Edge tuning a modern slalom ski

[swbca]

How thick is the fiber layup in the bottom and sidewalls of the current slalom skis ?  I have a D3 EVO that I want to sacrifice to bevel tuning to see if the tuning methods I used in the 80's do anything useful on a modern ski.  In the 80's  I turned HO, Kidder, and EP skis into skis where I would consistently complete 35off 34mph in Men3 tournaments before that was common even in the Men3 Nationals.  Without the bevel tuning I wouldn't have been competitive on any of those skis.  With the modified bevel profile placed 4th and 2nd in Men3 Nationals practicing short summer seasons in Minnesota.

I did the same type of tuning my age14 son's 63" fiberglass HO and he ran 4 at 28off 36mph in his second tournament.  Because of the ski size he had to test the ski during the process.

At the time I would restore edge material on the skis by spraying and baking several coats of 2 part Dupont Automotive Epoxy on the edges where I was removing material, so in most cases I wasn't tuning past the outer resin coat on those skis. I could fail and repeat edge tuning endlessly by always replacing the material I had removed.

My initial work on the D3 would get to the first layers of fiber, but probably wouldn't need to go much deeper.  Any idea of how thick the outer coating is before seeing fiber ?

The question "why bother" when there are so many great skis ?  ITS A HOBBY and it would take a few weeks in the winter months for the initial bevel makeover before on the water testing.   

This is my son on the 63" HO ski he helped me tune.  4 @28off 36mph at second tournament.  Theresa Wright driver.  Paul Chapin boat timer

Edited December 30, 2023 by swbca

[gavski]

Sounds like you need to go ski with KLP…

[DW]

The outer gel coat will be .020”-.030”, the carbon fiber base material is vacuum bagged so very little resin skin.  Won’t take much to hit the carbon cloth.  Sounds like a good plan would be to find a ski you can chop up to experiment on, slice in half to see the construction, etc.

[Horton]

there's enough thickness in the graphic layer extra resin to hit it with sandpaper and change the bevel contours a little. if you want to go full on 1980s with a metal file you're going to ruin the ski quickly.

I understand back in the day, this was how skis were tuned. I don't think there are more than a handful people who do this in the modern era. The only people that are doing it today are actually ski designers. if you don't mind destroying skis, i won't discourage you from doing it but the odds that you're going to improve your skis seems highly unlikely.

[Horton]

for additional perspective. pick up a current high-end ski and compare it to the weight of a 1980s ski. a lot of that weight is the core and a lot of that weight is excess resin. current skis are made as light as is practical so there is no extra material to be filed off the ski without getting into the structure.

[Rednucleus]

Interested to see if the Adams comment - I always enjoy seeing @AdamCordshow up with his latest modification. 

[swbca]

22 minutes ago, Horton said:

if you don't mind destroying skis, i won't discourage you from doing it but the odds that you're going to improve your skis seems highly unlikely.

I can thicken the outer coating enouph with a durable resin that bonds well to stay away from the carbon fiber.   Unlike most of the old edge shaping practices I am making the bevel smaller rather than larger/rounder like Dave Saucier and Carl Roberge would do on their skis.  and it all happens in the back 18" of the ski.

[MDB1056]

@swbca you have no way to precisely measure measure what come off, or you put back on, or consistency over the area. This is quite frankly a chop-shop practice no longer needed. The dozens of iterations tested in development, modernized ski construction, and the proven performance envelopes of modern skis have long since eliminated those things done decades ago, which even then were simply WAG's. With the known capabilities of any modern ski you pick being far above what you or your son are skiing there's no question that your suggested hacking on the ski is not needed. Focus on technique and personal performance, not changing the stick.           

[ALPJr]

Seems like boot placement,  adjustable fins, and now adjustable tails have taken the place of tuning the bevels. Like others said, as long as you don’t mind sacrificing skis and risking injury… 

[DW]

@swbca - if you simply want to sharpen the bevel with added material, do the experiment with bondo.  If you like it, use a radius gage to measure before you simply sand or knock off the bondo to get back to original shape.  It would be a one or two and done trial.  Happy testing.

[Horton]

If this is just a fun hobby I am actually sort of jealous. This is fun stuff.

