Fixing carbon blades

If the foot pocket side comes off, the blade will brake for sure,
there is no way around it.
This c-4s last a looong time.
Mine are still kicking after many years.

Looks like it broke along the line of the holes, they must have weakened the material along that line. The only way to salvage something is to cut that piece off and shape the back of what's left to fit in the pocket. You'll get a shorter straighter blade.

Were the holes made exactly where the blade bends?

There's two methods of making carbon fiber parts. One is the ''wet'' carbon method wich is similar to working with fiberglass in that you soak the carbon mat or roving with resin and let the part cure and then trim/finish etc. This method is used for parts that you want to have the carbon look but it's not as strong and lightweight as the other method wich is ''dry'' carbon in wich the carbon part it's bonded(resin and mat/roving) using a vacuum and put in an autoclave to cure.I have no experience with carbon fins but i would assume they're made using the ''dry'' carbon method wich it would be giving the application very if not impossible to repair.

i dont know if they are the same model and type but here it says they sell separate

http://www.scubasworld.com/products.php?cat=108

it doesnt hurt to call and find out. good luck,

I don't use screws on my carbon fins. They are hold in place by the tendons alone and some black 5200 which runs all along the very edge of the fin. If you do a little searching you will see that many people manufacturers included recommend using super glue to hold the blade in the footpocket by placing a drop in key areas. I am sorry to hear the blade broke but I am sure you can purchase them individually at www.scubasworld.com.

Quote from monster slayer

yup, they came mounted on Omer milleniums

It's said that holes in carbon will weaken it. I'm don't think 2 holes in a flat area will weaken the blade to the point of it snapping along that line under normal use, still much better chances with just one hole. All of you should realize that there's no necessity to have 2 screws securing the blade into the f/p. But 2 holes along an obvious high stress line such as the bend in the blade is not smart. Anyways as far as securing the blade in the pockets it's best when the f/p tendons snap well onto the little rubber rails on the blade. Then you don't need anything else, maybe at most a few drops of glue.

5200 BTW is nothing but a sealant which fills up space. It helps a tiny bit as far as eliminating the space to have something wiggle itself free. Instant glue actually bonds.

As far the strength and durability of today's carbon blades here's a little test I did on ours.

Video: Carbon fin test

sorry to hear about your problem. I also think the problem was that the holes were right on the bend. I owned c4s briefly and I the holes were placed well above the bend. C4s are good blades, it's too bad that this is leaving a bad taste on carbon blades for you, you should try other brand.

the holes is also becoming a thing of the past, for obvious reasons, I like the screwless installation of the Carbonteks and now OMER. I glued a palstic tab on the bottom of my CTs, slid them into the OMER pockets, tab goes in, then glued the tips of the pocket tendons to the rubber rails, they aren't coming off.

here is a picture of my C4s, note the hole placement.

did you get the blades from a store or a second hand buyer? I'm thinking the screws were done place incorrectly on those blades

oops, wrong picture, those are the Cts before I used the tab system,

here are the old C4s,

5200 BTW is nothing but a sealant which fills up space. It helps a tiny bit as far as eliminating the space to have something wiggle itself free. Instant glue actually bonds.

This is what I have always used and no problems yet. Pablo from Spetton was who directed me to use this high strength marine adhesive/sealant. Plus since it doesn't actually bond (as pargo mentioned) you don't destroy the tendons or the blade rail upon removal when swapping blades.

Yes that's the whole point, that it doesn't destroy everything if you want to disassemble it later. The idea I was trying to get across is that it does it's job as far as keeping the blades in the pockets by something close to suction. I wish there was an adhesive slightly weaker than instant glue, that would be perfect. But I think in the case of rubber and fiber real adhesives either bond or not. Now when I say bond I mean that the two materials become fused together to the point that if you try to pull them apart they'll break at another point other than the bond. In the case of rubber and fiber obviously the fiber will not break so the rubber gives way. Sometimes it will let go at the bond and other times it will tear. It would be very good to find a middle ground. Or something that will dissolve the bond and not stain either rubber or fiber.

In Europe they use sikaflex or something along those lines. I know of people that use 4200 rather than 5200 because it has a weaker bond making it easier to remove.

From an engineering standpoint that is the best combination to insure failure. A hole by itself weakens the local area by a factor of atleast three and combine with the bend it has a similar additive effect.

What makes the blade strong is the carbon fiber. The epoxy just keeps it all together. Since all the fibers are broken in that critical section the epoxy will do very little.

When you guys say that you use instant glue ,do you mean like ''crazy glue''? Because if that the case that means that the glue is ''CA'' (CYANOACRILATE) based glue and therefore you could go into a hobbyshop that caters to modelers(rc airplanes/boats/cars) and buy what we call ''CA''. It comes in different thickness, meaning thin/real watery, medium/like thin syrup and thick/like gel.There is also a liquid called ''acelerator'' to make it (the ''CA'') cure/set faster and also a ''debonder'' for when you need to disasseble. Hope this help you guys.Just my 2 cents.

i use black silicone. Works great! Im sure 5200 and 4200 work great too. I would try out 4200 first in black of course.

You never need to use screws. :nono: