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Torsional Stiffness - testing video and analysis

post #1 of 25
Thread Starter 

There have been some discussions of ski flex and how to quantify it for different skis.  While basic bending tests are pretty straightforward, torsion tests are a bit more interesting - so I thought I would share our methods.  There are a couple of methods used by other builders - this is just the one we feel is most comprehensive. 

 

 

There is more analysis of the effects of torsional stiffness in the tech article, but the testing jig/video is the eye-candy!

post #2 of 25

Nice experiment.

When I did something similar I used two different loads and measured deflections of 5 and 10 degrees.

The load is the applied torque in inch pounds.

 

173 Volkl Racetiger

post #3 of 25
Thread Starter 

@dakine , thats really interesting.  We test similar points - various torques between 60 and 180.  Lately I top out at 120.  If your tested length is around 60.5cm (based on some GS ski tests of similar length), the torsional stiffness is a good match for the Racetiger SLs in the video.  Were these GS skis?

post #4 of 25
Quote:
Originally Posted by SandwichTech View Post
 

@dakine , thats really interesting.  We test similar points - various torques between 60 and 180.  Lately I top out at 120.  If your tested length is around 60.5cm (based on some GS ski tests of similar length), the torsional stiffness is a good match for the Racetiger SLs in the video.  Were these GS skis?


Old original orange Racetiger cheater GS 16.4 m skis with Marker rail bindings.

Second from left and still badass.

These things set the standard for what a really grippy, highly cambered cheater ski should be.

post #5 of 25

SandwichTech's video test has two errors that I'd like to point out. I'm not sure if this was intentional or not, but the analysis left out the effects of the area moment of inertia J. A wider ski will deflect less torsionally because of the larger J, but won't necessarily have better edge grip because of wider width increasing the torque the ankle joint must overcome to maintain the critical edge angle needed for carving a turn of a given radius and snow conditions. A meaningful analysis should seek to find which ski has the larger shear modulus G, which would help give a better picture of how the ski will actually perform. It would be more interesting to test skis in the same category since powder skis and cheater SL skis are made for polar opposite uses anyway and have different design requirements accordingly. A SL ski with a smaller turn radius doesn't need as much torsional stiffness to hold an edge as a powder ski or all-mountain ski, so, while as a mechanical engineer I think the test is cool, it is virtually meaningless in its current form.

 

Second, while it is desirable to have a ski be relatively soft longitudinally and stiff laterally, longitudinal stiffness is still somewhat desirable. The stiffer the ski longitudinally, the better it will handle vibrations. So really, you want the stiffest ski possible laterally and the stiffest ski that you can still bend longitudinally.

post #6 of 25
Quote:
Originally Posted by mjp5 View Post
 

SandwichTech's video test has two errors that I'd like to point out. I'm not sure if this was intentional or not, but the analysis left out the effects of the area moment of inertia J. A wider ski will deflect less torsionally because of the larger J, but won't necessarily have better edge grip because of wider width increasing the torque the ankle joint must overcome to maintain the critical edge angle needed for carving a turn of a given radius and snow conditions. A meaningful analysis should seek to find which ski has the larger shear modulus G, which would help give a better picture of how the ski will actually perform. It would be more interesting to test skis in the same category since powder skis and cheater SL skis are made for polar opposite uses anyway and have different design requirements accordingly. A SL ski with a smaller turn radius doesn't need as much torsional stiffness to hold an edge as a powder ski or all-mountain ski, so, while as a mechanical engineer I think the test is cool, it is virtually meaningless in its current form.

 

Second, while it is desirable to have a ski be relatively soft longitudinally and stiff laterally, longitudinal stiffness is still somewhat desirable. The stiffer the ski longitudinally, the better it will handle vibrations. So really, you want the stiffest ski possible laterally and the stiffest ski that you can still bend longitudinally.


Virtually meaningless...WTF.

The tests present raw data, how it is to be interpreted is the point of the discussion.

Armchair engineers with no data or calculations are useless.

 

To state something like;

" A SL ski with a smaller turn radius doesn't need as much torsional stiffness to hold an edge as a powder ski or all-mountain ski, so, while as a mechanical engineer I think the test is cool, it is virtually meaningless in its current form."

 

A powder ski needs more torsional stiffness than a wide tipped slalom ski?.

You need to back this up because I think you are flat wrong.

They operate in different modes, powder being mainly hydrodynamic and SL being mostly edge lock carving.

