Testing Epoxy sidewall pouring

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pmg
Posts: 479
Joined: Sat Dec 01, 2012 8:59 am
Location: Sonthofen

Testing Epoxy sidewall pouring

Post by pmg »

Hey,

thought I'd open a new topic instead of hijacking the PU pouring thread.

Well, did some first tests with normal epoxy + flex additive yesterday, using:
http://shop1.r-g.de/item/100100
http://shop1.r-g.de/item/130140

Tried with 10% of flexibilizer so far. Result: Wow, this is no epoxy any more! On room temp its more like gum, flexing like hell but going back to the original shape.
It can be be slightly imprinted with a fingernail, but nothing permanent stays. And the surface isn't tacky at all. No chance of breaking it at room temp.

After the freezer its much much harder - much much harder at -20°C. I was able to break it, but only at a deformation you won't have when skiing (unless you hit a rock badly, but then the edge is deformed as well...).

The look is great, added 5% of
http://shop1.r-g.de/item/132130
This stuff is so much better than pigments, mixing is as easy as normal epoxy.
Will post some pictures tomorrow when its daylight again.

Also tried with 10% of cottom flocks:
http://shop1.r-g.de/item/210115
Nice filler, but completely degasing it seems impossible for me at the moment. So will go on without for the moment. Also made the cured resin harder - well, it's fibres after all.

So, what I will do now is test a bit more of the flexibilizer (15%), and will also add some short carbon fibres (3mm). Should make the sidewalls much stiffer, what could be nice for power transmission from the edge to the skis.
Last edited by pmg on Sat Jun 28, 2014 1:54 pm, edited 1 time in total.
pmg
Posts: 479
Joined: Sat Dec 01, 2012 8:59 am
Location: Sonthofen

Post by pmg »

Nearly forgot the negative part:

The resin with the flex additive is very very liquid at room temp. This will be an issue when pouring the sidewalls, going into every little gap it might find. The cotton flocks would e perfect for this, as they make it nice to work with, but the bubbles...
So its either adding thixotropy agent or waiting for the right time to pour. And as my experiences with thixotropy agent arent sooo good i'll think of something else. Quicker resin, perhaps 5% of cotton...

Well, that's what testing is like, isnt it? :)
pmg
Posts: 479
Joined: Sat Dec 01, 2012 8:59 am
Location: Sonthofen

Post by pmg »

Hi,

made a video of a test piece. Its about 12x12mm diameter, as a real sidewall can be like.

1) Room Temperature
http://www.spame.de/skibau/MVI_2253.MOV

1) Fresh out of the freezer at -18°C
http://www.spame.de/skibau/MVI_2254.MOV

The mixture is:
Resin http://shop1.r-g.de/art/100100
+12% flexibilizer http://shop1.r-g.de/art/130140
+6% cotton flocks http://shop1.r-g.de/art/210115
+5% black color http://shop1.r-g.de/art/132130

Its obvious it gets muuuuuuuch harder in low temps, but IMO is still flexible enough.
Is PU also so different in normal/low temperatures?
gav wa
Posts: 381
Joined: Tue Feb 18, 2014 8:58 pm
Location: Perth

Post by gav wa »

That is a huge difference from warm to cold.
There are several different reactive rubbers and polymers used to toughen (add flex) epoxy. Some are very bad at cold temps and this is probably the problem you are having.
Maybe try a different toughening agent. Solid CTBN might be the best option if you can find it.

Another point was raised previously about epoxy being hard to pigment. It is actually very simple and cheap too. Just use 2 pack paint pigments or even pearls.
Here are a couple of epoxy samples using some 2k paint additives I had in my shed.
Image
The blue is just a powder pearl, it also has some chameleon pearl added so it changes color in the light.
Image
The green is actually a tiny bit of candy added to the epoxy.

