Hi,
some fotos of the skis I put into the press today - hope they come out fine, if they do this will be my future way of building.
Highlights:
- self-routed ski ends made from ABS
- hollow tip
- thin Sidewalls, only 2.5mm thick
- each stringer of the wood core was routed to match the sidecut: Every string is slimmer in the middle equally
- a design austrians will hate :)
> pmg wrote:
- each stringer of the wood core was routed to match the sidecut: Every string is slimmer in the middle equally
Do you have more photos that elaborate on this? I'm having a little trouble wrapping my head around it.
Does this replace your usual method of core construction, where you add the final stringers after routing the sidecut?
Hi, unfortunately photos don't really show it, at least not in my bad workshop light.
But yes, I changed my usual method of just "bending" the outer stringers along the sidecut. Now I use the planer jig to have all stringers in the same shape, reproducing the sidecut when glued together.
In this ski, the middle is 90mm wide, the tip 128mm. Its 6 stringers per ski, 4 poplar, 2 ash on the outside.
In the middle, each stringer is 15mm wide, widening towards the tip, reaching a width of 128/6 = 21,3mm.
Then I routed away good 2mm from each side to make space for the sidewalls, also tilting the wood 8°, the same tilt the finished sides will get.
2.5mm sidewalls are really thin, I hope to find 3mm thick material long enough to use in the future. 3mm should suit my needs perfectly.
Interesting. Thanks for elaborating.
Can't wait to see the finished product and hear how they ride!
First impression is really really good :)
2 little issues I saw on first glance which don't really bother me:
1) One of my base-in-place-keepers moved a little little bit under the edge and lifted it by maybe 0,2mm -> will be gone after the base grind, if not its the outer side of the ski :)
2)I used 320g/m² glass fibres and 120g/m² white flax fibres below the transparent top sheet. The resin was colored with 5% white. Even now on some places the white isn't perfect, so next time I will paint the backside of the topsheet white, my supplier skibaumarkt.de offers a color specially for that.
Compare these 2 issues with the dream I had the night before layup: I dreamt I forgot the hardener in the resin, noticing it when pulling the skis out of the press... That dream sucked!
Tomorrow I will cut the skis out and finish them expect the base, then there'll be pictures.
Cheers
Philipp
> pmg wrote:
Compare these 2 issues with the dream I had the night before layup: I dreamt I forgot the hardener in the resin, noticing it when pulling the skis out of the press... That dream sucked!
Happened to two of my buddies that they mixed hardener GL2 with hardener L instead of resin L, which sucks about equally
So your sidewall thickness is just 2.5mm? I hope you have found a good way to align your cores.
Still I wonder how you deflash your cores and how you manage to bevel the sidewalls.
Why do you build your cores in such a complicated way?
It seems overly complicated.
> SleepingAwake wrote:
Happened to two of my buddies that they mixed hardener GL2 with hardener L instead of resin L, which sucks about equally :)
Ouch! Could happen here too, have these 2 hardeners here as well. Though I replace L with GL1.
@satch:
I think of how the "perfect" ski would be built like in my opinion and try to get there. In this case, I want thin sidewalls because I just need them for humidity protection. Thick sidewalls add weight, remove quite some wood in the core. And yes, I think I have a good alignment method, tomorrow will prove if I am right or wrong - my girlfriend was ill today, couldn't continue building.
I'm really curious about the outcome!
It looks like you have a full thickness sidewall from tip to tail. Is there a reason you don't use the semi cap construction anymore? Do you still Laminate in two steps? What's you lay up going to be?
Sorry for that many questions, but with your Elaborate plans your asking for it ;-)
You do sublim with vacuum? No problems getting wrinkles in the topsheet?
Hi satch, no problem, I will answer gladly (lets be honest, if you post something in the journal section and no one is interested - that sucks!)
I skipped the semi-cap design for one simple reason (and I will soon know if the cap really is the reason for it): When getting colder the cap skis start to have more camber, quite notabe. Another reason is that the 2 press cycle really is additional effort and produces extra waste. And I try to produce as little waste as possible.
And yes, the sidewall is full height, but only 2.5mm thick.
@mammuth: I don't do the sublimation myself.
So I deflashed the ski today, really curious how they turned out. Well, lets be honest: They look great, but they won't last forever because on one side the egde is pretty thin and on the other side the sidewall :)
So really some core shift happened, I still have no Idea how. The interesting thing is that only the middle section moved, which leads me to a theory:
I was afraid of air entrapments under the top sheet when the vacuum pump started to suck. So I tried to "press" the air out by hand, pressing on top if the vacuum sheet. Of course I pressed more in the middle than on tip and tail because thats where the topsheet gets bent over the top edge of the core the most. So maybe my pressure was not only from top but also a but from the side, causing the middle section of the wood core to move a bit.
Also one middle section of the topsheets shifted to the side, no idea how that happened: Tip and Tail are not shifted. You will see it in the photos later.
Hi,
some photos always help :)
The finished ski: on one the protection film is already removed, colors are nice and bright. On the other one you can see the topsheet shift in the middle... looks a bit strange.
