Do materials matter?

[Horton]

I am currently having an off line conversation with a Baller who is trying to decide what ski to buy. He has narrowed his choice to the brand and shape but he is confused about materials.

 

My 2 cents is as follows but there are plenty of Ballers who are engineers who can give even better answers.

 

Generally when a ski company makes multiple versions of the same ski but with different materials the “static” flex is about the same. The biggest differences are how fast the ski rebounds and the weight of the ski.

 

In my experience a heavier / lower spec skis may feel better from the wakes to the ball but never feel as good from the ball to the wakes. Unless the cost is out of your range I always tell skiers to get the highest spec version on a ski. No one regrets getting the all carbon & lightest core version of any ski (until their wife sees the credit card bill).

 

[DW]

Yes, different materials have different properties, so a same shape ski made with alternate materials will perform differently. Agree with your comments. Static flex numbers are different from dynamic response characteristics.

[eleeski]

What is Innegra? I've played with soft resins that did something like that. But couldn't make it work for the boot I was trying to mold. Cool stuff in the video.

 

Stiffer and lighter works best for a ski. Flex matters if the rocker is messed up, otherwise go with the rocking rocker as stiff and light as possible.

 

Eric

[vtmecheng]

I'll come forward as the baller that was having the conversation. I'm also a mechanical engineer who specializes in dynamic responses to shock loads. Totally agree that a structure will respond to static and dynamic loads differently. Shock inputs, like wake crossings or even in the turn when the ski chatters a bit, will cause the ski to vibrate. If those vibrations hit a natural frequency of the ski then it can become excited without sufficient damping, which I'm speculating would not be great for tracking or how the water flows under (I haven't worked with fluids since college so take that for what it's worth). All that said, how the ski responds is going to be a combination of the outer layers and the core. How these layers work together will change bending strength, elasticity, natural frequency, damping, etc. I imagine ski design isn't easy and requires a lot of trial and error to get a really good result. Look at the current Carbon V versus the previous model. @Horton didn't like the previous version but with slightly less carbon in the new one he seems to like it more.

 

None of this really matters to the consumer though, we just care that it works through the course at our desired speed and length ranges. The mid range skis are hard both for someone like @Horton to classify and a newbie like me to figure out. Take the Radar Senate line. The Alloy is capable of getting down the course and would be ok for someone new but how much better is the Graphite? Is that performance increase worth the extra $$ for someone new to the course? Same question can be asked of the V and Omni lines. It also doesn't help that the companies say the skis are better than they probably are. Connelly says the Carbon V is good from 30 to 36 mph but Horton's review says max is more like 32 off at 34 mph. Sure you can go 36 mph but should probably get a different ski for that. Add to that good reviews throughout a line (like the V and Senate). The Carbon V is said to be "impressive" and V is "a great choice" and "highly recommended." This all adds up to consumer confusion. What's really needed? Who doesn't like saving a few hundred bucks if the result will be similar? If the results are truly different then maybe that's worth the money. I think this is why there are so many "what ski should I buy" threads for the mid range.

 

Sorry for the long post.

[BraceMaker]

@eleeski oriented strand HD polypropylene. Ie woven carpet fiber fabric. So tough but select your resin carefully. Its more of a canoe material so your $$$ carbon canoe doesn't crack

[vtmecheng]

Here's a decent video describing the structural differences of carbon fiber and fiberglass.

[6balls]

@vtmecheng as a data based guy...a relation to medicine. Drug reps used to show us how the new drug (a replacement to the drug where they just lost patent) was a controlled release and thus superior to the prior drug. Often times, though, there was no difference in the clinical efficacy treating the condition in question.

My thought is certainly materials have different properties...but do they ski better wrapped into their particular design? I remember when GOODE was first on carbon fiber holy crap those skis were light. That was great and all but were they great because they were light? Dunno. The KD's and D3's I ran at the time were pretty good, too, and they were not so light. My Razor was light...skied really well.

My point being that tracing materials to actual performance vs. shape is an interesting one. Seems to me magic is probably both shape and materials, difficult to hit just right, and if it were easy everyone (the ski companies) would have it figured out by now.

[tap]

My opinion, assuming the shape is identical you're pretty much just paying for flex and weight, or lack thereof. It's pretty difficult to take the exact same shape, swap out carbon for glass and still end up with the same flex. The only way to actually make that work is to add a fair bit of thickness to the ski, and therefore no longer the same shape. Shape is primary, flex is secondary, light weight is a distant third slightly above graphics, nice to have but not critical, within reason of course. So, if shape and flex are truly the same, save some money. But if you can get a better flex pattern for a few extra bucks and drop a couple ounces as an extra bonus then probably worth the extra cash. Flex = shape under load, very important. As a side note, there is much much more to laminate design other than fiber selection... far too complex for a late night internet post.

