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DFT- Am I stupid?


Hipsup
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I've just acquired a new 68" D3 fusion (very happy with it!) and for the first time ever after more than 10 years skiing I decided to measure my fin.

After getting some callipers, the first thing that surprised me was that the fin, as supplied, measured nowhere near the stock settings published by D3. Measuring the length and depth was pretty simple, but the DFT is a joke. I could measure this 100 times and get a different reading every time. How are you supposed to hold the calliper against a short, angled surface and then measure the distance to the bevelled rear edge of the ski with any degree of consistency? I've got the same problem whether I do it flat from tail or needle to tail and according to D3 there should be a 0.04" difference between the flat and needle measurement - not when I do it there isn't!

Am I doing something wrong and does anyone have a fool proof method? Also D3 have white reference lines drawn on the fin itself - why don't they also put reference lines on the bottom of the ski so that you just have to line everything up to know that the fin is in its stock position without getting callipers out??

I'm starting to wish I didn't decide to measure it now - ignorance is bliss!!

 

 

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Hipsup, I also recently bought a d3 fusion about a month ago. I have been skiing the heck out of it, almost every day, & I'm having loads of fun. (free skiing so far). I really like the nice etchings on the fin, I figure you almost don't need to measure to know pretty much exactly were the fin is. Maybe I am naive about that though. I only know some basic things about fin placement, but I have moved the leading edge down a bit, to help keep my tip down, and I moved the fin back a bit to make the ski feel a bit larger. I am 6.3, & 198. How bout you? Also, is the main horizontal line exactly 2.5 inches? Can some experts please chine in? Thank you.
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  • Baller
Can't wait for the hundreds of explanations you will get back. First will be that you need to buy slot calipers. And no you are not stupid. Try to use it as a ref. point. Find a method that is somewhat repeatable for you. Use the same method each time when you adjust. Make adjustments relative to your method of checking. Using someones number for distance from tail my not translate to your checking method. Make your movements relative from a repeatable know location and don't put to much into a solid number.
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  • Baller

Before you change the fin, make a scribe line on the fin at the settings you like. Put a scribe line on the ski for reference as well. It is critical to get reasonably close to a baseline if you have made some large adjustments - or bonked the fin out of position (which happens a lot!).

 

I cannot make any fin measurements with calipers that repeat within .001. Using my eye against the scribe lines gives me accuracy adequate for my skiing. My skis are perhaps more variable than factory skis so calipers may be less reliable for me. I have had good luck with an engineer's scale in place of calipers for getting numbers but still use the lines on my ski and fin for placement.

 

Find a measurement technique that works for you. One that is repeatable and consistent for your tools and measurement skills. Accept that others may get different numbers (if you can get some guru to measure your fin you might be able to see if your numbers match). And scribe your fin and ski so at least you can place your fin!

 

Eric

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  • Baller

Crap -- somebody needs to hound me to take some pictures of a method I discovered a couple of years ago for getting extremely accurate DFT measurements with an ordinary caliper.

 

The key to it is that there are two measurements you can take very accurately-and-repeatable and the difference between them is the DFT. I've found it's repeatable to about 0.002".

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http://www.ballofspray.com/2011-ski-tests/2011-ski-tests/61-digital-slot-caliper-2

 

I know I have written about this in the past. For now just get a slot caliper

 Goode ★ KD Skis ★ MasterCraft ★ PerfSki ★ Radar ★ Reflex ★ S Lines ★ Stokes

Drop a dime in the can

 

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  • Baller

Andy Mapple method for measuring DFT (as taught to me anyway...) - stand the ski on it's nose, measure DFT using the heads of the caliper. One head against the back end of the ski, the other head against the end of the fin. Other than a slot caliper this seems to me to be the most repeatable method. Personally once I get it close I go by feel - need a bit more tip, move the fin back 1/4 turn on the set screw. Need less move it ahead 1/4 turn etc. Works for me.

 

Ed

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Thanks guys - It seems that nothing in slalom is straightforward!

It amazes me that the ski manufacturers make life so complicated for us skiers. Why publish stock numbers if we don't know how they were measured and we can't verify any repeatable measuring method? Its just daft- much like selling skis without all major binding pattern inserts!

If they put factory markings on the ski and fin we would at least have a definite starting reference point that we could rely on, without messing about with callipers, slots, fin tools etc...

 

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  • Baller

I second @Ed's comment. I was taught this method by someone and I can get a repeatable measurement every time. Just use your thumb to hold the caliper tight to the flat portion behind the tail, and make sure if the tail isnt perfectly flat you are measuring the peak. Let me know if it works.

 

If you end up filing down the edges be careful, they are meant to have sharp edges and those are what the measurements are based off of.

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  • Baller

The other way to measure with a standard caller is to use the opposite end "tail". Extend the tip and put it flush on bottom butting into fin and then slide in. It gives a different measure, but it is easier to repeat. KL used that method when wrenching on fins when he was at our lake.

 

If you have a longer digital caliper, you can put it o the front of the fin and stretch it to the back of the ski, zero out the caliper and then measure to back of fin. I don't have this capability, but have seen it done.

 

Again, these are different measures from stock head measurements.

 

I use the heads and push flat to ski bottom with thumb. I take a few different measuerements and record the one that repeats more.

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