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PostPosted: Wed Jan 29, 2014 3:33 pm 
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Hi all

I thought some of you might be interested in my latest build. I'm still struggling along with my 1/48th scale scratch build of the Imperial Russian torpedo gunboat "Kazarski" 1890, which has moved on, but only at a "glacial pace".

During 2013 I decided I needed to build something smaller and less complicated, to relieve the boredom of the hull plug preparation on this Russian vessel.

I looked at some plans and photos I owned of those wonderful little picket boats the Royal Navy (and other navies of the world) used around 1890.

I decided that I had sufficient info to build a decent "working" model at my chosen scale of 1/48th. I also concluded that a little model like this would compliment my other 1/48th scale vessels both on and off the water. So I started by transferring some basic out-lines to some nice pieces of lime wood (bass wood) in the workshop. This idea was not to make the model out of the wood but out of 1.5mm thick high impact polystyrene. The wood was to be used as a mould or plug for use in my vac forming machine.


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File comment: RN Twin funnel picket boat c1900
Picket boat 1900.jpg
Picket boat 1900.jpg [ 155.01 KiB | Viewed 4348 times ]

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PostPosted: Thu Jan 30, 2014 2:15 pm 
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Location: Dumfries, Scotland
Hi all

The huge advantage of basing this model on a series of vacuum formings is that, having manufactured a mould to "form over", the finished hull is light weight, 100% waterproof, easy to glue together and there in no internal strengthening to get in the way of fittings and RC gear. Yes I did have to invest some time in manufacturing the mould, but not much more than building a one off wooden hull. My vac forming machine is not large and the picket boat hull length just about fitted when placed diagonally, leaving space around the hull which could accommodate other fittings and deck detail. The two vac formed sheets of 1.5mm polystyrene are approx 300mm square.

The pictures show the two moulds (port and starboard). They are designed onto a base of 10mm medium density fibre board (MDF), with the main hull halves made from lime wood and all the other components manufactured from a type of "pattern makers" carving resin called "Conform". All components were stuck together with super glue. If you look close you can see the base board is covered with 2mm holes to ensure no air is trapped when the vacuum pump is turned on.

I could have just formed the hull halves on their own, but as there was space I tried to cram in as much as possible and therefore not waste the plastic around the edge.

Arranging the fittings was problematic as if they are too close together, the larger items can create "webbing" in the plastic. This creates webs like a bats wing and ruins the finished product.

I included a motor mount in the vac formings as it is strong and light weight. I designed this motor mount to carry a standard sized servo motor. In practice I fitted an even smaller motor which was more suitable and still fitted onto the mount, but more of this later.


Attachments:
File comment: Vac forming mould.
001.JPG
001.JPG [ 153.17 KiB | Viewed 4305 times ]
File comment: Other half of the vac formed hull and fittings.
002.JPG
002.JPG [ 109.71 KiB | Viewed 4305 times ]
File comment: Vac formed boiler room roof (close up).
003.JPG
003.JPG [ 123.94 KiB | Viewed 4305 times ]

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PostPosted: Thu Jan 30, 2014 5:34 pm 
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Hi all

I thought this might be a good point to put in a little historic and technical info about these “work horse vessels” for those of you who are not familiar with them. Please feel free to correct me if you think I’m talking out of my elbow.

These 56 foot picket boats were built from 1887 to around 1900 when they were replaced with 50 foot boats of a similar design. Many lasted through till the First World War and beyond.

Generally these vessels were based on-board capital vessels and deployed by being swung out on a large crane. The deck structures had 3 little hatches which allowed steel lifting cables to be attached directly to shackles bolted to the keel. The vessels weighed around 20 tons, so hoisting them out was no simple task.
The hull was wooden construction (double layer diagonal planking?). The boiler room roof and forward crew accommodation roof and “fustrum” (gun mount) were steel.
Twin funnel picket boats differed little from the contemporary single funnelled ones apart from the funnels and slight changes in the boiler room roof. The advantage gained from the twin funnels was better forward visibility for the helmsman.
Armament was a single 3 pound QF gun mounted forward and from 1900 a Maxim machine gun on the cabin roof. This replaced a 5 barrel rifle calibre Nordenfeld gun. In service the QF gun was rarely fitted as the additional weight (nearly 7 CWT) pulled the bows down in the water. They could also carry two 14inch torpedos in dropping frames.

These picket boats were built by an assortment of companies and therefore differed slightly in detail.

Colour schemes varied depending on which capital vessel they were based, theatre of operation (e.g. Far East Station) and time period. Vessels from 1912 tended to be grey.

I highly recommend two books as further reading. “Steam Picket Boats” N.B.J Stapleton and “The Boats Of Men Of War” W.E. May.

