Building a Vosper ASRL.

by Clive Halliwell

printed here by kind permission of Traplet Ltd, Publishers of Marine Modelling International

The Air / Sea Rescue Launches played a key role in WWII saving many lives on both sides of the conflict. British Power Boat and Thornycroft built the majority of the boats, though Vosper did build some; they were perhaps more well known for their MTBs and MGBs. Towards the end of the war the RAF wanted long range rescue craft for operations in the Pacific. Designs were drawn up by various builders, and keels laid by Camper & Nicholson. But because of the cessation of hostilities only one boat was actually launched (1946); Celerity was 105 ft ( 32m) long and powered by four engines had a top speed of 40 knots ( 74 kmh )and a cruising range of 4200 miles ( 6760 km ), built by Kris Cruisers. ( I think she went to the Bristol Aeroplane Co rather than the RAF ) However the end of the war meant the end of demand for small fighting craft and sadly the BPB yard at Hythe closed down but Vosper pushed on and in 1948 produced the experimental 73 ft ( 22.6 m ) MGB 538 and also the subject of this review, the 72 ft ( 21.9m) ASRL.

The Kit from AsTec

I suppose you could call it a semi-kit really ( yes that is exactly what it is... Allan). However the basic package contains the vacuum formed hull and deck, superstructure, cockpit interior, the three gun tubs, a hatch and life raft in styrene and clear plastic for the windshield and gun tub canopies. Included also are the instructions and these should be read and studied! Four more hatches, large and small vents are available separately to finish off the exterior. Motor, rudder assembly, servo mount and ESC ( Electronic speed controller ) and of course the prop shaft/s and prop/s and battery are also needed. Quite a list but conversely if you only intend to build a static display model the list would be much, much shorter.
The complete package is not expensive but the system would allow you to spread the cost a little and of course you may already have some of the hardware or fittings in your spares box.
The scale is approx 1/36th which is not a regular marine building scale though it is very close to the military scale of 1/35th. I mention this because modellers whishing to add extra detail may need to purchase additional fittings or crew. But not to worry, many fittings from the standard scales of 1/32nd and 1/48th will suffice. A small fairlead or bollard at 1/32nd will become slightly larger on the model and a large locker at 1/48th smaller. Even with the crew, not everyone is the same height, it's really a matter of common sense. The easiest solution would be converting a set of 1/35 scale soldiers in 'tin hats' to sailors at action stations i.e. in 'tin hats' ! You could perhaps shorten the legs of 1/32nd figures.

The 'Big' bits

The hull and deck need the excess styrene to be trimmed away and the instructions help the newcomer here with hints and tips. The usual method is to score around the particular item and then bend along the scored line to break away the excess. Each part should be cut slightly oversize and then pared back to the final line with a sanding block or a fine file. Take your time. If unsure practice on a scrap piece. Also do not throw away the various off-cuts, they will come in handy later.
There is always a great temptation at this stage to push on and fit the deck and superstructure to get a feel for the end result. However some thought should be given to fitting the hardware, motor(s), propshaft(s) and rudder (s) etc. first, as access will be restricted once the deck is fixed in place. The deck, with its built-in rubbing strake, actually fits over the hull and should be fitted much later. Of course if you are building a static model push on.
At some point you will need a stand of some sort. Whether it is a basic work stand or finely made display stand is up to the individual. I used a basic work one well padded with foam draught-excluder strip.

Cutting out

I followed the Build Instructions and stuck masking tape around the top edge of the hull. First I ran my thumb nail along the groove that represents the cut line and then marked it with a fine marker pen. At the bow and at either corner of the transom I made vertical cuts down to the trim line so that it was easy to bend and break away in sections. The deck was next. Be careful here; I found the trim line a little indistinct in places. Just check that your marked out line is parallel to the deck and not the outer edge of the moulding. Always ere on the too large size, it is easier to sand back than stretch! It did not take long, or cause any problems, and I soon had a nice neat fit of the deck over the hull. The deck edge forms an integral rubbing strake.
The superstructure was next. Again I made small cuts at right angles to the cut line in order to break away the excess in sections, especially around the rounded base of the wheelhouse. With that done I cut out the opening for the bridge. This time it was under cut so that I could trim back to the moulded edge. The well itself was cut leaving a small lip all around the top edge. ( I think just visible in a photo ) With the well oversize, and the bridge opening under size, I should, with careful trimming, get a neat fit!
At this stage you could fit the deck on top of the hull and then put the superstructure in place to get a feel for the end result.

Adhesives

You need to be aware that plastic can 'melt' under the influence of some adhesives. There are dedicated glues for styrene. Always check the instructions and if in any doubt try some on scrap off-cuts. 'Plastic Weld' is another product dedicated to plastic sheet. In liquid form it melts the two parts of a joint before rapidly evaporating to leave the 'weld' Do NOT overuse as you could melt the whole area. Practise on scrap first and be aware of 'elf & safety. You can also make up your own filler by adding scraps of styrene in to a spare jar with a small amount of Plastic Weld in it. Add a little at a time until it becomes a usable paste. My fabricated motor mount was strengthened using this method. ( see below)

A Change of plan?

