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[Bob K]

First time in the water !!!

Finally, received the “Next Day Delivery” batteries ordered Friday (Delayed by a Wedding) arrived Monday.

The ten foot paddling pool was repaired today.

Hull halves joined with sliding stainless telescopic tubes, and inter-hull latch clipped home.  Currently with deck panels (and guns etc) removed to check for leaks.

It Floats !!!

A shade heavier than planned due to having to replace the special LiFePO₄ battery (2.2 kg) with two regular 9Ah SLA’s totalling 5.6 kg.  Result is it floats slightly lower than calculated, but I can live with that.   



A couple of very minor leaks, but no problems.  A little bit from round the rudder tube, it must have taken a knock, and bit around the latch coffer dam.

With deck panels off you can see the switches and charging sockets for the 8 batteries required for the various electrical systems.

Electronics to be married up on Saturday morning in Sudborough, on the way to Wicksteed. 
Are we cutting it fine ???   Yes

[Klunk]

looking forward to seeing this Bob. build of the year

[SteamboatPhil]

So Bob, do  you now fit wheels to it and drive to Mayhem with the car on the back......or....more likely will you be sleeping inside it this year
Tis awesome M8.......that is text speak apparently 

[ballastanksian]

Hark at you Phil, going all 'Yoof' on us!


I am pleased for you Bob. It shows that you were doing it right from the word go if you only have a few wee leaks and a little extra depth. Go careful with setting your electrics up and don't rush. We'd rather see a running model than one that experienced the magic grey smoke from rushing the other electrics.


She looks fab 

[Bob K]

Wicksteed  T-0

The day of Wicksteed had finally arrived and after a very early start I journeyed to C0-3PO’s to commence the initial marrying up of the floating hardware and the intricate computer systems.   It was highly unlikely that we would complete the transplant, test everything, and update the software in each of the boxes.  However, if we could achieve something that could be demonstrated that would be wonderful.

After installing the Main Control Unit, Slave Control Unit, and getting the two halves of the ship talking to each other, C-3PO installed the forward three turret control boxes. Turrets rotated and LED’s flashed.  Discretion prevailed in not firing the guns in his conservatory.  I know they make a lot of smoke.

At that point it was 3 PM So we headed to Mayhem, hopefully not too late to create a stir.

The two hull halves were joined together and the huge ship lowered into the water for it’s maiden voyage.  Wonderful to see it underway for the first time under power.  Initial thoughts were that it really did not want to steer, and the big motors generated less tractive effort that anticipated, but an awesome start.
Did anyone get a photo ?

Huge thanks to Geoff and C-3PO.

[raflaunches]

It was great to you and Agin/Court over the weekend to see the progress in model form and I’m certainly impressed. I’ve got some pictures on my camera when she was on the water. I’ll download them this afternoon for you.

[Bob K]

Top man Nick.  Thank you.  I was too busy with my Tx to take photo's.   

[raflaunches]

Hi Bob


Just found the pictures of Agincourt on the water late Saturday evening.

[Bob K]

Many thanks Nick.  It proves she was on the water 

Some modifications were found necessary after the maiden voyage due to lack of propulsive oomph (if that is the correct nautical term?) plus great reluctance to steer.  So, the four 35mm props are being replaced with 45mm ones, which means I have to build in some under-keel protective skegs to avoid the prop edges clouting the table.  The rudder needs to be increased in size by around 50%.

However, it sailed.  First water 

[ballastanksian]

It was good to see her sail for the first time, and I reckon she did very well. The minimal water ingress can be alleviated and is to be expected on a maiden voyage.


Keep up the good work Bob!

[Geoff]

Indeed good to see her on the water and I can't wait until the tripods are mounted and she looks more like the real ship. The leakage was caused by capillary action at the hull joint and possibly by virtue of the motion of the ship. A big dollop of Vaseline may stop this or possibly some silicon sealant in a "U" shape with Vaseline the other side to stop it sticking, then pull the hull together and you may get a perfect seal or at least significantly reduce the water intake. To put this into perspective it was only about 1/2 a cup of water and that was contained by the latch mechanism so at some point it would stop leaking any more as the levels stabilised.

Keep up the good work.

Cheers

Geoff

[Bob K]

Thank you Geoff,

It did not help that the temporary main propulsion batteries were 3Kg heavier than planned for, making her over a cm lower in the water, and the latching mechanism closer to waterline.  The coffer dam around this limited ingress but I will probably need to do as you suggest even with the replacement lighter LiFePO₄ ones installed.  I had thought of embedding a one inch diameter O ring around the bar, set in to half its thickness.  The clamping force on the latch should force a seal, but Vasalene etc would help.

