to make ski stiffer

[MadRussian]

I want to make skis, as a gift to a friend, identical to MR86 I made, only stiffer.

Core 2=12=2 Maple Poplar with IPE sidewall. Only two strips of Maple for binding and 4 strips of popular.

for now I'm thinking of using few strips of carbon fiber tow

What is my best option?

[SHIF]

A few strips of carbon tow will not make them much stiffer. If you use a 2 to 3 inch wide strip of warp unidirectional carbon fiber both above and below the core along with your usual fiberglass layers you will definitely get stiff skis.
I've made several skis with your 2-12-2 profile, only varying the amount of uni carbon. It's amazing the effect this stuff has on the ski flex. I use GA090 material.

http://www.fiberglasssupply.com/Product ... brics.html

-S

[MadRussian]

okay maybe not a few. How about whole bunch? I saw K2 skis with probably 8 or 10 strips of CF tow top and bottom.
10 top and bottom will make the difference?

[vinman]

Some ways to stiffen a ski. Easiest and most cost effective in order.

1 thicker core underfoot

2 heavier glass or a second glass layer

3 add uni carbon. I do think that adding some 12k carbon tow will stiffen a laminate. I use 4-6 strings, this probably equates about a 1inch stringer of uni carbon. Each string of tow is about 3/16 wide.

[MadRussian]

Some ways to stiffen a ski. Easiest and most cost effective in order.

1 thicker core underfoot

2 heavier glass or a second glass layer

3 add uni carbon. I do think that adding some 12k carbon tow will stiffen a laminate. I use 4-6 strings, this probably equates about a 1inch stringer of uni carbon. Each string of tow is about 3/16 wide.

1. cores I made 12 mm underfoot. That's what everybody doing. Should I go with 13 or 14?

2. Two layers of glass top and bottom?

3 if 4 to 6 strips = 1 inch 10 to 12 = 2" it's still more cost-effective compared to uni CF

I don't need a lot of stiffness I simply trying to adjust stiffness for bigger person

[vinman]

13mm would be pretty dang stiff. Try 12.1-12.3. Adding .3 will stiffen things up pretty well. Or add a 2nd layer of glass just underfoot maybe 18-24" long. Taper the end to a point 4-6 inches long to feather the flex out.

[twizzstyle]

Don't do two layers of triax, they'll be way too stiff and heavy as tanks!

Adding just 0.5mm of core thickness over the entire length may be all you need.

Remember that bending stiffness is, all else the same, proportional to the thickness cubed. Adding a small amount in the center won't make much difference, but adding a small amount to the tips will make a huge difference.

For example - if you add 0.5mm to the entire profile, 2.5-12.5-2.5. The center will be 13% stiffer, but the tip and tail will be 95% stiffer!!! (i.e. (2.5^3)/(2^3))

[MadRussian]

Don't do two layers of triax, they'll be way too stiff and heavy as tanks!

Adding just 0.5mm of core thickness over the entire length may be all you need.

Remember that bending stiffness is, all else the same, proportional to the thickness cubed. Adding a small amount in the center won't make much difference, but adding a small amount to the tips will make a huge difference.

For example - if you add 0.5mm to the entire profile, 2.5-12.5-2.5. The center will be 13% stiffer, but the tip and tail will be 95% stiffer!!! (i.e. (2.5^3)/(2^3))

if I make tips and tales 2.5 mm I have to build up a thickness because tip spacers 2 mm. What the best way to do it?. Extra layer of fiberglass in tips spacers only?
how this sounds. make 2 – 12.5 (or12.25) – 2 with much shorter tip/tail spacers. This way core will be much longer and thicker across-the-board.


Separate question about CF tow. I think tow is more economical way to ad carbon fiber. What results to expect from adding tow?

[vinman]

sand the tip and tail areas to match the spacer thickness.

[Richuk]

Wood veneer is 0.6mm MR. I'm sure someone has off-cuts they could send you.

[MadRussian]

I'm going to use fiberglass mat on top of cotton for durability next time. Will it in any way affect performance?
Also if I put 3" wide strip of mat on the bottom to make symmetrical layup. How this will affect performance? Will you need to cut shoulder into the core for edges? as far weight it shouldn't be much FG mat usually under 1oz

[vinman]

no need for the mat on the bottom.

[MadRussian]

no need for the mat on the bottom.

if by using mat on the bottom don't have to cut shoulder for edges worth to use it. also mat might reduce 3x FG imprint through the basis

[twizzstyle]

I do a similar thing with a 3" wide uni carbon on the bottom. It's not quite as thick as the edge teeth, but enough that I don't bother doing any edge rebate on the core/sidewalls and get fairly flat bases (flat enough I can grind them flat). Adding a FG mat later specifically for that purpose is just adding weight.

[MadRussian]

Adding a FG mat later specifically for that purpose is just adding weight.

how much weight we talking about? FG mat is very light. I didn't like how shoulder cut out came out this time and trying to see if I can eliminate this step altogether

I had fairly noticeable imprint of fiberglass through the basis where you could see 0° and 45° fibers. Not a lot but noticeable.