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Author Topic: Bob's H.M.S. Polyphemus  (Read 208377 times)

Bob K

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Re: H.M.S. Polyphemus (1881), Ballast R&D
« Reply #225 on: January 05, 2013, 11:26:24 am »


Ballast R&D

After finally getting the ballast tanks fully airtight it was back to bath testing to adjust ballasting requirements.

With tanks empty and air tube outlets sealed the hull floats nicely, with or without major mass items fitted. 
 
However with the tube outlets open to air and an empty hull there are problems.  After a few minutes one side or the other dips slightly, admitting more water, and lifting the other side.  Eventually whichever side starts the list completely fills and the hull capsizes.  I need enough low fitted ballast to keep it level.

I now have a smaller 6V battery, the same footprint but almost half the vertical depth, and have ordered 2Kg of lead shot.  Mass needs to be as low as possible.  Whether enough lead can be spread in the keel areas to gain stability, with or without internal equipment, will be an R&D evaluation.

Should the amount of lead shot required exceed my total ballasting calculations I may have to opt for an under keel mounted pod instead, perhaps on a 100 mm keel fin, to provide leverage and even lower C of G.
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Re: H.M.S. Polyphemus (1881), not quite a submarine
« Reply #226 on: January 05, 2013, 02:33:26 pm »

If you ever look at fast electric racing boats, you'll see that many of them have a free flooding chamber on one side of the boat. This is to (hopefully) self-right the boat when they capsize in rough water. You're experiencing the same thing, albeit in reverse.

This shouldn't be a major issue once you get some weight in the hull, but that weight must be low down and well centralized.

I said it before, I'll say it again, I think the layout you have is going to be top heavy. Too many batteries high up in the hull. I would simplify things to one single battery pack, and get that pack as low int he hull as possible.

I would have also run a single main ballast tank in the centre of the boat, and not used saddle tanks. That would have given you a much more stable boat indeed, as the tank fills and empties in in one go and the boat effectively remains wider, meaning bigger righting moments across the width of the hull.

The same central tank could also do a double job of acting as a water reservoir for the water mister/smoke unit. Dismantle the unit you have, and put the mister unit inside the tank, and mount the fan on top of the ballast tank. This would save additional weight, which could then go in the bottom of the boat as lead ballast

Bob K

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Re: H.M.S. Polyphemus (1881), Ballasting continues
« Reply #227 on: January 08, 2013, 09:36:28 pm »


I refuse to be discouraged, or be told to scrap the hull and start again. 
Internal structures are now embedded in up to half an inch of rock-hard mastic.
 
Ballasting Trials Continue
 
Full size subs have side ballast tanks, either saddle or double hull, so the system should work. 
Ref: http://w3.shorecrest.org/~Lisa_Peck/Physics/All_Projects/photojournal/paul/submarines.html
 
This model's tanks extend down to the effective bottom of the hull, minus the keel ridge, almost the same as in a circular section hull. 
The base of the new 35 mm high main 6V 7Ah battery is level with the bottom of the 100 mm deep tanks, as is the Mister. 
 
The R&D stage I am at is determining ballasting for both deep and shallow waterline running. 
With tanks empty and main internals added she rode level and fairly stable.
 
With tanks flooded the dry space beam to o/a length ratio is still better than my destroyer which is very stable.
 
Please remember the latest bath test was on a completely empty hull, unstable with open vented tanks, but many model warship hulls might be unstable without any internals or ballast.
 
Moving almost a Kilo much lower
 
So, we need to transfer a lot of mass to much lower down in the hull. 
The new 7Ah battery is 930 gm lighter than the original 10Ah, and 17 mm lower.   
 

 
The original ship had detachable keel ballast, so 550 gm in lead sheet strips is being trialled underneath the keel ridge. 
Around 400 gm of lead shot is also being added inside the keel spaces. 
Together this almost a Kilo of mass transfer should generate much greater righting moment at between 60 mm and 100 mm below the deep waterline. 
All other mass items are centred well below both waterlines.
 



There is now nothing of significant mass in the top 60 mm of each compartment, which is vastly more than in my surface warships. 
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Re: H.M.S. Polyphemus (1881), Ballasting continues
« Reply #228 on: January 08, 2013, 10:38:43 pm »

I refuse to be discouraged

 :-)) Hurrah!

I can't wait to see this in her element.

