The Ship Model Forum

This is - was - HMS Coventry D118, a Type 42 air defence destroyer. Launched in 1974 and commissioned in 1978, she was sunk by Argentine A-4 Skyhawks in the Falklands War of 1982, with 19 of her crew lost. My father was part of the crew (and still with us thankfully).



Last year I found a radio control model of a Type 42 (HMS Cardiff D108) on Gumtree for a reasonable price. It had been built from a Sirmar fibreglass hull and various resin fittings plus scratch built wooden superstructure based on, I think, Jecobin plans. The fuzzy pictures on Gumtree made it look better than it was in the 'flesh', but it was a good price, cheaper than buying just the bare hull. So I decided it would be a good basis for a refurbishment to turn into HMS Coventry.

The Type 42 was built to 3 standards, or batches - Coventry was a batch 1, of which 8 were built (including, ironically, 2 for the Argentine navy). She was the 6th ship to be laid down so benefited from some lessons learned as earlier ships were constructed and had some variations in fit. The 8 ships of batch 1 all had some obvious differences. The first of the class, Sheffield (also sadly lost in the Falklands War), along with the two Argentine examples, had 'Mickey Mouse' ears on her funnel; the Argentine pair had an upper deck extension amidships for mounting Exocet missile launchers. Sheffield had no upper deck sponsons for STWS torpedo launchers, though all subsequent RN examples did. Sheffield and Birmingham initially had a green deck and a boxier main mast than the other ships. The type 965 'double bedstead' radar was fitted to the early batch 1s, with - I think - Exeter being the first to get the less bulky type 1022 instead. For the purposes of this build I can ignore all the later modifications made to the type 42s except in terms of recognising what not to do!



So that's what I'm starting with. It's not a bad effort at all - certainly better than I could manage from chopping up bits of wood - but to turn it into HMS Coventry will need some work. Anyway the initial list of jobs was:

1. Remove the supports holding up the STWS deck and hangar deck (easy, hack hack)
2. Replace the funnel with an accurate one (not so easy but I soon acquired a Sirmar resin one)
3. Replace the type 1022 radar with a 965 (photo etched one acquired from Scalewarship)

But you know how it goes. The more you look, the more you find things that are wrong. So the main most is the type that Sheffield had - that needs to go then. The superstructure on which that mast sits is wrongly shaped at its aft end. The kit on top of the hangar is mostly wrong. The aft 909 radar office and the forward end of the hangar are wrong. The bridge screen shouldn't have a railing right across the front. And on and on and on...

Now skip ahead to the first coronavirus lockdown back in March. A partial set of scale plans was donated to me (thanks radiojoe!), and a quick shufti at those found that the boat suffered from a lot of over-simplified construction. I removed the type 1022 radar from its pedestal, but then found the pedestal was a solid block of wood, which would preclude having the type 965 from rotating, which is surely a must-have.

Now I'm not great at whittling wood, but I'm alright with computers. So, as you do, I've been teaching myself Fusion 360 3D modelling, bought a 3D printer (Elegoo Mars Pro, which uses UV cured resin), and got cracking with designing a replacement radar pedestal that would be hollow and give me some room for the gubbins necessary to have a rotating radar head. So here's the existing radar pedestal, and the first test print of my resulting 3D design:





The first lessons learned with this were that the printer was capable of some pretty amazing fidelity, but you have to balance that with the resulting fragility. Round the aft side of the pedestal, for instance, the diesel generator exhausts were so thin they crumbled away when I was cleaning the part up. And, of course, the more reference material I collected from various Facebook groups, Flickr, etc., the more detail I could incorporate on the design.



Broken exhausts on the first (left) print. I also found that, under a coat of primer, I was getting some horrendous horizontal steps in sloped surfaces. Some experimentation found that these were the result of how the slicing software deals with angled surfaces, and could be reduced by rotating the object on the printer's build plate (35 degrees worked for the print on the right above). The perceived wisdom on many 3D printing groups/forums is that you should angle things vertically too, but I like to start from a handy flat surface on the build plate where possible, and let the items 'grow' from that point.

The forward superstructure is easily removable for access to the batteries and motors etc. inside the hull, which makes working on the rebuild easier too. Here I've got as far as removing the inaccurate funnel and cleaning up some of the decks. I now had a new resin funnel, which fits nicely. But we'll revisit that later. Another error found at this point was the fore mast, which is vertical when it should slope back slightly, and has a damping blanket wrapped around it which HMS Coventry did not have.



So, I designed some masts!



