Ski Building for a Composites class.

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corvettecrazy
Posts: 10
Joined: Wed Mar 11, 2009 6:34 pm
Location: Eastern US

Ski Building for a Composites class.

Post by corvettecrazy »

Well I figured I would make a post in the log section to share where my group has come in our ski making process.

To start from the beginning, my high school shop teacher agreed to work with me and CNC the pieces for our mold. (Yes the high school's in the district I went to have CNC routers, among other tools)
The set up
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The results, all the pieces for the mold and a outline of the ski I designed.
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The mold coming together, and my 4 cores sitting on the table next to it.
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Apparently I did not take pictures of quite a few steps between the above and getting ready for layup.

Mold with formica bonded to the wood. As the press we were going to use was basically stolen we had to resort to vacuum bagging the skis. The bonded formica created a nice smooth layer on the mold and epoxy really doesn't stick to waxed formica.
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Because I didn't like the extra space in the tips and tails where the edge tabs were, I cut little pieces to fill those gaps. (Not completely cut out) Also note, the roller cutter in the background is the HANDS DOWN BEST way to cut carbon and glass that I have ever used. Roll it down where you want cut once with a firm pressure and you get a perfect cut.
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Ski in vacuum bag. Which we left overnight. We were not able to get heat into this for the first ski, but we are working on it for the next couple skis we make. (The pump in the picture is not the one we used)
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The next morning, taking the ski out of the mold.
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Mold (not cleaned up yet from sealing the bag down)
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Ski season has pretty much ended here in NY, but from just playing with the ski it is pretty light but crazy stiff. I personally am not a fan of stiff skis, but as a first ski, I am at least glad it came out without too many problems.

Comments and questions welcome.
twizzstyle
Posts: 2204
Joined: Tue Mar 07, 2006 8:25 pm
Location: Kenmore, Wa USA

Post by twizzstyle »

Looks like a great first ski!

What are you using to seal your vacuum bag? Looks like caulking or something, looks messy.

You can get vacuum bagging tape pretty cheap, its a sticky rubber/clay kinda material. (I don't vacuum bag my skis, I have a firehose press, but I do a lot of vacuum bagging with molds for other projects of mine)
corvettecrazy
Posts: 10
Joined: Wed Mar 11, 2009 6:34 pm
Location: Eastern US

Post by corvettecrazy »

twizzstyle wrote:Looks like a great first ski!

What are you using to seal your vacuum bag? Looks like caulking or something, looks messy.

You can get vacuum bagging tape pretty cheap, its a sticky rubber/clay kinda material. (I don't vacuum bag my skis, I have a firehose press, but I do a lot of vacuum bagging with molds for other projects of mine)
Thank you! I spent a LOT of time reading with the hope that the first ski would not be scrap.

We did use a cheap caulk to seal the vacuum bag. It actually cleaned up very easily. More careful application and it would be a lot smaller of a mess than it is. I would love to use a press too, but the one we were going to use was taken from us too close to our deadline to make a new one.


And since I bought all my materials from ski builders and I had a spare shirt laying around....
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corvettecrazy
Posts: 10
Joined: Wed Mar 11, 2009 6:34 pm
Location: Eastern US

Post by corvettecrazy »

Well, made another ski this past friday.

The difference this time is that I made a tunnel so I could heat the air inside hoping for a better epoxy cure. So far it seems to have worked alright. I am not exactly sure what temperatures it got up to as I had no thermometer but It was fun.

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Hopefully I can finish cutting them out today.
corvettecrazy
Posts: 10
Joined: Wed Mar 11, 2009 6:34 pm
Location: Eastern US

Post by corvettecrazy »

Well my first pair is complete and trimmed out. I mounted the bindings last night.

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(The poster is because they were displayed in the innovation festival at RIT)

I can't wait for winter....
twizzstyle
Posts: 2204
Joined: Tue Mar 07, 2006 8:25 pm
Location: Kenmore, Wa USA

Post by twizzstyle »

Your skis look great! Well done!

