Thoughts on the Nelo Cinco design: or why is the nose upside down?

It’s been around for a few months now but the Nelo Cinco is still getting comments about its strange looks so we thought we should have a dig in to the ideas behind the changes. Obviously we can’t speak for Nelo and their designers but it is interesting to look at some general boat design and learn about the thinking behind the design of the Cinco. The main change to the hull is the upside-down nose / inverted bow but in addition there are changes to the rudder, rudder hatch, the stern and some cosmetic alterations.

Here’s what Nelo had to say on the launch of the new shape:

The inverted bow (a.k.a. reverse bow)
It certainly makes the Cinco stand out but what’s the reasoning behind the move? Inverted bows mean that the furthest forward point of the boat is under water, thus increasing the length of the water line. A longer water line means better top speed.

Also, there is reduced buoyancy at the front of the boat, note that the Cinco is pretty thin up front, which is meant to stop the front of the boat being picked by waves so easily. This should mean that the boat experiences less pitch variation and runs flatter through waves, stopping it moving up and down when you paddle through waves and possibly reducing the natural bouncing that comes from paddling. The obvious problem is if the waves are too big and there isn’t enough buoyancy, the boat gets buried beneath the waves.

If you were designing a yacht then you might also be concerned that the bow would kick up a lot more spray over the top of the boat (normally the widening out of the hull deflects water to the side) but at the speed of a kayak that’s not too much of a problem, and most people would probably take the risk of getting wet if they could go a tiny bit faster anyway.

The inverted bow was popular in early battle ships and has also been making a comeback in yacht designs and military ships.

Top quality racing yachts have been taking advantage of the inverted bow already, apparently the main benefit to them is the reduced pitch, reducing sea sickness and making operation easier.

Inverted bow on Team Oracle Yacht

Team Oracle’s Americas Cup Yacht, with inverted bows. Photo Robert Couse-Baker.

Cut off stern
New to the Nelo range is the cut off end, rather than coming to a point at the back there is a flat section. We’ve see it on kayaks before, the Roman Sail Paul used to paddle has the same thing. But what is the point to it? The cut off end will reduce wetted area slightly but also create a bit more turbulence, so there’s a trade off that’s really hard to balance. There can be some changes in handling that could make steering a bit better, and it also allows a little extra volume near the back which should help with pitch reduction again.

Thinner rudder
A no-brainer really; quite why kayak rudders have been so fat up till now is hard to explain! Reduced cross section means reduced drag, and as long as it’s still stiff enough to actually steer with you’ve got nothing to loose.

As with all boat design its a complicated problem, and the only real way to decide for sure is to go out a paddle one in different conditions! They’ve also upped the game a bit cosmetically and also made the rudder hatch easier to open, but that’s not so exciting.

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