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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: Trying to identify my boat?
03/05/2021 08:19:05
Posted by M Harvey on 02/05/2021 14:07:19:

I can report back that the metal hull is not at all magnetic... so what does that indicate?

M

As said earlier, aluminium or nickel silver. Litho plate was fairly available back in the day and was an aluminium alloy. Any sight of printed image on unpainted surfaces would give the game away.

Aluminium needs its own special soldering techniques, nickel silver, being white brass, responds well to more basic soldering.

Thread: Bristol Channel Pilot Cutter
02/05/2021 10:21:01
Posted by Dave Cooper 6 on 01/05/2021 17:32:35:

Made contact with an on-line colleague in Oz who has nearly completed a 56" pilot cutter. He reported that he had far too much hull displacement and now wishes he'd gone for a lower displacement design...(he needs a trolley to move it around and to launch it !).

Archimedes knew what he was talking about.

A 50% increase in size of a boat makes it over 3 times as heavy, if it was a heavy model to begin with..............

Thread: Identification
02/05/2021 10:15:57

Rule of thumb for a yacht mast - 150% hull length. So 1.9 metres tall. Or about 6 feet.

In old money, it is about 50 inches long, so "could" be an old Marblehead, or based on one. Before radios were mainstream, racers were solidly built and carried a vane for steering and had a shallow heavy fin. With radios came the lightweight construction and long fins. Not 100% sure which was first.

Currently, there are the Canterbury and Nottingham J class, which are 50" long, weigh 15 pounds and carry IOM rigs and have the shallow fin weight.

Thread: Trying to identify my boat?
02/05/2021 10:00:50

I remember tin plate being discussed widely as a boat building material from '50's magazines. Most preserved food came in the source material back then, and for larger sheets, so did motor oil. A quick way to check is a magnet - if it sticks, there is steel in there. If not, and the metal is "silvery", aluminium or one of its alloys. Old Litho plate? It used to be a fairly common modelling material back when printing was printing involving metal and etching rather than ink being squirted in a pattern direct to paper.

But if there is any rust, there must be steel involved.

As Ray suggests, resin sloshed around the inside. I would just add that adding sticky tape to the outside first will stop any leaking resin from marring the outside and creating the work of removing it.

Thread: May 2021 Model Boats Mag
01/05/2021 09:39:55

It would be nice to have pocket mags actually publish in a reasonable time frame. It is now May, the paper copy has been out since April 21st, having just this minute checked my pocketmags link, it has yet to appear.

Thread: How to calculate the scale of my model boat...?
29/04/2021 10:25:00

A starting point would be the stanchions at the bow. A reasonable guess would be about 1 metre high. Then check similar heights elsewhere, such as on or around the superstructure. The lower row of superstructure portholes look suitable for viewing knees, and are probably artistic licence, same with a few other details which might be better lost in a refurb.

If a model crewman looks OK if placed anywhere on the model, it must be to a constant scale, if he is a midget in some places and a giant elsewhere, it isn't.

Thread: To braid or not to braid...?
29/04/2021 10:08:38

Assuming that braided wire means stranded flexible wire, rather than the unlamented Litz wire that was always a total pig to terminate or the stuff found as the outer shield on co-ax and similar.

Flexible wire, by its nature, flexes. It absorbs vibration and allows you to work around it easily. Rigid bits, like soldered terminations benefit from added stress relief such as heat shrink sleeve over the area where it transitions from solid (solder) to flexible.

Solid single core does an admirable job of putting the electric where it s needed, but does not like vibration. It either provides a weak spot that eventually breaks or transmits the force into whatever it is terminates to, which might, in turn, provide the weak spot.

Working in the vicinity of wire, flexible lets you move the wire out of the way, solid doesn't, or at least, not easily.

Thread: Battery life
26/04/2021 20:38:59

A lot of years ago I was chatting with George Turner at a CADMA show. He was playing with one of his torpedo boats. I did ask what his run time was.

"Oh, almost and hour" he said.

"Unless I run it like this" he went on, turning the wick up.

"I like running it like that".

Temptation is strong. Assume shorter runs.

Thread: Size of a typical mast
26/04/2021 20:32:55

There is a school f thought that reckons that higher aspect sails are more efficient, probably true for the real thing. My thought is that since model boats generally sail at the bottom of a hole in the scenery, the top bit gets moving air before the rest of the sail simply because it is less sheltered by the bank.

