Broad Ambition - The Model

[FairTmiddlin]

4 hours ago, TheQ said:

I take it Broad Ambition will have smaller Broad Ambition exhibited on  table, inside (or on deck,) that therefore will need a even smaller Broad ambition sat on deck,  ..

which will need an even smaller on Deck..

which will need an even smaller on Deck.

etc

Yes but!

Doing that would mean,

when you move the model,

you would have to move every iteration of it.

Make for a very interesting evening

 

[OldBerkshireBoy]

Nah, just glue them together! 

[grendel]

more work on the cabin roof fittings, all now fixed down, solar panel fitted and wired to a connector under the cabin roof

[Boatingman]

Absolutely superb

Ray

[BroadAmbition]

It certainly is.  There's a proper danger that he will have model 2 finished anytime soon

Griff

[Polly]

Is the solar panel actually practical or is it decorative? 

[grendel]

the solar panel caused me no end of problems finding one with the correct voltage to charge the lighting circuit battery, in a flexible panel, that was the right size (actually forget the voltage, just the flexible in the right size was tricky, happily the voltage was perfect.), i did find two options, a single panel as you see, or a pair of panels half the width, but not quite as long as the bigger panel, this bigger panel was better size wise on the roof, if you look very carefully at the starboard side, you can see the pads of solder, the wires run up through the roof at the very edge and are soldered on.

[grendel]

todays work was adding some details, the ships bell was hung, fenders were fitted with ropes and hung down the sides

[BroadAmbition]

Looking great, the spotlamp on the fwd roof needs to be painted white.  And just noticed there should be a 'Cut Out' above the fwd passageway below the windscreen.  I'll see if I can find a photo or two

Griff

[grendel]

yes, spotlight was painted white about 5 minutes after i posted the update, I probably have a picture of the cut out, but it can probably wait until I make the doors.

[grendel]

Attention was taken today over a few details, not 100% happy with the results, but i can redo them if necessary after the wooden boat show, today is packing day for my holiday, then theres only a few days before i am due back for the wooden boat show, but as almost everything is ready, it meant some spare time, a temporary rear door has been made, this just puts wood in't'ole so to speak, a new door that hinges will be constructed to replace it, and i have finally added the lettering to the cockpit sides, not 100%  happy its as good as it could be, but it will have to do for Beccles, then it may get redone.

[grendel]

I may end up cutting a stencil for those and spraying them with my airbrush.

[grendel]

after trial runs at the wooden boat show, it was apparent that the model was stern heavy, this means some modifications to the battery are in order, the current lead acid battery weighs in at about 2.7Kg, I can drop the weight to at least 1/3 of that by going to lithium polymer batteries, the main issues revolve around voltage, I need to perform some speed tests to see if an 11.1v lithium battery can produce the same performance as a lead acid battery, or whether I will need to go up to 14.8V.

[grendel]

a power usage monitor has been purchased, amazing how cheap these sort of things are nowadays, and tonight after creating some wiring to insert it into the motor circuitry some tests were run, with the standard lead acid battery at 12.7 nominal volts, the motor consumption running free is 18W, using a lithium pack at 11.1 volts nominal it drops to 17.5W, next job tomorrow is to repeat the test in water, i want to see how each of the batteries reacts to the added load, theoretically the lithium cells should hold up longer as they are capable of delivering a much higher current than the 12v lead acid battery.

[grendel]

this means that if i accept a very slight drop in power i can change  over to a lithium battery quite simply, the other option is to increase to 14.8V, where i will need to change the speed controller too, and gain an increase in power slightly.  lets see what the in water tests show.

[Islander]

Why not use a DC to DC convertor. You could either boost or drop and no need to change your motor controller.

Colin 

[FairTmiddlin]

No need for that Just put a resistor in line covered in heat shrink.

 

[grendel]

mostly due to the potential 20A stall current, not many dc to dc converters can handle those types of current (well not ones that wont be bigger and heavier than the battery in there, ditto resistors, you wouldnt want to put a bit of heatshrink tubing on a potential voltage dropping resistor  we used to do similar with 50W 1 Ohm resistors to fast charge ni cads for model car racing, even bolted to a good heat sink, these got hot enough to brand fingertips if you forgot and touched one, anyhow testing has been done in the upstairs white enamel test pond, and though the 11.1V lithiums are not quite as good as the 12V lead acid they still give pretty impressive performance, i did have to find a better 11.1V lithium pack and cobble together the connection.

[grendel]

Video 1 with the first (none too good capacity wise) lithium battery.

Video 2 is with a 12V (11.1V ) lithium tool battery of 2Ah capacity, this gives a lot better performance than the original lithium battery which i could see discharging as i watched it.

 

[grendel]

basically the results showed that the lead acid battery gave out 60W  (5Amps) initially on a full charge, the better lithium battery managed 58W on full charge voltage.

However, the lead acid battery will slowly lose voltage at that current drain, while the lithium should hold pretty stable at that level throughout. 

This is just using a bulk standard lithium tool battery, the ones they have for model boats are capable of delivering much higher currents, i have yet to test one of those (as i dont have one yet - they are on my boot fair watch list for testing purposes)

the other test i did was using a smaller lead acid battery as ballast, and one at about half the weight of the big ones i use is the perfect ballast, bringing the boot topping just above water level.

You will also see just how much water this single 35mm prop moves by the wash up the back of the test tank. i would worry about cavitation if i upped the power much more than it is at the moment. the lithium batteries will come in at about 1/2 to 2/3 of the required ballast weight.

[grendel]

here are the discharge curves, of the two types of battery, the lithium curve would be dropped to start slightly below the lead acid, but you can see that after the first few minutes the lithium would be higher output than the lead acid, and stay that way longer.

ignore the voltages, I m just using the graph because it shows the discharge curves.

[grendel]

basically in the test the lithium settled out at 11.7 Volts under load, while the Lead acid settled to 12.05V under load.

[Islander]

Unless you are building to MOD spec ( ministry of defence not moderator of de forum ) to please Griff, I would say the lithium wins hands down as far as stamina goes. The lead acid, in theory, may win a drag race but the lithium will win the marathon.

DC to DC convertor wise, I thought something like this may have been useful and the weight, I would think, is quite low and well within what you save by using lithium. 

https://www.ebay.co.uk/itm/DC-DC-Converter-20A-300W-Step-up-Step-down-Boost-Power-Adjustable-Charger-P8T4-/224038775789?_trksid=p2385738.m4383.l4275.c10

All in all Peter, the model is looking great.

Colin 

[grendel]

yes that would do the job, but why make things any more complex than necessary, if I can get the power out of 11.1v lithium without needing to change out the speed controller etc, then that is the way to go I think, if I go for a 10Ah battery that will give nigh on 2 hours runtime at the 5A maximum in water consumption (the 20A is under stall conditions, and I havent managed to stall it out even with weed on the prop.)

[Islander]

I must admit I agree. There is little to be gained from the added complication but these clever little devices would mean almost any battery pack could be used. I about to use one for the Mrs portable sewing machine. It's 6v and she wants to use it of 12v. The price of these boards are so low there is no point in me designing and building one. By the way I do like your power meter. I will be looking for one of those on  Fleabay.

Colin