 

Any data is better than idle speculation.

Maybe you can contribute something to this discussion besides internet snark....maybe.

Give it a better try.

post #7 of 25

So I was always pretty terrible at mechanical engineering but wouldn't a wider ski deflect more?

 

It would take more force to get the ski on edge to overcome the longer lever but once on edge the longer lever now applies more torque to the ski. I assume that is why the torsion bar goes all the way across the ski. 

 

Like I said mechanical engineering is not my forte. 

post #8 of 25
Thread Starter 
Quote:
Originally Posted by mjp5 View Post
 

SandwichTech's video test has two errors that I'd like to point out. I'm not sure if this was intentional or not, but the analysis left out the effects of the area moment of inertia J. A wider ski will deflect less torsionally because of the larger J, but won't necessarily have better edge grip because of wider width increasing the torque the ankle joint must overcome to maintain the critical edge angle needed for carving a turn of a given radius and snow conditions. A meaningful analysis should seek to find which ski has the larger shear modulus G, which would help give a better picture of how the ski will actually perform. It would be more interesting to test skis in the same category since powder skis and cheater SL skis are made for polar opposite uses anyway and have different design requirements accordingly. A SL ski with a smaller turn radius doesn't need as much torsional stiffness to hold an edge as a powder ski or all-mountain ski, so, while as a mechanical engineer I think the test is cool, it is virtually meaningless in its current form.

 

Second, while it is desirable to have a ski be relatively soft longitudinally and stiff laterally, longitudinal stiffness is still somewhat desirable. The stiffer the ski longitudinally, the better it will handle vibrations. So really, you want the stiffest ski possible laterally and the stiffest ski that you can still bend longitudinally.

 

mjp5, glad the video got you thinking...I'll address your questions in reverse order.

 

First, vibrations are much more complex than just "stiffer is better".  Increasing stiffness reduces the amplitude of the vibration, but it also decreases the decay (true damping) and increases frequency.  I do have an intro to ski vibrations article if you want to have a go at that.  Also, going with "the stiffest you can bend" has some definite downsides.  Most obvious, you lose out on the variety of turn shapes that a softer flexing ski has to offer.  

 

Second, I would like to point out that the second ski is a Root 78 - certainly not a powder ski.  Now for the meat of it.  For anyone without an engineering background, torsional rigidity W is a product of the modulus of rigidity G (a material property), and the second moment of area J (a shape property).  So W=G*J.  mjp5 is suggesting that in order to ignore the effect of a slightly wider ski on J, I only look at G, not W.  The problem with ignoring the x-sectional shape is that is that it is extremely important.  Take Volkl's Double Grip: it is essentially an H-beam, placing more core area at the outer edges to increase its J.  This allows Volkl to use traditional fiberglass (lower G) and still have improved torsion.  The Root 78 on the other hand uses specific carbon facings (high G) and a more traditional x-sectional shape.  If we were to look at only G, the Volkl would be at an unfair disadvantage.  It would have been misleading of us.  For an analogy, imagine you have to cross a bridge and have two options.  One is a sheet of aluminum foil, one is an aluminum I-beam.  They both have the same modulus, so what difference does shape/area make?

 

Finally, if you feel the slightly wider (by 8 to 10 mm) ski should have had a proportionally greater torque applied to it - ok.  I could debate this as well, but why bother.  Adding 5mm to each torque arm acting on the Root 78 means that the Root 78 will have a 58% greater torsional stiffness in stead of the 62% (which I rounded to 60) stated in the video.

post #9 of 25
Quote:
Originally Posted by dakine View Post
 


Virtually meaningless...WTF.

 

 

Armchair engineers with no data or calculations are useless.

 

You need to back this up because I think you are flat wrong.

 

Any data is better than idle speculation.

 

Maybe you can contribute something to this discussion besides internet snark....maybe.

 

Give it a better try.

 

 

I suggest that dakine should remove his "ambassador" label until he achieves a modicum of diplomacy.

 

 

_____________________________________________________________________________________

How well you are able to ski is related to how hard you are willing to fall.

post #10 of 25

@ dakine
To clarify my comments about SL vs powder skis: these skis are at opposite ends of the spectrum and have completely different intended uses. However, for any ski working in a given set of conditions trying to make a turn of a given size, having a smaller turn radius reduces the required stiffness to hold an edge. I'm not going to derive this, but essentially it's similar to why it's easier to carve on a modern shaped ski than an old straight ski. Two skis could have otherwise identical construction and be trying to do the exact same thing, but simply building one with a smaller turn radius means that to make a carved turn of a given turn radius, the edge angle required is smaller, thus the skis can deflect more and still maintain the turn.

