I keep telling my skis to simmer down now but they aren't listening.
My last pair came out super light and seem to have no damping properties at all. Off trail they are nervous, deflect easily, and bounce around quite a lot in choppy crud. At least on smooth groomed when locked in a carve they feel rock solid even at high speeds.
The flex is about what I was looking for but I think the poplar core with maple sidewalls is too light and lively. The profile I did was 12.2 to 2.2 so maybe I'll make the tips and tails thicker. I also want to change to a denser core material.
I assume that the VDS over the edges doesn't do much for damping and is more a shear layer. Snowboard materials has some 12" wide stuff so I was wondering if that might do anything if I did a full ski layer, maybe top and bottom.
One pair I made with plastic sidewalls was considerably damper but they delammed and I don't want to risk that again.
I know some guys are experimenting with rubber and aluminum. Does the rubber available from such places as McMaster bond well or is some pre-treatment necessary? I also like Kam's idea about perforating metal to enhance bonding. Maybe I'll try that too.
Anyone else having any ideas they would like to share?
simmer down now
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If the trouble with bonding aluminium is related to its smoothness there is a chemical treatment called alladyne that is used in the aircraft industry to help with paint bonding. It chemically etches the aluminium surface which I assume makes many many microscopic roughened areas that the paint can physically interlock with. I haven't tried it, but have thought about using it when I make my first pairs - thinking of a thin Al sheet for binding mounting. Epoxy should similarly interlock physically (I imagine its like the reason the plastics need abrasion) but I also don't know how alladyne and epoxy get on together. The paints generally used are 2 pack polyurethane paints which are a similar idea to epoxy with the actual paint being mixed with a hardener prior to application.
About rubber - I don't know too much, but I know a lot of people believe the VDS is simply a bonding aid (maybe that's actually a fact) and has no damping properties. I also know that Kingswood have rubber strips on top and I think below their core for damping. If you watch their video on the site you see him lay out black material. I thought it was carbon fibre, but apparently at least some of it is rubber stripping I think 25mm wide. He also looks like he places a formed rubber tip spacer element on tip and tail also, but it could be cut out plastic.
About rubber - I don't know too much, but I know a lot of people believe the VDS is simply a bonding aid (maybe that's actually a fact) and has no damping properties. I also know that Kingswood have rubber strips on top and I think below their core for damping. If you watch their video on the site you see him lay out black material. I thought it was carbon fibre, but apparently at least some of it is rubber stripping I think 25mm wide. He also looks like he places a formed rubber tip spacer element on tip and tail also, but it could be cut out plastic.
Most of the rubber from McMaster will not bond. You have to treat it, for example using Chemlok, but be careful with it as the chemical is not that healthy for you. Some abrading will help, but the surface must be chemically treated.
The thin rubber used by many ski companies is simply to act as a shear layer to minimize delams. Rossignol and several others have used a type of rubber as a tip fill, but again the main reason is to minimize delams, especially during dynamic situations. As a ski bends, the layers want to shear relative to each other. Having a thin compliant layer between layers that don't bond well helps to keep them from failing in shear. Being thin, the rubber has little to no effect on damping, but if you use enough of it anything can happen. Heck, training a small soft rodent to ride near the tip of your ski will work, too!
There are a number of techniques for damping which involve specialized sandwiches made from, for example, different types of metals and viscoeleastic elements, strategically placed throughout the ski. Again, damping is about dissipating energy.
The thin rubber used by many ski companies is simply to act as a shear layer to minimize delams. Rossignol and several others have used a type of rubber as a tip fill, but again the main reason is to minimize delams, especially during dynamic situations. As a ski bends, the layers want to shear relative to each other. Having a thin compliant layer between layers that don't bond well helps to keep them from failing in shear. Being thin, the rubber has little to no effect on damping, but if you use enough of it anything can happen. Heck, training a small soft rodent to ride near the tip of your ski will work, too!
There are a number of techniques for damping which involve specialized sandwiches made from, for example, different types of metals and viscoeleastic elements, strategically placed throughout the ski. Again, damping is about dissipating energy.
DD,
You could implement a passive particle damping system like this
http://www.unr.edu/features/09-10/snow-science/.