 

@Horton "rebound rate"... you should consider a self administered panda. I'll do the math for you sometime if I really get bored.

 

@vtmecheng the strain rate dependicies you typically see in a shock analysis don't really apply here, the effects are negligible, it's very reasonable to just assume linear elastic behavior. I almost never say this, but I think you're over thinking it... this coming from a guy who has strain gauges glued to his ski. Just buy the better ski and don't look back.

[RichardDoane]

@tap like @Horton would ever give himself a panda @vtmecheng go with a Radar product, you'll be glad you did

[sunvalleylaw]

The snow skis I run (Head) use something called Graphene, which is very light, and very strong. Head is making some light, damp feeling (they are heads after all) skis using the material. It would be very interesting, I think, to see it incorporated into waterskis. https://www.scientificamerican.com/article/graphene-looking-beyond-the-hype/

 

Beyond that, I agree with getting the best built ski you can afford, especially if you want to improve a score in the course. Even at my comparatively pedestrian level.

[eleeski]

@vtmecheng The water is pretty good at damping things at any of the speeds we ski at. Rebound is realistically not a factor in reasonably smooth water. Ski design is complex. Materials are important but just one factor. I've found that the stiffer the better for my skis - if the measure is top buoy count. For consistency, slightly softer and heavier worked a bit better - but my top scores were higher on the stiff light ski. I'll take the heavy glass ski in the choppy rollers but for the glass run behind the best driver, light and stiff.

 

The numbers in the video aren't the numbers I've learned or experienced in the real world of building skis. It is application dependent. Carbon has been a much better material in a finished layup, weight and appearance wise for me. Boron is even better - but way more expensive (and awful to work with).

 

Years ago, I got to ski a System 8 and a Monza. Same mold, different materials and weight. I liked the Monza (light carbon). The System 8 (glass and noticeably heavier) felt bad and my buoy count was way off. Buy the best ski.

 

@tap actually, shape is below or weight in my experience (and I've done some serious grinding/shaping on my skis). Rocker rules. Tuning (binding placement, edges and fin settings) can also be more critical.

 

@RichardDoane The Radar Pro Build I rode a couple weeks ago was lighter than my ski! Nice ski! But not magic for me. The one I rode was too big for me - not a fair test? Cool ski for sure.

 

Eric

[andjules]

One nuance that's beginning to make this conversation even harder: carbon fiber's falling costs and wide availability in different weights and weaves.

 

It's no longer just expensive, high-end carbon vs regular glass. There is a variety of carbon and some weights/weaves are becoming cheap enough that manufacturers (skis and other industries) are replacing glass.

 

Radar's 2018 Senate lower-end "alloy" version is "all-carbon" lay-up... but almost certainly not the same layup (stiffness) as the lithium version.

 

I'd love to see a blind test (no graphics) of a range of skiers trying their hardest pass on Radar's probuild/lithium/graphite/alloy Vapors and Senates. I'd love to know to what extent the marketing speak lines up with the performance of all these material/layup variations.

[AdamCord]

I don't have time for a long post on this so I will just say this:

 

I have been building slalom skis for a decade, and I still call @tap when I have a question about composites. This is what he does.

[vtmecheng]

First off, @tap I love that you have strain gauges on your ski. Can we get some plots of the recorded data?

 

I haven't had much experience with composites, most of what I do is with high end steels and aluminum. I know there are different levels of both fiberglass and carbon (military gets the a lot of the best carbon), including weave designs. As for the video, I can't speak to the numbers used by the author but I believe the general ideas are correct. Also, I get that carbon has a high elastic modulus when compared to fiberglass and that stiffness is generally desired for a course ski. Regarding ski damping, I truthfully haven't thought enough about it but my kneejerk is that it will have some influence on ski performance.

 

Regarding the order of importance for a ski (shape, flex, weight), it makes sense considering what it needs to do. There's so much that goes into ski design that I can only imagine the number of iterations it takes to get things to the desired result. Add to that the always present cost.

 

All this aside though, it comes down to what the skier actually needs for a given level and desired use. Someone just free skiing and maybe doing a course twice a year has an easy decision, just get an Radar Alloy Senate or Connelly V level. It's harder for someone just above that, learning the course and wanting to go through the course more often. I think it's easy to recommend the highest class ski but is that bump in price really justified? That price bump is bigger going from a V to Carbon V, about $375. The reviews make things even more confusing. Keeping with the V to Carbon V example, both are said to go into the 34 mph territory. The V was highly recommended by @Horton here as a great choice up to 28 off at 34 mph. I know his latest review of the Carbon V is also glowing but I'm trying to understand if over double the price of a V is really worth it until someone is pushing into 34 mph. I get that the Carbon V is better but is someone going 30-32 mph really going to notice that performance bump? Some here seem to say "no" but others say "yes." I get that buying a Carbon V or Graphite Senate would result in no regrets but would a newer to the course skier really be bummed with a V or Alloy Senate?