 

I think you misunderstood me. Torsional stiffness definitely matters more for a SL ski than a powder ski. But this is entirely due to the usage. In slalom racing you want maximum edge grip in the most difficult conditions. In powder skiing, that's not the priority. I was trying to point out that a SL ski can still have better edge grip than a powder ski despite a greater torsional deflection due to things like the effects of a narrower width and a tighter turn radius. I haven't seen enough powder skis to make a generalization about if they would typically deflect more or less than a slalom ski, but I'm sure that a powder ski with anything close to a "race" construction would deflect less than a SL ski with a similar construction.

 

@ lonewolf210
The torque T is proportional to the width of the ski. The area moment of inertia J is proportional to the width squared. The angle of twist phi = (TL)/(JG). L is the distance from the fixed point to the deformed cross-section considered. G is the shear modulus, a property of the materials. Thus wider skis should deflect less than narrower skis for a given torsional load.

 

@ SandwichTech
Yes, it was sloppy to say that stiffer = less vibrations. Vibrations are definitely a lot more complex than that. I'm also happy to see you using the term damping instead of dampening. However, I still think that that's a reasonable heuristic if we assume resonances are avoided, etc. If I had to blindly guess between two otherwise similar skis which one had better vibration characteristics, I'd guess that the stiffer one would perform better. This is actually true with all of the skis that I've personally ever handled. Of course I've heard that for example, Atomic's D2 skis are softer yet damp vibrations better than otherwise comparable skis, due to their unique construction. I haven't had a chance to inspect any D2 skis in person and don't know how true this is one way or the other. My point is just that all else equal, stiffer generally tends to handle vibrations better, even though it's possible to do clever things. And by stiffest you can bend, I meant the stiffest skis you can properly ski, not just bend for one ideal turn or some nonsensical notion.

 

Higher frequency, smaller amplitude vibrations are desirable for a few reasons. The larger the amplitude, the harder it is to maintain properly pressured contact between the edge and the snow. Also, higher frequency vibrations are more readily absorbed and damped by most materials. You have made the assumption that damping is independent of frequency. Thus stiffer improves the transfer function dynamics over most Poincare sections from the Hamiltonian phase space of the system. In practice, the skis never have a chance to damp completely to a motionless state because they are constantly being perturbed, so trying to make the decay faster isn't very effective. Keeping the response amplitude small is a better goal.

 

I did not suggest to look only at G. Moreover, you can't just take the material G value, you need to determine the effective G from the composite structure (and if you want to do some engineering with this you really need the full blown orthotropic stiffness matrix). Rather, I wanted to point out that you need to look at more parameters than just phi before you can make claims about which ski will have better edge grip. G is just something I'd personally try to get from the test as a fun thing to do, but that's no where near enough to make the claims you made in your marketing video. Adding 5mm to each end of the torque arm does not properly account for the effects of a greater width. It should be 50mm longer on each end (100mm total, very roughly). This is a moot point however since as I talked about above, a torsion test won't tell you what you're trying to figure out. I really do think that the idea of a ski with legitimate use of carbon fiber and not just stringers or veneer could work great, but the video test is not grounds to have even the slightest cogency for the hypothesis of it having better edge grip than a slalom ski.

post #11 of 25

mjp5 ...that's a bit more constructive technically.

My professorial side tends to state things in a way that gets attention.

 

As you realize, a ski is a very complex shape made of at least ten materials.

Even if you had complete mechanical properties data on all the components and CAD drawings of the shape I doubt you could compute the flex properties of the ski without it being a major project requiring finite element software and a small supercomputer.

I don't think ski manufacturers have this capability.

(Maybe someone knows better but they sure don't publish)

The fact that Sandwich Tech and I are actually generating some data is much more interesting than theoretical speculation or skier impressions regarding stiffness or torsional rigidity.

 

Have you looked at this thread?

http://www.epicski.com/t/119302/some-ski-stiffness-data-wtf

 

You seem to be a sincere ME student eager to show off your knowledge of engineering mechanics 101.

I'm a crusty old PhD engineer with a 30 year career and 27 US patents.

Without data and detailed computation most technical speculation is not very useful.