The design team claims a ~65% reduction in tip acceleration in the first mode.
You could implement a passive particle damping system like this
http://www.unr.edu/features/09-10/snow-science/.
The design team claims a ~65% reduction in tip acceleration in the first mode.
Brian
Dr. Delam, I have a pair that behave like you describe also. I think the reason is due to a long binding mount area. I kept the binding area long, like > 1/3 of the ski length. You really have to be on your game to ski them. They are fun in smooth powder or groomers as long as you can keep up with them. They have no speed limit other than my terror level. On a smooth open run they go as fast as you dare. Get into any rough/choppy conditions and you get bucked around… a lot. I have been thrown over the handle bars, more than once, because of the rebound in these skis on a ski cut/packed mogul run . Sound familiar?
So on my skis the profile from the 11mm mount area to the ~2.5mm tip/tail is very short. The tip is a bit longer but overall the ski is very stiff. Could that be your issue? I have found that I like to dome the core. I cut the profile from ~50mm before and after the cord center and block sand the center into a dome. The skis are much friendlier to ski. Still lively but I’m not getting bucked around.
Anyway good luck finding a solution
Hafte
Truckee, haven’t been there since I was living in Reno about ’73. I really would like to get back there and see how much the ski areas have changed. That’s on my list of places to visit in the near future. I hear Mount Rose has really change since the 70’s. That’s where my dad patrolled.
So on my skis the profile from the 11mm mount area to the ~2.5mm tip/tail is very short. The tip is a bit longer but overall the ski is very stiff. Could that be your issue? I have found that I like to dome the core. I cut the profile from ~50mm before and after the cord center and block sand the center into a dome. The skis are much friendlier to ski. Still lively but I’m not getting bucked around.
Anyway good luck finding a solution
Hafte
Truckee, haven’t been there since I was living in Reno about ’73. I really would like to get back there and see how much the ski areas have changed. That’s on my list of places to visit in the near future. I hear Mount Rose has really change since the 70’s. That’s where my dad patrolled.
I have never done a totally flat binding mount area in my profile. I figured I would get a rounder flex with something like a flat bell curve.
But you do have me thinking that maybe the rate of taper does need to change some. I think for my next pair I want to reduce the core apex by .5 mm and increase the tip and tail by .5mm.
I have been in Truckee for 15 years and in that time the area has radically changed. Development has gotten out of hand. At the ski areas, high speed chairs are ubiquitous and everything gets tracked out within hours. But the terrain and the ripping skiing hasn't changed so that is why I still love it. Come back and check it out!
But you do have me thinking that maybe the rate of taper does need to change some. I think for my next pair I want to reduce the core apex by .5 mm and increase the tip and tail by .5mm.
I have been in Truckee for 15 years and in that time the area has radically changed. Development has gotten out of hand. At the ski areas, high speed chairs are ubiquitous and everything gets tracked out within hours. But the terrain and the ripping skiing hasn't changed so that is why I still love it. Come back and check it out!
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MontuckyMadman
- Posts: 2395
- Joined: Fri Jun 20, 2008 9:41 pm
I used poplar/beach core and they turned out soft and insane light. maybe 7.5lbs per pair.
1.7mm tip to cord 11mm center but they are 140-120-130.
They fly around a bit but are light enough to bring back in control but the deflection I notice seems relative to the softness.
This shape is amazing and with 30 cm rocker, also awesome. I was going to add a flat area but maybe now just increase the overall thickness to 13mm on center and 2.5mm or maybe 3mm in the tip.
I'm sure a denser wood of maple or ash or oak as stringers in place of the beach may increase dampness.
I really feel you can get a damp wood and glass ski without the addition of metals and rubbers.
1.7mm tip to cord 11mm center but they are 140-120-130.
They fly around a bit but are light enough to bring back in control but the deflection I notice seems relative to the softness.
This shape is amazing and with 30 cm rocker, also awesome. I was going to add a flat area but maybe now just increase the overall thickness to 13mm on center and 2.5mm or maybe 3mm in the tip.
I'm sure a denser wood of maple or ash or oak as stringers in place of the beach may increase dampness.
I really feel you can get a damp wood and glass ski without the addition of metals and rubbers.