Adjusting standing rigging

[c_witch]

Hiee all,

Well our boat is pretty nearly finished now and we are looking at launching the Sunday after this one. We are attempting to set up the standing rigging on this boat. Its a 22 foot swing keel. My questions being 1) When the boat is in the water should I expect the bottom of the keel box to be level? Consider this to be an unloaded boat. 2) I have seen that 0 to 5 degree's aft rake to the mast is favorable? We are trying to set the aft and forestay so the length of the aft stay will be correct when it comes time to re-step the mast when we launch. 3) I have not found any information on what the tension should be on the aft stay ? We do have a tension gauge for our standing rigging it is by the way 1/8'' wire rope 1/19 s/s.

According to the booklet that came with the gauge the forestay should be set to 320 lbs and the shrouds set to 240 lbs.

Thanx,
c_witch

 

[ITMaster]

I generally set the tension of the shrouds to about 10% of the full yield tensile strength (break) of the wire.

 

[Ray Bowles]

I forget where I found this articule on rig tuning but it is the best I have ever seen. It addresses everything. I am a computer idiot so I'll write this address longhand and you will have to enter it yourself. Enjoy tuning your rig. I have found it makes my boats sail much better, flatter and faster. I also use a Loos gauge.
Tuning address: www.riggingandsails.com/pfd/selden-tuning.pdf
Wow, I see the site did the address itself. Go figure.
Ray

 

[Stu Jackson]

Ray, the link didn't work for me. Suggest instead of typing it in, you cut & paste it from the site's url.

 

[RichH]

Seldén rig tuning (applies to ALL masts): http://www.seldenmast.com/frameset.cfm?id=6740&randnum=860279119 .... then click on "hints and advice" (english) to download. This is probably the MOST COMPREHENSIVE mast tuning / mast rigging advice on the internet.

Then for sail 'shape' and trim fanatics ... to set the proper amount of backstay tension to be in exact accordance to wind/wave conditions (for 'todays' sailing conditions): www.ftp.tognews.com/GoogleFiles/Matching Luff Hollow.pdf

FWIW and as applies to 'most' sloop rigs (mast located at ~30% of LOA from the bow) ....
If no roller furling, set the *forestay* tension to 15% breaking strength of the wire - use the tuning gage on the *forestay* as you adjust the backstay.
If roller furling jib .... Because of the geometry at which the forestay makes a 'sharper' intersect angle to the top of the mast set the *backstay* at 12% (to get 15% in the forestay) ... whatever tension you desire in the forestay DIVIDE that number by 1.3 = backstay tension.
If you set the backstay tension in order to get to the 'basic' forestay tension, you will overtension the forestay *on most sloops*. The real 'limit' for any rigging should be not to exceed 30% tension under 'dynamic sailing loads'. So, on a 'true' sloop that means that the BACKSTAY should not exceed ~22% max tension for 'long periods of time' .... or you increase the risk of *fatigue failure* of the forestay/backstay.

For rigs that have the mast positioned at other than at ~30% LOA, you really should calculate the set up tensions by the use of 'trigonometry'. For most 'sloops', whatever you tension the backstay, the forestay will result in ~1.3X 'greater' tension when measuring only the tension on the backstay.

 

[cephius (Dave)]

Ray just mistyped 'pdf' in his link. (Help from an IT geek)

http://www.riggingandsails.com/pdf/selden-tuning.pdf

 

[Bob S]

If you set the backstay tension in order to get to the 'basic' forestay tension, you will overtension the forestay *on most sloops*. The real 'limit' for any rigging should be not to exceed 30% tension under 'dynamic sailing loads'. So, on a 'true' sloop that means that the BACKSTAY should not exceed ~22% max tension for 'long periods of time' .... or you increase the risk of *fatigue failure* of the forestay/backstay.

I read through Seldon's tuning helpfull hints and had a question. I step the mast every season and have tuned by feel. I just ordered a Loos gage. I have a split backstay. Would you adjust the split @ 11% to get 22% ?

 

[Ray Bowles]

Bob, I have tried to set my split backstay by measuring the wire above the split. This gives a better reading but even measured there I never got a good reading so I set the rake and then adjust the backstay tension until I get about 4 inches if deflection on the forestay. The deflection is on bare wire without a sail flying. Doing it that way gives about 6 inches with sail up. This allows me to pull on the split backstay and flatten out the forestay and stiffen up the jib. There again this is on a 23' boat that sails off a trailer but it works very nicely.
Cephius, thanks for the help.
Ray

 

[RichH]

I read through Seldon's tuning helpfull hints and had a question. I step the mast every season and have tuned by feel. I just ordered a Loos gage. I have a split backstay. Would you adjust the split @ 11% to get 22% ?