If you think you are going to learn much of value or actually improve your skiing this is a terrible idea. 

25+ years ago skis were much less refined and the only thing a skier could do was to file bevels. It was pretty common in the 1970 - 1980s. Today ski designers have much more control over factors like flex, torsional flex, and rocker. Ski shape is certainly more understood also. All that and skiers now have a better understanding of fin & bindings. I honestly do to remember the last time I saw a skier ( not a ski designer ) sand on a ski.

The idea of taking a current ski and filing the bevels is as logical as putting the carburetor from a 1980s boat on a new boat. 

I will say it again: If this is a hobby and fun is the point then I wish I was involved. If it is about skiing better I do not encourage it. 

[DW]

Hey, come on now, changing jets, pumping your throttle 3 times, smelling raw gas as you flood the engine, what could be more fun than that. 😂🤣

[swbca]

18 hours ago, MDB1056 said:

@swbca you have no way to precisely measure measure what come off, or you put back on, or consistency over the area. This is quite frankly a chop-shop practice no longer needed. The dozens of iterations tested in development, modernized ski construction, and the proven performance envelopes of modern skis have long since eliminated those things done decades ago, which even then were simply WAG's. With the known capabilities of any modern ski you pick being far above what you or your son are skiing there's no question that your suggested hacking on the ski is not needed. Focus on technique and personal performance, not changing the stick.           

First, You know nothing about what I can do.   

Second, Focusing on technique and personal performance using a ski that doesn't work for you guarantees mediocrity.  One way or the other you have to find or build the best ski for you by any means if you want to be your best and maybe become one the best skiers in your club, state, region or country. 

Third, "Proven Performance Envelopes" don't begin to touch the infinite number of possibilities that will continue to be tested and incorporated into future skis.  Of course the new skis are superior to the old skis, but ski designers all of whom are skiers will always push that progress forward.   

The D3 EVO is a good modern ski that doesn't work for me.  Other modern ski work great.  I know I can make the D3 EVO work better for me and that's what I do for fun.  I might even learn something that will help me improve my current favorite modern ski.   

Edited December 31, 2023 by swbca

[Deanoski]

I think it’s awesome tune away 

you have about 2-3 mm of material to play with 

I have sanded many skis over the yrs and I know a few skiers that also sand  bevels 

 

[BlueSki]

@swbca please post some updates of what you do and how things go. I have no intention of doing the same thing, I would only ruin a ski, but some of us that came after the ski tuning era might learn a few things. Have fun with it. 

[lpskier]

I’m sure someone (maybe his wife) told Edison that his “light bulb” thingy would never work. 
 

I’m fortunate to ski with a bunch of different skiers who, from time to time, experiment with all sorts of stuff. Granted, many are involved in ski design, but they aren’t shy about trying new ideas. Extra layers of carbon, bondo, changing bevels, different fin shapes, cutting down, softening or stiffening hard shells, etc.  I watched KLP and Parrish come up with the idea of attaching the Radar boot to a Reflex plate and then stiffening the boot with some carbon  The point is, thank God there are people out there thinking and tinkering. The only difference between them and @swbca is the supply if skis or bindings to work on and a market for whatever ideas work out. So don’t be such Negative Nellies. I for one am interested in hearing @swbca’s report and maybe seeing some photos. That information may, at some time, for some one of us, be helpful. 

 

[Horton]

32 minutes ago, lpskier said:

The only difference between them and @swbca is the supply if skis or bindings to work on and a market for whatever ideas work out

AND decades of experience ruining skis providing foundational knowledge for what is plausible and what is not plausible.

I'm a little negative on this project the same way I was push back on @eleeski . I really don't want somebody without experience to read this and think they should go attempt it and then destroy their gear. Additionally, there's so much adjustability and learning to be done just with fin and bindings.

Now if you told me we were going to have a contest where we're all going to build wood skis from a blank and we all had to tune them ourselves and make up everything from scratch, that's a contest I want to be a part of. That would be some fun shit.

[thager]

Never give Horton the opportunity to make wood!!!

[skialex]

@thager wooden fins maybe..?

[thager]

Or blue pills.....

