Stiffness in Slalom course skis? Is more better? Making a few prototypes soon.....

[kurtis500]

I have a basic question about slalom course skis. I have little expereince with them since I grew up on Andy Clarks and Maherajah skis and still use them a lot today. I'm going to be making some carbon (maybe with glass) prepreg prototype skis for recreational use cut-n-jump style skis but wanted to know about stiffeness for the slalom course since you guys lean on them pretty hard. With that said:

 

1- is stiffness king? I can understand on a slalom course where stiffness can really help turning towards the next buoy. But is there too much?

2- Does flex in the ski need to be at a certain level? Is flex good/bad in the X or Y or both? Front to back flex or bending along the centerline? Or a good balance is best?

3- Are sharper edges on the bottom better or is a more gentle radius preferred. This would be the radiuses on the sides (outside edges) of the ski and where the tunnel transitions to a flat surface.

 

The purpose of this effort is to demonstrate some new composite curing technologies. Since Im in charge I get to pick the first protoype product :)

 

Thanks for any input you may have

 

 

[Horton]

Is suspension important to a car? Is nutrition important to an athlete? are ingredients important when baking?

[Horton]

@kurtis500 read this

https://www.ballofspray.com/forum#/discussion/15891/lets-talk-about-flex/p1

[kurtis500]

Thank you Horton

 

[Jordan]

An interesting point to consider. The D3 Ion comes in two flexes. Regular and soft.

There are a significant number of high end skiers on the soft version.

At the Malibu open, Sean Hunter, Charlie Ross were on the Blue soft version. Also Nate skis on a soft with the red graphics.

Freddie Winter was on the regular one.

 

So, I wouldn't say that stiffness is king at all.

[MichaelGoodman]

When the ski is done make sure you post video of

the test run.

[Horton]

@Jordan the difference between the stiff and soft versions of that ski is only a few pounds

[kurtis500]

I'll be happy to post a pic when done. :) Ive ran a couple test shells off the mold including a gelcoat carbon shell. Again, this ski is more of a cut-n-jump style and not really a slalom course. But it should be intersting anyways. Like any part there will be lessons to learn.

[MattP]

@kurtis500 not exactly what you are more than likely doing but this is a great thread. https://www.ballofspray.com/forum#/discussion/12147/the-how-to-build-a-water-ski-at-home-thread

[DW]

@kurtis500 - Stiffness is very important, it is a key parameter in performance along with several others. In this context, stiffness is the amount at any given point on the ski which will allow the ski to perform at its best. As noted, many top athletes perform best on the 'less stiff' version of the model of ski they use. Note ski flex data that is published by the mfg and would be great data for you to peruse as you work through your project.

[RGilmore]

Addressing your question 3, bevel configuration is also very important to how a ski performs. Sharp bevels create lift at the edge and "soft" rounded bevels allow the ski edge to ride deeper in the water. Sharp bevels contribute to speed, due to less drag, while round bevels contribute to "grip" on the water, again due to riding deeper. And that's just on the bottom edges; some ski companies, like Connelly for example, have also been experimenting with variable bevel shapes on the TOP edge of their skis.

 

Most skis have a combination of bevel configurations over the length of the ski, allowing the ski to perform differently depending on how it is being ridden - e.g., weight forward vs. weight back. Like flex, bevel design is a real science/art skill, and is not something you're going to get down with a few forum Q&A's.

[kurtis500]

DW, I did look over that thread earlier. I thought the approach was well done and some of the issues along the way are typical. Its amazing what can be done with gelcoat and fiberglass/carbon and some creative skill. Its still my favorite method of making composite molds and parts. A nicely done gelcoat surface is way more attractive and durable than a printed sheet as a topcoat. hand layup, RTM, vac bag and even prepregs can be cured on gelcoat fiberglass molds.

[kurtis500]

RGilmore, the sharper outter edges are a change I made already to the mold specifically to lift the ski out of the water while keeping the rocker the same. The inner edge of the tunnel seems like a place for a sharper edge. Im sure someone has tried that, or putting a strake under there somewhere. Maybe that kind of grip isnt needed with the other factors.. These are expensive changes to make to a mold anyways. The ski Im building is not for a slalom course but the skis likely share similarities.