When good 4001 base goes bad.
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heybulldog
- Posts: 17
- Joined: Wed Jan 02, 2008 3:41 am
- Location: Reading, Pa
When good 4001 base goes bad.
Ok, I'm working on my third pair of skis and I'm consistantly having the same problem. I use a router and a template to shape the 4001 base to the desired shape. When finished they are identical. Then... I attach the steel edges whith a few spots of super glue and the bases get all bent out of shape.. they are flat but it seems like they become sort of bananna-ish. It is causing me distress because the core is no longer the same shape as the base. Is this a chemical reaction? Is ther anythging I can do to prevent this? Thanks for the input.
If at first you don't succeed, try try again.
Symmetry is the key to success.
The day you receive the P-tex, split it down the middle and set it aside to relax. You will be surprised how much it moves over time. Ignore this step if making a snowboard.
Make sure your template is symmetric. I usually hand shape one half of the template using 1/4" MDF to match my CAD plot, then router trim a clone for the other half. Glue these together making certain the joint is perfectly straight. Then glue a sheet of 1/8” hardboard to them for reinforcement. Trim this off flush with your router.
Pre-bend all four steel edges to match the template. Anneal with a propane torch as required to make tight bends. Sand off all the char marks left from annealing. Inspect all four bent edges and adjust as needed so all are nearly identical in shape.
Prepare the P-tex by first making rough cuts, keeping an inch away from the desired net shape. Cut two (or four) bases simultaneously with a jig saw, using some doubly sticky masking tape to keep them together. Let them sit a few days (or longer) to stabilize before making a another, closer rough cut. Wait again before making the final trim. Router shaping is done one base at a time. First secure a base to the template using 4 or 5 spots of double sticky. The idea is to trim to final shape and then attach the edges before removing from the template.
Fit a pair of edges to the base and clamp as needed to stay put. Start on one end and secure the edge tabs to the base using Super glue. Work both sides of the ski together, 3 clamps on the left side, 3 on the right, 3 left, 3 right, and so on. I have enough clamps to go about a third of the length of the ski before I start pulling from the beginning. Keep it all symmetric:
Don’t remove the base assembly from the template until you’re ready to construct a ski.
You can probably assemble the other base using the back side of the template while the first base is still attached, although I haven’t tried this.
Hope this helps,
-S
The day you receive the P-tex, split it down the middle and set it aside to relax. You will be surprised how much it moves over time. Ignore this step if making a snowboard.
Make sure your template is symmetric. I usually hand shape one half of the template using 1/4" MDF to match my CAD plot, then router trim a clone for the other half. Glue these together making certain the joint is perfectly straight. Then glue a sheet of 1/8” hardboard to them for reinforcement. Trim this off flush with your router.
Pre-bend all four steel edges to match the template. Anneal with a propane torch as required to make tight bends. Sand off all the char marks left from annealing. Inspect all four bent edges and adjust as needed so all are nearly identical in shape.
Prepare the P-tex by first making rough cuts, keeping an inch away from the desired net shape. Cut two (or four) bases simultaneously with a jig saw, using some doubly sticky masking tape to keep them together. Let them sit a few days (or longer) to stabilize before making a another, closer rough cut. Wait again before making the final trim. Router shaping is done one base at a time. First secure a base to the template using 4 or 5 spots of double sticky. The idea is to trim to final shape and then attach the edges before removing from the template.
Fit a pair of edges to the base and clamp as needed to stay put. Start on one end and secure the edge tabs to the base using Super glue. Work both sides of the ski together, 3 clamps on the left side, 3 on the right, 3 left, 3 right, and so on. I have enough clamps to go about a third of the length of the ski before I start pulling from the beginning. Keep it all symmetric:
Don’t remove the base assembly from the template until you’re ready to construct a ski.
You can probably assemble the other base using the back side of the template while the first base is still attached, although I haven’t tried this.
Hope this helps,
-S
my 2 cents: i`ve experienced some base wrapping for the first time on my last pair i built. just make sure that you clamp down the base to the template you built when glueing on the edges.
on my bases one side was good and the other started to wrinkle when forced back into shape. so i clamped it onto the template and put it back into shape. then i glued on the first edge on the side that wasn`t wrinkled. for the edge on the other side i placed those little clamps as shown by shif every 20-30cm to hold the base on the template. then i worked my way from tip to tail, placing some super glue every 5th teeth or so. just from the first 20-30cm section to the next, gluegin one section, letting it dry, then go on to the next section. so i never had more than 30-40cm of "unfixed-to-the-template" base material. came out perfectly.
on my bases one side was good and the other started to wrinkle when forced back into shape. so i clamped it onto the template and put it back into shape. then i glued on the first edge on the side that wasn`t wrinkled. for the edge on the other side i placed those little clamps as shown by shif every 20-30cm to hold the base on the template. then i worked my way from tip to tail, placing some super glue every 5th teeth or so. just from the first 20-30cm section to the next, gluegin one section, letting it dry, then go on to the next section. so i never had more than 30-40cm of "unfixed-to-the-template" base material. came out perfectly.
plywood freeride industries - go ply, ride wood!
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heybulldog
- Posts: 17
- Joined: Wed Jan 02, 2008 3:41 am
- Location: Reading, Pa
Thanks for the input guys. I had no idea that the uhmp was so reactive. I have been taking the base right out of the box and going at it. I take maybe an hour at the most to go from a rolled up peice of uhmp to a shaped base with edges on material. I'll give it a little seasoning time in my shop and shape it slowly.
If at first you don't succeed, try try again.
Yeah, I have found that if I cut the base material into approximately 15cm x 200cm sections, let it deform, and leave it for awhile that when I finally cut it, there is no issues.
