As promised (or threatened?😁) stage two of the hull work and thoughts on motorisation. The hull was sprayed with two coats of grey primer/filler. Pic1. As usual this showed up the remaining imperfections (pics 2 & 3), but I'm not going to worry about them until I've got prop shaft tube and rudder stock sorted out and permanently fitted 😉 After my attempts to make and thread a 3mm prop shaft went awry Martin (Westway the Mechanicals Master👍) stepped in and made me a decent one complete with a bushed stuffing tube 👍 Vielen Dank Meister😊 I did however manage to make a 4mm to 3mm reducer so that I could fit a Rabeosch 35mm prop as seen in pics 2 & 3. The tube and shaft from Martin, arrived Saturday an' he only made it on Monday😊, have been dry fitted so that I can start setting up the gears, necessary to bring the drive down to the prop shaft fitted very low down in the hull, and motor mount. Pic 4. Motorisation: (Remember folks - this kit was designed and built as a static model!) I want to use the old 1950s Taycol Target motor which my Dad originally fitted in the Sea Scout which I have renovated and upgraded to brushless. See Build blog 'Sea Scout - Jessica' Many of you will know that the Taycol motors were field coil motors, meaning that they have no permanent magnet around the rotor coil, and thus reversing the battery connections to the brushes had no effect on the direction of rotation, as this simply reversed the magnetic fields of both stator and rotor coils🤔 To counteract this so that the motor could be used in both forward and reverse with a conventional brushed ESC I modified the motor slightly (separated the two coils) and built a simple converter board to connect it to the ESC. Again see the Sea Scout blog for the details of the conversion. Basically; once the field coil and brush-gear (rotor coil) have been separated a simple diode bridge can be used to apply the output of the ESC to the motor. This enables the reversal of EITHER field OR rotor coil polarity, depending on how you connect the converter to the motor. Thus reversing the direction of rotation of the motor. Beneficial side effect is that the diodes also suppress the commutator sparking😊 In my case, with the Taycol Target, I also cleaned, flattened and polished the commutator. Thus significantly reducing the potential for spark generation in the first place! A peculiarity of the Taycol motors is that they all use metal brushes, pressed phosphor bronze strip, so they need oiling! DO NOT oil conventional brushed motors with carbon brushes unless the brushes are exchangeable or you want to have to buy a new motor!!!!! Pics 5 & 6 show the proposed position of the Taycol in Gina 2 and pic 7 the prototype converter board I knocked up to test the motor, together with a Graupner Navy V30R Marine Brushed ESC. Details and results in the Sea Scout blog, including video of the sparks and oscilloscope pics of the drive waveforms before and after conversion! The latter showing the spark suppression effect of the converter😊 Some samples attached - last 3 pics. Pic 8 pic shows a more compact version of the converter, one of a few types I'm doing for Martin's various Taycols as a trade for the prop shaft he made for me and some useful material he sent. Thanks mate👍 Next steps will be 1) mounting the gears correctly on the shafts, requiring the manufacture of a 3/32" to 4mm adaptor and a 1/8" to 4mm adaptor, and keying them to the shafts - Hooray for mini milling machines 😉 2) manufacturing bushed end plates to hold the gears in place, 3) fitting the motor mounting platform. I'll probably borrow from my experiences of real shipbuilding and do this as a suspended 'false floor', i.e. mounted on stiff springs to enable adjustments to optimise the gearing mesh! On real naval ships this is done to improve shock resistance and to minimise engine noise / vibration conduction to the hull, thus significantly reducing the acoustic signature of the ship. Not that I'm tooo worried about being torpedoed 😁 Worth a try😉 Pic 9 shows the cleaned up and renovated Taycol Target motor. Pic 10 shows the drive waveform complete with sparks before modification.🤔 Pic 11 the cleaned 'forward' waveform with the converter board. Pic 12 the cleaned 'reverse' waveform, no suppression capacitors needed 😉 More soon folks, Cheers, Doug 😎 PS Along the way a new keel was fitted as can be seen in pics 1 to 3. The original builder had 'buried' the keel in the hull planking! 😲
Hi Well after some time thinking about making some new rudder horns (thinking = four beers) I have made them out of an old three pin plug I used the small fuse clip that the wire goes into, I have also used a mini servo and all seem's to work O.K, new motor mount made so that the motor's now line up, I also had to make a new rear deck and bulk head I will in time plank the rear deck, I have also started on making new rear deck housing. Fred
