I have repaired a kayak paddle that had very similar cracking in one of the blades.
The owner, who was a competition kayaker, was worried about the strength of a repair, and had been told that "it would never hold up, go buy a new blade" - "it will flex too much and fail..."
I took a look at the damage and decided on this approach:
First i flexed the blade at the damaged spot, to see which flakes of gelcoat/resin were loose enough to break them off for the repair, there really was not very much flex in the blade...
I broke off all the loose "flakes" and degreased the whole area around the damage. I used a small brush with stainless steel bristles to rough up the area. (this is a very neat way of getting a suitably rough surface on a very uneven surface!!, just make sure the brush has very fine bristles, and ONLY use it for this purpose, and clean it with solvent after each use
My other "secret tool" for this is "titanium wool" made from very fine Titanium swarf from my lathe..
unlike steel wool there's no risk of contaminating a part with rusting iron particles.. )
I then put sealant gum tape as a "barrier" all around the damaged area, with about 5 - 7 cm distance to the damaged area..
I wrapped and secured vacuum bagging film to most of the sealant gum tape around the edge, but left an opening to brush in a liberal amount of infusion resin, sealed up the bag with a silicone infusion "plug inside", mounted a hose and put a vacuum on the sealed up "bag"
I left the "setup" for about 5 hours with the vacuum pump running, then switched it off and sealed up the hose with a clamp, and left it to cure untill the following evening, so that made a bit more than 24 hours i total.
I then removed all the vacuum bagging gear. As expected the infusion resin had penetrated into the cracked areas, leaving all the cracks filled, but had also thinned out over the whole area of repair, covering it in a thin uneven layer of epoxy
That was not a real problem, i sanded the whole area down a bit, and used EC coating epoxy with a little added fumed silica to make it a bit thicker to build up the low spots.
After sanding and polishing the repair is virtually undetectable, and the owner says he can not feel any difference in the flex of the blade, it works perfectly, and as far as I know he still uses it, even though he is not doing high level competitions anymore ..
"Sapere Aude"... Dare to KNOW!
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