I posted a some pictures of my Crash Tender a few months ago and it was suggested that I should do a blog. So here we go.

This is my first blog, and my first boat. I am not going to provide a blow by blow account of the refit, as this would largely turn into a repeat of the excellent blogs by Rob (Robbob) and Mike (mturpin013). These two blogs have been a great inspiration and source of guidance for me over the past couple of months.

I built the boat in the early 1970s, but haven't had it on the water for nearly 45 years. Until recently, it had been collecting dust in my garage for all that time. The first task, having given it a good was to remove most of the dust, was to remove the ED Racer diesel engine, fuel tank, exhaust, etc and to fill in the exhaust hole in the transom. The diesel had always been a challenge to start, and to keep running. That, together with the unreliable, home built 27MHz radio gear is the reason the boat had been in dry dock for 45 years. A new brushless motor, water cooled ESC and 3S LiPo battery were installed in place of the diesel.

The propeller also needed replacing as the old one was too large. This identified the first problem. Times have changed since the 1970s and props now have metric threads, whereas my 1970s propshaft had a 4BA thread at both ends. A new 4mm silver steel shaft was fitted threaded M4 at each end. The new shaft diameter necessitated also replacing the plastic bushes in the shaft outer. Plastic bushes were probably not a good idea in any case. New phosphor bronze bushes were turned and fitted and it was then time to get it back on the water.

The first trial was very encouraging. The modern radio worked well, the boat was easy to start, quiet, and performed better than it ever had with the old gear. When I originally built it, I did not fit chine strakes. I cannot remember now why. It may be I didn't realise they should be fitted, or perhaps I felt they would spoil the smooth lines of the hull! Even without them it did manage to plane a little. Being fired up with enthusiasm after this first trial, I decided it was time to get back into the workshop, fit the missing strakes and start the refit proper.

Following the initial trial, I fitted chine strakes. These were steamed, bent to shape and left to dry. The original hull painting (humbrol enamel) was rubbed down and the new strakes fitted with epoxy and brass pins. I hope they will hold on the old paint surface. The gunwale strakes were also replaced as these had suffered from some damage over the years.

I also took the opportunity to replace the old cooling water outlet with something more to scale. Two exhaust ports were made using a couple of white metal portholes adapted with brass tubes which pass through the transom. The cooling water is fed out through both of these. I know this is not strictly accurate, as there should be a separate, smaller outlet for the engine cooling water, but I'm not looking to achieve 100% accuracy, just something that looks a lot more like scale than the original 45 year old model. I might revisit this at a later date.

The hull was painted using rattle cans, first a grey etch primer, then the colours followed by the decals and finally a clear lacquer coat. The hull was left to dry for two weeks and then it was back onto the water. As this is my only boat, I'm trying to carry out the refit in a way that allows me to get onto the water as often as I can.

The improvement in performance with the new chine strakes was remarkable. It now planes easily and turns quickly. With the diesel fitted it was reluctant to plane, and it could be difficult to turn which was due I think to the torque on the larger prop plus the missing strakes. What a difference hindsight (and this website!) makes. 😀 Another improvement was that the boat is now dry inside. It always used to fill the rear cockpit and the centre cabin with water but that is no longer the case. The two O-rings I added to the top and bottom of the rudder shaft may also have helped with this.

Returning from this outing I was unhappy to find that the foam protectors on the boat stand had marked the lacquer finish. Despite having left it for two weeks, it was still soft enough to be marked. Not sure if you can see the damage in the photo. Another detail I will have to revisit later.

I noticed that the motor was running a little warm so the opportunity was taken to replace the aluminium plate motor mount with one made from copper sheet with a copper tube silver soldered onto it. This has been plumbed into the ESC cooling water circuit and now keeps the motor reasonably cool.

The deck was then masked and painted with a textured finish followed by brush applied humbrol enamel. I found a tin of grey enamel in the garage, which must date from the original build, and it was still useable!

Having completed the basic hull repaint, it was time to get on to some of the more interesting details. Many of the deck fittings, ventilators, Samson post, etc were sourced from the shop on this website. These plastic fittings were primed with a grey etch primer and then top coated with Tamiya Gunmetal or Humbrol white enamel as appropriate.

Being the 1/16th scale Crash Tender, I don't have the benefit of having a set of white metal fittings. I wasn't able to find many off the shelf fittings in 1/16th scale so decided to scratch build them instead. It makes the job more interesting, if a bit fiddly, ....... and very time consuming!

The first task was to replace the fixed wheelhouse roof with a removeable one. This gives access to the interior of the wheelhouse for fitting lighting, new windows, and the searchlight servo. The window frames were cut from 1mm plasticard and painted silver.