Also, If you really want to contribute to this thread you should read this Swiss thesis on carved turn mechanics.

http://e-collection.library.ethz.ch/eserv/eth:28070/eth-28070-02.pdf

An engineer that doesn't read the literature will eventually make a big mistake.

The subject I am now pursuing is how snow elasticity affects energy storage in a bent ski..

Snow turns out to be incredibly complicated mechanically and (as all skiers know) really affects ski performance.

 

As Sherlock said "always get the facts first, otherwise your mind will inevitably twist the facts to fit your suppositions."

 

 As for Crudmaster....You are not an engineer and clearly don't recognize an invitation to a technical shitfight of the productive kind.

Self righteousness is not a moral virtue.

post #12 of 25
Thread Starter 

@mjp5 I think we have found some common ground!  I also cringe at the use of “dampening” (check out the first line from the article I linked to) and have a lack of appreciation for carbon used as “pop stringers”.  I do not assume that damping is independent of frequency, I just stop at a certain degree of complication for our tech articles.  Our Micro-Mechanical Damper is designed to attenuate 3rd mode vibrations between 70 and 120 Hz.  I agree that high frequency vibrations are desirable for a lively ski, which is why I disagree with the use of full sheets of rubber.

 

I do not say that one ski has better edge grip than the other.  What I do say is that there are many great torsion technologies out there (I mention three others, but there are many more) and since there are so many good choices, there is no reason to go without a ski with torsional improvements.  What would I hypothesize after the test?  The Racetiger is probably more forgiving and the Root 78 probably has a higher top end speed.  However, I say neither and the viewer is free to draw their own conclusions because this is just a torsion test video.  The point of the video is…to test torsion.

 

On to the technical (wa-hoo):  I didn’t just look at phi, but I think you know this and just got carried away.  Determining an effective G would mean looking at only one x-section down the length tested.  In my first post I said that we like this method because it is the most comprehensive; looking at the shear modulus of one x-section is not very comprehensive.  What we are looking at is the torque and length needed to twist the ski a degree.  This means that, to some degree (da-da-ching), the results can be compared from ski to ski and length to length.  It is worth pointing out that this is not “my test.”  It is a method published originally (to the best of my knowledge) in 2007 by Laboratory of Technology – Composites and Polymers partnered with Institute for Snow and Avalanche Research in Davos, Switzerland. 

 

This is an image from a test done at RMIT Australia, who referenced learning of it from Journal of Sports Engineering.

 

 

Anyway, I can fully appreciate approaching engineering claims with a degree (I can’t stop) of skepticism…but don’t make the mistake of thinking nobody else does their research.

post #13 of 25

@ lonewolf210

The torque T is proportional to the width of the ski. The area moment of inertia J is proportional to the width squared. The angle of twist phi = (TL)/(JG). L is the distance from the fixed point to the deformed cross-section considered. G is the shear modulus, a property of the materials. Thus wider skis should deflect less than narrower skis for a given torsional load.



 




O that gave me flashbacks to the nightmare that was my deformations class. It's that sneaky J that always screws me up.
post #14 of 25

Thanks for the lively discussion folks....and initial post by Matt at SandwichTech!

 

We talk to lots of ski builders with varying degrees of mechanical engineering and physics prowess, and they all say ski behavior is intensely difficult to model, much less measure...even aspects as seemingly simple as torsional stiffness can set people off into deep dark discussions for days on end.

 

The measurement of a ski's characteristics and response to stimuli administered and observed in various ways on a test bench is hard enough to nail down, but add in the mix of moving the ski along an undulating surface of varying densities and angles with different pressures delivered from above and below along its length when run flat or tipped at an angle while flexing longitudinally and horizontally as it travels down a slope of varying angles.....instant headache for us mere mortals....I am glad you smart guys are capable of figuring it out....:)

 

For those who are interested, we managed to Meet Matt and Katie squeeze a few testing days on the current version of the SandwichTech Root88 ski here in Vermont on some truly perfect, high-speed carving surface days.  We are working on the draft review, but I can tell you from personal experience Matt and Katie's Root88 is a superbly crafted racecarver with a stunningly stable and strong chassis.  SandwichTech is passionate (obsessed?) about their product's performance and quality, and skiers should expect to see these skis appearing all over the place in the coming seasons.  We were very, very impressed with their current version of their 88mm waisted ski.  Stay tuned for more...

