no one wants to grind my skis!

sir.orange · Post by **sir.orange** » Fri Dec 16, 2011 11:56 am

i just finished a pair of skis, so i went to switzerland (davos) today to let them grind and trying them out tomorrow.
thw ski servioce stations sent me away because my bases were bend in latreral directions. the guys told me that their grinding stone would be sealed by the massive abrasion. he checked the bases with his caliber, in some spots it was 1mm camber from edge o edge!!

why are my bases bending like that? and how could it be solved?

i pressed with 4 bars, totally symetrical lay up (glass, ash, glass...) constant heat from below and top (little hotter from below to increase the longitudinal camber...worked great)

Richuk · Post by **Richuk** » Fri Dec 16, 2011 12:18 pm

Concave or convex?

I don't think we've pinned this down within the forum, but I wonder whether it has something to do with the density of the core material being different to the sidewall material.

What's the thickness of the cassette and are the bases relatively clean when taken out of the press?

twizzstyle · Post by **twizzstyle** » Fri Dec 16, 2011 12:24 pm

Check your mold. I just pressed a pair that came out very convex, checked the mold and it turns out it had caved in

sir.orange · Post by **sir.orange** » Fri Dec 16, 2011 12:32 pm

it s concave.

if its something with core density it would have turned out convex i guess.

bases are relatively clean, very thin coat of epoxy.

the cassette is 1mm stainless steel, yeah maybe the mdf mould has some concave spots...i m just wondering because the concave is relatively constant over the whole length of the skis

i ll check the mould back in germany

Richuk · Post by **Richuk** » Fri Dec 16, 2011 12:32 pm

That's a damn shame Twizz, any imprint in the cassette?

I was assuming the sidewall material is relatively hard/dense and some of the stringers are softwood? This might lead to extra pressure being applied to the sidewalls, when the softwood compresses slightly. MDF isn't great once you get up to around 80 degrees and a thin cassette adds another issue to the mix.

You can skin your mould with ply or just control camber using heat.

Hope you find a solution!

sir.orange · Post by **sir.orange** » Fri Dec 16, 2011 12:47 pm

Richuk wrote: I was assuming the sidewall material is relatively hard/dense and some of the stringers are softwood?

sidewalls are abs all the rest is ash...we ll see

Sherpa Burns · Post by **Sherpa Burns** » Fri Dec 16, 2011 3:07 pm

Twizz, your mold has caved? As in there are indentations from where the skis were pressed into it formerly? Is your mold vertical ribs of MDF?
I have been using a sheet of mdf laid flat for the running length and it butts up to my tip and tail blocks (vertically laminated MDF). I put a layer of aluminum below the whole thing and is has held up perfectly flat for about 6 pairs of skis now. The first time time I tried this method, I did not have the aluminum sheet (I think it's .050), the laminate left an indent in the MDF at 60psi. Can't quite explain why the aluminum sheet is making all the difference, but not gonna complain.
This method has saved me a lot of cnc work by not having to have all the ribs cut. I still cnc the tips and tails, but replacing a short piece of mdf between the blocks is cheap.

Brazen · Post by **Brazen** » Fri Dec 16, 2011 5:54 pm

How are you cooling them?

twizzstyle · Post by **twizzstyle** » Fri Dec 16, 2011 8:25 pm

I am not using vertically laminated mdf boards, it's a single board laying flat that has been profiled to the camber shape. Tip and tail blocks are still vertical boards. I think thhorizontal board may be part of my problem (I think the middle of mdf is less dense than the outer faces of it, so maybe by profiling I cut into the soft stuff). But the biggie... I shimmed the mold up to get more camber, using lots of Popsicle sticks, but had maybe 3" gaps between the shims... Yeah not smart. Even still, I've skied 5 hard days on thesis so far and theyre amazing!

/threadjack

falls · Post by **falls** » Sun Dec 18, 2011 1:11 am

did you rebate the sidewalls for edge teeth?
I think not doing the rebate leads to concave bases (at least in my experience).

PowderKing · Post by **PowderKing** » Sun Dec 18, 2011 4:41 am

Hey Sir Orange, to wich shop did you go in Davos? I'm more from the Klosters side and one very good shop is Gotschna sport in Klosters. They are very nice and maybe they can help you with the grinding. I'll be in Davos next week so if I see somebody on an awesome pair of skis I know who it is.

sir.orange · Post by **sir.orange** » Sun Dec 18, 2011 3:54 pm

PowderKing wrote:Hey Sir Orange, to wich shop did you go in Davos? I'm more from the Klosters side and one very good shop is Gotschna sport in Klosters. They are very nice and maybe they can help you with the grinding. I'll be in Davos next week so if I see somebody on an awesome pair of skis I know who it is.

hey powderking,
i just returned from davos, was there just for teh weekend, but the powder today in the morning was just great!!

in went to "michel steiner" he was recommended to me by the "fullmoon" guys, as i went there for telemark festival infos.

i guess everyone would tell me the same as to grind 1mm means a lot of abrasion and the hard resin would seal the grinding stone, the consequence would be to sharpe the stone again... what ever, that was the guys explanation.

maybe i ll do the first grind on my own with a rough wood grinder...and if some edge remains, i ll let do a smooth finish on a stone grinder

gladegp · Post by **gladegp** » Mon Dec 19, 2011 3:23 am

From what I gather they shouldn't put the skis on the stone grinder before they've taken a couple of passes on a belt grinder.
Go to a place with a pure belt grinder and get the skis flatter. Then you can stone grind if you really feel you need to.

sir.orange · Post by **sir.orange** » Mon Dec 19, 2011 10:20 am

gladegp wrote:From what I gather they shouldn't put the skis on the stone grinder before they've taken a couple of passes on a belt grinder.
Go to a place with a pure belt grinder and get the skis flatter. Then you can stone grind if you really feel you need to.

yep, that was my suggestion to these guys too. he explained me why not, but he spoke the deepest switzer-german and i did not understandd 20% of what he was saying to me, i am german by the way...

i ll do the belt grind on my own, and we ll see what remains

skibum · Post by **skibum** » Sun Dec 25, 2011 9:17 am

I agree with Brazen's comment. How are you cooling them? The metal edges are a bit heat sync and will cool much quicker than the rest of the material. I cool mine down to room temp immediately after pressing. Otherwise the thickest section of the ski will continue to bake much longer than thinner sections and the edges. Also agree that you need to use a belt sander first. Stone's are only designed to remove a small amount of material. Use an new 80 grit belt first then a worn 80 and work down to a 120. My shop lets me do my own skis because it is not worth their time, I just pay for the belts. So figure out how long your epoxy needs to cure and make sure it is in the press for that length of time (plus a little bit to ensure the material is heated thoroughly. Mine needs 18 min @80 degrees so I bring it up to temp over 8 min and bake for 30 min then put it in the snow. This seems to work for me.
There are many other factors it could be instead but assuming you have read the other comments this could help.
Happy holidays and happy building!

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no one wants to grind my skis!

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