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Author Topic: Bob's H.M.S. Polyphemus  (Read 208380 times)

Subculture

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Re: H.M.S. Polyphemus (1881), not quite a submarine
« Reply #125 on: October 05, 2012, 08:07:39 am »

You don't need to spend hundreds of pounds to get reasonable CAD- plenty of free packages out there more than capable for what the modeller requires.

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Re: H.M.S. Polyphemus (1881), not quite a submarine
« Reply #126 on: October 06, 2012, 03:28:41 pm »

Have a look at http://www.bustedbricks.com   he will produce laser cut bits (I think he specialises in model railways) and from his website spiel it looks like he can produce from CAD drawings or use your own sketches to get his own (at extra cost).
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Bob K

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Re: H.M.S. Polyphemus (1881), not quite a submarine
« Reply #127 on: October 06, 2012, 07:03:17 pm »

The stage I am at is that the underdeck is ready for drilling and the 1m x 100mm hatch plate is marked out for drilling through both sheets clamped together to ensure the M3 fixings line up.  After this underdeck cutouts will be made with holes opened up for the nutserts, then individual hatches cropped from the hatch plate.  The black tape indicates bulkhead positions.
On its own a CAD / lasered hatch plate would not line up.



The special marker pens work well. 
Double sided tape used for initial bond, then clamps, then some 3mm acrylic rods as dowels to keep alignment whilst holes are drilled.
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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 #128 on: October 08, 2012, 02:44:51 pm »

75 sets of holes drilled today.  Hand-drilled through both panels to 2 dia, them opened up to 3.0 with the Rotacraft. 
Hatch plate removed.  Underdeck holes opened to 5 dia & csk for the nutserts.  All fits so far . . .

  Lexan hatch plate & underdeck, with protective film

One problem with an evolving design process is that procurement lags behind design.  The MIL std Neoprene turns out to be on ‘back order’ and may not now arrive for two to three weeks. 
In the mean time I had equipped myself with some ‘fresh’ HSS small drills, and been surprised that A4 lengths of 3 x 3 mm brass angle are over six quid each.   {:-{
So, I trawled around and found 500 mm lengths at over a Pound cheaper.  I now only need six lengths instead of ten.

Hatch cutouts next.   The risk of my messing everything up here is high  :embarrassed:
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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), Lexan cutting
« Reply #129 on: October 10, 2012, 12:28:18 am »

I did say I was going to report the complete story of the build.  Including the downs as well as the ups.

Progress has been quite good so far, apart from the dive system, and figuring out how to put the frame together whilst keeping everything vertical solid and square.  Using balsa boxes solved the later.

Today I have been attempting to cut the five apertures in the clear Lexan underdeck.  I have ‘discovered’ than Lexan is nowhere near as easy to cut internal shapes into as plywood or styrene of similar thickness.  Had it been styrene a sharp Xacto knife would have sufficed.

Pilot holes for corner radii.  Thread coping saw blade through hole.  I would have thought it just needed a careful hand and steady eye.  
Darn !  The material grips the blade in an almost continuous jam, and making blade direction almost uncontrollable.

A lot more thought needed.  I might end up making over 1,000 chain drilled holes, then having to file it.  Not very neat  {:-{
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Re: H.M.S. Polyphemus (1881), not quite a submarine
« Reply #130 on: October 10, 2012, 06:04:57 am »

Ty a coarser blade in your saw.

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Re: H.M.S. Polyphemus (1881), not quite a submarine
« Reply #131 on: October 10, 2012, 06:06:15 am »

That was supposed to be TRY a coarser blade.
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Re: H.M.S. Polyphemus (1881), not quite a submarine
« Reply #132 on: October 10, 2012, 07:05:05 am »

If I remember correctly lexan heats up quite quickly causing it to soften and this makes the blade stick
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Bob K

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Re: H.M.S. Polyphemus (1881), not quite a submarine
« Reply #133 on: October 10, 2012, 08:12:45 am »

Thank you.  A courser blade might work, if there is more teeth offset outside the blade thickness.

The Lexan may well be heating up and expanding, making the cut slot tight.  
I used a power jigsaw to rough out the outside profile, but cannot use anything like that for inside profiles.
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Re: H.M.S. Polyphemus (1881), not quite a submarine
« Reply #134 on: October 10, 2012, 10:28:43 am »

Get a small cup of water, you can mix in a little soap too if you like. Brush this on the work with an old paint brush as you cut. The water helps cool the work, and the soap helps the blade slide, the water is the most important bit though.