It was at this point that I began to think about a different approach :- a complete lift-off deck. The instructions from AsTec suggest cutting away an access opening in the deck below the superstructure. The complete lift-off deck would obviously give greater access for maintenance and also I could fix the mast, rigging and aerials etc more or less permanently. The down side would be watertight integrity and an accessible On/Off switch. Despite this I decided go for the complete lift-off deck and solve the problems along the way. I leave the decision to the individual modeller. None the less I cut away the section suggested and if I secured the superstructure with screws or bolts I could always revert to the original plan!

Hardware

The rudder was a commercial assembly that contains a brass rudder ( 34 x 24mm approx) and stock, a rudder tube with nut, washer and 'O' ring and a double tiller arm. They are available in various sizes from most model shops or by mail order and not expensive. The only problem was that the rudder tube was not threaded along its whole length. I made up a spacer from styrene tube and this allowed the nut and washer to clamp the whole assembly to the hull. (it is just visible in one of the photos) Subsequently I ran Plastic Weld between the bottom of the spacer and the hull and down between the inside of the spacer and the thread of the rudder tube. Nice and solid and waterproof. I also needed to file away a section of the moulded keel to get the rudder tube to fit snugly.


The build instructions suggest several options. From single 440 motor and single rudder ( or low drain 540 motor ) to a twin 440 and twin rudder installation. I had a spare 540 motor on its standard mount and tried it in situ. The mount seemed to fix the motor quite high up in the hull therefore increasing the angle of the prop tube or requiring a long prop tube and mounting the motor well forward. I considered fabricating a smaller mount from scarp styrene that would sit the 540 down in the bilges and in the end went along that route. With the motor I had a spare coupling and a 25mm brass prop; a quick visit to the model shop and I had a 5 inch prop tube with 4mm shaft. I drilled two holes, slightly smaller than the diameter of the prop tube, along the centre line and then cut out the section between them to form an elongated slot. With the motor fixed to the front face of its new mount handy, the slot was opened up carefully, width wise, until the prop tube was a push fit then slowly length ways. With the prop on its shaft and the shaft coupled to the motor the whole assembly was lined up until I had a nice, low drive line. Plenty of Blu-Tac was used in this exercise, continually checking that all was in line and the prop would spin and not foul the hull bottom or rudder! Once happy the two support brackets for the motor mount were 'welded' in place and the prop tube sealed through the hull with filler. (Isopon P38) I also fabricated an A-bracket to support the prop tube, but this is optional.

The Battery

I intended to use an ESC ( electronic speed controller ) with a BEC ( battery eliminator circuit ) therefore only one main battery or battery pack would be necessary; easing the problems of fitting, wiring and charging. ( My personal preference.) Back to the title of this section. Whole tomes have been written on this subject, and continue to be, as new hi-tech batteries, and their 'intelligent' chargers, come on the market. I guess the modeller intending to build this particular kit will not be investing in the latter set, at this stage, which may well cost more than the kit, the hardware and the R/C system put together! Basically the choice lies between the SLA ( sealed lead acid )or a NiCad pack or similar; each has a relatively simple and inexpensive plug-type transformer charger. There is even an argument for the standard dry cells. If this is your first attempt at marine modelling and you wish to keep the initial outlay to a bare minimum then you could install a battery holder and four dry cells ( 6 volts ) and upgrade later. I went for a 6volt 4 amp/hr SLA, probably about the largest battery you could install without compromising stability. A smaller / lighter battery or pack may need some ballast to get down to the waterline, but ballast does not have an amp/hr rating! When the battery's final position had been ascertained a styrene supporting tray was built around and under it.

Armament

Conceived along the lines of a lifeboat's role to save lives it was not initially intended to arm these rescue craft. However with their similarity to various coastal forces offensive boats, their hulls were the same, their silhouettes similar, they were given an anti-aircraft capability in the form of machineguns in tubs with the aircraft type Perspex covers.
The tubs were made up generally as per Build Instructions (see photo) and a section of the bottom rim of the two high tubs cut away so that they fitted close up against the superstructure sides. The machineguns were made up from scrap plastic tube.

Liferaft

The two halves of the liferaft were trimmed away from the backing sheet and glued together and sanded and filled as necessary. Here I decided to cover the styrene in masking tape strips to represent the outer canvas covering of a balsa raft. The raft outer rim was then painted, a dirty brown/grey. Some scrap balsa provided the wooden slats for the floor (mix up the grain ) with a couple of matchsticks for the athwart supports. An hour or so with needle and thread completed the rope work. ( knots and joints out of view were secured with a drop of superglue via a cocktail stick ) The paddles were made up from a cocktail stick and a lollipop stick

If following the Build Instructions to the letter you would probably have to make this area a removable section to gain access to the rudder servo and/or tiller arm and linkage. Typically a hole is cut in the deck and a coaming fitted around the inside. An inverted 'tray' made to fit tightly over it with the raft fixed to that.

