Putting a rocker in my Sumos?

[LC]

Damn, I might give this a shot on my Thugs over summer. I wasn't too happy with them in pow this winter, but that's definitely at least partly due to the fact I was kidding myself how much switch I'd be doing and went against opinions with the mount (-3.5 from running length centre) so a remount might be a good call too. So, anyone rockered Thugs?

And for a non-switch skier, why rocker the tails? Yeah most companies are doing it so should we just not ask questions and assume they've done it for a reason? What's the consensus on what sort of tip separation and contact points at both tip and tail are optimal for a pow-focused but groomer-capable ski? Best to look at someone like ON3P's stats and aim for what I like the sound of?

[Caucasian Asian]

I should clear some stuff up a bit. Yeah, we "rockered" the tips/tails of my skis, but not as much as it sounds. It's more like we moved the contact points back ~15cm in the tips and ~10cm in the tails. In K2 speak the tips are 10/15(10mm/15cm) and the tails 5/10. Not a lot of rocker when you compare it to most skis. I did not want very much rocker because I liked the way they skied on hardpack. I was looking for a rocker profile similar to a VCT Turbo.

I added a touch of rocker to the tails to make them a little easier to pivot in tight areas, not to make them ski switch better. As well, I found that my tip-only rockered ski felt like there was too much tail on hard pack. I felt it encouraged me to ski in the backseat a little.

I would try re-mounting your Thugs before you start bending them. But then again, I felt that even the rear mounting line was a little forward for me.

[XtrPickels]

Damn, I might give this a shot on my Thugs over summer. I wasn't too happy with them in pow this winter, but that's definitely at least partly due to the fact I was kidding myself how much switch I'd be doing and went against opinions with the mount (-3.5 from running length centre) so a remount might be a good call too. So, anyone rockered Thugs?

And for a non-switch skier, why rocker the tails? Yeah most companies are doing it so should we just not ask questions and assume they've done it for a reason? What's the consensus on what sort of tip separation and contact points at both tip and tail are optimal for a pow-focused but groomer-capable ski? Best to look at someone like ON3P's stats and aim for what I like the sound of?

In my opinion, rockering the tails increases maneuverability immensely. However, you lose the stability of the tail and the ability to really rail turns in steep / high speed situations.

My self rockered tahoes are super fun and playful. They're a phenomenal tree ski. They carve great on intermediate groomers but they lost the ability to be there when I realllly needed to stand on them, instead the tails have a tendency to wash out. (eg carving highspeed turns down a steep slope).

If you're putting the ski on edge and pulling g's then leave the tails alone. If you want a playful ski that's great in tight places then rocker 'em.

[FranklezZ]

I know you guys are having fun bending skis and all but this may be of some interest and help you find an appropriate temperature when doing this.

Carbon and fiberglass composites (skis) generally use epoxy as a matrix (glue) material. Epoxy is a thermoset polymer, meaning that it gets harder when you heat it. It does however have a "glass transition temperature" (Tg) that lies somewhere between 150C-190C. (~340F-390F) Google it. Which means that some of its material properties change at that temp, it may soften, (ever so slightly) which would relieve strain and allow it to cool in a slightly different shape.

(although West System Epoxy states their Tg somewhere between 115F - 160F, which I could not confirm by any other source for epoxy, and I think is wrong!)

The fiberglass cloth in contrast has a Tg ~2000C, we will never make it "soft."

The base material, side walls and top sheets actually also have a working temp in the same ballpark as the epoxy glass transition temperature:

"Unlike most thermoplastics, UHMW plastic does not become a liquid when it is heated above its "melting point". Because of its high melt strength, it can be handled and shaped above its crystalline melting temperature of 265° F (129° C). Although UHMW plastic can also be shaped below the crystalline melting point, this causes residual stress in the part.

Heating

Optimum forming temperatures for Gar-Dur® plastic sheet, rod or bar are 280 to 300° F (138 to 149° C). At these temperatures, the plastic is translucent and newsprint can be easily read through thin sections.

Methods for heating Gar-Dur® plastic include air-circulating ovens, conventional ovens (similar to those in the home), heat lamps, radiant heating panels and oil baths. The most reliable ones are the air-circulating oven and the oil bath, since these heat most uniformly. With other methods, it is difficult to control temperature accurately and uniformly. Colors can also affect radiant energy heating.

