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sizing a powder ski

post #1 of 22
Thread Starter 

I am looking to buy a pair of Rossingol Soul 7's so I have a ski that is a bit better in powder conditions, but versatile enough that I can ski typical New England slopes once the powder gets skied off by midday.  I currently ski Atomic Nomad's (size 164) which are an All Mountain ski.  I was told when you go to a more powder oriented ski that you should go up in size a bit ,which I believe is to help the floatation. If I upgrade the size, what should I go with a 172 or 180 in the Soul 7's?   I'm about 5'9" and weigh about 180.  I am an advanced skier and enjoy everything. Groomers, Powder, glades, etc.  Any thoughts or suggestions on size would be truly appreciated. 

post #2 of 22
Minimum 180, longer for a true powder ski. If only for occasional NE powder and more for general all mtn use then 180 will be ok.
post #3 of 22

The Soul 7 is made in lengths of 164 cm, 172, 180, 188.  What's the difference?

 

Skis are made stiffer as they are made longer.  The ski needs to respond to the energy the skier puts into it.  A ski too short/soft feels like a noodle.  One too long/stiff feels like skiing on a 2x4.  The 164 is made for the flyweight who is a very good skier.  The 188 is made for the biggest, most powerful skier on the mountain.  You are "5'9" and weigh about 180.  I am an advanced skier."  The 180 is probably a good choice.

post #4 of 22
Quote:
Originally Posted by SoftSnowGuy View Post

The Soul 7 is made in lengths of 164 cm, 172, 180, 188.  What's the difference?

Skis are made stiffer as they are made longer.  The ski needs to respond to the energy the skier puts into it.  A ski too short/soft feels like a noodle.  One too long/stiff feels like skiing on a 2x4.  The 164 is made for the flyweight who is a very good skier.  The 188 is made for the biggest, most powerful skier on the mountain.  You are "5'9" and weigh about 180.  I am an advanced skier."  The 180 is probably a good choice.

Except the Soul 7. The 166 is very stiff. The 188 is made for tall, light expert skiers, or heavier intermediates. The biggest, most powerful skiers on the mountain aren't on a Soul 7. Not tht it's a bad ski, but it certainly isn't a high performance 'big mountain' ski. That's what the Squad 7 is for. And I agree, for the OP, the 180 is the choice.
post #5 of 22
Thread Starter 

Thanks for the help and explanation.  Most appreciated!!

post #6 of 22
Thread Starter 

Thanks for the help and explanation. Most appreciated!

post #7 of 22
Thread Starter 

Thanks!!

post #8 of 22

Are you locked into only wanting that ski ?

 

There may be better choices out there.

post #9 of 22
Thread Starter 

No not by any means.  The unfortunate part is that I live in Danbury, CT.  So I do not get to ski powder often.  The other problem is that most resorts in NE don't demo powder skis bc All Mountain is typically a more appropriate ski.  While I hate purchasing a ski without trying it, I don't have much choice as it is rare that I find a place that both Demo's a powder ski and has a powder day at the same time I am there.  

 

Anyway, I did a bit of research and was looking for a ski that has good floatation, but can ski most terrain once the powder is skied off as is the common occurrence in NE.  That's what brought me to the Soul 7.     All that said, I am definitely interested in any and all suggestions on other skis that you may have that may fit this description, as I am by no means locked in on that particular ski.  Thanks in advance for the input. 

post #10 of 22

Mount Snow demo shop had the Soul 7 last year in their program, so likely this year as well.

post #11 of 22
Thread Starter 

Thank you for the heads up.  I guess I will be going to Mount Snow in my near future (I hope!). Many thanks

post #12 of 22

As a guy who seeks out eastern powder as often as I can, I'd suggest you open your mind to other skis also.  MOST of the time, "powder" in the east means 6" or less, which gets skied out by 11:00 at the latest.  If you're really going to go in the trees, then maybe the Soul is a good choice.  But if you're going to ski the chop that turns into push-piles separated by hard-pack or ice (the most common after-effect of fresh snow in the east), you might well want a beefier ski.  I haven't skied it myself, but most folks who do say the Soul is really a soft-snow kind of animal -- and may not have enough grip/stiffness/beef for the conditions I reference above.  

 

Just a thought that you should probably demo a few skis while you're at it.  You may love the Soul...or you may find something else more to your liking.

post #13 of 22

I skied the Soul & at a free demo day at Okemo season before last.  You would definitely want the 180.  I also rented a pair for 2 days in Whitefish powder and then crud and soft bumps.  It was fine in all those conditions.  The front 6" of the ski just kind of flops around on hardpack but really comes into play in the powder and crud.  I would say they are fine for eastern trees and soft days.  I also live in CT.   Both times I skied them in 188cm.  I am 5' 11" and weighed about 215 when I skied them...consider myself an expert.  I like a softer, easy to turn ski and the Soul 7 is definitely that.

