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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: 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.

Thread: Size of a typical mast
02/04/2021 15:18:20

If going for carbon tube, here is a pointer from the DF65 rules -

G.3 Mast Construction To avoid the mast tubes splitting it is permitted, and recommended, to glue in the Mast Top Plug and glue the mast section joints. Boats supplied from 2015 onwards come with metal mast and jib boom bands to reinforce the tube ends. These rings are available as accessories and may be used on older boats.

Taken from -

https://dfracingdotworld.files.wordpress.com/2017/03/dragonforce-65-restricted-class-rules-v1-61.pdf

The inference is that carbon fibre tube, while incredibly strong and stiff, is inclined to split at the ends, and needs a bit of help.

Thread: Rigging
31/03/2021 09:27:53

Local club if available. Not seeing them at your local lake doesn't mean they are not there - their sailing times might not coincide with your visit times. When chatting with passers by ay my lake I often get told that they didn't know such things happened, because they had never seen it in 30 or 40 years. I've been playing boats there for 30 years.

Alternatively, sites like this or one of the many others with like, or more focussed, interests. I did a lot of learning reading racing reports (and looking at the pictures) in model boat magazines. What works for a top racer is good enough for casual sailers like me.

Catalogs give a lot of information, even if some of it is unintentional. You spot names of parts which need a web search for an explanation, but its all part of the journey along the learning curve.

Thread: What material is used to make yacht Sails.
30/03/2021 10:57:27

A word with one of the model boat sail makers, Nylet, HouseMartin, Sails etc, PJ, and no doubt others, will show that they already do suitable sails for your boat. They will cost rather more than DIY sails, but they will be better made and have a better chance of working as required.

Material? Take your pick. Poly cotton from a dead shirt, bin liners, shower curtains, florists cellophane, drafting film, rip stop nylon, all have been used successfully.

Thread: Size of a typical mast
30/03/2021 10:39:40

What Ray said.

Just measured the mast on my Victoria, a slightly bigger yacht. 9mm diameter, aluminium tube. So 6mm carbon would sound OK. Although tube might be preferable. Competing or not, you still want the boat to behave well in a range of conditions, racing boats do this and it is a good idea to grab as many of their tricks as is feasible.

And, when another yacht appears, a race is going on.

Thread: Modav Huntsman 34? fittings
24/03/2021 10:30:29

In the model boat world, many fittings go by size rather than scale since in the real world, larger fittings follow the same design.

1:11 is a very odd scale, probably determined by something that the designer had available. More common scales are 1:12 (1 inch to the foot) or 1:10 (handily metric). The difference for fittings either way is probably small enough that nobody will notice. Smaller scale fittings usually fit better, more room to position them easily.

Thread: Bending 5mm brass rods to make driveshaft
24/03/2021 10:23:47

If the original used 5mm brass, fair enough. I would be tempted to look at stainless bike spokes. About 2mm diameter, much easier to get a 90 degree bend in, probably as durable as 5mm brass. They come in packs of 10, but unused ones tend to find uses very easily.

Thread: Mixing paint
20/03/2021 10:51:57

Nearest match to a shop-bought tin any time. The only exception to that was back when Humbrol were ruining their reputation having out sourced to foreign parts where it seems that the paint mixing department was using the local colour blind. It's taken them a long time to live that down.

Using a catalogue colour gives a much better chance of getting a later match when the inevitable touching in is needed after a bit of real life weathering.

Oil based varnishes tend to oxidise over time, which causes them to gain colour, usually yellow-ish. Acrylics don't.

Thread: kms bismark
16/03/2021 09:53:38

Finally found a datasheet for A4988.

https://www.pololu.com/file/0J450/a4988_DMOS_microstepping_driver_with_translator.pdf

Still having trouble seeing the need for an 18 volt supply, given that the A4988 uses a load supply voltage down to 8 from a max of 35, and the stepper that it is driving rates at 12volts.

15/03/2021 10:24:02

A link to a datasheet for the chosen circuit would be useful. A good data sheet can answer many questions, and might highlight some otherwise unforseen problems.

The few that I have seen for stepper controllers all indicate a need for cooling, either a heatsink or a fan or both. Stepper motors do have a reputation for speed and precision, but at the cost of being very thirsty for the work done, hence the need for cooling. Possibly the reason for the need for cooling. Not an issue with devices with external power (i'e; running of the mains) but definitely an issue in self powered portable equipment.

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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.

In order to maintain a consistent standard and format, all suggestions should first be sent to me by Personal Message for approval in principle. Only a very limited amount of time is available for editing contributions into a suitable format for placing on the website so it is important that the material is well presented, lucid and free from obvious spelling errors. I think it goes without saying that contributions should be illustrated by appropriate photos. I shall be happy to give advice on this.

The Member Contribution area offers space for short informative mini articles which would not normally find a place in Model Boats magazine. It is an opportunity for Website Members to freely share their  expertise and experience but I am afraid that virtue is its own reward as there is no budget to offer more material recompense!

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