If you want a really cheap way to add color to epoxy try the little packets of fabric dye. You need to use the stuff for polyester though (usually called Dye Poly). It gives some awesome results, but the color will fade over time. If you use it to make a candy color to paint your car (yes poly fabric dye can be added to clear coat 2 pack to make cheap candy coat) it will fade after a couple of years out in the sun. Would probably last about 10 years in a snowboard/ski sidewall though.[/img]
pmg
Posts: 479
Joined: Sat Dec 01, 2012 8:59 am
Location: Sonthofen

Post by pmg »

My main concern at the moment is that it will get too soft when in the heated press. Will try to heat it tomorrow and see how soft it gets.

Also put the testpiece in the freezer again and tried to break it with all the power I have in my arms - it didn't break ;)

In a finished ski, I would have little trouble with a sidewall that is soft when the ski is warm... As soon as its on the snow that trouble is gone...

Will do another test piece with less flexibilizer (7%) and see how it performs at -18°C.
And I found a good supplier for Smooth-On products in Germany - www.kaupo.de. They have the kilo for less than 25€. Think I will also order some 305 and perhaps I have less trouble with bubbles :)

Regarding coloring epoxy, the color from r-g.de are perfect. Its a neutral liquid that you can easily mix into the epoxy. Will never use pigments again.
gav wa
Posts: 381
Joined: Tue Feb 18, 2014 8:58 pm
Location: Perth

Post by gav wa »

Probably don't need to get too caught up with chasing huge numbers for elongation at break. Why would you need 500% for the sidewall when wood has only about 2%. If you have 10% elongation at break then your board will crack through the core before you break the sidewall.

The change in epoxy with temperature worries me a bit, I mean this stuff is pretty much the main building block for all skis and snowboards. I dont want my board soft and loose on a warm day then a stiff plank on a -25 day.
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MontuckyMadman
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Post by MontuckyMadman »

gav wa wrote:Probably don't need to get too caught up with chasing huge numbers for elongation at break. Why would you need 500% for the sidewall when wood has only about 2%. If you have 10% elongation at break then your board will crack through the core before you break the sidewall.

The change in epoxy with temperature worries me a bit, I mean this stuff is pretty much the main building block for all skis and snowboards. I dont want my board soft and loose on a warm day then a stiff plank on a -25 day.
Wood no good for sidewall
sammer wrote: I'm still a tang on top guy.
gav wa
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Post by gav wa »

MM, I think that's the point I was trying to make. Sidewalls can't be getting put to the point of 100, 200, 300% elongation as the wood core just wouldn't hold up to that, plus the fact wood sidewalls are a common option suggests that skis and boards just aren't put to that sort of stress.

That said I am getting frustrated with the epoxy tests, if urethane didn't need so much attention (degassing, flame passing, pressure chamber etc) I probably wouldn't even be trying it.

During the tests though I have learnt a lot more about how the epoxy resin is reacting to temperature influences during curing so all that is good info to know.
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MontuckyMadman
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Post by MontuckyMadman »

Elongation can also be considered during an impact in a small area. Its requiered to be hard but also bend and avoid cracking. Wood cracks under these impacts in the sidewall beacsue it cant deform or elongate.
sammer wrote: I'm still a tang on top guy.
gav wa
Posts: 381
Joined: Tue Feb 18, 2014 8:58 pm
Location: Perth

Post by gav wa »

Probably don't need to get too caught up with chasing huge numbers for elongation at break. Why would you need 500% for the sidewall when wood has only about 2%. If you have 10% elongation at break then your board will crack through the core before you break the sidewall.

The change in epoxy with temperature worries me a bit, I mean this stuff is pretty much the main building block for all skis and snowboards. I dont want my board soft and loose on a warm day then a stiff plank on a -25 day.
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MontuckyMadman
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Joined: Fri Jun 20, 2008 9:41 pm

Post by MontuckyMadman »

Yeah you dnt follow. The epoxy exists in a super thin layer not thick chunks.
sammer wrote: I'm still a tang on top guy.
pmg
Posts: 479
Joined: Sat Dec 01, 2012 8:59 am
Location: Sonthofen

Post by pmg »

Hi,

gave up the epoxy testing after having a PU test today. The flexible epoxy is just much too much changing with temperature.
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