Jonrezz’s Build Log

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Jonrezz
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Joined: Thu Feb 13, 2020 1:14 pm

Jonrezz’s Build Log

Post by Jonrezz »

After years of reading these forums I finally have the space to give it a go! Thank you all for the wonderful resources and info in these forums, we would’ve never gotten this far this fast without you!

I started out in January with my buddy and feel like were getting close to pressing our first pair 8) . He hasn’t been over in a while because of the circumstances, but I’ve been busy progressing the shop.

Gotta finish up the vacuum table and figure out heat for it. I was thinking about getting a motorcycle tyre warmer for the heat and place it on top of the silicone sheet (idea from OACs post)

Also gotta figure out graphics and edgebending. Was thinking about trying a fretbender and either veneer or a printer

I live on the east coast US and do a lot of hard pack/groomer skiing. I used to race GS & slalom in college and HS, and my SL skis are 10+ years old and shot, so my first pair is inspired by my Fischer RC4 Sl’s. 165 cm, 113-64-98, full camber. Poplar core with oak stringers, full width titanol top and bottom, CF under the core and FG over the core.

Here’s some photos of my progress:

https://imgur.com/gallery/YK75nzK

Looking forward to sharing more as I keep going!

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chrismp
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Re: Jonrezz’s Build Log

Post by chrismp »

Try the modified tile nippers for bending edges. Cheap, quick to make and works well.

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Dr. Delam
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Re: Jonrezz’s Build Log

Post by Dr. Delam »

Or cut your edges short and skip the full wrap edges. Quick and easy.

skidesmond
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Re: Jonrezz’s Build Log

Post by skidesmond »

That’s a lot of laminates in a short ski. What thickness are you planning for the core? Having 2 layers of titanal, FG and CF will make for a really stiff ski which you’ll want but if the tip area doesn’t bend enough the ski won’t want to release out of the turn. And since the ski is short at 165cm, you want it to bend but be damp. If this is your first ski I’d stick to the basics. I’d skip the CF. And for the FG might be better off with a light weight biax weave. The core thickness plays a huge part also.

Hannes
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Re: Jonrezz’s Build Log

Post by Hannes »

That CNC looks nice! I am thinking about building one but I am still in the mode of getting the right ideas to keep the dimensions, the stiffness, the price, the amount of time and the peace with my wife in the right order.

Jonrezz
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Re: Jonrezz’s Build Log

Post by Jonrezz »

Thanks for the feedback!

Chris/Delam - I ordered some nippers to make a simple edge bending tool. I also ordered one of those drill press vices that others have used to make the wheeled version of edge benders - but not sure when i'm going to get around to that. seems like a whole project in itself. I also want to stop my edges at the ends of the running length instead of wrapping around the front of the ski - but my buddy thinks its a mistake to do it that way because it will be less resilient and cause a premature failure/delam. Since he says that, now of course I have to do it that way to prove him wrong 8)

skidesmond - Honestly i'm a bit concerned that they will come out too stiff too. Looking at my RC4's, it's clear that they have 2 full titanol layers and the core is on the thick side, but I'm not sure what composites they use as far as fiberglass, carbon, etc. I wanted to keep both sheets of titanol in the design because from what i read it will make them nice and damp and allow good edge holding capability - which is super important to me because I spend a lot of my time on the slopes carving groomers at gore, okemo, killington, etc. For core thickness, my plan was to go with 2 mm at the tip and tail and 12 mm underfoot. I think I will take your advice though and choose weaker composites. I don't want the skis to be too soft and not be able to perform at speed, but I definitely don't want them too stiff either.

Hannes - Thanks! if it's any help the CNC in the photos is about as affordable as I could find - it gets the job done with enough accuracy; I just run it more slowly than one would on a stiffer machine. To give a general idea of the performance - on hardwood I run a 1/4" bit at 75 in/min and 1/8" step-down. I've tried to go more aggressive than that before but it didn't end well lol.