More build details of my model in the next post.


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PostPosted: Fri Jan 31, 2014 8:24 am 
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<sigh> there is a real one for sale in the US that served on Hood and Renown. My wife says I can't have it unless we can live on it, and it's far too small for that. It was converted to diesel but I would convert it back to steam.


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PostPosted: Fri Jan 31, 2014 9:13 am 
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Glen

Wow real history for sale. If I had the money I would certainly click "add to basket" if I saw one on the market. There are so few of these things left. The book I recommended by Stapleton has photos of dozens of them lined up at a post WW11 breakers yard. There is one preserved in the UK with a contemporary boiler and steam plant.

Looks like I'll just have to make do with my working model (sigh).

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PostPosted: Fri Jan 31, 2014 9:59 am 
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Location: Liverpool
Hi Steve great subject and superb model. Any one wishing to build an RN picket boat I can certainly recommend NBJ Stapleton's book Steam Picket Boats . Plenty of photos and good illustrations but also an excellent reference appendix . I keep saying one day I'll build a picket boat but that's for another time.
Dave Wooley :thumbs_up_1: :thumbs_up_1: :thumbs_up_1:


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PostPosted: Fri Jan 31, 2014 2:07 pm 
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Hi Dave

Thanks for the comments. The Stapleton book is great reference material, but I love the chapter where they just go off to an old Navy breakers yard, buy a picket boat, then proceed to sail it along the south coast of England and up the River Thames. The things you could get away with in 1949! I think if you attempted anything like that today you would certainly end up in court having failed to complete the correct "Health and Safety Assessment forms"!

Anyway back to the model.

Having made the moulds to "form over", I took them off to the workshop and warmed up the vac forming machine. After a few minor adjustments to the mould I managed to produce a pair of crisp detailed vac formings. Producing the moulds and getting the machine to work accurately and consistently is more of an art than a science but when it does work it's very satisfying.

The pictures show the first formings off the mould. I have cut them roughly out of the 300mm square sheets as this will make life easier when it comes to removing the remainder of the waste material. The smaller individual parts will be labelled and identified later.


Attachments:
File comment: Individual vac formed components.
IMG_1180.JPG
IMG_1180.JPG [ 153.8 KiB | Viewed 4227 times ]
File comment: Close up of the main picket boat components.
IMG_1181.JPG
IMG_1181.JPG [ 134.61 KiB | Viewed 4227 times ]
File comment: The vac formed motor mount is shown centre right.
IMG_1182.JPG
IMG_1182.JPG [ 109.19 KiB | Viewed 4227 times ]

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PostPosted: Fri Jan 31, 2014 7:21 pm 
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Hi all

I should have posted this picture earlier as it shows one of the two 300mm square vac formed sheets, this one containing the starboard hull half and boiler room roof etc. I hope it also shows how the mouldings look fresh out of the vac forming machine.

In the next post I start the assembly.


Attachments:
File comment: Fresh out of the vac forming machine.
003.JPG
003.JPG [ 155.09 KiB | Viewed 4214 times ]

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PostPosted: Sat Feb 01, 2014 12:09 pm 
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Hi all

Next I used a sharp scalpel to carefully score around the hull halves and remove the waste plastic. I had previously marked out the shape of the keel and bow reinforcing timbers onto some 2mm thick mahogany. These I cut out with a fine fret saw.

The inside of the hull mouldings, where the keel and bow timbers fit, was rubbed down with fine grade abrasive paper. This ensures that the CA glue keys well to the plastic and also speeds up the setting time. These timbers add greatly to the rigidity of the hull.

The timbers were glued into one hull half and left to set before the two hull halves were assembled.


Attachments:
File comment: Hull half, keel and bow reinforcing timbers and ESC/receiver tray.
007.JPG
007.JPG [ 151.6 KiB | Viewed 4186 times ]
File comment: Keel and bow timbers glued in place.
004.JPG
004.JPG [ 117.84 KiB | Viewed 4186 times ]

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PostPosted: Sat Feb 01, 2014 5:24 pm 
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Wow, that's great and fast!
I never vac formed anything and I always see people using 0.5mm sheeting. I was wondering how this was going to work with 1.5mm thickness? I guess you needed a lot of heat or just a longer period at lower temperature?
Anyway the result looks promising so far.
:thumbs_up_1:

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PostPosted: Sat Feb 01, 2014 6:13 pm 
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Location: campbell river.b.c canada
hey I realy like your vacuum forming .looks very good


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PostPosted: Sat Feb 01, 2014 6:43 pm 
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Hi Neptune

My vac forming machine is an old British made one which I bought from a design studio that had closed. It's not huge, but probably bigger than most hobby versions now available.
The high impact polystyrene (HIP) used here is 1.5mm thick, but is probably reduced in thickness to around 0.75mm as it is drawn down over the mould. I often use 1mm plastic for smaller fittings (vent cowls etc).
There are lots of tricks and short cuts to learn with these machines and initially you waste a lot of plastic making mistakes, but when you get the hang of it, the possibilities are nearly endless. They are very useful for larger curved or strangely shaped structures, ships boats etc.
The picture shows the two funnel casings and large ventilator that I vac formed for the German WW1 torpedo boat.This is covered in more detail on this forum under scratch builds.


