I have built two pairs of skis now and both of them have experienced the wood core shifting to the side sometime between putting it in the press and opening it up the nextg day, and I end up losing my sidewall on one side. Does anybody have a good method to fix this? I also have what looks like white air pockets or something throughout the top of the ski and I hope someone can point me in the right direction to remedy this too.
Other than that, they RIP!
Thanks,
Matt
Shifting during pressing
Moderators: Head Monkey, kelvin, bigKam, skidesmond, chrismp
I use two screws on each side of the core. These are about 400mm fore and aft of the mid camber reference line. Everything has a mid camber ref line; Templates, molds, base, core, top, graphic layer, and every piece of reinforcement.
The hardboard placed beneath the core shown in this photo is a crude spacer used to set the height of the screw assembly. This is an old photo, I now use 3/32" thick polycarb as a set-up spacer, it's closer to the actual ski materials thickness (base + reinforcements).
The ends of the screws fit into shallow dimples drilled into the side wall material, about 0.5mm deep. This keeps the core down and centered during lay-up. The screws are adjusted to align the core perfectly over the base. The screws on one side of the ski are then loosened about 6mm prior to starting the lay-up. Then once the core is placed for real, they are snugged back into their clamping position.
During prep, while the core is fixed in place (with no spacer material protruding), I trace along the sides of the core assembly with a Sharpie. Later I affix the base assembly to the aluminum with a few spots of double sided tape, taking care to center it between the Sharpie marks while ensuring my mid-camber reference marks are also aligned. Spray glue (Type 77) has also been used to affix the base with no ill effects.
BTW, that's a 10-32 UNF threaded rod and the 1" aluminum angles are tapped. I've learned to spray some Teflon dry lube on the exposed screw threads during mold prep. This allows the screws to be loosened easily later after the ski is cured.
Hope this helps.
Cheers,
S
The hardboard placed beneath the core shown in this photo is a crude spacer used to set the height of the screw assembly. This is an old photo, I now use 3/32" thick polycarb as a set-up spacer, it's closer to the actual ski materials thickness (base + reinforcements).
The ends of the screws fit into shallow dimples drilled into the side wall material, about 0.5mm deep. This keeps the core down and centered during lay-up. The screws are adjusted to align the core perfectly over the base. The screws on one side of the ski are then loosened about 6mm prior to starting the lay-up. Then once the core is placed for real, they are snugged back into their clamping position.
During prep, while the core is fixed in place (with no spacer material protruding), I trace along the sides of the core assembly with a Sharpie. Later I affix the base assembly to the aluminum with a few spots of double sided tape, taking care to center it between the Sharpie marks while ensuring my mid-camber reference marks are also aligned. Spray glue (Type 77) has also been used to affix the base with no ill effects.
BTW, that's a 10-32 UNF threaded rod and the 1" aluminum angles are tapped. I've learned to spray some Teflon dry lube on the exposed screw threads during mold prep. This allows the screws to be loosened easily later after the ski is cured.
Hope this helps.
Cheers,
S
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MontuckyMadman
- Posts: 2395
- Joined: Fri Jun 20, 2008 9:41 pm
wow shif that's pretty over the top.
Most people here use a plastic standoff or dowel system in the core somehow. You can also just make some short guides on the sides of the core attached to the cassette made the same height as the core. Wont help with slippage front to back but it will with side to side movement.
I use 2 small dowels in the center of the core super glued to the base prior to layup with corresponding holes in the core. Works great but I have to put some small holes in the core at specific locations.
Most people here use a plastic standoff or dowel system in the core somehow. You can also just make some short guides on the sides of the core attached to the cassette made the same height as the core. Wont help with slippage front to back but it will with side to side movement.
I use 2 small dowels in the center of the core super glued to the base prior to layup with corresponding holes in the core. Works great but I have to put some small holes in the core at specific locations.
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doughboyshredder
- Posts: 1354
- Joined: Mon Sep 17, 2007 7:37 pm
This.MontuckyMadman wrote: I use 2 small dowels in the center of the core super glued to the base prior to layup with corresponding holes in the core. Works great but I have to put some small holes in the core at specific locations.
