Lately we're getting bit by bit to a higher level on our Nacra Inter 18. We've been advised during training by very good sailors on several settings to increase the boats performance, and therefore got a bit deeper into this topic. For that reason we are thinking of buying a Loos gauge to measure tension in the stays.

However after reading some forum discussions via the search function, made me doubt a bit. E.g.
1) I see several disccussions going on where people are looking for the right tension settings. If these are not available what is the value of the gauge?
2) I see some discussions going on about the accuracy of such a gauge.
3) There not very cheap, and therefore it realy should contribute

Could anybody explain me if we would benefit from such a gauge? What can it bring us?

I would absolutely get a loos gauge. We use ours in a couple ways.

1. To set our tuning marks for diamond tension. We use marks on the mast and diamond wires to keep track of things on the water, but the gauge is important to make sure everything is calibrated.

2. To check tension on sidestays. We don't have sta-masters so this is a rather gross setting, but we like to make sure we are in the correct range.

I use one, and I think its a benefit. On my boat i set the diamonds to a guess of what the conditions might be. I think that it makes a big difference on my boat.

I also question the accuracy of the loose gauge, however i think what is most important is that it reads the same every time. I think that you should look at the tuning guide for a guideline but come up with your own numbers overtime. With that in mind I think it's important to use one gauge on your boat and not use multiple ones. Find out what works for you and take notes, The gauge will help you repeat the same settings when you want to.

I use the Harken rigtune. several friends have put their loos gauges on my boat to compare and seen similar tension numbers. However one guy put his device on my boat and it read several hundred pounds differently, if I had used his gauge one time for my settings, it would have been far different from what I was expecting.

If nothing else, it will allow you to set the boat up the same way each time. Over time, you will get a series of settings for your boat/weight/sails that match the weather conditions. This tool will ensure that you tune the boat to the same setting each time out (even if they are different from the generic "tuning specs").

Agree fully with the comments above. The primary value will be consistency in your settings, and a consistent starting point for further adjustments.

If you have good friends or events where people are willing to share info to ultimately make everyone faster, use your gauge to measure other boats, discuss settings and changes with more experienced sailors, etc.

Hope this helps.

Mike

I have been using one for years...

Regarding the setting of the diamond wires.... I got recommended benchmarks from the person that made my mainsail... They gave me a few settings depending on the conditions. I just took the middle setting and went from there...

As for them being accurate, all I can say is that I saw a Loos gauge in a aircraft mechanics tool box that he used for light aircraft rigging. I would say they are pretty much "close enough for government work." Note, this is all they do; that is build tools for cable/wire rope industry. I think they have it figured out.

You don't have to buy one... I always lend mine out to fellow sailors and collaborate on settings etc...

Also, if I could recommend, you may want to upgrade your diamond wires... The Inter 18 and Nacra F-18 used 1/8" here in the US and the recommended tensions/setting from my sail maker was pushing the limits of the cable... Loos recommended tension at no more than 25% of rated breaking strength. I upgraded mine to a 5/32 and was able to "honk it down" with plenty of room before it maxed out..

Here is some info from their website...

http://loosnaples.com/how-to-use-pt-series-tension-gauges

Thank you all for your input, as always it is helpfull again.

Hi ventucky red, thanks for your input on wire size. I have no clue which size it is on our boat?? But looking at the available sizes on the gauges, does anybody think the wire could be thicker than 4 mm? (5/32)

Your link doesn't seem to work?

If we go for it, we would go for this tool:



I think this one is ok?

And a little afraid to ask, but: would anyone have any settings for the Inter 18?

I would say a good starting point would to add tension until you get about an inch of pre-bend in the mast...

This should help you out

http://www.working-the-sails.com/masts_and_booms.html

These links above are for general, mono masts, Scows are pictured in the background.

Does your cat have an actual 'backstay'? Not the shrouds, or mainsheet- an actual backstay?

The intent was to show him how to measure the pre-bend for his mast.

Is that any different?

Bought one last week, and measured our settings last sunday when we went sailing (a bit cold though, with 0C)

38 on the gauge for the diamant (3mm) and 29 on the side stay (4mm)I do not have the table present at the moment, but I think to remember 320 kg on the stays and the diamant is out of reach of the table. Does anybody know if that is too much for moderate air?

Various Loos gauges have different scales for their numbers. It is useful to use the scale on the gauge to convert those into Kg or Lbs for the sake of discussion.

Hi Jake, yes I know, however if the conversion is not possible because the tension in the diamant is that high that the delivered table is not covering that area, than this is a bit difficult

Tried to find a tuning guide for the Inter 18. Searched the internet, asked fellow sailors, and even asked Nacra in Holland. It seems that nobody has one anymore. So if anybody knows where to find one, at this moment or in the future, it would be highly appreciated!!

Arjan,
in case you bought the loos gauge pictured/posted above, 38 is the medium setting for nacra F18. Max is 42. The prebend of your mast must be inline with the cut of your mainsail (luffcurve matches prebend). If you crank the stays hard, the mast gets stiffer in the lower section and the top is more flexble and vice versa. Andrew Landenberger has some tuning tips for A-cat on his homepage. I found it very helpful to better understand the physics behind. Most People overestimate influence of stay's tension compared to correct use of mast-rotation and cunningham.

Good point.

With today's sail materials (with little or no stretch), how much would changes to rig settings benefit the sail shape?

I was talking to Lin (North Sails) about the 3-Dl/3-Di moulded sailshape and what, if any, changes to pre-bend or even downhaul might have (other than to attain proper sail shape initially). I mean, if you crank a 16:1 downhaul, how does it flatten the sail if there's no flex/stretch in the material? Does it just bend the mast?

Bending the mast is exactly what a modern cat downhaul does, look at some of the A-class sails and you'll see a heap of fibre running up the luff.

So if you don't have a mast with a whole lot of flex (think the old N20 mast), and you're using modern non-stretch material on the main, you're pretty much not going to change the shape much with your sail controls (downhaul, outhaul)?

The I20 mast was capable of some pretty incredible bending...particularly at the top. I remember stepping back on one for the first time in a while after sailing F18 regularly...I couldn't stand to look up at the top of the I20 rig because the amount of bend bothered me so much.

Stay off the F16 Jake. It's capable of some very scary flexing.