Tip spacer stiffness

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Gilo
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Tip spacer stiffness

Post by Gilo »

Hello everyone - I have just acquired some 2mm ABS sheets and was wondering about their suitability as tip spacers - the issue that I have is that they are considerably more stiff than the end of the 2mm core - is this a potential problem? it feels counter intuitive to have the progressively softer core ending in a stiff zone. What's the consensus?

Thanks

Gilo
twizzstyle
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Post by twizzstyle »

The tip is ahead of your contact patch, it doesn't effect the overall bending stiffness of the ski, unless you are doing big nosepresses. Don't worry about it. Your only concern up there should be with good bonding of the plastic.
RYM Experimentals
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Post by RYM Experimentals »

What do you guys see as advantage of using spacers? I take my cores all the way to tip and tail and side to side, makes it allot easier to build and gives a really consistent flex.
twizzstyle
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Post by twizzstyle »

Main reason I use tip spacers (uhmwpe) is I worry the bamboo I use for the cores would have a hard time conforming to the tip shape. The ptex is probably heavier than the bamboo so I'm adding swing weight. While I've done wood (bamboo) sidewalls, I've never done a full tip-to-tail core without tip spacers - it's something I've wanted to try for a long time though!
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falls
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Post by falls »

abrasion resistance and stopping water ingress.
end grain of wood is more likely to split and allow water in when gets damaged than plastic.

That's my theory without having every tested durability of a full length wood core
Don't wait up, I'm off to kill Summer....
Gilo
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Post by Gilo »

Thanks chaps - I shall stop worrying and just get on!

Gilo
MadRussian
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Post by MadRussian »

in the last pair I used black Locust for tip fill. Have no problems. Also I like looks of wood compare to P-tex
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SHIF
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Post by SHIF »

twizzstyle wrote:Main reason I use tip spacers (uhmwpe) is I worry the bamboo I use for the cores would have a hard time conforming to the tip shape. The ptex is probably heavier than the bamboo so I'm adding swing weight. While I've done wood (bamboo) sidewalls, I've never done a full tip-to-tail core without tip spacers - it's something I've wanted to try for a long time though!
RAMP Skis here in Park City use bamboo cores with no sidewalls and no tip fillers. Just core material exposed all around the ski perimeter. I’ve examined their skis having moderate usage and thought they were holding up as well as skis having sidewalls and tip fillers. Certainly simplifies the building process. Having said all this, I’m sticking with my ipe sidewalls and P-tex tip fillers.

Cheers,
-S
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MontuckyMadman
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Post by MontuckyMadman »

I looked at ramps brand new skis and they look like asssss. Their process is flawed no doubt.
twizzstyle
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Post by twizzstyle »

I've also never been a fan of exposed core on the sides - when I've done bamboo sidewalls, they were separate bamboo strips glued to a bamboo core. I want to minimize exposed endgrain for water absorption concerns.
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SHIF
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Post by SHIF »

MontuckyMadman wrote:I looked at ramps brand new skis and they look like asssss. Their process is flawed no doubt.
I totally agree with your statement. I saw their entire building process and was not impressed. Their skis are certainly not up to our high standards. I was actually quite surprised that the few used pairs I examined were holding up very well despite the lack of sidewalls and tip fillers.

-S
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falls
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Post by falls »

the problem I find so far with bamboo sidewalls as part of the core is the exposure of the inter laminar glue lines on the finished sidewall if you cut the sidecut out of it. The dodgy drawing below highlights what happens to glueline exposure on the sidecut. This isn't an issue with a sidewall glued onto the sidecut as it follows the curve.
Further to this when you apply the sidewall bevel you can then exposure linear glue lines too in the other plane. It isolates small islands of bamboo laminar that have pointy ends and minimall top and bottom surface area for being held in palce.
This problem has been most pronounced in the rear sidecut esp right at the tail where the pointy ends are facing straight into the snow as you ski.
I have had small pieces lift out of the sidecut in the position where corss hatching has been applied in the sketch. Not fatal to the ski but not great for cosmetics. (actually just in tail where the high abrasion of drag meets the pointed pieces of bamboo).
If you cut a linear strip of bamboo and bend it to the sidecut you avoid this situation. Depending on how much angle you put on the sidewall bevel you can still have the horizontal glue line exposure.

Finally you also have to be careful when bevelling the sdiewalls that you don't rip it along a glue line with the force of the router (when in the tail area of sidecut) and tear a chunk out - doing 7, then 14, then 21 degrees and building up slowly has solved this for me. (I also have trouble when shapeing the cores with the router of glue line separation on the bamboo - the more aggressive the sidecut the worse the problem - always when in the tail area of sidecut purely due to router physics)

FYI: Ramp build video https://vimeo.com/83536909

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