Each is broken up into sections for printing, and mostly hollow to save weight, use less resin, and you also have to avoid trapping any uncured liquid resin inside anything. The fore mast is made up of the base, main shaft, and everything from the disc at the top upwards. Plus the radar head. I initially had the disc upwards as part of the main shaft but it failed to print - that big flat disc just couldn't be held by the thin support beneath it as the printer peeled that layer off the exposure plate.

The main mast I broke up into the base (up to the second change in angle), the main section (all the way up to the top platform support), and the top platform with separate radar head again. I had to go back and separate out the railings around the lower platform as they made it too awkward to paint things.

Clearing the decks. I roughly penned in all the missing detail hence the black marker in places. To correct the rear part I cut away some of the wood and blanked it off with plastic card:



...and tried the new main mast for fit. Nearly perfect, but the ladder on the mast clashes with the roof, which makes me think the original builder has got the height of the superstucture slightly wrong. Also, the gap between the main superstructure and the hangar block is far too narrow. Hmmm...!



As to the hangar block, that had errors too. The 909 office was butted right up against the hangar wall, when in reality there is a gap. The hangar itself is also not a straight line at this edge - it's kinda L-shaped. So I started rectifying this by cutting out part of the rear wall:



...and drawing up a replacement 909 office:



The pipes are - I think - part of the pre-wetting system that sprays water all over the ship in advance of a nuclear attack, so that fallout can be more easily washed off afterwards.The big hole in the top saves resin and also lets it drain out during printing; I chose to put the bottom of the office on the build plate, because the pipe work makes starting from the roof or sides impossible.

While I was at it, I thought the resin 909 domes (Sirmar I guess) looked slightly undersized, so I designed replacements. These printed from the base upwards, and I was conscious that would end up with a small amount of resin trapped inside when printing was finished, but I thought it would be a small amount and could be poured out when the part was removed from the build plate. I was wrong, it was a lot!



Office printed too - the pipe work is a bit saggy in place due to insufficient supports but that kinda matches photos of many real ships. A word on resin too; up to this point I was using clear resin, as it has the advantage that you can see if any solid bits have broken off during printing and are lying at the bottom of the vat when printing is finished. You can destroy your printer screen if the build plate comes down on top of anything solid and punctures the exposure plate, which is a very very thin and flexible piece of clear plastic film. However, clear resin is very brittle, particularly if you do a post-cure for too long. It also goes yellow very quickly if you over-cure it - which I have for these parts!

For a bit of light relief I moved on to replacing some fittings, namely the forward superstructure life raft shelves:



This is the 5 raft version that all the batch 1s were initially fitted with. What I didn't realise until one of the ex-crew pointed it out was that Coventry underwent a refit in 1981 where the forward two life raft stowages were cut off (the rafts had their occupancy ratings upped so fewer were needed onboard - in fact during 1980 she simply sailed with the forward 2 rafts removed, but the stowages still there). I'll have to revisit this bit later!



The hangar area also has shelves for life rafts and other bits. The cage at the far right of each shelf is for fuel can stowage for the engines of the ships's boats. They're angled so that all the cans can be jettisoned into the sea by undoing a retaining strap - for instance in case of a nearby fire (and presumably when air raid warning red is piped?). It's not until you start really looking at photos that you find the little bits of unexpected differences - some of the early ships including Coventry had a smaller stowage area on one side, my first iteration of this missed that detail.

The model's existing bridge. You guessed it - it's not quite right. The bridge's windowed area should go up in line with the 'screen' area below, and not have a hand rail in front. The windows are just black painted bits of photo etched metal too.



So, the most ambitious bit of design so far. Complete bridge and port bridge wing (no need to do starboard, it's a mirror image so I just print it mirrored). Hardest part here was finding reference photos - thankfully a couple of Facebook groups came up trumps.



Despite there being little chance of seeing much through those windows I did some basic interior shapes and some roof detail. Just because.



I've left the windows open and will figure out how to glaze them later. A couple of test prints gave me the right angle to park the windscreen wipers at so that they would print without needing to be separate bits.
However...



Some oddities when printed.

As with previous parts, I'd designed this to print from the ground up, i.e. the roof was the last bit to get done. The roof top, however, has lost some detail, namely the railing running from port to starboard behind the nav light stand. There's an odd 'step' just below roof level that isn't in the 3D model either. Also if you look closely at the bottom edges, there are some holes where no resin has been cured at all.

