Goode Fin Length Measurements

[brettmainer]

I understand the fin length measurements posted on the Goode website are measured with jaws on Goode calipers. Is there a known correction factor when using standard caliper tips? I seem to remember something like .13”

[skialex]

There is no standard conversion. This is why I carry 2 calipers, one Mitutoyo and one Goode.

When measuring tips the shape and size of the caliper and the shape of the ski play little role. But when measuring jaws and as the caliper sits deep between the fin and the bottom of the ski, caliper and ski size/design play some role and results may vary.

So you either buy a Goode caliper or ask someone to measure your fin’s length with his and then measure with yours using tips and that will be your conversion.

What ski are you on? If by chance I have the same model/size, I can do the conversion for you.

Alex,

[brettmainer]

@skialex, XTRcc

I guess the answer might be slightly ski dependent, but since the tips of a Goode caliper should be the same as any other caliper, there should be a fairly standard conversion obtainable by comparing length measurements with tips and jaws of a Goode caliper.

[skialex]

@brettmainer Goode measures length with second gen slot caliper using jaws. So that measurement is highly dependable on caliper and ski model and you can not make a universal conversion to an 8” standard caliper tip measurement. So I can tell you for example that my skis length is 6.815” Goode caliper Jaws and what my mitutoyo says when measured with tips. Ski is a 68” Xtr cc, I have a CG fin but at 6.815” it would not made a difference if I had a standard fin. I’m posting numbers as soon as I get back home.

[klindy]

ANYtime you use the non-machined surface of a precision instrument you’ll get varying results. The “jaws” on any caliper are not made to any tolerance, they are not measured or QC’d to any standard and they are NOT meant to be used to measure anything. I get that it may be “helpful” to lay the caliper ‘flat’ on the ski and tight against the ‘jaws’ but you should ONLY compare measurements using the SAME tool between skis or between measurements on the same ski. The results *might* be the same but it’s not the intention. I’m sure any machinist or engineer cringes whenever this topic comes up.

 

All that said, since we’re measuring an odd shaped part using a common tool, trade offs are made. But if you think you’ll get truly accurate measurements using the tools in a way they aren’t designed AND get comparable results with someone else’s measurements, you’ve been drinking too much IPA.

[skialex]

@brettmainer

 

[skialex]

@klindy you are right but what can you do when stock numbers are measured with jaws? I laugh every time a friend gets a new slot caliper and we compare it the bunch of slot calipers we have and numbers are all over...

[brettmainer]

@skialex, thank you. .087” for XTRcc. Insightful to mention that number will change depending on ski model due to variations in tunnel depth at fin.

 

@klindy, I completely agree with the first paragraph in your post above and completely disagree with the second. Calipers are designed and calibrated to be used with the tips. Goode website posts fin lengths measured differently than other manufacturers using the non calibrated part of their proprietary caliper. How else is one to convert to a tips measurement that can be replicated with any standard caliper?

[Horton]

When ever I get a Goode I call around for someone who will give me the stock fin length with tips.

[klindy]

@brettmainer understood. I love Goode Skis and have both a slalom and (now) a trick ski made by Goode. However it does make me laugh every time a company that prides itself on precision and technology thinks using a non calibrated part of a high precision tool is acceptable.

 

If you really want to know the difference between the jaws vs tips measurements OF YOUR TOOL, I'd get a small (3/16" or 1/4") piece of keyway stock and measure it with BOTH the jaws and the tips. Make sure it's sitting squarely on both sections of the caliper. Then the difference between the two measurements is what you would add or substract from the alternative dimension (jaws vs tips). It won't be a perfect comparison to someone else's caliper but it's probably a good starting point.

[skialex]

The second gen slot caliper uses machined jaws supposedly grinded with precision. So jaws of the second gen are not a non machined surface as in any other caliper.

[DW]

It would be great to eliminate the lack of a consistent methodology to measure fin dimensions. @klindy is correct on caliper use. The use of calipers for fin measuring should be done to proper tool measurement standards if comparing and publishing data is needed. For your own records, if you find something that works and is easy, great.

