snapping tip spacer joints left and right

[goneskiing]

Hey guys, just trying to get some feedback here. I'm making a 4 dimensional ski with 40cm early rise in the tip. When i look at skis at the shop it looks like they start their 2mm at the end of the sidecut and then go to tip spacer. This would give me about 30cm of tip spacer. Any time i do this i snap the tip immediately. Regardless of materials. My last layup was a 2/10.5/2 core profile with two layers of 11.5oz carbon and two of 8.3oz carbon. Still just snapped. If i carry my taper further up the ski it resolves this issue but then changes my profile at the contact points of the tail and tip. Any suggestions out there? Its frustrating seeing other layups with large tip spacers and i keep snapping mine right on the joint before i even mount it. This has probably happened on the last dozen skis. Or do you guys have a max length your willing to make your spacer? Thanks guys.

[vinman]

I make my tip spacers 150mm and I use an interlock style, a little more work but seems stronger to me.

Are you using a straight transition at that joint or something else?

[goneskiing]

Thanks vinman. Yeah its just a straight cut. How do you interlock it? 150mm seems like a more realistic number for tip spacer

[vinman]

I think there might be something on the main SB website on tip spacers. If not you can take a look at my blog. I think there are pics of my cores and tip spacers.

[MontuckyMadman]

I think we need more info about the resin system and pressures and temps used and the orientation of the carbon and what types.
If you are using no 0 degree then that may be the issue or if you are using a woven composite then you may have trouble.
Consider using glass or something less brittle than carbon in the area you are having breaking issues.
You also must be made of money if you are making skis and they snap and you throw them away.
I would stop and think about this more or get help before you waste any more resources.
Just because you see the tip spacer location on mass produced skis doesn't mean the core terminates there.
Look at the crown skis layup vid, they use huge tip spacer but extend the core into the tip.
If you look at several types of skis the 4frnts to name a few they just use extra composite in those ares to make up the span difference in core to tip spacer transition. Not the best way IMO but made in the elan factory so they have been makin skis for decades.

Who is snapping a dozen skis????

[goneskiing]

Thanks again guys, and I'm glad to hear these answers. Because i kept thinking that other people are terminating their cores that early. I pressed the skis at 50 psi, with 1800 grams of super sap at 180 degrees both sides. This layup was from bottom to top: base material, 11.5oz biax carbon, 8.3 oz biax carbon, core, 8.3 oz carbon, 11.5oz carbon, top sheet. I've tried this process with many different types of materials and each time i assume if i beef up the composites then the seam will stick. When i carry my core further through the tip then it does seem to somewhat help but it seems to only be considerable if i thicken the contact points of the core. I will look at all those sites and thank you again for the help. I'm trying to get my skis (130.104.124) @ 190cm down to 3.5lbs. I'm down to 4lbs so that's why I've been using carbon. I got some additives but haven't used them yet. .. and i keep snapping a dozen skis, haha. Thanks again guys very much

[vinman]

How in the world are you using 1800g of epoxy and getting a 4lb ski. I use around 100g in a 185cm ski with more width. You must get a huge squeeze out and on major mess under your press.

What kind of core?

You may very well have much resin creating a weak/ brittle composite.

[goneskiing]

Yeah there's a good amount squeezing out. But anything under 1500g I was getting delam. And with a clear topsheet it was full of tiny air bubbles between grains. Its a basswood core with two ash stringers underfoot. I have a friend that used the super sap in his layups and he said he really dislikes it. He makes kayak paddles and recommended us composites for their epoxy or west systems. I measure real exact while mixing so i know it can't be poor ratios

[MontuckyMadman]

Vin I think you mean 1000g not 100g.
1500g and delam?
What kind of delam?
Something else is wrong here.
You have no 0 degree axes in your layup.
The biax will only support sheer strength on the 45 and + or - some degrees but not on the straight 0 axis-tip to tail.
I can get a 4.2 lbs ski with ash, maple, carbon, glass, super sap cpm 1000g of resin and veneer topsheet at 188cm at 132-105-121 and it will definitely not snap at the juncture.
Even on our fattest longest skis its not over 1300 grams total.
I think vin might be on to something maybe the laminate is too resin rich.
you are looking for a 70/30 fiber to resin ratio.
I suspect you just don't have reinforcement in the 0 degree and thus the delam and the snapping but your friend is vacuum bagging the paddles I assume, totally different deal.

