Hi Trev,

I have used magnets to hold hatches in place on other models, but I wanted to use straps this time as that’s often how the hatch is held in place on a full sized kayak.

Hi Dave,

The brackets are black(ish) not chrome. I used ammonia fumes to take the brass shine off them.

One last thing to sort before gluing the deck and hull together are the fittings to hold the hatch in place.

Two elastic straps running across the top of the hatch will hold it down and I hope they will apply enough pressure to seal the neoprene gasket which will be in place between the hatch and the hull.

Brackets are needed to attach the straps to the hull. These were cut from a sheet of 0.8mm brass. A piece of masking tape was stuck on the brass sheet and the bracket outlines marked out on this. The holes were drilled and filed to shape before cutting the brackets from the sheet and bending them to shape.

Using black elastic for the straps, I didn't want the brackets to be bright, shiny brass so they were blackened by placing in a sealed container with a piece of kitchen roll dampened with ammonia. It only took an hour to take the shine off them 👍

Holes were drilled in the deck for the bracket fixing screws and M2 captive 'nuts' were made and attached to the underside of the deck. By having the nuts linked together in pairs, there is no chance of the nuts becoming loose and rotating when screwing the brackets in place. Based on experience, this is really important as the nuts will be difficult to access once the hull is assembled.

Finally, two channels were ground into the edge of the hatch opening on the deck to allow any water that does get splashed onto the hatch to drain away rather than collecting around the edge of the hatch opening.

Hi JB,

I can't think who it might have been who suggested your crew probably needed more firewood 🙄 but I didn't want them to get cold 🤣😂🤣

The more details you add, the better it gets 👍

Graham93

Lew,

I like the ‘note holder’. Great idea. I might have a go at making something similar but it will have to be fabricated as I don’t have a 3D printer.

I agree, the FlySky radios are great value. I have the FS-i6X and a pile of different FlySky receivers. Does everything I need from 2 channels on a sailboat to 10 channels on my Crash Tender (the note holder would be very useful for that to remind me which channel does what!)

Graham93

Starts today. Just look at the top of the HOME page

Graham93

Hi Trev,

Try looking for HF166F-12-1HDL2T-12VDC-magnetic-latching-relay. It is rated at 25A. There are several listed on eBay in the US.

Hi Trev,

The relay contacts are rated at 2A. There are two sets of contacts which I have wired in parallel to double the rating to 4A. The rating for relay contacts is the maximum switching current. When switching on a model with the controls set to idle, there is very little current being drawn. The current carrying capacity of the contacts (not switching) will be higher. I expect the current being drawn by the kayak will be less than 4A.

There are alternative latching relays available with much higher current ratings. I have one in my Crash Tender which is rated at 20A (if I remember correctly)

Hi Trev,

The relay I’ve used is type HFD2 sourced from eBay. There are plenty of sellers offering it. You have to match the coil voltage to your battery. I use a 5v relay for either 4 or 5 cell NiMh battery.

Hi JB,

Only forgotten it once 😥😫

Hi Trev,

Thanks, glad you like it. Thought it was worth explaining it in detail in case anyone else wants to try it.

You are right, I’m not using a LiPo battery. It’s a 5 cell NiMh.

I like to be able to turn the power on/off my models at the lakeside without having to remove hatches etc. I want a solution that is easy to operate and reliable, as there are so many other things to remember when preparing to launch. My two sailboats, the WeeNip and the Racing Sparrow have waterproof switches on the deck but this approach doesn't look right on a scale model. The power switches on my Crash Tender are fitted below the cabin hatch which slides over them to conceal them - if I remember 🤔. The Rowing boat and the Pilot Cutter have a pair of reed switches mounted below deck wired to a latching relay. A magnet is used to turn the power on and off by bringing it close to the appropriate switch above deck. One reed switch mounted on the port side turns the power on (P for Port and Power) and the other reed switch, mounted on the starboard side turns the power off (S for Starboard and Stop). This is the solution I'm going to use for the kayak.

The circuit diagram shows how it is all wired up. The latching relay has two coils. Each coil is connected to one of the reed switches. When a magnet is brought close to the 'ON' reed switch it activates one of the coils in the relay operating the contacts and turning the power on. The relay maintains this position even when the magnet is removed and the coil is powered off. Bringing the magnet close to the 'OFF' reed switch activates the other relay coil operating the contacts and turning the power off. Hence the relay only consumes power while changing state from on -> off or off -> on. It does not consume any power while the model is operating (or switched off).

A wiring harness was constructed on the bench having measured the required length of each of the connections. A charging socket is incorporated in the harness to allow the battery to be charged in situ. This socket will be accessible through the rear hatch.

The final three photos show the complete installation, prior to permanent fixing of the deck. It is possible to install and remove everything through the cockpit and the rear hatch.

Hi JB,

Looking better and better every day.

Nice to see you are using KIWI dubbin😉

Thanks Cash,

My Bill and Ben rowing boat doesn’t have a rudder and depends on control of the oars for steering. It is susceptible to cross winds, so I don’t sail it when the wind is up. I won’t have as much control over steering with the single kayak paddle compared with the two oars in the rowing boat hence the addition of the rudder which I expect will be essential

Hi Trev,

I don’t use AutoCAD. I scanned the rudder drawing from the book and then used photo editing software to scale it to the required size. Quicker and simpler than trying to redraw it.

Thanks Neil,

I’m planning to fit a small spring in each of the control lines to keep them tensioned. I’ve also made sure that the spacing of the control lines at the rudder attachment points is the same as at the servo arm which will help ensure the lines stay taught.

