How long is long enough?

The Darkness C1 is designed to conform to the International Canoe Federation (ICF) specifications for racing. This means paddlers can legally race in UK Hasler events and any other races which are sanctioned by the ICF.

However, many of the classic races (DW, Watersides, Thamesides, Ross Warland etc) and decents are not subject to these restrictions, which means The Darkness at 5.2 metres long, is at a disadvantage to longer boats such as the Wenonah J203 at 5.6 metres.

Apparently that additional 0.4 of a metre makes a difference as “Any hull has a “hull speed” equal to 1.34 x square root (length of waterline in feet). That basically tells you that as long as the hull is acting as displacement hull, the longer the hull, the faster the boat. The calculation is the length of the wave which is generated as the boat moves through the water.”

So, looking at the formula applied to various craft:

The Darkness: 1.34 x square root of 17’ = 1.34 x 4.1 = 5.525 knots
Wenonah J203: 1.34 x square root of 18.5’ = 1.34 x 4.3 = 5.764 knots

Clearly this is very simplistic as there are many other factors which influence overall race speed, especially portaging. The benefit of a faster water speed by a longer boat may be negated if it is awkward and heavy (and slower) to portage.

Another factor is of course the payload.

I have seen pictures of unusually long kayaks/canoes in some of the US ultra-mileage races especially the Texas River Safari (260 mile race to Seadrift from the headwaters of the San Marcos River) and have been intrigued as to whether they actually do go faster. I’ve decided to test the theory for myself.

The first thing I need is a longer boat, but one which I can test against a benchmark. So, I decided to elongate one of my Darkness C1s by simply cutting it in half, extending the distance between the bow and stern, and then filling in the missing middle section.

I decided to extend the 5.2 metre boat by an extra 1.3 metres making it a total of 6.5 metres. This is the same length as an ICF C2. If it pans out as I expect it to, I may also have a slim C2 which should support a couple of racing snakes.

So the theoretical hull speed should be – The Darkness elongated: 1.34 x square root of 21’ = 1.34 x 5.6 = 6.141 knots

Before I did this, I needed to construct a “cradle” to support a pseudo mold to bridge the gap. So I found the widest part of the hull and used this as a pattern for five 14cm strips of fibre glass to profile the hull. I then attached these to two long pieces of timber at regular intervals to add an additional 1.3 metres to the boat.

Completed cradle

Having constructed the cradle, I now needed a thin, pliable sheet of material to form the hull shape using the cradle for support. I thought of lino, or a thin sheet of plastic or even a sheet of aluminium. Whilst I was considering the next move, I had to go to Oman on a week’s business trip.

Coincidentally I had placed an order on my boat builder for a C1, but it was taking longer than usual. It transpired that he has used a new type of gelcoat which had “gone wrong”. He had built a replacement, but the question was what to do with the surplus boat. So instead of cutting up my beautiful, resin-infused carbon boat, we used this one instead, as the elongated candidate.

We still felt bad cutting up a perfectly (but flawed) useful boat but there’s no way I could have sold it.

The next step was to connect the two halves with the cradle and use this to support a pliable sheet. We tried a thin sheet of fibre glass, but it sagged between the spars, so we abandoned this method.

I’m not sure how it was achieved in the end, but how ever it was done, it worked although it was not pretty.

I was keen to compare it with a Darkness C1 and was a bit disappointed to see how it had flared out much wider than I wanted. The gunnels were finished off and I asked for the standard Duet flanges along the inside to support seats and footrests. This really improves the longitudinal rigidity, but also across the width once I brace it with seats and footrests.

I first wanted to try the C1 option, so I installed a single seat just behind the centre of the boat. I used aluminium thwarts to bring the sides in, and they are internally braced with threaded bars with nuts and washers on either side to ensure that the shape doesn’t pop out again.

I added an additional brace towards the rear of the flanges.

I’m now a lot happier with the width, The widest distance between the edges of the gunwales is 54 cms. The Darkness C1 is 51 cms and the Duet is 67 cms. So theoretically it should be a stable C1 and a less stable C2.

IF I go into production, I’ll increase the size of the rear deck and reduce the open section to 3 metres.

I’ve had to raise the footrests a bit as the flanges are the same height as for the C1 seat.

Obviously I had to compare it to the rest of the fleet.

Extra long single boats

The next thing is to try it on the water and compare the speed and performance with The Darkness C1.


3 thoughts on “How long is long enough?

  1. John Erskine

    Hey I love reading about your boats. I’m in Texas and have owned all three of the Texas boats in your picture above. The Duet and your C1 would both be great boats in the TWS in my opinion. Love reading your updates and your progress. ~ John

    1. nickadnitt Post author

      Hi John, many thanks for the feedback. I’d love to do the TWS but simply can’t afford it. I do find some of the American boat innovations very inspiring though, and it would be interesting to have a go in a few. Best wishes Nick


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