Andy (avid reader)
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Re: H.M.S. Polyphemus (1881), not quite a submarine
« Reply #229 on: January 09, 2013, 03:46:10 am »

I do admire tenacity Bob. I'm still enjoying the build too.
Dave
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Bob K

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Re: H.M.S. Polyphemus (1881), Yippee !!!!
« Reply #230 on: January 09, 2013, 04:55:33 pm »

 
Yippee !
 
Today has been Most Bodacious (to quote the Bill & Ted movie). 
Polyphemus has been sitting in the bath all day, steady as a rock.   :-))
 


Maybe I should not annotate this build as a page by page, but only after significant steps forwards.

Stability Achieved

After fitting the 900 mm long lead keel and 400 gm of lead shot in some of the keel spaces the hull floats with significant stability, even with all tank vents open.  Prodding down one side or the other results in an instant righting effect.  Just 950 gm in the lowest possible areas made all the difference..

I did say this was R&D.  ie: A lot of trial and error, hair clump pulling etc

OK, with hull empty and open vents the ship is now stable. 
Next up was loose fitting all the principle mass items.  Batteries, motors, pump, even the lightweight mister box.   Still solidly stable, bobs back level on side prodding, and with waterline not too far off optimum allowing for the extra weight of hatches wiring and superstructure. 
The lighter 6V battery also helped, and I now have healthy scope to trim further using more lead shot if required.

Maybe now I can get on with building the actual boat?    O0
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HMS Skirmisher (1905), HMS Amazon (1906), HMS K9 (1915), Type 212A (2002), HMS Polyphemus (1881), Descartes (1897), Iggle Piggle boat (CBBC), HMS Royal Marine (1943), HMS Marshall Soult, HMS Agincourt (1912)

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Re: H.M.S. Polyphemus (1881), Historical Info
« Reply #231 on: January 19, 2013, 11:31:50 pm »

Wiring Redesign
 
I can no longer run the wiring between compartments in brass tubes along the keel ridge, Engel-style as planned, with one and a half cartridges of mastic in the hull.  I am now making small cutouts near the tops of the bulkheads, to be sealed with RTV afterwards.  The mass distribution appears solved, so I can now make up the wiring looms.. 

Additional Historical Information

   
Whilst researching for info on the ships badge / crest I came across this remarkable biography of W.H.May who commanded HMS Polyphemus 1881-84, and later went on to become Admiral of the Fleet.  Chapter VI gives interesting insights and further information on this ship.



http://www.archerfamily.org.uk/bio/may_wh.html

The 2,400 ton ship only had 500 tons of buoyancy to keep it as invisible as possible.  There were twelve 20 ton emergency drop keel weights in case a compartment became holed.  Remarkable insights into the early trials and tribulations of Whitehead torpedoes and submerged tubes.


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Re: H.M.S. Polyphemus (1881), Semi Submersible
« Reply #232 on: February 04, 2013, 12:47:21 pm »

Some more progress . . .
 
Lead Keel
 
  For ballasting trials the lead keel was held on with duct tape, so now had to be properly fitted in place.   After preparing the hull step and lead strips the later were attached in layers using impact adhesive, and bonded at outside edges with epoxy.  Another Isopon filler application was needed to blend in to the hull profile.



Bow Rudders

1/8 shafts were silver soldered to brass plates, then clad in thin ABS, shaped and detailed to the plans.  There is still quite a lot of work to do blending in the shaft mounting holes which have M3 washers to match the rudders for O ring bearing surfaces.  Also to be finished off is detailing the ram side plates and bow torpedo cap.
 
I have since discovered that these rudders were retractable, but no way am I going to attempt that as well !
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Re: H.M.S. Polyphemus (1881), Switches & Scockets
« Reply #233 on: February 10, 2013, 02:20:05 pm »

Some ongoing R&D work on Switches and Connectors
 
Focsle Under Deck
 
Cut from clear Lexan in same style as main under deck, with 40 mm section aft of the bow watertight hatch. 
Access cut-out just large enough to get to fwd battery and bow rudders mechanism.  Not fixed in yet.
I may lower the 40 mm section to main deck level.
 
 

Switches & Sockets

Having several power supplies I need them each separately switchable, plus charger access.

