Dry lay up before first use? You might want to double check the matchsticks will still work. You may need to re-configure?
attached to core ----> l__________l l__________l <--- attached to cassette
Richuk is the only one doing it right.
Moderators: Head Monkey, kelvin, bigKam, skidesmond, chrismp
p-tex warpage and the never ending story
Been there. had these issues.
long time ago i used to cut bases out on a table and use the cutout in the press etc. Then one day we put two snow boards together, base to base, and they weren't the same. Dooh. The realization that there are internal stresses in the p-tex that were revealed when cutting out the bases was painful, to say the least.
I have always built small numbers of boards/skis and wanted to be able to change up thickness/widths to allow for different sidecut/width/flex on the same press shoe. This limits the appeal of a cassette. So I came up with the "sidewall dam".
I use a vacuum system, and there are certainly problems with the setup i use, but it does fix some of these problems, and it should work better with a pneumatic setup. Firstly i glue down the base directly to the press (elmers craft spray glue). Cut out the base from a metal template with a razor knife. Bend edges, yes this does include up into the tip/tail curves (sucks). Screw down sidewall/edge dams to hold edges in place. The dams are basically 3/4 inch by 1/2 inch wooden sticks with a small rebate routered into one corner. this rebate fits an edge into it and overlaps it by as much as i want the edge to protrude to allow filing later (about .75 mm). The stick is then thicknessed to the same profile as the core plus 3 mm. The dams are then mold released. Boards/skis are built without sidewalls, per se. I simply wrap my bottom layers of materials around onto the top.
There are a million ways to skin this cat. I have found one that works for me. Sort of. As to how this fits with the warping issues. I really don't have any issues. Just built a splitboard and inside edges are near perfect. Really good. But....
I think the larger issues surround heat. Every time i add heat too fast i have problems. I think most of them would be better with a pneumatic press, but i am not sure about the warpage one. Just for disclosure here I am using System Three "Phase II" resin. I bag the board(s) elevate temp to 90 f for 6 to 8 hours and postcure at 145 f for 2.5 hours.
I think that any radical heating of items in the press before resins reach some sort of "b" stage is asking for trouble. P-tex has a really high cte. especially when compared to epoxy/glass. look at how much camber changes when WAXING a board. The elephant in the room is just how much (little is probably a better word) control the big manufacturers have in controlling convex/concavity. Ask any ski tech and they'll tell you (when customers arent around) that nothing comes from the factory flat. Rocker/camber profiles? How you gonna measure them? Shape? At least you can put them base to base to see. I think some sort of cassette can probably really help in the shape department. Especially if temps are kept moderate until the resins set. Then, even if the stuff moves around differentially during a postcure, at least they have a chance of moving back after. Shit, i don't know....
All this begs the question: Does this really matter? Can you tell, when using a board/skis, if the sidecut radius is .1 meter out? I don't know. Hell, if people can ride magne-traction type sidecuts what won't work? Same with rocker/camber. Some years back most modern rocker profiles would have been thrown out as the skis are bent...
I understand that the real issue is that you want to be able to make what you design. Actually design x,y,z and then get x,y,z out of the press. So whatta ya do?
Don't cut p-tex out without having some way to get it back to the real template shape before pressing. Be careful with heat. I think you need heat, but it is a real pandora's box. Have a backup plan. If you build stuff with straight edges (splitboards) design them so you can grind off the high spots if need be. It ain't perfect. But what in life is?
have fun, Carlito
long time ago i used to cut bases out on a table and use the cutout in the press etc. Then one day we put two snow boards together, base to base, and they weren't the same. Dooh. The realization that there are internal stresses in the p-tex that were revealed when cutting out the bases was painful, to say the least.
I have always built small numbers of boards/skis and wanted to be able to change up thickness/widths to allow for different sidecut/width/flex on the same press shoe. This limits the appeal of a cassette. So I came up with the "sidewall dam".
I use a vacuum system, and there are certainly problems with the setup i use, but it does fix some of these problems, and it should work better with a pneumatic setup. Firstly i glue down the base directly to the press (elmers craft spray glue). Cut out the base from a metal template with a razor knife. Bend edges, yes this does include up into the tip/tail curves (sucks). Screw down sidewall/edge dams to hold edges in place. The dams are basically 3/4 inch by 1/2 inch wooden sticks with a small rebate routered into one corner. this rebate fits an edge into it and overlaps it by as much as i want the edge to protrude to allow filing later (about .75 mm). The stick is then thicknessed to the same profile as the core plus 3 mm. The dams are then mold released. Boards/skis are built without sidewalls, per se. I simply wrap my bottom layers of materials around onto the top.
There are a million ways to skin this cat. I have found one that works for me. Sort of. As to how this fits with the warping issues. I really don't have any issues. Just built a splitboard and inside edges are near perfect. Really good. But....
I think the larger issues surround heat. Every time i add heat too fast i have problems. I think most of them would be better with a pneumatic press, but i am not sure about the warpage one. Just for disclosure here I am using System Three "Phase II" resin. I bag the board(s) elevate temp to 90 f for 6 to 8 hours and postcure at 145 f for 2.5 hours.
I think that any radical heating of items in the press before resins reach some sort of "b" stage is asking for trouble. P-tex has a really high cte. especially when compared to epoxy/glass. look at how much camber changes when WAXING a board. The elephant in the room is just how much (little is probably a better word) control the big manufacturers have in controlling convex/concavity. Ask any ski tech and they'll tell you (when customers arent around) that nothing comes from the factory flat. Rocker/camber profiles? How you gonna measure them? Shape? At least you can put them base to base to see. I think some sort of cassette can probably really help in the shape department. Especially if temps are kept moderate until the resins set. Then, even if the stuff moves around differentially during a postcure, at least they have a chance of moving back after. Shit, i don't know....