Hi Bryan, If you want to do the SOE version she was most likely painted all matt black! The colour of skulduggery 😉 What ever you do, despite your good intentions to retain the 'old patina', judging by the photos you are in for a complete strip back and redo. Just as I have discovered with the PTB I bought. Thought it would just be a 'cosmetic job', flatten back and respray with Pacific green camouflage. Ho ho ho! Pics show what she currently looks like after cleaning off layers of enamel, and discovering that the prop shafts and rudders were misaligned and the chine strakes glued to the paint. 😡 Never mind an engine room fire when I tried to test the 'as bought' motor installation. 😭 Since those photos I have fitted new a new chine strake and started reinforcing the thin hull with glass fibre tissue. Next issue; set prop tubes properly and make an alu bracket to mount both the motors. Then set the rudder stocks correctly. Last thing I want is to dampen your enthusiasm, but that hull looks like it needs oodles of TLC. 🤔 Be aware of what's ahead of you and plan accordingly👍 Deck looks pretty neat, if unusual for a WW2 in service boat! As far as I can tell from the photos it's not just the cabin roof which is warped 😲 cabin and window frames will also need some attention by the looks of it. Before you run that motor I would strip it, clean all parts and check brushes and commutator for wear. See my Sea Scout blog 'Taycol Target motor' for a 'How to'. Should run well with a 3S LiPo, 11.1V. These boats weren't the fastest, 28 - 30 knots I believe. Which is why ST360 was reduced to more mundane duties after try outs by SOE. Don't forget some spark suppression!! Good luck, whatever you decide to do have fun doing it, Cheers Doug 😎
Skinned the frames added deck and splash rail also started on cabin and superstructure, added rudder and installed twin brushed Graupner 600 motors via Graupner style direct couplings. Motor mounting system through a bulkhead gives extra support to motors which mount on to end of the shafts. currently adding a rudder servo mount, as rudder is a close copy of the real boat's and still functional.
Hi Rowen, I have had water cooling on all my patrol boats running at 12Volts, whether brushed or now brushless. For the brushed motors I have used aluminium tube coils with water pickups between the propellers and rudders. I did try water jackets a couple of times but found too much friction loss and therefore lack of flow. For the newer brushless outrunners I use a brass tube soldered to a brass plate across the front of the motor fitted between it and motor mounting bracket. I agree with Doug with regards to the disconnection of the red wires on the ESC's. This is now common practice, especially if you have an external receiver battery.
Once the rudder, propeller and shafts were installed, the position of the motors could be established. A light aluminium bracket to hold all three was fabricated and bonded to the hull. Due to the high speed capability of the brushless motors, particular attention was paid to alignment. Also kept to the shortest prop. shafts that could be fitted to avoid whipping. Although the motor type might change, whatever is best will require a sound electrical installation as the current requirements for each brushless motor could reach 50 Amps. Wired each motor and ESC separately with its own dedicated fuse to give the maximum system protection. There is an extra fuse section allocated for auxiliary circuits, such as a cooling water pump and lights. Will try the original planned layout of 3 x 2835 motors with 30mm propellers and a 2S Li-Po battery first. Am hoping the reduced voltage will also make these motors more tractable. For the test program the three ESCs will be each controlled from an individual Rx channel. Once the final layout is determined, a more sophisticated and flexible control system can be installed. To minimize ballast, particularly around the stern, the battery will be housed as far into the bow as possible. After the test runs the final battery type, size and location can be established. To assess performance, hope to try both 2 and 3S Li-Po batteries. Planning to reduce heat build up by fitting cooling water jackets to the motors, these are easiest to instal at this stage so the wiring or mounts are not disturbed in the future. Have not decided the layout for the water circuit yet, but this easily can be added later. All that is needed now is the ice to melt off our local lakes so tests can commence.