Thread: JIF 65
16/04/2021 16:04:16

If using 1.6mm stainless, the tube from the inside of a dead ball point pen refill is a sliding fit. It will need support, but a brass tube with a matching ID will do. The tubes from cotton buds were good, but they may now be environmentally banned. At my secondary school there was woodwork in the first form, art extended into the second form and that was that.

If using a vice and a drill to persuade a 3mm brass rod to fit in the thickness of the rudder, rubbing a bit of a brass plug pin will be as nothing. It does help to have a dremel or similar to drill the hole, though. Having said that, commercial tiller arms are cheap. ish.

If sailing in salt water, mixing and matching metals in contact with each other is a definite no-no, either in the water or just somewhere on the boat..

I've just spotted something in a flyer from Banggood - it seems that what I have been calling a bellows (for waterproofing round a rudder linkage rod exit) is called by them a "Waterproof plastic organ sleeve" or, rather wonderfully, a "water against accordion part".

Edited By Malcolm Frary on 16/04/2021 16:12:51

15/04/2021 21:06:47

Bumper looking good - nice to see a thought exercise work out.

Tiller arms. I like to use a piece of brass that has been lovingly crafted with a convenient hole to poke the rudder shaft into, and a threaded hole, with a matching brass screw. Or a pin from a 13A plug, as it is known. Just needs a hole drilling at the right distance to accept the control rod. If using a Z bend, a bit of filing will thin it down easily to allow threading the rod.

Avoid at all costs dissimilar metals for rod and tube. Electrolytic welding is annoying to deal with a week or so after the first sail. Plastic tubes don't have the problem. Turning both shaft and tube in the hull against the glue holding it in place puts a considerable strain on the servo.

Training your right thumb and having a reliable parallelogram linkage layout is the conventional way to go. It's conventional because it works without the hassle of over thinking your way into problems.

If using wood for a rudder, laminating with the sheets having crossed grains works well. Also lets you choose whatever method you prefer to stop the shaft twizzing round inside the rudder. An L bend is totally effective, filing a couple of flats on the shaft and sitting the result in epoxy works as well. When balsa is laminated and coated, it is very much strong enough. BUT since it is the most exposed part of the entire project, my preference is to regard it as a mechanical fuse - I will break something that is easy and cheap to replace/repair rather than something difficult within the hull. I might mutter a bit about that, but for me it is better than the alternative.

Thread: Power Supply
11/04/2021 14:04:23

1, 2, 3, 4 & 6. Motor whistling under ESC control. Yes, they do. In the extreme elder days, a motor speed was controlled by wasting power in a resistance element which had to be very closely matched to the motor. Nowadays, the variation in power is got by switching the supply on and odd VERY rapidly. Due to the constraints of the electronics involved, this usually results in a coil held in a strong magnetic field being moved in a series of steps at a frequency that is audible. Older ones didn't work just as well, but ran on a lower frequency and rumbled. Different motors differ in their susceptibility to produce sound, but since all motors contain the same elements as loudspeakers, they all do it. Just that some are louder than others. Some ESCs you don't hear, but passing dogs might.

Personally, I appreciate the whistle. It lets me know that something is going to happen.

All devices that plug into a receiver run on the timed pulses coming from the receiver. A mixer, in theory, takes the timing from the throttle channel, and looks at the pulses coming down the rudder channel. If the rudder channel pulse is saying "go straight", the throttle channel just passes its information along, unadulterated, to both ESCs. If the rudder channel is giving a longer or shorter pulse, indicating a turn, then the mixer adds a bit to one output, and subtracts a bit from the other which tells the ESCs to change their outputs.

The number of possible permutations is scary. I tend to break things down in an effort to get my logic straight by using a couple of servo testers as known supplies for the signals instead of the radio. Radio switches and added computer controls do muddy the logic somewhat.  

The other handy items are a pair of servo Y leads and a pair of spare servos.  These can be used as meters to look at what signals are being passed round the system, and in the case of ESCs, you get to see what they are being offered and are not stuck with just observing the motors behaviour.  Much problem solving consists of finding ways to break a sequence down and finding out why actuality has diverged from theory.

Edited By Malcolm Frary on 11/04/2021 14:11:35

Thread: JIF 65
11/04/2021 10:21:49

Arm vs drum, there is considerable debate, and the answer is always what works for you.

Arms are on the face of it simpler, but this only applies if various factors are true.

The mounting must be strong enough to withstand the twisting forces without the servo moving in the mount or the mount twisting the hull.

