Print

Please login or register.
1 Hour 1 Day 1 Week 1 Month Forever
Login with username, password and session length.

[Bob K]

Thoughts always appreciated . . . 

Sorry this is dragging on folks, but I am trying to resist the temptation to rush the last bits of wiring plumbing and testing. Fingers crossed for commissioning then ballast trimming.

I might even get to start the deck planking after that 

[Bob K]

HMS Polyphemus (1881)

Plumbing

I have replaced almost all of the flexible pipework with copper, including silver-brazed tee’s. This will hopefully make them more secure as they need to be kept airtight, especially around the tank-tops.



  Air System Circuit

Bilge Control

With six separate compartments it is not practical to install a bilge pump and controller in every one.  Having checked with Hunter Systems I have fitted individual sensors in each compartment, wired in parallel to a single Hunter Controller.  The output is wired to a mini 12V Piezo pulsed alarm of 105 dB. 



At the first hint of ingress I will hear about it and can rush for the shore.
Being ultra-careful with my resurrected ex-Polly’ as “Norwegian Blues stun easily”.

Systems Commissioning

Double checking all the wiring, yet again, then testing the various control systems individually.
Tx on, power & Rx on. Servos for the 3 rudders OK, props working, air valve and pump operation optimal. 
Popping one of the six bilge sensors into a cup of water was instantly deafening.
Yes, we have ‘smoke’, with throttle-variable fan speed and engine sound.

Too complicated?  Certainly !   

Re-cleat wiring looms then fill the dry dock (bath) for re-ballasting and another long leak soak.

[derekwarner]

Hi Bob........just a thought......

1. the water pump has nylon type suction & discharge male stud tubes.....these also have a cast in barb on the OD
2. it would be advantageous to install miniature cable ties or DUBRO fuel line wire clamps for added security
3. you can also soft solder a ring of copper wire around your copper tubing to act as a barb for the same attachment with clips or cable ties etc

Not sure how the water side of your bilge system is designed  ...with six suctions in six individual compartments....if a sensor detected water in one flooded compartment ...it activates the pump?...OK...I see the electrical control of this 

But do you have six solenoid valves to ensure that the other five compartment suctions are not drawing air & hence negating suction in the flooded compartment?

In many real marine builds....each hold has a bilge, however in a model application could you not have each of the six compartments connected to a common bilge? & then only one sensor or two for added security/redundancy in this one common bilge suction?.......

or have I totally misunderstood this and the sensors are for an alarm only?....& not for control of a pumping function? 

Do the sensors work with fresh clean water or do they rely on metals/crud or contaminates in the water to make contact?

Too complicated or too simple?.......keep us posted

Derek 

[Bob K]

HMS Polyphemus (1881)

Many thanks for your detailed input Derek.  Both the pump and valve have barbed nozzles, so I will take your advice and source some fuel line clips which should help greatly. 

Most subs appear to be plumbed in flexible tube.  The silicone tube is an extremely tight fit on my 5 mm O/D copper.  My key thought was to have a rigid pipe between the opposing tank top stubs, again a close fit, sliding flexible tube sleeves over the end-butted joints so it could not easily be pulled out.
I will look into having clamps over these joints.  Thanks.

The bilge controller’s twin-prong sensor utilises the significant difference in electrical resistance through water versus air.  When water bridges the prongs a threshold is tripped which switches on the output circuit.  If any one of the sensors gets wet it will trip.

In my case I am using this to set off a single alarm, rather than multiple pumps. 
The original idea of 6 compartments was that if 1 or even 2 flooded it should still float.

[ballastanksian]

Almost there Bob! And then on to finishing the superstructure IIRC.

[Bob K]

Indeed ballastanksian !   I almost can't wait, however she is currently doing an all-day bath test.  Four hours static, then power up and test the trim control levels.  So far so good.  Only needed 200 gm ballast adjustment, to port rear, to get her exactly level.