A conventional fryer can be used as an oil bath for heating small parts. Most units for use in homes will hold temperatures with sufficient accuracy for the forming processes. Recommended heating oils are glycerin, silicone oil and commercial automobile antifreeze (ethylene glycol)"

Also be aware of sharp corners, such as those displayed in most of the jig pics in this thread, they are known stress risers. It means there will be exaggerated stress in that location. stress --> strain, which is deformation. This explains the "kinks" we have seen in many of the photos.

Lastly we want to relieve as much residual strain as possible, which means we want the COOLING period as LONG as reasonably possible.

So the plan. (I wish I could do it)

1.Create a jig with rounded, large radius, contact points, perhaps with multiple points.

2. preheat oven to 350F, and bake, slowly reducing the temp over a couple of hours.
2b. deep fry that thing!! ( make sure to test how soft the base material gets first)

3. somewhere around 200F wrap it up and keep it warm for as long as possible.

4. when fully cooled check rocker.

You could make a makeshift oven door out of plywood and fiberglass cloth. Wood will be totally safe up to ~400F

ref:
http://www.arlon-med.com/Measuring%2...nding%20Tg.pdf
http://www.epotek.com/SSCDocs/whitep...Paper%2011.pdf
http://www.springerlink.com/content/n12h0782nv8n8465/
http://www.garlandmfg.com/plastics/h...mingparts.html

[FranklezZ]

Wow what a mess.

cliff notes:

I think the optimum temp for reshaping skis lies between ~300F-350F <-- absolutely above 265F to avoid residual stress in the base material.
Use an oven if possible. A make shift ply door will be safe under 400F
the hotter the better
test a piece of base material first. (UHWPE starts getting soft ~265F)

Let them cool as long as possible, which means reduce the heat slowly then keep 'em warm.

Use jigs with large radius curvature if possible. Avoid sharp corners.

Man I need a garage!

[El Chupacabra]

Mid-summer update:

My 190 Sumos have been sitting in the rafters of a backyard shed, with a 2x4 shoved between the tips (two C-clamps are holding the skis base-to-base; clamps are positioned about 3" ahead of the binding toe pieces). The skis have been sitting this way for about 3 months. It's hot in that shed -- probably gets to 120-130 degrees during the hottest times of the summer.

I've got rocker in the Sumos: fairly mild; closest ski I can think of that it resembles is the Salomon Czar. I don't know if the rocker profile will stay, but I shoved the 2x4 a bit further down between the skis, and am going to leave it there through the rest of the summer. We'll see what happens.

No delaminating, wrinkles, or other visible bad side effects.

[Huck_Schmuck]

Mid-summer update:

My 190 Sumos have been sitting in the rafters of a backyard shed, with a 2x4 shoved between the tips (two C-clamps are holding the skis base-to-base; clamps are positioned about 3" ahead of the binding toe pieces). The skis have been sitting this way for about 3 months. It's hot in that shed -- probably gets to 120-130 degrees during the hottest times of the summer.

I've got rocker in the Sumos: fairly mild; closest ski I can think of that it resembles is the Salomon Czar. I don't know if the rocker profile will stay, but I shoved the 2x4 a bit further down between the skis, and am going to leave it there through the rest of the summer. We'll see what happens.

No delaminating, wrinkles, or other visible bad side effects.

Chup - I don't think this will work brilliantly. I left a pair of Pow Plus' like that for 5 months. Mostly in a boiler room which was normally around 80deg. That wasn't doing anything so I left them in a sauna, which was used quite a bit at around 200deg.

The Sumos should be easier than the Pow + so maybe it will work out. I suspect you will need to apply direct heat.

I ended up giving the Pow + to a friend for Xmas, he stuck them in an agricultural pipe bender and got wicked rocker on them. B'stard still owes me pics...

[El Chupacabra]

he stuck them in an agricultural pipe bender

That'll certainly bend a ski!

I don't know if my home-rocker experiment will work for the long run. If not, it doesn't look like I'm doing any permanent damage to the ski (no wrinkles/cracks/etc. visible), so at worst, this might just be a waste of time.