The telescopic tubes arrangement supported the hulls well, and did not leak. 
I believe this may be a first for hull halves connection so it is experimental.

[Bob K]

Propulsion & Steering

Motors props and steering becomes a whole new science for very large ships.  All the knowledge and experience gained on previous smaller vessels seems to fall flat at this magnitude.  I know several of us have run into problems in this bigger ball park.

Some necessary modifications after the maiden voyage at Wicksteed.  A lack of propulsive oomph (if that is the correct nautical term?) plus great reluctance to steer.  So, the four 35mm props have been replaced with 45mm ones, 65% additional blade area.  Inner and outer props now slightly overlap when viewed from the rear.

This meant I had to build a protective skeg projection under the rear of the keel to ensure the propeller tips did not get damaged against the table prior to launching.

The rudder needed to be increased in size by around 50% to provide greater effect in the water flow behind the props.  The extended forward end of the rudder now slightly overlaps the edge of the inboard propeller on full rudder.  Hopefully these modifications will make Agincourt move better on the water.

Before



After



Only another trip to a lake will tell if this solves the problems, but before that I need to put an ammeter in line to the drive system to check values, and another dip in the ten foot paddling pool for a batteries refit as she is floating 30mm too deep.  Much of that is due to the two 12V 9Ah SLA's in parallel I had to put in to replace the 12V 16Ah LiFePO₄ lightweight battery that refused to fit in the space by 3mm.  That added nearly 4Kg over the planned displacement. 

The 8 batteries comprise a major part of the displacement.

[Colin Bishop]

That's a big rudder Bob! However, have you introduced mixing to get the motors to help in turning the ship. If not, it could make a significant difference. Particularly if the ship is moving at slow speed or is stopped.

Colin

[C-3PO]

Hi Bob,

I know you have a P94 Dual ESC and Mixer installed - is it running in mode 3?

https://www.componentshop.co.uk/pdf/P94.pdf - Switch 1 off / Switch 2 on?

C-3PO

[Geoff]

Bob,

Is there no way you can get the larger battery to fit as its quite a difference in weight. If its a bulkhead issue you could always cut a door then seal the bulkhead the other side which would give you another 4-5mm to play with. As you have a fibreglass hull this would not impact the integrity of the structure.

I suspect the current consumption with the new props will be hardly any different given the high torque motors you have.

Cheers

Geoff

[derekwarner]

ob.......in October 2017 you display outboard turning propellers which is the traditional format for Capital size or Class and latter design Naval vessels

Today you display inboard turning propellers and comment on poor steerage characteristics

Have I missed the reversal of the propeller rotation?, simply increasing propeller diameter to water that is not there will do little

The first image is October 2017, the second image is this week

As C-3PO noted, ......the P94 Dual ESC and Mixer installed - running in mode 3 is also critical

Derek

[JimG]

Why not use LiPo instead of LiFePO_4, generally smaller and lighter.. I have a couple of 3S (nominally 12V when charged) 8Ah Lipo packs, each 165 x 70 x 25mm weighing 590g each. A pair of them in parallel gives 16Ah with capacity of providing much more current than you need. Looking on Amazon an equivalent 12V 16Ah LiFePO₄ battery weighs 2200g twice the weight.
Jim

[Bob K]

OK.  Some very old pictures Derek.  The latest shows inboard turning props, which IMO are more efficient.

I ended up using Mode 4 on the P94, on advice from Dave M (Inertia) back in October. 
"100% mixing on a 7ft model would be a bit extreme!"

I can't cut the bulkheads now they are installed.  They are 9 and 12mm thick for the mounting tubes, and not accessible now.

The current characteristics of the thermistors do not lend themselves to LiPo's, and need to be 12V.

Before going much further I need to get this into the giant paddling pool for some tests with an ammeter before deciding on batteries  At the same time I will test the waterline without batteries, gradually adding them until I go over depth on the waterline.  That will ultimately define battery choices. 

[Geoff]

Bob,


I have also thought about using LiPo's for the thermistors and whilst a 3 cell is nominally 11.1 volts I think this would work okay because even with lead acid batteries as they are used the voltage will drop below 12 volts - it just takes longer to get the thermistors to the required temperature. Lead acid can also be virtually discharged and used again where this would be the death of a LiPo.


Experimentation would be the key as it may well be that the current availability is more important than voltage.


The problem I see with LiPo's is that:


1) You would need some electronic circuitry to stop them over discharging and as this is voltage triggered I don't know how long they would last for before the voltage trigger kicked in.


2) Cost - individually they typically cost more than a single lead acid battery


3) You would need at least two or more wired in parallel to get the required capacity and I understand this can be tricky as unless they are identical one battery will look to discharge into the other at an exponential rate causing damage. I'm pretty sure there is some "electrickery" available to alleviate this problem though.