 

[skialex]

Knew it immediately that I hadn’t gotten the joke… 🤗

[swbca]

@Horton  said . . . "I'm a little negative on this project . . . I really don't want somebody without experience to read this and think they should go attempt it and then destroy their gear"
___________________________________________________________________________________________________

No Worries . . . There is no information I could post on this forum that could be considered a "How To"  on wrecking your ski.   I may wreck the D3 ski I am working on, but it won't be structural damage because the functional modifications to the bevel area are accomplished by shaping material that is added, not by shaping the existing coatings or structural layers of the ski.  I only need to clean off the outer coating of the D3 ski for bonding because D3 skis have a highly soluble finish. 

and "Don't try this at home"  if I use the sprayable resin I used in the past, it can be dangerous if not handled carefully.  In one instance I didn't have access to my vented spray booth and I ended up in the hospital for 2 days with low blood oxygen and an incredible headache.  My wife thinks I had permanent brain damage 🙂

One push back.  In a recent poll on BOS I believe it was concluded that the ski itself is the most important part of the SKI-FIN-BINDING assembly.  If the properties of the ski can't be improved, why are there new versions of the best skis every year?  

Thanks to the couple of contributors that answered my question about the thickness of materials outside of the fiber.

This topic should be closed.

Edited January 1 by swbca

[thager]

For those iactually nterested in ski tuning there is a short section in the "Slalom with Andy Mapple" DVD produced by Gordon Rathbun about ski tuning. It gets into the why and how's of bevel tuning.   Excellent information.

[swbca]

3 hours ago, thager said:

For those iactually nterested in ski tuning there is a short section in the "Slalom with Andy Mapple" DVD produced by Gordon Rathbun about ski tuning. It gets into the why and how's of bevel tuning.   Excellent information.

Thanks . . Ill look for that DVD.  You mention Andy Mapple . . . my inspiration for the changes I make to my skis is from a side-by-side video of Andy Mapple and Nate Smith on the their initial setup and turn toward the gate.  On that setup, Mapple's ski was very "tail happy".  In that video he moderated his speed on the setup by transferring weight back multiple times braking with his tip very high multiple times. When he had too much speed at his most difficult rope lengths, his ski would snap to a very aggressive angle with his weight biased to the back. 

By accident I modified a kidder ski that was also very tail happy.  It would hold good angle at the finish of a turn with the tip engaged, but with too much speed it would also initiate a very aggressive angle (backside the ball) with weight shifted back a little.  That characteristic helped me ski rope lengths consistently when all but a few national level Men 3 guys were skiing into the rope waiting for their tips to engage.  As a fun project, I am going to try that same tune on my D3 that is collecting dust.

Edited January 1 by swbca

[101driver]

@swbca Well this subject certainly split the Ballers into 2 camps. My Vote is GO FOR IT. Reasons:

• From this post and others you clearly have been blessed with enough brains to do this and the capacity to understand your limitations.
• You have developed skills and knowledge but want more knowledge
• It's fun and you get pleasure from learning and just doing this

What is not to like about the above, we should encourage more of this freewill or agency otherwise we will all end up as minions just accepting a life as given.

• Sure you will make mistakes..........great that is how we learn
• The man who never made a mistake never made anything
• I agree with @DW make some edge profile gauges, I would recommend numbering them and recording your gauge profiles at measured distances on the ski so that you have a record to go back to. KEEP METICULOUS RECORDS.

GOOD LUCK, HAVE FUN and don't listen to the dissenters.

To the dissenters: your fears are well founded and you are right, going into this area especially with highly evolved products is high risk and requires a massive amount of base knowledge before even starting to scratch the surface. As an engineer I can quantify that subject better with greater depth of knowledge than many on this forum. What I can thus say as reassurance is that @swbca clearly has a good appreciation of the subject and a good appreciation of the risks. His quest to learn more is his own and is to be encouraged. Blindly following in his footsteps with out undertaking the work to gain that knowledge and the understanding to manage risk is foolish. in this respect you are completely right and I support your concerns.

[Octopus_Paxarbolis]

I imagine a @Horton is mumbling something to himself about Dunning-Kruger.

[Horton]

@Octopus_Paxarbolis Every day brother. Every darn day.