This is a problem with the Mars 2 Pro; it uses a grid of LED lights as a light source to cure the resin, and the plastic grid guide results in a cold spots where insufficient light gets through. Elegoo will provide a replacement grid and LED board if you contact their support, but it involves dismantling the entire printer to fit it and doesn't entirely cure the problem; I've since fitted my 'fixed' grid and while I no longer get holes in cold spots, you can still sometimes see indications of the grid pattern on large flat surfaces. A gentle sanding sorts it most of the time but there are types of printing - such as curved transparent lithos - you simply cannot therefore print nicely on this machine.

...more concerning though, is the recurrence of the weird piling up of resin in the roof interior:



It looks like uncured resin has collected and the roof has a sagged and melted look as a result. It took me some time after this to figure out what is going on. As the bridge was printed from the bottom up, it had nice solid walls and then the printer laid down a very very thin (0.02mm) layer of resin for the first lattice of roof reinforcement. That gets cured, then the print head moves up to peel the layer off the exposure sheet. It's not fully cured, so it's pretty flexible, and flaps like a sheet of paper in a breeze, being unsupported in the middle. When the print head moves back down to start the next layer, that flexible layer now flaps in the opposite direction, then a new layer is cured... with the previous layer not fully back in place. So over time this results in liquid resin trapped between ever wavier cured layers. Not good. The lesson is not to allow horizontal flat surfaces suddenly come into play as a design moves through the printing process.



Bridge wings - these worked better, though I'm not too happy with the contours underneath them and how they'll fit against the existing superstructure. Amazed that the little pipes on the outside faces printed OK, though they're incredibly fragile!

impressive progress in a short period!

JIM B

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David - yeah I came to that decision! Haven't been keeping the thread up to date, will try harder...

Boat davits. Earlier in their career, type 42s carried a motor launch and a whaler either side of the funnel. Falklands experience showed that better defensive armament would be a wiser use of the space so these were done away with on later ships to make room (and weight capacity) for better cannon (and later CIWS). These were a pain to design as I couldn't find any good drawings or photos but I think they're roughly right.





Printed nicely first time so quick test fit - nearly right, cutting away the raised deck edge found them to be nearly dead on for spacing. I'll use a bit of brass or plastic rod to do the connecting shaft but for the time being these are being put aside while I work on other bits and pieces, such as this lot:



Hangar roof gubbins. From the top, clockwise... some sort of wooden mat (?), HF aerial (later ships had a mesh cone, early ones were solid with drain holes like this), gangway, RAS pipes (?) and some big blocky thing of which I know nothing. And the more I looked at the hangar and the tiny gap between it and the main superstructure, the more I got worried. Something was clearly amiss - but where?

So I measured up the hangar compared to the scale plans. And it matched. And then it didn't match. And I got confused. And then I realised that the scale plans (from Jecobin) aren't even consistent with themselves.The length of the hangar is different in the side profile compared to the overhead one. Aargh!

Now, I already had the task of blanking off the bit of the hangar that I'd cut away to fit the new 909 office into, and the whole thing was lacking in detail, so I bit the bullet and designed the entire hangar superstructure block in Fusion. This was going to result in something significantly bigger than the build volume that the printer can handle, so it had to be split up into bits. And I didn't want a repeat of the roof problems I had with the bridge, either, so no building from the floor upwards this time.

Now, minus the life raft shelves etc., the rear portion of the hangar superstructure could fit within the printer's build area if I cut it just aft of the 909 office, and then used that cut surface to build up from. I wasn't sure how rigid thin resin would be, so I went for fairly thick walls but that still left a lot of internal volume to do something about. God knows what possessed me (gin probably) but I decided as it's going to have to be an empty shell to save resin and weight, it'd be a shame not to have *some* detail in there. Couldn't find any photos of early 42 hangars so it's all a bit speculative based upon the few photos I could find of later ships.





The printed result after a quick blast of white primer on the interior...



Success. Didn't clean off dust etc properly before priming but nobody will see. No soggy roof! It's a heavy chunk. If I were to go back and redo this I'd make the walls much much thinner.



Evidence of the resin-piling-up problem at the rear face. As this is all hidden it's no problem but I did have to go digging into this to release a certain amount of liquid resin trapped in the layers. Again, experience has told me how to better deal with this - support these surfaces like mad, or seperate these faces out and print them on their own.

Aft hangar block external view, with life raft shelves glued on. One genius aspect of this UV curing resin is you can use it as glue - just apply a thin layer to the surface and point a UV flashlight at it. It hardens incredibly quickly and forms a really solid bond. Far, far better than superglue. There are various details missing from the hangar at this point - approach lights, landing aids, a big cabinet on the aft bulkhead - all to come later.

