So as some of you remember a couple of months ago I made up some sample layups to break. This is the original link: <a href="http://www.wakeworld.com/MB/Discus/messages/65919/545968.html" target="_blank">http://www.wakeworld.com/MB/Discus/messages/65919/545968.html</a> <BR> <BR>So we have tried two different loading scenerios. Both of them had a 1/2" of soft silicone on them. This seems to even out the load a bit and the thought was to simulate what the water is doing to the bottom of the board. Neither of the samples failed correctly though. The particular layup we are testing here I know on the water either the top skin fails in tension or the bottom skin fails in buckling. Where what we see in both of these videos is the core shearing away from the skin. So at this point I am trying to figure out what to change to get it closer to reality. We have posted the videos at the bottom of our engineering page. Give them a few minutes to download. One is like 7 megs and the other is 12. <BR> <BR><a href="http://www.cdifins.com/Engineering2004.html" target="_blank">http://www.cdifins.com/Engineering2004.html</a> <BR> <BR> <BR>Skiing made me board, <BR>Lyle <BR>Chrome Dome

Lyle, <BR> <BR>This isn't related to your design and testing methods, but it might help in seeing what is actually happening in your testing: <BR> <BR><a href="http://www.casio.com/products/Cameras/Exilim_Pro/EX-F1/" target="_blank">http://www.casio.com/products/Cameras/Exilim_Pro/EX-F1/</a> <BR> <BR>This camera can shoot 1200 frames per second video and 60 frames per second photos. <BR> <BR>Here are some sample videos: <BR> <BR><a href="http://www.exilim.com/intl/ex_f1/features2.html" target="_blank">http://www.exilim.com/intl/ex_f1/features2.html</a> <BR> <BR>It's not cheap @ $999 but it sure would allow you to see what is going on better. <BR> <BR>jjakober

what kind of process are you using to connect the skin to the core?

In my experience and testing your results are correct. The core is going to weaken or fail first resulting in the outer skin failing. You will need to bond the top and bottom skins together to correct this problem. Either a stringer system or a differnt type of core material. Nida Core Structiso is a cool concept but is used with infusion. <BR><a href="http://www.nida-core.com/" target="_blank">http://www.nida-core.com/</a>

jjakober, that is a sweet camera and would be great for this application. <BR> <BR>Andy, the carbon fiber is layed up with epoxy resin then vacuum bagged together. <BR> <BR>Phaeton, <BR>The problem is in reality this is not what happens when this particular layup fails. This is the exactly layup I have used on the last 4 boards I have made. When they fail it will be either a tension failure on the top skin (bottom in this test) or a compression/buckling on the bottom. Where as can been seen when you play either of the videos frame by frame the skin is actually shearing away from the core. <BR> <BR>Skiing made me board, <BR>Lyle <BR>Chrome Dome

Travis sighting! Sent you an email buddy! To the sky ski email that is....

Lyle correct. It all boils down to a core bonding failure. We have the same issue in our industy. We have a testing Dyno that repeatedly puts pressure and records the data. The only fix we can make work in our tests is to have the top and bottom sheets connected to each other with either a stringer system or the Nida Core stuff. Of course there are other way's but this is the lightest we have come up with so far. <BR> <BR>Hahn email sent!

jjakober: actually thats pretty cheap for a camera like that. Its not very powerful compared to some SLR's but the speed alone they could of sold it for alot more. I spent alot more than that on some of my lenses. <BR>But what I would suggest to lyle is contacting your nearest film camera specialist and renting something like this for the afternoon: <a href="http://www.highspeedimaging.com/fastcam_SA-1.cfm" target="_blank">http://www.highspeedimaging.com/fastcam_SA-1.cfm</a>