I'll update this in the fall with some photos. After I pull the 2x4 out in a couple of months, it'll depend on what happens after another couple weeks/months go by after I remove that pressure. The ski might just return to its normal camber.

[wildskizer]

Chup - I don't think this will work brilliantly. I left a pair of Pow Plus' like that for 5 months. Mostly in a boiler room which was normally around 80deg. That wasn't doing anything so I left them in a sauna, which was used quite a bit at around 200deg.

The Sumos should be easier than the Pow + so maybe it will work out. I suspect you will need to apply direct heat.

I ended up giving the Pow + to a friend for Xmas, he stuck them in an agricultural pipe bender and got wicked rocker on them. B'stard still owes me pics...

Huck; Yes, the mild pressures of the clamp, block and leave'm won't work cause they have metal in them. You have to Seriously bending them like your friend did, and others have done on open riser stairs, in a Dumpster side slot, etc., which bends the metal layer, and puts a permanent rocker in them.

The Sumos, on the other hand, having no metal, seem to respond to heat treated blocking processes.
'CHUP': I have succeeded in eliminating all the 1/2" of original camber, on mu Sumos, and have put 2 mm of early rise in tails, and 1cm of early rise separation between the tips when placed base to base. I still have them clamped together, mid way between the top of toe binder and tips and wedged open at the tips with a 1" spacer. I apply heat now and then with a steam iron on high over a wet cloth. Will continue to do so till the snow flies. No visible stress indicators, and the bend / rocker seems to be gradual, without an abrupt bend point. I am satisfied with the minimal rise in the tail as I want to retain edge hold on packed slopes because these will be used mostly for Pow days on lift served terrain and side stashes.

Wish I could figure a way to effectively make use of the info and suggestions in the great tech post by 'FranklezZ', on thins subject.

I'll post an update on this process , and how they ski, when the time comes to ski them.

Later, Cheers...to all benders...

[lobstahmeatwad]

I put more rocker in some 138s that I made, after I tried it initially with the heat gun and fuct the topsheet.

This may have worked much better. I have a silicon heat blanket sandwiched in between the AL sheets that I use to press skis.

I cooked to 235F as 265F sounded ridic. I thought I saw a thread where someone shot the ski with an infrared heat gun?

They took on a fair bit of rocker see if it holds.

nice blurry pic for ya.

Pretty ghetto

[El Chupacabra]

End results of summertime Sumo rocker project:

How they were stored, clamped, with a 2x3 shoved in between the tips:




Resulting mild rocker, with 2x3 removed, and clamps still holding skis base-to-base:

[wildskizer]

That's pretty good for not having to put any elbow grease into the job. Must have been pretty hot in that shed. I've got a little over 2 cm. between mine so far, but then that's with a lot of elbow grease. Hell my Mavens are only 35 mm. Any camber left in them?

Cheers

[El Chupacabra]

I didn't look closely at whether I have any camber left in the Sumos, but I only had a very small amount to begin with (maybe 2mm per ski?). I remember the Sumos decamber (press to flat) very very easily.

I'll also have to wait and see if the Sumos hold the rockered shape, or whether they return to normal. I pulled the 2x3 wood out of the skis when I was taking these pictures over the weekend.

[crank54]

So I've been trying to put some tip rocker in an old pair of Mantras that I plan on using for touring this season. I've tried two ~10min heat gun sessions with no effect.

Is there any way to rocker skis with metal in them? Anyone had any luck with this?

[wildskizer]

So I've been trying to put some tip rocker in an old pair of Mantras that I plan on using for touring this season. I've tried two ~10min heat gun sessions with no effect.

Is there any way to rocker skis with metal in them? Anyone had any luck with this?

Yes: Look Up the Thread title; "Powspatuplus: IT CAN BE DONE"All the info you need is there....

Cheers

[wildskizer]

Yes: Look Up the Thread title; "Powspatuplus: IT CAN BE DONE"All the info you need is there....

Cheers

I just bumped the thread...

Essentially you have to control - bend the skis metal layer[s].
I think someone reported doing Mantras. Been awhile since I read the whole thread, so check it out.