Connect rudder to the mounted servo, servo box completed and glued into position, servo was mounted this way to leave the max height for rudder tube, as stern of the boat is narrow and when on the plane will be deep in the water. also the servo could be glued to the hull and the internal frame. Part of coupling attached, waiting for the motor! Also note some strengthening around the frame base, with right angled scrap. Reused cutaway plastic to make an inner sealed hatch this will be stuck down with ice hockey tape.
I'm with you there Skydive 👍What Boatshed means is the part of the rudder in front of the stock. Thinks: are you building an Offshore Power Boat or a scale Lifeboat? If the former then follow Boatshed's recommendation. If the latter and the rudder is 'scale' then leave it alone. Any braking effect, which usually is only significant in a fast racing boat model or other fast planing types, can be diminished by reducing the rudder servo throw at the TX. One should also consider how the original behaved, maybe they did 'dig in' maybe not. There has to be a reason why such rudders were developed, and surely not just to annoy modellers 😁 One more minor point that struck me - Ouch 😭 Your prop struts! "not that it provides a huge amount of support but adds to the scale appearance." Even in a model they can be important. To help reduce potential whipping of the propshaft, especially if the model is overpowered. Actually in the originals they were vital, especially in larger vessels. The purpose of these struts, in larger vessels 'A' frames, is to provide support to the end of the shaft which carries the prop weighing several tons and, more important, to carry the bearing for the outer end of the shaft! Actually in the originals the shaft tube, or 'Stuffing Box' would not extend significantly beyond the hull. Thus the strut or A frame was vital for the shaft end bearing, fitted immediately in front of the prop for maximum stability. Attached pics of my HMS Belfast (sorry don't 'ave nutt'n smaller with this feature🤔) show the arrangement. Have witnessed such construction in various shipyards around the world. Last one in UK was the first T45, quite an experience! 😲 In the end she's your boat, if it feels good do it! 😉 I would leave the rudder alone if it is 'as fitted'. 👍 I make my struts and A frames from brass sheet and tube. Cheers Doug 😎 PS Stick with the brass Donnie! 👍
So, managed to get all the glass clothing done at work at the weekend! So far, 1 coat of resin followed by 2 thinned coats to come. Today has seen all the fenders/rubbing strakes added. It took some careful measuring to get positioned correctly but well pleased with the outcome. It paid to pre-shape them prior to fitting. I’ve added filler where needed and a couple of coats of sealer, all seems to be faired in nicely. May need some touch up after priming. Also fitted the rudder mounts as today’s final job. Tomorrow should see the prop shafts fitted, motors mounted and will make the shaft struts. Postie arrived with some RNLI resin crew figures that will add a great touch when painted.
This is not a build but a modification of a cheap Chinese boat just for fun, I got a bit bored of scratch building projects as they take so long especially as I am not retired yet. The NDQ 757 Coastal Brother 1:25 Radio Controlled Racing Power Boat cost about £25 each from Amazon. These boats have a basic 27mhz radio and two 380 type motors which have forward and reverse and you steer by powering one motor or both for straight ahead. I bought two of these boats as they are light and about 24 in long, one to convert/upgrade radio, esc and brushed motors. The second was to upgrade radio, esc for brushless motors. The brushed motor version I put in two higher rated motors (390) with cooling fans built in, but same motor diameter but longer body I had to modify the mounts, kept same couplings and shaft/propellers. I did remove trim tabs (fixed) and replaced the straight running adjuster for a racing rudder. The brushless version is the same but has brushless motors 2x 2845 2600KV sensor less Specifications: KV(RPM/Volt): 2600KV RPM: 50000 Max Current: 42A The boats ran well but trimming needs attention, as hull is curved up at the back so trim tabs down, to prevent proposing, in-fact at one stage the boat left the water, but need to distribute weight towards the bow. Tried on 3S (11.1v) for brushless went well but got slightly hot after 10 mins. 7.4v for brushed also got slightly hot after 10 mins., and went nearly as well as the brushless. Surprised!!
