I sacrificed a ski tonight .
I wanted to see how easily it would delaminate so I held the ski upright by the tip and pressed on the center with my foot. I released the tip and let it hit my asphalt driveway (similar to the test in a Karhu factory tour vid).
Suprisingly nothing happened the first time. The second time the fiberglass delaminated from the edge/base layer. About two inches in from the end the bottom layer of glass delaminated from the wood core.
Have the people using composite tip spacers had a delamination problem like the rest of us? Any thoughts on how to prevent this?
I have tried ending my wood core about 2" short and having the two glass layers meet. Becasue there are fewer layers to bond I felt my chances of delaminating would be less. Still waiting on some snow to try it out.
Geez Louise, man, that was a ballsy move. I had a moment of silence in observance of the sacrifice. I'm not sure I could face that test myself. Good things learned though, eh.
It's often difficult to get a good sense of these problem areas from a verbal description. Any chance of seeing a photo of the delaminated areas? In lieu of a photo, am I understanding correctly that the base material separated from the fiberglass?.. or was it the tip spacer material that delaminated from the glass? If it was the actual base material, that is interesting because it would indicate a surface treatment deficiency of the UHMW that came from the factory already abraided and flame treated. If the separation did not penetrate too deeply, the bond weakness could have originated at the metal edge/glass junction, maybe due to the steel edge not being properly prepped, then the delaminaton just propagated a little way into the base material . Did you sandblast the edge before super gluing it to the base?.. and not touch the edge after sandblasting except to wipe it own with acetone (while wearing rubber gloves)? But if the above described delamination was a full depth separation, then I'd say that there must have been a problem with the surface flame treatment of the UHMW, an improperly cleaned base prior to lamination/pressing, or a problem with the epoxy. I don't remember what formulation of epoxy/hardener that you are using. If it was the tip spacer that delaminated from the glass, I think that I read recently that the K's have had a problem with this also. I have not had a problem with the tip spacers, but, I use 2mm tip spacer that comes from Durasurf abraided and flame treated on both sides. Is that what you use? In terms of the epoxy, are you using a heat cure formulation? If it doesn't get fully baked at a high enough temp, it is very brittle and, when stressed, sort of crumbles into powder.
The fact that you also had a problem with the glass delaminating away from the wood leads me to believe that it's an epoxy problem. The wood/glass bond should be very stong unless the wood surface was too smooth and non-porous, or, again, if the epoxy failed.
I think G-Man has it right with starting to look at your expoxy first.
Before that, just check that your parts area is clean and that nothing could have been contaminated.
The final thing I'd check is parts placement or design, as it is always a pain to have to rethink templates.
I don't know if you have a "troubleshooting checklist" but I've always found one to be handy to reference to keep my head.
The wood core to fiberglass "connection" seems to be prone to bad saturation in my experience. You might look at resin amounts for each area and layer of your process. Also, look at our materials.
I don't know what you are using for a topsheet, but some topsheet materials can actually resin starv the layers beneath them.
In the evolution of all parts placement and designs I've layed-up; all headed in the direction of complete glass coverage over the core and tip/tail.
Sometimes delams happen because either you have a delam curse on you (and it will seem to only happen to you--no-one else using the same press, parts and molds will seem to have the problem) or, you are just unlucky.
I've lived with the curse quite a few times. I'm not willing to believe I'm unlucky (who'd I blame?).
Oh, something that I forgot... did you use VDS? Because it supposedly reduces shear forces between the lanimations, not using it could exacerbate the inherent forces encountered when getting slammed against the asphalt.
I've seen the results of VDS over time. I have never been very satisfied wtih the data I've seen. I think the safest thing I can say is if you see delamination and are not using, try using it. If you aren't using it and have no delamations, then don't use it.
I ran a few production runs over 18 months were we were "rubber crazy"---we and everyone in the industry thought it was a "must have"--that is until we ran out and still needed to meet quota. None of the production runs completed without it ever showed any delamination problems even in warranty records. I can say that we did significant materials changes during the runs. So, the culprit was probably in another one of the other areas or materials in the mix. Since we made those changes when we had thought we had fixed the delam problem with VDS, we didn't think to validate that.
I say "go figure?"
I'd love to hear about other people's experiences with it. I am still open to new information. In my experience, I just don't think I ever saw the kind of data I would like to make a decision one way or another.
Good thoughts from real world experience. I have so many plans to do this battery of testing and that battery of testing... just not enough time in a day... speaking of which, it's almost 11 pm and I haven't had dinner yet... yikes.
The first pair I made with composite tipspacers (7 layers of fiberglass) delaminated in the terrain park one day when the landings were icy. My other pairs with fiberglass tip spacers have not delaminated yet, but they only have 3 or 4 layers of fiberglass at th tips so they are a lot more flexible. With the pair that delaminated, I squeezed in some epoxy betweeen the layers and riveted them up. It has worked like a charm so far. So, I know it is kind of sloppy but "If in doubt, a few rivets will usually solve the problem".
Just to throw another monkey into the works,
If you try everything you can think of and still can't cure a delam problem, look at your materials.(a good practice is to keep a journal of what you are currently using on your current ski, which products and companies made them and how they came to you).
You would be surprised on what kinds of 'releasing agents' cant get on materials through the production process and transport.
Hydraulic fluid is quite common---fork lifts.
Some suppliers "repackage" materials that other customers send back (this includes resin, believe it or not--even stuff that has been partially used).
I had some more time yesterday to look into how the ski delaminated. I feel that I have a couple problems going on.
First off, I have a feeling that the glass did not adhere well to the edge. I did a quick wipe down with thinner however this may have not been adaquate in removing all the oils from handling, etc.
Secondly, its seem as though the glass that delaminated from the core was starved for epoxy. I have a hunch that the wood sucked it away from the glass. I used a thinner epoxy this time which may have caused this problem. My glass top sheet also was abnormally staved for epoxy.
I forgot to mention that I did not use any tip spacers on this ski. I will get some pics up asap.
When I talked to the guy at (CDW?) about edges, he claimed that the bond between the steel edge and the fiberglass was the common starting point for most delamination.
He advised that you should at least use a sandblasted edge in order to create some texture for the bond. He advised (of course!) that his specially coated edges were much better at bonding. The only downside being that the coating will burn off if heated, so you must bend them cold.
I haven't tried bending my edges yet, but there are conflicting opinions on this site about the feasibility of bending edges cold.
Keep in that I really had to abuse the ski to get it to delaminate. It was no easy task. I agree that the bond against the metal edge is probably the weakest however it is still fairly strong. I am a little more concerned about the glass delaminating from the core.
I would recommend a sandblasted edge over a primed one. As far as bending goes...it is a PITA to cold form them. I have been getting them pre-bent from CDW then "tweaking" them on my own. This has been the easiest method I have found
Yeah, I get the sandblasted ones. I send them a cut out base and they bend the edges to that. I still have to do a lot of bending and trimming but their bends are a good starting point.
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