Tuesday, April 01, 2008

Kaya-Jet review

Over the last year the staff at seakayakphoto.com have been doing quite a lot of paddling in tidal waters. Robert Burns our National Bard wrote "Nae Man can tether time nor tide..." and he was right.

We have often been frustrated when slow service in a sea kayaking pub has delayed our departure and caused us to miss a tidal window. It's no fun battling through even a short tidal channel against the flow and you certainly don't want to hang around until the tide changes. Another scenario involved an attractive looking pub at the head of a sea loch with a narrow entrance out of which the ebb was pouring. We paddled like fury but got nowhere, we had missed the tide and were just about to miss closing time. What was required was a little lateral thinking.

Have you noticed how the capacity of rechargeable NIMH batteries has been creeping up?

Now imagine ten of these babies in series in a battery box snug in your day hatch. Yes that makes 27amp hours of juice! That's easily enough to kill a herd of elephants!! What would you do with that amount power? Play all 8000 songs on your iPod? Well more lateral thinking is required.

Rule have just released a 12v 5000 gallon per hour bilge pump. That's over 5 litres per second. Or put another way, 300kg of water shifted every minute. A plan was hatching. I took my ideas to Geoff Turner at Kari-Tek...

An intake was drilled in the cockpit floor behind the seat. Geoff made a moulding into which the pump fitted. The outlet hose runs back through the day hatch into a nicely faired tube at the front of a modified Hydro Skeg box. It points back... YES the Kaya-Jet was born!

Tony and I took a Kaya-Jet equipped Nordkapp LV to our favourite tidal playground in the Sound of Luing. At full spring ebb it just wasn't possible to paddle uphill against the tide. Tony tried about 6 times, I tried about 3 and we were both knackered.

Now the real test. Tony pressed the 25amp switch and whoosh, the kayak surged forward, he still paddled as hard as he could of course, but the difference was he was through the channel in less than 45 seconds, all together the pump had only run for just over 90 seconds! Success!

In further trials on the measured mile in the Clyde (note the white transit posts on the hill) we have found that the pump draws about 15 amps average over the mile. That means it will run for nearly 2 hours!

Geoff had also built in a slider into the moulding that the pump intake sits in. If you are out of the boat after a capsize, slide the slider to port. This closes the under hull intake and now the pump sucks from the cockpit. Renter roll and your boat is full of water but now you have the most powerful pump on the planet and it empties in a jiffy at the same time as supplying forward thrust! One caveat for gentlemen, I wouldn't risk firing up in pump mode if you are wearing only loose boxers. There's a lot of suction down there!

I know this is only a prototype and I have to declare a vested interest but, all the same, I award Kaya-Jet, this innovative new design, 10/10.

Already I can hear the howls of protest from the traditionalists, who chew their own catgut to stitch their skin boats together. I do not mind, sea kayaking is a broad church and I am certainly not a traditionalist!

Look out for Kaya-Jet in a kayaking store near you in about 18 months time. If you really can't wait that long, we have another prototype that need testing with a bigger pump and more batteries!


  1. Sounds fun but Im not entirely convinced about your dissapointed of not been able to get out the pub before the tide gets away. Has the inability to paddle into the tide any link to how much you drink in the pub ?

    All the best - Glenn

  2. Was the new Rule pump by any chance on "special offer-today only"? It may be a factory second as I'm fairly sure those red tops need recalling, some of the text isn't quite centered. Or have I been at the beer too?

  3. This is an awesome break-through! I'd be ready to set-up a paddle shaft tubing rig which would route the jet stream into the leading lower edge of the paddle to provide greater lift, thus increasing one's speed, but giving the sensation of paddling all the while. Paddling moves into the jet age at last and what a day to begin it on: April 1st!

  4. Sounds truely innovative, I never much enjoyed the repeditive nature of paddling anyway. Could it be turned at right angles to the boat to aid rolling?

  5. I suggest a can of beans, a very tight spray deck and a hole under the seat. Than you may even hoover over the overfalls...:-)

  6. That looks like a fantastic kayak innovation to me!

  7. I don't want to appear to pour cold water over your plan, but putting 2.7Ah, 1.2V batteries in series increases the voltage but leaves the capacity unchanged. I estimate that at 15 amps draw, the duration is less than 11 minutes if the batteries are in tip-top condition. Have you checked the endurance?

  8. Greetings Derek, it is good to hear from you.

    Quite a lot has happened since this was posted at the beginning of April!

    You are correct about the amp hour capacity being the same as the individual batteries' capacity when they are connected in series, we found out the hard way!

    The other problem was that the 2.4amp hour capacity is calculated at a low discharge rate. Using the pump motor at a high discharge rate you get less capacity, that's when we discovered Peukert's formula!

    We then replaced the NiMH batteries with a 28Amp hour deep draw lead acid battery. This worked well achieving its rated capacity and providing decent thrust for about 1hour 45minutes.

    However, all further development of the Kaya-Jet project has now stopped.

    We discovered that some clever folk in Carson City, Nevada had well and truly beaten us to it. We might as well all throw our paddles away!


  9. I really thought that this was April 1st wind-up. But it seems you were actually being straight-up.
    More fool me!

  10. Greetings Eurion, beleive it or not, a posting (a year before this one) about a CO2 inflatable "brace-a-float" seems to have inspired a commercial CO2 inflatable paddle float!

  11. While your efforts for making kayaking easier are admirable and despite some skepticism that your post was coincidentally dated around "early April" I love your humor.
    For a more serious "simple" install of said pump (minus the "special" effects) you can check http://gnarlydognews.blogspot.com/2009/04/shop-electric-bilge-pump-in-kayak.html

  12. Greetings Gnarlydog! I also use the Rule 500. In my Quest I have fitted it behind the seat but there was not room in my Nordkapp LV I have fitted it in front of the foot pegs and run the wires sealed to the hull with Sikaflex (not silicone!) back to the day hatch. I have found that SLA batteries sealed in a pelicase cause rapid corrosion of terminals so I just mount the battery in a little carrier made from closed cell foam. On one boat I use a toggle switch mounted on the bulkhead on the other an airswitch also mounted on the bulkhead. I used to have fuses but that just puts two more connections into the circuit and the fewer connections the more reliable! My oldest installation is still running faultlessly after 6 years!

  13. Wow I wish they had something like that down here in California! I mean there are a lot of people down here and it would most definitely be a memorable day in a kodak moment type of history!
    It really does look like a fun event and I wonder what other events like it they have planned! :)
    With events like this Im sure with its positivity it will only bring people to more of these all around the world!