Section8 2013-2014

skidesmond · Post by **skidesmond** » Mon Sep 02, 2013 12:42 pm

Time to get this years thread started.

I made 2 cores back in March and they've been sitting on the work bench since. A couple of other projects got in the way. Finally got going again. Both cores are 100% ash with Ipe sidewalls. I made one core using the traditional vertical strips. The other core I shaped the center stringer first and then added the appropriate size stringers to get the desired width. I like this second approach because it makes for a faster core build. The center string is 1 piece and then shaped. Then I glue the remaining stringers and sidewalls and clamp using HD Quick Release clamps. No big HD pipe clamps, I like that. Then I profile in the normal manner (planer crib).

Using the other traditional style core making (gluing dimensional stringers) the stringer would occasionally tear away when routing the shape when ever I crossed a glue line with the router. I could have taken the time to step the router depth and make multiple passes, but seemed like a PITA.

The skis are Christmas presents for my daughters. I hope I get them done in time :-D

skimann20 · Post by **skimann20** » Tue Sep 03, 2013 4:04 am

I like your second approach. I've always been worried about tear away when crossing the glue line towards the tips and tails. (its never happened to me but always a concern of mine) When you make your rough cut before routing, how far off teh line are you. I try to keep it less than half the router bit width and I run 1/2 shank trim bits.

skidesmond · Post by **skidesmond** » Tue Sep 03, 2013 6:32 am

I've done it both ways. The first time I just plowed through the full width and depth of the center core. That's a bit scary even with a 3hp router 1/2" bit. You need to be sure the template is firmly attached to the core. But it saves a step of doing the rough cut. You could do step cutting in 2 passes but I have not tried that approach yet. Since the bearing must ride on the template
the first pass would cut through most of the core anyway.

Be sure to have a sharp clean bit and don't push too hard. Let the router and bit do the work.

I also did the rough first. You are correct to keep the cutting to less than 1/2 the width of the bit. I try to keep 2-3mm off the line.

Both approaches worked fine.

skidesmond · Post by **skidesmond** » Wed Oct 23, 2013 3:54 pm

Finally have something to show. This ski is for my daughter.

Length - 152cm
Ski dims - 117-71-104
Core Dims -2.5-10-2.5.
Poplar wood core
Ipe sidewall full width of the edge
tip/tail spacers - Poplar veneer
Steel edges
P-tex 4001 base
20 oz FG
Carbon Fiber 9.4 oz
Topsheet - cotton with epoxy and poly
Bling - Crystals on the eye sockets
Epoxy - Resin Research

I added a 3inch wide CF top/bottom from tip to tail. It turned out to be over kill. It's a very firm ski especially for such a small ski, but it should rip. I have another ski I'm making for my other daughter that will be the same w/ a different topsheet. I'll probably go 1inch wide CF.

Here's some pics:

The next will have this as a top sheet. The problem is the CF will show through.
http://desmondskiworks.com/wp-content/u ... 70x370.jpg

chrismp · Post by **chrismp** » Wed Oct 23, 2013 10:59 pm

Great looking skis! How do you apply the poly? I like the sheen it has to it.

skidesmond · Post by **skidesmond** » Thu Oct 24, 2013 3:03 am

I applied 1 coat of epoxy, lightly sanded with 220 grit. Applied 4-5 coats of exterior poly. Then lightly sand with 220, 600, 0000 steel wool followed by a rubbing compound. Maybe 1 - 1.5 hrs of finish work. It gets rid of most of the little blemishes and dust specs.

OAC · Post by **OAC** » Thu Oct 24, 2013 9:21 am

Voodoo Chile...

skidesmond · Post by **skidesmond** » Fri Dec 13, 2013 6:22 pm

Another pair ready for Christmas for my oldest daughter. Same dims as the previous pair but w/o the CF. They're at the ski shop waiting on bindings and a tuning.

