[recreational tuning] Choosing base and side bevel angles

[Jamt]

Eh, taxiing on an airplane right now. Will see what I can find once we get above 10,000'. Maybe @Jamt has something at the ready...

The thing with the critical platform angle is that it needs to be aligned with the body joints.
If you reach a critical platform angle in a turn the forces increase quite rapidly. If e.g. the knee joint is outside the force vector at this time the knee will be pushed to the outside which may reduce the platform angle to below critical, which will reduce the grip and the ski will slide a bit. In turn that reduced the force, knee moves in again reaching yet again a critical platform angle, repeat... This is how chatter happens. Alignment of equipment and better technique will reduce it.
Part of the alignment is the base bevel angle, in particular when the surface is hard..

 

[James]

Part of the alignment is the base bevel angle, in particular when the surface is hard..

Can you elaborate? How does going fom a 0.5 to a 1 deg change things for the skier in terms critical edge angle?
And wouldn't a more acute edge penetrate deeper and change things?

 

[Jamt]

Can you elaborate? How does going fom a 0.5 to a 1 deg change things for the skier in terms critical edge angle?
And wouldn't a more acute edge penetrate deeper and change things?

On hard snow it means that you need to edge the ski 0.5 degrees more with 1 degree base bevel before you get critical edge angle.
If the ski chatters with 0.5, it may not with 1.0.
If you want more penetration I think it would be "safer" to experiment with side bevel.

 

[James]

So, a brief tangent to critical edge angle. Questions-

The 90deg is measured from the line of action to the platform which would be the bottom of the base edge, right?

Now, the angle is the angle on the downhill side? Downhill or essentially over the ski as opposed to extending the platform line into the hill, and measuring the angle between that and the line of action.

That right?

 

[cantunamunch]

Can you elaborate? How does going fom a 0.5 to a 1 deg change things for the skier in terms critical edge angle?
And wouldn't a more acute edge penetrate deeper and change things?

On hard snow it means that you need to edge the ski 0.5 degrees more with 1 degree base bevel before you get critical edge angle.
If the ski chatters with 0.5, it may not with 1.0.
If you want more penetration I think it would be "safer" to experiment with side bevel.

Alt-tangent -> I think this entire thread is working with too idealised a ski model.

@Jamt 's post here begins to point down the path I envision, that of visualising the ski as a flexible, vibrating system that has to settle into an approximation of a commanded edge angle, with that settling time being dependent on base bevel, sidecut, flex/torsion.

Put another way, bevel angle models use a rigid skate model where the command lag to achieving any angle is zero. If we allow twist in the edge angle model, the discussion becomes a lot more interesting, because different angles can result in different command lag, and different settling times. Every one of which will affect the sensation of sharpness, notchiness &c.

 

[Viking9]

I went with the .5 and 3 on my new hero ST’S , let’s say I don’t like it and want to go back to a 1 , 2 am I losing a lot of life with the bases or is it nothing.
I’ve tried a 3 with my old pursuit 16’s and did not like it, to me it held the turn longer and that’s not always good for my style.
Thanks.

 

[oldschoolskier]

My skis are set as follows 0.5/4 GS and 0.7/3 SL (skis came tuned that way from @ScotsSkier ), precious SL’s were 0.5/4. I will likely make the change to the more aggressive edge when I need a base grind.

As to issues none. Reason is simple, ski neutral in all conditions. OTHERWISE skis tuned like this will punish errors. Either you learn or you like eating snow.

The rewards for tunes like this is amazing, but be prepared to get there.

As to the best compromise tune a 1/3 is the choice I give everyone else for Family and friends (unless they want to work it). Enough forgiveness (the 1) with bite in hard to ice (the 3).

 

[cantunamunch]

I went with the .5 and 3 on my new hero ST’S , let’s say I don’t like it and want to go back to a 1 , 2 am I losing a lot of life with the bases or is it nothing..

almost nothing - and there is no base life cost since .5-> 1 is edge-only correction and 3-> 2 is a side edge correction.

Notice also that normal base edge wear will naturally push the base edge towards 1.

 

[Viking9]

Ok thanks , appreciate it .

 

[oldschoolskier]

Couple of points on base and edge bevels.

Base angle is the “detune” of the old days. The bigger the number the slower the bite. So 0 is a almost instant response (no forgiveness) and 1 there is a delay (or forgiveness), everything else is in between.

Side bevel is how well they hold on edge, but must be combined with a the base number (side - base = net side). So a 1/1 is a net 90, a 1/2 is a 89, a 1/3 is a 88 and a 0.5/4 is a 86.5.

So when you look at a 1/3 and see the the net number it doesn’t look so aggressive anymore (by the way 88 was the sort of go to standard for straight skis for several years prior to shaped skis).

As to not liking any tune generally it is not the tune but the quality of it! The tuner left a burr that is causing you issues. Burrs depending on side or base will cause you different issues.