[vtmecheng]

Also, thank you everyone for the great discussion so far. I love this stuff.

[mwetskier]

just remember that no matter how much time you put into learning how the clock works, in the end you're gonna care a lot more often about what time it is.

[SkiJay]

I got to test the 2018 Vapor Pro Build back to back with the 2018 Vapor Graphite. Long story short, the difference was surprisingly small, but still worth paying for if you can afford it.

[Horton]

I argued about this crap over enchiladas and chile verde tonight with Baller / retired Engineer from Boeing. I must have won because he picked up the bill and now I am drinking his beer. : )

[DW]

Right to Horton's wheelhouse of 'flex matters' (from the old CBR fin days), did you ask your Boeing buddy about wing flex? Pretty amazing to watch on a bumpy flight. As an aero guy, I tend to like the wings to stay attached to the tin tube I am riding in.

[JAS]

"More and more about less and less until everything is about nothing". Hats off to Denali for introducing something really different. For me an endless pursuit of finding something that works for me. My metric is simply what ski is funnest to ride. Thanks to all ski companies for your efforts!

[vtmecheng]

Ok but seriously @tap, let's geek out with some strain plots from your ski. Even cooler would be some in-course strain data or, better yet, accelerometer data. I'll even post process it for you if you want.

[pregom]

My analytical side loves discussions like these! From a very practical point of view, I'd like to offer my personal experience. I bought a Radar Senate alloy back in August 2015 when I had barely just learned to do deep water starts on one ski. Since then I worked my way through the course and I developed a very acute case of slalom-itis. I'm still struggling at 15 off. Last month I found a 2016 Radar Vapor Lithium at the right price on ski-it-again and I pulled the trigger. I put a 2018 Vapor Carbitex binding on it (front only, plus normal RTP in the back) and off I went. Our slalom course was already out for the winter, but, just free skiing at 30 to 34 mph, what a difference! Last week I skied on my old Senate - I wanted to see if I could tell the difference. I definitely could! With the Senate I felt I was dragging the ski across the wakes, whereas with the Vapor I feel I am across the wakes without even thinking about it and with a big grin on my face. Of course all this is very un-scientific, just the impressions of a beginner. I was very hesitant to get into a Vapor, especially after reading all the comments from Horton and others about how you learn more quickly on a non-high end ski. So far I'm very happy with my decision. It will be interesting to see how I will do in the course next year.

[TallSkinnyGuy]

The only way to physically test the differences in materials is to be on the exact same shape of ski but made with different materials, like Skijay's experience noted above. I would love to ski the current Radar Senate in all three versions back to back on the same day. The closest I've gotten to that is skiing my '15 Senate Alloy one day and then my new '17 Senate Graphite a few days later. However, these skis are different shapes, so not truly a valid test for this discussion.

 

I found that a much more significant change was going from a relatively soft front boot to a Radar Vapor front boot. It took me at least 5 or 6 sets to get used to the stiffness of the Vapor boot and not be distracted by it anymore. I had the new Vapor boot on my Senate Alloy for a few sets before switching to the '17 Senate Graphite. I wasn't fully accustomed to the new boot by the time I got on the new ski, and I felt like the biggest difference after getting on the new ski was still the new boot.

 

The '17 Senate Graphite definitely felt less damp in the pull-out, but otherwise felt quite similar to my '15 Senate Alloy. I would have gone with the '17 Senate Alloy except that I wanted the adjustable fin and I absolutely love the graphics on the '17 Senate Graphite. For me, the biggest difference in the skis is probably that I think the '15 Alloy graphics are okay but the '17 Graphite graphics are spectacular.

[Horton]

I have had a few experiences with skis of the same shape and theoretically very similar flex and rocker but very different materials.

 

I rode the Radar Strada (all Carbon and PVC) and the Vice (Carbon/Glass and PU). The Vice always seemed better off the second wake to the ball but from the ball back to the wake the Strada was WAY better especially when it was time to get busy.

 

In the case of Connelly I believe that the last gen F1 and the first two generations of Prophecy were all identical shapes and about the same flex. I am sure there were some flex and rocker tweaks.

 

The F1 (Carbon/Glass and PU) was a finicky bear to ride. It was fun at 32 off but I could never run a smooth 35 on one. The first gen Prophecy (Carbon and PU) was way easier to ride. It was faster and just flowed better. The second gen Prophecy (Carbon and PVC) was clearly better again.

 

[Brewski]

From a carbon fiber expert " hell ya materials matter "