Edge tuning a modern slalom ski

[swbca]

Here's another way to keep your head into skiing through the winter.  Install a 37.5 foot width guide in your boat. 

This idea was borrowed from the OffCourse official method of calibrating OffCourse.

This is one of my ski partners skiing behind my boat at 35off 34mph.   The blue floaty stick is permanently mounted in my boat so you have some idea of your width when Free Skiing when your course isn't available.   The floaty stick is permanently installed for 35off because that's my starting length when free skiing.  Needed something that would bend over because the rope gets dragged over this spot every time the skier pulls out to stop at the end of a pass.  For flexibility, the floaty slips over a 1" PVC pipe that is fastened to the boat's side pocket near the floor.

Needed the height of the floaty stick so it's high enough to show in the video like below.  Tape on the deck works too, but it doesn't show in your videos if you prefer a normal focal length view of the skier. 

If you are free skiing at 35 off, you can glance at the boat to see if the blue marker is in line with the pylon.  If not you're skiing too narrow.  The camera is pylon mounted so in this photo the camera, the blue floaty and the real ball are exactly in line.  I used a trig calculator to locate the blue floaty, so I didn't need the boat in a big yard to lay it out as suggested by the OffCourse manual.

Edited January 10 by swbca

[DW]

Nice idea, is it mounted to the gunnel?  I have seen posts where the side of the boat was striped (by line color) as a width marker.  My ski partner has a box mounted on the pylon that turns on a light at the correct angle.  The next addition is to add the time element so one ski's at the correct frequency & width when absent of buoy's.

[swbca]

On 1/3/2024 at 4:03 PM, Horton said:

@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. 

You can't flat sand the bottom of a D3 ski to substantially reduce the size of the bevel because the coating thickness before you get to the fiber is negligible.

Here is how to reduce the size of a bevel on a modern ski. (You drew a sketch trying to figure that out)

1. spray a high quality resin or industrial paint on the bottom, the bevel and the side wall.  3 or 4 double coats over a few days is substantial.

2. Block sand the bottom all the way down to the original ski coating.
3. Block sand the sidewall all the way down to the original ski coating. 

This increases the dimension of side wall and widens the flat area on the bottom of the ski  . .  thus a smaller bevel.

With good technique, the uniformity of thickness from 10 coats of spray material can be very good.  so the finished result has good precision in appearance and function.

For performance tuning, you then reshape the sharp edges that have been created at the bottom and top edge of the radius bevel.  

I couldn't get the Dupont Epoxy paint to spray any longer so I used a high quality automotive caliper paint.  Very durable and the coats dry fast.

[AdamCord]

@swbca I haven't read this whole thread so I apologize if this has been covered - 

There is more material than you think before you hit the core, certainly enough to change the ski and make it act completely different. And if you're like me and you sand into the core sometimes, just soak it with epoxy and keep going.  Ignore anyone who tells you not to modify your ski. Take it from someone who has been modifying skis for a long time...everyone thinks you're crazy when you do it, that's just part of the deal. 

I'll give one warning: almost every ski I've ever modified the bevels on has ended up trash. This is because if I make a change and it's better, I'll inevitably keep sanding to try and make it better-er...until I go to far and it starts to really suck. That's just part of the process though, enjoy!

[swbca]

3 hours ago, AdamCord said:

@swbca I haven't read this whole thread so I apologize if this has been covered - 

There is more material than you think before you hit the core, certainly enough to change the ski and make it act completely different. And if you're like me and you sand into the core sometimes, just soak it with epoxy and keep going.  Ignore anyone who tells you not to modify your ski. Take it from someone who has been modifying skis for a long time...everyone thinks you're crazy when you do it, that's just part of the deal. 

I'll give one warning: almost every ski I've ever modified the bevels on has ended up trash. This is because if I make a change and it's better, I'll inevitably keep sanding to try and make it better-er...until I go to far and it starts to really suck. That's just part of the process though, enjoy!

The method of adding material I described above has allowed me to make it better and worse, then better again 20 times on the same ski.  Just have to stop screwing around when it happens to be better a week before your most important tournament.

I can see that method wouldn't give you right shapes on a Denali ski because of the larger radius bevels.

