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Does anyone know how to properly tune-up an MK V standing rig? I need to know the tension on the shrouds/back stay/forestay?
What's the best method of doing this and what kind of tools are needed?
Thanks in advance.
Guillermo
Check the Sea Change - MK V section of this site for the tuning guide.
You sould have a rig tensioning guage to make sure the tension is equal port & starboard. (if I had one I would tell you our settings, but I don't have one! Maybe Santa wil help!)
We tune pretty much as per the guide - medium tension on the uppers & lowers, about 6" of rake, and about 4" of bend in the mast with the back stay tensioner right off. We use plenty of back stay tension when racing in anything over 8 - 10 knots, unless it is wavy without wind.
Jim W
Distant Thunder Hull #69
This question doesn't have a simple answer. There seems to be two "camps" about shroud tension -- one says the leeward shrouds should never have any slack and the other says slack is OK when hard on the wind. I tend to favour the "no slack" side (to elimate shock loads on the rig when the boat bounces), but C&C warns in the tuning guide that the MkV slender mast shouldn't be under too much compression. I agree with Jim that you really need a LOOS gauge or other objective way of measuring tension to do this right. I tend to use 900-1000 lbs on each of the main 7/32" wire shrouds and a lot less on the thinner (3/16"?) mid shrouds. You need to balance the port and starboard sides so the mast stays straight and centered. The tension difference between the main upper and lower shrouds controls the mast pre-bend. The optimum amount of pre-bend depends on the cut of your mainsail. Mast rake is another issue. The C&C tuning guide talks about 15" of rake <IMG src="http://www.cc27association.com/f3/toast/emoticons/icon_exclaim.gif"> but I think that applies when sailing with 6 beefy guys on the rail. I have sailed a season with 12" of rake and another season with 6" of rake. With 12" rake the light air performance was better, but I had too much weather helm in heavy air. (I usually sail single handed and race with only one crew.) With 6" of rake the boat was better behaved in heavy air but light air performance seemed to suffer. Also, there was just a touch of lee helm in light air. I tallked to a guy named Collin Andrews who sailed on the prototype MkV and he said the boat initially had lee helm. That may be why C&C recommends what seems like excessive mast rake.
when going upwind my leeward shrouds are loose.
Re: rake - The boat has a neutral helm - so more rake is good. In heavy air the key thing is to play the main sheet traveller, and ease it when overpoered in the puffs- if you do that constantly you'll have no problem with wether helm.
Thanks for the responses. Now, how do I measure mast rake? and how do I adjust it?
Guillermo
to measure mast rake rig the boat, then hang something heavy from your main halyard - say, a hammer - so that the helyard hangs vertically. Measure the distance from the back of the mast at the deck to the halyard - that's your rake. To add rake, loosen the forestay, tighten the backstay.
Jim
Hi Jim,
Thanks for your response. Now I understand how to measure the rake. The question is how much that distance should be in order to have a 6 degree rake?
Thanks Guillermo
From what I remember about trigonometry:
Opposite = x
adjacent = 989.89 cm (mast lenght)
Angle/rake = 6 degrees
If my calculation is correct...
tan( 6 ) = opposite/adjacent
opposite = tan( 6 ) x adjacent
x = tan( 6 ) x 989.89cm
x = 0.10510424 x 989.89
x = 104.04 cm
Am I doing this correctly... It seams like 104.04 cm is quite a lot.
Guillermo
6" of rake is just having the tip of the mast leaning 6" backwards from straight up. If you measure from the base of the mast to where the halyard hangs - that's your rake. 6" of space between the halyard & the mast = 6" rake.
oh you see, I had it all wrong... When I read 6 to 18 on the tuning guide... I thought it was "degrees" not inches!... 6" is short of 1 degree angle on the mast... which makes perfect sense.
Thanks
Guillermo
For those of you that would like to know what I ended up doing:
First a bit of background:
"Compos Mentis" is 1986 MKV. She has a Quantum Main sail brand new which has to full battens and two partial battens. Before this adjustment under load the leeward shrouds were very loose.... so loose that I could have taken them out of the chain plate if I wanted to. The forestay had a lot of sag and gave me some trouble pointing high... All her standing rigging uses 7/32 wire.