post #14 of 22

180 is perfect size for you - i ski the goods in Utah and am around the same size, 172's would be way too short for you - ( been there and done that ) -  all my fat rockers are between 178-183cm's -( line bacon, pollard opus,armada bubbas,faction royale) - no problem whipping them around in the trees

post #15 of 22
Thread Starter 

180 definitely seems to be the general consensus.  Thanks for the input it is greatly appreciated. 

post #16 of 22
Thread Starter 

Thanks for the feedback.  I have heard they are a great ski.  Okemo and Snow are two of my favorite places to ski, so I am going to definitely take a "sick day" on our next powder morning to give them a try.  Can't wait. Thanks again for the help.

post #17 of 22
Quote:
Originally Posted by NEPowder View Post
 

I am looking to buy a pair of Rossingol Soul 7's so I have a ski that is a bit better in powder conditions, but versatile enough that I can ski typical New England slopes once the powder gets skied off by midday.  I currently ski Atomic Nomad's (size 164) which are an All Mountain ski.  I was told when you go to a more powder oriented ski that you should go up in size a bit ,which I believe is to help the floatation. If I upgrade the size, what should I go with a 172 or 180 in the Soul 7's?   I'm about 5'9" and weigh about 180.  I am an advanced skier and enjoy everything. Groomers, Powder, glades, etc.  Any thoughts or suggestions on size would be truly appreciated.

So, I should start out saying that I haven't skied in the east. I would agree with others here that are suggesting a 180 length. I am 5"4' and about 145 and that is pretty much what I'm skiing. I just bought a Nordica Patron in a 177, but it is the same physical length as my 183 Rossi's. 113mm under foot, but it does not ski like a fat. It's pretty quick edge to edge and nimble. Very fun, playful ski regardless of snow conditions. It has traditional camber under foot with early rise in the tip and tail so it skis almost normally. I did have to widen my stance considerably. Hope this helps.

post #18 of 22
Quote:
Originally Posted by SoftSnowGuy View Post
 

Skis are made stiffer as they are made longer.

Not sure I agree; can you provide a link or evidence? 

 

As several of us here have noted previously, a ski's stiffness - assuming materials are held constant -  is mainly determined by its cross sectional area at whatever point you're measuring. Not by the length. Which will influence pressure we can exert on the tip, another issue.

 

As I dimly recall physics (not an engineer), the formulas have unrealistic assumptions like homogenous materials, uniform beams, symmetry, lack of torsion, and all that otherworldly stuff physics always assumes. And as I recall, the issue is bending. What we call stiffness is sufficient resistance to bending that the ski flexes a certain amount. We seem less concerned about structural failure, like a bridge, although obviously people break skis occasionally. And doesn't seem like shear even counts. I assume this means that skis are over engineered and that literal failure is not a market concern, while enough resistance to bending - and torsion - forces is.

 

So. I think that how much bending stress is changed by size is the key. I think that bending stress = (Moment around the axis) x (distance to that axis)/(Some other moment (can't remember)) x (cross sectional area around the longitudinal axis). Which I translate as meaning that as cross sectional area increases at the same length, bending stress decreases. While as length increases, at the same area, bending stress also increases. I'd add that area increases by the square, distance does not. That becomes a big deal in terms of what we're talking about. The resistance to bending contributed by area increases faster than the desire to bend contributed by length. So the actual stress gets lower as the area increases. In theory, a ski could be shaped like a shoebox and never bend with the forces we generate. You can't do that with a bridge because it'd weigh too much. And AFAIK, bridge people, like ski designers, want some flex. 

 

So (I think) longer skis are actually flexier, not stiffer, but the effect is small because the differences in length are small compared to the contribution of the cross sectional area. And the material used. It is possible that ski engineers have compensated for this by making longer skis thicker, but I've made a few micrometer measurements when I have access to several of same model, different lengths, have never found a difference. OTOH, I've read here that some long models are specifically made stiffer, which must mean thicker or something different inside. Or it may be that the changes in area required are tiny enough to be inside my measurement error.

 

Moreover, unclear to me in a business sense why ski engineers would make longer skis stiffer, as opposed to perhaps keeping them the same stiffness. Unless they were planning for a waaay bigger skier range, like needing to make the longest length suitable for a 350 pounder down to a 200 guy. Or have some data that really heavier guys are also faster or more expert skiers. (Nothing personal, larger Epic guys. :D)

 

But IMHO, there are so few people who weigh over 250 actually skiing that it wouldn't justify the bother commercially, and anyway the product would be unsuitable for a more typical demographic, the taller normal to lean skier who is 6'4" and weighs 220. (Skiing being a sport of the upper and upper middle classes, who tend to be taller and leaner, y'know). If I'm a truly big guy, I don't go for a longer length Rossi than my height justifies, I go for a different brand. Stockli and Head and Moment and Blizzard become my friends. 

 

Anyway, have not measured the Soul series, although have demoed it. And own a Super 7, longest length, doesn't flex or ski any differently than the next length down, far as I can tell, just more stabile and a little tougher to turn (both other issues than addressed above). I really doubt the Soul is any different. 

