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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: Returning modeller
24/09/2020 22:09:22

The important rule is that anything that passes power on should be shrouded and will probably be the receptical, any connection that collects power will be a blade. Same as domestic wiring - you dont want to be waving live power around where it can do harm. It doesn't matter whether it is the positive or negative side - it is whether voltage is being presented or collected.

Thread: ESC ratings for brushed motors.
11/09/2020 09:27:46

The nce thing about brushed motors is that you don't need an ESC to check what current they take. Just get a bag of assorted fuses and connect them to the battery under load. Take the lowest value fuse that doesn't blow, pick an ESC of a higher current rating (preferably start at fuse + 50%) and it will work. If using a meter to check the current, start at 50% more than the reading.

Thread: Controlling bow thruster and propulsion motor
09/09/2020 21:45:31

What Dave said. The BECs in the ESCs power the internal parts of their ESC and, via the red wire, the receiver and anything plugged into the receiver. Two BECs into one power rail might not play nice, so disconnect one.

Both small switches will need to be "ON" for the circuits to work, but both need to be "OFF" when the system is powered down if the battery remains connected. A good idea is to mount them both together so that you can see that both are off. I've been caught by a black switch hiding in a dark recess resulting in a mysteriously flat battery before.

Thread: Hobby Engine “Richardson” tug boat upgrade
07/09/2020 14:42:37

Probably one or two more screws hiding under deck fittings.

If hunting on tinterweb, it might also be known as "Southampton". Probably a few rebuilds around, hopefully by people who have found the hidden screws.

If only the sailboat crowd see your query and ignore it, it might be better posting in a more general area like "all things..." or "beginners".

Thread: Returning modeller
02/09/2020 09:43:43

If a 10A fuse is being blown on a regular basis, it probably means that more current is being drawn than the 15A ESC can safely handle. A lower rating is needed for a fuse than the ESC involved because fuses are not instant acting. The length of high current time that it takes for a fuse to blow can be critical for the electronic bits involved. The answer is either a less demanding load on the motor (less prop diameter, typically) that will demand less current and/or a meatier ESC that can handle what is demanded.

A down and dirty method of figuring what ESC current rating is needed is to do empirical tests using fuses instead of an ESC. Fire it up under load (i.e. prop in water) and figure out the lowest value fuse that doesn't blow. Or use a meter to get the actual number, but most multimeters stop at 10A. Multiply that by 1.5, look for the next rating ESC above that figure. Avoid ESCs that claim 320A and don't have a recognised makers brand name.

Thread: Motors/prop for model warship
01/09/2020 21:47:05

The much quoted rule of thumb for sussing out a combination of motor and prop is "motor can no less than prop diameter, prop should have fewer blades than the motor has poles." Not scientific, but it works. Having the precise definition of a brushless motor is great if what is actually wanted, or needed, is known.

A very common question that crops up is "Why is my motor too hot to touch after only a few minutes?" The answer is always "There is too much prop". If going for a 360, go for a smaller prop with fewer blades. A 385 with a 30mm 3 blade prop works well and will not melt the solder off the terminals (yes, seen it done)

Most of the 385s that turn up in model shops say 6-15 volts on the label, running one on half to 3/4 the max gives the right performance for a surprising range of models.

31/08/2020 11:14:56

The main reason that the one I mentioned earlier wound up shorter was the free wood panel size. The reason for it being that bit deeper was that in that magazine issue there were two plans. One for a retro Bowman look-alike launch, the other the Quickstep.

I started on the launch and decided that I would rapidly get bored with it. A bit of pencil work, a few bits missed off and there was a slightly shorter, wider and deeper "frigate". It got called "Troutbridge". Despite the lack of any actual prototype, it didn't stop the occasional passer by claiming to have served on one, or something very similar. At least, until they got a close view. They were all polite enough to not mention the missing rack of torpedo tubes.

A boat this size will work well with a 385 on around 3/4 the volts it says on its label. A much smaller 280 will be working far too hard. A longer shaft lets you position the inboard end higher, hopefully above the water line, while keeping the angle shallow.

30/08/2020 09:05:02

My first go at building from a plan was HMS Quickstep, probably a GG plan. A few changes were made as it was built from ply panels recovered from a dead kitchen door. It ened up a bit shorter (missed out a set of torpedo tubes) and a bit deeper (about 1/2" which heped stability and payload. The ply probably helped make it strong enough to minimise bank damage.

With a free running boat, you don't get to choose which bit of bank its going to slam into. You have to guess and get there first. Remote steering helps. Getting a speed control as well was a revelation.

Thread: Action P44 Twinlatch switcher
24/08/2020 08:59:40

Small relays can operate big relays, but its all extra weight and volume and complexity - extra battery or bigger battery is better. More run time plus less chance of it not working when needed.

Thread: Smoke unit
23/08/2020 17:09:51

Everybody would like a smoke unit that gives black smoke. Nodody makes one. Given that generally the black particles that smoke comprises are usually considered carcinogens, nodody is likely to.

Thread: Action P44 Twinlatch switcher
23/08/2020 17:01:10

Any switcher with heavy enough contacts can be arranged to do the job, but Tim's answer is the simple one that works.

Relays with contacts that can carry the full battery load tend to be thirsty when operated, and will tend to negate any benefit. Switching to a smaller capacity reserve battery to get you back "might" be viable, but really it is simpler to notice that performance has drooped a bit and bring it in. Having a switchable reserve is probably a temptation too far.

