Where did you obtain the hull and or plans?? I would like to biuld a Sarinda as well!

Well, after reading this thread I ordered a couple of kingmodel ESCs, have just bench tested with the BYMS. Did find out I’d forgotten to grease the prop shafts so once I’d worked out a fix to reach the grease nipples with the deck in place the bench test was a success.

The BYMS has twin MFA 385 motors so the 20 Amp ESC with blend may be over the top but it works fine. Good value for £6.11

Thanks Roy
All now purchased.

Hi Steve I went on the site you mentioned and saw the esc's but they were about £7-£8 each.
I bought mine last time at 5 units £14 free postage. < £3 each including postage.

They are still there at around that price. I buy about 5 at a time, they quote 10 amps and even 20 amps but I am content at 2 - 3 amps but always check the spec for i/p voltage.
Roy

Hi yes I use JST red wires.
A quick look found this advert on ebay. You will need minimum 2 pairs but you might also want to make a Tamiya / JST adapter.
Below link shows 5 pairs and free postage at about 70p per pair.
Good luck
Roy

https://www.ebay.co.uk/itm/262719964389?hash=item3d2b5484e5:g:j8wAAOSwU95avM21

Question for Roy.
In an earlier post you suggested the Kingmodel ESC/mixer which I have now bought. Have to say it looks really nice.

I think you were saying you bought the matching connectors/wire for the battery and motors. I have searched through the Kingmodel listing but cannot find them.
Could you please suggest a link?

Good evening everyone.

I read the word "mathematics" and then I got curious.

I wanted to reread a message that I hadn't given particular weight to because I hadn't fully understood its meaning and it seemed off topic, perhaps even useless.
However, I thought I had misinterpreted the content.

But is it "mathematics" with a capital "M" or mathematics with a lowercase "m"? Ahahahahaha!

My tone is joking, please don't let anyone take it badly, but I want to be precise.

I reread it and asked myself: "isn't he really commenting on the contents of an electronic item sold on Aliexpress?"
"Aren't you really commenting on the fact that some data provided by sellers on Aliexpress is not very reliable?"

Yet the more I read it, the more I realized that there was no other explanation.

Do we really evoke the word "mathematics" to comment on the section of electrical cables based on current absorption?

Is there a need for special calculations for quite obvious things?
Anyone will have seen, inside a car, the section of the cables and the value of the fuses, anyone will have made a comparison and realized that for 320 amp. (in DC supplied continuously) much larger sections would be needed.
What a sensational find!
Anyone will have seen a table with the cable sections in mm2 or AWG and the related electrical currents.
Are we talking about this exactly?
But even before the cable sections, the connectors are already giving the warnings. The Tamiya connector reaches a certain current capacity then other types of connectors are needed.

In the last two messages I explained twice why I included those links. This alone, in my opinion, should be enough.
Repetita juvant:
I expressed my opinions (certainly questionable) on brushed motors, ESC and more.
Once the choice was based on Roy's advice (which I share) I expressed my personal opinion (this is also debatable) on the casings of electronic devices in general and I showed what I meant with the images of the links.

However, at that price, I would still buy those ESCs if I needed them, even if they don't meet the specifications declared by the seller in the slightest.
The wires are large enough for the currents that I measure or estimate are actually flowing in a specific situation (certainly not 300 amps, it makes me laugh just thinking about it).
In any case that section would be protected by the fuses that I use, based on their threshold.
The price is low and don't worry if they break.
Of course, it's not just the cables that have to withstand the passage of current, there are the tracks, the individual electronic components, etc. etc.
Will there also be a difference between an apparatus that costs 5 euros and a similar one that costs 150?
Furthermore, if you remember, my first (questionable) choice was for the Graupner Gra2880. There are less expensive and more expensive ones.

Well what can I say? If this had been the topic of the topic, perhaps I would have also wondered why sellers indicate these capacities in amperes.
Who knows if they refer to measurements of transient or peak passages or simply threw in a value at random.
This wasn't the issue.
Steve asked some pointed questions.
Some like Roy, RodC, Scotts, Terry have given precise indications with useful information content.
Instead, I can't understand what use it could be to say that Ebay has many types of engines for sale and a person can choose what he wants.

"
Whoa there... Did I miss something?