[goneskiing]

Really. Here's the link for the composites I've been using. I had one snap, like I'm referring to, and one had no tip spacer and i ski'd last week on it with no problems other thean I wanted it softer.


http://www.uscomposites.com/carbonpage.html


The delam was usually in the top sheet, sometimes under the core also where it meets the edge.

How far from your tip does your spacer begin?

And correct on the paddles its vacuum bagged. Something has got to give tho. I really appreciate all the advice

[MontuckyMadman]

Those are all woven fabrics, (other than the uni at the bottom) not what you want to build skis IMO.
Each time the fabric is woven and compressed it makes a crimp and thus you loose any strength, might be stiff but brittle in stress areas.

How did you arrive at using these materials?

Try a 12oz 45+- stitched material, not woven, and a 0 degree uni hot melt or stitched material in a 5oz.
With your core dims it may work out OK, but will be stiff most likely.

The delam is weird, not sure what the issue is, maybe you are not cooking the laminate long enough?
dirty topsheet? no reflame on the nylon? Contaminates in the layup from cleaning solvents or release agents?
we use 10-15cm tip spacer.

[vinman]

Yes meant 1000g.

[goneskiing]

That makes perfect sense. because not only is it snapping on the joint for the spacer but it follows that weave perfectly along the snap.

I don't really remember how I came across it. I didn't know that about the woven though, makes perfect sense. I had gotten some 16oz triax carbon last season and did one layer on the top and one on the bottom. it seemed really thick though and i was nervous that i hadn't wetted it all the way out, because i was expecting a much stiffer result. i did a lot more profile/flex testing with fiberglass afterwards using the vectorply 22oz triax, and then recently started going back to the carbon. i figured if i did mulitple layers of thinner carbon i would know it was wetted out easier. so my paddle friend had recommended us composites because it's where he shops from. my previous carbon layup had used a total of 32 oz of carbon so i figured i'd shoot for 40 oz total on these ones and i came up with the 11.5oz and 8.3oz.

i also have a triaxial 11oz at home that's a free sample that i haven't tried yet. enough to put 3 layers in one layup. but that's braided i believe...actually it even came from braided.com. do you have any thoughts on the braided vs the stitched?

i've got some contacts that i'll pull up tomorrow and try and reach some of the 45+/- stitched biax and the uni seems like its out there pretty abundantly. it looks like vectorply carries the stitched biax in carbon. i'll just have to hope one of their reps at a store can get me a smaller quantity.

as for the delam, i'm not sure if its an issue of cooking for long enough. i tend to keep the skis in the press at 180 for about 45 minutes, i always worry about pulling it too soon. then i pull it and let it rest overnight. it really seems to be just with the carbon layups that i find myself flexing the tip and i can see things seperating. and its not necessarily with the top sheet all the time either....i mean, its not EVERY time, maybe 10%. but its a reason why i put so much epoxy on. especially with the carbon layups, when i use the "naked" from crown i get white patches between a lot of the weaves where it cooked air into it or something. ...maybe my top sheet is too hot and I'm letting out epoxy gasses? ida know.

[MontuckyMadman]

The braider triax stuff is a +-60 and 0 right? Its real high quality. Might work ok, might not.
I sometimes feel like I'm throwin money away but you should reevaluate how you land on these details maybe try and hit up some pros on carbon layups before you go wasting time and lots of resin obviously.
Something we never talk about is the strand density of the glass vs carbon.
Most of the carbon is a 12k and by weight but how many strands does each section of glass have?
I have no idea.
Generally carbon is 3 times stiffer, not " stronger", than glass so you have to downsize the weight of the fabric accordingly, almost.
Carbon is a tough nut to crack.
If it was easy everyone would do it.
Where are you located?
Try and visit a local ski maker and bring beer?
I think my work is done here.
Good luck on this.

[knightsofnii]

get rid of that seam straight across your tips, any discontinuity like that is going to be a weak spot.

Make an arc/moon shaped tip fill/tip, it will disperse the seam and still protect awesome.