Ski Builders Forum

By not shouldering and adding glass. You are only adding wt. shouldering cores not only helps with flatness, you are removing material and making things lighter...

Vinman wrote:By not shouldering and adding glass. You are only adding wt. shouldering cores not only helps with flatness, you are removing material and making things lighter...

????????????????? how much weight can you reduce by shouldering??????? 1 gram per ski??

uni CF mentioned here about 2 to 3 ounces FG mat usually .8 ounces. I don't think added weight will be that significant. My skis came out 3.7 pounds each so even if adding mat on the bottom will make them 4 pounds(which unlikely) still insignificant weight gain in my book.

My main interest in adding something on the bottom is to remove or reduce imprint of fiberglass into the basis. No shouldering could be added benefit

I could really care less what you do. Just making a suggestion. You were the one that asked the question. Which probably could have been answered on your own with some research and reading of the forum. Good luck.

sorry I didn't mean to offend you.

Dont forget the weight of the resin that is soaked in the fibreglass mat.
Routing a rebate is easy, I do it by hand. Set the depth on my laminate trimmer and run around the edge, its a 5 min job and you dont have to be all that accurate

gozaimaas wrote:Dont forget the weight of the resin that is soaked in the fibreglass mat.
Routing a rebate is easy, I do it by hand. Set the depth on my laminate trimmer and run around the edge, its a 5 min job and you dont have to be all that accurate

somehow I managed to screw that simple task up. Ms. measure incorrectly and made the channel 3 times wider

Not shouldering the cores is a valid thing to do in some cases. There are some benefits. One, if you want to add some stiffness you can add your extra layer of uni glass in between the edge teeth. This occupies the space and doesn't add any weight because you were going to add this glass and resin elsewhere anyway. In addition it adds a little more core shot protection. The big thing though is that not shouldering your cores means you don't crimp the glass up and over the edges. Your glass layer runs flatly full width. Reduces stress on the glass and maybe reduces voids in this area. Saves one step (shouldering core) but adds a step (shaping glass to fit between teeth).
Just some thoughts.
Both ways are valid.
The edge relief rebate I think helps stop core shift so if you go without it you need a solid method for core alignment.

PS. If you just use fibreglass mat I don't think it's worth it. The layer should be structural not just space occupying as that is just added weight.
Some companies use a polyurethane film/fleece in this area I think to ease production rather than structurally. There's a thread on here somewhere about this fleece. I guess it's easier to cut lots of the fleece out with the drag knife and lay it in there than rebate all the cores/sidewall, or its just a different approach.

FYI on a 183 core, a .7mm rabbet cut about 35g per ski. 30g = 1oz.

Vinman wrote:FYI on a 183 core, a .7mm rabbet cut about 35g per ski. 30g = 1oz.

thank you for follow-up.
while 30g not a big deal for skis I am making.
Decided, for multiple reasons, to go with rabbet and not make too many changes all at once before do some experiments first