Smooth cut finish
Moderators: Head Monkey, kelvin, bigKam, skidesmond, chrismp
Smooth cut finish
When you trim the fiberglass flash off of the pressed ski, does anyone else have a problem with short fiberglass ends sticking out all along the perimeter. I am trimming on a wood bandsaw set at a high speed with a brand new blade...and still there is a furry fiberglass seam. how do ski companies seal off this seam so impeccably? i am thinking of running a small bead of resin along the trimmed edge then stretching a layer of suran wrap over it to let it cure to a smooth, flat finish. What do people do to fix this problem?
mattman,
Are you talking cap construction or sandwich. I use a band saw to trim my sandwich skis. I end up with a slight amount of glass hairs, but they are easily removed by the grinding and routing finishing work... no sign of a hair on the finished ski.
If you are using cap construction and cutting/trimming right up against the metal ski edge (not leaving any material for finish grinding), I can see where you could get the problem you are describing. Other than band sawing and leaving a couple of mm's for finish girnding, I don't have any solutions for you. The Karhu video seems to show the workers cutting up against the metal edge, then doing a little grinding for the cleanly finished edge. Maybe they use a very fine tooth blade that doesn't fracture the resin as much as a larger tooth.
G-man
Are you talking cap construction or sandwich. I use a band saw to trim my sandwich skis. I end up with a slight amount of glass hairs, but they are easily removed by the grinding and routing finishing work... no sign of a hair on the finished ski.
If you are using cap construction and cutting/trimming right up against the metal ski edge (not leaving any material for finish grinding), I can see where you could get the problem you are describing. Other than band sawing and leaving a couple of mm's for finish girnding, I don't have any solutions for you. The Karhu video seems to show the workers cutting up against the metal edge, then doing a little grinding for the cleanly finished edge. Maybe they use a very fine tooth blade that doesn't fracture the resin as much as a larger tooth.
G-man
Could this be it?
CAUTION! Heating epoxy that has not gelled will lower its viscosity, allowing the epoxy to run or sag more easily on vertical surfaces. In addition, heating epoxy applied to a porous substrate (softwood or low-density core material) may cause the substrate to "out-gas" and form bubbles in the epoxy coating. To avoid out-gassing, wait until the epoxy coating has gelled before warming it. Never heat mixed epoxy in a liquid state over 120°F (49°C).
Found this reading west systems information...
rockaukum
CAUTION! Heating epoxy that has not gelled will lower its viscosity, allowing the epoxy to run or sag more easily on vertical surfaces. In addition, heating epoxy applied to a porous substrate (softwood or low-density core material) may cause the substrate to "out-gas" and form bubbles in the epoxy coating. To avoid out-gassing, wait until the epoxy coating has gelled before warming it. Never heat mixed epoxy in a liquid state over 120°F (49°C).
Found this reading west systems information...
rockaukum
g-man, i think you are right about the finishing they give in the Karhu video. thats what i should be doing (its a cap construction). But its not a grinding wheel they use, its some kind of belt. And the belt oscillates vertically too. Any idea what the belt is? Just a fine sandpaper? seems like it couldnt be that simple. Is it something special and thats why you called it grinding?
What kind of blade are you using? Maybe going with something with a higher tooth count would help. Is the blade heating up? Heat will kill a blade in no time.
I just cut out a pair of skis the other night and used a jigsaw. This time, I used a slow speed on the jigsaw and used oil to lubricate the blade. The blade looks much much better than when I did it before. Normally the blade would be shot after a pair of skis, but this time, it looks pretty good.
I've read that Pam cooking spray is good to lubricate blades. Spray on an wipe off excess. Another use for Pam!
-kelvin
I just cut out a pair of skis the other night and used a jigsaw. This time, I used a slow speed on the jigsaw and used oil to lubricate the blade. The blade looks much much better than when I did it before. Normally the blade would be shot after a pair of skis, but this time, it looks pretty good.
I've read that Pam cooking spray is good to lubricate blades. Spray on an wipe off excess. Another use for Pam!
-kelvin
water works good too as long as your motor isn't directly under the blade!!!!
I use a high speed die grinder with a cutting wheel and no lubricant for most of my trim.
One thing that might help is if you have the ski topside down - so you are looking at the bottom as you trim, it will tend to break the glass away from the edges. If you do the cut with the top up, the blade will work with the edge material to shear it instead of tear it
I use a high speed die grinder with a cutting wheel and no lubricant for most of my trim.