Component Shop do excellent SP on/off rocker switches with waterproof covers.  Later I found Maplin did SPCO illuminated switches that are a perfect fit for the waterproof caps.  Saves wiring in LEDs.  I intend to recess these in and seal with RTV.  I also need a 4P CO for the 24V, and have a found suitable switch with a waterproof boot cap.  NB:  CO switches allow either On or Charge positions.

Access caps / cover needed for the charging sockets.  I had tried Oasis bottle screw caps, but they were far too deep.  Nearest I could get were kids bubbles at 32 mm dia x 15 high.  I also found some soft rubber square end caps which were very low profile.  I have also been considering resin casting a rectangular hatch from a plug made from sections of a small Tesco food box.



Basically, I have 40  x  100 mm  to work in, although I could mount the switches on the main hatches.
Bottle caps would need to be part recessed in tubes as they have to be 10 mm max height to be flush with the underside of the focsle deck.

Interesting!

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Re: H.M.S. Polyphemus (1881), not quite a submarine
« Reply #234 on: February 10, 2013, 02:30:11 pm »

Do check the current draw on the illuminated switches: you might prefer to leave 'em dark.

Andy
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Bob K

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Re: H.M.S. Polyphemus (1881), not quite a submarine
« Reply #235 on: February 10, 2013, 02:42:08 pm »

Good point Andy.  No info on packaging or Maplin website, so I will have to wire one up and measure it.
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Re: H.M.S. Polyphemus (1881), not quite a submarine
« Reply #236 on: February 10, 2013, 03:05:27 pm »

If they are LEDs then about 20 MA max

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Re: H.M.S. Polyphemus (1881), Semi Submersible
« Reply #237 on: February 15, 2013, 10:03:18 am »

Gradual progress

 
  • Bow rudders mechanism now fully assembled and tested prior to electrics commissioning.
  • Focsle under deck fitted and sealed.
  • After further re-think switches and connectors panel will now be sloping between the raised F'o'c'sle and the Main Deck..
  • I have replaced the illuminated rocker switches with Arcolectric 1 pole c/o, and will add 3mm LEDs.  Turned out that the 3rd pin on the Maplin ones were not c/o but DC -ve for the light !
  • Finally managed to get a coaxial charger plug to fit the F14 Tx,.  Boy that is an unusual size.
  • With Tx charged and a temporary 4.8V Rx battery I can start commissioning the 40Mhz system.
  • The servo reverser Y lead works well.  As main rudder turns to left so do the twin bow rudders.
  • ACTion P94 twin ESCs fitted to aft of motors compartment.
Next will be getting the motors and 6V battery wired up. 
A lot of wiring in this ship, so I am taking it one step at a time. 
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Re: H.M.S. Polyphemus (1881), not quite a submarine
« Reply #238 on: February 15, 2013, 12:11:48 pm »

Hullo Bob K....it is good to read .....Planning, planning & yes  :-)) more planning.....
As you may understand I am firm believer in the 'ordered state' ....without such, how would we be able to understand the success's or and failures in our build efforts....... O0 ....Derek
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Re: H.M.S. Polyphemus (1881), not quite a submarine
« Reply #239 on: February 15, 2013, 01:02:05 pm »

Sincere thanks Derek.   Wading around is maybe a sign of being close to out of ones depth, hence the slow progress.  True semi submersibles are not done that often, especially by those of limited experience (tee hee!).   Lots of R&D, trawling through Mayhem and Google, breaking the problem down into bite sized morsels, and thinking several stages ahead.

Almost half this build involves totally new challenges.  Even when I get the hull operational the upperworks will be 100% scratch due to the unusual scale.  1/60
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Re: H.M.S. Polyphemus (1881), not quite a submarine
« Reply #240 on: February 16, 2013, 02:16:40 pm »

Comment from my stepdaughter (8) who is learning English


"Is it called scratchbuilding because you look at it and scratch your head lots?"
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Bob K

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Re: H.M.S. Polyphemus (1881), semi submersible
« Reply #241 on: February 21, 2013, 09:25:22 am »

Control Panel

First trial fit of the control panel.  This slopes backwards from the raised Focsle down to the Main Under Deck, which will be covered by the removable final decks.  The rocker switches are mounted on an alloy back plate.  A hardwood framework supports the sandwich that will be sealed with aquarium sealant. 

In the end I used the two soft rubber caps to plug the charging connector recesses.  On completion the wired assembly will be fitted and sealed in place.  The slope should hopefully discourage water laying over it, but in any case it is all waterproofed.
 

