NNN-BC Red Flexors

[bbense]

Back in the day ( early 90's) , people experimented a lot with this. You could buy blue and white flexors, the blue was slightly stiffer and the white was solid hard rubber with no cut-outs for "bellows". There were even people experimenting with casting them out of solid resin. I found the blue ones to be the best compromise between kick'n'glide and more control on the downhills. You can duplicate the flex of the blue ones by filling in the bellows spaces in back of the standard black ones with a flexible urethane glue.

[Nitram Tocrut]

Does anyone know a store in Canada or Europe that sells the red flexors?

I ordered some from Akers https://www.akers-ski.com/ last year and they delivered to Canada.

I use the red flexors on the Sverdrup and it makes a difference for me. I tried the black for K&G and did not notice a big difference with the red... but this has no scientific value... just a feeling

[Capercaillie]

There were even people experimenting with casting them out of solid resin. I found the blue ones to be the best compromise between kick'n'glide and more control on the downhills. You can duplicate the flex of the blue ones by filling in the bellows spaces in back of the standard black ones with a flexible urethane glue.

These ideas are great, thank you very much @bbense for the pointers.

I tried a few things, the results of which others may find useful.

I had a half-full tube of silicone seam sealant lying around. Silicone does not bond to most non-porous rubbers or plastics, so I decided to try filling in the flexor bellows with the silicone. If I did not like it, it would be easy to remove. The seam sealant had a good pouring viscosity and filled the deep bellows completely, but because it was solvent-based, I had to aspirate (poke holes with a safety pin) the silicone over several days until it was completely cured.

I decided to try the flexors with my 205cm Fischer TN66. My biggest disappointment with those skis was the lack of control when lifting the ski up to herringbone and side-step compared to all the other skis I have - even 205cm NNN in floppy soft boots. I think this has to do with the weight and weight distribution of the TN66. The other ski I have mounted NNNBC is a significantly lighter foam-core 220cm Karhu classic touring ski, and it is much better at side-stepping, herringbone, and even bushwhacking, despite the much longer length. Same boots, so it is down to the ski.

So I was very surprised to find that problem went away with the stiffer silicone-filled flexors. It was like a completely different ski, for a while. Now, just after 50km, the silicone has mostly crumbled and fallen out of the first bellows (nearest the boot) and the sloppiness returned.

It seems that the first bellows collapses too easily, and there is not enough initial resistance when lifting a heavier ski off the snow to prevent it flopping around. The silicone in the bellows that are inside the binding, farthest away from the boot, is intact. It seems that part of the flexor does not undergo any flexing, and probably has minimal, if any, effect on the performance of the flexor.

I tried filling another pair of black NNNBC flexors with a flexible polyurethane solvent-based (single component) glue - these are commonly sold as fabric/vinyl/PVC repair glues; it turns out I also had a half-used jar lying around. The glue was significantly more viscous than the silicone seam sealant, and I could not fill the bellows with any kind of consistency. It dried with a lot more air bubbles than the silicone, and started peeling off of the flexors after it dried. It was so bad I did not even bother to test these, just pulled the glue out. The worst part was probably that the dried glue, while flexible, was significantly harder than the flexor or the silicone. I don't think it would have worked even if flowed and adhered properly. I don't have a durometer, but based on descriptions and data for commonly sold silicone for mold making, I am guessing the silicone seam sealant was somewhere in the range of 20-30 Shore A, and the black flexor material is similar.

So far the best price I have found for a pair of red flexors is $40 CAD. For that price, you can buy enough polyurethane rubber to cast a lot of flexors - NNNBC, and replacements for obsolete NNN bindings. The flexors are simple enough that you can make molds out of cheap silicone caulk. Which is what I am planning to try next.