Attachments:
File comment: Vac formed funnels and ventilator.
IMG_0480.JPG
IMG_0480.JPG [ 127.5 KiB | Viewed 4165 times ]

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Last edited by PICKETBOAT on Sun Feb 02, 2014 12:02 pm, edited 1 time in total.
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PostPosted: Sun Feb 02, 2014 5:43 am 
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Hi all

I used Revell solvent adhesive to stick the two hull halves together, holding them in place with tape, spring clamps, rubber bands etc. The adhesive should only be applied to the points where plastic touches plastic (not on the wooden keel and bow timbers). Leave this to set overnight before running plenty of medium thickness CA along the wooden keel. Tip the hull forward and backwards so that it runs along and soaks down, bonding it in place. Leave to set over night. You might also need to stand the hull upright so that CA glue can be run along the bow timber bonding it in place too.


Attachments:
File comment: Sticking the two hull halves together.
005.JPG
005.JPG [ 180.02 KiB | Viewed 4146 times ]

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PostPosted: Sun Feb 02, 2014 11:51 am 
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Hi all

When all the glue had set and all the clamps etc were removed I cut out the inner transom re-reinforcing piece from the component sheet. A sharp blade and some abrasive paper was used to clean up the joint inside the aft part of hull. Having carefully trimmed the reinforcing piece to form a neat fit it was glued in place with poly weld adhesive.
The pictures are self explanatory, but show clearly the keel timber sandwiched between the hull halves.


Attachments:
File comment: Transom reinforcing piece.
006.JPG
006.JPG [ 107.67 KiB | Viewed 4126 times ]
File comment: Hull halves assembled and transom reinforcing in place.
007.JPG
007.JPG [ 156.6 KiB | Viewed 4126 times ]

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PostPosted: Sun Feb 02, 2014 3:18 pm 
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Hi all

Some of you may have noticed that my vac formed hull has raised bulwarks and the 1900 twin funnel picket boat I'm modelling was flush in the bows. I decided to add these raised bulwarks so that if I decided to build a later version I already had them moulded in. At this point however I trimmed them off as they are not needed for this build. I simply scored along the mould line and snapped them off.


Attachments:
File comment: Removing the raised bulwarks on this version of the picket boat.
008.JPG
008.JPG [ 152.04 KiB | Viewed 4115 times ]

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PostPosted: Mon Feb 03, 2014 9:02 am 
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Hi all

At this point I put the partly assembled hull to one side and started to think about the finer deck detail and fittings. I thought it would be good if I could make all the fittings myself. Buying fittings “in” was not going to be an option anyway, as there was practically nothing available in the right scale, and any way most of the parts were specific to this model.

I used an assorted collection of bits of plastic, metal and some more pattern makers resin (Conform) to create “masters” for a full set of fittings for this little boat. It totalled 68 parts in the end. As each item was manufactured (some were turned on the lathe, some were carved) they were glued onto a 3mm thick base, which had already had its edges chamfered. This base was itself then glued to another slightly larger base of the same thickness.

The picture shows the finished “master” which has been sprayed with car finish red oxide primer. This gives a good matt finish and also shows up minor irregularities so that they can be rectified. The matt finish also holds the release agent (in this case petroleum jelly dissolved in white spirit) very well and makes it clear where you have applied this mix.

A thin plastic card wall was then temporarily glued around the edge of the base plate. This will retain the RTV silicon rubber while it sets.


Attachments:
File comment: The "master" used to create a silicon rubber mould of nearly all the models fittings.
IMG_0919.JPG
IMG_0919.JPG [ 145.38 KiB | Viewed 4082 times ]

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PostPosted: Tue Feb 04, 2014 8:43 am 
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Hi all

The silicon rubber mould turned out well and I was then able to cast all the fittings in one go. When the casting had been made, the fittings are still attached to what I refer to as “the casting base”. This is in fact the reservoir of liquid resin which is forced down into the mould and replaces any trapped air bubbles. When the resin sets, the 2 to 3mm thick base acts as a carrier for all the parts until I was ready to use them.

