Bent Green Things 13/14

[amidnightproject]

Thanks for all the useful information!

Chris: I'll take a look into that too. so you suggest to look at the camber section of the ski in that area to see if there is some "high spots".

Yea I would give it a look over. IT might be very small. Mine was and it didn't take much to smooth it out.

If you are lacking pressure in that area you could take some scrap base and put it between your hose and upper mold. A sheet or two is probably all it would need.

[skidesmond]

I thought the cracking noise came from the epoxy/FG cracking. That's what I was told. It happens in commercial skis also.

[skimann20]

I thought the cracking noise came from the epoxy/FG cracking. That's what I was told. It happens in commercial skis also.

still scares the hell out of me ;-)

[amidnightproject]

I "pre-flex" every set I send out to mitigate that.

I remember flexing some K2 park skis one time at the local shop and we heard a rather loud snap. I slowly placed them back...

Come to find out it's normal. Didn't know that at the time, and I didn't have the money to replace it then!

[skimann20]

I've had shop owners put their knee into my skies to see the flex. (flexing them past any point I'd ever go, i was actually impressed that they would go that far) and had a pop or two and they have yet to flinch at all. "industry standard" I guess.

[sammer]

I've had shop owners put their knee into my skies to see the flex. (flexing them past any point I'd ever go, i was actually impressed that they would go that far) and had a pop or two and they have yet to flinch at all. "industry standard" I guess.

I always try to flex them as far as I can, a week or so after I think they're cured. Takes a few of these flexes before the crackling stops.
Just the epoxy/fiberglass cracking, but yeah it can be a bit scary the first few times.

It's pretty scary watching slow motion of the downhill or any ski events at the Olympics, skis flex a lot! (Snowboards too)

Talking to a composite guy, this is normal and continues to happen on a smaller scale for the life of the composite.
One of my peers, locally, uses 24oz triax, says every flex breaks down the fibers of the ski.
The more/heavier the fibers the longer the life of the matrix.
Eventually the fibers break down to the point your skis are noodles.

I don't know what the average life of a ski is, but I'd be surprised if a normal pair of skis see much more than 100 days max before they are replaced with the latest and greatest.

I've got a couple pair now with more than that, that are still like new using 22oz glass. So my thinking is 24oz glass is overkill.
Eventually I'll kill a pair then I'll let you know

sam

[amidnightproject]

From what I've been told, 70 days is about the average amount of days on a set of sticks, and about 70-100 days of hard riding most skis tend to lose their properties. I've noticed it with some of my older ones.

[skidesmond]

I "pre-flex" every set I send out to mitigate that.

I remember flexing some K2 park skis one time at the local shop and we heard a rather loud snap. I slowly placed them back...

Come to find out it's normal. Didn't know that at the time, and I didn't have the money to replace it then!

HAHAHAHA... That wasn't me, it was like that

[amidnightproject]

Hey man, I didn't break em... Just a loud snap! haha.

[skimann20]

Quick question: when I press my ski the "texture" of the 22oz fiberglass shows through the top sheet. is there a way to eliminate this? I'm thinking a very lightweight mesh fiberglass? I don't see a difference with my layup and the "big boys" besides molds and I don't see a txture showing through theirs. thoughts?

[MontuckyMadman]

type of resin, type or weave of glass, try a veil material if you care. Lots of skis show this. the type of topsheet can play a roll as well.

[twizzstyle]

For a while now I've been placing a 3" wide strip of uni carbon on top of my triax fiberglass (and below the bottom). That has really reduced the fiberglass texture in the topsheet, because the cattrack and top cassette are basically bridging over the CF (if that makes sense). That's my theory anyways - it means the fiberglass isn't getting as much pressure as it could otherwise, but I'm not going to spend the time routing out that thin of a channel in my core to compensate, and my results have been great.

One way to eliminate it entirely is to use pre-cured sheets of fiberglass. I tried that on a pair a few years ago, using some precured sheets I bought from SnowboardMaterials.com. The skis were great, with perfectly smooth topsheets, but they were a little bit heavier than a normal wet layup (not what I was expecting)

[skimann20]

First some good old, o crap moments... not enough suction on the table. FFFFFUUUUUU.... well i've fixed that issue. both errors occurred at different times with different layups.



getting ready to for another pair. this core has the same dimensions as the last pair 2.7-12.7-2.7. However, i put a flat section under the binding area. I'm still working on flex profiles, I think this will put me in a good spot.


HOWEVER.... so I came across some "sample" packages of Victorply fiber glass. I've taken some photos of Vectorply and an other fiberglass company. Vectorply strands are 2.4mm and other is 3.4mm. There is a noticeable difference in the flex of these two materials.



a noticable amount of spacing between the strands of "other" company.


So here is my dilemma, I would really like to use the vectorply in this next pair but then I would be adding two variables to the ski and that would skew my results. Has anyone tested two different fiberglass companies? There is a significant difference between the two fibers and that it is going to have a effect on the stiffness of the ski. Ideas?

After seeing Vectorply, i'm sold!

[falls]

Vectorply is certainly made for the job. Nicer smaller and tighter bundles.
The big thing really though is how much glass is in each direction in terms of affecting stiffness.
I am no expert on glass, but if you have two lots of 22oz glass and both have 10 oz in the 0 degree direction and 5.5 in +/- 45 degree plane then they should give you comparable flex despite having different thickness of their bundles once cure with the same resin.
The big kicker however is that not all 22oz is equal in its distribution betwenn the axes. That will probably be a bigger thing in switching glass. I know my 22oz has more weight in the 45/45 axes than vector ply. So I end up with more torsional stiffness but less longitudinal stiffness and have to make thicker cores to compensate.
I think the tighter bundles help to keep the axes straight which is what gives good strength (fibres excatly alligned in straight lines) and probably helps prevent voids where resin fills the gaps between bundles.
Not sure how it would affect wet out of the glass.

Someone who actually knows may want to comment on how bundle size affects properties of the laminate however

[twizzstyle]

That's a great comparison shot of the vectorply. I've always wanted to give it a go, since I knew it was a tighter weave, but I've just always stuck with the same stuff - I get my 20oz triax from FiberglassSupply.com (located in Washington), and it looks just like the other stuff you have in your picture. Works fine, but that vectorply just looks... nice.

I bet the tighter weave will reduce texture print through on the topsheet too. Tough decision though, if you're trying to change as few variables as possible.