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Author Topic: Bob's H.M.S. Polyphemus  (Read 208379 times)

rmaddock

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Re: H.M.S. Polyphemus (1881), not quite a submarine
« Reply #75 on: July 19, 2012, 02:14:16 pm »

I think this is a fantastic build Bob. I'm enjoying it greatly.  You've got a very unusual but fascinating subject and your doing a very hands-on build too. No buying all the trick bits in a magic black box for you eh?
Keep it up!
 :-))
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joppyuk1

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Re: H.M.S. Polyphemus (1881), not quite a submarine
« Reply #76 on: July 19, 2012, 03:50:05 pm »

The top picture was the one I mentioned. Definitely shows a need for accurate watertight access if your planning this sort of thing.
IJ
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Bob K

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Re: H.M.S. Polyphemus (1881), not quite a submarine
« Reply #77 on: July 19, 2012, 04:09:59 pm »

rmaddock:  Thank you.  I am having a lot of fun with this one. There were no 'magic black boxes' in 1881 either  O0

Ian:  Fascinating reading material just arrived, I am learning even more about this ship.  Decks awash, sloping armour protected the base of the funnel and conning tower.  The flying deck was on a maze of pillars and largely sacrificial so the ship was very hard to damage by gunfire.  A brilliant concept that was overtaken by the advent of rapid-training quick fire guns which effectively made her obsolete as she became operational.  A common fate in that era.

Hull innards have to be treated as if a submarine, watertight yet in accessable compartments.  Water will tend to flow over at speed.
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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), not quite a submarine
« Reply #78 on: July 19, 2012, 04:11:05 pm »

I just love all the old photos of her - brilliant :-))

Dave
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Re: H.M.S. Polyphemus (1881), not quite a submarine
« Reply #79 on: July 19, 2012, 09:28:47 pm »

Blow time sounds about right on 6 volts. I said about 15-20 seconds on a 12 volt system, so 40-45 seconds is about double that- the motor won't be working as efficiently on the lower voltage. I reckoned the specification of 12-15 litres per minute was optimisitic for that pump, I have one of pretty much identical size and it shifts about 8 litres a minute, which is still good going considering it only draws a few watts.

Flood rate sounds very slow however. To get an accurate assessment you should partially submerge the bottle ,as the hull would be, and sticking a bit more weight (more or bigger spanner) underneath will help matters too.

Bob K

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Re: H.M.S. Polyphemus (1881), not quite a submarine
« Reply #80 on: July 19, 2012, 10:20:11 pm »

Blow time sounds about right on 6 volts. I said about 15-20 seconds on a 12 volt system, so 40-45 seconds is about double that- the motor won't be working as efficiently on the lower voltage. I reckoned the specification of 12-15 litres per minute was optimisitic for that pump, I have one of pretty much identical size and it shifts about 8 litres a minute, which is still good going considering it only draws a few watts.

Flood rate sounds very slow however. To get an accurate assessment you should partially submerge the bottle ,as the hull would be, and sticking a bit more weight (more or bigger spanner) underneath will help matters too.

6V was worth trying, but the full 12V should improve things.  On the test I was using aquarium 4 mm bore tubing, but it would go better with the full 1/4".  Neccessary elbows and tees will restrict bore a bit.  
Batteries for 12V, 6V (motors), and 24V (mister) makes for interesting wiring.

The Blagdon ball valves do their job very well, but are only 2.9 mm bore.  I was hoping air would vent more easily than pumping water out, but it was slower than expected.  Finding a larger airtight stainess ball balve with a very easy turning handle would not be easy.

I love high tech solutions:  Fit a heavier spanner   :-))-   LOL !  I will try that.

PS:  HMS Warrior was still on the active fighting list in 1881, although 'only' 20 years old.
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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), not quite a submarine
« Reply #81 on: July 20, 2012, 07:10:10 am »

Festo do ball valves with larger diameters, all compatible with water- http://alshobbies.com/shop/search.php?Desc=Festo+Ball+Valve+with+Arm+-+4mm

But to be honest I doubt the valve is the restriction, it's low pressure plus the drag of the holes where the water come in that slows things down. If you try weighting the bottle down to at least 50% of it's displacement, then open the valve, I think you'll get a much faster dive time.

Regarding all those voltages, would it not be wise to ditch the 6 volt motors for 12 volt, and run the booster I linked to earlier? Then all you need is one 12 volt pack. You could use the three cell lipo pack that didn't fit the sub driver.

Bob K

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Re: H.M.S. Polyphemus (1881), not quite a submarine
« Reply #82 on: July 20, 2012, 12:23:57 pm »

The key advantage of the stainless Blagdon air valves is they take very low effort to turn, making servo operation possible.  You are probably right about low air pressure, and I will try that.  The model will need about 20 lbs of equipment plus ballast.  To half submerge a 2 litre plastic bottle will take 1 kilo.