This is what the Chinese ESCs claim on the aliexpress site:
"RC Ship & Boat R/C Hobby 6-12V Brushed Motor Speed Controller ESC 320A
Special attention: this 320A ESC.
With 3S (12V), only motors not greater than 380 can be used.
With 2S (8.4v), only motors not greater than 540 can be brought.
Connecting a motor with more power will cause ESC to burn out.
Description When connected with motor, it is capable of supplying up to 320 Amps (forward) or 160Amps (backward) of continuous motor current. Its integrated Battery Eliminator Circuit (BEC) powers the receiver from the motor battery, with automatic cutoff of the motor power to preserve receiver power as the battery becomes depleted. It is small and powerful, which can be used for different type of ship or car."

Did I miss something in my electronics class? Those wires from the ESC are pretty small to handle 320amps "continuous".

Careful what you recommend.

Lew
Florida, USA "

No Lew, You did not miss anything... It is the NEW math....😁

Hi Lewz I have read those claims as well!
Like you I do not believe them.

These esc's are very small and work OK for me, 10 amps claimed, I find 4 amps works and I do not go higher.

By the way they have a switch on them for turning off the brake function and for the mixer turning off the mixer as well.
Smallest switches I have ever seen!

Regards
Roy

Hi Roy, I take note of that.
Good to know.
I can learn from experiences, like yours and that of other long-time modelers, in this forum.

No problems Alessandro, as it happens the circuit board is in shrink wrapped plastic, weighs a few grammes and just sits in the air in my boat.
Regards
Roy

Hi Roy.

I'm sure the setup you recommended to Steve is great.
I hope the text of the last message was not misunderstood, if so it is certainly my fault. I'll explain.

I wrote that the ESC you recommended is exceptional and very low cost. I would buy it too for an identical configuration.

The links were only as an example to make it clear which case I intend to contain the electronic circuit of the ESC.
But they concern possible ESCs, very cheap, that I could buy for some of my engines, not for Steve. Again, not for Steve.
I thought I wrote it clearly, if I wasn't clear it's definitely my fault.

You're right about currents and heating. To power the receiver and the rudder servo, I too measured very low currents years ago.
I blindly believe that your ESC hasn't even warmed up, I have no doubt about that.
I was just expressing my preference in general: I repeat it here: I prefer electronic devices contained in metal cases (even with fins) rather than electronic devices contained in heat-shrinkable sheath.
It's definitely an unjustified obsession of mine but I can't do anything about it.

In other words, in this last message, I have not given any purchasing advice to Steve who, moreover, I believe has already bought the ESC.

I made some observations about possible uses of the ESC that Steve bought, with heavier loads on the BEC, but they were certainly not critical of his purchase. Nothing about the configuration as it is.

Unfortunately I wasn't able to understand all the messages in this topic, some of them, although I tried, I just couldn't understand what they mean.

Whoa there... Did I miss something?

This is what the Chinese ESCs claim on the aliexpress site:
"RC Ship & Boat R/C Hobby 6-12V Brushed Motor Speed Controller ESC 320A
Special attention: this 320A ESC.
With 3S (12V), only motors not greater than 380 can be used.
With 2S (8.4v), only motors not greater than 540 can be brought.
Connecting a motor with more power will cause ESC to burn out.
Description When connected with motor, it is capable of supplying up to 320 Amps (forward) or 160Amps (backward) of continuous motor current. Its integrated Battery Eliminator Circuit (BEC) powers the receiver from the motor battery, with automatic cutoff of the motor power to preserve receiver power as the battery becomes depleted. It is small and powerful, which can be used for different type of ship or car."

Did I miss something in my electronics class? Those wires from the ESC are pretty small to handle 320amps "continuous".

Careful what you recommend.

Lew
Florida, USA

Hi Alessandro, I have used these esc's for several years now in 4 model boats. I have used one of them at 4 amps and they do not even get warm. So no heat sink needed.

regards
Roy

Hi Steve-d the boat you have in mind can use 9 gramme servos for the rudder. Less current used and as the BEC does not have to drive any esc's, so less current needed.

Regards
Roy

Hello everyone and in particular to those who participated in this interesting topic.

Roy's advice was precise and comprehensive (it helped me a lot too).
He found an exceptional ESC at a very low cost. I think less than this is impossible for a dual with built-in mixer.