Insert drawing ' LiferaftAccess.bmp '

Windows and glazing

I followed the Build Instructions for the wheelhouse windows, namely mark out the aperture, drill a series of small holes just inside the line, cut out the central section and then file or sand to full size. They are then glazed with a single length of clear plastic on the inside ( easiest after painting the outside), the six windows around the aft section of the superstructure were merely painted black after spraying. ( Note that superglues tend to 'fog' clear plastic.)

Waterproofing

Because I had decided to go for the whole lift-off deck option my thoughts turned to making the join waterproof. I intended that the deck would be screwed down at sea but water has a habit of seeping in, especially at speed. To this end I fabricated an inwhale around the inside of the hull at deck level, across the transom and built up a triangular block in the bows. I laminated lengths of balsa, it is easier to follow the curve of the hull, with the for'd sections having their grain vertical. Plastic is soft and after each laminate I made sure the deck still fitted over the hull. The bow section was made quite thick and a final length of 12 x 6mm balsa glued across the front face of the transom inwhale, these two areas would take the securing screws after the whole top edge of the inwhales had been well greased ( Vaseline )

The mast

The mast is from plastic tube; it goes down through the coachroof and is supported by sliding a short length of the next size tube over the lower end and 'welding' in place. Also were the lower section of the mast butts up against the superstructure plastic weld is brushed into the join. The RX aerial will go up as far the yardarm, which, like the top mast, is from a cocktail stick. The rigging is black sheering elastic with brown sheering elastic for the signal flag halyards.

Painting

This is not to help with waterproofing, as it would be with a wooden model, but to make it look right. The photos should help but basically I used red oxide for the lower hull, black above that, grey for the superstructure and deck equipment and yellow ochre for the deck. You may spot a bit of weathering, it is merely cold tea brushed on to certain areas that would be covered in spray at high speed.

On the water

The 540 motor drove the boat at what was probably well over scale speed, producing a nice bow wave and wake, but the heavy SLA battery kept the model in the water. By that I mean it did not skim across the surface like some fast electric racer, but sat down and, I think, looks much the better for it. Duration will of course depend on several things, battery size and state of charge, how much time you spend at full throttle etc. Incidentally for its first serious outing on the water, forty-five minuets or so, the deck was not screwed down. The fit is so neat that I relied solely on the Vaseline to keep the deck in place; there was not one drop of water inside the hull.

ARSL Appendix

I thought I could point out here to the newcomer that it is always possible to modify a basic kit. I have included three ideas for vessels that could be built from the basic box of parts. They are of course free-lance designs of mine but are based on genuine designs that saw service for the situation was often very confusing as the MASB concept was flawed and many boats commissioned as 'sub-chasers' were converted to ASRLs and MGBs.
The first suggestion being the RAF Crash Tender, unarmed and fitted with water cannons. ( working cannons are available commercially if you fancy this design)
The second and third are really Royal Navy WWII vessels. The MGB has the after gun tub replaced by Rolls Royce, single shot 2pdr or the ubiquitous 20mm Oerlikon. The MASB has depth charges on racks either side in lieu of the after gun tub. (The gun tubs would not have the Perspex covers ) The scale would generally have to stay the same. As the superstructure, bridge area etc. would look at odds with different size crew members wondering around!
I have planned my ASRL with the possibility of rebuilding it later ( the after gun tub is not permanently glued in place ) The MASB version appeals, so removing the aft tub and a re-paint and adding a few DC's and maybe smoke generators and I would have a new model. As an ex-Submariner I am not sure why the MASB appeals but I guess they were not supposed to depth charge one of their own subs, only the enemy; but then again maybe I will build a gunboat! Anyway just an idea

Freelancedesigns.bmp

Conclusion

The fact that it is only a semi-kit, no minor fittings or hardware, keeps the initial outlay quite low and gives the builder many options from the simple to the much more detailed. The instructions are not comprehensive, but they do not need to be; the one piece hull, complete deck and one piece moulded superstructure merely need cutting out and trimming to give reasonably finished model. Of course one can go on and on adding fittings and details! It is relatively easy and I am sure it will suit the newcomer / novice builder.

Notes:-

If still unsure about working with plastic, this magazine runs occasional articles on this subject and back issues are available. The most recent I think was Tiffy's Workshop, a quite comprehensive guide, in MMI December 2008. AsTec are at www.astecmodels.co.uk tel:- 01275 543471 Model shop ( mail order ) www.redbank-models.co.uk tel:- 01253 751537 (Blackpool) Numbers, roundels, flags etc. BECC Model Accessories Ltd, stocked at many outlets or tel:- 020 8777 9377 ( e-mail chris@becc.co.uk ) Try www.bmpt.org.uk for a short Pathe News film of an ASRL at work. ( British Military Powerboat Trust )

Here is are a few other pictures to accompany the article.