Here is a list of all the postings Malcolm Frary has made in our forums. Click on a thread name to jump to the thread.
|Thread: Criteria for boat servos|
A normal servo has an arm that swings to mimic the position of the controlling stick on the transmitter. Usually a swing of about 90 degrees.
A "sail winch" is a servo that is geared to "swing" through rather more and drive a drum rather than an arm. A 6 turn winch will travel through 2160 degrees, a 2 turn through 720. There is extra gearing that lets the same position sensor "think" it is dealing with the standard 90 degrees.
Beware of "360 degree" servos. Manufacturers sales and marketing are a bit casual about the meaning. Some think that it means "will go round and round forever", some think it means "will act like a normal servo, but is arranged as a 1 turn winch". Usually, it is the former, which gives a box containing a motor plus a gearbox plus a small ESC. Works well with a spring centre control once you get used to it, minor drawback is that it doesn't have end stops - winding in it can try to compress the structure of the boat, over winding out can cause a reverse re-wind, which can lead to confusion.
Any guesses without some details of the actual model must be guesses, even if the principles are sound.
For a 17" sailboat - Look at the servo specs - "under 1/2" wide, no se looking at named sizes, "mini" and "micro" tend to be a bit flexible. There are analogue servos (digital not needed) around 0.45" wide. If working a balanced rudder, probably any of them, unbalanced, metal geared is preferable.
The sails are not going to offer a huge load, but there are no winches smaller than "standard" size plus a big lump for the drum and shroud. This leaves arm type servos, just look at metal geared and the highest torque figure available.
https://servodatabase.com/servos/all has a fairly comprehensive list.
Edited By Malcolm Frary on 21/01/2021 10:51:40
|Thread: Returning modeller|
Alternatively, take two strips of aluminium, form them into a pair of conduit clips (looked at end on, a near semi circle with a flat ear at each end), clamp the motor between them, use the ears to fix the motor down. Has the benefit of providing a bit of extra surface area for cooling the motor.
|Thread: Veron Veronica and Radio Control|
Modern sail winches are proportional, they position themselves according to the position of the controlling stick. This is why most yotties prefer to use a ratchet stick for the sail control. Saves wear and tear on the left thumb.
If the rotary knob that Ashley mentioned is a proportional channel, it will do the job OK.
Using a single line usually means having an elastic line tensioner to ensure that the unwinding drum does not leave a pile of slack line which will tie itself round anything available. Unshrouded drums wrap the line under the drum, shrouded ones find other things to tie the line to.
|Thread: flexible propeller shafts|
Tugs do need reverse, flex shafts tend to unwind themselves in reverse, so they don't get used on tugs.
|Thread: New RC modeller|
Modern 2G4 radios are allegedly immune to radio interference, and will remain so until some creative soul manages to do it. But that only covers interfering signals entering the system via the radio. A big enough signal can be picked up by wire going to any electronic devices. ESCs can give stuttering or uncontrolled motors, servos can twitch.
Suppressors can keep the interfering signals that the motor generates within the motor, where they are harmless. If checking the new motor shows that the terminals have a thin wire vanishing into the insides of the motor, they may be already fitted.
While your boats radio might be unaffected, there is a chance that somebody else with an older radio sailing near to your boat could be affected.
|Thread: Sailing Yacht to Restore|
If going down the sewn cloth route for the sails, it is well to remember that the threads of the cloth should be at right angles to a line between the top of the sail and the trailing corner, not the leading edge. Reduces the saggyness and baggyness over time.
Looks like either a Star, or one designed by somebody who liked them.
The lightest venetian blind line that you can lay hands on is a good rigging line, both standing and running. Doesn't stretch, low surface friction. I've also used a fishing line that I believe was called "salmon backer" but the label fell off the reel years ago. Again, braided and non-stretch.
If you know somebody who is willing and able to sew, an old poly cotton shirt makes fine sails. Otherwise, Nylet, Housemartin, Sails etc will either have the right sails listed or be able to do bespoke ones.
It looks like a free sailing pond yacht, it will need to be sailed at a suitable venue - one with access all round. Such venues are not as universal as they used to be, remote control allows sailing in many more places. With modern components, fitting a radio is much easier than it used to be.
|Thread: Can you help identify this 6 Meter sailing model|
The presence of the Braine self steering says to me that it is a pre-1950s design. Later designs would "probably" carry a vane.
Just what it is, who built it and when are a whole set of different questions.
It is a thing of beauty, though.
|Thread: Propeller shaft lubrication|
Not tried it myself, but there is a faction who favour "fishing reel grease". One option with this comes in a pack of two - one oil, one grease. There might be a case for squirting oil in. then following it with a dab of grease.
Oil does the lubing low in the tube, the grease forms a water resistant block under he filler.