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Re: H.M.S. Polyphemus (1881), not quite a submarine
« Reply #242 on: February 21, 2013, 10:33:41 am »

Looks like a prop from a Gerry Anderson flick!:D

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Re: H.M.S. Polyphemus (1881), not quite a submarine
« Reply #243 on: February 21, 2013, 05:48:44 pm »

Looks like a prop from a Gerry Anderson flick!:D

Tee hee !  It does a bit  O0    The object was to keep all the power and control swiches, plus charging connectors, in one waterproof section to minimise removing watertight hatches.  LED's were added to give visual indication when the various voltages were 'on'.  I did try to use drinks tops, but ran out of space.  At least each bus section is isolatable for commissioning.
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Re: H.M.S. Polyphemus (1881), semi submersible
« Reply #244 on: February 25, 2013, 10:32:20 pm »

6V Electrics

  The 6V wiring is in and tested.  Big SLA, P94 controller, P19 BEC, rocker switch, charging connectors and LED.  DC wiring is run along the port side, through small slots at the top of the transverse bulkheads, which will be sealed with RTV.  C/O switches are used so batteries can only be charged in the off position.

   Switch / connector panel

I have just upgraded the MMB Mister for a throttle controlled variable speed fan.

Next will be the 12V and 24V circuits.  A bit busy, but that was my choice.
Servo leads will be routed opposite on the starboard side. 
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Re: H.M.S. Polyphemus (1881), not quite a submarine
« Reply #245 on: February 25, 2013, 10:58:30 pm »

Hi Bob K


Looking forward to seeing this on the water or should I say in the water. The work you have put into the development of the hull and all the equipment you deserve more than a pat on the back!
I don't know if you have read the book Early British Destroyers by Norman Friedman but the initial chapter goes into some detail about the Polyphemus and her development including suggestion of a sister ship to be built but never was. I'll fetch it out over this weekend and write up the info for if you have not got it already. Hope to see you at Wicksteed Park this year.
Regards


Nick B
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Re: H.M.S. Polyphemus (1881), not quite a submarine
« Reply #246 on: February 25, 2013, 11:24:08 pm »

Welcome back to Blighty Nick  :}
 
I don't have that book, so any specific info you have on this would be greatly appreciated.  Thanks.   I will be at Wicksteed at the end of May, but whether Polyphemus will be ready by then is in the lap of the Gods.  At best it could be a decked over hull.
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Re: H.M.S. Polyphemus (1881), semi submersible
« Reply #247 on: February 27, 2013, 08:53:08 pm »

More Electrics

  There is something very satisfying after checking wiring connections several times, you switch it on, and everything works. 
I doff my cap to ACTion once again, having four of their modules aboard this build.  The huge props turn nicely, in the right direction first time. 
The Deans Kondor motors have good torque at low RPM.

   Motors Compartment

Now was the time to tidy the cable runs so far.  A lot of servo leads. 
Three rudders with servo reverser.  Ballast tank controls.  Throttle controlled Mister fan.

   Mister Compartment

12V

Nice and simple.  The 12V air pump is operated by a servo cam microswitch, so it remains off unless you move the Tx stick to max up.  Just a charging socket and LED to add to the wired pump.

24V

Another change of plan.  I did get a 12 to 24V DC to DC converter, just to try it.  However it is too large and heavy to fit onboard.  Googling I found a medical mains charger with 24VDC output suitable for NiMh batteries.  This way I keep the weight in the workshop, and charge the two series connected 8 cell packs in situ.  Beats having twin 12V charging sockets plus 4 pole switch under the deck.

 
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Re: H.M.S. Polyphemus (1881), not quite a submarine
« Reply #248 on: March 01, 2013, 07:37:09 pm »

Hi Bob


Here is the info from British Destroyers From Earliest Days to the Second World War by Norman Friedman.


HMS Polyphemus was an alternative solution to combining torpedoes with the deployable fleet. Conceived a decade before HMS Vulcan she was a dead end because without large calibre guns she had no viable peace time role. Despite her conventional appearance she was semi submersible ship with a three part raft superstructure designed to float free if the main hull sank.