 

Some pics:


SandwichTech Root88 Sidewall -(Ipe wood)

 

 

post #15 of 25

Very interesting discussion. @SandwichTech  has done a clever job with his measurement device. How much weight did you use? (Elegant potential adjustment for different widths by changing the arm length.) Certainly more useful than the old "hold the center and twist the tip" measurement.

 

Still, I wonder if there is a diminishing return for torsional stiffness. Obviously a noodle will not edge and a noodle will twist and even cause uncommanded turns in powder. Too soft is all bad. But in all the pictures of bent race skis none were twisting torsionally. I haven't seen visible twisting when looking at any of the skis I ride. 5cm is not much lever arm to induce twisting - and that's from the centerline of a powder ski not the boot edge (are some boots wider than a narrow ski?). In an aggressive turning ski angle of say 30 degrees will a couple degree washout really cause a loss of edge hold?

 

Perhaps a clever designer could engineer a ski to twist more edge angle when the ski is bent. (Wouldn't an oval shaped cross section flatten or widen when bent? Attach that to the top of the sidewall and there would be pressure to increase the edge angle.) Clever uses of composites should make that buildable.

 

@dakine We got to the moon with slide rules and TLAR (that looks about right). Finite element analysis is not the only way to get something built. GIGO happens when all the parameters are not right. In a product like skis (which have a huge subjective component) the variables of snow condition, steepness of the hill and skiing style make a too analytical and data based approach inappropriate. A good feel from an "armchair engineer" may be more valuable. Of course, the "armchair engineer" can use data for some pretty silly claims as well. As long as the data gathering is fun, right on. And thank you for your data from the  http://www.epicski.com/t/119302/some-ski-stiffness-data-wtf  thread - it drove a fun and productive experiment with my Race Tigers. (I'm not sure if you are a professional ski designer or an "armchair engineer" - either way I enjoyed your work. As I'm enjoying this thread).

 

Of course I believe that "ski bending causes a carve" is a myth so what do I know?

 

Eric

post #16 of 25

Stiffness and damping have to go hand in hand to produce a useable product.

Just about every sport has gone through a too stiff, not enough damping phase resulting in equipment that works horribly.

Honda, hardly a company without analytical resources, still builds several chassis for its Moto GP bikes with differing stiffness and tests them to find their race bike.

Finding a balance of properties is what engineering is about.

One advantage the old ski companies like Kastle or Atomic have is lots and lots of experience.

They may not know why something works but they know thousands of things that don't work.

Edison never considered a bad experiment a failure.....

.....He just learned one more thing that doesn't work.

 

Slide rules huh?

The favorite in my collection is this 22 incher with special scales for solving radiation problems.

A Post Versalog got me through undergrad then I switched to a HP 35 calculator and got caught up in the dark side of engineering.

The HP 35 will work with a new battery, the slide rules will work forever.

I still use an old circular slide rule to compute gas mileage when I fill up.

Folks that see me think it is black magic when I say 21.2 mpg.

 

post #17 of 25

@dakine Slide rules and HP. Nice.  Yes I had a slide rule and still do, also had a circular one (may still have it somewhere)>  HP 33e, HP33c HP41, HP41cx and lately i41cx+ on the iPhone looks like the cx plus a whole lot more.

 

@SandwichTech Nice video and skis.  If I might suggest that the test be done with the ski base up and only loaded from one side as this could possibly better define the stiffness and performance when comparing skis as it would be closer to real world type loading.  Also measure lateral off axis deflection under this loading.  Loaded equally from both sides could mask some details.  

post #18 of 25

Beautiful sidewall photo.

Great skis!

http://youtu.be/bXwGPEjV5YM

post #19 of 25
Quote:
Originally Posted by dakine View Post
 

Stiffness and damping have to go hand in hand to produce a useable product.

Just about every sport has gone through a too stiff, not enough damping phase resulting in equipment that works horribly.

Honda, hardly a company without analytical resources, still builds several chassis for its Moto GP bikes with differing stiffness and tests them to find their race bike.

Finding a balance of properties is what engineering is about.

One advantage the old ski companies like Kastle or Atomic have is lots and lots of experience.

They may not know why something works but they know thousands of things that don't work.

Edison never considered a bad experiment a failure.....

.....He just learned one more thing that doesn't work.

 

Slide rules huh?

The favorite in my collection is this 22 incher with special scales for solving radiation problems.

A Post Versalog got me through undergrad then I switched to a HP 35 calculator and got caught up in the dark side of engineering.

The HP 35 will work with a new battery, the slide rules will work forever.

