Jump to content

Fin depth variation from side to side


disland
 Share

Recommended Posts

  • Baller

Is the fin perpendicular to the ski? Pull the fin block to make sure the fin sits at a 90 degree angle to the fin block when everything is tight. Then check to see when attaching the fin and fin block to the ski if it stays at 90 degrees to the bottom of the ski. The fin block could be flexing the fin or the ski could be putting the fin block at an angle. You can also completely remove the fin and place it on a flat surface to see if it's bent.

 

There is always some difference which is why you make your measurement routine consistent (always measure the same side) but as a sanity check the above will make sure there is nothing seriously wrong.

 

As a final check, after you fix the left right difference do you ski better or worse? ;)

Link to comment
Share on other sites

  • Baller
As @DanE pointed out, the head of the caliper sits in a different spot when measuring each side. The head is closer to the tail on the right than the left. The bottom of the ski flattens more toward the tail. This could account for some or all of the discrepancy. Use the needle of the caliper in the exact same spot for each side.
Link to comment
Share on other sites

  • Baller

What you describe is very common and especially with a two piece clamp. Loosen the clamp from the ski, tighten the fin and then screw the clump Back little by little while measuring both sides, use sims between the fin and ski slot if needed. When everything is tighten down and both sides measure the same or close, then you are ready to adjust your fin.

Good luck,

Alex,

Link to comment
Share on other sites

  • Baller_
Its likely that tail of the ski is not perfectly flat while the clamp is. Check if you can get a feeler gauge between the clamp and ski. The difference caused by the caliper head from side to side may be a thousandth or 2, but not significant. Also think about the manufaturancing tolerance of the tail thickness. I wouldnt be surprised if something in the range of 0.010" was typical, but I don't think anyone ever really checked. I know I haven't before.

If it was easy, they would call it Wakeboarding

Link to comment
Share on other sites

  • Baller

Yes this is normal @disland. Out of the many hundreds of skis I've measured, maybe three have been the same on both sides of the fin. I think the average would be around .004", but it's not uncommon to see differences of around .010". I've not noticed any correlation between the size of these differences and specific manufacturers.

 

I've also dicked around for hours trying to make some fin's measure the same on both sides without shimming, but with only minor success (@skialex is on the right track). The only way you can get FD exactly the same on both sides by shimming underneath the fin block (between the block and the ski) on the deep side of the fin. But does this introduce twist in the tail?

 

I've had the opportunity to dig through bags of Fin blocks from two of the main manufacturers and was able to find some blocks that were better than others. What I didn't try was then seeing if the best blocks were good on other skis. So while the cause appears to be manufacturing tolerances, it's not clear if those good fin blocks were the most accurately machined pieces, or just good on those particular skis. I suspect it's the latter.

 

I will say that the accuracy of ski manufacturing these days is remarkably good. And that for the most part, this FD difference won't affect most skiers in any significant way. Skiing technique adapts quickly to such nuances, and skilled ski-tuning quickly finds an optimal sweet spot.

 

What's most important is to always measure your fin on the same side while tuning.

Link to comment
Share on other sites

  • Baller

@SkiJay your comments about manufacturing tolerances pose an interesting question I haven't seen yet. What are ski manufacturing tolerances? What are fin and fin block manufacturing tolerances? Are they tight enough that measuring our find down to 1/1000th is really productive?

 

This is more philosophical discussion, I still measure my fin to the 1/1000th.

Link to comment
Share on other sites

  • Baller
@Wayne That only matters for number sharing, which is miles away from a precise practice. As soon as you start making adjustments to suit your own technique, all that matters is repeatability. And the quality we have now borders on overkill.
Link to comment
Share on other sites

  • Baller

I asked about this to Rossi. Rossi said the variances are typical. He said that he and the folks at Radar measure with the tip of the ski pointed to the left. I think as long as your are consistent and always do it the same way, your adjustments will yield the desired changes to ski performance.

 

FYI, Here's Rossi measuring fin depth:

 

Also, just fYI:

 

 

Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
 Share

×
×
  • Create New...