The 'technical answer' is NO. A split backstay system with each 'leg' at half the desired tension will not result in double the tension in the single backstay of the configuration. Either apply your tension gage on the 'single' part (above the legs) when adjusting .... or provide me with the approximate angles of the backstay system (angles that the backstay legs make with the single part that runs to the mast .... and I'll calculate/provide you with the correct tensions for the 'legs' to attain the desired tension in the single part - Trigonometry !!!! Just a side view + stern view drawing that shows the rigging angles will be sufficient. ;-)

The 'functional answer' is: 1. how much SAG to leeward is occurring in the forestay when the jib/genoa is windloaded and does that wire sag 'match' the shape of the leading edge of the jib. If you ignore this, then you can wind up with a boat that aggressively heels over, cant 'point' .... very cranky boat. 2. that the forestay/backstay combo doesnt go much above 30% tension under/during max. sailing conditions - a 'fatigue' of the wire consideration.
The reason for all this that wire stretches with varying loads applied by the sails AND the sailmaker probably cut the shape of your jib/genoa EXPECTING that the forestay has ~15% 'basic' (at the dock) wire tension for when sailing in 15kts. of wind - an EXPECTED / predictable sag in the forestay wire when the jib/genoa is windloaded. !!!!!!!
Here's how to adjust the backstay for 'dynamic' or sailing conditions if you desire 'decent' upwind sailing performance:
http://www.ftp.tognews.com/GoogleFiles/Matching Luff Hollow.pdf

 

[Bob S]

Thanks RichH, unfortunately my mast is in storage. I hope to get it down next week. I will post it then.

 

[RichH]

Thanks RichH, unfortunately my mast is in storage. I hope to get it down next week. I will post it then.

For simplicity in your reply ....
1. how far apart are the two chainplates on the stern and
2. how 'high' along the backstay system is the 'connection' to the split backstay stays .... or how long is the length of one of the 'split' backstays.

 

[Bob S]

Rich,

I went out to the boat to measure when I realized the mast wasn't up! I did measure the distance at the chain plates @ 68" but until I get my mast down I don't know the leg length or i would have figured out the angle and given it to you. I'm missing that one piece of info.
BTW, thanks for all your great responses. There's a never ending learning curve that is quite daunting when first starting out. I'm the type that has to be hit in the head a few times before it sets in. I don't want to roatly know it, but much rather understand it.

 

[ifmdalvey]

c-witch
The lbs torque you are quoting sounds extreme to me, my Island Packet is in the region of 15 -35 lbs torque depending upon which part of the rig is being tuned. I would check the numbers before torquing any where near your figures.

 

[c_witch]

c-witch
The lbs torque you are quoting sounds extreme to me, my Island Packet is in the region of 15 -35 lbs torque depending upon which part of the rig is being tuned. I would check the numbers before torquing any where near your figures.

Hiee,

We are going with information in the little guide book that came with the Loo's tension gauge model PT-1. For 1/8'' wire its says to use 320 lbs on the forestay and 220 lbs on the shrouds. Working backwards then about 245 lbs on the aft stay. My main concern was in having the boat level in order to get the desired rake to the mast. We have NO specs on the rigging for this boat and there appears to be NO information on the Net about it either.

c_witch

 

[anchorclanker]

My 222 says hand tight. I was thinking about how the guys decades ago would have done it. They only needs be tight enough to not allow mast movement, correct? I know you wouldnt want any slack, that could allow extreme forces on takeup/slop. But extra tension beyond that would only contribute to forcing the mast downward, while applying opposite loads to the chain plates.

Couldnt you just thump them like a guitar??

 

[justsomeguy]

My 222 says hand tight. I was thinking about how the guys decades ago would have done it. They only needs be tight enough to not allow mast movement, correct? I know you wouldnt want any slack, that could allow extreme forces on takeup/slop. But extra tension beyond that would only contribute to forcing the mast downward, while applying opposite loads to the chain plates.

Couldnt you just thump them like a guitar??

Blasphemer! You've gotta spend the requisite $$ for absolute certainty!

 

[cephius (Dave)]

Tension in lbs

ifmdalvey,
The document in this link was based on information received from Hunter. http://www.h260.com/rigging/rigging.html It shows values of 365 lbs and 560 lbs. It indicates that these are 26 and 37 on the PT-1 Loos Gauge. I use these values when tuning my rig and they stay well within the thread range of the turnbuckles. 37 is about 2/3 up on the scale range for my size wire on the gauge. I think c_witch can use those numbers safely.

anchorclanker,
I tried for years to set my rig without a gauge. When I finally got one I found I was only 1/2 the tension recommended. I'm glad I got a Loos Gauge.

 

[Bob S]

RichH,

Got the mast down. The backstay is 1/4 and 3/16 at the split 10'10" long and 68" apart. How would you calculate the #'s for each split using a loos gage?

Thanks for your effort.

 

[Douglast]

Abit of variance on adjusting it seems...well can someone tell me if im on the right track..??
...i have the loo's guage pt1...the guage comes with what seem a pretty good guideline to follow...my manual says to adjust forestay first..(my backstay has several holes with pin to set on back mount )..then upper shrouds...then lower shrouds a tad less tension then the uppers and then fine tune when tacking etc.

So far preliminary things look good..(Loo;s does say better to be on the more tension side of things then less..)....1/8 cable


lbs
forestay 340 ...backstay 220 .upper shrouds 240..lower shrouds 220..( Loo;s indicate if the speaders swing aft that uppers can possibly need higher tension..up to 25 percent of breaking strength..??)

Any way i seem to be in the ball park i think..??..one real question though..

Its a fractional rig..my mast groove is nice and straight all the way up..BUT the mast has a very very very slight rake to the aft (barely noticable) from about the top of the mast to approx 5/6 feet down..Is this a problem..i thought somewhere i read it was often sought after..??..willikers..the first post...hahaha

Anyway any replies on if im close...( i have just been guessing for the past 5 years..haha.) it would be much appreciated...and if the slight rake seems ok it would be nice to know..

Thanx Doug

 

[Douglast]

ttt...^^^....