Another thing I'm really hung up on is - I'm working on CAD and CAM for my camber mold while I wait for other materials to arrive - gonna cut it on the CNC - but I'm really nervous about where to start as far as accounting for the camber relaxation after pressing - some threads on here say to double the design camber (ie if you want 9 mm of ski camber - make the mold with 18 mm of camber) - but in some places I see people getting results true to their mold (ie 9 mm camber in the mold - 9 mm camber in the ski). I plan on heating from the top-only during pressing which makes me think I should go with a mold more true to the camber I want since the top will expand faster than the bottom while the epoxy is curing - but I have a feeling Its going to take multiple attempts to get it right. My thought process regarding heat from the top only is it will be a lot more affordable to do a 120 volt setup / single heating pad. I wonder if I'm better off in the long run just spending the extra cash to run a 240 volt outlet and do two heating pads - one on top and one on bottom. If i destroy 3-400 bucks worth of materials doing trial and error with the single heat pad work - then it would've made sense to just get the dual heat setup in the first place.

BS Tech
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Re: Jonrezz’s Build Log

Post by BS Tech »

its been our experience that camber runs from heat...
meaning.. top heat only= less camber
bottom heat only= more camber
assuming a symmetrical build.

skidesmond
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Re: Jonrezz’s Build Log

Post by skidesmond »

We’re basically skiing the same areas and we are both carvers. IMHO no need to run the edges all round the tip or tail. I run my edges about half up the tip and tail. No problems with delams. Make sure you pre bend the tips and tails after you attach the edges. This helps prevent the edges from pulling away in the tips/tails.

Keep the 2 layers of metal, ditch the CF. As for the FG I think you’re better off with a very light weight triax or med weight biax. You’ll get the torsional stiffness from the Titanal so biax will work ok. As for the camber I would go true to what you want. If you end up with too much camber and a stiff ski it will chatter like hell on hard pack.

As for the core thickness 12mm for a 165cm ski is pretty thick when you’re adding titanal. I made 180cm GS cheater ski. I’ll include the details and review in a link at the end. But in short my wood core is ash in the binding area, poplar fore and aft, for tip fill I used ash veneer about 1.6-1.8mm thick. I used 2 layers of titanal that is .6mm thick. And Flax instead of FG. The flax is a biax weave and around 10.35 ounces. The wood core is 10.5mm thick tapered down to about 1.8mm. I use Ipe wood sidewalls which really stiffens the ski also. The length of the binding area also is a big factor in the stiffness of the ski, generally the binding area is a consistent thickness.

If you have digital calipers take some measurements of your RC4 and do a little bit of reverse engineering. I did this to a pair of 180cm Fischer RC4. The max thickness of the was about 15mm. Then I started subtracting out the laminate thickness. The wood core came out to be about 10-10.2mm tapered down to 2mm. The binding area was a lot smaller than I normally make mine. I think it was about 100mm in front and behind boot center.

I made 165cm ski and made the wood core 9.4mm and binding area 265mm/355mm tapering to 1.8mm. I used flax and CF strip 2inchs wide above and below the core. The CF was uni weave and super light at 4.4oz. Ski came out really nice. I made this ski once before and the tip area was way to stiff and the core was about 11mm thick. The ski would not release out of a turn unless you were going really fast and flexing the ski hard. It wasn’t fun skiing on it and ended up pulling the bindings off.

Here’s the details on my 180cm ski:

http://www.exoticskis.com/Forum/default ... osts&t=585

skidesmond
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Re: Jonrezz’s Build Log

Post by skidesmond »

Here’s a couple of pics of my planer crib. Hope this helps. I’m working on a new version however.
6917D19D-9C24-4521-AC92-71AB17228989.jpeg
6917D19D-9C24-4521-AC92-71AB17228989.jpeg (85.12 KiB) Viewed 517 times
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334B964E-A473-47ED-9874-C75F5FEC6616.jpeg (92.96 KiB) Viewed 517 times

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