of course i used mapp! hot is better, right?
one of my wood cores caught fire as i was flame treating the sidewall. the wood was extremely dry -- no doubt because it was old wood that i found in the rafters of my garage. it burst into flames within nanoseconds. anyway, the flames' life came to an abrupt end when i finally deprived them of O2 with my bare hands. left a nice black burnt mark, but skis turned out nice though.
so, any clever ideas out there about shielding the torch from adjacent wood during flame treatment? don't make me beg...
on fire
Moderators: Head Monkey, kelvin, bigKam, skidesmond, chrismp
bigKam wrote:
Rafter skis.
All of the information that I've read on the flame treating websites says that mapp gas doesn't create the proper oxidizing flame conditions for surface treating UHMW. Basically, they say that mapp just doesn't work. Also, heat isn't the goal in flame treating. What you are looking for is the right combination of propane and oxygen (about 23:1), the right location in the flame that will expose the UHMW surface to the proper flame atmosphere, and the right amount of time for exposure. The only accurate method of establishing these parameters is to do lots of testing on very smooth UHMW surfaces (not abraided) and test the resulting surface tension with actual dyne solutions. The surface energy of the UHMW must be increased to about 10 dyne above the surface energy of the epoxy (39 dynes), so 49 dyne will work, but I shoot for 60. Once you have established the proper flame/gas mixture, the proper distance from the primary cone of the flame, and the proper speed along the plastic, you can transfer all of this technique to the abraided material.
Yes, as I've noted before, many builders say that they "just pass the UHMW under a propane torch flame until water doesn't bead up" and everything works just fine. Another builder recently posted (and recommended) that going for a slightly burned/brown appearance on the UHMW will lead to successful bonding. All of this is pretty contrary to what the literature recommends for consistently strong bonding.
I have a huge file of web-links on flame treating stuff. One of them is to a manufacturer who has told me that they supply much of the ski and snowboard industry with their machines. Those machines start at about 25 grand, mostly due to the expense of a unit called a 'flame analyzer' that constantly monitors the molecular content of the oxidizing portion of the flame and gives feedback to the mixers who are constantly adjusting the gas and oxygen ratios, depending upon ambient temperature, humidity, and gas quality.
At times, I have produced just a little bit of burning/dis-coloration of the wood while flame treating (pine burns pretty easily, you know), so I sometimes just run a 6 inch piece of thin sheet metal along the UHMW/wood bond line to shield the wood from the flame. Mostly, I've noted that, at the proper speed, distance, and flame orientation, the wood doesn't suffer too much.
Let me know if you would like me to pass on some links.
G-man
Now your tearing your garage apart to build cores?it was old wood that i found in the rafters of my garage
Rafter skis. All of the information that I've read on the flame treating websites says that mapp gas doesn't create the proper oxidizing flame conditions for surface treating UHMW. Basically, they say that mapp just doesn't work. Also, heat isn't the goal in flame treating. What you are looking for is the right combination of propane and oxygen (about 23:1), the right location in the flame that will expose the UHMW surface to the proper flame atmosphere, and the right amount of time for exposure. The only accurate method of establishing these parameters is to do lots of testing on very smooth UHMW surfaces (not abraided) and test the resulting surface tension with actual dyne solutions. The surface energy of the UHMW must be increased to about 10 dyne above the surface energy of the epoxy (39 dynes), so 49 dyne will work, but I shoot for 60. Once you have established the proper flame/gas mixture, the proper distance from the primary cone of the flame, and the proper speed along the plastic, you can transfer all of this technique to the abraided material.
Yes, as I've noted before, many builders say that they "just pass the UHMW under a propane torch flame until water doesn't bead up" and everything works just fine. Another builder recently posted (and recommended) that going for a slightly burned/brown appearance on the UHMW will lead to successful bonding. All of this is pretty contrary to what the literature recommends for consistently strong bonding.
I have a huge file of web-links on flame treating stuff. One of them is to a manufacturer who has told me that they supply much of the ski and snowboard industry with their machines. Those machines start at about 25 grand, mostly due to the expense of a unit called a 'flame analyzer' that constantly monitors the molecular content of the oxidizing portion of the flame and gives feedback to the mixers who are constantly adjusting the gas and oxygen ratios, depending upon ambient temperature, humidity, and gas quality.
At times, I have produced just a little bit of burning/dis-coloration of the wood while flame treating (pine burns pretty easily, you know), so I sometimes just run a 6 inch piece of thin sheet metal along the UHMW/wood bond line to shield the wood from the flame. Mostly, I've noted that, at the proper speed, distance, and flame orientation, the wood doesn't suffer too much.
Let me know if you would like me to pass on some links.
G-man
G-man: i did read over some of the info you linked in the past about the flame treatment process. very interesting info.
i've made a couple pairs of skis in the last few weeks with uhmw sidewall, and i have a couple more pairs ready to be pressed in the next few days. so far, the flame treatment seems to work well, it's just the discoloring of the wood (and sometimes the uhmw) that i don't like. with thin cloth for the graphic layer, the imperfections show through. maybe i need to try the sub-printing method for the graphics.
anyway, i'm going to try separating the flame from the wood using a barrier. uhmw sidewalls are nice, but like the epoxy sidewalls i've made in the past, they take time. i still like wood sidewalls. simple.
kam
i've made a couple pairs of skis in the last few weeks with uhmw sidewall, and i have a couple more pairs ready to be pressed in the next few days. so far, the flame treatment seems to work well, it's just the discoloring of the wood (and sometimes the uhmw) that i don't like. with thin cloth for the graphic layer, the imperfections show through. maybe i need to try the sub-printing method for the graphics.
anyway, i'm going to try separating the flame from the wood using a barrier. uhmw sidewalls are nice, but like the epoxy sidewalls i've made in the past, they take time. i still like wood sidewalls. simple.
kam