Length - 152cm
Ski dims - 117-71-104
Core Dims -2.5-10-2.5.
Poplar wood core
Ipe sidewall full width of the edge
tip/tail spacers - Poplar veneer
Steel edges
P-tex 4001 base
20 oz FG
Topsheet - cotton with epoxy and poly
Bling - Crystals on the eye sockets
Epoxy - Resin Research

skidesmond · Post by **skidesmond** » Fri Dec 13, 2013 6:46 pm

Getting ready for the next pair. I'll be using Flax in this layup from BComp. They are located in Switzerland. The flax is biaxial weave at 350g. I made some samples using a single layer, double layer and a single layer w/ 9.4oz CF. Each sample had a 3mm poplar core. I thought I posted the results here but looks like I forgot. So that will be coming soon.

The ski dims:
length - 172cm
core dims - 3-12-3
shape - 125-82-108
Core - ash and ipe sidewall. Extremely heavy, the core weight w/o tip and tail spacer is 3300grams. On a good note there only 5 gram diff between the cores. The core is not shaped yet so it will be a bit less in the finished ski. The final shape will be cut out when the flashing is cut off. But they'll still be heavy.

I'll be using a double layer of flax since it's only about 12 ounces. The ski should be damp. The ash/ipe should provide enough torsional stiffness.

My veneer order came in yesterday from Certainly Wood. I bought their man-made reconstituted Oak and Teak which look great, nice straight grain pattern. Also got some kingwood and ziricote. Both are beautiful. I never heard of ziricote before but it has a creamy white/tan and black streaks.

Since this build is my "green" build I should go with the reconstituted oak or teak. Which only means I'll have to make another pair of skis with kingwood or ziricote for me :-D

SleepingAwake · Post by **SleepingAwake** » Sat Dec 14, 2013 2:12 am

Not sure if i get that right or not, but you planed to use just the biax flax as reinforcement without a uni layer? Because the biax is usually used to control torsional stiffness, and with 350gsm flax it will be already stiff with a single layer (one above, one below the core - obviously)... I would strongly recommend using a uni layer as well, just biax will probably end bad. no matter if it is carbon, glass or flax...

skidesmond · Post by **skidesmond** » Sat Dec 14, 2013 4:23 am

What do you mean by end badly? The reason I was doubling the layers is give it additional strength since it's 1/2 the weight of the triaxial FG that I normally use. My samples I made didn't give me the impression that a single layer of biax flax would be torsionally strong enough, ie it would be a soft ski.

The double layer came close to another sample I had made previously that was a triaxial FG layup of the same size.

This is my first time using biax of any kind.

chrismp · Post by **chrismp** » Sat Dec 14, 2013 1:05 pm

what he's saying is that you need fibers in the 0 degree direction (ie unidirectional) or otherwise you'll get a noodle lengthwise. but i'm guessing the carbon you're using is uni.

skidesmond · Post by **skidesmond** » Sat Dec 14, 2013 1:55 pm

Ok I get it. I was thinking the core would be stiff enough to go with out anything in the uni direction. I didn't plan on CF for this pair, however I did make a sample test piece using Flax and uni-CF. The sample piece was 3in x 30in and the CF I used was uni 9.4 oz top and bottom 3 in wide. It was too stiff. It would barely bend. I'd probably go with a 1 inch wide strip top/bottom CF. So I think I'm in a holding pattern until I can get more uni-CF.

Thanks for the info!

vinman · Post by **vinman** » Sat Dec 14, 2013 5:12 pm

9oz uni carbon will be really beefy. I used 6.7oz uni carbon and 12.5 biax glass on my last layup with a 2.2-11.6-2.2 core and could have gotten away with 4.7 uni carbon. Or could have thinned my core to 11.3 underfoot. That layup came out stiff but not unmanageable. Slightly softer would have been perfect.

skidesmond · Post by **skidesmond** » Sat Dec 14, 2013 5:19 pm

Thanks Vin! I was just about to order the 9 so thanks for saving me the mistake and $$. Did use a full width CF or just a strip? I know you use a tow also.

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Section8 2013-2014

Section8 2013-2014