G-man's skis and press

[G-man]

Well, the summer heat has finally arrived to the Northern Sierra and is doing a number on the snow conditions. So, I now have time to post some pictures. Thanks again to Collin and Hose-man for the picture posting tips.

I started on this ski building adventure about the middle of last November. It took 5 months and about $5,000 to get the first pair built... to say nothing of the hundreds of hours spent building all of the needed equipment, jigs and fixtures. But, those first couple of turns on the home-made skis made it all worth the effort.



This is the first pair of skis I made, finished about the middle of March, but not skied until early April because of a shoulder injury. They're 140/108/130. They have about 16mm of camber and are made with Ponderosa pine cores. They have a fairly soft flex which, IMO, is pretty appropriate for a wide ski... wide skis are meant to float in soft snow, whether the snow is light or a bit on the heavy side, and they need to de-camber fairly easily when edged and weighted in order to acheive that smooth, round flex that results in a smooth, sweet turn. These skis were unbelievable in late season powder and early spring wet snow that hadn't yet transitioned to corn. I mostly use my skis in the backcountry and I wanted a tip shape that would hold a skin loop. So, I went with the 'old fashioned' pointy tips... love 'em. Weight is 4 lb. 3 oz. each.








I built this pair for a friend, Steve, who skis AT. They're 125/92/15. They have a full layer of 5.7 oz. uni-directional carbon between the base and the core, laminated with a layer of bi-directional fiberglass. They are quite a bit stiffer than the first pair. I made a set of adaptor plates so that I could also mount tele bindings on them (all of my skis, so far, have inserts). Steve and I both love these skis. They ski corn like a dream... very easy to feel 'one' with these skis. Ponerosa pine core. I got rid of the twin tips on this pair... they just get in the way in the backcountry (cool rooster tails at speed, though). Weight is 3 lb. 11 oz. each.








This is the most recent pair. It's the same size as Steve's chili pepper skis, also uses Ponderosa pine. This ski is super stiff...much stiffer even than the chili peppers, maybe because the core is about 1 1/2mm thicker (13mm/3mm). It handles 45 degree slopes on 1 to 2 inches of early morning corn soooo well... edges like crazy. I wanted to experiment with binding location, so I added a mount position 4mm forward and 4mm rearward from where I had calculated the sweetspot to be. Turns out that my calculated position was pretty perfect. Haven't weighed this pair yet.








Here's my press. I didn't want to have to load a big, heavy cassette into a closed press frame, so I made the press so that the upper mold could be raised up out of the way. The ski components are then placed into the mold while it's in the press. The upper mold section is then lowered and pinned into position. Most everything else about the press is a conglomeration of stuff that I got from this site or from graf's site. The mold length is adjustable from about 195mm to 155mm.







The next few months will be spent building a new shop, cause I've outgrown the present one already, and transitioning from skiing to bike riding for the Summer and Fall seasons. I'll continue to play around with lots of ski construction durability testing. Hopefully, the new shop (dedicated primarily to ski building) will be usable by mid-November. Then, I'll be cranking away on the skis, again. What an amazing past few months this has been. Thanks again to Kelvin, the Kams, and everyone else who has shared their ski building experiences on this site.

Big Cheers to all,

G-man

[Mutombo]

5000 $!!! My god, when I read this it really hurts me but now looking at your pictures I can see the answer to this question. It´s the most proffesional press I´ve ever seen.

[collin]

Very nice.

[iggyskier]

Looks great! $5,000 is quite a bit of cash...

how does the camber of your mold change as you adjust the length?

[G-man]

I should clarify that the 5 grand didn't all go into the press. Actually, the press by itself was only about $1,300... 500 for the steel, 150 for the heaters, 150 for the electronics, 200 for all of the grade 8 bolts, 100 for the bladder, 100 for MDF, and I'm sure that there's another hundred in misc stuff. Then, I bought enough of the above same parts to build a smaller test sample press that can also function as a die sublimation press down the line. I got a little carried away and bought 10 Dewalt routers (about $2,000 right there) so that I would not have to be changing cutters and router set-ups all the time when I get going on more of a small production scale... pretty much everyone who skis these skis doesn't want to go back to their factory skis, so, I potentially have a lot of skis to build. Then, there is all of the other tools, jigs, fixtures, templates, plastics, composites, resins, edges, inserts... actually, I must have quite a bit more than $5,000 into it. I hope my wife doesn't read this... she doesn't look too mean though, does she??