I drill the holes in the core, and then line up my core to the base and mark where I need to glue my dowels. I then use spray contact cement to hold the base down. All of the plates have centerlines on them.
That would work Alex
I think headmonkey used a similar technique with his boards. I don't think he offset one to the left and one to the right though.
@doughboy: using the spray adhesive on your aluminium molds, do you also use a mold release? Does the spray adhesive stick to a waxed mold skin or do you have to leave a non waxed area where you spray the adhesive spray.
I think headmonkey used a similar technique with his boards. I don't think he offset one to the left and one to the right though.
@doughboy: using the spray adhesive on your aluminium molds, do you also use a mold release? Does the spray adhesive stick to a waxed mold skin or do you have to leave a non waxed area where you spray the adhesive spray.
http://www.happymonkeysnowboards.com/HM ... amination/A critical part of layup is alignment of the core to the base, and thus the mold (since the base is already aligned to the mold.) The core may be aligned to the base carefully when it is first placed during layup, but as the laminate is placed into the press it is quite easy for the core to shift. Any core shift is unacceptable and results in a lost board, so we take care to ensure this simply cannot happen.
Shops that build specific board models have dedicated “cassettes” for each shape, with permanent fixtures to hold the base and the core in alignment. Doing the same thing for a one-off custom build is impractical, but there is a simple alternative. Extra “alignment inserts” are affixed directly to the base. Alignment holes in the core match these insert locations, and positively align the core to the base. These inserts are never drilled out and exposed in the final product; they remain contained within the laminate. The bottom layer of glass is cut to allow these two alignment inserts through without distorting the glass layer.
Don't wait up, I'm off to kill Summer....
Ya, but it works really well. I like the idea of attaching metal guide pieces to the aluminum hot plate that would capture the base assembly. Especially for making multiple similar skis.MontuckyMadman wrote:wow shif that's pretty over the top...
If I continue this crazy project much further, I plan to build a two-up press and tooling. Making skis in pairs makes so much sense. My screw clamp idea does not lend itself to a double-wide press form.
-S
Yeah I was wondering how you held the other side of the core with 2 skis.
You could still work it out. Just need to mount two pieces on your skin between the skis and just use pressure from the outside to hold in place. Need to make sure the piece on the skin is lower than your total ski height. I can see you working it out. Even just a block of aluminium with a tapped hole through the middle and some all thread with a nut welded to the end to let you screw it in or out. I think it's better than drilling holes in the core even though that's what I'm planning on doing!
You could still work it out. Just need to mount two pieces on your skin between the skis and just use pressure from the outside to hold in place. Need to make sure the piece on the skin is lower than your total ski height. I can see you working it out. Even just a block of aluminium with a tapped hole through the middle and some all thread with a nut welded to the end to let you screw it in or out. I think it's better than drilling holes in the core even though that's what I'm planning on doing!
Don't wait up, I'm off to kill Summer....
Two methods I have used with success:
Sticky foam pads. The first pad is as thin as the edge height and keeps the base in place. Two in the front of the ski and two in the rear. After the base is set, I place the core on top of the base and put more sticky pads on the cassette at the edge of the sidewalls, two in the front and two in the back. These pieces are thicker to come up at least half way up the sidewall.
I also like the dowel method as I also incorporate the holes in my profiling process.
No shift mishaps with either of the methods for me.
Sticky foam pads. The first pad is as thin as the edge height and keeps the base in place. Two in the front of the ski and two in the rear. After the base is set, I place the core on top of the base and put more sticky pads on the cassette at the edge of the sidewalls, two in the front and two in the back. These pieces are thicker to come up at least half way up the sidewall.
I also like the dowel method as I also incorporate the holes in my profiling process.
No shift mishaps with either of the methods for me.
I see.
If you have the insert stuck to the base it might "suck" the base up when you tighten the bindings. Your tolerance for the flange depth recess will have to be pretty spot on or there will be a void between the top side of the flange and the core. But probably that tolerance is spot on anyway. I guess the insert ends up "stuck" to the base when you press anyway.