The mast was built from brass, including making the pulleys. A 5mm white LED is fitted to the top, with a little white painted brass cap to make it look the part. Rigging is 1.5mm elastic cord. I think this is a little thick and 1mm might look better. I still have to source the ensign to fly from the mast. There is a pulley in place ready for it.

The port, starboard and wheelhouse roof navigation lights were all constructed using plasticard and fitted with 3mm LEDs. The aerial on the roof of the wheelhouse is made from brass based on the details given by Mike (mturpin013) in his blog.

The boathooks were also scratchbuilt from brass. I thought they would look better than the white metal ones available on eBay. For the "shepherd's crook" hook, the brass rod was first tapered by filing and sanding before being bent to the appropriate shape. The other hook was formed by silver soldering a brass cross piece onto a tapered shaft. Both hooks were formed on the end of a long length of brass rod to make it easier to handle them. Once complete, a short section of rod behind the hook was turned down to 1mm dia to form a spigot for mounting on the poles. The poles were carved from mahogany.

With all these details in place it is really beginning to look the part. Next up the rear deck.

The rear deck gives plenty of opportunity for adding some model detail. The original cockpit floor was plain painted grey with a 'power bulge' to cover the 1970's rudder servo. A new smaller servo and servo mount were installed to allow a flat floor to replace the original power bulge version. The new floor has been planked with lime strips grouted with 0.5mm black plasticard. The central hatch is easily removable to check that the servo compartment is dry. It is held in place with magnets.

The two foam tanks are made from 2mm ply with mahogany trim and pieces of a commercial grating fixed on top. The tanks are also held in place with magnets.

The ladders are 2mm mahogany with the runners glued and pinned to the sides with brass pins. The ladders are mounted using M1.6 threaded rod glued to the bottom of the ladders and passing through the cockpit floor. Foot pads had to be added to the bottom of the ladders to provide a sufficiently large fixing point for the threaded rod. Springs on the underside of the floor hold the ladders in place with the top of the ladders simply pressing against the bulkhead. This allows the cockpit floor to be removed with the ladders in one piece.

The towhook is made from plasticard, with a few details added with brass rod and M1.6 nuts. The towhook stays are also plasticard. They locate into brass bushes in the cockpit floor with the top end held with a locating pin and two small magnets.

The hose fittings were turned from brass using Robbob's drawings with the dimensions scaled down to 1/16th scale. The hoses are the normal coiled wire covered with black heatshrink. A brass hook at the rear of the cockpit holds the hoses in place. I was concerned that this was not sufficient in itself and do not want to loose these hoses in the lake, so black elastic cords were looped through the tops of the foam tanks. These loops pass round the hoses and hold them securely. The hose bulkhead fitting has a 5mm round magnet set into it's rear face which holds it in position against a similar magnet set into the bulkhead.

Using magnets for fixing the foam tanks, the towhook stays and the hose bulkhead fitting allows them all to be quickly removed thus allowing the cockpit floor to also be removed for access to the steering servo.

My thanks to Robbob and MTurpin103 for their excellent Crash Tender blogs. Much of this work on the rear deck has been based on their blogs.

When the boat was fitted with a diesel there was no deck between the forward cabin and the engine room. This was to allow room for the engine cylinder head. So the first task was to construct a planked deck to fill the space. The opportunity was also taken to add the cabin door detail, complete with dummy hinges and door knobs.

The davit was constructed from plasticard and painted gunmetal grey. Basic height and reach dimensions for this were taken from the plan. Details were added based on photos found on this site.

The scramble nets were made using black woven cord. This was laid out on a piece of scrap plywood using panel pins to space the cord into the desired net structure. The cord crossover joints were then glued with superglue. This didn't work well. The joints were not strong, some having to be re-glued. The dried glue caused a white stain on the cord. This was disguised with permanent black marker pen. A bigger issue was that the cord had absorbed the glue which wicked along the length from the joints making the net inflexible in parts. It would not roll up neatly and looked a mess. Fortunately I had enough cord left to make replacement nets. This time, each of the 100 crossover joints was sewn with black cotton thread. This took some time but the joints are now strong and the completed net is fully flexible.

This post brings us up to present day with the refit. There is still more to do including the fire monitors and spotlight. Just to show it does sail, I've included a photo of it out on the lake yesterday. It is only running at approx. 1/4 throttle which doesn't show how it planes. I haven't yet mastered driving it at full speed while simultaneously taking photos!

I want to have working fire monitors on the boat, so decided to make them in brass. I also want them to swivel. To give the right appearance, the water needs to pass through the vertical support column into the body of the monitor. I don't want a separate tube from the body of the monitor going through the cabin roof as it would not look accurate, and will likely restrict the rotation of the monitor.