6V is needed to turn the two inch props slowly, otherwise I will be into more expensive and noisy reduction drives.  I have low RPM high torque Kondor motors from Deans which are made for these kind of applications.  As I wrote before, I am reluctant to have a large RF coil amongst the Multiplex 40Mhz Rx and electronics.  So multiple batteries that I can charge in situ from a single QD sealed access hatch seems the best operational compromise.  Batteries make good fixed ballast anyway.

Hull Slots

Planning ahead, I have made up a sample lozenge shaped sponge plug with a central mandrel, long screw with pop rivet washers, that I can insert into the hull slots before spraying the hull.  This is to prevent paint spraying over the inside faces of my clear bulkheads.


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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), not quite a submarine
« Reply #83 on: July 20, 2012, 01:06:51 pm »

The Festo valves are used a lot by submariners in place of pinch valves. They work fine with servo actuation.

You can use o-ring belts and pulleys for reduction- cheap and quiet as a mouse. Also it removes the need for couplings, so that's a cost saving. You can also get low revving motors for 12 volt operation. Engel do a 500 size motor that does about 500 RPM per volt. It's the same one you have in the 212, and is also used in their Lafayette model.

A switchmode supply can be mounted inside a grounded steel box, if noise proves to be an issue.

Bob K

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Re: H.M.S. Polyphemus (1881), Lexan bulkheads
« Reply #84 on: July 23, 2012, 06:32:18 pm »

Lexan Bulkheads
I finally managed to cut out the 3mm clear Lexan polycarbonate bulkheads from the jig template.   Multiple scoring on both sides would not create a snapable break line, so the profile was marked onto marking tape over the sheet, then clamping the sheet down I cut it using my new Bosch PST 900 jigsaw.  The jigsaw has a blower and lamp which helped.  Then it was a junior hacksaw for the small radii and finishing off with a rasp file.


Max bulge tank dimensions are 820 long, 50 wide and 90 deep.

Now I am making progress.  I will leave the protective film on until final fitting.  With the panels taped in position and my balsa jig I can then start working on the 100 wide transverse bulkheads, which are only curved at the keel end.

Ballast test jig
I tried this again but with ½ kilo ballast on the bottle.   It took five seconds longer to blow the tank, but submerged in only 40 seconds.  OK, so valve sizes look about right. 

-------------------------------------
Sorry, but no way am I going to fit a huge 11V LiPo underwater then fill the boat with ‘dummy’ SLA’s for ballast.  SWMBO will not let me charge LiPo’s indoors, and it can't be charged in situ.  Whilst the Engel 540-12 from my 212 is an excellent motor it runs faster than my Kondor’s on 6V, and too fast on 12V for big slow props.  I really don’t want to get into fabricating ‘O ring’ belt drives just to compensate for not using the big 6V SLA that will be on board anyway.
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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)

Bob K

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Re: H.M.S. Polyphemus (1881), Victorian Propellers
« Reply #85 on: July 27, 2012, 01:01:56 pm »

Victorian propellers

My special Victorian propellers have arrived from Swan Precision Castings (Prop Shop) and they really look the biz’.   ‘Crocus’ bladed with big onion bosses.  Very nice job.   
Slightly smaller than scale at 48 mm, will hopefully make them a bit less vulnerable when docking.  They do stick out well beyond the hull profile at the stern.



These complete the internal and running equipment for the ship.  Batteries and electronics were sourced a while back, as were the Raboesch watertight prop shafts, motors and pump etc.  Transverse bulkhead positions and static ballasting have been carried out specifically for this equipment set.

Re my last post:  Comments are appreciated, but suggesting I effectively junk all internals are not really helpful.
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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), not quite a submarine
« Reply #86 on: July 27, 2012, 05:27:27 pm »

You won't break those- silicone bronze, tough as old boots.

bikerdude999

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Re: H.M.S. Polyphemus (1881), not quite a submarine
« Reply #87 on: August 15, 2012, 02:12:45 pm »

Any more progress on this build? I'm finding it very interesting!
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Bob K

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Re: H.M.S. Polyphemus (1881), not quite a submarine
« Reply #88 on: August 15, 2012, 06:12:33 pm »

Slight delay in progress, sorry, I've been epoxied to the television enthralled with Team GB's Olympic successes.   :-))

The internal bulkheads framework is proving to be a bit challenging.  Having completed the side bulkheads I am working on a dozen Lexan and Marlon pieces, much of which must fit exactly as a 'drop in' assembly.  Catch 22 is that some bits should ideally be created in situ so some headscratching involved to work out the optimum method for ensuring it all goes together precisely when dropped into place, with top edges exactly level for the under-deck.  The balsa jig helps, but the side bullheads have a small curve.  Anti-slosh baffles will be fitted direct to the inside of the hull bulges as these can have slight gaps to the main framework.
When the framework is done I can cut the under-hull water slots, prop shaft slots, and mountings for the three rudders.
Top faces of the ballast chambers will be done last, then after checking for fit it all needs to be epoxied into the hull.  I may do the under-deck in several sections to ensure it is water tight, with all its access plate holes and blind fixings.