Edited By Malcolm Frary on 23/08/2020 17:04:44

Thread: Ship Repair
21/08/2020 19:21:54

Some shops sell mast and spar replacement parts but they mis-label them as "chopsticks" or "kebab skewers".

I expect they think that the exotic eating market is bigger than that for model boat parts.

Thread: Best Servos
21/08/2020 19:13:28

Over the years, there has been several changes inside my first Victoria (for comparison, about 400 sq in, weighs 5 lb, 30" long).

As bought second hand it was fitted with a standard servo, the manufacturer claiming it could be worked by one. As I found, it would only pull the sails in if there was so little wind that it wouldn't go. Probably why it found its way onto the CADMA bring n buy.

A "High Torque" servo from Howes worked great. Enough force, in light wind, to have the slack find the slide switch and switch the thing off. A radio boat that is now self steering on a large lake with shifting winds generates plenty of exercise. Thinking to figure out whwere its going, walking to get there, more thinking when the different wind close to the bank causes it to take avoiding action.

Over a few years, it did slowly bust its mounting box causing a rethink.

Small winches at a sensible price appeared (King Max)

A Victoria wants the travel that a 2-turn offers. 400 square inches is a bit too much for a 2-turn winch. A 4-turn required a bit of re-rigging, the winch line getting a doubler with a running block (or shirt button, as some call it) on the after deck to lose the excess travel and increase the available torque at the cost of speed. After a bit of a shuffle round of winches and models, it got a 6-turn. Same basic doubler, but the geometry of the deck bridle and boom fitting soaked up the extra.

Whether arm or single ended drum, a tension line is needed to keep the line being let out tidy. On a 30" boat, 5 or 6 of the elastic bands that come with bunches of spring onions do nicely, or you can go to a sewing shoppe and get an approprite weight of shirring elastic.

These small winches are superb mechanically, but to fit everything into a standard servo case, the electornics is maybe too tightly packed for its own good. This should not be a problem with larger winches.

Thats 11 years of sailing it like a hooligan.

Thread: Ship Repair
20/08/2020 22:38:35

As Roger suggests, a slightly oversize hole up each part and an internal splint epoxied in place. Since it is decorative rather than working, a piece of toothpick rather than a metal peg would do.

If it wasn't so prominent, a bit of clear heatshrink might do the job, possibly forming a  sleeve over Colin's superglue butt join.  If the ends are jaggy enough, the butt join could well be enough by itself.

Edited By Malcolm Frary on 20/08/2020 22:44:34

Thread: Boat?
18/08/2020 21:55:46

Slec (one of the advertisers on this page) have a range of cabin cruisers. Depending, some should be large enough to fit out easily and use in a range of conditions while not being too intimidating as a project. Sadly, cabin cruisers lack sails.

Edited By Malcolm Frary on 18/08/2020 21:56:29

18/08/2020 21:55:17

Slec (one of the adverisers on this page) have a range of cabin cruisers. Depending, some should be large enough to fit our easily and use in a range of conditions while not being too intimidating as a project. Sadly, cabin cruisers lack sails.

Thread: Best Servos
18/08/2020 21:47:00

8 turns seems a lot. Much more usual is 3.5 turns. Most normal servos turn 1/3 of the travel of the pot on the inside, standard pots have a 270 degree track, so 90 degrees. To do a winch, the easy way was to use a "10 turn pot", 1/3 of that gave 3 and a bit turns, which was handy. With a normal transmitter, 3-and-a-bit might be it.

Measure from the chosen spot on the boom to the chosen rigging point on the deck with the boom full in, and again, full out. Subtract one from the other, if its a 1" drum, (3 and a bit inches per turn) you can work out how many turns. If it isnt too far out, jiggling the chosen points about can get the length the boom wants to fit what the winch will offer. Then try to do the same with the other sail.

At that price, it would have been rude not to get two. Maybe even churlish.

18/08/2020 10:09:08

When picking a sail winch, apart from being able to fit it in the space available, you need to know the sail area and how much string is going to be pulled in. Some just throw the string on and fiddle with the electronics to get it right. It is much better to figure out the travel and tweak the layout of the string first.

Winches usually have a 1" diameter drum, so it is possible to work out the travel that a winch of however many turns will give. Arranging the running rigging (position on the boom, position on the deck) can make quite large differences, allowing you to trade speed and torque.

Arm winches do need a really strong mount to withstand the twisting that they generate - a drum just gives a straight pull. An arm is less likely to create a tangle, but is not immune from the problem. I have had one loop a loose line round the radio switch and switch it off. Amnnoying.

If the sails turn out somewhere in the 6-800 square inch range, anything that is good for an IOM will be fine.

Thread: Boat?
17/08/2020 09:21:19

Ever since it appeared a long time ago, the 1:72 Revell Snowberry corvette has been a good starter, especially for those with some previous modelling skill. Mostly just a bunch of new words to learn.

Fairly easy conversion to radio, big enough to get both hands in, small enough to carry to the pond, enough performance to look good, low enough performance to be forgiving.

Thread: Best Servos
17/08/2020 08:59:42

Is this for the pond yacht? Knowing the size of the boat and its sail area helps a lot, along with the intended travel from full in to full out.

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