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Types of Carbon Fibre


DUSkier
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Is vibration an issue in waterskiing? Water is intrinsically good at damping vibrations. While wakes and chop cause vibrations, I'm not sure that the water by itself allows the displacement to propagate.

 

I build for stiffness and light weight. I set the rocker in the mold and add enough material to have it stay there while skiing. Controlling the flex of a ski could improve skiing performance but honestly that's beyond my skiing and design capabilities. Note that my skis suck in rough water. Adding weight (from screwing up the layup) made the skis better in rough water and gave me more consistent scores but took down my top scores. The heavy skis were just as stiff. But maybe the extra resin did some internal damping. I liked the consistency but hated having my top scores limited. Light and stiff gives me more potential.

 

I quit experimenting with resins when I found the Applied Poleramic resin I use now and my rate of ski breakage went noticeably down. Still, I have some flexible epoxy resin to play with - but I was planning to make boots with that stuff. Hmmm, maybe a strip of cloth with that resin would do good things for not too much weight?

 

Eric

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From that video - they aren't using a type of carbon fiber - they are using some other material as a layer within the lamination.

 

I would consider the difference between a ski - with a sandwiched core that could provide your dampening, to a hollow carbon fork/frame.

 

Recall Obrien used to have the Kevlar skis.

But I'd be interested to hear folk's thoughts on

Kevlar

Spectra

Carbon

Basalt Fiber

Fiberglass

And Boron.

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@BraceMaker‌ I've played with a few of these materials.

Kevlar: I can't get it to work. Hard to wet out with resin and compressive loads seem to dislodge the resin out of the cured matrix. I'm using the wrong resins or cure processes or something. It is very light. I do use it in spot locations to retain screws and inserts.

Spectra: a more expensive cousin of Kevlar. Since I don't like Kevlar, I haven't spent money to try Spectra.

Carbon: Black magic! Very light and strong. Expensive but affordable. Easy to work with (maybe not as itchy as glass). Only drawback is that it is much weaker in compression than in tension. Makes the design more complex.

Basalt fiber: I've seen it marketed as a high temperature product. But I've never seen or played with it. Might be fun to make a basalt/aluminum composite.

Fiberglass: The original magic! Reasonably cheap. Easy to work with. Relatively light. Relatively strong. Tough. A wonderful product. I use some in my skis. Carbon is lighter and stronger so It's not so cutting edge.

Boron: Great for reinforcement. Light, strong (both in tension and compression) and stiff. Ridiculously expensive. Nasty to work with - the splinters are horrible. Complex shapes might be a problem as the dry fibers don't like sharp bends. I'm trying to figure out how to do a precured sheet to use in my skis - the dry fibers are just too unpleasant to work with. The boron fibers solved many issues in my skis so I'm kind of committed to them.

 

I'm pretty low tech with room temperature epoxy, low pressure presses and fudgesicle stick stirrers in red beer cups. I'm sure people with vacuum bags and autoclaves will have different experiences. With that said, I have been sucessfully doing this for a long time and have optimized my materials and processes (a shout out to Applied Poleramic for solving my resin problems). My skis rock!

 

Eric

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A few years ago I had some pre cured carbon fiber unitdirectional with peel ply on both sides. That unitdirectional was autoclaved and pressure pressed. It had better properties than my wet layups. It was easy to work with and reinforce specifically where the ski needs it.

 

I want that in Boron. I might have to do a wet layup just to make pre cured Boron sheets to make it easy to handle but I'd like to get the properties from an autoclave.

 

Eric

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Thanks Guys, this is an area I know VERY little about (and am sure others are the same)

Is vibration an issue??? In rough water would this help the ski settle into its sweet spot??? Our site can get a little rough on the pull out at one end and teeth chattering and blurry vision in the glide can be a bit weird =)

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Instead of building a ski for rough water, perhaps you could bolt on a vibration damper. I can't remember the company name but someone is making a damper that is ball bearings in oil. They claim that this works well to reduce vibration and add stability to snow skis. Perhaps this could help in your specific situation. When you get to smooth water you have the option of removing the device and getting the ski as the designer intended.

 

Or you could soften your knees a bit, edge a bit more aggressively and adapt your style. Not nearly as much fun...

 

Eric

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@‌eleeski

 

You maybe know all of this before but just in case some one can use the advice:

 

My friend use to build Epoxy / carbon fiber airplanes.

The wing profile had similar size as a ski.

He used to create vacuum to get minimum amount of epoxy.

The method is very cheap and simple!

Build the ski on the mold.

Wrap Polyethylene (?) plastic (same material one use for houses to keep the humidity. Just a bit a bit thicker than floor folio used for painting)

Use tape to seal it.

Create the vacuum using a vacuum water pump.

They are connected to a garden house or similar and consume type a half gallon per minute

It will give you type 2000 pound per square feet of pressure.

 

If you heat the ski during hardening it will become stronger.

Suitable is 60 C (type using a heater fan on max under some blankets).

 

 

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@gsm_peter‌ Sigh. I know I should try to upgrade my process. I did buy a vacuum pump a few years ago but I struggled to get the vacuum bagging to work as well as my airbag (I get at least half that much pressure pretty easily and I get pretty good laminations). I used to heat to about 90c when I used pre preg and honeycomb but that kind of heat melted the foam when I switched to foam. My current resin is designed to give most of its properties with a room temperature cure - other resins I've used do require a post cure heating. Most of it is that I'm a bit lazy and have a process that works. I'll have to get creative when I switch materials, cores, resins or processes and will certainly consider using some of your ideas. My mold is at the airport so I'm pretty sure I can find some homebuilders to assist me when I change. Thanks.

 

Eric

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FYI Carbon Fiber is not one product. It comes in many forms, qualities and properties. I have seen the carbon stock in a few factories. Not everyone is using the same stuff and I know that factories are looking for an edge with different carbons.

 

if you want a brain bender... one measure of Carbon fiber is modulus. http://en.wikipedia.org/wiki/Young's_modulus

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