Polyphemus


Sartroius' ideas collided with those of DNC Sir Nathaniel Barnaby to produce the Royal Navy's first sea going torpedo vessel, the torpedo ram 'Polyphemus'. On 26 September 1874, apparantly on his own initiative, Barnaby proopsed an ocean going torpedo ship- he had been considering the idea for some time. The ship should be able to operate in whatever weather the ironclad batleships could fight, maintaining fleet spped for 10 hours. To keep her reasonably small, he wanted her to draw her supplies and relief personel from a larger ship with which she would be associated with (possibly even tow her on over long distances). At this time the only torpedo tube in service fired underwater, so Barnaby armed his ship with one submerged bow tube. He argued that current engine technology offered the sort of high sea going speed such a ship would need. Barnaby initially proposed a fast single screw 1560 tonner (200ft x 27ft) with most of her hull underwater, presumably to avoid exposing much of her side to gunfire. The design was practicable only if her machinery was no more than half as heavy as in  a conventional ship. Barnably cited Thornycroft's recent successes in building small high speed launches as proof that light weight engines could be built. Board action on Barnaby's design was deferred because promising experiments at HMS Actaeon showed that torpedoes could soon be fired from the broadside.  In June 1877 Barnaby sketched a new design for a 2060 tonner but the version he submitted was for a 2340 tonner  (250ft x 37ft x 24ft) and 5000ihp for 17knots. The ship was armed with one underwater bow torpedo tube (with 9 torpedoes) and with four broadside tubes (16 in total). Her main protection was the water covering most of her hull but its turtle back upper portion was armoured and she had 6inch vertical armour on hatchways. As built the flying  deck above the hull was built in sections to form rafts in the event that the ship sank, She was ordered from Chatham Dockyard in January 1878.
Polyphemus was probably the first torpedo ship for which high speed was crucial, she was intended to dash out of the mass of ironclads to close with enemy ironclads and torpedo or even ram them. Like the torpedo boats then being built, she needed unusually powerful boilers. Locomotive boilers were chosen because they promised the most steam for their weight, they had been used successful on land using clean water without condensors and they had been successful in torpedo boats. They could also handle a high rate of forced combustion, however, torpedo boats only used one boiler, Polyphemus required 10! A special supply of reserve fresh feed water was provided (50 tons), even with this reserve the total weight of machinery was 2cwt (224lbs) per ihp, compared with the usual 3.75cwt. Space occupied by machinery was also considerably less, as was the cost. The boilers proved disappointing, the Chief Engineer reported that on her full power trials she only developed only 4800ihp rather than 5500ihp expected, and it was only half an hour before her boiler tubes began to leak so badly that the ends put out fires were nearly put out before she could steam down the Maplin to the anchorage at Sheerness Harbour. The Engineer in Chief proposed replacing the boilers with more conventional boilers as used in the Comus and Satellite classes, which could be forced to get the required power. The ship was re-boilered and she was commissioned for limited torpedo trials. Polyphemus was rated at 5520ihp at natural draught (17.85knots) and at 7000ihp forced draught (18knots).
A second ship was ordered from Chatham on 30 December 1881 but cancelled it (it was not laid down) on 10 November 1882, shortly after Polyphemus was completed. Another was ordered from Chatham to be named HMS Adventurer on 6 March 1885 presumably as part of the Northbrook Programme but cancelled on 12 August 1885.


Hope this is of some interest


Regards


Nick B
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Nick B

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Bob K

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Re: H.M.S. Polyphemus (1881), semi submersible
« Reply #249 on: March 01, 2013, 10:20:25 pm »

Thank you Nick B

  I greatly appreciate your having taken the time to transcribe that information, adding more depth of detail about this unique experimental ship, a fascinating prototype vessel on so many levels.

A Technical Problem

Another bout of head scratching coming on, trying to get both ballasting controls operated by one throttle stick.  RH stick up/down, channel 2. 
   
  • Stick centred, everything off.
  • Stick upwards, cam operated microswich to turn on air pump to blow tanks.  No problem.
  • Stick downwards, actuator to operate air vent valve lever.
The later means translating half the servo rotation (~30 degrees) into 90 degrees of valve lever rotation.
Seems like this could require a bell crank of some kind.  Ideas ?
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HMS Skirmisher (1905), HMS Amazon (1906), HMS K9 (1915), Type 212A (2002), HMS Polyphemus (1881), Descartes (1897), Iggle Piggle boat (CBBC), HMS Royal Marine (1943), HMS Marshall Soult, HMS Agincourt (1912)
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