If I may add something: if you decide to get the ESC that Roy told you about (it's really cheap for the features it has) take a good look at the maximum current of the built-in BEC.
I thought I read 5 Volt 500 mA on the photo.
As a maximum current it seems a little low to me.
Normally if you power only the receiver and the rudder servo with the BEC you should not exceed this threshold.
However, remember that if you add other loads to this BEC, perhaps in the future, you can risk damaging it.
A 500 mA fuse (cylinder) can be the solution for carrying out bench tests of any additional loads, even under stress.

Some ESCs allow you to choose the options that ROY described to you with small jumpers (some options also include the choice of battery type).

Aliexpress is really very competitive.
Following Roy's example, I saw on this Chinese site other ESCs for Brushed motors, both single and dual, with interesting features and very low prices.

It makes me want to buy one even if I don't need it.
In this case, however, I would opt for an ESC with a metal chassis, with "chubby" cables and equipped with fins for heat dispersion rather than those wrapped in the thermosheath.

Just as an example:
https://it.aliexpress.com/item/1005005505210877.html?spm=a2g0o.productlist.main.45.76fda4f3Yr80qp&algo_pvid=5ce76084-f011-4104-96c5-9eca14a5c0f3&algo_exp_id=5ce76084-f011 -4104-96c5-9eca14a5c0f3-22&pdp_npi=4 %40dis%21EUR%219.27%215.46%21%21%219.60%21%21%402103879316989533003923329e2f6b%2112000033341152525%21sea%21IT%21860224597%21&curP ageLogUid=5ggqLmYsi7GQ

https://it.aliexpress.com/item/32726923180.html?spm=a2g0o.productlist.main.63.76fda4f3Yr80qp&algo_pvid=5ce76084-f011-4104-96c5-9eca14a5c0f3&algo_exp_id=5ce76084-f011-4104 -96c5-9eca14a5c0f3-31&pdp_npi=4 %40dis%21EUR%215.31%215.31%21%21%215.50%21%21%402103879316989533003923329e2f6b%2110000000108761746%21sea%21IT%21860224597%21&curP ageLogUid=kmW9lmJTePp8

https://it.aliexpress.com/item/1005005595662048.html?spm=a2g0o.productlist.main.15.76fda4f3Yr80qp&algo_pvid=5ce76084-f011-4104-96c5-9eca14a5c0f3&algo_exp_id=5ce76084-f011 -4104-96c5-9eca14a5c0f3-7&pdp_npi=4 %40dis%21EUR%2137.27%2111.93%21%21%21282.56%21%21%402103879316989533003923329e2f6b%2112000033688941549%21sea%21IT%21860224597%2 1&curPageLogUid=zdTwceVUqL5Q

https://it.aliexpress.com/item/1005005376321948.html?spm=a2g0o.productlist.main.113.7b405611UOqSVk&algo_pvid=9db52ccb-1441-4451-975c-c7bfc3282562&algo_exp_id=9db52ccb-14 41-4451-975c-c7bfc3282562-56&pdp_npi=4 %40dis%21EUR%2120.90%2115.67%21%21%2121.64%21%21%402103879316989537356773301e2f2a%2112000032800852023%21sea%21IT%21860224597%21 &curPageLogUid=l8896PHwOEAv

https://it.aliexpress.com/item/1005003510629231.html?spm=a2g0o.productlist.main.67.77865367FqnsFj&algo_pvid=0e1e0761-ba6a-4f46-b9f7-037605c41119&algo_exp_id=0e1e0761-ba6a-4f46-b9f7-037605c41119-33&pdp_npi=4%40dis%21EUR%2116.14%218.56%21%21%2116.71%21%21%40210384cc16989551794502216ed249%2112000029252610835%21sea%21IT%21860224597%21&curPageLogUid=zS0uLzFgYrvb

Many thanks Roy.
They were that cheap I bought 3.
I'll experiment with the batteries I have before investing further so now all I have to do is wait until the bits arrive.
Back to the building board.

Further to my post, when in use and the throttle control is in neutral, when you use the rudder only the boat should start to spin on it's own axis.
Using these esc / mixers you can see they use small 2 pin connectors. I buy these with the mixer ready made. Last time I bought 5 female and 5 male connectors for about a pound, so very cheap.