The body of the monitor is made from a short length of 6mm brass tube with two turned end caps. The front cap, the nozzle, was turned and filed to a suitable shape on the lathe. The inside is drilled out as much as I dared to reduce the weight. The nozzle outlet was initially drilled 0.6mm dia. During initial trials with the pump connected this was opened up to 0.85mm dia. to give an increased water flow without having any significant effect on the throw of the jet.

The rear end cap is also drilled out internally to reduce the weight. Two 3mm holes are drilled at 45 degrees at the rear of the cap to attach the curved copper pipes which will carry water from the vertical support column. Bending the 3mm copper tube to shape was tricky, it is a tight bend but I managed it without it collapsing too much. The tubes will need a bit of cleaning up before painting.

The connection to the vertical column is formed as a T piece from two short pieced of brass tube. These were soldered together using silver solder for strength. Two small turned flanges connect the copper tubes to this T piece.

The handles were cut from brass sheet with a length of 1.5mm brass rod as the cross piece. All the parts were soft soldered together. The completed monitor body was connected to the pump and tried out. One of the soldered joints was leaking and had to be remade. Having drilled out the nozzle to 0.85mm dia. the resulting water jet looks effective with a throw of around 2-3 feet.

The fire monitor columns are constructed from two lengths of brass tube with various bits added, either for appearance, or for function. The short tube is 8mm o/d and has a brass collar added. This tube will eventually be glued into a hole in the cabin roof. I had to make these tubes a little longer than shown on the plan to ensure that the rotating monitor would not foul the lifebelts on the engine room roof.

The second, longer tube is 7mm o/d and forms the rotating column. It will slide into the shorter 8mm tube. It carries the water from below deck up to the monitor at the top of the tube. A brass bush is soldered into the top of the tube and the monitor body is soldered into that bush.

Part way down this tube, a brass collar is soldered to act as a bearing point against the top edge of the larger tube when everything is assembled. The bottom of the 7mm rotating tube was plugged with brass and then drilled and tapped with a female M5 thread.

The servo coupling is a brass boss with a disc of 0.5mm brass sheet soldered on. This was then turned to be circular before 4 brass pins were added to engage with the servo arm. The top of the boss is threaded with an M5 male thread to screw into the rotating column. A short length of 3mm copper tube is attached to the side of the boos to provide the water connection point. The centre of the M5 screw is drilled out 3mm to allow the water to pass into the rotating column.

Plasticard was used to add some details to the columns and then the monitor was rigged up on a mock up of the cabin roof and connected to a servo to test out the rotation. An electronic servo pulse stretcher was built to give 180 degrees of rotation for the monitor. I would have liked a little more, but the servo doesn't seem capable of accepting more than 0.5 - 2.5mS pulse width.

Finally everything was stripped down, de-greased and painted using rattle cans. First with grey etch primer and then with 'Toolbox red' as suggested by Robbob. I have just realised, while writing this that I should not have painted the lower sections of the rotating tubes as these need to slide into the shorter tubes. Ah well, it will be easy enough to scrape that bit of paint off!

(I'm sorry that the photos are not ordered in the correct sequence for the description. It doesn't seem to matter how I name the photos, or upload them, they just take on a random order of their own. Anyone know a solution to this?)

I have finally fitted the monitors onto the boat.

Servo mounts were made from aluminium angle. The position of the mounting hole in the forward cabin roof for the 8mm tube (see Part 2) was calculated based on the distance between the servo shaft and the mounting face of the aluminium servo mount plus a couple of mm. for adjustment. This dimension gave the distance of the hole from the bulkhead (CF3) on which the servo was to be mounted. The 8mm tube was glued into roof hole using epoxy. Once the epoxy was set the roof was put in position and a 7mm tube with wet paint on the end was slid down the 8mm mount to make contact with a temporary wooden block attached with double sided tape to the CF3 bulkhead below. The wet paint left a circular mark on the wooden block indicating where the servo should be positioned so that it's shaft would align with the fire monitor rotating column in the roof. The extra couple of mm. allowed for a spacer of suitable thickness to be made and fitted under the servo mount to achieve the correct alignment. The distance between the top of the 8mm tube and the wooden block was also measured allowing the required height of the servo mount to be calculated.

The same process was followed for the second fire monitor mounted on the engine room roof. In this case, the bulkhead (B4) had to be extended vertically to position the servo close enough to the roof. The servo mounts, and the new timber within the boat still need to be painted.

I had intended to use the crucifix servo arm to drive the rotating column, as can be seen in one of the photos. Whilst this worked OK, it was difficult to fit the roof and get the four pins at the bottom of the rotating column to engage in the holes in the servo arm. To make this easier the servo arms were adapted by adding a disc of 2mm plasticard with radial slots to engage with the drive pins. This has made fitting each roof easier.

