aligning base and core

[alexisg1]

hello everybody !

I've been around this website for a while now, getting as much infos as I could to build my own skis. This morning, the first pair got out of the press. Here's a picture before a more complete story.

just for info so that you dont look at them strangely, they are 140-100-125 for 170cm long.


Now my question
the main problem for us appeared to be: how to know where is the base under the core while laying ? And how to align them properly ?

What we did was :
- lay down the base on the mold and fix it lateraly with nails on the sides (head of nails did not exceed over the top of the base)
- after laying some fibers, we put the cores on top, and then we nailed some pieces of seidewalls (two on each side of the skis) to insure that the core does not slide while pressing.

The problem was
before we put air in the bladder, the core moved over the pieces of sidewalls... So when we pressed, We realised something went wrong and we had to un-build the press and nail out the pieces of sidewalls. You can imagine it's been quite a mess as the epoxy was already curing...And then we did not have any guarantee anymore that the core would not move while pressing .

I've seen the technic in the "howto guide", but still it does not insure that the core is aligned with the base right ? An we could not use this method as our sidewalls were not large enough (they were precut) to nail them to the mold.

Do tou have any wonderful technic ?



PS: sorry for my poor english...

[SCHÜSS]

i too am very interested in finding a way to align the core!

At the moment i am just painstakinly lining it all up, re-checking and checking again. im not using a prenuamtic press so its easier for me to get it aligned.. but most my designes involve <1mm or less core movement error and often its difficult and fustrating to achieve this.

if any one has a successful method please help..

schuss

[Idris]

Fix the base to the mold usind double sided tape, hot glue or other sutable method.

Fix alignment blocks either side of the base. These should let you slip the core between them, but not let the core move.

Cut notches in your composite layers for the alignment blocks. To avoid having say your lower glass layer folded up against your sidewalls and jamming your core between the alignment blocks.

Make sure you cover the aligmnet blocks in tape or wax or something the epoxy won't stick too or you have to hack them off the core after pressing (found this one out the hard way)

How tight a fit the alignment blocks are is dependent on your alignment tollerances. At Pm gear, we had 1.5mm of slop and 8mm of sidewalls, quite a bit of a saftey marging without being a pig to work with. 0.5mm was just awful to work with.

Make your alignment blocks lower than the complete height of your ski or your press won't work (not true if vacuuming).

[beansnow]

If you use inserts this could help.

The way we did it on our boards was to place two inserts into the core (one at each binding location). We then applied a small amount of crazy glue to the binding insert bottom and then layed the core down on the base and lined it up. After a second the inserts were glued to the base and we picked the core up. At layup you but the base down, your first layer of glass, cut a whole in the glass to let the insert peak through, and then put your core down and the inserts will act as locating pins for the core.

The only issue with this is that the iserts you put in below the first layer of glass end up lower then all the others which makes them look diff when you cut the holes in your top sheet. If your careful you can minimize this.

[rockaukum]

This is somewhat like the previous post. The diference being that you use what is called a spacer (available form McMasters). You place these one in the tip area and one in the tail area. Drill a hole in each location of the core. Put the spacer into the hole then align (pre lay-up) to the base. Fill the spacer with crazy glue and let set. remove the core and now you have indexing pins attached to the base. Cut the glass to slip over the spacer. This spacer will sit flush with the top sheet and be covered with the glass ect.. I'm off to ski now so I will visit later to give you the link to the Mcmaster page and I'm sure it will help with the visuals.
rockaukum

[rockaukum]

So Sorry for the delay,
http://www.mcmaster.com/
Start here and go to "standoffs" under "Fastening and Sealing".
The one to look at is the "Female Unthreaded Round with Shoulder. Then pic the size you need. Looks like they cost about $10 -15 per 100. Hope this helps.
rockaukum