It's been a while since my last update!

Up to this point, the kayak mechanism has been largely mechanical as shown in the first two photos. The trouble I find with such mechanical solutions is that to make adjustments to the action requires making new parts. This is often a trial and error process which takes a lot of time and leads to much frustration. I much prefer to use multiple servos with software in a microchip to coordinate the servo movements to achieve the desired effect. That way, changes to the action can be made quickly and easily by adjusting the software. Quicker changes and less frustration, at least for me.

So, I've put together a new, servo based mechanism for the kayak as shown in photos 3 and 4. This uses 6 servos to produce the paddling motion.

A recent video from RCsailing includes clips of Katie paddling the kayak with this improved mechanism

https://youtu.be/c64eW8HekvU?si=LNfWJCctswAGhYVy

Having gained some experience with the test paddle, and having worked out the feathering angle needed between the two blades by trial and error, its time to make a fancy replacement.

Some cedar and pine were cut into strips and glued to produce a striped blank. This was then cleaned up and cut using a bandsaw to produce four blanks taking care to ensure that the stripe pattern lined up. A shaped sanding block was used to sand a curve into the blades which were then glued to a redwood shaft and cut to shape. Lots more sanding was needed to thin the blades and blend the joint between the blades and the shaft. Once the sanding was finished the blades were strengthened with a layer of lightweight glasscloth and epoxy on both sides, followed by 3 coats of yacht varnish.

The new paddle is slightly longer than the original, and the blades are also a little bigger.

A short video, courtesy of 'philcaretaker':

The original rudder was made to "scale size" (1/6th). It worked, but the turning circle wasn't great. I attached a piece of plastic to the rudder with double sided tape to try the effect of a bigger rudder, and as expected, the maneuverability of the kayak was much improved, even if the appearance wasn't 😆.

A replacement rudder made from western red cedar looks a lot better. The shape ensures that the increase in size is not visible when the kayak is out on the water.

I can't believe it's been two months since my last update to this blog. I haven't been idle though and have continued to tweak the paddling mechanism and the control electronics.

The latest tweak was to increase the size of the rudder as I had foolishly made it the correct 'scale' size, forgetting that water doesn't scale and a model rudder needs to be larger than scale. Anyway, I glued a bit of clear plastic on to the wooden rudder with double sided tape as a trial and it has greatly improved the turning circle. Now I just need to make a wooden replacement to replace the plastic and sticky tape version. I'm also part way through making a 'fancy' paddle to replace the test paddle, now that I have the blade feathering angle worked out.

Here's a short video clip of the latest outing yesterday:

I wanted to keep the paddle shaft in one piece for strength, but while undergoing 'sea trials' it has become clear that a means of adjusting the feather angle between the two paddle blades is essential. Accordingly, a brass coupling was made on the lathe. It comprises two pieces which screw together with a knurled locking nut. The paddle shaft was cut into two halves and epoxied into each end of the coupling. The two halves can now be adjusted to set the blade feather and locked in position.

The other problem during the first outing was Katie letting go of the paddle. Whilst this gave an impressive demonstration of one, or even no, handed paddling, it wasn't very realistic 😂🤣. Loops of elastic cord were added to keep her hands on the paddle.

The paddling action is produced with a combination of mechanics and software control. A few changes were made to the software to improve the ability to steer. There is still more to be done to improve this. If you watch carefully at 0:35 seconds in the video, you can see the rudder compensating for the paddle stroke to help keep Katie moving in a straight line.

Sorry the video is a bit jerky in parts with my camera mounted on the transmitter. I expect Phil may have something better to show, once he has had time to edit it.

Before the maiden (!) voyage, a quick head 'transplant' !! I'd like to introduce 'Katie the Kayaker' 😂🤣

It was with some trepidation that Katie was carefully launched onto the Buxton lake. An ideal day last weekend with very little wind. I knew she would float, but would she move, and be controllable? Well the answer is yes - sort of 🤔

Thanks to Philcaretaker for the video clip.

She managed to paddle out, turn and paddle back, which was a great start. At least she didn't need rescuing. Shame she wouldn't keep hold of the paddle!

The paddle blades are not feathered at the right angle. The starboard blade is at the wrong angle and is hitting the water causing the kayak to rock excessively from side to side.

Once back on dry land, the kayak was checked inside for water. There was just a drop but nothing to worry about, which was also a relief.

So, overall it was reasonably successful, but several teething problems to be resolved before the next outing.👍

With everything finished, it's just a matter of installing it all into the hull.😉

A temporary paddle was made for initial trials on the water. There are many variables to be settled for the paddle in terms of paddle length, blade size and the feathering angle between the blades. Once these are established, then a 'fancy' paddle will be made.

Pictures 3 & 4 are from an earlier post and show everything in situ, before the deck was added to the hull.

With the deck in place, it is difficult to see very much. It is also difficult to install all the bits, but with a little patience, it all fits.

Manufacture of a spray deck from rip stop nylon was subcontracted to my wife, who has much more patience than I do.😇 An elastic cord run inside a seam around the edge grips over the cockpit rim.

With everything in place, a short video to show the action:

The rudder mounting pivot was attached to the stern of the kayak using brass pins and epoxy. The rudder itself was then fitted using a length of M2 threaded rod as a pivot. As with a full sized kayak, a length of bungee cord holds the blade vertical but allows the rudder blade to tilt backwards if it comes into contact with something underwater.

The rudder is linked to the servo using two cords which run from the servo, under the deck through the previously installed aluminium tubes and then exit through the deck adjacent to the rudder. The small springs provide some tension in the cords to remove any slack and backlash.

An additional line runs from just behind the cockpit, through small guides glued to the deck, and attaches to the top of the rudder blade. On a full sized craft, this allows the kayaker to raise the rudder blade to avoid obstructions.

The short video shows the rudder in operation:

The hatch fittings that were made a few weeks ago screw into place either side of the hatch opening. Black 'knicker elastic' is threaded through the fittings to hold the hatch in place.

A neoprene gasket was made and glued to the underside of the hatch lid, together with a wire loop. A cord from this loop is attached inside the hull to ensure that the lid is never lost. Making a replacement to match the existing planking would be very difficult.

I was fortunate to find some miniature plastic buckle clips to fasten the elastic over the completed hatch.

I'm concerned about the risk of the kayak sinking. It will be very low on the water and being long and narrow, it likely won't have a lot of lateral stability. Also, because of the mechanical connections to the paddle, even with a spray deck in place, it won't be possible to fully seal the cockpit against water ingress.

To reduce the risk, I decided to fill the empty space in the hull with polystyrene beads. The red lines on the first picture show the areas to be filled. I hope this will ensure that even with a capsize, the hull will remain afloat and not disappear to the bottom of the lake.

The hull was hung on a cord from the workshop roof and polystyrene beads were poured in to almost fill the spare space. To hold the beads in place, a handful of beads were coated with (waterproof) PVA and added to the top of the fill. Once dry, these formed a plug to hold the loose polystyrene in place. It will be a simple matter to dig out the plug and pour out the loose fill if it ever proves necessary.

The process was repeated to fill the other end of the hull.

Once everything was dry, it was time for a first float test in the domestic test tank. The mechanism, the RC gear, battery and the paddler were installed. It was a great relief to find that the kayak floated level, is reasonably stable and is self righting when tipped from side to side.

All up weight is just 1kg.