Norsk Alpine
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knightsofnii
- Posts: 1148
- Joined: Tue Jan 08, 2008 6:02 am
- Location: NJ USA
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After all of the suggestions and discussions here I took a step back from my core-profiling and decided I needed to make a better jig to get a good methodology down. After looking at the cribs you all have made I took a trip to home depot and bought some 3/4" mdf and made a decent crib. CAFactory and powderho...I am very glad you suggested making the crib parallel for the first 4-6". I think that is the key to reducing snipe or having the tip and tail eaten by the planer when put through.
I decided to scrap my old cores and practice making a new pair out of an old cedar deck board I had in my garage. The "practice" pair turned out so good that I'll be using them in my next build! I then went on to make a 12" wide profile that will be used underneath the mold for camber. NO MORE SHIMS.
Powderho - To calculate the forces seen by the press I took the width of my hose laying flat, assumed it would be that wide when inflated, then calculated the resultant forces for the full 8' length at 50psi. The over-estimation of contact area (both length and width) is my safety factor for this build. The FEA analysis calculated a safety factor around 1.5, so I was confident with continuing the build. Also, the pallet rack I used is refered to as "Structural" or "Seismic", and the standard recommendation for each beam pair is 13,000lb. , significantly more than the rating for teardrop style (4000lb).
In the end I still stand behind a wall when I inflate the bladders, 100,000 pounds of force is nothing to mess with!
I decided to scrap my old cores and practice making a new pair out of an old cedar deck board I had in my garage. The "practice" pair turned out so good that I'll be using them in my next build! I then went on to make a 12" wide profile that will be used underneath the mold for camber. NO MORE SHIMS.
Powderho - To calculate the forces seen by the press I took the width of my hose laying flat, assumed it would be that wide when inflated, then calculated the resultant forces for the full 8' length at 50psi. The over-estimation of contact area (both length and width) is my safety factor for this build. The FEA analysis calculated a safety factor around 1.5, so I was confident with continuing the build. Also, the pallet rack I used is refered to as "Structural" or "Seismic", and the standard recommendation for each beam pair is 13,000lb. , significantly more than the rating for teardrop style (4000lb).
In the end I still stand behind a wall when I inflate the bladders, 100,000 pounds of force is nothing to mess with!
Norsk Update
I've made some significant changes since my last journal post. Namely moving from MN to CO. Unfortunately it looks like I lost some of my touch. I had a few problems getting my air bladder to coform to my mold, but I think my primary issue was too much heat.
I'd appreciate any feedback from someone who's seen this issue before, or has a likely guess. I knew I had a problem as soon as I took them out of the mold... For reference, the "ski" on the left is actually the base I ripped off the ski after my realization that it was a total failure. (I used Rhino epoxy and was able to reclaim my cores in about 3 minutes! Not good).
I had my TC stuffed in near the rear tip of the ski, and I'm planning to move it to the front-center of the ski's during my next attempt.
I also tried a camber-mold used my profiling 9mm of camber into a sheet of MDF, manufactured with the help of COSurfer. Overall the camber turned out fantastic, and I'm excited to try this method again.
I'd appreciate any feedback from someone who's seen this issue before, or has a likely guess. I knew I had a problem as soon as I took them out of the mold... For reference, the "ski" on the left is actually the base I ripped off the ski after my realization that it was a total failure. (I used Rhino epoxy and was able to reclaim my cores in about 3 minutes! Not good).
I had my TC stuffed in near the rear tip of the ski, and I'm planning to move it to the front-center of the ski's during my next attempt.
I also tried a camber-mold used my profiling 9mm of camber into a sheet of MDF, manufactured with the help of COSurfer. Overall the camber turned out fantastic, and I'm excited to try this method again.
Looks like you way over cooked your skis to me. I did this on the first pair I pressed with heat. Mine didn't turn out that bad, but they had huge blisters on them. They were also smoking pretty good when I took them out of the press. I only have heat on the bottom and I had my TC located on the top, tail end of the cassette. I was thinking this would be last place to heat up to full temp (and it probably was) so I wanted to make sure it reached 175 degrees. Well by doing that, the bottom center of my ski was probably around 250 degrees. P-tex melts right around there. There's not that much temperature difference between the ideal cure temp for the epoxy and P-tex's melting point. I started using multiple TC's to monitor the temp in various places. My current setup has the controlling TC placed bottom, center--the hottest part. I don't want that part getting hotter than 175. The top of the cassette will only reach about 145 degrees by doing this. I just leave them in for a bit longer; around 2 hrs under heat.
New epoxy: Check
T/C placed in correct position: Check
And after 30 minutes at temperature and pressure: Voila!
Introducing the Norsk Odin 176. 136-110-123 25.5m sidecut.
Durasurf 4000
20oz Triax
Cedar core with Maple sidewalls 2-9.5-2
20oz Triax
20 oz Triax in binding area
Black Walnut
These are crappy cell phone picks from the back of my truck this morning. Two more coats of UV Urethane and they'll be ready for the first base grind. I hope to get some better pictures up wheny they're "prettier."
T/C placed in correct position: Check
And after 30 minutes at temperature and pressure: Voila!
Introducing the Norsk Odin 176. 136-110-123 25.5m sidecut.
Durasurf 4000
20oz Triax
Cedar core with Maple sidewalls 2-9.5-2
20oz Triax
20 oz Triax in binding area
Black Walnut
These are crappy cell phone picks from the back of my truck this morning. Two more coats of UV Urethane and they'll be ready for the first base grind. I hope to get some better pictures up wheny they're "prettier."