What I am doing with the D3 is just a learning experiment.  It's on deck to be used as ski for weekend guests.

 

Edited January 5 by swbca

[Horton]

@swbca if you don't like the way I administrate this site, may I suggest Facebook?

[swbca]

2 minutes ago, Horton said:

@swbca if you don't like the way I administrate this site, may I suggest Facebook?

In don't know what your are talking about.  Last week I said its your dedicated attention that makes BOS great.  Was I not supposed to address your comments about modifying bevel sizes ??

[VONMAN]

Holy Smoke! As if boot placement and fin adjustments wasn't enough! I remember having a conversation with Will Bush many years ago and decided to let the ski designers to do their thing. Over the years I've found some articles on it but it seemed like bat wings and mirrors at least to me.

@swbca Sounds like a cool project, keep use updated and good luck.

@DWAbout that box with a light to measure angle. Your Serious?

The only time I've seen someone sanding a ski was at the club about 11 years ago. He was in the lake with a Goode 9100 sanding the whole ski bottom to take out all of the scratches. When done he proudly held up ski to show me. I just shook my head in disbelief. They walk among us.

[swbca]

21 hours ago, DW said:

Nice idea, is it mounted to the gunnel?  I have seen posts where the side of the boat was striped (by line color) as a width marker.  My ski partner has a box mounted on the pylon that turns on a light at the correct angle.  The next addition is to add the time element so one ski's at the correct frequency & width when absent of buoy's.

Your partner's system would be marketable and the timing element that would a great addition.  Skiing wide enough is only part of the equation. 

A question about your partners device.   At short line the rope is always blown back by the wind when the skier is wide and the rope a slightly slack. (look at the photo of the skier about 5 post up from this post) How does the device know where the skier is when the rope is angled back an arbitrary amount. 

Used 1" OD PVC pipe.  Don't know what its called there is a PCV elbow that has screw holes in one direction.  Screwed that to the carpeted face of the side pockets about 2" above the floor.  Then PVC pipe up to a few inches below the side deck of the boat.   The blue float fits snug on the pvc. 

I have used tape markers as well, but I wanted something that would show in the videos.  I don't care for wide angle video so I needed to have some height on the markers to get them in the video frame.

Edited January 6 by swbca

[DW]

@VONMAN - Yes, we have used it a few times.  The challenge we are having is getting the software person to act in a timely manner so lots of delays.

@swbca - thx, it is clearly a prototype thing right now, somewhat cumbersome and heavy and potentially fragile if not careful.  You hit on another challenge, having it be accurate per your rope 'slack' effect.  More of our playing with it has been with intermediate skiers and trying to show them how wide one actually has to be to make a buoy.  The knowledge is simply an angle relative to the pylon, the system turns on a light when the angle has been achieved, each angle is programmed in to the software so when rope length is changed, you set the angle on the device.

It turns on a light, the first attempt was a white light, no good, way too hard to see depending on sunshine.  Red light is better.  We will keep tinkering.  We can integrate a timer, the key is what to make it do, for instance steady light (good), blinking light (sorry buddy, you just missed that buoy:-).  Another thing about the light, there is a time delay to when you as a human acknowledge it which means you may not really be on time.  Also, the first time you trigger the light, you are technically behind if you are not changing direction by then.  My buddy loves to tinker with stuff and create 'relatively useless' things so we are having some fun with it. 

And to JTH, please don't give me the Eric Lee award for crazy ideas 🤣

 

Edited January 6 by DW

[VONMAN]

@DW Sounds cool! It could be a good for training a beginner in achieving width and timing before getting into course. I like where ski partner is going with this. Build a good foundation before crashing into buoy's.

[swbca]

@DW

Does anyone know if the white fibers closest to the bottom ski surface in this D3 ski are structural ?   

A more theoretical question . . If an edge tuning strategy damages the tensile strength of 20% of the carbon fiber between the fin and rear foot,  is that going to make any difference for a 165# M9 skier ?

Freddy Winter broke his D3 (on WTBC) behind his rear foot but the forces he creates on the ski are a high multiple by comparison and also has had a high multiple of flex events.

EDIT  Drilled an inspection hole adjacent to the fin block and 1" from the edge of the ski using a countersink bit.

