I have learnt the hard way that it is important to know the state of charge of the battery in a boat😊

When bionic Bill gets exhausted from lots of rowing (battery low) he starts to panic and look around for the shortest route to the shore! LOL😁

The little RX2A receiver I'm using doesn't support telemetry to feed the receiver battery voltage back to the transmitter, like the bigger FlySky receivers do. I added some software to the microprocessor that controls the rowing motion to monitor the battery level. It reads the battery voltage at intervals, and when the voltage drops below a threshold, the controller takes over control of Bill's head turn servo from the transmitter and gets him to turn left and right, looking for the shore. I hope this will be clear enough to see on the lake so that I can get the dinghy back to shore before Bill gives up completely.

Planking the bottom starts at the transom with a 35mm wide planks fitted either side of the keel at an angle. These were glued and nailed to the hog, transom, battens and chines. Subsequent planks are all 24mm wide and butt up against the previous ones. At the rear of the hull, the bottom planks overlay the side planking. Towards the front, the bottom planks butt up against the side plank. All the planking is mahogany and was cut 3mm thick from a wider board using the table saw. It was sanded smooth to remove the saw marks. Particular attention was paid to sanding the inner surface as it would not be possible to sand this from inside the completed hull.

Once all the planks were in place, the overhanging ends were trimmed flush with the side planking. Oak capping strips were added to the keel and stem to cover the bolt heads holding the structure together. Rather than trying to bend a thick section of oak, the curved section of the stem was capped with multiple thicknesses of oak veneer glued one at a time. These were then trimmed and sanded to shape.

I decided that now was a good time to build the stand for the dinghy, so that it would be ready for use when the hull is removed from the building jig.

I started with the hardboard template I had used to build the frames. This was cut out using the marked frame outlines as a guide. It was then tried on the upturned dinghy to check for the correct shape. The shape was then transferred onto some 9mm ply salvaged last year from a skip - I knew it would come in useful one day!

Once the hull shape was cut out of the two formers they were taped together and pilot holes drilled through both pieces. The two outer holes in each piece were drilled through 12mm, the other three holes were drilled halfway through using a flat bit.

Curves were added by drawing round a suitable sized paint tin and then cut out with the scroll saw. Not really necessary, but they do make the completed stand look more elegant, and they reduce the weight a little.

12mm dowel was cut to provide two long and three short lengths. The long lengths fit through the outer holes and are pinned through the edge of the ply, the shorter lengths are glued and screwed in the three central holes. A couple of coats of quick drying woodstain and a few pieces of pipe insulation and the stand is complete.

The last photo shows the reason for the longer dowels. My launch straps can be looped round the end of the dowels to make stand into a carrying frame.

WARNING: Based on a few of the comments made about my last Update, some members may find a few of the following photos upsetting..😂🤣

The mahogany used to plank the dinghy was sawn to 3mm thickness, but not planed. This meant that the hull needed a lot of sanding to produce a smooth finish ready for glassing.

Once smooth, I used slow setting epoxy resin and 25g/sq m. woven glasscloth to cover the dinghy. I'm a novice when it comes to glassing hulls, hence the use of slow setting resin. Three pieces of glasscloth were used, one either side of the keel to cover the length of the hull, and one for the transom. 24 hours was left between fitting each piece.

The chine rubbing strips, cut from mahogany were then glued and pinned in place, using 5 minute epoxy and the entire hull given a second coat of epoxy resin. This was left for 3 days to fully harden and then rubbed down with 600 grit wet & dry, used wet. Once smooth, which didn't take long when compared with the initial plank sanding, mahogany rails were fitted to the edge of the sheerplank and the transom. These were pinned and glued with epoxy. Having had to race against time when gluing the chine rails using 5 minute epoxy, I bought some regular epoxy to glue these rails. It has a 90 minute working time, and made for a much more relaxing fitting process.

Finally the rails were masked and the hull given two coats of grey etch primer using a rattle can (!!!). I think it will look great once it is finished with a white gloss topcoat (I know not everyone agrees with that ! 🙄)

The plan gives details of how to mark the waterline. Being concerned about the total weight I decided to pencil the waterline onto the primed hull so that I can check how it floats and what balast it might need (anyone come up with negative balast yet, in case I need to lighten it?)

Two horizontal battens were set up on the building jig at the correct height and a length of string was then used to draw the waterline position onto the hull.

Now the big reveal, time to remove the hull from the building jig. It came off relatively easily with just a couple of screws which were a bit difficult to reach. The inside looks OK, only 3 pins just sticking through out of the 1000 or so that hold all the planks on. Easily fixed with the Dremel and an abrasive wheel.

My priority was to check the weight. The full size plan states that the empty dinghy should weigh in at 400kg. I have built it to 1/6th scale so the target weight should be 400kg divided by 6 cubed or 216 which gives a target of 1.85kg. The hull isn't complete yet, but I needent have worried. It weighs just 1.55kg 😁.

Having removed the dinghy from the building jig, the first job was to cut and fit the oak forward deck beam and centre plank.

These were followed by mahogany inwales running the length of the boat pinned and glued along the top inside edge of the frames. Once the glue was dry, and the clamps removed the top edge of both the outwales and the inwales were planed level to each other to enable the cover planks to be fitted. To accommodate the curvature of the hull sides, the planking is fitted in three pieces on either side. Fitting these planks was quite a challenge. There wasn't a single straight edge to work to. It was also important to position the nails carefully as there will be visible on the completed dinghy (not paint here Doug!) In the end, I glued and clamped the planks in position one at a time. Once all three were in position on one side and the glue was set, the edges were trimmed flush to the inwale and outwale. Then it was possible to mark the position of the nails at a constant spacing from the edges of the planking. The nail holes were predrilled and the pins carefully hammered home.