Even if the calipers are a fully ground and a zero capable surface, there is no reference to distance off surface to provide an accurate datum so a high error rate is probable. Comparable example would be measuring an automotive camshaft, total duration is difficult to measure so the measurement standard is duration at .050" lift (hence universally known).

Certainly lack of consistency is understandable given line length is measured in opposite fashion whether metric or imperial. At least not in increments of furlongs:-)

[klindy]

@DW we can start measuring lake depth in fathoms......

[klindy]

 

 

 

 

What we're calling "jaws" is actually the "root" which is not a machined surface with a known tolerance. The "jaws" and "jaw tip" (see above diagram) are in fact ground and should be accurate.

 

Again, I totally get we're measuring an odd shaped multi-dimensional part (fin on the bottom surface of the ski) but do not expect different calipers to give you the same measurements if you use the "root" of the jaw.

[The_MS]

Knowing the fin movements effect on the skis performance and correcting it to help it is more important then the caliper itself. Get it close to stock and take it from there to where it helps it’s performance with your skiing style

[skialex]

@klindy you obviously know what you are talking about. The root jaws are not meant to be used for accurate measuring. The caliper pictured is an absolute precision measuring device. The Mitutoyo coolant proof. I have one actually I have few Mitutoyo calipers. And yes the root jaws are not meant for measuring. The second gen slot caliper has been grinded specifically to be able to measure at the jaws root and also have a slot cut to help with dft measurement. These modifications change a $20 caliper to a $150 one. As long as Goode posts numbers taken with a slot caliper, you need one at least to put the fin close to a starting point.

Funny that couple of years ago they changed the brand and the new ones do not produce the same numbers as the older ones but the numbers on the their fin chart haven’t changed. The display is of different size and maybe this is causing the problem, the way it sits when measuring with jaws.

Anyway, this is why I carry 2 calipers in my tool bag.

[klindy]

@skialex I agree with you. Again it’s the comparisons between tools that becomes the issue. When In the world of precision engineering, different people should be able to repeat the same measurements with different tools. If you “have to hold your head just right” to get the dimension your after, it’ll never be repeatable and, by definition, never be shareable.

[DaveD]

I'm so glad I'm not a good enough skier to be affected by fin measurement error or octane levels. :smile:

[skierjp]

FYI, 2 good videos on YouTube with Chris Rossi giving step by step instructions on how to measure your fin and set your bindings.

[BraceMaker]

 

[BraceMaker]

About the best you can do is test it yourself. The older goode ski manuals listed measurements with a slot vs standard caliper which looks to be .066 on length.

[skialex]

This is so old... the slot caliper was the first gen without the grinded Jaws all the way to root. Also numbers with the dial caliper were jaws too...

Go figure... if you look at the new charts but the old models and try to compare the above numbers with the ones on the new charts, you are getting a headache.

I use the new charts for skis after the N1.

[ForrestGump]

@brettmainer Chad Scott gave me 6.830, 2.495 depth, and .700 dft. With a regular caliper using tips. I specifically asked about whether it was a slot and he said No.

[The_MS]

For my 67 XTR cc.

6.840 tips

2.498 deep

.708 DFT

 

[jimbrake]

@The_MS - are those stock for the XTRcc or your personal numbers you've settled on? I've got a 68 XTRcc coming next week. Thanks for posting as I too will be using caliper tips.

[The_MS]

Those are the numbers that I settled on with my dial caliper. I found that the DFT adjustments are the most critical

[jimbrake]

@The_MS thanks. Do you have your front binding at stock or back? When I tried the XTR at stock it was good. Went back a bit and it got heavier/slower but still pretty good.

[BraceMaker]

@skialex not saying it isn’t. I agree with the absurdity of using a low quality instrument to measure a high degree of accuracy. I get the idea of,a slot caliper but only if every slot caliper is carefully calibrated to a standard and they are not.

[Drago]

*cough*

All Goodes should be set at exactly:

1 thumb dft

3 fingers deep (at 2nd knuckle)

and the length of your Allen wrench

Got these numbers from a pro and ran my pb 1st set in a drysuit and haven't looked back

[The_MS]

@jimbrake I am about 2 slots on my Mikrojust forward of stock so basically stock