Here you can see how thin the rest of the sidewall is - wood showing trough... Won't grind the edge often :)
The white is not perfect despite so much white resin and fibres - will definitely paint the back white next time.
Same here, a bit of the black carbon showing through on the tips. The hollow tip comes pretty nice.
Jeez mate.. you have been busy.
I also need to investigate sidewards preasure when using vacuum bagging.
In my last skis where I used thoes nails to center the cores. I was amazed at the dimples that I got in the bases which shouldn't have been possible without loads of sidewards preasure.
I took steps to prevent that too, by introducing a fold in the vacuum bag between the skis, so it baffled me too.
Nearly forgot to add.. Great looking skis.
When are we going to go for a ski together?
Hi Akiwi,
hopefully soon! I am in Garmisch from 16th - 19th on skiing instructor exams. If you happen to be on the mountain give me a call. Will ride these skis, its my skiing instructors model - a ski for everything.
I used thumb tacks to position the core again, no dimples at all.
Great looking skis! That's a pretty similar layup to what I used in this years free tourer. I just used the heavier UD flax. Up to now I only Hand flexed them and gave them a knock by Hand to hear how they sound. To be honest it sounds pretty much the same as the all carbon ski from last year.
But I don't really mind that. Last years ski work great. And I'm pretty sure that the Wood core plays a much bigger part in terms of dampening
It's a bummer that your positioning didn't work out the way you planned. "Hate to say I told you so" ;-)
Maybe you should use 5mm sidewalls with the next ski. It'll make a ski about 40g heavier but I think it would be worth having that bit room for error.
Hi,
just saw your questions. I re-built that ski since.
1) I didnt use any glass
2) I only used 300g/m² uni flax on top (right below the wooden veneer) as bcomp states
3) 300g/m² triax carbon as before
Result: Perfect! The single layer of flax on top is great, better dampening the very springy carbon.
For durability: The Swiss Ski still skis and skis, no delam, and the ski still skis good.
But: I think that 300g/m² carbon is way stiffer than 750g/m² glass. I never made skis with glass though and cant provide experience on that.
Hi,
Great, many thanks! And good to hear the result was such a success. So did you get even better dampening with the top flax only (as BComp states), compared to one layer below and above the core?
Nice to hear also that your original Swiss Ski is in such a good shape.
Skibaumarkt indicates that 300g/m2 carbon would be approximately as stiff as 750g/m2 glass (they sell both), but that is probably just an approximate. I guess I'll just need to do some testing. In any case, I'm confident that I'll use the type of layup as you have in this version 2.
Best,
Sami
Hi,
yes, 300g/m² on top is superior to the 120g/m² on top and bottom. also way easier to work with. The 120g/m² is a PITA to lay up, the thicker one is much better to handle.
Hi,
I'm interested in your flax experience, can you detail your last built (core thickness, core composition and layup)
My first skis I built last summer were:
140_106_138mm for 174cm
Core: 1.8_9.8_2.4mm made of balsa: Bcomp xq (the stiffer they had at that time, I know it has changed recently)
black locust side walls
Layup
top: 0.6 wood venner
160g Kevlar/carbon (carbon on length direction and kevlar at 90°)
200g carbon biax
120g carbon UD
300g flax UD
core
300g flax UD
120g carbon UD
200g carbon biax
base
They ski very well (largest skis I ever skied so difficult to compare), have a super pop and hold hard snow pretty well even if vibrates quit a bit on icy messed up spring snow. They are aimed to be touring skis, a bit heavy (1625g/ski nude). I decided to put the flax directly on the core with the idea that it would provide a smoother transition from wood to layup (balsa is super soft), I didn't know about the Becomp recommendations to put flax at the exterior level.
My next pair will be 98 large and I want to try a lighter lay up in order to fit more reasonable touring skis specifications. Also I will built my own cores, paulownia, two strings of poplar and black locust side walls.
So yes I was wondering if I could go to:
top: 0.6 wood venner
350g biax flax
300g triax carbon
core
300g triax carbon
300g ud flax
base
thanks,
Aïdan
Hi,
I cant recall the exact numbers, but the last one I built is pretty much this way:
130-88-118
2.5mm - 14mm - 2.5mm; mix of Poplar and Ash
0.? Wood veneer
300g/m² Uni Flax
300g/m² Triax Carbon
Wood Core
300g/m² triax Carbon
Definitely more than stiff enough with this setup, but I like em rather stiff
Thanks for the fast reply,
I can defenetly go lighter in the lay up.
An other thing I will try to achieve in the next built is to have much more flexible tips in order to absorb icy irregularitys we encounter a lot in touring skis, the main default of my first built is that: too stiff tips. To achieve that I will try pure cork tip spacers instead of several layer of veneer as I did (even if it looks great). Which means semi cap (can't have cork directly out). And have a lay up on the tips that has only 45° orientation, no 0°.
cheers
tried to add pics, don't know if they going to show
Having the cork exposed isn't an issue. Have done that on my snowboard last year and it worked well.