One thing that might help is if you have the ski topside down - so you are looking at the bottom as you trim, it will tend to break the glass away from the edges. If you do the cut with the top up, the blade will work with the edge material to shear it instead of tear it
Totally not following what you're saying.RoboGeek wrote:One thing that might help is if you have the ski topside down - so you are looking at the bottom as you trim, it will tend to break the glass away from the edges. If you do the cut with the top up, the blade will work with the edge material to shear it instead of tear it
As for kitchen lubricants, I've seen coco butter used in machine shops to good affect. Smells good too.
------------------Take nothing I say as expert advice------------------
if your using a bandsaw, and the ski is bottom up, your cuts are forcing the glass into nothing- basically no back support.. hence the glass doesn't cut because the resin breaks away. If you cut with the edges down, the bandsaw is using the sawblade and the edge material acting together as a shear.
That should leave minimal fibers to deal with in the final sanding
That should leave minimal fibers to deal with in the final sanding
mattman,
Yes, when I used the term 'grinding', I was referring to the process of 'edge grinding' which is often done with a machine that uses a sanding belt... sorry if I made that a bit confusing. Anyway, regarding the actual process itself, I'm supposing that many of the machines that the bigger companies are using are connected to a huge dust collection system because I'd don't often (if ever) see the operators using a respirator for inhalation protection. Most of us home builders aren't going to have that kind of equipment available, and because I'm such a geek about keeping myself as healthy as possible, I'm always looking for alternative ways to manage the health risks inherent in ski building. So, here's what I do. McMaster-Carr sells many different types and sizes of waterproof sanding belts. I use silicon carbide for sanding plastic, but it doesn't hold up well to metal. If you're using cap construction, aluminum oxide would probably work better. Then I use a cheap garden/deck sprayers (like the ones you can get at a hardware store for about $25) to spray a continual fan of water on to the belt. The water keeps the grinding/sanding residues from becoming airborne and ending up in your lungs. I built a belt sander so that the motor was a ways away from the actual sanding belt, but any sander will work as long as it's rigged so that the motor doesn't get wet. 60 or 80 grit belts work great. You don't really need an oscillating rig... just vary the areas of the belt that you are grinding/sanding on. You can put a curved surface under the belt so that you can grind curves. By the way, my band saw uses the same water system as the sander. I just spray all ferrous metal parts with clear lacquer to keep my machines from rusting. Oh, in addition to the water systems, I still wear a respirator... I have too many younger friends who keep dreaming of kicking the old man's but on the next ascent... dream on whipper snappers!!
In general:
Yes, the resin gets very fluid and runny as it's heated. I inflate the press bladder about 2 minutes before I crank up the heaters to 170 degrees F for an hour. I've never seen a single bubble.
One problem with trimming flash with the ski top side up is that you can't see where the metal edge is... easy to cut into it or cut too far away from it.
G-man
Yes, when I used the term 'grinding', I was referring to the process of 'edge grinding' which is often done with a machine that uses a sanding belt... sorry if I made that a bit confusing. Anyway, regarding the actual process itself, I'm supposing that many of the machines that the bigger companies are using are connected to a huge dust collection system because I'd don't often (if ever) see the operators using a respirator for inhalation protection. Most of us home builders aren't going to have that kind of equipment available, and because I'm such a geek about keeping myself as healthy as possible, I'm always looking for alternative ways to manage the health risks inherent in ski building. So, here's what I do. McMaster-Carr sells many different types and sizes of waterproof sanding belts. I use silicon carbide for sanding plastic, but it doesn't hold up well to metal. If you're using cap construction, aluminum oxide would probably work better. Then I use a cheap garden/deck sprayers (like the ones you can get at a hardware store for about $25) to spray a continual fan of water on to the belt. The water keeps the grinding/sanding residues from becoming airborne and ending up in your lungs. I built a belt sander so that the motor was a ways away from the actual sanding belt, but any sander will work as long as it's rigged so that the motor doesn't get wet. 60 or 80 grit belts work great. You don't really need an oscillating rig... just vary the areas of the belt that you are grinding/sanding on. You can put a curved surface under the belt so that you can grind curves. By the way, my band saw uses the same water system as the sander. I just spray all ferrous metal parts with clear lacquer to keep my machines from rusting. Oh, in addition to the water systems, I still wear a respirator... I have too many younger friends who keep dreaming of kicking the old man's but on the next ascent... dream on whipper snappers!!
In general:
Yes, the resin gets very fluid and runny as it's heated. I inflate the press bladder about 2 minutes before I crank up the heaters to 170 degrees F for an hour. I've never seen a single bubble.
One problem with trimming flash with the ski top side up is that you can't see where the metal edge is... easy to cut into it or cut too far away from it.
G-man