Ski Bending - help...

[Boulderski]

Hello hoping to get some input on my ski build design and problem solve some issues with my build.

I have been pressing skis for a few seasons now - mostly following examples I have seen on here to learn the ropes. This season I tried to branch out and make my own unique design (layup and topsheet) but I am running into a few issues. My ski layup is different - sort of vertical and horizontal lamination in one.
This pic will give you a better Idea of what I mean:
http://s19.postimg.org/fn52udbnn/IMG_1991.jpg

Layers of the ski:
Topsheet: Maple/bamboo veneer with epoxy coat (doing coat in press now)
1 Glass - 19oz
2 Titanal Mount plate with VDS on each side (20in long)
3 Glass - 12oz (not tip to tip just covering maple below)
4 Maple veneer that goes just shy of contact to contact
5 Glass 12oz (only sightly longer than vertically laminated boo core 95cm)
6 Vertically laminated bamboo core under foot ( 92cm)
7 Glass 12 oz full leangth
8 Maple Veneer full leangth with tip and tail spacer at each end
9 Glass 19 oz
Ski base... edges and vds

Epoxy: entropy CPM
Glass: 19oz is triaxial and 12oz is biaxial

Why: SO Yes the ski is a bit on the heavy side but it has an awesome flex pattern and I really enjoy riding this ski! I have made several variations of this model but this the general layout above. I grew up a park rat and then began venturing more into trees and BC... but I always loved the Maple Skate style layup of the line Afterbang (a burly park ski) and I wanted to incorporate some of that style with a bamboo core.

Dimensions: 177cm long and 132,102,125

Problems: I work in a ski shop and have been leaving my skis there and letting the homies test ride them ... and the last 2 skis I have built the camber under foot went flat and the rockered tip is now sticking up really high. I know some of these guys do pretty hard nose butters and they are constantly grabbing my skis and flexing them - but still my ski needs to withstand some ABUSE!
http://s19.postimg.org/crrzni7nn/IMG_1992.jpg

Would love some input - Ideally I would like to improve on this concept but I am open to hearing that its a bad idea. THx Guys

[Boulderski]

I have a few theories as to why the ski bent so much at tip... before I begin explaining here is another pic of the worst ski bend I have had. This ski is all 12oz glass (trying to get weight down) and it bent really bad. So in the pic you will see 2 sets of skis. They are different models but they should have contact point at the same point on both sets of skis but as you can see the bottom ski in the pic is bent to hell before contact point.
http://s19.postimg.org/rp5229a9v/IMG_1994.jpg

So my theories
1 12 oz is to thin and I should use atleast one 19 on each side of core - which I did on last build and had some improvement
2 epoxy mix was bad and maybe not enough hardner (just started using scale - I was using pumps)
3 The design with having only 2 layers of maple (topsheet and base maple layer) and 2 layers glass is too thin. Each layer of maple is 1.7mm so 3.4mm thick of wood from contact to tip). When I caliper this section base to topsheet it comes too 6.6mm thick (doesn't seem to thin)

4 my 180lb buddy laying into my skis doing a nose butter: http://s19.postimg.org/lf9sf9av7/IMG_1962.jpg

Ok 4th reason doesn't count my skis need to be able to handle that but figured it was a good pic to share

[MontuckyMadman]

How are you pressing and at what pressure?
Are you useing heat to cure top and bottom?

[Boulderski]

I am pressing sandwich press at 45- 50psi heated with one blanket underneath aluminum cassates at 180f

[MontuckyMadman]

This is pretty confusing but if u dont have uni composite on both sides of the core this deformation is mostly inevitable especially if you have horizontally stacked portion of the core in my opionion.
Orienting the fibers in a full vert lam changes the mechnics of the deformation of the laminate especially the woodishy parts.
Try a full bamboo core thin it out and stick with your composites I think you may have similar ride results. Or maybe you just need heavier uni firbers maybe some carbon tow.
Make sure u mix ur entropy very thoughely. Stir it for atleast 2 min.

[Boulderski]

Thx - sorry took me awhile to get Back to this thread broke a few ribs skiing this week😞
I get what your saying with not having vert lam going all the way down ski... Do you think if I switched composite layers and had some sort of uni directional composite on each side I could get away without leangthening bamboo?
Probably leangthening bamboo is best fix it just adds so much prep work profiling it down.

Thx for response,

[Akiwi]

If you want to add some Uni directional fibres, but don't want to add an entire layer, I bough a 2m long sheet of Uni directional Carbon, and cut it into strips. Is much better than using Roving.
You can selectively select where you want to add some extra strength

[heke]

If you want to add some Uni directional fibres, but don't want to add an entire layer, I bough a 2m long sheet of Uni directional Carbon, and cut it into strips. Is much better than using Roving.
You can selectively select where you want to add some extra strength

I don't know about the skies, but with widsurf & kite boards there is risk of breakage if the carbon strip is not full lenght?

[Akiwi]

If you want to add some Uni directional fibres, but don't want to add an entire layer, I bough a 2m long sheet of Uni directional Carbon, and cut it into strips. Is much better than using Roving.
You can selectively select where you want to add some extra strength

I don't know about the skies, but with widsurf & kite boards there is risk of breakage if the carbon strip is not full lenght?

You can add it full length, it just doesn't need to be full width which might be adding unnecessary weight.

Wit regards to loosing camber / rocker, have you tried letting the skis cool down comeletely in the mould. I have experiences with longboards that if I heat them and take them out of the mouls when the epoxy is still warm, that it is softer than when it cools down, and they loose some of their shape.

[Boulderski]

Cooling - so yes I allow my skis to cool in press for 45min after pressing with heat for 30min at 180f. I found that if I pulled them early my bases would not come out as flat.
So as soon as I heal up some more I am going to try and do full leangth vert bamboo (broken ribs suck - I just sneezed and I want to cry!)
- I will also try the half vert bamboo I have done in past builds and try some sort of uni Carbon - anyone have any suggestions as to where to buy and thickness?

Also I have been doing a titanal mount plate - if I extended it past contact points this could add strength but I feel like if the ski did start bending this would only facilitate the process right? I'm just beginning to learn about using metal in ski ... But as a ski tunner I have seen a lot of bent metal skis. Last year some lady brought me here mantra with a half foot of rocker in it - she hadn't noticed it was bent and wanted a tune - ha wax fixes everthing right!