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Member postings for Malcolm Frary

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: Bristol Channel Pilot Cutter
11/12/2021 10:59:33

There are such things, but the one that I looked at, while appearing useful. upon further reading, indicated that the author had little understanding of the real world that we live in, or general engineering principles.

While it is possible to calculate what loads the winch will undergo, there is no useful calculation that takes into account the wind forces that will be encountered. As a result, most of us go by the TLAR rule. (That Looks About Right). I suspect that even if his calculator was used, if you didn't de-rate heavily to account for the unexpected, the chosen winch would have a short life.

Thread: Robbe Smaragd
11/12/2021 10:38:39

A Hitec HS785HB will probably be a drop-in replacement. A Kingmax 6 turn winch is smaller and will generate the pull required, but being smaller is running much nearer its limits. The Hitec carries a larger diameter drum, so its 3 and a bit turns is fairly equivalent to the Kingmax's 6.

A bit of searching for a Futaba 8336 (I think its the same animal) turned up this spec -

Specification:

Dimensions: 59.4 x 29.0 x 52.2 mm

Mass/weight: 110.00 pond/g

Operating voltage: 4.8 - 6.0 Volts

Nominal voltage: 4.80 Volts

Nominal voltage: 6.00 Volts

Torque: 80.00 Ncm Torque: 100.00 Ncm

more Specifications:

Operating voltage:´4.8 - 6 Volts (from receiver battery)

Current drain approx. Idle 9.5 mA - No load 230 mA - Nominal load 1.4 A

Drum Ø:´38 mm (winding Ø

Winding travel: approx. 12 cm/revolution

Revolutions: approx. 2 - 5 (4 revs. with Futaba systems)

Torque: 100 Ncm corresponding to:´approx. 11 kg with 17.5 mm drum approx. 5.3 kg with 38 mm drum approx. 3.3 kg with 60 mm drum

Suitable for sail areas up to about 0.65 m 2 with the 38 mm drum.

Edited By Malcolm Frary on 11/12/2021 10:39:56

Thread: Bristol Channel Pilot Cutter
10/12/2021 10:22:42

The usual cause of tangling with a drum is lack of tension. When it unwinds, tension is needed to keep the line tidy. With good wind, the pressure from the sail "might" do the job quite often. Any other time it is a certainty that the line will hop off the drum and make friends with almost anything.

There are several cures.

Easiest is an elastic line above deck that pulls the line out from below. Has the minor disadvantage that the elastic has to be regarded as an expendable spare part. Since all of the power generated by the sails goes through it and the arm develops quite a considerable twisting force, a really solid mount is advisable. As is ensuring the the arm does have room to swing. ( A club member ran one with a transmitter with not quite the right settings. When it got to the travel limit determined by a frame, it tried to mash through the frame, but managed to mash the splines instead..)

Next is the continuous loop. Most winch drums have two layers. The loop starts with windings on the lower spool, heads off to a turn point, goes over a straight run long enough for the required travel, turns and comes back to the upper spool. As it feeds out of one, the slack is taken up by the other. Zero chance of a tangle. The take-off for the sails happens on the straight run, which can be above or below deck, builders choice. A 6 turn drum winch needs about 17". The shroud that you get with some winches is helpful, but by no means totally foolproof with a single ended setup, but this might depend on the type of line used. Since the pull is linear and always in just one direction, mounting is vastly simplified.

It doesn't matter which system is used, you don't want potentially slack line below deck, while practically nobody can design a machine that can tie knots, mother nature does it for fun. I can vouch for this having had the slack line from an arm tie itself round the slide switch and turn it off when pulling the sails in. That was in a Victoria done as per the instruction book.

Thread: Very old Vosper MTB
23/11/2021 09:43:53

NiMH packs appear in increments of 1.2 volts. A 7 cell pack will be labelled as 8.4 volts, an 8 cell pack as 9.6. The 7.2 volt packs have 6 cells.

Traditionally, with a 2 channel set from back in the day, the right hand stick going left and right does the steering. The servo for that job usually plugs into channel 1. The left hand stick up and down is the throttle and uses channel 2. As a result, the first sign of radio interference (the bane of 27MHz AM) is the rudder servo twitching.

With modern sets having 4 channels, it becomes 1 for rudder, 3 for throttle, but still the same sticks.

Thread: What Problem ???
16/11/2021 09:16:49

No one metre size sailboats.

Thread: Returning modeller
07/11/2021 09:21:29

With 2 ESCs on a Y lead, both ESCs are getting the exact same signal. What they do with that signal depends on how equally they were set up to respond to that signal.

After the ESCs have responded to the signal, they tell their motors what to do. Just how well the motors respond depends on many factors, as mentioned previously.

