Top sheet bonding problems

[Tore]

Hello!

We are now finished with making two pairs of skis, and the result was surprisingly good. Everything was almost perfect, the fir core, the 1035 g/m2 fiberglass (a bit heavy, but has many good qualities), and the graphic layer made of black flanel turned out much better then expected. I tried to post some pictures, but wasn't able to do it.

Anyway, I have a quastion about a problem we have. The top sheet doesn't seem to bond perfectly to the flanel layer along the egde of the ski. I can only describe it as half bubbles of air, and there's a lot of them. Do anyone of you know if this is because we don't use a heated press? Could the difference between a heated and a "cold" press be this big?

Thanks in advance for answers. Please tell me how to post the pictures as well if there is interest in seeing them. (It can't be more difficult than making skis?)

[bigKam]

hi Tore:

what was the room temperature when you pressed?
did you notice a lot of air bubbles in the epoxy mixture?
how much pressure are you using?
was the epoxy cold? you can try to warm up the epoxy resin and hardener before you mix...

we notice bubbles on occasion, but nothing like what you describe. when we use a vacuum press there are significantly less bubbles.

oh, about posting photos: you will have to find a place to upload and store them, like some of the free photo galleries available online. be sure that the galleries allow you to 'hotlink' to the photo. afterwards, to include a photo in this forum, add the following to your posts:

[ img ]http://www.photogallery.com/myphoto.jpg[ / img ]

take out the "spaces" in the line above. notice the "http://..." is where your photo is located.

let me know if you still have problems. i'd love to see what you've created and if all else fails, send me a note and i'll be glad to host your photos here...

[Mongo]

On the second pair of ski's I made, there were some slight air spots visible under the durasurf topsheet that I did not see on the first pair. (The ski in the left of the picture)



I think it is because I did not thouroughly wet out the flannel like I did on the first pair trying to save a little bit of weight. Instead I just layed in the flannel after wetting out the fiberglass and the underside of the topsheet hoping the pressure would leave a good color and bonding finish. Flannel has a lot of air space in it, and is very absorbant, so it will suck some of the epoxy away from the bonding surfaces leaving the air spots seen. On my most recent pair, I used Trigger Fabric with a composition of 65% Polyester/35% cotton and got a really good looking interface between the fabric and the topsheet with the same layup process. The fabric was much thinner, and I switched to a thinner fabric based on the great looking results from the Grande Kokoa's use of a similar fabric. Some insight into more of a mainstream topsheet procedure can be found from some questions I sent to a topsheet and graphics specific company called Alkemy Skis (Denver) in a thread here:

http://www.skibuilders.com/phpBB2/viewtopic.php?t=637

Hope this helps. --Geoff

[Tore]

Thanks for the information. Yesterday I wrote a long answer, but when I tried to post it all disappared. I just love when that happands.

Anyway, to answer bigKams questions:
- The temperature in the tiny room where we did the lay up was about 75 degrees.
- We actually noticed a lot of small bubbles in the epoxy, but wasn't able to do anything about it.
- The pressure is enough to make the massive industrial hoses leave horizontal marks along the skis. (Probably because we didn't use any kind og protecting sheet between the skis and the hoses except a thin transparent plastic layer.
- The epoxy had room temperature. We should maybe heat it up a little the next time, but couldn't that reduce the curing time a lot and increase the chance of mistakes during the lay up?

Mongo: We tried to save weight by reducing the amount of epoxy as well, so it might have something to do with that, if the flannel layers really absorb that much epoxy. And when we in addition to flannel use such heavy fiberglass it will absorb even more.

I was suppose to post the pictures yesterday, but it has been snowing a lot in Norway the last week, so I tried out my home made skis for the second time. They actually still work out great! But the pictures will be out soon.