Besides, I haven't built her a pair of skis yet, and she really wants a pair.


iggyskier, so far, all of the skis that I have built have been the same size. When I do build a different size, say 10 mm shorter, both the tip and tail blocks will be moved 5mm each towards the center of the mold. Given that I have about 12 mm built into the camber block over a length 180mm, adjusting the length of the mold 10mm should change the camber less than 1mm... in theory. I'll just have to try it and see what happens. There are so many variables in pressing a ski. So far, all of my skis can be placed back into the mold and they fit like a glove... beginner's luck? By the way, when pressing, I let my temp guage get up to 170 F, then let the skis cook for a full 60 minutes, then pop them out while they're still too hot to handle. Then, I have to wait until the mold cools down completely before laying up another ski... don't want to add any heat to new batch of resin before I get the press buttoned up for pressurizing.

G-man

[iggyskier]

I got a little carried away and bought 10 Dewalt routers (about $2,000 right there)

.........

..............

wow. Umm.....wow

I can see the reason for it, though.

any important tips you have regarding the whole process. I am in the process of building my frame right now, so still have loads more to go.

regarding cash, I am expecting it to cost about $3,000 to get all the tools needed and the press + heating blanket.

[iggyskier]

two more q's....

what epoxy due you use and what psi do you usually press at?
How did you determine your mounting point?

[kelvin]

g-man,
Very impressive. What is the final camber of the skis? Are you having any camber related issues with the heated press?

Thanks for the pictures. Nice work, again.

-kelvin

[hose-man]

G-man!! excellent!

In addition to the above questions I would like to hear some specifics about your heating system. Did you mimic the K's set up or do you have a different angle? Where did you purchase your heating blankets? I'm probably going to abandon the ghetto heater & get some blankets going.

[G-man]

Okay...

iggyskier,

I use QCM's EMV-049 resin with the ECA-048 hardener. Keep in mind that you MUST heat this mix to at least 150F or it will just crumble like sugar candy... and so will your newly pressed ski. Also, consider that the thicker and wider portions of the ski take a bit longer to get up to temperature, so it doesn't hurt ot cook the ski a little longer just to be sure. I leave mine at 170 for an hour so it gets done through and through. I did a buch of small test pieces using this resin combination, and when cured properly, it's really tough stuff.

Regarding mounting point... there are 3 main parameters that need to co-incide in order to find the nirvana turn. Number one is to locate the narrowest point at the waist of the ski... basically, that's the side-cut arc center. Sounds easy, but it's a bit tricky to find the exact spot... well, I try to get it at least within a cm or so. Number two is to find the flex arc center of the ski and get that point to match up with the side-cut arc center. I built a 'flex analyzer' to find this spot. Basically, it's an 8 ft. by 16 inch piece of MDF that has a 20 foot radius arc cut into one edge. That piece of MDF is mounted into a couple of end stands so that the curved edge is oriented up. Then, I mount a ski on top of the fixture and roll a weight back and forth until I find that spot where the arc in front of the weight and behind the weight has the same curve. That spot needs to match up with the side cut center. If it doesn't, you have to alter your profiling dimensions until it does. I've noticed that core thickness effects the location of the flex arc center, and I would assume that wood type may effect it, also. It's just a matter of trial and error to get it right. Third is to match up the pressure center of the ski boot with the side-cut and flex arc centers. The pressure center of an alpine boot or alpine touring boot is pretty straight forward... it's generally marked on the boot. Tele is a different matter for a number of reasons. First, there's no mark on the boot. Second, everybody weights the forward and rearward boot differently in a tele turn. Most tele skiers really don't get much weight over the rear ski, so, since most of their weight is on the front ski, they'd do better just to mount alpine method. Tele mounting is always going to be a compromise is some way. ScottyBob solved part of the problem by making one edge shorter than the other, but, those skis still have to compromise in respect to the flex arc center, even more so than a traditional ski (I happen to feel that the flex arc center is more important in a turn than the side cut arc center, FWIW). But, for the sake of this description, I'll assume that we all weight our tele turns with 50% of our weight on the front ski and 50% on the rear ski. So, basically, I make a mark on my boot at the mid-point and at the ball of the foot. Then, I split the difference between those two marks, make another mark at that point (my compromise location) and line that mark up with the side cut arc center and the flex arc center. Then, I place my inserts accordingly. Hope that's not to confusing.