Any idea why you have so much wrinkling in the top sheet? It doesn't look like you have any breather cloth between the top sheet and the bag material, why is that? You will get more even and complete pressure if you have a breather cloth, and it might help to distribute the load to prevent the wrinkles. You could also lay some thick vinyl or something similar down on top of the ski, then the breather cloth, then the bag - again to help distribute it out and prevent wrinkles.

I'm jealous of your mold, it looks perfect!
corvettecrazy
Posts: 10
Joined: Wed Mar 11, 2009 6:34 pm
Location: Eastern US

Post by corvettecrazy »

twizzstyle wrote:Your skis look great! Well done!

Any idea why you have so much wrinkling in the top sheet? It doesn't look like you have any breather cloth between the top sheet and the bag material, why is that? You will get more even and complete pressure if you have a breather cloth, and it might help to distribute the load to prevent the wrinkles. You could also lay some thick vinyl or something similar down on top of the ski, then the breather cloth, then the bag - again to help distribute it out and prevent wrinkles.

I'm jealous of your mold, it looks perfect!
Thank you!!

We did have a breather sheet, if you look at the picture with it in the mold, you can see that the breather is black cotton fabric. I do believe that I need something thicker but I haven't put too much thought into it yet. I am not sure why we have wrinkles other than the top sheet did not lay flat when going up the curve.

I like the vinyl idea to provide a flat surface on top of the ski. I would also like to try using a top sheet which I have not done yet.

Thank you for the ideas. We have a set of bamboo skis that should be ready pretty soon.
twizzstyle
Posts: 2204
Joined: Tue Mar 07, 2006 8:25 pm
Location: Kenmore, Wa USA

Post by twizzstyle »

There is breather cloth specifically designed for vacuum bagging, its nice and thick, and its pretty damn cheap.

I get mine here (price is per yard)...

http://www.aircraftspruce.com/menus/cm/ ... _film.html
krp8128
Posts: 367
Joined: Fri Feb 23, 2007 1:57 pm
Location: Marcellus, NY

Post by krp8128 »

Hey Rob,

You going to be on campus this summer? I'm planning to make a few pairs myself as an Independent Design Project.

Making a new mold out here is going to be cheaper then driving a truck from Maine, maybe we can figure out a press.
corvettecrazy
Posts: 10
Joined: Wed Mar 11, 2009 6:34 pm
Location: Eastern US

Post by corvettecrazy »

krp8128 wrote:Hey Rob,

You going to be on campus this summer? I'm planning to make a few pairs myself as an Independent Design Project.

Making a new mold out here is going to be cheaper then driving a truck from Maine, maybe we can figure out a press.
I am not going to be on campus this summer. I will actually be in the northwest greater boston area for summer and fall.

If you would like to use the mold that I made for the class, I will be swinging through rochester in a few weeks and could grab it from my storage locker.

I definitely want to make more skis in the future though. Are you going to be there winter quarter next year?
krp8128
Posts: 367
Joined: Fri Feb 23, 2007 1:57 pm
Location: Marcellus, NY

Post by krp8128 »

corvettecrazy wrote:
krp8128 wrote:Hey Rob,

You going to be on campus this summer? I'm planning to make a few pairs myself as an Independent Design Project.

Making a new mold out here is going to be cheaper then driving a truck from Maine, maybe we can figure out a press.
I am not going to be on campus this summer. I will actually be in the northwest greater boston area for summer and fall.

If you would like to use the mold that I made for the class, I will be swinging through rochester in a few weeks and could grab it from my storage locker.

I definitely want to make more skis in the future though. Are you going to be there winter quarter next year?
Just answered your e-mail before reading this.

Yes, I'll be here next winter. I have no idea how much free time for skibuilding I will have though, I should be in my 2nd senior design class by then.

Right now I'm trying to use COSMOS to make sure my new press design won't explode. Kind of hard to figure out, seeing as how ACT is in my near future...
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