However I would see no reason why you couldn't use them for motive power and save weight that way as a possible solution. The speed controllers would need to be designed for LiPo usage as these automatically prevent over discharge.


I appreciate it would be impossible to remove a bulkhead but assuming the battery would otherwise fit you could drill a series of interlinked holes to cut out a section maybe? I can't recall the precise layout and internal structure which may preclude this but it may be viable to let you use the light weight battery.


Such issues always plague us big model builders. Just because its big doesn't actually mean you have usable internal space!


Cheers


Geoff

[C-3PO]

I ended up using Mode 4 on the P94, on advice from Dave M (Inertia) back in October. 
"100% mixing on a 7ft model would be a bit extreme!"

Bob,
I would think it would be worth a try in mode 3 - reading the PDF that would have been the mode I would have chosen - nothing to loose...

PDF specifies:
Mode 4 faster vessels e.g. fast luxury cruisers, MTBs and modern lifeboats

Mode 3 slower vessels e.g.  tugs, ferries, fishing vessels and other work-boats

C-3PO

[JimG]

Bob,


The problem I see with LiPo's is that:


1) You would need some electronic circuitry to stop them over discharging and as this is voltage triggered I don't know how long they would last for before the voltage trigger kicked in.
There are plenty of low voltage warning sensors available, many use either bright LEDs or a loud buzzer to signal low voltage. LiPo generally hold their voltage under load better than gell cells. Why they are used in high power electric flight.


2) Cost - individually they typically cost more than a single lead acid battery


3) You would need at least two or more wired in parallel to get the required capacity and I understand this can be tricky as unless they are identical one battery will look to discharge into the other at an exponential rate causing damage. I'm pretty sure there is some "electrickery" available to alleviate this problem though.

LiPos  are easy to connect in parallel, you just need two with the same capacity and as long as they are fully charged when connected they will not discharge into each other. This 'problem' was debunked years ago on RC Universe, originally for Lead acids, although still applicable for LiPos. In fact many of the larger LiPos are made up of parallel cells. ( often described as 3S2P for example) I have regularly used 2 packs in parallel without any problems both in the air and on the water.

However I would see no reason why you couldn't use them for motive power and save weight that way as a possible solution. The speed controllers would need to be designed for LiPo usage as these automatically prevent over discharge.


Cheers


Geoff

[Bob K]

Testing

I connected up an ammeter in between the batteries and the propulsion system.  Most odd.  Showing just under 2 Amps with all four motors turning flat out in air.  Strange, because these four motors are rated at 1.9 A each I expected a lot more.  Obviously it is with water resistance that counts. 
Joined up the two hull halves and with assistance lowered it into the ten foot diameter paddling pool.

With propellers going flat out in water it still shows only 4 Amps.  Not what I had expected.  Maybe the Buehler spec was for driving a much higher mechanical resistance load.  Well, one thing, that gives me more options on batteries as I was expecting nearer 8 Amps for four motors.

Buehler rate these motors as 12-24V.  24V batteries are not an option unless I connect 12V in series, but the ESC’s are only rated up to 15V so that is out.  The next choice is less Amp Hour capacity for the main batteries, which will save a lot of weight.  With only one of the two 2.6Kg 9Ah batteries installed she sits more closely to the waterline.

Now if I can offload that to shore and fit a single LiFePO₄ 12V 7AH that should still give me two hours sailing (flat out) plus shed 1.6Kg of weight.  (4.2 Kg less than twin SLA’s)

Turning

Next I tested the steering, as far as I could with only 18 inches of water for and aft.  Remarkably the larger props quickly moved it forwards, and full rudder provided a good swing.  The same in reverse.  In fact reversing the props seemed to slow it considerably even in a confined space.  Being able to stop is as essential as a workable turning circle.

I think I am getting there. 

PS:  LifePO₄'s are self limiting on current, whereas LiPo's would need additional circuitry to shut down on low voltage. 

[Geoff]

Bob,


Iron Duke only draws about 3.5 amps on full throttle in the water and about 2.5 amps in the air running on 6 volts. I suspect the current consumption is lower that you anticipated as you are using the motors on 12 volts and not 24 volts but its a very positive result.


Cheers


Geoff

[Bob K]

Geoff,

It is indeed a positive result, though I am still not sure why as the motors are quoted at 33W, which does not equate to the half Amp each I appear to be getting, even at 12V.

Still, not to look a gift horse in the mouth.  If I can run them on a 960gm 12V 7Ah LiFePo₄ I am a happy bunny.  Battery on order.

Bob K