new skibuilder

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Richuk
Posts: 1146
Joined: Sun Jan 31, 2010 9:53 am
Location: The Duchy of Grand Fenwick

Post by Richuk »

Your almost there on so much of what you are doing. Hope the following helps:

- watch the boheme video's for a different approach to attaching the edges
- pull back of the depth of the rebate, you'll get a clean finish on the base
- bonding UHMWPE: define grit level, use MAPP gas, bond per Boheme method or within then press before it is used
- exclude wood with knots, the bond is weak and or results in an over concentration of epoxy
- modify the approach you are taking with the core, 'Montucky styleeeee', if you luv wood, drilling the core is just like stabbing yourself in the heart
- CF needs to be straight - its worth thinking about how it call be held in tension before the cassette is closed - you don't need to send to all the way to the tips.
- Make sure you fibre is super dry before it is used - over night in the airing cupboard is a good idea in this instance. You will need to consider how you work this epoxy into the fibre or elevate the temperature you are working at. You might have a problem with compatibility - so speak to your suppliers. Once the fibre is correctly saturated, then pressure will only affect the fibre ratio.

Good luck
szymon
Posts: 24
Joined: Wed Dec 09, 2009 3:32 pm

Post by szymon »

Thanks Richuk and Jellyfish!
Richuk wrote: - pull back of the depth of the rebate, you'll get a clean finish on the base
what do you mean by that? what's the rebate?
Richuk wrote: - exclude wood with knots, the bond is weak and or results in an over concentration of epoxy
I'm taking only spruce with knots - as it's not "important" wood in skis (soft and not with good pop). When using ash, I'm never taking with knots. And for spruce - you think it's a problem with knots? Dou you think it's better to glue parts without knot than using long wooden stringer, but with knots?
Richuk wrote: - modify the approach you are taking with the core, 'Montucky styleeeee', if you luv wood, drilling the core is just like stabbing yourself in the heart
What do you mean by that? I'm not drilling the core anywhere...
Richuk wrote: - CF needs to be straight - its worth thinking about how it call be held in tension before the cassette is closed - you don't need to send to all the way to the tips.
I'll think about that... doesn't seem so easy to do it.
Richuk wrote: - Make sure you fibre is super dry before it is used - over night in the airing cupboard is a good idea in this instance. You will need to consider how you work this epoxy into the fibre or elevate the temperature you are working at.
I'm always super aware of that. I put all the cut fibers on the heater for the night.
Richuk wrote: You might have a problem with compatibility - so speak to your suppliers. Once the fibre is correctly saturated, then pressure will only affect the fibre ratio.
I think compatibility is not the issue, because It was bought together from the same supplier and it is used together often.
I think the solution can be as jellyfish wrote - viscosity
jellyfish wrote: Looked at your resin low viscosity and a long time to gel is very similar circumstances to a cold cure, this is how it looks to me your fiberglass reinforcement outside the ski is saturated and even puddled, your resin has a viscosity of 700cps at room temp now heat it up to 60*c and my guess it is like water give it 40 mins under pressure and your resin was pushed out of your ski before it cured. This is how it looks to me.
I think this can be the issue.
I tried to press some samples today at 50psi, we'll see.
I'll also try to find other epoxy with higher viscosity.

Anyone now where can I buy ski-specific epoxy in Europe? I know it should be easy, as many manufacturers are here, but I can't find good suplier for ski-specific epoxy.

Best to you all!
Richuk
Posts: 1146
Joined: Sun Jan 31, 2010 9:53 am
Location: The Duchy of Grand Fenwick

Post by Richuk »

Most people rebate the sidewalls to create a space for the the edge set. It looks like there is too much epoxy on your bases (around the edge set) - can't quite see properly. This could result from the depth of the cut - sometimes less is more. If you are not rebating the core, you might want to research this issue.

Knots - less likely to get a good bond, epoxy within the knot is likely to fracture. Long term it's not a great choice IMHO, as I would expect delamination, particularly when subject to compression.

I understand you have an issue with the core moving in the press. MM has offered a good solution, which means you don't need to drill the core. It's a variation on the theme you have already tried.

It's worth doing a bit of research within the forum on epoxy, it will help you determine which epoxy you want to try next.
rockaukum
Posts: 558
Joined: Fri Nov 03, 2006 9:23 am
Location: Placerville area

Post by rockaukum »

Just checked back in and saw a question about how I locate the core...
I use something called a standoff found in Grangers catalog. It is used for circuit boards and come in various sizes. I hot glue them to the ski and drill the core. I place two per ski or board one in front of and one behind the binding area. In this post there is a pic that you can see them. they are small and plastic
( viewtopic.php?t=1786&view=next&sid=b668 ... e4fb1c02d3 )
ra
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