For fun, I was looking at the below image of a ski cross-section and wondering how to make the bevel radius smaller without changing the sidewall height, and the transition radius from the tunnel to the radius. Pretty sure this is why ski designers work in CAD cut test molds. 

 

[101driver]

Absolutely right @Horton and if you are in the ski design and build business that is the most efficient way to go. I would go so far as to say the only way to go. R and D is hard and in business you have to manage that otherwise you are not around for long. BUT it is not the only way you can do this. You can do this by hand in your shop if you want to, the problem is the hours of work tears and pain of trying to manage the process and navigate inconsistency is just not worth it for most. The second biggest problem is if you break through that skin into the core you open up a whole other world of pain, hence why @swbca asked the original question. You can do it but in my experience of doing this with knee boards the best you will get is a prototype for development test purposes. Best efforts best materials hours of work yield poor reliability. But you learn and move forward. 

SO WHY DO IT it is great fun and immensely rewarding.............and when the baby that you have nurtured and laboured over performs the feeling of elation is like no other.........until the next test when it all goes wrong and you go back to your shop with your baby in a bin bag.

LOGICALLY don't do it it's not worth it

EMOTIONALLY go for it you only live once do something you want to do

[101driver]

I am going to try and explain something which 90+% of you just will just not get and in that respect I will fail. Sorry I am not gifted with the words to do this better.

20 ish years ago I had little money and I took a broken kneeboard and repaired it for my young daughter.  I had no choice as I did not have the money to buy a new one. It worked for a while then broke. In the mean time I read every write up on the latest kneeboards and why they were so good .............so when I rebuilt it the second time I took some of those ideas and incorporated them. The story repeats many times.

Years go by and I now have a good job, so I buy my daughter the kneeboard she always wanted and the one I always felt she deserved. It has all the wonderful design features that I had struggled to replicate and it's done so much better as it's now evolved to a higher level and the execution is reliable and lighter and...........

Daughter rides the new board and it's amazing, months go by and Daaaaaad "I really love the new board but it's not the same as OUR board can't you rebuild OUR board one last time, I promise I won't break it again"

There is something else here other than the tangibles that we can measure. When you visit a religious site there is a feeling which is hard to explain best quote for me "practice something in ritual space something is left behind" It's the same when I pick up an old hand made gun that someone laboured over a hundred years ago, there is something there you don't get with a new factory made gun.

I can absolutely guarantee even though I have never met @swbca or his son that in many years to come when at the end of his days @swbca  and his son looks back at his life it will not be the latest wiz bang ski they talk about, it will be the summer of 2023 and the ski dad built/developed and son tested and the great time that they had.

PRICELESS

[The_MS]

[swbca]

23 hours ago, Horton said:

For fun, I was looking at the below image of a ski cross-section and wondering how to make the bevel radius smaller without changing the sidewall height, and the transition radius from the tunnel to the radius. Pretty sure this is why ski designers work in CAD cut test molds. 

 

For fun, I was looking at my 66" KD Titanium this morning.  They have implemented the same "TUNE" on the Titanium as I implemented on my Kidder and HO skis and the same Tune as I plan to implement on my D3.   .

The flat spot KD imposed on the ski creates a sharper bottom edge on the bevel on each side that slightly flattens the lateral flow of water off the bottom edges of the ski.  Before you examine your KD, look closely under a single point light source.  The actual transitions are softer than the sketch above.  Before you decide it doesn't exist look at 9 5/8 DFT where it is most visible. It fades 4" in both direction from 9 5/8 DFT. . . . Like with fin adjustments, this small thing makes a big difference and can't be replicated with fin adjustments or binding placement. 

The actual final tune is settled after testing several iterations to control how sharp or soft the bottom edges of the bevel are and where flattening starts and stops on the ski.  On the D3, I will be able to cut and restore without limits by recoating the area with sprayed resin. 

Edited January 3 by swbca

[Octopus_Paxarbolis]

Tell us more about how awesome you were in the 1980s. Please tell us more.

[swbca]

5 minutes ago, Octopus_Paxarbolis said:

Tell us more about how awesome you were in the 1980s. Please tell us more.

Got nothing else.  When your on some un-named spectrum you really suck on the stuff you don't care about.

[101driver]

@swbca I think what you are doing is really interesting and your approach is sensible and well thought through. Please continue to post.