The servo needs to generate the torque required to pull the sails in in the strongest wind anticipated (and on some days, a bit more)

The electrics need to be strong enough to supply the current that a powerful servo can try to draw. Good battery, good wiring.

Great care is needed laying out the running line. Travel is always at a premium with any arm system. Usually, the line coming to the arm is doubled back to a fixed point. Travel is doubled, torque to the line is halved, but the same twisting force is applied to the mount. It is a good idea to ensure that when "full out", the end of the arm is as near as possible to the entry and tie-off points of the line, and that when "full in", the line passes as close as possible to the servo arm screw.

Drums are generally not as fast as arms, but do offer the same pull throughout their range.

They are generally less greedy for amps.

A shrouded drum (and most of the servo size ones are) only needs to have the shroud leaning on the bulkhead that the line comes through and very little fixing. Any more is optional.

Travel is not usually a problem unless you need to actually lose some. My preference is a doubling arrangement above deck. This does slow things a bit but allows (with a suitable spread of the ends of the double) for greatly increased torque when it is needed, i.e. close hauling.

A drum does give the option of a single line, single ended system, or a continuous loop system.

Both systems benefit from having an elastic line helping take up any slack. Very essential on an open drum, single line, a good idea on a shrouded one, also on an arm. In light airs, where the sail relies on the wind to move the sail out, it might not keep pace with your command. The result is slack line. Unshrouded, the line falls off, shrouded, it can try to tangle inside the shroud, with an arm it will try to tie itself around anything available. From experience, the on/off switch is deeply annoying. The elastic line does, of course, give extra resistance to pulling in.

My boats that have a low after deck usually have the line exit via a tube that essentially slopes down to its exit point. A longish tube with a bit of slope slows water down enough and allows any that finds its way into the tube a way out when the boat isn't burying hat bit under water. The wet line, when pulled in, does bring some in with it, of course. For the rudder rod, I use a bellows. Idea borrowed from the power boat lads. A very similar item is used by cyclists on the brake end of their cables.

Thread: Power Supply
10/04/2021 10:07:57

I hope he only said "ONE of the red wires". Unless running a separate supply, the 5 volts needed for the mixer, radio and anything else plugged into the radio has to come from somewhere, and that is usually the ESC that still has its BEC.

Actually cutting the red wire is a mistake. Much better to winkle the wire and its terminal out of the plug and tape it back in a tidy manner. Much easier to reconnect if that ESC plus its BEC is needed in the future.

Thread: JIF 65
07/04/2021 09:32:10

+1 on the cautions. Lead is useful, but dangerous stuff if mishandled at any temperature.

I had a more roundabout way of getting my ballast. I was going for a teardrop shape.

1 determine the volume. put the required amount of lead into a measuring jug. pour water in up to a marked level. Pour water into something handy, remove lead. pour water back in, bring up to level by dropping plasticine into the water. In my case, because I was doing it in two halves, half the weight.

2 Make the plasticine into the shape required. In my case, a full teardrop, so the shape, then whack it onto a solid flat surface. Shape was chosen such that the two halves would be symmetrical.

3 Coat the plasticine plug with thin grease like Vaseline. Take a plaster mould off it.

4 When set, dig the plasticine plug out and leave the mould to dry for a long time*, including giving it plenty of time in the oven. Total dryness is essential. *Several days, weeks are better.

Using the mould afterwards was much as described above. Pre heating and having it in a foil tray was deemed a good idea. If the plaster suffers a thermal shock, you don't want molten lead wandering over a concrete patio, even if it is outdoors and downwind. A plumbers ladle is a really good idea.

OTOH DF65 spare ballasts are available.

06/04/2021 16:22:55

RG65 rules

https://rg65.org.uk/class-rules/

mandate a fender made of an "elastomeric material". That's for racing, but pleasure sailing only means that having such is a good idea to reduce damage to your yacht in the event of an overly sudden return to the bank or to prevent damage to other boats.

Pine and oak do not deform, and so are more ramming devices. Balsa, if squidged, stays that way. D section fendering (in rubber) is available. I have heard of people using flip flop soles as donor material. One could be moulded using hot glue gun sticks, fixing to the bow probably using yet more hot glue. It taken about 20 years, but uses are emerging for the stuff. The Akela instructions suggested carving expanded polystyrene to shape, but that would probably act the same as balsa.

https://www.radiosailing.co.uk/df65-front-bumpers-2-pk-1061-p.asp are available as spares for DF65. No idea how they match yours for size.

