders is for depowering the sails, it doesn’t help hold the mast up.