The bottom of the ski is made of 1.5mm black resin and 1.5mm of the white fiber you see in photo above.  I looked at it 5" ahead of tail.   I can't know if there is a different layup further ahead on the ski where there would be more stress.

Edited January 8 by swbca

[scoke]

This has "THREAD OF THE YEAR POTENTIAL" and delivers!

Too bad the OP won't be sharing video of what is to come. Unless he will?!

 

[DW]

@swbca - My thought on the white ribbons, could be a form of safety strap, carbon is brittle so the potential of a fracture exists, the two cords running lengthwise may simply be to keep two halves together in the event of a fracture.

[skialex]

 

12 minutes ago, DW said:

@swbca - My thought on the white ribbons, could be a form of safety strap, carbon is brittle so the potential of a fracture exists, the two cords running lengthwise may simply be to keep two halves together in the event of a fracture.

@DW read your post and went to my workshop to check 2  D3s broken from transport, one at the middle and one at back just in front of the fin slot. 
Didn’t see any white ribbons, looking at the gap of the broken at about the middle ski.

The other one, broken just in front of the fin slot, I see some white at the gap, at bevels, could be something like white ribbons, but definitely doesn’t seem it did any difference at the brake. It’s a clean brake…

 

[Horton]

there is a non-structural white plastic layer between the graphic on the outside and the structural carbon on the inside. that layer is there to make the graphics look brighter. I can't tell if that is what is in the images above but seems likely.

 

[swbca]

10 hours ago, scoke said:

This has "THREAD OF THE YEAR POTENTIAL" and delivers!

Too bad the OP won't be sharing video of what is to come. Unless he will?!

No one wants to watch a video of an M9 skier ski unless its his brother.   32mph just doesn't deliver a great example of good slalom skiing because of the slushy response from the ski.  Like racing on a road track with low tire pressure.  For the participants, exciting competition doesn't depend on the speed, but spectator value drops with the boat speed.

Edited January 9 by swbca

[Octopus_Paxarbolis]

@swbca

You talk a good game. Let us see some video.

[swbca]

20 hours ago, Octopus_Paxarbolis said:

@swbca

You talk a good game. Let us see some video.

Relax - no one is water skiing in Minnesota til May 2024.   

and @scoke

More important . . Who is the skier with the highest visibility on this forum and often posts videos of himself skiing when reviewing new skis ??

Its @Horton   When my videos look as good as his, I will post a video.  With his superb skills and several decades of age difference that well never happen.   But I will keep having fun working on ways to ski better by any and every means possible until I can't.

That will include following @AdamCord advise to ignore everyone who says your crazy for modifying the shape of your skis.

Edited January 9 by swbca

[Sethro]

21 hours ago, swbca said:

 32mph just doesn't deliver a great example of good slalom skiing because of the slushy response from the ski.  

I'm not sure about that...There's a video of Joel Poland just posted on Instagram running 41off at 30mph on a Radar Butterknife.  It's a great example of slalom skiing!  🙂

[swbca]

I was focusing on the observers experience.   If the Pro Slalom events were run at 30 or 32 mph it wouldn't be close to the same experience.  Like in most sports its the speed that makes it exciting to an audience that isn't personally related to a competitor.   When I was watching the archive video on youtube of a Nationals a couple of years ago.  The announcers didn't even show up for some of the 32 and 30mph divisions.

[Horton]

Should not hold me up as an example of "Good enough to show video"

I say if you have a lot to say and a lot of strong opinions you should be willing to show what you are talking about. 

[swbca]

1 hour ago, Horton said:

Should not hold me up as an example of "Good enough to show video"

Just sayin I wish I could ski as well as you do.   I know that ship has sailed.       

Edited January 9 by swbca

[Horton]

We all struggle at our own level

[DW]

All I care about is what is learned, perhaps and hopefully something he finds that makes the ski or his skiing better.  Hopefully when the ice melts in July (it is Minnesota after all) those results will be posted rather than having the topic go off the rails.

[GaryJanzig]

Don't mess with anything except the binding placement, and fin/wing settings. The ski designers know what they are doing. Too expensive an item to risk screwing it up. 

[swbca]

I'll check back next summer.   In the meantime I will observe Adam Cord's advise from a couple of days ago on this thread.