If you use Tamiya leads on your batteries make up an adapter lead with the male Tamiya lead and one of the 2 pin red connectors.

The 385's I suggested will only take an amp at most so no issues with high current or cooling. The esc unit does not need cooling at all.

Hope this helps
Roy

Hi Steve-d, I have sourced below a typical single unit controller. It is an esc for 2 separate motors and has a built in mixer function. There is a single yellow lead which would go into the rudder signal socket on the receiver.
You would then have speed control for both motors and when you use the rudder it speeds up the outer motor and slows the inner one on a turn.

But like this the rudder servo is not connected. So to get the rudder and the mixer to work together get a Y servo lead and plug it into the receiver rudder servo socket.
Plug the rudder servo into one of the Y o/ps and the single yellow wire into the other lead's signal wire socket.

The servo leads are black on the outside red in the middle and then a light coloured lead next and this is the signal lead. Do not muddle them up!

There is only one throttle control on the transmitter and so it all works on a 2 channel RC set.

regards

Roy

https://www.aliexpress.com/item/33008316502.html?spm=a2g0o.productlist.main.91.19ab3O9y3O9yBo&algo_pvid=699f62fe-3851-45e5-81aa-059825caaaf6&algo_exp_id=699f62fe-3851-45e5-81aa-059825caaaf6-45&pdp_npi=4%40dis%21GBP%215.13%214.51%21%21%216.07%21%21%402103847816989439021751405ebfc4%2112000033529852297%21sea%21GB%212773551854%21&curPageLogUid=2Jd8DyqpXEbm

Hi Dgoss.. They are a nuisance. They slow down the time it takes to go to reverse.
I mentioned the very cheap esc's I use and they have a tiny switch for turning the brake off.

They would not unwind a prop as usually they are lock-nutted in place.
Roy

Going for an esc with a brake function, I would suggest you disable the brake. This could potentially spin the prop loose and I'm not sure serves a useful function on a boat!

Hi Steve.

After reading the opinion of the others, it also evaluates this ESC.
In my opinion it has interesting characteristics, a guaranteed brand and an affordable price (not cheap but good value for money in my opinion).

The Gra2880, of the Graupner, has these characteristics: naval variator V30R 30 Ah with reverse, Operating Voltage 6 ... 12 V Celle Nicd, Nimh: 5 - 10 cells PB: 3 - 6 Maximum current: 30 Ah Max Current Reverse: 20 Ah Temperatures Cut-Off:-Emf Brake Reverse Mode: Si Power-on Signal Suppreation: Yes Pulse Frequency Appros. 800 Hz Bec: 5 V / Peak 5 A Dimensions 69x31x11mm Weight 65 g type of JST connector

If you want to spend much less oriented on automotive ESCs of 10 euros at most, but take into account that they could break without a clear reason.

I, personally, advise you to protect ESC (whatever ESC you put) and engine with one or two fuses from the car.

Thanks guys for the response.
Roy's choice of 385 looks to be pretty good when compared to the list Terry added so, again, thanks.

I've bought the 385s and mounts.
Next is ESC. Most of my searches take me to the Mtronics versions which are rather expensive. I said before cost was not an issue but if there is a valid cheaper version then let me know.
I had thought I would run an ESC for each motor but there has been mention of mixers and I don't know how they work or what to ask for.

This is Groupner motor list which might help

Hi LewZ thanks for the motor spec link. Very useful especially for measurements and performance data.
Roy

Hi Steve D.

I, personally, have always preferred brushed motors.

I'm not saying that brushed motors are better than brushless ones, but considering the characteristics of one type and the other, in relation to my needs (or rather the needs of the model) so far I have opted for the brushed ones. But it is a completely personal choice.
The cost probably also influenced the choice.
I am more oriented towards the choices of Scotts and Roy but I really like Rodc's choice, clear, detailed and precise and I would be very curious to try it in the future.

I have become increasingly familiar with brushed ones: to start them you just need to give them the right voltage, to reverse the gear you just need to invert the polarity, to accelerate you just need to increase the voltage (logically up to a certain limit); on the other hand, brushless motors need electronic control to rotate the magnetic fields, it is not enough to provide voltage on the windings.
It's certainly not a problem, the ESCs will do everything.