[Bob K]

I am excited !  Five hours in the bath and not a hint of water ingress.  Ballasting controls have her going up and down by just over half an inch, and keeping an even keel whilst doing so.  Excess air bubbles evenly from both groups of tank-bottom vents nicely when fully blown. 

At this point I am so pleased that I was pig-headed enough to persevere with the internal restoration and problem solving.
 
However, if the Lady of the House finds out that I have been funnel-smoking in the bath I could be in deep water.   

Time to start fitting the six compartment covers, sealing the control panel, and recommencing work on the decks and superstructure.

Thank you everyone for your patience 

[ballastanksian]

Excellent news Bob. I look forward (as I expect you do) of the coming day when we can see 'Polly' on the water, perhaps via Youtube?

Onwards with the plethora of Nordenfelts and struts.

[dreadnought72]

I am excited !  Five hours in the bath and not a hint of water ingress.

I hope that's the boat and not you, Bob?! 

Andy

[Bob K]

HMS Polyphemus (1881)

Experimental hatch seal tried, as an alternative to smearing the neoprene gaskets with silicone grease before fitting the screwed-down clear Lexan hatches.  That had proved rather messy to clean up whenever access was needed.

After tests with household film I bought a roll of industrial triple-thickness cling film, more wrinkle resistant and better application.  It sticks almost by itself to both gasket and hatch, and when “sandwiched” between should provide an additional sealing membrane.  Easily replaceable without mess when required.

A standard watering can test should prove the “pudding”. 
Technically the hatches do not need to be dive proof, but give similar wave protection to the hatch covers on model yachts and tugs.

Control Panel

The rebuilt control panel was carefully seated in place on its mounting flanges using a little silicone sealant and screwed down.



Next stop will be Peterborough for an extended sailing trial at the Deans Marine shallow test pond.

[ballastanksian]

Great news Bob! I wish you god speed on the pond.

[Bob K]

HMS Polyphemus (1881) Sea Trials

After almost a year of research testing and restoration HMS Polyphemus took to the water again today, at Deans Marine test pond near Peterborough, amid patches of icebergs.  Not a good omen?
However, unlike the very deep home waters of Black Park Lake this pond pings only around eighteen inches on the echo sounder. 
An important safety factor if you have been following the history.

Five hours of bath testing appeared to auger well so a full sea trial was called for before committing her to scale depth oceans.

A little cycling of the depth controls was needed to balance the ballast tanks, but after that an even keel was achieved.  I might reduce the recently added side ballast a bit.

Three and a half hours on the water, without the Piezo bilges alarm going off, has massively boosted confidence in the integrity of the hull sealing modifications.  She goes up and down by a range of nearly 20 mm.  Even in deep trim she sails nicely, but with a wide turning circle. The inside prop almost stops with almost any rudder movement.



I am still not happy with the 40 Mhz system, not as responsive as 2.4 Ghz, and with intermittent ‘fluttering’ of rudder and motors with controls centred at rest.  I may convert to 2.4. 





All in all a very successful day.  The long overdue recommencement of deck planking and detailing can start.  Now I am into the fun part of the build.

[essex2visuvesi]

You set about this with the determination of a Yorkshire Terrier and it looks like you have finally cracked it.
I hope you are celebrating your success with a very large glass of something expensive :)

[ballastanksian]

Amen to that Mr Essex! She looks a sweetie already. I hope the conversion to 2.4 is not onerous.

[Bob K]

Thank you guys, appreciated. 
The 40 Mhz system was occasionally "fluttering" the rudders and motors with sticks centred, so I am a bit concerned never having had that on 2.4 Ghz. 
Anyone experienced that?  Possible causes?