"Ignore anyone who tells you not to modify your ski. Take it from someone who has been modifying skis for a long time...everyone thinks you're crazy when you do it, that's just part of the deal"

I have said a few times this is a Hobby experiment on a ski that otherwise had no value to me and has virtually no value on Ski It Again.

Edited January 13 by swbca

[eleeski]

Cutting up skis to modify them to your tastes is fun! Maybe expensive and a bit risky but you will learn a lot. Both about ski design and making your skills improve.

Do consider modifications to the top edge. 

Just to make your experiment more complex, edges can be quite different from front to back to optimize performance.

FWIW, I build and modify my own skis.

Have fun!

Eric

[ForrestGump]

If there is one person you should ignore, it's definitely that eleeski cat.  He's loony as the day is long.  

[Kevin89MC]

I love that you're doing this, and can't wait to hear more about the results! As a fellow Minnesotan I also feel the need to keep occupied in the winter months. I have a very long list of things I need (and get) to do, so unfortunately ski adjusting will never be in my foreseeable future. But as an engineer I totally get the desire. With the expected "warm" temps coming soon, maybe a few lakes will open up and you can try some ideas out! 🙂

Good luck in your pursuits!

Kevin

[Horton]

Back off @ForrestGump giving @eleeski a hard time is my job.

[Adam Caldwell]

I think more people should get out the file and play with a ski.  Like @AdamCord said. It can be a slippery slope, but learning things is what fun.  I think I would have been done with this sport a long time ago if it wasn't for exploring what filing, splitting, or adding bondo on a ski can do. Its all part of the fun and part of the challenge.  Plus if it doesn't work. you at least have a good excuse for the day.   

Plus, the more skis that get filed on, the more that get destroyed,  and the more people will need new skis!

If anyone knows of some young guys who are curious to play with this stuff, send them my way!  

[skibrain]

When I was 13, my dad picked up a pair of Nash brand wood combos for $15.  Said “TUNNEL CONCAVE” right on the bottom, calling attention to the shallow recess milled out of the center. As my brother and I were both slaloming, older bro got the ski with rear toe.  My dad had the brilliant idea of “cutting down” the second ski from full 68” Using a jig saw to remove 3” off the tip and 3” off the tail. Looked about right to pops.  He added a rear toe and I picked out a 3” deep metal fin. Barely any curve on tip. No rocker. No bevels. 
 

I tried my best on that thing for the rest of the summer but it was dangerously bad.  

[swbca]

My cutting up, shaving, filling, recoating resins goes back in Water Skiing history to when Warren Witherell gave 3 of us Minnesota Boy's division skiers new Northland Warren Witherell signature slalom skis. Then he proceeded to cut 2"off the back of all of our brand new skis with a carpenters saw a few weeks before the National Tournament.

Stock skis left a lot of room for improvement in the 70'-90's so being able to make them better was a competitive advantage.  I ended up with Regional records and National titles largely because of my endlessly chasing better ski performance.  Still doing it today but modern skis provide a much better starting point. 

-----------------------------------------------------------------------------------------------------------------------------------

My starting point on the last several skis I have worked on is to reduce the size of the bevel by about 30% on the last 18" of the ski and have the bevel meet the bottom of the ski with a very sharp edge. 

The rest will be done by carefully/slightly detuning the sharp bottom edge with on the water testing. If the edge is soften too much, it can be reversed by flat sanding the bottom a few strokes with 600 wet and dry paper glued to a 1x2 wood block.  Very similar to practices used in tuning snow ski edges. 

The irregularities in this photo are reflections.

Edited February 1 by swbca

[scoke]

This thread is inspiring! Don't let the haters slow you down. Keep going!

To get the ski to engage and turn more in the tip, have you considered drilling a few "relief" holes in the forebody front deck? or even in the front side walls? That's a common solution to relieve pressure.

 

It's 2024, all up is down and down is up now. Anything goes!!

 

[Adam Caldwell]

Well I've got one young gun interested in filing on some skis....Any other takers out there? 

[swbca]

Now that I have this ski ready for testing, I see that it looks like a throwback to the 45 degree sharp edged bevel used on KLP's 1970s Maharajah but in this case its only on the last 16" of the ski . . . . leaving the larger radius modern bevels on the rest of the ski.