[alTAos]

So I've been trying to put some tip rocker in an old pair of Mantras that I plan on using for touring this season. I've tried two ~10min heat gun sessions with no effect.

Is there any way to rocker skis with metal in them? Anyone had any luck with this?

I rockered my xxl's with this technique...heat gun and 2x4's. I think i gave them more than 10 minutes of heat though. Heated probably 6-8" of the ski where i wanted it rockered, pretty intensely right at the location, clamped it as shown and it worked perfectly. I did one at a time also, so I could concentrate as much heat as possible into the ski.

[crank54]

This is the setup I have now with my Mantras. I've had to get way more aggressive than I did originally, as shown by the amount the tips are forced up. I've had them like this for four days, with multiple heat gun treatments (also getting more aggressive), and they now show some nice, gradual tip rocker, starting from right in front of the binding where I have them clamped, though it's maybe only 10mm high at the tip. I'm going to keep going and see how much I can get in them. I'll post after pics when I'm done.

[123ski]

I have some older "blue/grey/green" Prophet 130's without early rise tip. All the new P130's are the exact same ski but with rocker. Wondering if anyone has had success rockering a ski with metal in it like the prophets.

[crank54]

I have some older "blue/grey/green" Prophet 130's without early rise tip. All the new P130's are the exact same ski but with rocker. Wondering if anyone has had success rockering a ski with metal in it like the prophets.

Not sure if you missed something or are just not familiar with Mantras, but my post above ^^^ details what I'm doing now with my old pair. Mantras are wood core and about as full of metal as you get (2 sheets), and I'm having some luck getting rocker in them using the above clamp / heat gun setup. It's a slow process though, and as you can see the tips are WAY stressed - I literally can't pick them up any higher than they are right now by hand.

[crank54]

Ok, I decided the Mantras have enough tip rocker for me now. I really like how they came out, very gradual starting from the front of the binding. We'll see how they ski - no ill effects visible at all, flex still feels great, no topsheet damage etc.

[DudeLebowSKI]

^^^ crank54, That's a SWEET looking shop you have access too. I'm jealous.

[crank54]

^^^ crank54, That's a SWEET looking shop you have access too. I'm jealous.

Thanks, it's the shop at my office that we use for prototyping stuff, etc... It's also handy for things like mounting bindings and rockering skis

[123ski]

Thanks for the info Crank54. That rockering job looks really well done, almost looks like the rocker on the new Gotamas.

Yeah, somehow I must have missed that those were Mantras..or maybe the metal just didn't click...happens when you are scrolling a thread during class...haha

[wildskizer]

Not sure if you missed something or are just not familiar with Mantras, but my post above ^^^ details what I'm doing now with my old pair. Mantras are wood core and about as full of metal as you get (2 sheets), and I'm having some luck getting rocker in them using the above clamp / heat gun setup. It's a slow process though, and as you can see the tips are WAY stressed - I literally can't pick them up any higher than they are right now by hand.

The process you used was designed to rocker fiber glass reinforced skis not metal laminate skis. It probably doesn't hurt to heat up a metal ski, but the altering of the shape [ rockering ] occurs from bending the metal sheets where one wants to change the shape. Unless one has some means of applying a moving force as with a roller perhaps, the metal will only bend at one point of sufficient applied stress.

It appears from your picture that you finally applied enough stress to bend the metal in your skis a little ahead of the toe binder where you had it clamped down. One way to check it is to take a metal straight edge, like a metal yard stick and place it on the base of your ski and see what you have done to it from the point of bend at the toe piece to the tip. I'd be curious as to what you find. If it is just a straight flat line, then you just bent it at one point, and that's not rocker. The "Surface" skis have a straight bend from a point, but that is about half way or less between the tip and toe mount.

It seems to me, as others have stated, that to rocker a metal laminated ski one has to put slight multiple bends in it from the tip back to some point to simulate a rocker curve. This was why I posted to you the "Powspatuplus" thread info, which deals more specifically with rockering a metal laminate ski.
Sumo's and many of the other skis in this thread have no metal in them.

Please check your skis and further update here as to what I mentioned so it is clear to other searchers on what was the result of this process on your skis.

Thanks, and Cheers