If the transmitter stick is set to "normal" and a motor runs in the opposite direction, reconnect the motor with its wires crossed over. If required, repeat with the other motor. Using the "servo reverse" to sort out motor rotation rarely has a happy ending. Unless it is a Futaba transmitter, because they used to like to reverse their signal logic - don't know if that is still the case.

Thread: boat size
31/10/2021 20:21:45

With eyesight not what it was and fingers seemingly getting bigger as time goes on, my natural tendency has been to operational models. Changing weather has helped with the decision. Not much detail, choice of size of fittings, and sailboats get better with a bit more breeze.

As others have noted, detail is independent of scale - larger scales mean that more smaller details get added. If looking to do a model that stands out in a crowd, or in a show, there is the same proportion of fiddly little bits on a big project. But because it is bigger, lots more of them. It's a fractal thingy - the closer you look, the more there is to see. Or make and fit. Cabin cruisers can get by very well on finish and presence on the water, but wanting every possible detail can result in a lot of detail work.

An evil offspring of mine bought me a couple of those metal puzzle type model kits a few Christmases ago. I was very glad that I had a loupe to clip on to my specs frame. And tweezers and very pointy pliers and a good bench light.

Thread: stuffing tube bushings
28/10/2021 11:40:14

On an old model that I ran a considerable time in salt water, it developed an interesting "engine sound" that was actually the shaft wobbling about. When the bushings were checked, they were fine, but the shaft wasn't. Probably something to do with the lake "water" being a combination of salt, silt and stuff. A bit of heating and careful knocking allowed a complete replacement. Since the tube, on examination, had some matching corrosion, complete changeout was not a bad move.

Thread: Best budget esc for 6 volt 7 amp Decaperm geared motor
22/10/2021 09:08:41

When using anything involving a BEC that the voltage regulator almost always works by losing some voltage, some more than others. When the supply voltage drops too low, different ones react differently. Usually the output voltage drops, sometimes, and it might depend on the load, it cuts off. Some radios can tolerate a bit of voltage drop, some don't and switch themselves off until they get the required voltage back. There are BECs out there that are able to step up from a lower voltage as well as step down, but they are "exotic" and therefore normally expensive, and don't get used in low cost products, or products like RC gear where price is important.

Using a separate battery gets round marginal voltage supply problems as long as the red wire from the ESC to radio is disconnected. A BEC trying to charge a battery normally does neither the battery nor the BEC any favours, some BECs do not respond well to having a higher voltage battery connected to their output.

A 7 Amp motor will only draw 7 Amps under the right load conditions. A resistance controller needs to be well matched to its motor under the assumed load. An ESC is less particular. What will drive a lot will just as well drive a little. While the 7 Amp motor might only rarely actually draw 7 A, it is usual practice to double that figure and pick the next higher rated ESC. So 15A is a good start, but any higher rating will work as well, with the exception of the "320A" ESCs which are widely pushed on t'interweb.

Thread: Help with identifying wooden yacht, and rigging
12/10/2021 09:29:07

My favoured way is to have the line appear above deck either via a small hole in a rearward facing vertical panel, or through the deck using a fairlead, or bit of plastic tube. Or copper or aluminium tube. In any case, with the exit hole facing backward to avoid creating a scoop.

This will invariably put the line where it is not wanted for the final trip between a point on the centre line and the boom (i.e. where the existing hole is). A three-point bridle sorts that. One ring, three adjustable lines each with a hook on the end to fix to three convenient points on the deck. One adjusts fore and aft, the other two centre the ring over where the hole was. Through deck pulleys look nice, but costa lot and provide a hole in the deck.

Electronics are best mounted as high as they will go so that any wet that gets in doesn't slosh into them. That, and generous use of Vaseline and/or something like CorrosionX so that any wet that hits them falls off. And storing with the hatch open so that damp air can dissipate. In the case of a 2G4 radio, they usually only have a short aerial lead. Since the aerial needs to be as high as possible, so does its attached radio.

11/10/2021 09:04:29

It is an R36R (restricted 36", radio). No idea what particular design, but it does look a lot like the line drawing that appeared in a list of plans.

Rigging is a fairly standard sort of arrangement - most of it is to either stop the mast falling over, or to relieve strain. The backstay stops it falling forward in a following wind and offers some tension to help sail shape. The masthead crane might be either a rigid fitting or might be a seesaw with a tension line on the other side. The sidestays stop it falling over sideways when the sails are collecting force to drive the boat. They are also very useful when picking the yacht out of the water without bending too far.

Some boats have a forestay to prevent the mast being pulled over backwards by the force of the backstay. Most racing classes dispense with that in favour of using the foresail, which is carried on a luff line on its leading edge and the pivot arrangement that hooks it to the fore deck. To stop the pull of this line stretching the rear edge an adjustable line is fitted from the top to the rear end of the jib boom.