So... This is what I did:
- I measured all the previous tensions with the LOOS gauge and wrote the down the setting (just in case I need to revert). I noticed that lower and cap shroud were around the 26 mark on the gauge for a 7/32 wire. The forestay was so loose that did not registered anything on the gauge (with no backstay tension).
- I started with the cap shrouds first and center the mast on the boat.
- I measure the mast rake and I had lots of it! Over a 20 inches of rake was measured... so I adjusted the forestay to bring that rake back to about 8 inches. Tip: I'm about 220lb and I noticed that letting my wife measuring the rake (she is about 100lb), it was way more accurate... since I will bounce the boat around making the task more difficult.
-I setup the tension of the cap shrouds to about 32 on the LOOS gauge, which I think it was about 750lb if I remember well. This setting was about 12% to 15% of the wire's braking point. I didn't want to set it up to tight... my reason is that there is always time to tight a bit more and too late after is broken <img src="emoticons/icon_smile.gif">
- I continued setting the lower shrouds to the about the same tension of the cap shrouds (since it was originally setup this way). I had to look at the mast from many times trying the get the middle portion of the mast straight. It worked out pretty good. I was able to setup all the shrouds about 32 on the gauge and have the mast straight... which I checked many times <img src="emoticons/icon_smile.gif">
- After this I was ready to setup the minimum backstay tension mark which I setup at about 12% of the braking point. Then I setup the maximum mark to 40% of the braking point.
- I was ready to go sailing now... so I went sailing in a 20-25 knots wind and flat water to see how the she handle the new settings. She was very responsive and easy to handle. One thing I immediately notice is my ability to point higher now. I was able to get a finer entry on my fore sail. The mast was straight under load as well, so no adjustments were needed. The leeward cap shrouds had no slack under load, but the lower shrouds have a bit of slack. I left it like that for now since before I had lots of slack in both and didn't seam to be a problem. I might change the settings later based on what other people have to say here.
That was the end of the process... it is time consuming, but fairly easy to do.
I didn't have time to try the boat in light air... but I'm sure I will find one of those "rare" days very soon <img src="emoticons/icon_smile.gif">
Thanks,
Guillermo
Hi All and Happy New Year.
For those who've been following this rig tuning discussion and who, like me, are not able to leave your mast up all year, here's a quick tip. Once you've gone through all the steps to get that mast vertical, in proper alignment and with the appropriate amount of rake etc., don't lose all that tweaking and twiddling when you pull down the mast. Just before loosening those turnbuckles, make a couple of turns of electrical tape around the turnbuckle threads, right at the outside edge of each turnbuckle barrel. When you put the mast back up, simple tighten each turnbuckle back to within a half turn or so of last season's stored settings (tape) and you're ready to sail again with minimal need for re-tuning everything !!
Clare Jordan Aragorn
<U>SAIL FOR SALE </U>_
#2 Genoa for 27' Mk.111 by North Sails . Tri-radial cut, Norlam fabric, built 1998-- good shape . Window, tell-tales and draught stripe. Stitching etc. checked ;2001/2002 . #6 Luff tape .
Replacement Genoa is on order for 2004 racing season but there's some cruising years left in this one -$ 550 asking price. phone 613 498-2029 or e-mail <A href="mailto:bosco@ripnet.com">bosco@ripnet.com</A> <img src="emoticons/icon_frown.gif">Brockville)
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Hi
First I know this is a 4 year old thread but when I did a search this is the only one that came up.
Has anything changed in the last 4 years to change the so called preferd setting for the rig. This is my first year stepping the mast and I want to do it right. The mast was up for me last year when the boat became mine and I made the mistake of not checking anything before taking it down last fall.
I had to take the furling apart over the winter due to the top part of the track being damaged so I had a new forstay cable made. The mast rake is my big concern.
3 questions--- is there a setting for backstay using the loos gauge??? can I reduce or increase the rake at the base of the furling without undoing it from the deck??? what are others using for rake with 3 average weight guys and are you measuring it at the top of the boom or at the deck????
Thanks all and sorry for reviving a old thread
Jim
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Rake: I'm using about 15". Measured by hanging a wrench from the main halyard and measuring from the back of the mast to the halyard at boom height. Make sure the boat is sitting level in the water - move stuff down below if necessary. Measure with no backstay tension.
Upper shrouds: we are at 30 on the loos guage.
