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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: Old sailing vessel, need help identifying type, rig, scale etc.
04/09/2021 20:21:01

While it might be beamy for a particular clipper, there might be some useful stuff here -

http://mcjazz.f2s.com/ClipperShipPlans.htm

In all probability, there was a 3rd mast. Also a considerable bowsprit. The rudder would have been a tall, narrow and with parallel sides. Not really used for steering as much as for trimming direction once that had been determined by use of the sails after much shouting by the sail master and a lot of sweating by the crew. This aspect of the days of sail rarely makes it to the movies.

Thread: Names
22/08/2021 22:01:30

When making printed circuits, the "etch resist" is basically paint. The etching solution is formulated to attack metal, usually copper, but it likes brass as well, but paint isn't metal, so is let alone by the etch solution. The result being a lower surface where the paint (resist) wasn't.

Whatever Letraset is made of might have the required properties.

As long as the surface is lowered by more than the thickness of a coat of paint, painting and abrading the surface should, in theory, leave brass letters on a coloured background.

I have usually cheated by making a vinyl sticker using a colour laser printer, but then, I keep my standards in check.

Thread: Lubricant
20/08/2021 10:00:09

Metal rubbing or thumping metal, lubrication has always been a good idea. Metal to metal gear teeth, definitely lube. Metal to plastic, less so. Any atmospheric muck will incorporate into the lube and be thumped by the metal gear teeth into the plastic teeth.

Plastic gears have been touted as self lubricating, but that depends on the plastic involved. Bearings are another thing again.

The gearbox on top of a servo has lots of gears and usually a smear of grease, but I suspect that that is there more for the rubbing faces of gears against each other in a pile, and bearing surfaces, rather than the teeth, and that space is generally clean and sealed.

E&OE

Thread: Returning modeller
07/08/2021 08:50:52

Using the 50" length as the main clue, I'd say it's a Marblehead of some type. What particular design within that class, no idea. Maximum mast height is 85", but there is nothing to stop shorter rigs being used as long as the sail area measures at 800 square inches or less.

Since it has a registration number, the MYA might be able to fill in a bit of history.

Edited By Malcolm Frary on 07/08/2021 08:53:20

Thread: LCT Front Ramp
06/08/2021 08:46:31

A HS-785HB is just an ordinary servo with more travel. Instead of 90 degrees of travel, it does 1260 degrees (3 1/2 turns) with a typical transmitter on a proportional channel. Depending on the particular transmitter.

Plug it into a switched channel and see how many turns you get between one switch position and the other. Once you know that plus knowing the diameter of the drum, you know the travel available. After that, its just a case of working out the best arrangements for the string, matching the travel you have with the travel required for raising and lowering the ramp. And stopping when you get there. With a 1" diameter drum, thats about 11" of travel, but the settings on the switched channel might be different.

Thread: Returning modeller
29/07/2021 20:24:48

With a 2 channel set, if differential steering is wanted, yes, two ESCs and a mixer. Choice of 1 battery or two is dependant on whether the one battery can supply the demands of two motors.

If differential steering is not needed, then one ESC "can" work both motors if it is rated for the motors used. The battery needs to be rated for the job as well. Or, one ESC per motor plugged into one channel using a Y lead. Number of batteries becomes optional, although one per ESC is probably the simplest option.

There are plenty of 4 channel outfits available, shopping for a "best buy" is a fraught business since unlike 27/40MHz, there is little compatibility between makes, although at the lower end of the market HobbyKing/Turnigy/Flysky receivers work with the other transmitters and replacements cost about the same as a pair of crystals used to cost.

Thread: JIF 65
29/07/2021 20:04:12

When designing a small Bowsie, you find that you need several holes in a small piece of fairly strong plastic with preferably no corners. When finished, the immediate thought is "This looks like a shirt button." Most shirt buttons are two hole, but there is room for another. Whenever a shirt gets beyond further use, it presents a collection of potential bowsies.

When you have gone through enough servos, you wind up with a stock of spare servo horns. The arms of these are usually strong plastic, with a row of conveniently sized holes.

The boom vang just needs to be a line with a bowsie to adjust to taste, unless you really want to create a further maintenance task by introducing adjustable metalwork to expose to a salty environment.

The elastic is a necessary evil to ensure that the line at the drum is never allowed any slack, when it will fall off and tie itself round the underside of the drum (if an open type) or allow itself to push into a lump inside the shroud. A visit to a haberdasherer will find "Shirring Elastic". Various weights, not everlasting, but 75 metres lasts a long time. As do a packet of fairly light elastic bands from most stationery shops. Oddly, thinner elastic bands have a better stretch ratio which is good for operation. Their relatively short life is made up for by the fact that a 30" boat uses 4 or 5, and a pack of 100 cost £1.

Good pulleys look nice, but anything with a bit of a radius does a very adequate job of turning a line. There is probably some rule of thumb giving the minimum diameter of the turning point, probably something like "at least three times the line diameter". My Victoria originals were a plastic "bead" in the stern panel, but when much use had caused the line to saw its way in, converting the hole into a slot, I replaced the bead with a stainless self tapper with a cover to stop the line hopping off when slack.

28/07/2021 10:46:26

Assuming that the wood that they are screwed into can stand the forces, if the maths are done diligently, the difference will be a miniscule, going on totally insignificant, fraction of the total. Just go for what you find pleasing to the eye.

A side stay will be trying to pull the eye out by its roots, and will exert very little sideways force. The main force will be between the threads and the wood that they are sitting in.

If being used as turning points for running rigging, 2mm or so of brass will be more than adequate for whatever your sail rig can offer. If they are brass plated steel (stronger), a rethink may be required if salt water is ever involved -steel + salt = rust, think "any BL car". The plating doesn't last outdoors.

Servo testers. Unless one of the fancier types that tells you actual pulse lengths on a screen is used, the rotating knob just lets you swing the servo as far as either the servo can go, or as far as the tester can go, whichever end point comes first. The cheap basic types like mine are good for basic checks without involving a radio, but come without any calibration.

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.

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