As this looks like a deck stepped mast, all of the support lines are vital for transmitting the forces gathered by the sails down to the fin under the boat via the hull structure.

While the running rigging lines are very tidy above deck, I would prefer a rearrangement. I don't like lines carrying strain going through hatches. Similarly I have misgivings about any line that simply pops out of a flush hole in a deck. Yachts go in windy weather (its what they are for) which usually involves lumpy water which in turn means water on the deck. Any hole is an invite for water inside, where it is not wanted.

Thread: Robbe receiver
06/10/2021 09:55:32

It is rarely reliable trying to join different generations of RC together. My first radio was a Maplin brand one. Servo plugs in a very substantial housing (industry "standard" "Molex", maybe) but had the pins on the usual 0.1" spacing. But with the three sets of connections in one row across the receiver. "Modern" low profile plugs would fit.

Apart from a couple of old Futaba servos I was given, which had pins and unequal spacing. The copper tube adaptors worked but it was, at best, a bit iffy. If the receiver had had receptacles rather than pins, pins could have been easily created by using the right size nickel silver wire, but would still have had that bit of uncertainty.

Then there was Sanwa, who kept to the expected mechanical standards, but shuffled the pin order. Everybody else went -,+,signal. Sanwa didn't, and if you mixed without rearranging the wire order, you had a reverse connected radio battery. Thankfully, nowadays everybody has settled on one standard of plug layout, any manufacturers foibles of using locating key tabs can be cured with a sharp craft knife.

I don't know what the signals were on the old 4 wire servos that I have heard of, but since before I started, everybody has worked to the same signal standard, so if the wires can be plugged in in the right order, it will work.

E&OE

Thread: Motor size/ set up
05/10/2021 09:12:56

For working a ramp, something like

https://kitronik.co.uk/products/2589-fs90r-360-degree-continuous-rotation-servo

or

https://www.digikey.co.uk/en/products/detail/adafruit-industries-llc/2941/5823442?utm_adgroup=Motors%20-%20AC%2C%20DC&utm_source=google&utm_medium=cpc&utm_campaign=Shopping_Product_Motors%2C%20Solenoids%2C%20Driver%20Boards%2FModules&utm_term=&productid=5823442&gclid=EAIaIQobChMIyryH9-Wy8wIV4-jtCh18LARvEAQYASABEgKr7fD_BwE

might do.

The first is a servo with continuous rotation, the second a motor and gearbox requiring an ESC or switcher. Neither is proportional, you just turn it off when the ramp has got there. From posts about similar projects elsewhere, the ramp needs some extra weight to ensure that it will drop.

If it is the foot long one like the Italeri one, a 385 might be overkill. A 140/1 as sold by Component Shop might be more appropriate, and much easier to hide.

Thread: Robbe receiver
03/10/2021 09:44:30

No experience with this particular EC other than what a google search has turned up. From the very scant information, it has no BEC, so needs a 5 volt input, the red 2 pin does that. It has the conventional pair of big thick wires for main power, and two more for motor connection.

The weird bit is the signal connection. Most manufacturers use a 3 pin connection that caters for both control power and signal. This one uses a 3 pin receptacle, but only the outside two points. Presumably black for ground and white for signal.

So, on a modern radio, the radio battery would plug into the "Batt" or "Ak" hole, the signal plug into the preferred channel, the steering servo into the chosen channel for that, and the ESC red plug into a spare channel to give control power to the ESC.

Unfortunately, with a 2 channel set, there are not enough slots, so a choice needs to be made.

1 Get a Y lead. Plug it into the throttle channel, plug the black two (3 connection, only 2 used) pin into one leg, the red power into the other. This might entail a bit of minor surgery on the red plug, Y leads are generally intended for flat plugs. Receivers have pins, the plugs that fit them are usually shrouded receptacles, thus technically, sockets. I tend to wait for a show and go to the Component Shop stand for things like that. Or, over the last couple of years, mail order.

2 Winkle the red wire out of the red two pin (assuming that its a floating socket) and insert it into the centre hole of the black three. This will cause it to be wired like every other ESC on the planet.

3 Go modern radio. 2G4 sets tend to start at 4 channel with a 6 channel receiver and cost less than a replacement second hand 27MHz receiver.

4 Get a more conventional ESC. Mtronics and Quickrun spring to mind. Unless you already know that the Bobs board is a perfect match to the motor, vastly better control will be had with an electronic unit.

I have no notion of why the makers thought that this was a good idea without illicit substances being involved, but there might be a reason in there somewhere.

Thread: 1:33 scale boat fittings and people
26/09/2021 09:01:27

Another check is the height of railings. These should come about half way up any figures. Doorways on work boats are not always a reliable guide.

