Hi JB,

Re: How about using something like these remote switches which I use on my HSL and ST to turn pumps and lights etc on/off.

Yes, that would work but I should have explained the issue clearer. With the pump plumbed on the feed from the pickup as you suggested, the pump will need to run both when the monitors are in use and for cooling the motor/ESC. With they way I have it plumbed currently, the pump doesn’t need to run to cool the motor/ESC.

If I do find I need to change it round, I’ll probably put a remote switch together to connect to the throttle channel and the solenoid (fire monitor) channel. The switch could then turn the pump on when needed for either function.

Graham93

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Doug,

I also find I have lots of very low resistor values that I’m unlikely to ever use. At least with those I can put them in series to make a useful value, and the calculation is much easier🤣
Graham93

Hi Peter,

No, there isn’t any back pressure on the valves. They seem to work OK at around 7.5v but I don’t have much run time with them yet to know if they will be reliable at this voltage.

Graham93

Doug,

Yes, a 555 based solution would do the trick. I’ll probably start with that on the bench for experiments, but move over to a PIC implementation later as I would want the pulsing rate to track the engine speed and would find that easier to implement with a PIC. Would also use less components and be smaller.

Graham93

JB,

Yes, I could change the plumbing round as you suggest. The downside is the pump would have to run continuously. The present arrangement only needs the pump running when the monitors are in use. However, when it comes to smoking exhaust, maybe I’ll need it plumbed that way

Doug,

The solenoid valves were sourced from a box in my workshop, which is now empty, so there is no point providing a weblink to that 🤣. However as the box is empty, I did order two more earlier today from eBay for smoker experiments. These are identical to the ones I used for the monitors and look very similar to the ones JB has found.

They are rated 12v but seem to work quite happily on a 2S LiPo. Draw less current that way which will help with battery duration. Whilst it works well in practice, I’m not too happy with the dual solenoid solution from a current draw point of view. One solenoid is always activated, so there is a constant current drain. The servo driven cam solution would have had minimal current drain, shame it didn’t work 🤔

Graham93

https://www.ebay.co.uk/itm/DC-12V-Mini-Electric-Solenoid-Valve-Normally-Open-Fluid-Air-Gas-Water-Valve-J7/264467726756?_trkparms=ispr%3D1&hash=item3d938141a4:g:JQgAAOSwlSBa9lZG&enc=AQAEAAACQBPxNw%2BVj6nta7CKEs3N0qX63lU0L3MVMHgwqRWDFa5fU6YnPNp2DuVMJnQhqelceMGj44nT1LtBcj2g%2Bl6DuOnQVwjqKrZ%2Ffd2irZNTXetznfw0kYraVv5TU2SG%2FNjrFlPNvngZvZ2h9sIaIyOOmEe%2FljbDFqXjgwTZ%2FDqRewmFWSQ7JFvFl1yArlQ2ajfAAyJ1BeobPxlp0eYQhAnM0qgbfi5juPq7EmYV5LUjWQWXbdSSkZcdzt0HapF226azpi6blJikYx14BEloDTRKAAE%2F351GX7BdUUaP3Lcey

🔗

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Hi Martin,

The cooling isn’t pumped. There is enough flow round the circuit just from the motion of the boat and the pressure from the prop. At least there was until I fitted the valve. Haven’t had chance to test it on the lake since I fitted that. If necessary, I could change the plumbing so that the pump is in the direct line from the water pickup and runs all the time. That would increase flow through the cooling circuit, and the valves could still be used to switch the flow between cooling and monitors.

Graham93

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Hi jb,

Here is my latest attempt. Using part of an e-cig coupled to a 12v pump via a solenoid valve. Switching the valve on/off quickly gives a pulsing effect. Currently doing that manually, but a bit of electronics would automate it. Could envisage pulsing the water in a similar way.

Graham93

Smoke generator

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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 😁

Fire monitors

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Thanks Doug, I got a bit carried away with the technical bit and missed Michael's request for resistor colour codes. My only excuse is it was late last night 😉

3k isn't standard in the common E12 series of resistor values, but it is standard in the E24 series. I recently bought a pack of 1000 mixed E24 values in 1/8W size quite cheaply from Ebay as I needed physically smaller resistors for model use. They are so small it is difficult to see the colour code printed on them, but fortunately the carrier strips are printed with the values. A good ohm meter also helps.😁

Graham93

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Mike,

The servos I have used are TowerPro SG90s, but I expect the modification would work on any analogue servo, although the resistor values may need to change.

Servos have a feedback potentiometer attached to the servo output shaft. This pot feeds a variable voltage into the servo electronics based on the output shaft position. For the SG90 servo this voltage is 1.0V when the control stick is at its minimum setting (= 1mSec pulse width) and 2.35V when the control stick is at its maximum setting (= 2.0mSec pulse width). The servo (and feedback pot) rotate about 100 degrees between these two settings.

Before modification the pot, which is capable of around 250 degrees rotation, has a total voltage of 3.3v across the ends of the track. Thus 250 degrees of rotation would equate to 3.3V and hence 100 degrees equates to the 1.35V range given above (2.35V-1V). By adding resistors to each end of the potentiometer track, we can reduce the voltage across the track such that the 250 degrees of available rotation equates to a voltage change of only 1.35V. This way the servo has to rotate much further to provide the electronics with the 1V to 2.35V input it is expecting.

Adding the resistors involved dismantling the servo, cutting the outer two leads to the feedback pot and fitting the 3K resistors between the cut ends. Hope the attached sketches, together with the photos previously posted help.

