Goat-Ham-Ah project

sammer · Post by **sammer** » Wed Nov 11, 2009 9:50 pm

Ben...
I'm not suggesting you use painters tape on your bases.
at 40 psi you'll probably get good imprinting of the seams.
I'd probably use the contact paper or nothing.
The majority of the epoxy that gets on your base can be removed with a good file and/or belt sander / sanding block.
Or just base grind it off at your local shop. (If your tech doesn't mind the epoxy in the machinery)

sam

ben_mtl · Post by **ben_mtl** » Thu Nov 12, 2009 4:49 am

Well, the ski teck's gonna be my next problem... there are lots of ski shops here in Montreal and I have to find a good one to grind (properly) the bases... I believe most of the skis techs here are just students who want to have some deals on winter gear... it doesn't necessarily mean they're bad at doing base prep but odds are against them...
The list of machines I would like to source/build is expanding : CNC router, resin dispenser/mixer with temperature control, CNC edge bender, base grinder...

teleman36 · Post by **teleman36** » Thu Nov 12, 2009 3:12 pm

Ben, Nice skis. I am glad to see that you got to ski them. I take mine to my local shop that has an automatic Montana tuning machine. These machines are very expensive so you might have to find a large shop. I am friends with the owners who are quite knowledgeable about the whole skid building factory scene so they are very helpful in solving some production issues. Roy charges me ten dollars for a flattening only. No worries about epoxy on the base, everything just gets ground off, and gets a nice structure pattern also. Good luck in finding a shop with a big machine.

ben_mtl · Post by **ben_mtl** » Fri Jan 08, 2010 5:05 pm

Here are some pics of 2 of my last pairs :
The original Goat-Ham-Ah, this pair is mine, already got 5 days on them and the work great !

And my latest creation : a "rockered" ski that turned out pretty different from expected, I had the molds and templates cut a while back... I have serious doubts about how they will ride ! tip not high enough is my main concern (only 17mm before the "kick in the tip shape) Anyway they need to be tested. They were designed as powder skis but for their first ride tomorrow they might only have hardpack for lunch...

dimensions are 176cm - 142-105-128.

tip "rocker"... not much...

sammer · Post by **sammer** » Fri Jan 08, 2010 8:11 pm

Once again they look great Ben.
I think when you get them in the pow you'll be happy with that tip.
too bad you're not out west again this year.

sam

doughboyshredder · Post by **doughboyshredder** » Fri Jan 08, 2010 9:12 pm

those look pretty damn good. I think that camber / rocker profile is going to work great. That doesn't really look anything like that drawing you posted. Am I imagining it or does the sidecut go quite a ways in to the rocker?

falls · Post by **falls** » Fri Jan 08, 2010 10:48 pm

yeah looks like the sidecut runs all the way through the rockered section and ends where the little "true" tips and tails kick up. No early taper from the contact points like suggested in the other post.
and i agree they look awesome. have you got inserts and switching dukes from set to set or buying a new lot of dukes for every ski? edit: i just read you have inserts on your personal skis and 1 pair of dukes.

ben_mtl · Post by **ben_mtl** » Sat Jan 09, 2010 6:07 am

Exactly, "hawk-eye-Falls" is right : the sidecut ends exactly where the tip kicks up. I have a regular camber section about 80cm long in the middle (40cm fwd and aft of the mounting point) then the "rocker" starts.
What I had in mind for my next shape was to have a longer regular camber (120ish cm), slightly a bit more rocker (20mm instead of 13mm) and a real tip after that, not just a tiny kick... I'll develop it more in the other thread with scaled sketches to show what I plan to do.

Yeah on my personal skis I put inserts and I have 2 pairs of Dukes to switch ski to ski. I got a great deal last spring on those bindings so I got a few pairs for 220$ each, I kept 2 for me ant re-sold the other with skis to my friends I go "touring" with.

Thanks again Sam, I don't always post but your skis looks very good too. Can't wait to be back in the Koots, I'm pretty stuck now as I have to save some money and my girlfriend just started a course at the university... it just means I have 1.5 / 2 years to prepare my come back. I have to admit the ski-building activity doesn't match well with my saving objective... but my initial investment on that is almost complete, now I sell skis to pay for improvements.

falls · Post by **falls** » Sat Jan 09, 2010 7:18 am

220 is a great deal on dukes!

ben_mtl · Post by **ben_mtl** » Wed Jan 20, 2010 2:52 pm

All right, I finally found out why I end up with convex bases... the easier explanation is often the good one : the press flexes ! I had look from under the press when under pressure and found out that the small horizontal members of the lower frame actually bend.

Well the same parts on the upper frame are bending too but I don't think it's a big deal.

I didn't thought those 2x2 steel bars would bend at only 40PSI but they do !
I have to reinforce that !

I thought about 2 options :
- add some short horizontal members : adding one in every space, spreading the load on 11 members instead of 6,
or
- double the short members : welding a 1.5x1.5 on top of each short 2X2 to increase the height an minimize the deformation... I would have to notch my mold ribs to accommodate those extra parts.

What do you guys think of that ?
I was thinking of only reinforcing the lower frame as a deformation of the upper frame doesn't affect the "flatness" of the final product... good or bad ?

Jekul · Post by **Jekul** » Wed Jan 20, 2010 6:46 pm

If you send me a simple sketch of your press, including dimensions, tube sizes and wall thickness I could run it on my CAD program and determine the approximate deflection. THe Finite element analysis software is pretty accurate, and it would help you figure out what you need for reinforcements. PM me if you're interested.

On another note, does anyone know what a person should strive for in determining deflection limits? I've calculated less than 0.005" deflection on my press, but I've only pressed one pair of skis so far (with flat bases), so I'm not sure what would be acceptable.

doughboyshredder · Post by **doughboyshredder** » Wed Jan 20, 2010 7:11 pm

Steel is soft.

If you need the strength of a 2" vertical there is no need to go 2" wide, you're just adding unnecessary material. I.E. use rectangular steel. 2 x 1 instead of 2 x 2. 2 x 1 is actually a little bit stronger than 2 x 2 assuming the 2" is vertical. And, it's cheaper.

ben_mtl · Post by **ben_mtl** » Thu Jan 21, 2010 5:42 am

DBS-> Yes that's what I was thinking but I just don't know which solution will be the most effective : adding 1x2 cross members or make the existing ones beefier.
The easier for me would be to just add cross members as I wouild not have to modifiy my mold but my first concern it to get no deflection.

Also any idea if I should make this upgrade on the top frame as well ?

Jekul -> could you please send me you email in MP ? I have a sketch ready for you but I don't feel comfortable posting all the details about my press here... don't want to feel responsible if someone make a press following my plans and everything blows...

vinman · Post by **vinman** » Thu Jan 21, 2010 9:24 am

wouldn't vertical center posts (front and back) prevent that kind of deflection?

ben_mtl · Post by **ben_mtl** » Thu Jan 21, 2010 10:04 am

There are already 4 center posts on front and back, I'll get a picture of the finished frame

the deflection I noticed is only on the short horizontal yellow members (the one the board sits on in the picture...), I didn't noticed any significant deflection longitudinaly (mold ribs add stiffness in this direction)

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Goat-Ham-Ah project