The softwood frame braces were removed, opening up the inside of the dinghy and the oak rear deck beam was fitted. Finally the foredeck planking was fitted. The stem still needs to be trimmed back somewhat as it is too tall. The rear deck planking also needs to be fitted, but not before the servo mounting plate is designed, made and fitted.

Before planking the rear deck, the mounting arrangement for two servos needed to be made and fitted.

Each oar is powered by two servos. One to raise and lower the oar, the other to provide the fore and aft stroke movement. I want, as far as possible to hide all the mechanics from view, which in an open boat, is not so easy.

The stroke servos provide the power to move the dinghy, and hence need to be a reasonable size and torque. The ones I selected are TowerPro MG996R metal gear servos with a torque rating of 9.4kg cm on 4.8V. They are too big to fit under the floorboards in the dinghy so the only other option is to fit them under the rear deck.

A cardboard template was made from the hull and a piece of 3mm ply cut to shape with mounting holes for the two servos. This slides into place under the rear deck and is held in position by a single M3 socket head bolt which screws into a captive nut in a piece of oak glued to the keel. The rear edge of the mounting plate slides under retaining strips glued to the inside face of the transom. A thin piece of mahogany veneered ply is glued to the front of the servo mounting plate to conceal the servos. Two notches at the bottom of the mount give room for the pushrods to exit the mount and run along the floor of the dinghy to the oars. These pushrods will be concealed with removeable planked floorboards.

Once this assembly was complete, the rear deck was planked with mahogany to match the rest of the gunwale planking.

Thank you to everyone for the great comments received on the posts so far. I'm enjoying this build and hope you are enjoying the blog.

Time to move on to the rowlocks. On this build, the rowlocks will be rotated by the servos featured in the last post. Rotating them to-and-fro will move the oars fore and aft to produce the stroke.

Having studied pictures on the web, a full size sketch was put together and then scanned onto the PC and reduced to 1/6th scale. Construction started with two strips of brass of 4mm x 1.5mm section. These were annealed and bent round a steel bar to produce the basic shape. Two crescent shapes were also cut from 1.5mm brass strip and two bushes turned on the lathe. Each set of parts were assembled, wired together and silver soldered. The bush fits onto a 4mm stainless steel shaft (salvaged from a printer) and is held in place with a grubscrew. On each side of the dinghy, the rowlock shaft passes through a brass bush let into the gunwale and a second bush fitted in a beam between the side frames. A control horn will be fitted onto each shaft to connect to the corresponding servo.

The oars need to be attached to the rowlocks so that they move as the rowlocks rotate. The oars also need to be able to pivot up and down in the vertical direction to dip the oar blades in and out of the water. Rather than simply drill a pivot hole through the oar which would weaken it, I decided to make a collar to fit round the oar shaft.

The oars are rectangular section where they pass through the rowlock, so a rectangular collar was bent from 0.8mm brass strip by folding it round a suitable section of aluminium bar. The collar was wired closed and a short length of brass tube was also wired in place before the assembly was silver soldered together. The wires were then removed and the assembly cleaned up. A pivot pin passes through a hole in one leg of the rowlock, through the brass tube, and then into a threaded hole in the opposite leg of the rowlock.

The servos under the rear deck need to be connected to the rowlocks with long pushrods which run along the bottom of the dinghy and will eventually be concealed by the floorboards. To avoid the pushrod bending during bionic Bill's power stroke (!) I wanted to arrange that the servos will pull the pushrods for the power stroke. This needed a pivoting arm to reverse the direction of motion. The arm conveniently also raises the movement up from under the floor.

The sketch shows, in two dimensions, the arrangement of the pushrods and pivoting arm for the starboard side oar.

The two pivoting arms were cut from brass strip. The strip was first 'painted' with a black marker pen and then the outline of the arm scribed through the ink. The arms were cut out, cleaned up and brass pivots turned on the lathe to allow the arms to be attached to the side of the hull under where the thwart (seat) will eventually be fitted, thus concealing them from view.

Because of the way the servos are hidden under the rear deck, it isn't possible to connect the long pushrods from the servos to the pivoting arms in one piece. A joint for each pushrod was fabricated from brass to allow the two ends of the pushrod to be connected. Whilst this works OK, I'm concerned that it may come apart in use (Bionic Bill doesn't know his own strength!) so I plan to replace these with something that gives a more solid connection.

I use 2mm cycle spokes for most of my pushrods. These have a thread on one end, and are easy to cut to length and thread the other end with a 2mm die. My cycle spokes in stock were not long enough for this pushrod so I used 2mm piano wire instead. One word of warning, don't forget to temper piano wire before trying to thread it. Other wise you may end up having to buy a new die!

RobBob asked:

"I'm losing a sense of the scale of this boat now, perhaps we could see it alongside something we all recognise to help us 're-calibrate' our view "

So here are a few photos to help. Bionic Bill decided to carry out a progress inspection this morning and I got a photo so you can see the size compared with Bill (Action man). For those of you without an Action man in your toy cupboard 😁 there is also a photo of the dinghy alongside my 1/16th scale 34" Crash Tender. They are roughly the same length, although the perspective in the photo makes the dinghy look bigger than the Crash Tender.

Bionic Bill is 1/6th scale, approx. 12" tall. Hence the dinghy has been built to 1/6th scale from a plan for a full size dinghy of 17 ft (5.2M) length.