I have been using 2001, but just ordered a lot of 4001, so hopefully there is no difference.
I have the edges prebent, but I only glue one side at a time, although the other side is left on the template.
It is the last thing I do before lay up though.
While the super glue is drying I am getting everything ready for layup. Then I just attach the base to the cassette, clean everything, and lay the ski up.
Usually within 60 minutes of cutting the base material the ski is in the press.
I have been using 2001, but just ordered a lot of 4001, so hopefully there is no difference.
I have the edges prebent, but I only glue one side at a time, although the other side is left on the template.
It is the last thing I do before lay up though.
While the super glue is drying I am getting everything ready for layup. Then I just attach the base to the cassette, clean everything, and lay the ski up.
Usually within 60 minutes of cutting the base material the ski is in the press.
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knightsofnii
- Posts: 1148
- Joined: Tue Jan 08, 2008 6:02 am
- Location: NJ USA
- Contact:
you definitely need a temperature controlled environment.
uhmw reacts within seconds to heat and will expand/contract enough to screw up your nice edge job, or make your sidewalls all wavy
wear at least some latex gloves when handling the edging part, even your BODY HEAT will have an effect on the stuff.
to see how drastic it is, wait for a 70+degree day, take your edged base and place it in the sun, then see how long it takes to wrinkle, then put it in the shade, it shrinks back within a minute.
uhmw reacts within seconds to heat and will expand/contract enough to screw up your nice edge job, or make your sidewalls all wavy
wear at least some latex gloves when handling the edging part, even your BODY HEAT will have an effect on the stuff.
to see how drastic it is, wait for a 70+degree day, take your edged base and place it in the sun, then see how long it takes to wrinkle, then put it in the shade, it shrinks back within a minute.
Doug
warped skis and poss. of preforming camber on wooden core?
I'm just about to have a go at making some alpine skis: I'm still at the excited but no kit stage: soon to buy a rack of bits, and so trying to foresee pitfalls and how to avoid them, by learning from those that have gone before!
I'm interested in the observations about the ski bases going wavy: I can see why given that you've got materials that thermally are going to behave so differently, and wonder if this is why in traditional mass production they let the heat press sort it all out: I think I'm right in saying they don't pre bond edges to the bases before lay up; but use jigs to hold everything in place...
Non the less is it the huge stresses and hence resulting strains created by differential thermal expanion in the presses prior to glue hardening that leads to such shockingly non flat bases on mass produced skis ? (particularly at the shovel where they always seem to be concave).
I can't imagine how they get away with it -- but for all the apparent "flattening the base on a grinder" stages displayed on all the factory vids on youtube, whenever I've looked at any retail ski, it is shockingly bad. Are they just too cheapskate to grind the bases properly do you think; or indeed is all they are fussed about is taking off the glue residue so the base looks tidy?
Most skiiers as a result get to ski on really badly sorted equipment because as a DIYer (or come to that in the service shop) flattening a base in nigh to impossible.
So: is it possible to minimise these risks when making your own, and indeed what are the key areas you guys would advise being careful over so as not to have a difficult birth for the new member of the family?
Another possible source of the conavity at the shovel: will the wooden core bend smoothly in the press; or when it is bent at the shovel; can it bend up in such a way that it has a concave hollow under it do any of you find this with your own home made skis, and if so, how do you avoid it ?
If so; is there a case for trying to preform the cambered wood core shape(perhaps in the heat press; wetted... for a day or so..) then stone grinding the base of that to get that flat.... prior to proper glued lay up and heat pressing of the whole structure?
Sorting out a non flat base of a made up ski before you ski on it as part of its "breaking in service" is a pig of a job; so I'm keen to avoid it if I can...
What do you reckon guys?
You've all been here before!
And thank you for such a wonderful forum.. keep up the good work!
Jonathan
I'm interested in the observations about the ski bases going wavy: I can see why given that you've got materials that thermally are going to behave so differently, and wonder if this is why in traditional mass production they let the heat press sort it all out: I think I'm right in saying they don't pre bond edges to the bases before lay up; but use jigs to hold everything in place...
Non the less is it the huge stresses and hence resulting strains created by differential thermal expanion in the presses prior to glue hardening that leads to such shockingly non flat bases on mass produced skis ? (particularly at the shovel where they always seem to be concave).
I can't imagine how they get away with it -- but for all the apparent "flattening the base on a grinder" stages displayed on all the factory vids on youtube, whenever I've looked at any retail ski, it is shockingly bad. Are they just too cheapskate to grind the bases properly do you think; or indeed is all they are fussed about is taking off the glue residue so the base looks tidy?
Most skiiers as a result get to ski on really badly sorted equipment because as a DIYer (or come to that in the service shop) flattening a base in nigh to impossible.
So: is it possible to minimise these risks when making your own, and indeed what are the key areas you guys would advise being careful over so as not to have a difficult birth for the new member of the family?
Another possible source of the conavity at the shovel: will the wooden core bend smoothly in the press; or when it is bent at the shovel; can it bend up in such a way that it has a concave hollow under it do any of you find this with your own home made skis, and if so, how do you avoid it ?
If so; is there a case for trying to preform the cambered wood core shape(perhaps in the heat press; wetted... for a day or so..) then stone grinding the base of that to get that flat.... prior to proper glued lay up and heat pressing of the whole structure?
Sorting out a non flat base of a made up ski before you ski on it as part of its "breaking in service" is a pig of a job; so I'm keen to avoid it if I can...
What do you reckon guys?
You've all been here before!
And thank you for such a wonderful forum.. keep up the good work!
Jonathan