The servo stretcher worked well, giving 180 degrees of rotation. However, once I saw it in operation, I decided it would be better to increase this to around 240 degrees as I had suspected. As stretching the drive pulse even further would not give more rotation I decided to try modifying the servos instead. This turned out to be easier than expected. Each servo was dismantled and two 3K resistors were added, one to each end of the feedback pot. The value was determined by trial and error. There was plenty of room to accomodate 1/8W resistors within the servo case. You can just see them in the photos. The servos now give the desired rotation without the need for the pulse stretchers.

I was hoping to include the plumbing details in this post, but I have had a few issues making this work acceptably, so I have had to go back to the drawing board and now have a few more bits and pieces to make. More to follow.....

The boat has a water cooled ESC and engine mount. These are fed from a scoop behind the prop. The water circulates through the ESC and engine mount and then out through the exhaust ports on the transom. The first attempt at plumbing in the monitors was to simply tap into this cooling circuit, add a filter and pump and feed the pumped water to the monitors. This didn't work too well.

With the pump running the monitors worked well, but water was sucked backwards out of the cooling circuit, drawing air in through the exhaust ports until the pump was sucking on air and the monitors stopped working. I had sort of expected this might occur so I had a non return valve available ready to fit in circuit just before the exhaust ports to prevent this reverse flow. I had hoped I would not need to fit it as I am concerned that the extra flow resistance it will cause will reduce the effectiveness of the cooling circuit. The second, unexpected problem with this simple approach was that, with the pump off, there was enough water pressure in the cooling circuit that the monitors continued to dribble water onto the cabin roof from where it drained into the hull. Adding the non return valve in the cooling circuit would only serve to make this problem worse owing to the increased pressure in the circuit. The last thing I want is for the boat to slowly fill with water, drenching all the electrics and gradually sinking so this dribble needs to be stopped.

After some thought, I decided that a diverter valve could be the solution. This would route the water either to the pump and monitors, or to the cooling circuit. I reasoned that I would not want the monitors working while the drive motor was running at high speed and so can afford to switch off the cooling circuit while the monitors are operating. I had an interesting few hours making a servo driven cam mechanism which at one end of it's travel would squash the silicone tube to the cooling circuit while allowing flow to the pump and monitors. At the other end it would cut off the water to the pump, and enable the cooling circuit. The servo would be driven by the same channel as the RCswitch that turns the pump on/off. Great idea, but it didn't work 🤔 The servo doesn't have enough power to turn the cam and squash the tubes and simply stalls. I need to try thinner tubes, or a more powerful servo, or something? Any helpful suggestions welcome...

Throughout the summer I have tried to keep the boat sailable for the local club sessions on a Wednesday afternoon. Not wanting to have to keep it in dry dock for an extended period while solving this issue I tried a different approach. I had available two solenoid valves so these were pressed into service as shown in the sketch. An RCswitch was constructed so that, with the pump on, valve A is closed and valve B is open. This routes the water flow to the pump and monitors. With the pump off, valve A is open and valve B is closed, routing the water to the cooling circuit. This works!

In the video (my first ever on YouTube) you can see how water flows from the exhaust ports when the monitors are off. I don't have a test tank at home so water is fed into the water scoop connection using a small aquarium pump. Now I just need jbkiwi to solve the smoker challenge so that I can add some smoke 😁

Following several weeks experimenting, and lots of discussion with jbkiwi, the exhaust smoker is now installed in the Crash Tender.

The heart of the device is an e-cig tank and coil. This was adapted with an acrylic end piece to allow connection of power and air. The 2ml capacity of the e-cig is a bit limiting so an expansion tank made from acrylic tube was added to give a fluid capacity of around 10ml. The smoker fluid is 75% vegetable glycerine.

The coil in the e-cig is designed to work from a single cell LiPo battery. A power converter drops the voltage from the boat's 2S battery down to 3.5V with a claimed efficiency of 98%. This voltage is adjustable which allows control of the amount of smoke produced.

Forced air is provided by a small diaphragm pump salvaged from a defunct blood pressure monitor. This pushes air through the e-cig. The resulting smoke is fed into the cooling water line between the ESC and the exhaust ports.

As the smoker is most effective simulating the engine 'ticking over' a water pump is used to create some water flow when the main propulsion motor isn't running. This adds more realism to the effect.

An electronic controller based on PIC microchips connects to the throttle channel and pulses the air pump at a rate determined by the throttle setting. It also runs the water pump at a slow speed, and controls the power to the smoke generator coil. If the throttle is held at maximum for a couple of seconds, the smoker pumps and coil are switched off to save on battery consumption. With the throttle at idle, a quick blip forward on the throttle will start the smoker again. Power consumption is around 0.7A on a 2S LiPo.

The two pumps are mounted below the footwell floor and the smoke generator is fixed to the bulkhead at the rear of the engine room.

My thanks go to jbkiwi for his encouragement and suggestions during the development of this feature.

Graham93