I placed the rudder servo forward of the gear box. The folks at dumas wanted it placed. Against the coaming that runs along the opening of the hull! I found this angle troubling! The servo would be on a 180 degree angle. Which would be hard to get to. What if I don't have a screw driver. that's small enough to get to the screws! So, the servo has been placed next to the gear box! On a 90 degree angle which makes it extremely accessible. I have also placed the receiver. On the coaming using double sided tape. I placed the aerial on a piece of wood. I placed on a 90 degree angle! On my last Tug I put the receiver. On the motor mount floor. And the aerial against the coaming!
Evenin' Gerry. OK understood. So I assume you have no electrical equipment, experience or components available. Correct? For an 'electrics novice' I am inclined to recommend you start with standard brushed motors and NiMH batteries. Cheaper and easier to manage for a novice. In which case 3 x 380/385 motors with 3 x 25mm 3 blade screws would be a good start. Can send some info on a suitable dual+1 ESC and rudder mixer tomorrow, getting late here in Munich now 😲 Don't worry there's lots of clever (been there dun that) guys here who'll help you through 😉 More later when I've cogitated a little 😊 One final thought: don't finish planking/skinning the hull until the motor mounts and prop shaft hull breakthroughs are sorted out and trial fitted for alignment. Doing that on a completed sealed hull is a pain in the you know where🤔 cheers Doug 😎
Have added a few more planks over the last couple of days before and after bed as on nights. Gaps should be closed by Friday? Have also marked exit points for prop shafts and marked and drilled rudder mounting holes.
Many thanks Dave and Brian, I guess Brian's craft is much bigger and heavier than mine; 56x30 cm. Spec says weight 1.3kg with motors fitted but without batteries and RC gear. It came with a 9cm diameter 3 blade ducted fan, 13x? two blade thrust prop and a pair of 400 size brushed motors, the mountings for which limit me to 28/30mm diameter brushless. When I hauled the kit box down from an upper shelf to investigate I found the packing list and spares price list in both Deutschmark and Euro, i.e. circa 1999/2000!! Planning well ahead for the retirement 😉😉 In mine there are no rudders! The whole motor/prop mount is turned. Will see how it goes with that and maybe mod it later with rudders depending on how easy it is to control - OR NOT😲 many thanks for the tips 👍 Doug
At this point I decided to fit the rudder tube, water pick up and skeg. I was able to mount the boat in the machine vice by gripping the keel; this ensured that the holes are drilled absolutely true and square, 2 x 8mm holes are needed to take both the rudder tube and water scoop. I purchased the rudder assembly from a well-known supplier but I didn’t like any of the proprietary water scoop tubes on offer so decided to make my own. Whilst the boat is in the vice I also decided to machine the slot for the skeg to fit in. This required drilling a series of 2mm holes and then opening them up into a slot using a long series slot drill again giving an accurate slot which the skeg can locate into. Water scoop Having dealt with the woodwork, I turned my attention to metalwork. To bend the ¼” brass tube successfully it has to be annealed, (cherry red and quenched in water), then inserting a tight fitting spring inside the tube to stop any kinking I gently pressed it round a former to the correct shape. Springs removed I filed the end to the correct angle which gives an oval opening, but the end didn’t look finished, so I machined a thin spacer and then squashed it to suit the oval end and silver soldered it to the end of the tube, this gives a much better visual appearance.