It's true, brushless ones (technologically more advanced) are quieter and don't have brushes which, over time, will wear out. They don't spark.
However, brushed motors (I don't want to be wrong because I'm not an expert in commercial research) are generally cheaper than brushless ones.

Precisely because they are different they have two completely different types of ESC.
Therefore on the economic scale considers not only the cost of the motors but also that of the ESCs.

I prefer to choose a motor with a voltage range greater than that of the batteries, but this is a questionable choice.

Not being very experienced and having space problems in the hull, so far I have opted for the direct attack. That is, the propeller shaft is directly connected to the engine shaft and I delegated the reduction of rpm only to the radio remote control.
The most experienced and capable model builders will rightly advise you to reduce the rpm via gears for more realistic navigation.

I'm curious to see your electrical and mechanical setup, please post lots of photos as you proceed with the work.

There are plenty of motors out there so the choice is yours. They run from cheap to expensive, perhaps overpriced. Check to voltage current draw, stall current, and if selecting a brushed motor, the windings, shaft diameter, etc.

Ebay has a lot of them, originally made for electric drills, vacuum cleaners, and many other objects. Almost all of mine are simple, low cost motors, costing only a few US dollars each. So cheap that I usually buy 3, 4, or 5 at a time and put them in my spare "motors" box. This way I have replacements as well as some ready for new builds.

Cheap does not mean they will not function or last long. (I've seen even good model boat motors die young.) Think of the original purpose for some of these motors as I mentioned above. A decent ESC will turn these motors very well at all speeds.

Sometimes the labeling on the motors is faint so I take a Sharpie pen and re-write the motor model number as well as the volts, speed, current, amps. This helps for searching through a box of motors. Install the motors with the labeling up in case you need to replace them.

Lew
Florida, USA

Visual link (to get an idea about the comparison of sizes) for some common motor sizes: https://www.nfpmotor.com/dc-electric-motors

Hi Steve
You can always get two brushed 540 motors and if you are going to you them you can always get two brushed rc car esc or a dual esc for a RC car

roycv, I like the 650kv brushless mtrs being custom made & sold thru ZIPPKITS in Florida.

My ESC didn't run one on a 6V SLA but when I put two 6V SLA in series everything was perfect.

These motors are inexpensive, & display excellent torque at low rpm, very smooth transition thru midrange, & then up to full power. I use an aeronautical-style TX with throttle on the left stick, spring to centre return for neutral. I hav found the wheel-'n-trigger type its tough to give smooth proportional throttle.

The ZIPPKITS plastic tug props come in lefthand & righthand & are very economical. They are cast in a bronze-looking plastic

Hi reading your post again the HDMLs were not meant to run fast like MTBs. I think 15 - 17 knots (experts please correct). I suggested brushed motors which I think give you a better control at slow speeds.

My only experience with brushless was about 10 years back and the slow end was rather ragged.

regards
Roy

Hi I have a HDML (36 inches) twin screw that goes at a nice speed, just a small bow wave. I use a couple of Pitman motors but comercial not in the modelling sphere.

However I think a couple of 385's would suit. They are often quoted as up to 15 volts, and I would go for 12 volts but they may be OK on 7.2 volts.
Props are Prop shop 35mm 3 blade.
So no cooling required and each motor takes less than one amp.

I use a mixer and 2 batteries and 2 ESC's. You might even get away with high capacity AA cells. The ones I use are 2/3rds sub-C's 1.3Ahrs and last a long time.
If you go for 6 or 7 cells, try the very cheap esc's from Ali Express, they will easily cope with the current. They are only £2 or £3 each, might have to wait a few weeks though.

I have a single unit double esc (2 motors) with a built in mixer, I think from a similar source. There is a single wire which connects to the rudder servo signal in the receiver. I have yet to use this unit but expect to use it in a future twin screw model boat.

My HDML has the mixing function in the transmitter. She spins on a sixpence and is delightful to run.

regards
Roy

Nice lines, I like it a lot. I'll stick with it.👍

Not much to show just yet as just a plastic hull with the prop shafts going in. Some pics of how she is now and one of her in better condition.
Also not in one picture the plan suggesting Monoperm motors.

Pictures, pictures, picturesPictures, please