Lower shrouds - we are at 25 - 32 is too much - you want a bit of sag in the middle of the mast to give the main shape in lighter wind.
Prebend - the mast should have about 4" of bend in it after the shrouds are set - that's with no backstay tension.
Jim W
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Rake: I'm using about 15". Measured by hanging a wrench from the main halyard and measuring from the back of the mast to the halyard at boom height. Make sure the boat is sitting level in the water - move stuff down below if necessary. Measure with no backstay tension.
Upper shrouds: we are at 30 on the loos guage.
Lower shrouds - we are at 25 - 32 is too much - you want a bit of sag in the middle of the mast to give the main shape in lighter wind.
Prebend - the mast should have about 4" of bend in it after the shrouds are set - that's with no backstay tension.
Jim W
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I am adding this question to the standing rigging thread because I could not find another appropriate entry.
For the Mark V, in our first season, we were never confident as to the correct setting for our adjustable topping lift. We have a loose-footed main whose shape always looks great-so we normally put no tension on the topping lift and let the boom settle at the height and angle determined by raising the main to its full height.
Sometimes, through carelessness, the topping lift was tensioned, but we quickly released it.
So, we have this nagging thought-in light air (how light) should we tension it to bag the foot of our loose-footer even more?
any hints appreciated.
copasetic
after 3 races, it is clear that we are slower than last year. last fall, we ( do-it-yourself) unstepped the mast and restepped this spring without being careful to exactly duplicate what another yard had set up last year when they turned the boat over to us from the previous owner.
we have the uppers at 30 (LOOS) lowers at 25. Nobody has mentioned what the baby stay should be-any suggestions?
we have not yet installed the backstay adjuster, so what is an average tension for the back stay-rarely more breeze than 10-12, often less. Fore stay is a roller furler.
different from last year, our main often catchs up on the back stay (or the topping lift)
thanks in advancecopasetic
Copasetic:
First of all, since you didn't have the ability to get yourself back to where you left off last year with respect to mast tuen, you kind of have to start over again. the first thing you must do is make certain that the mast head is in the middle of the boat (awthart ship- side to side) you can do that by using a 50' tape measure and with the main haylard hoist the end of the tape measure up to the top of the mast (I use a spare sail slide so that I know I'm measurig from the exact centre of the mast (the main haylad sheeve is not in the centre at the top) then measure to a known point (I use the deck imediately outboard of the chain plates at the toe rail) on each side. Adjust the upper (cap shrouds) so that the mast is centred, (the tension at this point is irelevant). Now you are set to tension the rig, by adjusting each side the same number of turns on the trunbuckles load up the uppers (if you are using a LOOSE gauge you want to get to around 30 - 32), next you can tension the lowers to pull the mast into column, the lowers will likely be a little looser than the uppers (LOOSE gauge around 25 - 2<img src="emoticons/icon_cool.gif">. Now your mast should be centred and have the proper amount of prebend (described above by JimW) now set your mast rake as per Jim'sdiscription, remember make sure the boat is level fore and aft, hint check the waterline and adjust stuff down below to get it level.
I don't use the baby stay, unless it's lumpy, and then we only hand tighten it. The baby stay on the Mark V is there to stop the mast from pumping and is not designed to be loaded up. If you tension the baby stay too much you will only create more trouble for yourself and end up with a leak at the deck where the chain plate is. If you look at how the baby stay chain plate is installed in the boat it is only supported by the bolts attaching it to the forward bulkhead, it's not intended to sustain a lot of load.
If you are racing the boat and don't have a back stay adjuster, get one, you are just not going to get the preformance of the the Mark V without being able to tension the backstay to minimumize forestay sag.
May sound like a long way of saying you need to retune the boat , but the Mark V is very sensitive to rig set up and once you get your boat tuned record the settings, mark stuff in the fall before you take it appart. One word of caution, when using LOOSE gauges there are 2 styles, for wire rigging, the standard gauge and the professional (the standard is what most people have, the professional is designed for one handed tuning and stays put on the wire while adjusting) the two gauges give different readings so what is 30 on one is not 30 on the other.
If your main is hanging up on the backstay while tacking try using a little more vang tension, you can also spray the leech of the sail with "sail kote"
Steve
Still Knot Working MkV #75
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