 

OK, now have my usual non-engineer headache trying to puzzle out what I learned off of scratches on stones in the middle paleolithic. And I probably used the wrong formula or remembered it wrong. But if I'm vaguely right, then:

 

Unless you can show me that the longer lengths of the Soul actually have thicker cross sections, or different materials like a sheet of metal or carbon that the others don't, your statement is physically impossible. I think...

 

Your turn. Carry on. :) 

post #19 of 22
I think the Soul 7 skis would be great for those conditions.
Edited by FatChance - 11/21/15 at 11:08am
post #20 of 22
Quote:
Originally Posted by beyond View Post
 

Not sure I agree; can you provide a link or evidence?

 

As several of us here have noted previously, a ski's stiffness - assuming materials are held constant -  is mainly determined by its cross sectional area at whatever point you're measuring. Not by the length. Which will influence pressure we can exert on the tip, another issue.

 

As I dimly recall physics (not an engineer), the formulas have unrealistic assumptions like homogenous materials, uniform beams, symmetry, lack of torsion, and all that otherworldly stuff physics always assumes. And as I recall, the issue is bending. What we call stiffness is sufficient resistance to bending that the ski flexes a certain amount. We seem less concerned about structural failure, like a bridge, although obviously people break skis occasionally. And doesn't seem like shear even counts. I assume this means that skis are over engineered and that literal failure is not a market concern, while enough resistance to bending - and torsion - forces is.

 

So. I think that how much bending stress is changed by size is the key. I think that bending stress = (Moment around the axis) x (distance to that axis)/(Some other moment (can't remember)) x (cross sectional area around the longitudinal axis). Which I translate as meaning that as cross sectional area increases at the same length, bending stress decreases. While as length increases, at the same area, bending stress also increases. I'd add that area increases by the square, distance does not. That becomes a big deal in terms of what we're talking about. The resistance to bending contributed by area increases faster than the desire to bend contributed by length. So the actual stress gets lower as the area increases. In theory, a ski could be shaped like a shoebox and never bend with the forces we generate. You can't do that with a bridge because it'd weigh too much. And AFAIK, bridge people, like ski designers, want some flex.

 

So (I think) longer skis are actually flexier, not stiffer, but the effect is small because the differences in length are small compared to the contribution of the cross sectional area. And the material used. It is possible that ski engineers have compensated for this by making longer skis thicker, but I've made a few micrometer measurements when I have access to several of same model, different lengths, have never found a difference. OTOH, I've read here that some long models are specifically made stiffer, which must mean thicker or something different inside. Or it may be that the changes in area required are tiny enough to be inside my measurement error.

 

Moreover, unclear to me in a business sense why ski engineers would make longer skis stiffer, as opposed to perhaps keeping them the same stiffness. Unless they were planning for a waaay bigger skier range, like needing to make the longest length suitable for a 350 pounder down to a 200 guy. Or have some data that really heavier guys are also faster or more expert skiers. (Nothing personal, larger Epic guys. :D)

 

But IMHO, there are so few people who weigh over 250 actually skiing that it wouldn't justify the bother commercially, and anyway the product would be unsuitable for a more typical demographic, the taller normal to lean skier who is 6'4" and weighs 220. (Skiing being a sport of the upper and upper middle classes, who tend to be taller and leaner, y'know). If I'm a truly big guy, I don't go for a longer length Rossi than my height justifies, I go for a different brand. Stockli and Head and Moment and Blizzard become my friends.

 

Anyway, have not measured the Soul series, although have demoed it. And own a Super 7, longest length, doesn't flex or ski any differently than the next length down, far as I can tell, just more stabile and a little tougher to turn (both other issues than addressed above). I really doubt the Soul is any different.

 

OK, now have my usual non-engineer headache trying to puzzle out what I learned off of scratches on stones in the middle paleolithic. And I probably used the wrong formula or remembered it wrong. But if I'm vaguely right, then:

 

Unless you can show me that the longer lengths of the Soul actually have thicker cross sections, or different materials like a sheet of metal or carbon that the others don't, your statement is physically impossible. I think...

 

Your turn. Carry on. :)

I'm also not an engineer, but in my experience, core thickness in a particular model does increase proportionally with length. It's only thousandths of an inch for every centimeter of increased length, but longer skis are indeed a few thousandths thicker than shorter lengths. If metal, phenolic or fiberglass is added, then the thickness of the core is reduced slightly to allow the extra material to fit in the ski. I only have experience making wooden cores at the Volant factory, but I would guess that other core materials have a similar dynamic, but maybe not. Props for the physics. I couldn't do it. 

post #21 of 22
Not that I care tremendously, but some ski manufacturers are very good at making their skis progressively stiffer appropriate to length. Others are not. Rossi is on the latter list.
post #22 of 22
Try the new Enforcer if you can demo. Also the Rocker2 100.

But the Enforcer would be best of the bunch on paper for harder snow days.
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