[essex2visuvesi]

I've had Servo chatter on cheap servos in the past.
What radio are you using? it might be possible to increase the deadband which should eliminate the twitching on the servos and esc.
Some ESCs have deadband adjustment as well

[Bob K]

The Transmitter is a Robbe/Futaba F14, using the big Rx that came with it.  Bow servo is the Futaba S148 supplied with the Tx,  Rear servo is a chunky ACOMS AS-17.  However, I do have the throttle channel also tied in to a small Action mister fan speed controller, plus a small Action sound unit.  P96 twin ESC / mixer.
The rudder channel operates both bow and stern rudder servos through a 'Y' lead. 

Yonks ago, on her first outing at a Beale Park Show, despite being assigned my frequency by the organisers, she immediately shot off uncontrolled and it took time to get her back. I can only assume that someone within rage was already on my channel number.  Hence my nervousness of 40 meg.

A lot more testing required, but if all else fails I will swap to 2.4

[unbuiltnautilus]

Check the transmitter antenna connections in the handset. These are notoriously 'Heath Robinson', consisting of a solder tag connection from the electronics, to an M3 NBW through the top of the set. Check all your connections there are good and clean.
Nice to see it on the water

[Bob K]

Thank you for that advice. I have not used that Tx for a long time.
Almost all of the ships wiring has been replaced during the refit.

For a ship of 2,400 tons she only had 500 tons of buoyancy so most of the hull is below the waterline, hence why 40 Mhz chosen.

[ballastanksian]

Forgive me for asking again if you have already explained the aerial mounting, but is it all within the pressure hull or is the length required for the wave length of the signal exposed as if the latter, the amount of freeboard should not matter unless the reciever benefits from being bathed in signal as well as the aerial. As it is short, the 2.4gig aerial may be more of a problem. Looking at images of the mast I am sure you could hide ther aerial in it.

[Bob K]

The 40 Mhz aerial wire from the receiver runs almost the length of the hull, close under the decks.  Using 40 Mhz the aerial will still receive signal if well under the waterline, which is why submarines use this frequency.

If I were to use 2.4 Ghz the very short aerial (~20 mm) would have to be close under the f'o'c'sle deck, about an inch above the waterline.  Not so good for reception, especially as the ship gets further away as 2.4 cannot go through water.  Even a good bow wave could 'obscure' the signal. 

In both cases aerials are fixed length built in from the Rx. 

[Ian K]

Hi Bob,

Just a thought, regarding the 'jittering' effect you have got, have you fitted suppressors to you motor terminals? There is a lot of cable within your hull, and you may be getting electrical noise from it all.

Try to keep the main power supply and speed controller cables away from all the Rx radio side, this may help.


Regards

Ian

[Bob K]

Hi Ian.   Interesting.  You may be onto something, in a round-about way.

It all seems to run OK here on the bench, it was just something I noticed occasionally on Saturday in the water.

Yes I do have suppressors on the motors, terminal to terminal, but not terminals to case.
ESC/Mixer is fairly close to motors, about 70 mm, so short ESC to motor cables on ship C/L, DC power cables routed down port side, servo leads etc down the starboard.  So far, so good.

However, due to the need to charge and switch on without stripping out the hatches, there is a lot of DC that runs from the three sets of batteries to the control panel then back to the stuff it powers.  In some case quite a long loop of power-bearing heavy gauge cable. eg: the 6V for the motors doubles to almost 900 mm.  Maybe relays might have been better, but more devices/connections to possibly 'fail'.

PS:  I have since adjusted the pot in the P94 to increase rudder movement before stopping inside prop. With big slower props close together I think this should help her turn better.

Bob K

[Stavros]

Bob try changing the Acoms servo for a futaba one.....I have had trouble in the past with Acoms servos
 
 
Dave

[essex2visuvesi]

Bob try changing the Acoms servo for a futaba one.....I have had trouble in the past with Acoms servos
 
 
Dave

What Dave said


Also if you go down the 2.4Ghz route, have you considered an RX with satellite options like this one.
http://www.hobbyking.com/hobbyking/store/__1123__1117__Radios_Receivers-OrangeRx_Satellite_Receivers.html


Of course you would need to have a spektrum compatible TX