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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: Todays Boating
27/07/2021 21:58:34

All my sellotape (which might be the real thing or just what the shop was selling) is fairly elderly, being the remains of a 5 pack of rolls about 4" diameter, a new one being broached every time the current one vanishes into its hiding place. But perhaps not that elderly as to be a porous variety.

Duck/duct/gaffer tape does a great job of aggressively sticking, but is a pig to remove should that be needed. The plastic comes away leaving a woven mess that really wants to stay where it is. It was waterproof enough for the Mythbusters to skin a boat with it and sail around in one episode. Mind, they also "proved" that a home design of personal flying machine couldn't work. Whether it was they who decided it should be built from scaffolding poles or the original plan was never made clear.

27/07/2021 15:16:33

I'm surprised about the sellotape comment.

For some time past I have given my packs a covering of the stuff when doing repairs brought about by relying on the manufactures shrink sleeve.

Provided it is laid on with care (no fingerprints on the sticky side) on a clean dry surface and no unexpected gaps left, I have yet to have one come apart in use. Perhaps early learning by applying handlebar tape on my bike helped with the technique, but on an awkward shape like a 5 cell humped AA pack, I aim for two layers using a spiral layout pattern and usually end up with three or four, which is still thinner than heatshrink. The basic trick is to have a long flat start and finish while ensuring that the pack lead has adequate support where it leaves. Important words are "clean" and "dry". As anybody who has ever tried to start pulling sellotape off the roll without a tab (like when the cut end has been allowed to settle itself without a folded-over bit) it sticks to itself amazingly well.

I would consider using coloured electricians tape, but I haven't seen any that has decent adhesive properties commercially. OTOH, sellotape is easily come by, and cheap.

Thread: Bristol Channel Pilot Cutter
23/07/2021 10:08:52

On the real thing, if an auxiliary motor was fitted, there was no requirement to have the prop on the center line. Fitting was considerably easier if not trying to arrange a hole up the backbone of the vessel.

That snippet from "Topsail and Battle Axe" - a good read for anybody interested in Bristol Channel cutters, if it can be got. I had mine from my local library, back when local libraries were still around.

Thread: Toggle switches for RC sets
20/07/2021 15:49:44

3 contacts makes for a single pole switching between two outlets. The difference between the two is that one is mechanically arranged to have two positions, the other, three.

Thread: Glueing wood to polystyrene ?
15/07/2021 09:30:42

Gluing wood to moulded or sheet polystyrene, epoxy. For expanded polystyrene, as suggested previously.

Thread: 18650 batts in model boats
13/07/2021 09:06:47
Posted by phill downes on 12/07/2021 21:01:34:

thats the first ive heard that 18650 can be Nimh.

I know the batteries will be coming from a top of the line scooter and thats all I know so far.

I do know the scooter had a range of about 30 miles or more..

once I grab them I will take some pics to see what they are....

It came as a surprise to me when I read the label properly, but there it was.

A goggle this morning for "18635 NiMH" did its best to show everything but that, but near the bottom of the first page was -

https://www.batteriesplus.co.uk/acatalog/18650_Size_NiMH_Battery.html

Not common, but they are out there. Twice the AH figure of a typical Lithium cell, but only 1/3 the voltage, so I suppose that in the same space Lithium stores about 50% more power, but with a different delivery profile.

12/07/2021 09:48:00

It helps to know what is inside any particular cell. If it has no label, its probably a recycle item unless it came from a known pack with a label or you can do some cautious testing.. 18650's are not limited to lithium, some are NiMH chemistry, with voltage to match. Being about twice the volume of an AA, they have about twice the capability. Potentially, anyway.

11/07/2021 17:15:03

In the model boat world, even if NiCad are available, since NiMH with better numbers at lower prices are so readily available, why go that way? For most of us, NiMH is a direct drop in replacement for NiCad, and, in packs, without the "memory" of myth and legend.

11/07/2021 09:53:32

One of my members, as part of his business, winds up with lots of laptop battery packs that have ceased to be workers. He strips them down, checks the cells (which are invariably 18650s) and uses the good ones to build packs to power his boats. Cruisers rather than screamers, but having roughly the same power demands placed on them as they had in their native laptops, they work very well. And, of course, to him they are free.

To drive his hooligan boats he does pay real money for proper batteries.