Burrs from the base tune will feel very sharp, though generally rarely happen (other than edge damage) because the side tune will remove them.

Burrs from a side tune are common. These will make a ski grabby, twitchy to do right uncontrollable! These are due to the nature of how edges sharpen. Poor sharpening technique only worsens the burr.

In all cases the burrs must be removed.

• So at worst an aggressive well tuned ski will feel aggressive but controllable.
• A poorly tuned non aggressive tune will feel aggressive and uncontrollable!
• A well tune 1/3 should feel comfortable and hold. It should never cause any issues.

 

[François Pugh]

I went with the .5 and 3 on my new hero ST’S , let’s say I don’t like it and want to go back to a 1 , 2 am I losing a lot of life with the bases or is it nothing.
I’ve tried a 3 with my old pursuit 16’s and did not like it, to me it held the turn longer and that’s not always good for my style.
Thanks.

If you don't like your 0.5:3 tune, then try 1:3 before going all the way back to 1:2. You won't loose any base or edge life going to 1:3 from 0.5:3.

 

[oldschoolskier]

I went with the .5 and 3 on my new hero ST’S , let’s say I don’t like it and want to go back to a 1 , 2 am I losing a lot of life with the bases or is it nothing.
I’ve tried a 3 with my old pursuit 16’s and did not like it, to me it held the turn longer that’s not always good for my style.
Thanks.

Check to see if you have a hanging burr first.

 

[Jacques]

My skis are set as follows 0.5/4 GS and 0.7/3 SL (skis came tuned that way from @ScotsSkier ), precious SL’s were 0.5/4. I will likely make the change to the more aggressive edge when I need a base grind.

As to issues none. Reason is simple, ski neutral in all conditions. OTHERWISE skis tuned like this will punish errors. Either you learn or you like eating snow.

The rewards for tunes like this is amazing, but be prepared to get there.

As to the best compromise tune a 1/3 is the choice I give everyone else for Family and friends (unless they want to work it). Enough forgiveness (the 1) with bite in hard to ice (the 3).

Workin' It!

 

[Fishbowl]

• “So at worst an aggressive well tuned ski will feel aggressive but controllable.
• A poorly tuned non aggressive tune will feel aggressive and uncontrollable!
• A well tune 1/3 should feel comfortable and hold. It should never cause any issues”

I know a good tune can make a difference, especially on hard pack, but how much?

Am I really going to have an “uncontrollable” ski just because the tune is a little sub par?

 

[mdf]

Am I really going to have an “uncontrollable” ski just because the tune is a little sub par?

If really bad, it can make edge grip turn on and off unpredictably. A typical bad tune just fees like a lousy ski.

 

[Sibhusky]

It's sort of amazing the impact a tiny burr can have in the wrong location.

 

[François Pugh]

• “So at worst an aggressive well tuned ski will feel aggressive but controllable.
• A poorly tuned non aggressive tune will feel aggressive and uncontrollable!
• A well tune 1/3 should feel comfortable and hold. It should never cause any issues”

I know a good tune can make a difference, especially on hard pack, but how much?

Am I really going to have an “uncontrollable” ski just because the tune is a little sub par?

The sharper more aggressive tune makes a big improvement if your carving arc-2-arc, not so much if your smearing turns. A less aggressive tune is easier to feather in bumps and probably preferable if your in moguls or smearing turns. The only down side with a more aggressive tune is if you stop paying attention you can easily catch an edge.

 

[oldschoolskier]

The sharper more aggressive tune makes a big improvement if your carving arc-2-arc, not so much if your smearing turns. A less aggressive tune is easier to feather in bumps and probably preferable if your in moguls or smearing turns. The only down side with a more aggressive tune is if you stop paying attention you can easily catch an edge.

IMHO a 1/3 is not an aggressive tune, as the 1 in the base provides all the forgiveness you need.

 

[oldschoolskier]

• “So at worst an aggressive well tuned ski will feel aggressive but controllable.
• A poorly tuned non aggressive tune will feel aggressive and uncontrollable!
• A well tune 1/3 should feel comfortable and hold. It should never cause any issues”

I know a good tune can make a difference, especially on hard pack, but how much?

Am I really going to have an “uncontrollable” ski just because the tune is a little sub par?

A good tune is the best thing you can have in all conditions (maybe except park skiing as tunic goes out the window on the first rail grind). Predictably and a well behaved ski makes things easy. In conditions where you need the edge it greatly builds confidence as the ski bite when you want them too and not skid.

As to a poor tune.....YES....it can make great skis be crap skis. As mentioned it can do all sorts of unpredictable things including making the ski dangerous at moderate and above speeds. Go read threads containing “I had my skis tuned and they don’t work” type threads. 99.999% of the time a hanging burr was left on the ski.

 

[Fishbowl]

Multi quote............

Yikes, but thanks for the heads up.