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Tecnical Question about float

post #1 of 17
Thread Starter 
Which ski would have the better float. If the two ski's had same comstruction, same side cut ratio, But one ski is 7cm longer and the other is 7mm wider throughout the skis length? Let's say a 170 and 177cm.
post #2 of 17
Im no techy but I would go with the wider one...but thats just me.
post #3 of 17
1700 X 80 = 136,000 square millimeters

1770 X 73 = 129,210 square millimeters
post #4 of 17
Thread Starter 
Is that all that matters though? Just more surface area? Does it matter where it is distributed? Does more width under foot mean more than width in shovel?
post #5 of 17
To be more elaborate, but (not surprisingly) to get the same answer

170 cm ski (162 cm actually running), 117 mm widest width, 16m sidecut:
1,674 square centimeters area

177 cm ski (169 cm actually running), 110 mm widest width, 16m sidecut:
1,608 square centimeters area
post #6 of 17
Quote:
Originally Posted by ski=free
Is that all that matters though? Just more surface area? Does it matter where it is distributed? Does more width under foot mean more than width in shovel?
Yeah, but you said:

Quote:
same comstruction, same side cut ratio
Plus you posited two lengths relatively close (7 cm) to one another.
post #7 of 17
Ah, good, something I can screw up very easily and not worry.

Assume a rectangle of width 100mm, ignore the nonsense regarding sidecut ratio (whatever that is) and that the entirety of the ski is flat on the snow in both cases. Area is what we want, because 'float' will be greater (less sinkage) with a constant mass (weight/force whatever) when force per unit area is less.

Area = length x width (of a rectangle)
1cm = 10mm

Scenario 1: 170cm length (107mm width) = (18190 mm^2)
Scenario 2: 177cm length (100mm width) = (17700 mm^2)

You do the math, dinner time for me.
post #8 of 17
Quote:
Originally Posted by ski=free
Is that all that matters though? Just more surface area? Does it matter where it is distributed? Does more width under foot mean more than width in shovel?
Sure it matters where in the real world, but that's no starting place.
post #9 of 17
Not to hijack your question, but I think the issue is really which ski would float better while standing on the middle of it. A longer ski with a soft flex in the front will give you float with your weight in the middle or even forward. A shorter fatter ski may give you more surface area, but you will have to be leaning farther back to make it work, so you would have to ski it differently to utilize the float. That's why I like a long powder ski. The short ones force you in the back seat to keep them from diving. You've got the surface area for float, but you end up swizzling them from too far back instead of charging forward and having the tip rise up. IMHO a wide soft tip longer ski will get you more float time than an shorter fatter ski. You should be able to push or dive a good powder ski into the snow and have the tips load up and then surface on their own.
post #10 of 17
Well ... it all depends how much shorter and how much fatter:

7 cm = a little shorter
7 mm = significantly fatter

... and that's whether you're talking about geometry or skis
post #11 of 17
As eastern skiers we don't have the float issue come up as "common" critical element in our every day skiing but, mudfoot hit on the flex issue and I tend to support that.

The softer forebody of the ski will allow better balance in powder, you will be more centered over the ski.
post #12 of 17
Thread Starter 
Mudfoot, no hijack at all. I actually had a bunch of questions and not much time to write the thread, that's why my first post is a little crude.
Basically what I wanted to know is what exactly determines that a ski float better than another? Surface area has a lot to do with it, but obviously it isn't the whole story. If a ski is too fat and not long enough it's not going to ski well.
Also is width more important under foot than in the shovel and tail?
And flex, obviously it's important as you pointed out.
I know it's probably impossible to quantify what makes a ski float better than another with the very limited criteria I've given here. But I'd bet nasa could give me a pretty good answer.
post #13 of 17
Quote:
Originally Posted by sjjohnston
Well ... it all depends how much shorter and how much fatter:

7 cm = a little shorter
7 mm = significantly fatter

... and that's whether you're talking about geometry or skis
I'll second that. It's kind of like the difference between giving a homeless guy $1 and giving someone in a home $5. $1 will feed the homeless guy his normal meal, but $5 isn't going to satisfy the person in a home.
post #14 of 17
I think width is important in the tip and under foot. I have never liked really shapey skis in deeper snow because they feel squirrely. You don't need much sidecut because you are turning as much or more with the changed shape of the flexed ski as opposed to the sidecut. For me the dilemma has always been finding the perfect powder/crud ski. The perfect powder ski has a soft wide tip, but when the snow firms up a little this kind of ski will contiunally try and climb up on top of the snown (unwanted flloat) and makes you fight to get back down in it where you can control things. You need a striffer tipped ski for punching through the crud. The "perfect" powder and crud skis are dissimilar, but those snow conditions normally follow each other either from morning to afternoon, or top to bottom of the mountain.

If you want an interesting take on float and carving with fat skis, check out the article in the lastest issue of Powder on the K2 Pontoon that Shane McConkey is designing. It's 155-130-120 with reverse camber and will come in a 179 or 189 cm. Like with the Spatula, McConkey is again reinventing skis.
post #15 of 17
Compare the float of a 1800mmX100mm ski to a 18000mmX10mm ski.
post #16 of 17
Yea but how does the ski feel?
post #17 of 17
You want the width under your foot, that's where the weight is supported. What good is the tip floating if the rest of the ski is sinking? True you do need some width in the shovel also, but skis with a wider waist generally have a proportionately wide enough shovel.
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