Loos gauges accuracy at low end

[yelkenli]

This youtube claims that PT Loos gauges are not accurate at the lower end of the scale. true false? I want published accuracy if I am paying (no worries if I borrow ). The PT has the added benefit of leaving it on the wire while you adjust.

I will be measuring on a 3/16, which is the lower end of a Model PT - 2.

Thoughts? Experience?

Thanks!

 

[dLj]

I don't know the answer to your question. But typically gauges of this nature have a % of inaccuracy that is just always there. they also typically have greater deviations at both the low and the high end of the scale they are rated for.

Also, don't confuse accuracy with precision. Each individual gauge is probably pretty precise while their accuracy may not be. You don't really need accuracy if you are buying a gauge and are using just that gauge - you need precision. Do you understand what I'm saying here?

dj

 

[dlochner]

I've been using Loos gauges for decades including a "professional model." The Pro model is a little easier to use and read than the other less expensive models mostly because it can stay on the wire as it is adjusted.

In general, if you are tensioning the wire at the lower end of the scale, the shroud is almost certainly way too loose, likewise if tensioning at the upper end of the gauge, the shroud is way too tight. Most of the gauge readings will in the middle of the range.

In my non-engineer way of thinking, the gauge's precision is not very high, however the readings are very repeatable. In other words, if the guage indicates 1,000 lbs of tension, it might have a measurement error of +/- 100 lbs. This is simply a function of the gauges construction. It is sort of like measuring something with a ruler that only has inch markings. If the thing being measured is more than 1 inch long and shorter than 2 you have to estimate whether it is 1 ¼ or 1 ⅓" long. So it is a rough measurement of wire tension.

On the other hand, the gauge allows for accurate repeatable measurement. If the gauge says it has 1,000 lbs of tension on the wire today and tomorrow it reads the same, then we can be fairly confident the tension is the same, although it might not be exactly 1000 lbs.

I use the gauges to make certain the shrouds are evenly tensioned at about the tension I want them to be (around 10-12% of breaking strength). It works well for this purpose and it works well for checking the tension later on, if I remember to write down the starting tension. It is much more precise and accurate than my not so well calibrated thumb. The gauge readings also give me an idea of how much tension to add as I tune the rig, it helps to answer the questions, "how many half turns should I add on the turnbuckle, before switching sides?"

Is this as accurate or precise as a load cell on the shroud? Nope and its not intended to be.

 

[dLj]

I've been using Loos gauges for decades including a "professional model." The Pro model is a little easier to use and read than the other less expensive models mostly because it can stay on the wire as it is adjusted.

In general, if you are tensioning the wire at the lower end of the scale, the shroud is almost certainly way too loose, likewise if tensioning at the upper end of the gauge, the shroud is way too tight. Most of the gauge readings will in the middle of the range.

In my non-engineer way of thinking, the gauge's precision is not very high, however the readings are very repeatable. In other words, if the guage indicates 1,000 lbs of tension, it might have a measurement error of +/- 100 lbs. This is simply a function of the gauges construction. It is sort of like measuring something with a ruler that only has inch markings. If the thing being measured is more than 1 inch long and shorter than 2 you have to estimate whether it is 1 ¼ or 1 ⅓" long. So it is a rough measurement of wire tension.

On the other hand, the gauge allows for accurate repeatable measurement. If the gauge says it has 1,000 lbs of tension on the wire today and tomorrow it reads the same, then we can be fairly confident the tension is the same, although it might not be exactly 1000 lbs.

I use the gauges to make certain the shrouds are evenly tensioned at about the tension I want them to be (around 10-12% of breaking strength). It works well for this purpose and it works well for checking the tension later on, if I remember to write down the starting tension. It is much more precise and accurate than my not so well calibrated thumb. The gauge readings also give me an idea of how much tension to add as I tune the rig, it helps to answer the questions, "how many half turns should I add on the turnbuckle, before switching sides?"

Is this as accurate or precise as a load cell on the shroud? Nope and its not intended to be.

Your description is actually backwards - in terms of terminology. Precision is repeatability - accuracy is how close to the right number it gives you. That is exactly what I was saying above. Let me attach a photo - this shows it very well.



These gauges likely have fairly high precision but low accuracy.... Although, just guessing really...

dj

 

[shemandr]

I have only used the first model - I think because there wasn't a choice.
I Agree with the above posts. It's not an instrument. It gives a reasonably repeatable reading - if you can use it consistently. For example, you should measure at the same height on each side of the boat and thereafter when re-checking. The deflection two feet above the turnbuckle would be less than five feet from the turnbuckle. The gage is useful for comparisons but not for absolute numbers
Ditto with the variations for top and lower wire sizes.

 

[Dalliance]

How precise do you really need to be? It will aid in getting tension equal from shroud to shroud and give you a good idea of tension load. It’s a big step up from just going by feel. I wouldn’t worry about the claim of inaccuracy in one YouTube video.