I still use an old circular slide rule to compute gas mileage when I fill up.

Folks that see me think it is black magic when I say 21.2 mpg.

 

 

 

 

Haha NASA also does the same thing. I did a literature review on carbon-phenolic nozzle construction as part of a project and pretty much all the papers analyzing construction methods basically all ended with the same conclusion. "We have no idea how this method was arrived at but it's worked for 20 years so well just keep using it"

post #20 of 25
Thread Starter 
Quote:
Originally Posted by oldschoolskier View Post

 

@SandwichTech Nice video and skis.  If I might suggest that the test be done with the ski base up and only loaded from one side as this could possibly better define the stiffness and performance when comparing skis as it would be closer to real world type loading.  Also measure lateral off axis deflection under this loading.  Loaded equally from both sides could mask some details.  

 

@oldschoolskier Thanks, I am glad you enjoyed it.  The reason opposite torques are applied to each side of the ski is to isolate the deflection to only twisting - no bending.  If you were to hang only one of the two weights, the ski would both twist toward the weighted side and bend down the length of the ski.  This means that a difference in bending stiffness would skew the results for torsion comparison.  Luckily, most sandwich style skis have a symmetical layup, so twisting behavior is nearly identical in either direction.

 

@Speed! That is some great footage!  I just embedded it on our site - thanks.

post #21 of 25
Quote:
Originally Posted by ExoticSkis View Post

 


SandwichTech Root88 Sidewall -(Ipe wood)

 

Why the Ipe Wood sidewall? Is it part of the core?

Can't say I'm a fan of it on either aesthetic or practical grounds.

post #22 of 25
Thread Starter 

@Tog The Ipe offers a few key benefits that made us choose it.  First it has a much higher modulus than UHMW or ABS which makes for added torsional stiffness and edge-compression strength.  From a reliability standpoint, Ipe (or any wood) is going to bond to your core and composite facings much better than you will ever get from UHMW or ABS (a typical starting point for delamination on other skis).  Finally, compared to bamboo or oak or black locust (wood sidewalls used by other indie brands), Ipe is naturally waterproof.  Ipe decking is rated for 75+ years.  As far as performance and reliability, I would choose phenol as a close second, but because of brittleness we chose Ipe.  Aesthetics are personal preference.  I personally don't care for the look of wood topsheets, but going with ironwood sidewalls was a utilitarian choice.

post #23 of 25
Quote:
Originally Posted by SandwichTech View Post
 

@Tog The Ipe offers a few key benefits that made us choose it.  First it has a much higher modulus than UHMW or ABS which makes for added torsional stiffness and edge-compression strength.  From a reliability standpoint, Ipe (or any wood) is going to bond to your core and composite facings much better than you will ever get from UHMW or ABS (a typical starting point for delamination on other skis).  Finally, compared to bamboo or oak or black locust (wood sidewalls used by other indie brands),

 

Ipe is naturally waterproof.  Ipe decking is rated for 75+ years.  As far as performance and reliability, I would choose phenol as a close second, but because of brittleness we chose Ipe.  Aesthetics are personal preference. 

Interesting on the bonding and structural part.

As far as the 75 years...The Ipe Decks I've seen left untreated will never make it. But we all know that anyway, just like pressure treated and the 30 years.

 

Anyway, more importantly to the owner, how do you plane the sidewalls for sharpening?

post #24 of 25

@SandwichTech

 

Thanks for the reply.  I think a second test showing both would be beneficial as it does take the bending moment into account as in the real world this is part of the feel of the ski as you carve those railway tracks.  It would be interesting if the results showed one thing taken one way and something else when taken the other way.  This could lead to a good corilation between feel and actual performance.

 

Example; Tests torsional stiff yet feels soft and has no grip or the opposite.

post #25 of 25
Thread Starter 
Quote:
Originally Posted by Tog View Post
 

Interesting on the bonding and structural part.

As far as the 75 years...The Ipe Decks I've seen left untreated will never make it. But we all know that anyway, just like pressure treated and the 30 years.

 

Anyway, more importantly to the owner, how do you plane the sidewalls for sharpening?

 

I wouldn't expect an ipe deck to last as long as the rating...but then I also wouldn't leave my skis out in the rain sidewall-up :)  Most sidewall planers have carbide inserts that can shave metal (titanal) - they have no problem with ipe.


Edited by SandwichTech - 4/7/14 at 8:40pm
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