Thread: Rigging
04/04/2021 10:01:00
Posted by Eddie Lancaster on 03/04/2021 09:46:18:

And many more sailings if my experience is anything to go by, according to my Tx my IOM has been on the water for around twenty hours and I am only just beginning to get an idea of what needs to be changed to improve handling, speed or pointing etc.
Eddie.

Yes, my usual advice is to just change one thing at a time to know whether that change has had the desired effect. One day, I might do that.

A thing about model yachting is that conditions, and possibly the problems being solved, can change in the time spent doing a tweak on the bank. Certainly they change day to day. Its's part of the continuing fascination. A single circuit of "my" lake even on a really nice day does offer a range of conditions. Even an oblong hole in the ground like Fleetwood (a superb venue for racing) keeps its interest because of these changes.

Thread: JIF 65
04/04/2021 09:43:16

On a racing type boat, and this was designed as such, it is normal practice to cover the holes with "hatch tape" "deck patches" or, as some call it, "sticky back plastic". Solid hatches are often held in place during sailing by tape, which is regarded as expendable.

Other means used are solid hatches, either flush or over a coaming, held down against a gasket by tensioned clips. Commercial models invariably need a bit of modification in this area, if the threads covering them are to be believed.

A bit of asymmetry in side to side weight distribution in the middle of the hull doesn't matter at all. The senior vote in where the weight is is the weight at the bottom of the fin, and that will be on the centre line.

A small, easily removable hatch is needed for easy access to the switch and battery, and possibly to get a view of the receiver to check that it is operational. Working holes in the deck required for heavy maintenance should only be needed once in a while, and can have a more permanent fixing - hence the single use sticky back plastic, or a plate with fixing screws and a gasket.

My take on waterproofing inside the hull is that a wooden hull needs everything it can get, but it has to be realised that a yacht leans over and getting a bit of damp inside is inevitable. An easy way to get rid of the damp* must be provided. Sealed compartments simply don't work. There is always a way in, but no viable way out. A good size hole high in a bulkhead will let unwanted water drain out with the boat on end, but prevent it sloshing about out on the water.

Going back to the rudder arm placing - I much prefer above deck.  Easy access should work be needed on the rudder.  The hole where the control rod exits can be waterproofed by fitting a rubber bellows as used by power boaters.  Much the same thing is used by cyclists on brake cables.

*Possibly a half pint or so of "damp" if conditions have been a bit exciting, but boats operated in damp air anyway.

 

Edited By Malcolm Frary on 04/04/2021 09:51:39

Thread: Rigging
03/04/2021 09:14:30

Wire rigging is great if you use screw adjusters, if bowsies are used, thread is needed. My preference is my reel of salmon backer (if I have remembered right, I bought it a long time ago and the label is long gone). Brown, braided sheath, running rigging slides easily, standing rigging stays put once you figure out how to tie the stuff, very resistant to stretching. On larger boats with higher forces B&Q's thinnest blind cord works a treat, but a 65cm boat won't get that far.

The starting point for rigging is just to make sure that that with the mast vertical the sails sit nicely with a straight leading edge and the other two sides having a gentle curve, and no wrinkles between. Worry about the other stuff later. Tuning can't happen until you can see what needs tuning, and that is a function of the first sailing.

Thread: Another stupid question, for those who know
02/04/2021 15:51:09

If by IOM type you mean a bare looking racing type boat, then near enough but you don't want IOM size recommendations for a 65cm yacht, which is very much in RG65/DF65 territory.

For this size, especially if the hull build is heavy, 4 or 5 AAA size rechargeable cells will do the job. Highest capacity you can find in that size pack.

https://www.componentshop.co.uk/6v-aaa-950mah-flat-battery-pack-low-self-discharge-type.html

Looks about right, or the 4 cell version.

Sail servos. There have been many yacht designs that tout their ability to use a standard servo to operate the sail. I have yet to find one that works in wind strong enough to power the boat unless it is sailed very sympathetically. Component shop and others do servo size sail winches with varying degrees of travel. Work out the difference in control line length (in inches) between full in and full out, divide by pi, and you know how many turns you need your 1" drum to turn. Higher torque arm servos do need good batteries and wiring.

An exception was the XL25/Akela from the late '80's, but that had a semi balanced swing rig not needing as much force to operate.

Rudder servo. DF65 use a small servo (can't remember the number off hand). In a home build you could use a standard one.

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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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