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"shouldering" cores for edges

Posted: Tue Jan 19, 2010 8:23 am
by alexisg1
Hello,

I feel there's not so much activity on this forum lately...so I've decided to post any questions I had 8)

So, I've seen many brands and also some amateurs machining each side of the core in order to compensate the extra height due to the edges glued on the base.

A little drawing below in case of my english is too bad to make myself undesrtandable ;)
Image

Do you think this might make the ski stronger ? Less disposed to delam ?
Do you guys do that ?
Or do you think this does not bring anything special ?

Posted: Tue Jan 19, 2010 8:55 am
by chrismp
the reason for making a recess in the core is to prevent the base from becoming slightly convex when pressing.
many people here in the forum (including me) router out this recess, but i've also read about people who don't do it and still get a flat enough base.

i don't think it makes the ski stronger, though.

Posted: Tue Jan 19, 2010 5:40 pm
by shopvac
We have cut out the "shoulder" on one pair out of 7 now. The bases have been flat on all 7 pairs though so I don't think it is necessary. To get flat bases you need a flat bottom mold for your press (and maybe a cattrack if you have a narrow or wide hose). At least that is what I can determine from reading other posts.

If you have an easy way to put the "shoulder" into your wood cores, then I think it is a good idea. I didn't have a really easy way to do it so that the depth was the same each and every time so we stopped doing it.

I think the edges just get pressed into the core so maybe the shoulder is a good idea if you are using a harder wood than ash or poplar (that is what we use).

Posted: Tue Jan 19, 2010 6:52 pm
by doughboyshredder
freehand with a laminate trimmer is easy as can be.

I didn't do it on a few boards and it visibly indented the base. Still flat as a board. ;)

Posted: Tue Jan 19, 2010 6:58 pm
by shopvac
we did it freehand with a small bosch colt "bably" router. It wasn't too bad but it was an extra step.

DBS - are you going to do it on your boards?

Posted: Tue Jan 19, 2010 11:57 pm
by doughboyshredder
yeah, for sure. I shaped my core so that the sidewalls were over the edge. Makes running the laminate trimmer by freehand super easy. You could also clamp your cut out template to the core as a guide for a router.

I do think it's a good idea to do it.

Posted: Wed Jan 20, 2010 3:32 am
by alexisg1
After having brought my skis to the skiman last week, I've seen that my base was slighly concave, and we did not made that recess for the edges...
Do you have any idea why ?
Image


I guess the best way would be to use a shaper.
DBS, can you explain to me what a trimmer is ? I have no clue :( Is it some kind of small router ?

Posted: Wed Jan 20, 2010 4:50 am
by chrismp
yep, a laminate trimmer basically is a small router.
i've used a regular router to make this recess. i just drew a line one the sidewalls/core along the inner side of the edges and then routered along that line. i set the depth of the cut by trial and error using a scrap piece of sidewall.

Posted: Wed Jan 20, 2010 6:43 pm
by iggyskier
Worth doing for sure, IMHO.

We incorporate it into our sidewall profile, which are temporarily attached to the cores before layup. After pressing, everything sits nicely.

Image

Posted: Wed Jan 20, 2010 7:33 pm
by ben_mtl
iggy -> can you develop on how you attach your sidewalls ?
Thanks !

Posted: Wed Jan 20, 2010 7:51 pm
by iggyskier
ben_mtl wrote:iggy -> can you develop on how you attach your sidewalls ?
Thanks !
Actually...sorry...but no. A few other people would likely hunt me down and kill me if I did so. It is one of the few trade secrets in here I really am not supposed to share.

Either way

Posted: Wed Jan 20, 2010 10:27 pm
by carnold
Hi
I've done both. Made no difference to the 'flatness' of the base. I now recess it for all the ones I make.
C.

Posted: Thu Jan 21, 2010 5:45 am
by ben_mtl
iggyskier wrote: Actually...sorry...but no. A few other people would likely hunt me down and kill me if I did so. It is one of the few trade secrets in here I really am not supposed to share.
No problem, it was worth a try :p

Posted: Wed Jan 27, 2010 11:28 pm
by knightsofnii
our sidewalls are profiled a few thousandths thinner than the core, to compensate for the edge teeth. Its' never really been a problem with mashing into the tip fill, just along the sidecut if we dont do it, we get the teeth dents, no problem to sand out, just an eye-sore, and yea can sometimes make for un-flat ness that can usually be ground out.

Posted: Sat Sep 04, 2010 12:27 pm
by Richuk
This is a good way to shoulder your edges, just be careful when starting as the tip is vulnerable - two passes each side and you are done. Placed a piece of mdf on top to hold the tips in the correct position on the second pass. One small slice and then another.

Image

Sorry, the photo is a really crappy - but you get the picture. Using the same jig used to make the core. I'm going to remake the jig. Template from Snowcad, smaller radius than ski.

Image

Image

Controlling the width of the cut - clamps are ok. I might end up screwing to the bench in future.