Please bear with me, this has become a bit of a 3D jigsaw puzzle !!!!   %%  %%
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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)

bikerdude999

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Re: H.M.S. Polyphemus (1881), not quite a submarine
« Reply #89 on: August 15, 2012, 06:44:46 pm »

Thanks for the update, sounds like a huge headache! Will you be taking it to the model boat show at Warwick? Would love to see this model in the 'flesh'.
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Bob K

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Re: H.M.S. Polyphemus (1881), not quite a submarine
« Reply #90 on: August 15, 2012, 08:37:27 pm »

Not really a 'headache', just an interesting build sequence that I'm trying to work out an optimum solution for.  No plans to take the duck to water yet, this one will take longer than my previous builds.  No fun or challenge otherwise  {-)
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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), not quite a submarine
« Reply #91 on: August 16, 2012, 07:34:50 am »

If you want an exact 'imprint' of a curved area, and using soft wire to obtain the shape isn't cutting it, then I use the following method.

Tape off the required area (parcel tape is good). Apply a release agent to the tape, this can be PVA (not the glue the release agent used for GRP work), wax or even a smear of vaseline. Cut out a rough template of the shape you want, plywood, plastic sheet, or balsa is good. Slather the part where you want the shape in polyester filler, and squish onto the taped off area. Allow to cure for a few minutes (a hair dryer will speed the cure) then pull it away- provided you've been thorough with the application of release agent the part should separate easily. PVA will be more tenacious than grease or wax, application of little water (brush it in) can help here.

Then remove the tape, and you should have a nice clean area, and a perfect template to use for marking out the lexan parts.

Bob K

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Re: H.M.S. Polyphemus (1881), not quite a submarine
« Reply #92 on: August 16, 2012, 09:58:58 am »

Not really a headache, just trying to work out an optimum sequence for this part of the build.  No plans yet to take the duck to water, this will be a longish build. Challenges are part of the fun.
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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), not quite a submarine
« Reply #93 on: August 16, 2012, 01:12:23 pm »

You alright there Bob, you're repeating youerself matey!

Bob K

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Re: H.M.S. Polyphemus (1881), not quite a submarine
« Reply #94 on: August 16, 2012, 02:27:23 pm »

You alright there Bob, you're repeating youerself matey!

Thats strange.  I had replied yesterday but noticed today it was not showing even after refreshing the page, so I wrote it again.  Weird !

Thanks for the tips on managing some of the internal structure.  Ideally I am trying to get as much framing done as I can as a removable subassembly before drilling the numerous hull slots.  Then I can hard-resin it in with the interconnecting brass tubes etc in place.  Tubes are a) balance flow pipes between ballast chambers, and b) wiring conduits between WTC compartments.  Hopefully dousing the ends of the later in RTV sealant will be sufficient.
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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), not quite a submarine
« Reply #95 on: August 16, 2012, 04:48:49 pm »

You can use something like Sikaflex 221 if you really want to be sure. This is a very strong mastic adhesive that is totally waterproof and very high tear strength.

Bob K

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Re: H.M.S. Polyphemus (1881), not quite a submarine
« Reply #96 on: August 20, 2012, 11:07:23 pm »

Just go back from a holiday visiting family in N Ireland.  I will try that Sikaflex 221 sealant, having looked it up on Google.
Now I am back home focus will be on the internal framework build. 
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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), not quite a submarine
« Reply #97 on: August 22, 2012, 05:52:22 pm »

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Bob K

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Re: H.M.S. Polyphemus (1881), internal structure
« Reply #98 on: August 25, 2012, 04:03:26 pm »

Internal structure

A lot of head scratching resulted in some lateral thinking.  Instead of looking at the problem as building a ‘House of Cards’ inside a partially enclosed volume I switched to thinking in terms of the space volumes to be enclosed.  So I built the main volumes as balsa sheet boxes, to locate and temporarily attach the watertight panels on to.  That way it could be made solid, square, and with vertical planes.  Once completed the balsa ‘volumes’ would be removed and the framework secured into the hull.

It has taken a while to reach this stage as numerous other considerations have to be factored in, such as how large the access apertures need to be for the watertight hatches.  I now have suitable M3 stainless blind nutserts, a key dimensional factor for the hatch apertures to fit and access internal equipment.

The first balsa box replicates the main 6V battery compartment, including space to twist and lift out the battery.  The second box represents the mister chamber, again with lift out clearance.  A strip of lead sheet was used to copy lower hull profile sections.



Now assembly can start, knowing dimensions are correct and all is square.  Tape was used to locate panels to boxes, whilst making sure panel edges seat well into hull profile.  Note mini spirit level using balsa strips.



Moving outwards, the next two chambers only required partial balsa boxes to set dimensions and ensure squareness.  With four of the seven chambers the framework is quite solid and removable.



Eventually the panel joints can be epoxied, then the tape and balsa boxes can be removed.  It is intended to seat the framework onto beads of Silkflex 221 air curing sealant adhesive, after all the slots and tubes etc have been built in.

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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)

rmaddock

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Re: H.M.S. Polyphemus (1881), not quite a submarine
« Reply #99 on: August 26, 2012, 07:27:46 pm »

I like a bit of lateral thinking. Well done that man  :-))
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