All this begs the question: Does this really matter? Can you tell, when using a board/skis, if the sidecut radius is .1 meter out? I don't know. Hell, if people can ride magne-traction type sidecuts what won't work? Same with rocker/camber. Some years back most modern rocker profiles would have been thrown out as the skis are bent...
I understand that the real issue is that you want to be able to make what you design. Actually design x,y,z and then get x,y,z out of the press. So whatta ya do?
Don't cut p-tex out without having some way to get it back to the real template shape before pressing. Be careful with heat. I think you need heat, but it is a real pandora's box. Have a backup plan. If you build stuff with straight edges (splitboards) design them so you can grind off the high spots if need be. It ain't perfect. But what in life is?
have fun, Carlito
Don't want to single you out here, but you heard BS. Epoxy cures via an exothermic reaction, i.e. the chemical reaction creates heat to assist the cure. If you add more heat in, you get a stronger bond and faster cure. Pressure also creates heat and assists the cure. The biggest advantage of pressure though isn't to do with the bond, it's the epoxy squeeze out, which reduces weight. This is why the big guns use high pressures, also assists in reducing cost.DutchDesigns wrote: So this might be B.S but Ive heard that epoxy cured at room temp. 75 F will cure to a better bond as long as its left to fully cure, like a week!
DBS, your prob could be a combination of too much heat and too much pressure, or too fast a ramp up of heat as mentioned above. I haven't had any warpage issues on mine, I cure at 85C for 90min ramped up from room temp over 1/2hr.
Cassettes are definitely the way to go though, especially if you can get away without gluing the edges on. For high temp and high pressure cures, I would agree they are a must. For us low volume and home builders though, these high heat and high pressure cures aren't necessary. The key reasons for em are reducing weight and speeding up the manufacturing time, which are important to big companies but not really us.
I'm think a basic idea for a casette, grab 2x 1.2mm aluminium sheets, CNC cut the board shape out of one with a few channels for resin, then sit on top of another flat sheet and spot weld or rivet together.
This link is posted on another thread, but its spark a few thoughts:
1.41 - 1.44 - I'm not entirely sure whether the edge is on or merely in place at this point. But, if part of the advantages of a cassette is accuracy (base warp) and a great edge fit. Then a simple flat plywood mold would complete this without the need for a full cassette. Secure the plywood mold to a sheet, insert edges and base, apply pressure - usual crock clips would be fine/inserting into a press would be better.
Next step as illustrated in the clip - bending 3D edge sets is tricky by hand, for speed I think you have to go to 4 pieces.
Having done this, you could probably get away with a more general purpose cassette - a flat cassette would be possible, maybe even preferable. Inter-changeable tips molds either way - to hold tip spacers in place, but these are easy to make by hand.
Extend the tip mold 1cm or so to hold the core in place - if the base is pre-bent, it could be a bit tricky, but its still do-able.
Hold the body of the core in place using MM method, matchsticks and if you want to abuse your mind, you'll carry on drilling through the core : )
1.41 - 1.44 - I'm not entirely sure whether the edge is on or merely in place at this point. But, if part of the advantages of a cassette is accuracy (base warp) and a great edge fit. Then a simple flat plywood mold would complete this without the need for a full cassette. Secure the plywood mold to a sheet, insert edges and base, apply pressure - usual crock clips would be fine/inserting into a press would be better.
Next step as illustrated in the clip - bending 3D edge sets is tricky by hand, for speed I think you have to go to 4 pieces.
Having done this, you could probably get away with a more general purpose cassette - a flat cassette would be possible, maybe even preferable. Inter-changeable tips molds either way - to hold tip spacers in place, but these are easy to make by hand.
Extend the tip mold 1cm or so to hold the core in place - if the base is pre-bent, it could be a bit tricky, but its still do-able.
Hold the body of the core in place using MM method, matchsticks and if you want to abuse your mind, you'll carry on drilling through the core : )
Then a simple flat plywood mold would complete this without the need for a full cassette. Secure the plywood mold to a sheet, insert edges and base, apply pressure - usual crock clips would be fine/inserting into a press would be better.
Photobucket is down ... picasa has a zoom function : )
https://picasaweb.google.com/lh/photo/a ... directlink
Advantage of this process is that you see the result before you have to glue it. Crock clips not used - just experiment, but would be used. Will need to cut a small finger hole so that it can be lifted
I'm not sure this is 'right', but it has a few advantages. It the glue used in the Line video is an epoxy, then a step like this would be a possible solution?
https://picasaweb.google.com/lh/photo/- ... directlink
User error when cutting the base
https://picasaweb.google.com/lh/photo/P ... directlink
Photobucket is down ... picasa has a zoom function : )
https://picasaweb.google.com/lh/photo/a ... directlink
Advantage of this process is that you see the result before you have to glue it. Crock clips not used - just experiment, but would be used. Will need to cut a small finger hole so that it can be lifted
I'm not sure this is 'right', but it has a few advantages. It the glue used in the Line video is an epoxy, then a step like this would be a possible solution?
https://picasaweb.google.com/lh/photo/- ... directlink
User error when cutting the base
https://picasaweb.google.com/lh/photo/P ... directlink