Getting oil down a filler is no problem, the grease might benefit from being scraped into the hole at the top, then pushed down with a suitable rod. In theory.
|Thread: red empress|
The superstructure does look like it was built to a different scale to the hull. I've got some drawings tucked away somewhere where the drafter decided it was a GOOD IDEA to draw the superstructure to a larger scale tan the hull to help "clarity".
An over-sized superstructure will act as a sail when hit by a side-wind. The force of the wind will cause a lean, in a case like that, a high CG will not help.
Scale boats are an oddity in modelling.
Considering model rail, if your loco is too heavy, you say "hooray" because it will pull more without slipping. If you build a plane too light, it flies more easily, if a bit heavy, more power usually sorts things.
Scale boats have to be the correct scale weight. If too heavy, they don't float. If too light, they tend to sit too high in the water and become unstable, fall over and sink.
The weight also needs to be in the right place, not only fore-and-aft and side-to-side, but the height is also critical. Too high and you get instability. I have yet to notice any model boat with the CoG too low. The main item governing canter of gravity is usually the battery. In a tug, probably an SLA. These can be mounted laid on one side, which lowers the CoG as opposed to one mounted stood up. If a lighter type of battery is used, ballast will be needed, preferably as low in the hull as possible.
A few years back a newcomer to the hobby tried a Puffer, which was vastly under ballasted. Despite being repeatedly advised not to use it in the wind conditions that day, he persisted. Predictably, when the wind hit it, it headed away, lost all control and eventually foundered. We never managed to recover it.
|Thread: Propeller shaft lubrication|
Ask any group of 10 model boaters what they use for shaft lube and you will get at least 10 different answers. If they have working boats, they will all be correct. Much depends on the nature of the model, and the nature of the water being sailed in.
Edited By Malcolm Frary on 12/12/2020 10:02:24
Unless a huge amount of space is available, for anything involving a submarine and a supply or hospital ship, a smaller scale might be a good idea. Maybe N at about 2mm/ft. or 1:144.
|Thread: ac75 Ineos yacht|
It's a point that gets plenty of mention at the poolside. A real yacht has somebody on board feeling what is happening, and they have their reaction time to what they sense is going on, usually preventing a disaster. Foilers, almost by definition, to get their performance, are seeing how close they can get to the edge of disaster, and need very fast reactions from the crew to avoid it.
Even if it doesn't have a full size equivalent, a model sailboat can be considered "scale" - it is operating a "scaled" conditions, which usually involve squares an square roots. A 1:25 model gives you about 1/5th the time to react, and your indication is not feeling the boat, it is seeing what the boat is doing at a distance.
In earlier AC events, everything had to be purely muscle powered, what with it being a sort of athletic event. I have gathered, right or wrong, that the trend has been to have a squad of "grinders" - muscle bound athletes whose task is to continuously work pumps which are capable of building up and storing hydraulic pressure. A feasible way to give rapid handling of sizeable masses.
While "ye cannae brek they la's a physics"* it is amazing how far they bend.
I can't really see them being mainstream working models anytime soon, but then, who knows?
|Thread: polarity of servo wires|
I have heard tell of servos that do have reversed logic, at a price. It is also possible to create one by taking the servo apart, reversing the motor connections AND transposing the two outer connections to the pot. The servo reverser is by far the simplest and cheapest option, and the most likely to work.
|Thread: help - 1/250 scale Yamato|
The single 280 will be enough to see the propellers turn and the model move, and not much more. Probably enough for the model designers to realise their intention in the circumstances that they imagined at the time. Running the numbers, 150,000 SHP on the real thing gives about 8 Watts out of the motor at scale, probably needing about 15 Watts of power into the motor(s). Way too much for a single 280, well within the capabilities of a group of 385s running on reduced voltage if the intention is to move a 10 lb model at a bit over 3 feet per second.
Cavitation is only likely if the kit props are poor - plastic kit moulded ones can have very thick blades which create more turbulence than drive. Most "cavitation" on models is actually aeration - air being sucked down from the surface. Model battleship props are likely to be far too deep to be affected.
|Thread: help with rc/control|
The two wires probably had a small slide switch on the end, used to switch the control part of the ESC on and off. If a previous owner didn't feel the need for it, or if it died from old age then shorting the bared ends of the two leads together would result in the ESC being on all the time that it had power.
|Thread: viper marine 15 bec s/c|
Zero experience with Ace Commander gear, but the last time I saw this the transmitter had a well hidden little switch marked "mix" which he had managed to slide. That was on a Joysway lunchbox transmitter.
The side slider usually just operates to swing the position of the pot a bit one way or the other to mover the center position. Sliding that will move the deadband, Moving it far enough will cause the ESC to tell the motor to start turning.
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