Uh-oh... I just got a call from a neighbor that a forest fire has just started up about a quarter mile away... got to run. I'll finish this later.

G-man

[G-man]

Okay, I'm back. Sorry about all the drama. We've had lots of lightning storms the last 3 afternoons resulting in about 50 different fires within 10 miles. Two of 'em got going today within 1/4 to 1/2 mile of our house. Crews will work on them through the night, and we'll see where we are in the morning.

Anyway, where was I...

Kelvin,

I have 16 mm of camber built into my mold (I made an errror in an earlier post when I stated that I had 12 mm), and the skis come out with 16mm of camber, give or take a mm, or so (close enough that it's tough to measure any significant variation). I know that my results are not consistent with results that other builders are getting, and I don't have a good answer for why that is. Initially, I had hoped for about 8 mm of camber in the ski, so, based on other builder's reported results, I doubled it and built 16mm into the mold. Actually, I like the way the 16mm cambered ski performs. It seems to be a lot more lively than a near zero cambered ski. Most years, we don't get a lot of nice, dry powder in the N. Sierra, and that's the type of snow where camber might be undesirable. In firmer snow conditions, it takes very little weight to decamber one of these skis, but that weighting seems to preload the ski just enough that it gives back a bit of energy at just the right time in the turn... makes the turn "flow like water".

I have noted, however, in some of the sample testing that I have done, that using different composite combinations, weights, axials, etc., seems to effect whether the test piece comes out of the test press flat, or a bit concave, or convex. It seems to stand to reason that a particular composite lay-up might well effect camber changes from mold to finished ski. Again, my actual finished ski results have been quite consistent. I'll just have to build more skis before I can have a good sense for why this is.


hose-man,

Mostly, I did mimic the K's heating system... with a few twists. I got my flexible silicon heaters from www.hiheat.com. (click on 'catalog heaters'). They offer a number of off the shelf units for 40 or 50 bucks. Only problem is that the longest size is 40 inches. I tried to get an expensive custom made unit form a couple of other companies, but they just never came through. I got tired of waiting and just ordered a couple of units from Hi Heat. I got the 3 x 36 incher's for about $50 each. I routed a 1/16 inch deep relief into my mold base, placed the heaters with lead wires sticking out both ends of the press, then placed two layers of .040 aluminum sheet (7 inches wide) over the top. I left a 2 inch gap between the heaters at the center of the mold and attached my temp sensor in that gap. Basically, the heaters heat up the aluminum sheets (great heat conductors), which, in turn, heat up the ski. The 3 inch wide heating units work so well that I'm quite sure that the 2 inch units would work just fine... and for about $30 each off the shelf. If a heater should go bad for some reason, you can just call up Hi Heat and order another one. It just takes about 3 days to get them. Pretty cool, eh? Yes, ditch the ghetto heater. Keep in mind, though, that even though these heaters are pretty cheap, the electonics could run you a couple hundred bucks by the time that you're up and running. Also keep in mind that all I do is button up my press, inflate the bladder, flip a switch, and walk away for an hour. The electronics bring the heat up to 170 F +/- 2 degrees and keep it there... very nice.

Like the K's, I also got my PID controller and solid state relay off of e-bay. In fact, I got two of each, one set for my ski press and one set for my test press.

I guess that's it for now.

G-man

[G-man]

Okay, I'm back. Sorry about all the drama. We've had lots of lightning storms the last 3 afternoons resulting in about 50 different fires within 10 miles. Two of 'em got going today within 1/4 to 1/2 mile of our house. Crews will work on them through the night, and we'll see where we are in the morning.

Anyway, where was I...