Thread: Expanding foam
11/07/2021 09:43:10

Apart from its knack of absorbing water, either from contact with liquid or just getting it from damp air (and boats operate in damp conditions), most users use far too much, not really allowing for it expending as much as it can.

Expanded polystyrene packing or similar, hacked to shape works well. Or similar packing noodles. Or, if you can forego the joy of popping them, bubble wrap sheets.

I imagine that the last thing wanted in a buoyancy chamber is soggy ballast that cannot be extracted and/or dried.

Thread: JIF 65
06/07/2021 09:59:03

The shroud is plastic. You are a modeller. You possess a drill. You can arrange your hole or holes anywhere that you want them. Plug it in and try it with your radio - observe which way it rotates for "in" and "out"

The friction rubbing the line against the plastic is not a real worry. A smooth line will go round the corner easily - a rough line will reshape the hole to its own satisfaction. I prefer my line to go straight to a fairlead after leaving the shroud - the tension line above deck should ensure that the line pulls out in light airs, but it is a good idea to avoid any possible chance of stray slack line below the deck. It has a distressing habit of finding anything it shouldn't and self tying a knot. If that knot happens to be around the power switch, it is annoying. The line just needs to be thick enough so that there is room on the drum to hold the appropriate number of turns comfortably - too thin a line "might" try to escape between shroud and drum.

The shroud is very good at preventing a slack line from hopping off the drum and doing evil. However, a very light, flexible line, in light air conditions, is effectively being pushed at the hole. It can try to form a "tidy tangle" inside the shroud. A gust of wind will usually pull this out, or it might need a bit of experimental winding in and out to lose the tangle.

In practice, I haven't needed to use the screws provided to hold the shroud in place. The drum and its fixing screw does that job admirably. The locating stubs just make it face the "right" way when mounted to the top of the winch body, but other than providing nuisance value for later on, can be ignored.

Modellers tend to like complications - manufacturers are happy to oblige them, but sometimes you can bypass complications that are simply not needed. Just a question of spotting them.

03/07/2021 09:19:17

If you go the LiPo route, no more than 2S. That is the maximum that easily (and cheaply) available servos can handle, and even that would probably be better (safer, longer lasting) fitted with a UBEC to bring the voltage to something that is universally accepted. Regulating down from a higher figure just means that you are carrying more battery than is needed with no real benefit. While UBECs are efficient, they are not THAT efficient.

From my days of collecting and reading data sheets for ICs, 7.5 volts was a common figure for the maximum voltage on chips used in the modelling world. Anybody running such chips above that was relying on a combination of dumb luck, and, in the case of flyboys, lots or air flow providing cooling. A freshly charged LiPo can exceed 8.4 volts - I have seen some that claim 8.4 on the label.

02/07/2021 09:47:11

Almost everything on a model has more than one job, especially the rigging. The primary job of most of it is to stop the mast falling over.

The backstay stops it falling forward in a following wind, but also, when correctly tensioned, affects the shape of the mast and the sails attached to it.

The side stays, if used, keep it upright in a side wind and help keep the mast rigid. Also very useful when launching and retrieving as you can lift the boat by the mast, letting it dangle easily (holding by the mast like it was a frying pan is not recommended). With a deck stepped mast, they also transmit all of the forces from the sails through the hull on their way to the fin, which is shoving the other way.

Some boats have a fore stay, which stops the mast falling backwards. Many (racing types where there isn't room for a forestay) use the fore sail and its associated lines to do the job. There is a line running down the leading edge of the sail (which is tensioned to this support line) to the front end of the boom, the boom itself, and a swivel or bit of line from a point on the boom to the deck. Some get a leech line, which starts somewhere near the top of the sail and goes to the rear end of the boom. This completes the triangle and allows the fore sail to be properly shaped without being unduly tensioned.

My version of keel stepping doesn't allow for adjustment, if I need to alter things to get a better balance, I need to do something radicle with sails. A deck plate allows for adjustment.

A gram saved at the upper end of the mast is ounce saved down below, since the weight down at the bottom doesn't have to counterbalance as much weight at the top to provide the righting moment. Since both DF65 and JIF are intended to conform to the same racing rules, there will not be huge differences between the two sets of sails, and, being of very similar area, will generate very similar forces. Of course, cut, shape and material will make differences, as will their eventual fitting and adjustment.