[Deanoski]

I will follow this thread 

great stuff IMO 

[DW]

@swbca A lesson learned from years of my involvement in testing and development, many finds / discoveries / ah-ha moments came from the unexpected, errors and not only from something I actually expected to work.  You touched on it, I assume that asymmetry will be part of your program. 

[ForrestGump]

What is going to be better with the sharper bevels? What are the expected results?

[swbca]

This is my last post on this thread that had become to long. Thanks everyone for feed back.

A few months ago @Horton looked out his window and said this feature doesn't exist on the Titanium.  Of course he had to be right and I had to be wrong.  End of discussion.  That is why I have been careful to illustrate this feature on the KD Titanium

@ForrestGump asked "What is going to be better with the sharper bevels? What are the expected results?"

I was hoping no one would ask . . .

Even on the best modern skis, for many non-pro skiers, as the rope shortens they progressively get more slack to the point they can't complete the pass.

It appears to me they only have one mode for executing turns . . . which is to follow the natural arc the ski provides when they execute their turn.  The don't fully engage the tip to complete the turn in a hurry and they have no other aggressive technique to avoid skiing down course when they need to be skiing cross course.

From my experience with this bevel modification, the sweet spot for finishing turns isn't limited to using more tip pressure. It widens the sweet spot so the ski will complete the turn in a hurry with less dependency on skiers exact balance over the ski.   The desire result is to be able to come into a ball fast and late and then backside the ball without tip pressure and never see slack.       

EDIT: Disclaimer

I don't recommend anyone act on this.  I tested 100's of variations of this on four skis over three years.  I had heat-lamps in a paint booth working all summer most of the time to try variations.  

If the near identical feature on the KD Titanium was deliberately done for a reason, I wouldn't expect their rational would have anything parallels to what I experienced.  

Edited January 3 by swbca

[101driver]

@swbca YOU CAN"T QUIT NOW this is way more interesting than our normal source of data the manufacturers marketing mans BS. Would some one who knows @swbca better than me go and give him a cuddle or something.

So I am trying to get my head around this with my limited understanding, please correct me anyone who knows more..........

We have an unmodified ski which we put into a short line turn, turn is compromised by late or whatever and the skiier needs more angle but with a smooth transition into the pull..........Normal action would be tip engagement more smear + yaw + forced load on rear to smear more............so we end up with a really narrow window of good behaviour where either it over smears and then snaps back down course wheeling or under smears and we either don't get the angle or we wait for ever for the ski to come around and then have a late rough pull.

Sharper edge as proposed by @swbca would control the smear more when on high yaw and the fin is achieving less resistance to smear.......soo I think that would permit a ballance shift. The need for a fully engaged tip is now not so critical, the arc can be generated with less tip engagement so it is easier for the skier to complete the turn and also get to the right position for the pull...

Someone rip the above apart please so I learn more!

[Horton]

@101driver

Bevel radius / shape is but one design element. A complete ski design is a synergy between all the elements. 

As the bevel gets larger or rounder it has less grip and allows the ski to sit deeper and smear more. This could seem counterintuitive as one might visualize a higher riding tail having more slide but it is the other way around.

Sharper bevels between the back foot and the fin will make a ski faster but less friendly - more twitchy. There is no perfect bevel radius and every current designer has a slightly different magic sauce.  

@swbca 

if you are saying that you are going to block sand the bottom of the ski to create a bottom bevel edge, that makes more sense then adding material and trying to then create a smaller radius. 

I am not sure I have been snarky with you on this topic. I am doubtful this project will improve your ski but I am sure it will be entertaining. There is also a chance you will prove me wrong. I look forward to before and after videos of you skiing on the modified ski. 

[101driver]

@Horton Thank you for your input and clarification. Your explanation of counterintuitive effect is exactly why I believe posts such as these are important, they educate and enlighten, with greater understanding comes more informed questions and the process self drives.

The process of changing one element and how that changes the synergy is endlessly intriguing for me, not least because you can then tune back some changes with fin and balance, then add a third layer of the human elements and skills and how they interact with the change. 

