Defective Fin Block

[Gloersen]

Plagued with inconsistent Gates/1B & unpredictable 2B’s finally determined that the fin keeps moving; gets deeper and also a tad longer.  Tuned it to 2.506/6.880/.735/7 for last Saturday’s tournament. Skied 5 sets since, somewhat inconsistent in getting a good rhythm, measured fin at 2.515/6.883/.732

 

 

This movement had been noted about a month ago, thought the problem was due to an inadequate diameter of the bore recessed into the halves of the fin block to permit the DFT set screw unimpeded travel. Once this was determined, the set screw was used to set the fin at desired DFT, the clamp made snug, then the set screw backed all the way out from the clamping halves to permit final tightening of the fin clamp & unimpeded fixation of the fin tabs.  Then a final re-measure to verify chosen settings.

 

 

Turns out this was not the only problem. The right half (looking from top) of the fin block was improperly machined, not only the bored out recess for the DFT set screw was inadequate, so are the two recesses for the two top set screw housings on the left half of the clamp. Just visually inspecting it side by side with a new fin clamp on a club member’s new RCX; one can see at least a millimeter less radius in the bored out recesses. This of course was leading the two clamping halves tightening against themselves at the set screw housings and thus inadequate fixation of the fin tabs.

 

 

Switched to a fluid motion nylon block until the D3 fin clamp (03/10 Z7 ST) can be replaced.

 

 In conclusion: a good reason to become proficient in fin tuning and reproducible measuring techniques; identify a potential & remedial source of inconsistent skiing. In all likelihood there may be quite a few defective fin clamp assemblies out there. 

 

 

[skibug]

I noticed the same thing on me 07 Nomad RC in 2008.  I took the fin clamp off and used a dremel tool in the recessed areas to open them up a little bit.  This allowed the clamping screws to actually tighten with out bottoming out the half of the clamp that fits in the recessed area.  It was an easy fix and it didn't take much to open up those recesses.  At the time I was quite aggrevated though; thinking that they should of have had some +/- tolerances built in to the design.

[Jim Neely]

I had the same problem (clamp bottoming out and not holding the fin) on my radar. Radar replace the block and fin.