Thread: 2021 Builds during lockdowns
30/06/2021 09:46:23

Just guessing, but I have a feeling that the original builder had some misconceptions about rigging a yacht which might have contributed to the abandonment of the project. Some closer pictures of the sails might help confirm or deny.

As a general rule, the leading edge should be arranged to be straight, the trailing edge left to find its shape. On most swing rigs the fore sail has its own boom rather than being loose footed, and, just like any other yacht, there is a "slot" between the trailing edge of the fore and the mast.

Thread: Todays Boating
27/06/2021 09:32:39

Way back when I was incarcerated in a control office I asked one of my merry men what it was like on the moors above Littleborough. He said, and I quote, "Still snowing from last year".

26/06/2021 20:23:35
Posted by Paul T on 26/06/2021 17:52:26:

Ashley

The weather is getting bad in your area, watch out for storms and icebergs coming in from the Heron Lake.

Meanwhile it so hot up here int north that the cobbles on the M6 are cracking

Paul

Surely you mean the M62 where patrons of the highway are allowed to avoid both Oldham and Rochdale in one go?

Thread: JIF 65
25/06/2021 10:07:11

My thoughts are turning to servos, I will use a drum drive as the arm alternative causes the thread to move through a linear quadrant or arc (whatever), with variable torque to the rudder arm. I can now see that the drum has the thread moving along a constant path, the torque applied is consistent and finally I can keep the hole through which it passes quite small. Still do not know what brands are wort considering, or how powerful a servo is needed for the rudder.

Do some measuring. Determine the distance from the boom connection point to the deck connection point both when fully "in" and "out". The difference is the needed travel. The drum is approx 1" diameter, 3 and a bit inches per turn. A 2 turn winch will do the job, DF65 uses , I believe, a 1.5 turn winch. A bit of extra travel lets you be a bit sloppier in line layout. I prefer winches for their simplicity in installation in a confined space, but an arc, properly arranged and with a sufficiently high torque servo, uses the variable torque to advantage. Probably the King Max 2 turn metal geared one.

For the rudder link, swinging the rod through an arc is no problem - just make the hole oval. The speed lads use rubber bellows to cover the hole. Simple, cheap, works. Rudder servo? Look in the DF65, observe the mini servo, get a similar one with metal gears.

Given that the boating lake near here is saltwater, I am not at all sure that Brass is the best, nor is the steel, chrome plated any better. I would use Stainless steel, also knowing that this is prone to Chloride attack. I guess that a good wash down is needed for all the options.

Brass. As simple as that. Stainless steel if that is needed for strength. Chrome plated steel is a disaster in a hurry to happen, chromed brass or stainless, OK. Lacquer is good.

None of my boats have ever used a deck plate for the mast. Wherever possible, they are keel stepped and sit in a brass tube that goes from deck to keel (meaning hull bottom in this case, not the lump on the end of the fin) and is an integral part of the rigidity of the whole thing under load, avoiding putting any undue stress on the hull structure.

A bit of extra weight in the rudder will probably be offset by the weight of water that it displaces, but a lightweight rudder "might" provide a bit of buoyancy at the stern, which might be a factor in the performance of the original.  Having a rudder that is not quite as strong as its mount is no bad thing.  Careful handling is no bad thing, but a broken rudder is much easier to fix than a broken hull.

Edited By Malcolm Frary on 25/06/2021 10:10:22

Thread: Suppressors when using 2.4gHz?
15/06/2021 14:59:28

As a brushed motor rotates, each brush shorts out one of the windings as it passes from one segment of the commutator to the next. All of the energy stored in that bit of the armature wants to go somewhere, and that puts a lot of current through the bit of brush doing the shorting. The suddenly changing field that this causes also appears as stray voltage spikes at the motor terminals which send current p the motor leads. It is this current that generates the interfering signal rather than the spark itself, the spark is a visible thing that indicates that something is happening.

Bits of muck and uneven-ness on the commutator allow the sparking to continue for more of the rotation time, thus a tired motor (or one that was designed tired) generates more interference.

Thread: Which prop shaft
15/06/2021 09:20:46

Probably the project in his other thread.

Thread: What's the foresail on a cutter-rigged ketch called?
14/06/2021 16:16:57

Spotted on https://www.sailboat-cruising.com/cutter-rig-sailboat.html - it "might" be what the writer on there referred to as a "Yankee". This might mean that that particular sail has different names in every area where it is used.

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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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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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