The purpose of the 45 degree bevel is entirely different than the classic 45 bevel.  Performance adjustments are by modifying the bottom edge from from razor sharp to not quite razor sharp.  You tune the ski by dividing the back 16" into a number of zones and finding the best combination of bottom edge sharpness across all zones.  The logic is parallel to tuning the metal edges on alpine racing skis.  And, like with tuning alpine skis, the adjustments made on the bottom edges of this slalom ski are physically so small you can feel them but can't see them.  Like dragging your thumb crosswise on a knife blade to see if it has the feel of very sharp or not so sharp.  The very sharp bottom edge on the ski assures a straight flow of water away from ski . . . no trace of water wrapping the edge. 

This tuning framework gave me a competitive advantage when tournament skis in the 80's were not great.  I'm Optimistic but not sure how it will work on this D3 EVO which didn't work for me in its stock form.  

 

 

Edited February 25 by swbca

[dvskier]

Will this be the ski that you ride to win the 2024 M9 Nationals?

[swbca]

On 2/22/2024 at 10:20 PM, dvskier said:

Will this be the ski that you ride to win the 2024 M9 Nationals?

Not a chance, but I placed 2nd in a Men3 Nationals on a 66" HO with this same tuning setup with over 50 skiers in the event.  I believe Gordon Rathbun won the event.

Edited February 25 by swbca

[swbca]

On 2/1/2024 at 8:43 AM, scoke said:

To get the ski to engage and turn more in the tip, have you considered drilling a few "relief" holes in the forebody front deck? or even in the front side walls? That's a common solution to relieve pressure.

I've been thinking about the "common solution" you describe above for a month.   

 

 

 

Edited March 4 by swbca

[Horton]

[ForrestGump]

Horton, As soon as my new ski arrives I'm getting out my grinder and a drill.  New skis have warranties, right?

[eleeski]

Since I have infinite Pandas, I am allowed to drill holes.

The hole drilled in the back of my slalom ski just put up an annoying stream of spray, the ones in the front did nothing and there wasn't enough room for holes in the binding area. I don't put holes in my ski now.

The hole I drilled in the bottom of the boat was quite successful at softening the slalom wake of the old Mastercraft but it sucked air into the propwash - so a different effect.

Eric

[Ski2000]

@eleeski
The hole I drilled in the bottom of the boat was quite successful at softening the slalom wake of the old Mastercraft but it sucked air into the propwash - so a different effect.

 

I must admit I am thoroughly confused, and more than a little curious about this part. 
Perhaps I am missing nuance or sarcasm. Either way I want see it if it’s real. 

[eleeski]

Absolutely real. 2004 MC Prostar with a wake that Nautique skiers complained about. I drilled a hole near the prop with a tube extending above the waterline. Softened up the propwash noticeably. The picky skiers loved it. The boat would cavitate a little on high power starts but the skier didn't notice. PP Classic mode showed an improvement in efficiency (faster times with the "Bubbler" open vs capped). We ran it for a few years with the Bubbler. I'll get a picture next time I get to the lake.

The holes in the ski were real too - they didn't work so no pictures of skis.

Eric

[DW]

@eleeski - In some corners of this site you have been missed 😆.  Horton may not agree & the newbies have no idea why but the out of the box discussions were always fun, insightful, maybe even frightening but never boring.

[swbca]

20 hours ago, eleeski said:

Absolutely real. 2004 MC Prostar with a wake that Nautique skiers complained about. I drilled a hole near the prop with a tube extending above the waterline. Softened up the propwash noticeably. 

I drilled a hole near the prop with a tube extending above the waterline.
Please explain this.  Any hole drilled -in the hull- near the prop would be a hole below or behind the fuel tank.   I have no plans to copy your idea, but curious about what you did.     I knocked down the prop wash on a 2004 ProStar with a replica of the Nautique Hydrogate.    I quit using it because was a waste of fuel.

[eleeski]

I'll get pictures. I was surprised how well it worked. And the PP indicated better efficiency. Didn't work well enough to keep MC from changing the hull (and obsoleting one of the best trick wakes).

Sometimes tinkering does work.

Eric

[eleeski]

Extreme edge modification. 

[thager]

Doubles as a Cricket bat!