Kelvin,

I have 16 mm built into the mold (I made an errror in an earlier post when I stated that I had 12 mm), and the skis come out with 16mm of camber, give or take a mm, or so (close enough that it's tough to measure any significant variation). I know that my results are not consistent with results that other builders are getting, and I don't have a good answer for why that is. Initially, I had hoped for about 8 mm of camber in the ski, so, based on other builder's reported results, I doubled it and built 16mm into the mold. Actually, I like the way the 16mm cambered ski performs. It seems to be a lot more lively than a near zero cambered ski. Most years, we don't get a lot of nice, dry powder in the N. Sierra, and that's the type of snow where camber might be undesirable. In firmer snow conditions, it takes very little weight to decamber one of these skis, but that weighting seems to preload the ski just enough that it gives back a bit of energy at just the right time in the turn... makes the turn "flow like water".

I have noted, however, in some of the sample testing that I have done, that using different composite combinations, weights, axials, etc., seems to effect whether the test piece comes out of the test press flat, or a bit concave, or convex. It seems to stand to reason that a particular composite lay-up might well effect camber changes from mold to finished ski. Again, my results have been quite consistent. I'll just have to build more skis before I can have a good sense for why this is.


hose-man,

Mostly, I did mimic the K's heating system... with a few twists. I got my flexible silicon heaters from www.hiheat.com. They offer a number of off the shelf units for 40 or 50 bucks. Only problem is that the longest size is 40 inches. I tried to get an expensive custom made unit form a couple of other companies, but they just never came through. I got tired of waiting and just ordered a couple of units from Hi Heat. I got the 3 x 36 incher's for about $50 each. I routed a 1/16 inch deep relief into my mold base, placed the heaters with lead wires sticking out both ends of the press, then placed two layers of .040 aluminum sheet (7 inches wide) over the top. I left a 2 inch gap between the heaters at the center of the mold and attached my temp sensor in that gap. Basically, the heaters heat up the aluminum sheets (great heat conductors), which, in turn, heat up the ski. The 3 inch wide heating units work so well that I'm quite sure that the 2 inch units would work just fine... and for about $30 each off the shelf. If a heater should go bad for some reason, you can just call up Hi Heat and order another one. It just takes about 3 days to get them. Pretty cool, eh? Yes, ditch the ghetto heater. Keep in mind, though, that even though these heaters are pretty cheap, the electonics could run you a couple hundred bucks by the time that you're up and running. Also keep in mind that all I do is button up my press, inflate the bladder, flip a switch, and walk away for an hour. The electronics bring the heat up to 170 F +/- 2 degrees and keep it there... very nice.

Like the K's, I also got my PID controller and solid state rely off of e-bay. In fact, I got two of each, one set for my ski press and one set for my test press.

I guess that's it for now.

G-man

[iggyskier]

one last question - what psi do you press you skis at?

also, hope you house/area is ok .

I am currently living in WA for school, but my home is in the mountains outside Boulder, CO. Our home came very close (about 1/4 mile) to being caught in a forest fire a few years ago. Very scary expierence. Fires suck. Hope all is well.

[G-man]

Sorry about the double post everyone. I Don't know how that one happened.

iggerskier,
I meant to answer that question earlier, I just spaced it out. I press at 50 psi. I don't know why that appears to be the magic number, but everyone else seems to press at 50 psi, so that's what I chose. Once the press is inflated to that point, it's quite easy to get a sense for just how much pressure 50 psi really is... it's huge. The bladder gets hard as steel. I wouldn't want to go anymore than 50, and I really think that one could get by just fine with as little as 35, or so, psi.

Thanks for the thoughts on the fire. The smoke is so thick this morning that I can't see but 2 or 3 hundred yards. It's weirdly quiet. I'm going to get on my bike and go check things out.

G-man

[Buuk]

Looking great G-man!!

I read you are pressing at 50 psi (about 3,5 bar). Does there squeeze many epoxy out of the skis while pressing? I designed my press to a maximum of about 90 psi (6 bar), so I'm wondering if more pressure will be better (and create a lighter ski) or that it will only squeeze more epoxy out of the skis so the bonding between the layers will be weaker.

Buuk