Graham93

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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.....

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Mike,

Looking good. I agree, bending the tubes is probably the most difficult part. I like your elegant solution with the solder filled tube. Much better than my brute force attempt. I used annealed copper tube and an external bending spring, but if I put enough of a bend in the tube, I couldn’t remove the spring! I’ll remember the solder trick for any future attempts.
Graham93

Mike,

No I haven’t. I don’t have any experience with sail winches. It looks like they will certainly rotate more than 180 degrees. I think the one you have found will do 4 x 360 degrees. You would need to be careful not to tie everything in knots with that.

Found the attached video which shows the rotation. It looks like the servo takes a little while to complete its rotation which could make it a rotating monitor difficult to control.

Regards
Graham

The HS-785HB Sail Winch Multi-Rotation Servo Explained

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Martin,

It is a clever solution. I feel I should just point out, just to avoid any confusion, that I didn’t build it. It’s simply a video I found on YouTube.

Regards
Graham

jacko,

Very difficult to synchronise two continuous rotating servos. They will almost certainly run at slightly different speeds due to friction, manufacturing differences etc. Even if they run at the same speed, tiny changes in loading on each oar for example will change their speed and knock them out of step. There are lots of videos on YouTube showing rowing mechanisms. With a continual rotating servo, the solution seems to be to use one, and then have a separate servo to adjust the drive to each oar, using a clutch as in the attached YouTube example. Trying to sync two continual rotating servos is really tricky. It would need sensors on each servo to measure their relative positions, and then some control unit using these sensors to keep the servos in step.

Other solutions use normal servos for each oar, and use some control electronics to drive them both in sync, or out of sync when turning. This is the approach I plan to use.

Regards
Graham

RC ROWBOAT MECHA

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Thanks JB,

There is plenty of room, although I am gradually filling it up. I like the elastic suggestion and plan to fit an elbow to the copper tube inlet to turn the tube down. I just need to make sure it clears the servo while rotating.

Regards
Graham

Thanks Rob,

Yes, I did try them before I painted them and was pleased with the water throw. If I was to make them again, I think I would arrange for the nozzle to screw on to the front of the monitor to allow it to be dismantled and flushed out. I’m going to fit a filter in the pipework but I suspect I’m going to have problems with blockages on the lake.

Good point about securing the pipework. Would hate to watch the boat slowly sinking in the middle of the lake.

Regards
Graham

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Thanks Peter,

Component Shop have some great products for this sort of thing, and that device would give a good range of control. Being a retired electronics engineer I like to keep my hand in and make whatever I can in terms of controls. Makes it all a bit more interesting.
Regards
Graham

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Mike,

Yes, the silicone tube will attach to the copper pipe and hence will have to swivel. I am concerned about this getting into a tangle but I have a few ideas. I wasn't looking for as much as 270 degrees, but a bit more than 180 as shown in the picture. I think I'll stick with 180 for now and get it all installed and working. Can always upgrade it later if I'm bored!

Doug,

The pulse stretcher isn't the problem in this case. There aren't any mechanical end stops on the servo either. If you give it pulse widths over 2.5mS it will do 360 degree and more in uncontrolled rotations without any damage. No stalled motor or stripped gears.
It seems to be the electronics in the servo that will only sensibly interpret pulse widths between 0.5 and 2.5mS. This range equates to 180 degree rotation. So if I want to get more, I either have to change the servo, or adopt one of the suggestions from you or Martin.

The pulse stretcher is scratch built. A few lines of assembler code burnt into a baseline PIC10. Very basic, it takes in 1.0 - > 2mS pulse width and outputs 0.5 -> 2.5mS. I even dispensed with a circuit board and simply soldered the wires onto the chip to keep it small. Need to wrap this in heatshrink before it goes in the boat.

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?)

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Peter,

The mini lathe has made all the difference to being able to make things like this. I couldn’t attempt it without it. I haven’t had it long, and I’m still a bit of a novice with it. What you can’t see in the blog is how much time it has taken to make these bits, and how many spoiled attempts there have been.

I think the rotating support columns, together with the water connection will be quite a challenge.

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Rob,

Good to meet you on Saturday and to see your boat for real rather than just looking at the photos. We enjoyed the event at St Albans. It was great to see so many activities for the youngsters to have a go. Nice video of the boat. I especially like the on-board clips. I picked up some brass rounds at the show that will be used for parts for the fire monitor support columns.

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.

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Thanks Martin and thanks to everyone else for the positive feedback and encouragement.

Yes, I am pleased with the results so far. It looks a lot better, and sails a lot better than it did before the refit. Now it’s time to get on to the working monitors and searchlight.

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!

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Peter,

Thanks. The paint is brush applied Tamiya acrylic in Gunmetal Grey X10 applied over grey etch primer from a rattle can. I’m pleased with the effect. It is thin, goes on easily without obscuring detail and dries quickly. I have found that it needs frequent stirring otherwise you end up with a plain dark grey finish.

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Mike,

This has taken most of my spare time over the past three months, indeed I have really spent more time on it than I should have, with many domestic jobs not getting done. And I haven’t had the distraction of having to build a boat for my grandson like you have. He wants to sail this one, which I’m not sure is a good idea 😉

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Thanks Martin. It has been a challenge, but it has kept me out of mischief for the past few months. Not finished yet, but I’m already planning the next project. Trying to be good though and making sure I finish this job before I start the next one...

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.

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