Further adventures in a motorised inflatable kayak / canoe

Following on from the last post regarding my exploits in fitting an electric outboard to an Adventure Plus kayak, I thought to add a few observations covering the kayak, motor mount and the cheaper, fixed speed, trolling motors.

I’ve now appended a chart at the end of this post showing all Bison motor Amp draw levels from 32 to 62lb thrust motors that Craig from Fishing Mad was kind enough to provide me with.

First off, a few links to save those who aren’t keen to wade through my rambling writings.

  • Another trolley with higher load capacity and more relevantly, which folds flat (I wish I’d not seen a month after buying mine) – Maplin Trolley
  • Spare parts for your Sevylor! – Meridian Zero It took me a while to find a supplier who could provide a correct mini Boston valve so a useful link and helpful supplier.
  • I mentioned battery boxes in the last posting, these are examples of the basic forms available –12v Shop
  • The more costly and capable versions that have charge indicators and cigar lighter sockets – Minn Kota Trolling Motor Power Center

Other battery boxes similar to the Minn Kota such as the Numax or Generic ones are readily available but all seem to be between £55 and £80 in the UK.

The Adventure Plus – One year on

As far as the kayak is concerned for myself and one passenger, I am still very pleased with this model, from a control, storage space, comfort and ease of deploying and packing perspective, although I would say with three on-board, it does feel less spacious. Having now seen a Colorado up close I think I made the right choice for my needs though (more space to relax and stash more gear).

The wind does have a real impact on the kayak and I enjoy the leisurely way this can allow me to paddle just on one side with the wind to counter the turning. This is fine when on a river (unless paddling against current/tide) but when moving into open water offshore, it is worth appreciating how far it can push you off course.

My only real complaint at all is regarding the inflation valves. The flower shaped fittings for the main side bladders that are meant to secure the cap to the valve when not closed and the valve to the outer shell of the hull, either bend outwards or fall off entirely and really just end up getting in the way. The floor bladder valve cap is not fixed to the main valve in any way whatsoever and if not screwed back in tightly (not what one wants to do when deflating) could easily be lost.

Well, I did lose mine and have now managed to purchase a spare after a good bit of searching. (A mini sevylor boston valve is what you want and through the link above was where I got mine) The point is that the official spare I purchased came with a full valve assembly including a base which is properly connected by a plastic strap to the cap. Now I’m not going to cut out and replace the whole valve just to keep the cap fixed on and will be more careful in future but this could have been avoided if the same, replacement valves were fitted at the factory in the first place. Fitting similarly integrated valves to the side bladders would remove the need to search around inside the outer shell for the valve when the ‘flower’ base has fallen off and separated the valve from the outer shell when deflated. The time spent pushing them back on to the valve base is also becoming a bit tedious and I’m wondering if epoxying them on is the answer. Probably not as that would bind the bladder to the outer skin and after annoying me on another trip out I’m just going to cut them off!

As it took a while to track down a spare cap that would fit the floor bladder valve, I attempted to improvise a cap. This is a handy bodge that I successfully spent a day out on the sea with. If you find yourself looking for something that could suffice in an emergency to give you an inflated and sealed floor bladder, the cork from a bottle of sherry or wine could be a perfect fit! Even to the degree that the cork screws into the valve smoothly and with no mess. (For the sake of accuracy, I had an M&S Jerez sweet sherry bottle handy so having a plastic top on the cork acted as a top to the bung) Of course you have to over-inflate a little and then be quick to seal the valve. Still, it took a full load for seven hours without noticeably losing any air.

Picture Postcard Arun

Picture Postcard Arun

The Motor Mount

I’ve taken a few more trips out since the first posting including a day out on the sea. Beyond the homemade nature of the overall rig making it feel precarious (or maybe because I know I made it), even when under a brief full power load from the trolling motor, nothing ever came free or looked to damage the straps or boat structure.

There has been no discernible deformation of the hull as a result of hanging the motor over the side although I haven’t used the motor more than four or five times.

I did note that the two bolts I used to fix the wooden bar to the metal bars had bent a small amount after several trips so I’ll probably try one size larger on the next two test rigs I’m playing with at the moment.

If being more critical, even though the battery and bungees hold the assembly in place, it is obviously not solidly fixed to the kayak and shifts slightly as thrust is applied which makes regular checks to the fixings a consideration. Having a firmer base to fix to, that distributes the thrust evenly to the kayak and perhaps reducing the vibration of the motor (only noticeable if holding to steer for long periods) are my main considerations for improvement.

One thought in terms of portability came up when I saw an Avon outboard motor trolley with wheels which I wondered if could be used to both mount a battery and the motor to. Again, as this would rely on the battery counterbalancing the motor it would still require some extra form of stabilisation by something such as bungees.

I’d also like to compare how a lower powered motor would work allied to a smaller, say 30Ah battery, although now I’ve been reading up a bit more, I’m going to have to investigate the specifications in a bit more detail as I’ll cover in the motor section now.

Lunch break at Regatta

Lunch break at Regatta

The Trolling Motor

Whilst I have no complaints with the motor and am very happy with the purchase, I grow ever more frustrated by the lack of information available from manufacturers/resellers of the cheaper, fixed speed motors, particularly with the two specifications that should be easily available. Weight of motor and amperage draw at each level of thrust. (Not, I should hasten to add, the most helpful Bison motor suppliers, Fishing Mad)

Without the electrical information, calculating even approximately how long your battery will last is going to be tricky and require testing by yourself.

