I am working with a local wood worker to develop a way to easily profile cores. The idea we have come up with is to make a fixture where the ends on the "blank" are raised and the center is sucked down by his vacuum table. A cnc router then makes flat pass across the top (which will be the bottom of the ski) creating the entire profile....
With this method we should be able to profile 5 pairs of skis in one pass.
Any thoughts on this method? Unforseen problems??
New Profiling Method
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wouldnt the flat pass be the top of the ski (once the vacuum is released and the core rebounds)? also, without sealing the gap between the end risers and the middle of the core (where it actually touches the table) how will the downdraft actually hold a vacuum? Maybe a concave mold with vertical air holes would fix this (for the blank to bend into flush) Last, considering a blank can start at 5/8" thick it could be very difficult to flex with a vacuum. I know vacuum bagging 1/16" rock maple veneer is almost impossible into tight curves. Granted this isnt a tight curve, but its also 10 times the thickness. But if it does work, a vacuum table will be next on my list of things to build 
Yea, that would be the top. Dunno what I was thinkingmattman wrote:wouldnt the flat pass be the top of the ski (once the vacuum is released and the core rebounds)? also, without sealing the gap between the end risers and the middle of the core (where it actually touches the table) how will the downdraft actually hold a vacuum? Maybe a concave mold with vertical air holes would fix this (for the blank to bend into flush) Last, considering a blank can start at 5/8" thick it could be very difficult to flex with a vacuum. I know vacuum bagging 1/16" rock maple veneer is almost impossible into tight curves. Granted this isnt a tight curve, but its also 10 times the thickness. But if it does work, a vacuum table will be next on my list of things to build
We are either going to use vacuum or....the inserts. If we used the inserts we would have to start with a core that is the max thinkness of the final profile so that the router bit doesn't hit the inserts. Its a bit hard to explain however, I will send pics of the final setup
the insert method sounds more promising (vacuums can be very tricky...i have gone through MANY methods trying to vacuum-thermoform topsheets). so the inserts will be installed temporarily upsidedown, then bolted into from the table? how do you think the final shape will be? if it bows mostly at the ends, your tip and tail will be pretty thick. if you can get any pictures of the process that would be great. OH, you know what else would work and allow you to make a full pass...if you have your core pre-shaped with a slight angle on the sidewall (i put a 60 degree sidewall on my skis), you could use an edge clamp to hold down the core, just like you would with a piece of metal on a milling machine. mcmaster would have them cheap. actually if you dont want to preshape the core, you could cut a step right into the side (that will get trimmed away later), and use a normal bolt down clamp right to the step. oh, i like that...now i want to try...if i explained it bad let me know...
Not sure if I completely follow you. Seems like there are a lot of extra steps involved. Trying to keep it as simple as possible.
Another thing to keep in mind is that the core blank needs to be excessively long so that the ends can be clamped down to the fixture. This method could also be adapted so that would can send the entire fixture through a planner
Another thing to keep in mind is that the core blank needs to be excessively long so that the ends can be clamped down to the fixture. This method could also be adapted so that would can send the entire fixture through a planner
In doing the 'inverse' profiling, how are you going to end up with a flat area at the waist and at the tip and tail of the core? I've been using a conventional profiler (as described on this site) with the addition of a vacuum clamping table. It takes less than 2 minutes to profile a perfect core. The vacuum table holds the core rock solid and switching from one core to the next takes about 10 seconds. I could probably do 30 or more cores in an hour. Your idea is a creative one, for sure, but I'm just wondering why you couldn't use your same vacuum table idea with the cnc router and profile from the top. You could still profile mutiple cores at one time and end up with a more desirable profile. Because the flat base of the core would facing down, your vacuum problems would be simplified or eliminated. Just some thoughts.
G-man
G-man
thats true as long as the cnc table has z-travel (if he is to stick with cncing). it may not be as simple as the profile jig method, but it sounds like it could simplify the planer method. i have never had much luck with the profile jig method, i can never get the two rails to be identicle enough. also the profile is never the same as the ribs due to the wheelbase of the carriage. maybe i need cnced steel ribs for accuracy.