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Re: H.M.S. Polyphemus (1881), Lexan cutting
« Reply #135 on: October 17, 2012, 10:15:33 pm »

That's wierd, I had posted an update on the 15th which has now dissapeared  :((
Maybe dropped out during the site upgrade.  If I can remember it right:- 

After trying several typres of coping saw blades, with and without water, the blades still kept jamming and wandering the cut badly in trying to cut the internal appertures. 
Finally I tried an X-Acto keyhole saw blade which was stiffer so less jamming, and seemed to cut straighter if angled at 30 degrees to the material. 



Slowly and carefully.  20 more cuts, totalling approx 2 metres.

PS:  Hopefully new photos with good news tomorrow.  Underdeck almost done.
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Re: H.M.S. Polyphemus (1881), not quite a submarine
« Reply #136 on: October 17, 2012, 11:21:02 pm »

Bob,
Have you tried liquid soap on the cutting blade.

Bob
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Bob K

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Re: H.M.S. Polyphemus (1881), not quite a submarine
« Reply #137 on: October 18, 2012, 12:44:40 am »

Hi Bob,

All the cutting done now.  Photos tomorrow when I've fitted the nutserts. 

Water did not help, and when I tried a little washing up liquid it partly disolved the indelible marker pen lines on the protective film.
Challenging stuff Polycarbonate sheet  :embarrassed:
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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), underdeck
« Reply #138 on: October 18, 2012, 08:27:41 am »

Clear Lexan is not a material I have worked with before, so this is all a learning curve.

The X-Acto keyhole saw worked reasonably well, but still a lot to finish with files.  I have been taking this very carefully against visions of snapping the polycarbonate across the thinner sections. 
The Workmate was handy in clamping and supporting the part over maximum length.

Eventually I had all five cutouts made.  Phew !    Nutsert holes were lightly countersunk to give a flater profile for the heads.  Remove protective film both sides of deck.  Recheck alignments before fitting the 75 nutserts with epoxy.  Working access should be infrequent, mostly one compartment at a time, but one blind nutsert per battery hatch was drilled through to provide a vent with screw removed for charging safety.  (SLA and NiMh.)





Cutting out the individual predrilled hatch plates is much easier.  Straight external cuts.

No hurry, the special neoprene will not arrive for another two weeks.  However the most critical stages have now been done.  The internal structure is in clear material for full visibility.
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Re: H.M.S. Polyphemus (1881), not quite a submarine
« Reply #139 on: October 18, 2012, 06:20:22 pm »

many years ago we used to build model car chassis from 1/8" clear lexan, bending it was very tricky but doable, cutting as you say very difficult, we learned to drill corners and cut to the holes as sharp corners allowed stress fractures to start propagating, but then the stresses involved with the cars were very high.
Grendel
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Re: H.M.S. Polyphemus (1881), not quite a submarine
« Reply #140 on: October 18, 2012, 08:59:47 pm »

That's interesting Grendel.  Lexan is a new material to me, but at least the learning curve has been useful.  I did start with 5 dia holes on the internal corners to start the saw cuts in, but squared them off finishing.  Maybe I should have left radii in as you said as this stuff is not only tough and durable, but is also hard and quite brittle.
If I do a similar exercise again I will seriously consider all-CAD and water cutting.

After the hatches I have to make up the f'o'c'sle underdeck and hatch.  I will use corner radii for that cutout.  That compartment is for the twin bow rudders.

The only other major part in clear Lexan is the removable main deck, mainly because I already have the sheet and it was easy to trace the hull profile from the finished underdeck.
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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 #141 on: October 18, 2012, 09:07:09 pm »

I dont think you will have any problems in your application, we were using it to form the main chassis for the cars, onto wich everything was bolted, so any hard knocks and flexture to the chassis caused stress, especially twisting the whole chassis. so weak points were to be avoided, other materials used were sheet aluminium and fibreglass board, but the lexan was superior for strength and weight.
Grendel
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Bob K

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Re: H.M.S. Polyphemus (1881), F'o'c'sle underdeck
« Reply #142 on: October 20, 2012, 05:56:09 pm »

H.M.S. Polyphemus (1881),  F'o'c'sle underdeck

F’o’c’sle underdeck completed, plus all six hatches, including the new f’o’c’sle hatch for access to the twin bow rudders.  I am awaiting delivery of the special neoprene gasketing and s/s csk Allen screws.