Amusingly, on reading further, it appears that the reason for advertising trolling motors in pounds of thrust is due to the perception that people wouldn’t want to buy a 0.2HP motor so calling it a 50lb thrust motor is far better. Who for? It isn’t as if there is a likely racing application for them is there?

To satisfy my own interest, I am going try to find out a little more about the motor specifications and what to expect as a result. What I’m posting today is what I have found briefly browsing around online, next I’ll try manufacturers/resellers.

I’m only comparing fixed speed motors here. Variables and digitally controlled ones such as the Minn Kota or Motor Guide make, whilst more efficient and accurately controllable are an expensive option for my basic recreational application. Note: If misled by the terminology, even if the motor is advertised with 5 forward and 3 reverse speeds, that is still a ‘Fixed Speed’ motor. Variables controls are akin to a conventional outboard or motorbike throttle.

I’ll add some links here that are the only ones I’ve found so far with some sort of chart giving an ability to approximate from. I’m not going to test the draw at each speed like these so approximation and comparison is all I’m going to aim for until I can find more accurate figures.

Approximation chart for a rough guide – Trollingmotors.net
James P Smith’s blog post covering a 30lb motor at each forward speed – 30lb Motor Test

Just comparing the woefully inadequate manufacturers specifications that I can find, we see the following (different manufacturers of motor shown with differing max draw):

86lb max draw 48A
62lb max draw 58A
55lb max draw 55A
44lb max draw 48A
40lb max draw 35-40A
30Lb max draw 30A
18lb max draw 15A (7A min – see later note)

Considering the 86lb motor requires a 24v power supply, that leaves the others to compare specifically for my application.

James P Smith’s post about his specific and detailed tests give something that allows for a more accurate set of data for a 30lb thrust motor. This shows at level 1 on the control, the draw is not a fifth of the max. Now as James noted, the difference in thrust between level 4 and 5 on the motor is far greater than between level three and four.

In keeping with this train of thought, based on the draw at level four in James’ tests, level four equates to half power and as you can see, the load increase between level four and five seems to reinforce my perception of a greater jump in power between those levels during the mount tests. I’d agree with his assertion that the thrust isn’t doubling but considering the drag from my inflatable and the semi-fixed motor mount I am using, the strain on the mount was significantly greater jumping from 4-5 than 3-4. (I consider it was during that test I probably bent the bolts on the mount frame)

Taking James figures, noting also the stepping in speed differences for the first four gears, it would seem therefore that the levels one to five could equate roughly to the following drain on battery where 100% equates to forward control level 5:

Level/Motor Minn Kota Endura 30lb Bison 62lb Bison 32-55lb
Level 1 24% 15% 18%
Level 2 31% 20% 24%
Level 3 42% 33% 30%
Level 4 51% 42% 40%
Level 5 100% 100% 100%

Update for Bison motors: Based on the table at the end of this post, I’ve amended the above list into a table as there is a notable correlation between all but one Bison motor. With actual manufacturer published specs to base the draw on, estimations for this brand of motor can be a lot more accurate.

Taking these comparison to my 70Ah battery and the use I got out of it when running at between level 1-3 for several hours, I would say the figures are pretty accurate.

A final point here is that on the specs for the 18lb motor I noted a minimum draw listed as 7A which certainly isn’t 24% of 15A so that would blow my approximations out of the water and suggest the 30lb motor to be far more efficient than the 18lb (if the stepping between control levels follows the same pattern as above). So does level 1 on a 30lb motor provide the same thrust as level 1 on an 18lb or is the 30lb motor more efficient? According to Bison, their 32lb thrust motor draws 4.75 amps at level 1 so I suppose it just depends on the manufacturer thus it is advisable to check.

Offshore by Hove Lagoon

Offshore by Hove Lagoon

Out and About

Well, whilst I haven’t spent as much time on the water as I’d have liked, the variety of locations and conditions we’ve been to so far have proved the versatility of the kayak and the immense fun to be had with it.

From trolling around Henley Regatta all day with my youngest to surfing in the waves of the lovely Trecco Bay in Wales the kayak feels really safe, especially with children on board, due to the high sides and stability.

At Trecco, after riding in on a few waves with three on board and due to some overenthusiastic paddling, we took a full side-on hit from a wave breaking on the shore which purely filled the boat without even capsizing, leaving us sitting laughing in a paddling pool on the shore! (I felt sure the bladders would burst when trying to empty the water but rolling from the sides got it all out after a few hard pushes)

The day out just offshore from Shoreham Harbour gave me a chance to see how the kayak worked as a sunbathing/swimming platform and if I felt secure enough to be out there with the motor rig unbalancing everything.

Most recently I tried a run up the Adur, again from Shoreham Harbour without the motor traveling up and back with the tide. Taking a very leisurely paddle up about half-way to Steyning took about three hours and I returned in two only paddling marginally faster trying out my laid flat style.

Well, that’s about all for now. The mount frame is in pieces and I’m trying to get some salt from the bolts to test out the next design. More, sometime..

As noted above, the following table shows the amp draw at each level of the Bison motor range. (I’ve not included the 86lb specs as that is a 24v motor and out of my scope)

Model / Throttle Pos. R3 R2 R1 F1 F2 F3 F4 F5
32lb 26 7.92 4.75 4.75 6.25 7.92 10.33 26
36lb 29 8.83 5.33 5.33 7.00 8.83 11.50 29
40lb 34 10.33 6.25 6.25 8.25 10.33 13.50 34
46lb 40 12.17 7.33 7.33 9.67 12.17 15.83 40
55lb 52 15.83 9.50 9.50 12.50 15.83 20.50 52
62lb 58 19.08 8.75 8.75 11.83 19.08 24.92 58
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