Deckline breaking strength?

Not sure if this qualifies as ‘over-thinking,’ but I was curious to know if folks have heard of a recommended minimum breaking point for deck-lines on sea kayaks.

As the season winds down, I’ve a few projects and was planning on replacing current deck lines with reflective 550 cord. (Which can take a load of 550lbs before failing). Thought that would be sufficient, but wanted to be sure.

Any additional opinions, thoughts or banter on the matter is greatly appreciated.



what is weakest link
in the decklines? I suppose 550 static pounds is far in excess of fittings attached to, or through deck. Knots reduce breaking strength. Sun and water will reduce too. I like the largest diameter line for ease of holding on to deck rigging. 5 or 6 mm will be plenty strong even with poor quality line. I recall some rescue drills where I was being towed. That boater had tow rope attached to deck lines. I purposed capsized to create unexpected drag which proceeded to pop loose several of his deck fittings from fiberglass.

weak link is the fittings, not the line
I have never seen deck line itself go, at least the static line. people we paddle with generally replace that regularly, and often with just typical strength stuff.

But I have seen the fittings pull out in a regular rescue no infrequently. That is what you need to be most diligent about.

thickness and slack
you are not going to break that line. Way more important is to have the right amount of slack and line that’s not too thin. Not so much slack that someone’s head can go through but plenty of slack for a hand or arm. Many stock lines come very taught and are difficult to grab with gloves. If your boat has 3 recessed fittings right in front of the cockpit, skip the middle one. Makes T rescues much easier to grab the boat.

fittings and hull
I usually see fittings fail or the deck structure fail (The deck line rips everything out).

Slack decklines are a bad idea…

– Last Updated: Sep-03-13 9:14 PM EST –

...because they make it difficult to get a firm grasp on a boat during rescues. OTOH, tight decklines that lay flat on the deck can be impossible to grab when wearing gloves.

What you want is tight, but ELEVATED decklines that you can easily hook with a gloved hand. I use 3/4" wooden beads from a craft store to elevate the lines on my boats, but there are undoubtedly other things that will do the job. They allow the lines to be taught for good control, but make them very easy to grasp.

As to the original question, the others here are absolutely correct, the fittings will fail before the lines will.

Your fingers are the weakest point
Hanging onto a deck line with a crashing wave you will soon learn your fingers , and shoulder are the weakest link. Seriously injured my left index finger hanging onto a deck line. Don’t do it.

I was wondering about that

– Last Updated: Sep-04-13 8:10 AM EST –

Doesn't take much force to do damage if your arm isn't in the right position.

Wouldn’t use 550 cord
Personally I think 550 paracord would be too small.

The breaking strength isn’t really the issue with it, although it would be much weaker than the usual 5mm cord installed by most manufacturers.

The big issues would be reduced durability and excessive stretch.


deck line tubing
consider clear plastic tubing over the bow and stern deck lines. Much easier to hold onto than thin naked deck line especially in rough water.