Well almost. I have amassed most of the materials. the remainder will arrive this week and I can start my first set! I'm very excited about this. However I have a few questions for the "pros" out there.
1. I plan on using 1/2" sidewall material. the question is this. How much should I cut back on the wood core from the finished dimensions to allow for the sidewall material? OR how wide should the finished sidewall be?
2. I will be using tip spacers on the skis. Does the sidewall material stop where the tipspacer starts?
3. I plan on tapering down to 2mm at the tip. Where or how far up does the wood go tward the tip (the starting point of the spacer)? At the bend, just into the bend or before the bend, ect...
3. I'm sure I'll have more in the future so I'll ask them later...
Thank you all for the help!
rockaukum
ready, set, go....
Moderators: Head Monkey, kelvin, bigKam, skidesmond, chrismp
Hi rockaukum,
Here are my answers to your questions:
1. I also use 1/2 " material, so I make the core about 7/16 smaller all around than the finished ski dimension. This leaves about 1/16 inch of sidewall material outside of the metal edge after pressing. The band saw blade tends to cut right up against the sidewall (UHMW) so that leaves 1/16 inch to grind/sand away. I try to keep it minimal because the UHMW is very tough to remove.
2. Yes. Looking through the clear topsheet on my finished skis, I can't tell where the sidewall ends and the tip spacers begin.
3. I don't square off the core at the tip and tail curves because I feel that doing so creates a stress point where the rigid plastic meets the more flexible wood (others may certainly disagree here). Instead, I make a 'horseshoe' shaped tipspacer that is about 1/2 inch smaller than the finished tip and tail shapes.
I hope this makes sense. I'm more sleepy than I realized when I decided to respond to your post. I can't tell if it makes sense or not. I'll check-in in the morning.
G-man
Here are my answers to your questions:
1. I also use 1/2 " material, so I make the core about 7/16 smaller all around than the finished ski dimension. This leaves about 1/16 inch of sidewall material outside of the metal edge after pressing. The band saw blade tends to cut right up against the sidewall (UHMW) so that leaves 1/16 inch to grind/sand away. I try to keep it minimal because the UHMW is very tough to remove.
2. Yes. Looking through the clear topsheet on my finished skis, I can't tell where the sidewall ends and the tip spacers begin.
3. I don't square off the core at the tip and tail curves because I feel that doing so creates a stress point where the rigid plastic meets the more flexible wood (others may certainly disagree here). Instead, I make a 'horseshoe' shaped tipspacer that is about 1/2 inch smaller than the finished tip and tail shapes.
I hope this makes sense. I'm more sleepy than I realized when I decided to respond to your post. I can't tell if it makes sense or not. I'll check-in in the morning.
G-man
G-man,
Thanks for the reply. Your answers were what I was looking for. You brought up another point I was interested in. I want to do a clear topsheet (no fabric) so I would be able to evaluate the laminate throughout the lift of the ski. IE: look for weak areas ect... I was planing on using WestSystems epoxie with the cold cure hardener. Have any experience with that product? Does it yellow or cause any adverse reactions over time?
Again, Thanks for the help.
rockaukum
Thanks for the reply. Your answers were what I was looking for. You brought up another point I was interested in. I want to do a clear topsheet (no fabric) so I would be able to evaluate the laminate throughout the lift of the ski. IE: look for weak areas ect... I was planing on using WestSystems epoxie with the cold cure hardener. Have any experience with that product? Does it yellow or cause any adverse reactions over time?
Again, Thanks for the help.
rockaukum
rockaukum,
I don't have any experience with West Systems products so can't help you there. But, yes, if you want to evaluate the innards of the ski over time, then leave out the fabric. I've had bond failures ranging from micro fractures of the glass layer along the inner edges of the top surface of the skis (from banging them together when I ski) to quarter size (and larger) delamination voids in the areas of the tip spacers and sidewalls. I wouldn't have been able to see these problems if I had put fabric in the mix. In fact, I built a pair of skis last Spring in which I did a lousy job of surface treating the UHMW and pretty much the whole perimeter of the ski delaminated, top and bottom, probably the first day out, but I didn't notice it because the fabric hid the voids. I test my skis now-a-days by tossing them as high as I can into the air in parking lots, chucking them like javelins across the parking lot, then running over them with the biggest truck I can find. Keeping the topsheet translucent helps me to assess how much they suffer.
G-man
I don't have any experience with West Systems products so can't help you there. But, yes, if you want to evaluate the innards of the ski over time, then leave out the fabric. I've had bond failures ranging from micro fractures of the glass layer along the inner edges of the top surface of the skis (from banging them together when I ski) to quarter size (and larger) delamination voids in the areas of the tip spacers and sidewalls. I wouldn't have been able to see these problems if I had put fabric in the mix. In fact, I built a pair of skis last Spring in which I did a lousy job of surface treating the UHMW and pretty much the whole perimeter of the ski delaminated, top and bottom, probably the first day out, but I didn't notice it because the fabric hid the voids. I test my skis now-a-days by tossing them as high as I can into the air in parking lots, chucking them like javelins across the parking lot, then running over them with the biggest truck I can find. Keeping the topsheet translucent helps me to assess how much they suffer.
G-man
G-man,
Seems like a private conversation here. Thanks for the help. Another point comes up... Flame treating the Uhmw. I thought the stuff from durasurf was already set up so you don't have to flame treat?? Where can I get the inside scoop on this process and how does one know if it needs to be done?
Your help is invaluable and I thank you!
rockaukum
Seems like a private conversation here. Thanks for the help. Another point comes up... Flame treating the Uhmw. I thought the stuff from durasurf was already set up so you don't have to flame treat?? Where can I get the inside scoop on this process and how does one know if it needs to be done?
Your help is invaluable and I thank you!
rockaukum
Me again,
Yes, the 1/2 inch UHMW comes abraded and flame treated on one side, but that is probably the surface that you will bond to your core. From there, you'll be doing your profiling, and even if your material came flame treated on all sides, you'd end up machining the treatment away when you profiled. So, you need to flame treat the sidewall strips after you profile the core assembly. Some folks say it's as simple as "passing a propane torch over the UHMW". That approach hasn't worked for me and is not supported by the dozens of references/articles that I've managed to locate on the internet. There has been a lot of stuff discussed on this forum about the subject. I tried to quickly look some of it up for you, but it's kind of scattered around. I'm headed to bed for an early morning rise and a week away (not skiing
), or I'd try to locate some stuff for you. Try a search for 'bonding UHMW' and 'flame treating'. I've said it many times before and I still feel it to be true, that I think that successful bonding of the sidewall material, to the top and bottom glass layers, is the most challenging part of ski building.
good luck,
G-man
Yes, the 1/2 inch UHMW comes abraded and flame treated on one side, but that is probably the surface that you will bond to your core. From there, you'll be doing your profiling, and even if your material came flame treated on all sides, you'd end up machining the treatment away when you profiled. So, you need to flame treat the sidewall strips after you profile the core assembly. Some folks say it's as simple as "passing a propane torch over the UHMW". That approach hasn't worked for me and is not supported by the dozens of references/articles that I've managed to locate on the internet. There has been a lot of stuff discussed on this forum about the subject. I tried to quickly look some of it up for you, but it's kind of scattered around. I'm headed to bed for an early morning rise and a week away (not skiing
), or I'd try to locate some stuff for you. Try a search for 'bonding UHMW' and 'flame treating'. I've said it many times before and I still feel it to be true, that I think that successful bonding of the sidewall material, to the top and bottom glass layers, is the most challenging part of ski building.good luck,
G-man