Thread: Robbe receiver
26/09/2021 08:57:06

Being Robbbe, the markings are likely in German. At a guess, "AK" is short for "akkumulator". Maybe Dr for direction? or maybe drive?

Channel 1 is traditionally steering, and is usually the furthest away from the battery connection. Throttle is the one in the middle. Normally receivers use the outermost connection pin as the black/negative/ground line with the next inboard being red/positive line. These pins are usually common across the rows, only the innermost pin on the two columns is unique and carries the signal for that channel.

If using an ESC with a BEC, you don't need to use the battery connection anyway, it's been done for you.

Thread: 1:33 scale boat fittings and people
24/09/2021 10:10:39

Boat kits tend to be fairly "round number" scales. If metric, 1:10, 1:50, 1:100 etc. If imperial, usually something convenient for reading off a ruler, like 1:12 (inch to the foot), 1:48 (1/4 inch to the foot) and similar, or a binary scale, like 1:16 or 1:32. But occasionally, a model is designed to be a certain size to fit either the drawing board it was designed on or the box that the kit is going to ship in. This does result in strange and unlikely numbers.

Figures can be got from other hobbies that have other ideas about suitable scale, but it has to be remembered that while people are all the same scale, they are not the same size. Answer is to look for figures the right height, or near enough. A bit smaller usually fits more easily. Boats are very much a minority hobby, and this is reflected in the supply of the extra bits. Very specific scales require the right tooling, which is a big outlay for a small market. 3D printing is one way forward, but such figures, if they are scaled for one single application, will take expensive time to produce.

Fittings in the model boat world tend to go by size. Things like cleats and bollards tend to keep the same broad design whatever the size - bigger ships/boats get bigger fittings, but they look the same.

Careful measuring on a 1:33 model might show that it is really 1:32 or 1:35 anyway.

Thread: How Big is your Club Lake?
20/09/2021 18:19:23

For casual individual visitors, there is a very definite speed limit in the Lake District, but it is recognised that organised groups can and do get dispensations for events.

https://www.facebook.com/recordsweek/

The information is a bit dated, and times might have moved on. Usually, they don't move on for the better when officialdom gets involved. Speed week usually happens the first week in November.

Thread: Help with Project for School Children
13/09/2021 09:29:56

Hopefully the original kids have benefitted from the experience. The next lot could also benefit.

Thinking about sail power, in the elder days I used the plain plastic bags from supermarkets as sail material. This was before they discovered how to print on them. A suitable alternative is white, handled, bin liners. Ordinary sellotape is excellent edge strengthening. Extra science point - anybody going this way learns a great deal about static electricity. Rigging line, no point looking for alternatives, a 300 metre bobbin of 0.48mm fishing braid can be got for £10. Adjuster can be readily made from buttons from dead shirts.

Thread: Returning modeller
09/09/2021 20:26:47

Winches come in two varieties.

The most common type on sailboats is a proportional type. Whatever position the stick on the transmitter is in, or5 is set to, so the winch assumes that position. Sometimes eventually, sometimes very quickly. Depends on the particular type.

Non-proportional winches have a couple of sub-types. If everything is adjusted as it should be, "spring centre" should result in neutral.

Easiest to understand is the simple motor + gearbox worked by switches off a servo. Throw one way, it winds in, throw the other, it winds out, in both cases, flat out.

Easier to fit is effectively a continuous rotation servo which is really a motor and gearbox driven by its own self contained ESC. When at neutral, like any other servo, it sits still. When the stick is moved, it drives, one way or t'other. As its movement approaches that indicated by the stick, the motor slows. If it drives without the stick being moved, the system "thinks" that the stick is not at neutral.

A non-proportional setup is best with a centring stick - a ratchet stick is more suited to a proportional winch. Less stress keeping the left thumb steady. Getting the centre offered by the stick to match that required by the winch is the trick. If there is no adjustment option on the winch, what is left is the transmitter trim slider.

It doesn't matter what it was set up for, in radio control, what matters is the pulse length that comes out of the receiver. As a sort of standard, a bit longer than 1.25mS corresponds to a servo plugged into that channel being full left. 1.5mS puts the servo centre. 1.75mS puts it full right. On a normal boat ESC, this corresponds to full reverse, neutral, full forward. Or if a winch, drive out, stop, drive in. On a "forward only" ESC, 1.25mS is stop or maybe idle, 1.5mS is half speed, 1.75mS is full forward. This is true whether the transmitter is sprung or ratcheted.

If it drives to one end and stops there and won't be controlled back, its broken. Or the winches centre is so far out that stick movement doesn't go far enough. The servo tester will show this fairly instantly.

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We welcome well written contributions from Website members on almost any aspect of Model Boating with a particular emphasis on practical hints, tips, experience and builds.

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