Removing the parts from the casting base was straight forward.

First I used a sharp drill of the appropriate size; to drill out any holes that were needed like the port holes. It’s so much easier to do this while these tiny parts are still held in place by the casting base.

I then used a craft knife to score the base, between clusters of components, and then carefully snapped the base into more sensible sized chunks.

Having previously tried different techniques for removing the components from the casting base, I finally perfected this very simple technique.

I found that a very fine fret (or piercing) saw blade cut through the resin easily, and with a little care the blade followed the flat surface of the casing base. A flat backed razor saw worked OK, but had a tendency to wander up or down and was more difficult to steer if the blade went off track. I also found the brass spine on the saw got in the way.

The other plus with the fret saw blade was that the cut was so fine that material loss (the kerf) was very small.

With the larger fittings, like the rudder, I also discovered that it was easier if the saw blade circled the fitting, cutting inward from all sides towards the centre, until the fitting fell away.

Each component was then rubbed gently along some fine abrasive to dress the cut surface. Sticking a piece of abrasive paper to a chunk of stout heavy board is a great idea.

.


Attachments:
File comment: All 68 fittings including the rudder servo mount, on one casting.
014(2).JPG
014(2).JPG [ 105.43 KiB | Viewed 4038 times ]
File comment: Drilling any holes before removing the fitting from the base make life easier.
026 (2).JPG
026 (2).JPG [ 107.01 KiB | Viewed 4038 times ]
File comment: A fine blade fret saw is the best method of removing the fittings from the "casting base".
016 (2).JPG
016 (2).JPG [ 106.43 KiB | Viewed 4038 times ]

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PostPosted: Tue Feb 04, 2014 10:19 am 
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beautyful !!! :thumbs_up_1:


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PostPosted: Tue Feb 04, 2014 1:22 pm 
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Thanks Sentori

I have to admit I was quite pleased with myself, having managed to produce what I consider to be a quite complicated casting. I’m sure others on this forum will have produced better stuff, but I consider this my current “high water mark” in cast fittings.

Anyway, back to the model.

I put all the cast resin fittings to one side and focussed back on the hull.

At this point I had no idea of how much the hull displaced and what weight it might carry in the form of RC gear, motor, batteries and ballast. Maths not being my strong suite, I worked this out by floating the bare hull in the sink and adding known weights. It was surprising to see that it needed 8 ounces to take it down to water line. I will leave you to work out the metric equivalent.

I should point out at this point, although I designed this from the outset as a “wet” model, there is nothing to stop me building a second as a static or even waterline model.

The eight ounces of weight kept a reasonable free board, as the hull shape indicated that the model (and one assumes the prototype vessel) would bounce across the waves, rather than plough through them.

One of the pictures attached to this post is detail from a contemporary (1900) painting by Charles Dixon and shows a twin funnel picket boat, minus gun, bouncing across a choppy sea, within Portsmouth harbour. This is an interesting colour reference source too.

When fully loaded and carrying two 14 inch torpedoes slung in dropping frames these boats were well down in the water with very little free board.


Attachments:
File comment: Floatation tests for the bare hull.
009(1).JPG
009(1).JPG [ 103 KiB | Viewed 4010 times ]
File comment: Victorian kitchen scale weights come in useful for checking ballast loads.
009(2).JPG
009(2).JPG [ 103.13 KiB | Viewed 4010 times ]
File comment: Detail of an original painting from 1900 by Charles Dixon
001.JPG
001.JPG [ 161.67 KiB | Viewed 4010 times ]

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PostPosted: Wed Feb 05, 2014 2:14 pm 
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Hi all

After installing the inner transom re-enforcing piece, I decided to also reinforce the short length of “butt” joint in the hull halves (between the transom and the wooden keel piece). This was easy to achieve with a small strip of 1mm plastic card. The solvent adhesive had stuck the hull halves together really well, but the last thing I wanted was for this joint to crack after the model was finished. As the hull is only nominally 0.75mm thick the “butt” or edge to edge joint is an obvious weak point. Another reason to reinforce this point was that the stern tube will exit here and the hull will need to be drilled to accept this.

The vac formed motor mount was cut out. This already had, more or less, the correct angle designed in. It was stuck down to the hull floor with solvent adhesive. The location point is indicated in the picture.


Attachments:
File comment: Hull seam reinforcing strip.
009.JPG
009.JPG [ 94.83 KiB | Viewed 3951 times ]
File comment: Installing the vac formed motor mount on the hull floor.
010(1).JPG
010(1).JPG [ 85.61 KiB | Viewed 3951 times ]

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