Ski Builders Forum

thanks for all the feedback! the carbon fiber is 11oz. im curious if instead of making the tip and tail thicker, could i just use carbon fiber in an X in the tip and tail?

What about some carbon tow just in the front 1/3 of the ski to selectively stiffen it? I've been using some CF tow instead of stitched fabric to stiffen some areas selectively.

I've been using 19oz triax with 3k tow in full length stringers and in short lengths in the tip or tail to beef things up a little as needed. I typically use 6-10 strings top and bottom depending on how much stiffness I want to add.

that sounds like a good idea at this point. I found some cheap 24k cf tow, could i use that but just less? or would that give unsatisfactory results?

24k might be a pretty thick bundle of CF. I was thinking 6k or 12k so that there would be no press thru. 8 strands of 3k would be equal to 1 strand of 24k. Easier yes, but you have less ability to spread out where you stiffen things. I like to distribute things evenly across the ski.

I was thinking of 5-7 strands of 6k would do nicely to stiffen up things selectively. I'm probably going to buy 6k or 12k tow for this season. And I still have some 3k lefty to play with also.

I've been using 24k tow for a while now, you can spread it out into a ribbon and it will stay thin enough not to show through your top sheet. (doesn't leave a bump)
3 or 4 strands will add a bit of stiffness for sure.

sam

great info sam. I was worried about the 24K being too thick. After hearing that from you I think maybe I'll go with the 12K and then fine tune things with the 3K. Something like 4-5 strands of 12K with 3K interspersed.


I also like to throw some CF or basalt strands on an angle (~60 deg or so) between the contact points to give some extra torsional stiffness for those skis that might get a bit more use on firm snow. So you get the 45 deg of the triax plus some extra strands right along the axis that the ski would twist.

So I'm back at it after a long hiatus. I made another board after this last one (sorry no pics) and it actually went well. I decided to try something a little bit out of my comfort zone. The board will be a 156 with a 6mm center and the tip and tail thinned to 1.3mm rather than 2mm. Full uni-carbon with 6" carbon x's running at +-45 at the tips and in the middle. I left out some spots in the core to fill with honeycomb to take the weight down even more. This is all to make up for the fabric and clear topsheet. Some pics

I found that I can lay out by hand much more accurately than I can tape printer sized pieces of paper together. Unfortunately the local staples couldn't print my layout to the correct dimensions.

Still using a router bridge, I can't justify a planer yet

I use permanent carpet tape to keep the core down, no issues. I originally tried making a vacuum router table but that failed.

I cut my honeycomb profile after the core was profiled just by putting it in the core and tracing around the honeycomb. I cut off the excess and sanded it smooth in the core

where it sits now, actually ready to press just forgot to take pictures of the rest. I do have a question that I was hoping you guys might be able to help with. I bought a snowboardmaterials epoxy kit a few months ago. After that I stumbled upon the cheap chinese heat blanket thread and ordered one. My question being, can snowboardmaterials epoxy be cured in the 20-30 minutes that a normal heat activated epoxy can? I'd assume it's similar to west system 105 epoxy

All 2 part epoxy systems are heat curable. U accelerate the cure time with heat. Spread some outside on a summer day in the sun.
Is the honey comb In the insert pack area? Bad idea if it is.

What MM said is not completely true. Yes, every epoxy can be accelerated with heat, but only heat cure epoxies may be heated over a certain point for the initial cure cycle. Most epoxies are fine up to 40-60°C but you will have to consult with the manufacturer to find out how much heat it can take on the initial cure cycle.

ahh gotcha. Thanks guys, I'm pretty sure its a 24 hour cure at ~21°C. I'm sure a temp around 30°C couldn't hurt. And no, there's no honeycomb directly in the binding area, just outside. There will be extra CF reinforcement on both sides of the core there as well.

Hey probs are you going to laminate that core in two steps to keep the resin out of the honeycomb cells? There is a type of fiberglass/pp veil layer that keep resin from filling in the cells from the top for one step laminating but I haven't found it anywhere. see http://www.compositesworld.com/articles ... -laminates

I'm thinking you could also laminate a thin layer of composite over just the honeycomb, let that resin gel for a few hours (facing down away from the honeycomb) whatever it takes, then either laminate the whole board or wait and sand those layers a bit if they need it after they fully cure and then lam the whole board.

I've used that resin a lot, It'll harden w/o heat but it stays sticky in the mixing bucket for several days. figure out how to add heat even if it is putting it in a box and blowing with a heat gun up to 130-140 for an hour or two (20 minutes at 160-170 is the rec'd cure), it will go a long way to a fast hard cure and will add toughness and better adhesion. Be careful not to directly heat either your vacuum hose or your vacuum bag if they are not heat-rated.

Even a few strong heat light bulbs in a small, insulated box will get you quite a bit of heat. google heat lamp box

I think I'm going to just wet out my CF on a table then put it over the core. I don't think it will drip through. I actually ended up getting a heat blanket so my heat source is covered well enough. I just didn't know if snowboardmaterials.com epoxy kit was heat curable in under an hour