The F’o’c’sle is slightly raised which gives opportunity to make it a lift off deck to give easy access to the waterproofed charging connectors and switches.  
Separate connectors and sealed rocker switches for each of the three circuits.  Motors + electronics, pumps, and mister.



Wiring runs between compartments at keel level will be in brass tubes (Engel 212 style) with ends sealed using RTV.
Unlike submarines which need to be pressure-tight I am aiming for a system that allows for frequent sailing without having to keep dismantling sealed parts for charging and on-board manual controls.  

I am not far off the point where I can start to install prop shafts motors and rudders etc.  Frame assy and underdecks will not be sealed into the hull until internal fittings, slots and holes, are all in.

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Re: H.M.S. Polyphemus (1881), not quite a submarine
« Reply #143 on: October 20, 2012, 07:29:00 pm »

What a lot of people us is the bottle tops from fizzy drinks. these are totally water tight once done up, but are quickly released if access is required to a switch or plug. They're usually bonded into the plastic lid.

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Re: H.M.S. Polyphemus (1881), not quite a submarine
« Reply #144 on: October 20, 2012, 08:07:43 pm »

That's a neat idea.  I like lateral thinking  O0
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Re: H.M.S. Polyphemus (1881), not quite a submarine
« Reply #145 on: October 21, 2012, 11:55:10 am »

You can probably solvent weld them onto the lexan lids, most drinks bottles are made from Pet-g, which is an easy to mould thermoplastic which doesn't absorb much moisture (important when you're using them for drinks). Some might be polypropelene- don't use those, it doesn't bond well.

Try one on a bit of scrap. Trim the bottle back to the neck, then sand on a board to give a nice flat surface. If you want belt and braces you could run a bit of acrylic adhesive or sealant around the bond.

 Oasis bottles give nice large lids, enjoy contents and recylce packaging!

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Re: H.M.S. Polyphemus (1881), Prop shafts
« Reply #146 on: October 24, 2012, 03:45:49 pm »

Prop Shafts

This is only the second set of shafts I have installed, and hopefully I’ve learned from the previous fit. 
I am using Raebosch watertight shafts.  A bit more expensive but well worth the extra.

Lots of measurements taken, inside and out, marking out hull from plans dimensions. 
The big 48 mm props have to be close into the hull profile, with motors positioned within the compartment level and straight. 



‘A’ frames were cut to suit the hull and slots made using my Rotacraft.  From here sight lines were established parallel to the keel.  Hull intersection points marked out with long centrelines as after the initial hole it is important to keep the developing slot centred and in line.  Holes drilled, and opened out into the required ellipses with round files.  File starts off perpendicular to the hole, then gradually angled to create the ellipse. 



A balsa box that was used for frame construction came in handy to positionally locate the inboard shaft ends



The shafts need shortening.  3 mm off the M4 threaded end, then the brass tube and stainless shaft to suit motors & UJ's.  The inboard bearing sleeves secure with Loctite. 
Recheck evertyhing, hold shafts in place with with Bluetack. 
When all OK set in with epoxy, using reinforcing tape inside, and finish with filler.
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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), Prop shafts
« Reply #147 on: October 24, 2012, 05:03:23 pm »

Prop Shafts

The propellers were really big for a ship this size, as this dry dock photo illustrates.

 

The props protruded quite a long way outside the rear hull profile, hence the mooring fender booms in the picture below.  Note also the circular section hull required a fending pontoon.



When the shafts and motors are fully installed I will start work on the three rudders.
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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), Bow remodelling
« Reply #148 on: October 28, 2012, 07:04:27 pm »



Fitting the prop shafts went better than expected.  With so much inner shaft exposed it made the free running alignment of the much shortened brass outers with ‘A’ frame bearings a bit ‘hairy’.  All now epoxied filled and sanded.

Bow remodelling

Three rudders.  Start with the bow pair.  However, the underside of the bow looked far too narrow and steep sided to get them on a scale pitch apart. 
The photos below indicate the problem.  The original lower bow was wider and more rounded underneath.  Some remodelling was required.



To replicate the armoured cutting edges I made up brass plates and secured them to the hull using brass tube for strength.  Not a huge additional volume involved, so using the metal plates as a guide I will remodel the shape gradually building up using car body filler.



It may look ‘lethal’ for a boating lake, but so does reversing with overhanging two inch props. 
Double 0 License applied for.


Bob
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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 #149 on: October 28, 2012, 07:23:54 pm »

Very interesting build Bob........but are the props as shown counter handed to the real vessel?......................Derek
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