Why some skis are more sensitive to fin settings then others

[Horton]

An idea that I have heard from at least 2 of the smartest guys I know is: skis with the bindings closer to the fin are more fin (and water temp) sensitive. The bindings on my D3 ARC and Radar Vapor are more than an inch forward compared to my Goode XT or Warp. Fin settings are important on all skis but on the Goode and Warp it is extra critical.

 

Clearly the distance between the fin and bindings is only one of many factors. The shape/design of the Goode is very different from the Warp. I found different setup challenges with these two skis.

 

@SkiJay what do you think?

[skiep]

I agree. Fin center and binding center closer together the fin has less leverage over you. (easy to over smear) Farther apart the more leverage fin has over you

[evolski]

agreed - haven't directly measured S2 vs Reflex, but based on holes vs plate location - S2 further apart hence reflex much more sensitive; and it is. S2 i can almost use a ruler to set it.

[MrJones]

Horton.

Aren't you on a 65" Nano and a 67" Radar?

[Horton]

@MrJones advertised ski size is besides the point. Advertised size is more about marketing than ski design. That is another thread.

 

Both of those skis are correct for my weight and skiing level.

[Gar]

I tend to agree.

[Bruce_Butterfield]

My first reaction is that the overall ski design and not any 1 or 2 particular attributes. But as I think about, I think that, ski weight may be the dominant factor in making proper fin and binding settings extra critical.

 

Just one theory.

[Razorskier1]

Heck if I know . . . I just ask people smarter than me for suggestions.

[Horton]

@Bruce_Butterfield the actual weight of the ski?

[MrJones]

Horton.

Yes, but I have both of those skis in the rack and the Nano is a good bit shorter than the Vapor regardless of advertised size. I'm not disagreeing with you about the concept, but those 2 skis don't seem to prove much in regard to binding distance from tail. :)

[Than_Bogan]

Well, it's only one piece of data, but the original setup for the Denali 3.1 was quite fin-sensitive whereas the '17 is not at all, and one of the fundamental difference is that the boots are waay further forward now.

 

So that fits the theory.

[BRY]

+1 to @Bruce_Butterfield with "My first reaction is that the overall ski design and not any 1 or 2 particular attributes." Though to his second part I don't think weight has anything to do with it.

 

Some skis from Goode:

Rev6 68"-190 lbs. and up 29.75” (+- 1/8)

Nano1/Nano XT 66.75″–195 lbs. and up 29.25” (+- 1/8)

Nano1FT 66.75″–195 lbs. and up 29.00” (+- 1/8)

 

Vapor 68" 180-220 lbs 30.25" though Rossi posts 30" and Brooks set mine there at Nationals. 30" seems to work better at 36 for me.

[DW]

@Horton : that theory makes sense, think of a car wheelbase, shorter wheelbase makes a vehicle much more responsive and sensitive to steering inputs and also sensitive to alignment changes. An even better comparison would be a motorcycle and same applies.

[Horton]

The factor that I think everyone is overlooking is the square inches of tunnel and amount of bevel between the bindings and fin. The tunnel and bevels create some amount of grip. If the bindings are way back there is simply less grip created by the shape of the ski and the fin has to carry more load.

 

Besides all of this, the shape of the tunnel and bevels is also a real factor on the impact of the fin.

[Bruce_Butterfield]

@horton yes actual ski weight. Would you agree that as a general rule a lighter ski will be more responsive? Isn't a more responsive ski necessarily more sensitive to setup? Goode and the warp are pretty much the lightest skis out there.

 

Try a little thought experiment: pick one of the older D3s that we used to joke that you could put the fin on backwards and it would still ski just fine. Now give that ski a hollow warp core and pretend it weighs 1 lb. would this make that ski more responsive and sensitive to setup? Now take your Warp and give it a 10 lb pvc core. Do you think it will still be sensitive to setup?

 

Of course this is just a theory and 1 piece of the ski design.

[liquid d]

Flatter skis seem to make it very critical, also stiffness will affect it.

[Horton]

@Bruce_Butterfield a 67 inch X7 sits deep in the water and the front binding is about 30". Weight could be one factor but there is a lot of ski generated grip between the fin and bindings.

[SkiJay]

@Bruce_Butterfield is right about the deeper a ski rides, the less sensitive it is to fin changes; and I believe @Horton's comment on the tunnel and bevel effects is part of this effect. @skiep is on the right track too. The amount of leverage the fin has does contribute to adjustment sensitivity. The longer the moment arm, the more adjustment-sensitive a ski will be. [Moment arm: The distance from the fin's center of pressure to the ski's ever-changing, somewhat-central pivot point].

 

But perhaps the most significant factor affecting fin adjustment sensitivity is binding location—or more specifically, the amount of the area the ski’s tail has behind the bindings. As the ski rolls up onto an edge, the fin is less and less effective at resisting smear (how much the tail drifts sideways), and the more effect the size and shape of the ski’s tail has.

 

 

As the bindings move back, tail area gets reduced. When the bindings get too far back, the fin has to work overtime to control smear around the ball. This can lead to fin settings that undermine width and space in the course. If the bindings go too far forward, the tail gets so much traction at high roll angles that the fin gets taken right out of the game while going around the ball. This too can lead to inefficient fin settings.

 

Put another way, at medium roll and lean angles (i.e. during the cut for most mere mortals) the way the fin affects width and space in the course is highly fin dependent. And around the ball at max lean and roll angles, the ski’s tail area affects smear the most. The ideal setup will blend these two relationships for great course width and controlled smear at the ball—and this ski will very likely NOT be overly sensitive to fin adjustments.

 

So the question posed here is more complicated than it first seems. To skiers who are most focused on building width and space in the course, they are more likely to notice fin adjustment sensitivity with skis that have their bindings further forward than usual. For skiers more focused on how the ski smears around the ball at extreme speeds and lean angles, binding-back setups will stand out as being the most sensitive to fin adjustments.

 

Simple! Right?

[brettmainer]

I like beer

[WaterSkier12]

^^^

Made me choke on lunch!!!!

[Gar]

Makes sense!

[WaterSkier12]

Meant Brett's comment, NOT Skijay's explanation. Still digesting his book