For the fibreglass I am thinking of getting a hole punch to punch the hole in the glass where the dowel/insert needs to go through. I use biopsy punches at work too that are basically circular razors that you can spin around to cut a hole. I might try one of these too. Others I'd say use a scalpel to just cut a hole. I don't think it's that great to cut the continuity of the glass but for such a small area I can't see it making a great deal of diference.
What I'm thinking of doing is drilling 2 holes in my core. Then I will drill corresponding holes in my core template and place dowels facing upwards. Then I can fix the core firmly to my template for routing the sidecut shape. After that I will profile the core. Then do what doughboy does and allign the core on the base and mark where to superglue on the dowels.
If you have the insert stuck to the base it might "suck" the base up when you tighten the bindings. Your tolerance for the flange depth recess will have to be pretty spot on or there will be a void between the top side of the flange and the core. But probably that tolerance is spot on anyway. I guess the insert ends up "stuck" to the base when you press anyway.
For the fibreglass I am thinking of getting a hole punch to punch the hole in the glass where the dowel/insert needs to go through. I use biopsy punches at work too that are basically circular razors that you can spin around to cut a hole. I might try one of these too. Others I'd say use a scalpel to just cut a hole. I don't think it's that great to cut the continuity of the glass but for such a small area I can't see it making a great deal of diference.
What I'm thinking of doing is drilling 2 holes in my core. Then I will drill corresponding holes in my core template and place dowels facing upwards. Then I can fix the core firmly to my template for routing the sidecut shape. After that I will profile the core. Then do what doughboy does and allign the core on the base and mark where to superglue on the dowels.
Don't wait up, I'm off to kill Summer....
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doughboyshredder
- Posts: 1354
- Joined: Mon Sep 17, 2007 7:37 pm
headmonkey adds a couple inserts that never get used. He glues these to the base.falls wrote:That would work Alex
I think headmonkey used a similar technique with his boards. I don't think he offset one to the left and one to the right though.
@doughboy: using the spray adhesive on your aluminium molds, do you also use a mold release? Does the spray adhesive stick to a waxed mold skin or do you have to leave a non waxed area where you spray the adhesive spray.
http://www.happymonkeysnowboards.com/HM ... amination/A critical part of layup is alignment of the core to the base, and thus the mold (since the base is already aligned to the mold.) The core may be aligned to the base carefully when it is first placed during layup, but as the laminate is placed into the press it is quite easy for the core to shift. Any core shift is unacceptable and results in a lost board, so we take care to ensure this simply cannot happen.
Shops that build specific board models have dedicated “cassettes” for each shape, with permanent fixtures to hold the base and the core in alignment. Doing the same thing for a one-off custom build is impractical, but there is a simple alternative. Extra “alignment inserts” are affixed directly to the base. Alignment holes in the core match these insert locations, and positively align the core to the base. These inserts are never drilled out and exposed in the final product; they remain contained within the laminate. The bottom layer of glass is cut to allow these two alignment inserts through without distorting the glass layer.
I use general purpose wax as a mold release. I use a very small amount on my skins, and don't use any under where the board will be. The spray adhesive can be tricky to work with. If you wait too long the bond is stronger than necessary. I basically spray both sides and stick em. It doesn't take much and you only have a few seconds to adjust so getting lined up right is critical. I have centerlines on my skins and I mark center on the edge of the edge with a sharpie.
Hugo, I would love to see how you use magnets
I am about to try some magnets as well. I am just going to use steel skins/cassettes in stead of the aluminum I have been using. I bought a bunch of neodymium magnets off of ebay in different thicknesses, 1/16", 1/8", 1/4" and 1/2". My plan is to cover them with mold release and just use them to hold everything in place down the sides of each ski. Different thicknesses will obviously be used at diffferent parts of the ski. I think with them covered in mold release they should be reuseable. It's the only way I could figure out how to do custom shapes easily. I have done the dowels through the core and had good luck, but I really didn't want to be drilling through the core. I will try to get some pics up when I do my next layup.