Having a rudder is optional on a full size kayak, but I think it is going to prove essential on the model if there is to be any chance of it travelling in a straight(ish) line.

Drawings of a typical rudder were copied from Nick Schade's book, scaled and glued to wooden blanks. The blade is cut from western red cedar, the other parts from birch ply. The parts were cut out, cleaned up and brass tubes fitted to each of the pivot holes to act as bearings. A brass fitting was made to mount the rudder on the stern of the kayak.

To route the control lines from the rudder to the below deck servo two aluminium tubes were bent and glued to the underside of the rear deck with their aft ends protruding through the deck. These ends were then trimmed flush with the deck. The inboard ends of the tubes were flared.

Two cords will run from either side of the rudder, through the tubes and then to either side of the servo arm. The cords will be tensioned with either elastic or springs. I prefer the idea of using springs as they won't perish over time.

Final assembly will not be done until the deck has been attached to the hull, but I needed to get the aluminium tubes in place before then.

Hi Doug,

Yes, I expect EzeKote would be a good alternative although I don’t have any experience with it. I’m just using up what I have in stock. I live not too far from Easy Composites and made a bulk purchase a couple of years ago.

Thanks Dave,

I’ve spent a lot of time thinking through different ways to fit everything in. It’s working out OK so far I think but the real test will be when I get it on the water 🤞

In addition to the rowing mechanism, I need to install the battery, receiver, paddling electronics and rudder servo.

For the battery, I decided to use 5 NiMh cells rated at 3300mAh. The decision was based on several factors.
1. Experience with the rowing boat where I've used 4 cells rated at 3700mAh. The rowing boat had 9 servos plus a 'transistor radio' and a smoke generator for Ben's pipe. The battery typically gives an hour or so rowing time, more if Ben doesn't light his pipe!🤣. The kayak has 3 servos plus the drive motor (a modified servo) so the selected battery should give plenty of duration.
2. The kayak needs some ballast and I prefer to use larger cells for this, rather than having to add dead weight.
3. The selected cells will fit under the paddler (just!)

The position of the battery under the paddler brings the centre of gravity of the kayak to a position just behind the location of the paddle which I think is where it should be. I may need to add some more ballast to balance everything up once the build is complete.

The receiver and paddle electronics are fitted into a plastic box (shown without it's lid) which sits just behind the paddler and battery.

The rudder servo is mounted behind the receiver. Both the receiver and the servo can be accessed through the rear hatch.

If you look carefully at the differences between photos 4 and 5 you will notice one of my 'mistakes'. Having glued the servo mount in the position shown in photo 4, I realized that I couldn't access the rear fixing screw through the hatch opening. The mount was carefully cut free and repositioned as shown in photo 5. Glad I spotted the issue at this stage rather than later.

Thanks Dave,

The fact you can’t see my mistakes shows that I’ve had a lot of practice hiding them 😂

Hi Trev,

I’m always making mistakes. I guess I’ve just got better at hiding them over the years. 😂

“Anyone who never made a mistake, never made anything”

Thanks Trev, JB,

I wanted as fine a cut as possible, hence the use of a scalpel. It still needs some cleaning up and sealing with epoxy.

As the cockpit opening is filled with the mechanism and the paddler there isn't much access available for anything else, so I decided to add a hatch behind the cockpit to give access to the rudder servo and the radio gear. It is not unusual to have a hatch in this location on full sized kayaks.

A paper template was drawn up on the computer, printed and taped to the deck. A scalpel was then used to cut around the hatch outline. It took a while, but eventually the hatch came away in one piece.

The template was rescaled on the computer to produce two more templates for a plywood rim to be fitted to the opening. The rims were cut from 1.5mm ply and glued into position.

The hatch will sit flush in the opening. It will eventually be fitted with a neoprene gasket and held in place with elastic straps. The double plywood rim creates space for the gasket while keeping the hatch cover flush with the deck.

I like the pencil marking jig Michael.👍 One to remember for future use.

Hi Stephen,

I certainly hope I don’t need to remove the mechanism to charge the battery. Getting everything in and connected is going to be a bit like keyhole surgery and I don’t want to do it more often than I have to.

The plan is to be able to charge the battery in situ so nothing needs to be dismantled.

Thanks Michael,

It’s the ‘unfortunate’ issues that I enjoy solving. It’s what makes scratch building such a challenge.

Before the hull and deck can be permanently joined together, the mountings for the paddling mechanism need to be installed in the hull. Checks also need to be made to make sure that, once the kayak is completed, it will be possible to install the mechanism through the cockpit opening.

The mechanism was developed and tested while mounted in a cardboard mock-up of the kayak. Now, cardboard supports were cut to position the mechanism in the hull in the correct longitudinal position, and at the right height. Once everything looked to be OK the cardboard supports were used as templates to cut the final shapes from 3mm ply. These were then tacked into position with superglue and the mechanism installed for a final check with the deck in place.

It soon became clear that it was not going to be possible to install the mechanism in one piece, through the cockpit opening. This was not entirely unexpected based on the experience with the cardboard mock-up. The mechanism baseplate was cut in two, separating the paddler from the remainder of the mechanism. The two pieces are held in position with M4 dome head screws which fasten into a tapped brass plate glued underneath the plywood support rail. There is only one linkage between the paddler and the mechanism which will be straightforward to attach through the cockpit opening.

“I’ll be back” 😂🤣

Thanks Gary, I did consider starting the blog with “And now for something completely different “😁

I like the challenge of trying something different. It provides lots of problems to solve and many hours exercising the gray matter while trying to work out the next step.