I have a different perspective on "I am doubtful this project will improve your ski" In a pure sense of producing a mainstream ski on the shelf for the masses with higher performance yes you are right. The proposal that @swbca tabled was for a custom tuning type scope of project inspired by elements from personal tuning of ski's in the past. For me personally this resonates with the excellent chapter in Fin Whispering by Jay Poscente where he explains how tuning can help someone with a particular habit achieve more by synchronizing ski and skier. (NOTE NOT COMPENSATING FOR FUNDAMENTAL FLAWS). I feel that our understanding of the ski and how it reacts and works in response to our technique or in my case lack of it helps that understanding of our faults and helps drive the skills. Yeah you can drive a car with out knowing how it works, but the best race car drivers come into the pits with informed reasoned feedback to their specialist mechanics. 

AND AS I HAVE SAID BEFORE THIS IS FUN

[Mastercrafter]

I have designed and built a lot of proprietary equipment for my business that makes us efficient and profitable. I tend not to share all (any) of my secrets. I see no reason why the owners of a waterski company would/should chime in here. 

[swbca]

22 hours ago, 101driver said:

For me personally this resonates with the excellent chapter in Fin Whispering by Jay Poscente where he explains how tuning can help someone with a particular habit achieve more by synchronizing ski and skier. (NOTE NOT COMPENSATING FOR FUNDAMENTAL FLAWS). I feel that our understanding of the ski and how it reacts and works in response to our technique or in my case lack of it helps that understanding of our faults and helps drive the skills.

Exactly, If I hadn't left his book at our cabin, I was going to quote some of his points on this.  Whether its body structure or habits from 12 years old I always had to make changes to stock skis for them to work well for me.  And it was often the same problem on every ski.  I didn't try too hard to adapt to the skis, because my work arounds always seem to work very  well.   

Edited January 4 by swbca

[scoke]

[ral]

For sure you can take a ski that allegedly does not work for you that is two generations old now and tweak it to make it better for your particular skiing style, reducing its resell value a lot and spending several hours in the process.
 

Or you could trade it for a newer generation one  (ION & ION 2), that have hundreds of hours of expert R&D and world-class testing on them, and see if it works better (which has been the case for all skiers I know that have upgraded their EVOs).

I guess it all depends on the pleasure derived from the tweaking process and placebo effect v/s  the pleasure of more probable better skiing out of the box with the newer versions. 

[DW]

Or you could start making ski's in your garage hoping someday people may want them because they perform really well (*cough* Adams) or maybe just to transport some unique substances or because your ski pole company allows you to fool around with carbon fiber decades ago.  Or just buy a new ski as that is clearly easier.

[swbca]

@scoke @ral @DW

I have a new KD ski and you missed the context.
I sidelined the D3 years ago and said this was a HOBBY experiment. Had no hopes or intention to have the modified D3 as the ski I would use.  

 

[Ski2000]

@swbcaI for one like what your doing. I wish I had a project to keep me engaged in skiing while it’s cold but no snow on the ground. I have often wondered if I could modify some of my old skis to fit my kids who are 60 -100 lbs lighter than me. 
Keep it up. 

[swbca]

3 hours ago, Ski2000 said:

@swbcaI for one like what your doing. I wish I had a project to keep me engaged in skiing while it’s cold but no snow on the ground. I have often wondered if I could modify some of my old skis to fit my kids who are 60 -100 lbs lighter than me. 
Keep it up. 

Speaking of Winter

While working on the D3 today, I was reminded that I have always enjoyed the craftsmanship dimension of working the edges of skis.  Its January in Minnesota and I am doing something I love to do.  I can't test anything until spring but that doesn't take away the fun of perfecting methods of tuning skis without degrading their factory new look.   Not a fan of Bondo. 

Your Kids

It would be a huge challenge to modify skis for your kids, if you were expecting good performance.  I did that once for my son before he had become a good slalom skier.  It was sort of a waste of time because the ski didn't work.

It also depends on the 60-100  pound difference.  Is that a 20% difference in weight or a 70% difference in weight.

 

[mmosley899]

@swbca have fun! I have been adjusting skis for over thirty years, sometimes they get better and sometimes you just move on to the next ski. If you ‘know’ what you are doing you can at least decide whether it worked or not. For those that do not ‘know’, they should not try this at home!