Hi,

I have quite a fragile, well defined edge on my carbon-kevlar kayak that I need to repair but it seems more fragile than necessary so I'm looking to make some modifications from the original construction to improve the impact resistance of the area.

I've attached a photo showing the damage and geometry (sorry, the camera doesn't seem to have focused on the edge so the damaged isn't in focus but hopefully you can see enough).

Instead of just patching with some more Carbon-Aramid 188g weave (which I believe it what the original construction is), I was considering patching the entire edge with 300g Aramid cloth, overlapping the corner by about an inch either side, and then adding a Heavyweight 400g Kevlar Flat Braid over the edge to add further abrasion resistance. Would you consider this a reasonable plan? Also, will I be able to maintain the geometry of the edge doing this? I want to improve the damage resistance of the boat and reduce the  need to keep adding patches (which will add weight and affect the bow/stern balance) but also don't want the modification to be unnecessarily heavy either.

Also, I've heard that some composite kayak manufacturers have started using a flexible resin on carbon or aramid braids to improve impact resistance. Would you recommend using a flexible resin like EF80 Flexible Epoxy Resin if using a Kevlar Flat Braid over the edge? I'm currently using Epoxy Rapid Repair Resin.

Any suggestions appreciated.

Thanks,
Nick

Your plan to use the extra aramid, both cloth and flat braid is a pretty sound plan.  Combine that with the Epoxy Rapid Repair resin you already have and you should have a strong repair.  Certainly the move from a hybrid fabric to a pure aramid will improve abrasion resistance and to a degree the impact resistance, bearing in mind the original material is still beneath.

The advantage of using aramid in this way is it can be replaced with the same again once it is worn away in future. In effect it can be a sacrificial area to prevent the main structure underneath being worn away.

We wouldn't recommend EF80 for such an application as it is very flexible compared to a rigid epoxy.  Rapid Repair resin has a high flexural strength which means it will flex more before failure when compared to other epoxies.

Warren Penalver
Easy Composites / Carbon Mods - Technical Support Assistant

Thanks Warren.

there is also a material from Kraiburg in germany that we have been using, its a rubber like material that you can use within the laminate to improve impact resistance.