If you look very closely you can see the fine stepped lines on the angled surface of the life raft shelves. As these will be obscured by the liferafts once fitted I'm not bothered about sanding them smooth. The side of the hangar has more widely spaced lines, which I have made some effort to sand off.



This is the area of superstructure forward of the actual hangar. Annoyingly, this was too big to print it one go too so I split it in two (you can see the join line along the top near the ladder). The obvious choice here for build plate surface was the roof itself, which avoids any shelves collecting resin elsewhere. So I cut off the little bit sticking up and printed that separately too. Also you'll see an open ventilator hatch, I seperated that out before printing as it otherwise gets cut in two by the roof line.



Another view, showing some reinforcement walls to keep things stiff. In the end I don't think these were actually necessary and were I to print this block again I'd try without them.



Printed item, primed and glued to the aft section. I've clipped off the reinforcement bits to save weight.



Some assorted gubbins for the upper hangar deck. Lockers, cabinets etc. plus the blast shield and control kit for the Corvus chaff launchers.



Took two attempts to print the Corvus shields, as they needed more of a floor to work properly, but they came out OK second time. Rough placement of various bits to see how far I'd got - this was actually taken before the 'glued together' shot earlier in this post hence the missing life raft shelves.

Right, light relief time. Funny I always think doing a small bit will be less work than the big chunks. They never are.



Mk.32 Shipborne Torpedo Weapon System (STWS) or the triple torpedo tube as the Septics call it. Great bit of bolt-on kit dating from 1960 with a rotating mount and 3 torpedoes ejected by a compressed air system (the hemispherical end) after the end cap (left) hinges up out of the way. The derrick to the right is used for loading torpedoes into the tubes.On later ships these were removed to make space and weight capacity for other equipment such as more guns - the ship retained torpedo capability via the Ship's Flight Lynx.



STWS fresh from washing after printing. If you look closely you'll see a flat disc under each one - this is where the mounting failed to print correctly.



After post cure and removal of supports. I ended up making separate parts for the mountings as they didn't print correctly for some reason. Look at that detail - I didn't think the wiring on the junction box would come out for instance!

Now, going back to the central superstructure. Again on comparison with scale plans, something was seriously out. It looks like the entire section is too long, with the errors spread over several places. The lack of detail and the cross passageway made the decision to rebuild the section under the funnel easy enough. However, choosing the orientation to print it was trickier - flat deck is the obvious build plate area, but makes the part too wide to print in one go. Also too long, of course. So this part is actually split into 4 bits for printing.



Resulting bits, glued together, and placed on top of the existing model structure to demonstrate how far out the woodwork is. The big empty space gives me more room to possibly put a smoke generator in the funnel... hmmm.... Any recommendations for an inexpensive non-polluting smokey thing?



So, the funnel. As I mentioned earlier I had a quite nice funnel replacement already. Big chunky bit of resin - 90 grams of it. Dimensionally pretty accurate but a little lacking in detail perhaps. And it had two big rectangular depressions on top that aren't there on photos of early type 42s. So, sod it, designed that too. As I've been doing with other bits, I'm going with ladders and railings embedded on the surface rather than being separate items. This is because it'll save me time and fiddling, and hopefully be more robust when it comes to handling the model.



Completed funnel test fit - spot on. The holes in the side of the funnel are for later use to put in some aerial spreader poles, resin wouldn't be strong enough for those so I'll use brass rod. I have used resin for the bracing to the side of the main mast as you can see on the far right - that's under no load so while it's still delicate I might get away with it, or I might replace with brass too. The completed funnel is 64 grams, so a nice little weight saving on the Sirmar item too. This is a wide angle shot so the forward side of the funnel is distorted looking - it does correctly slope back a bit in reality.

Back to fiddly bits...

8 barrelled Corvus chaff rocket launcher. Another sod to design as I couldn't find any decent drawings and online info contradicts actual photos. Best I could manage anyway. Illumination rocket launcher on top. Chaff rockets are used to throw a bundle of basically metal foil into the air to decoy away missiles (such as the infamous Exocet). A type 42 had 16 ready to go, supposedly enough to decoy away 4 attacks before reloads were necessary... but they didn't carry many reloads.



I designed this to include the deck wiring conduits, but they didn't print well; I also designed it so that the illumination rocket launcher was printed seperately so I could support it easier. A mistake in retrospect as they were a massive pain to clean up without breaking them!

Next, the pelorus stand on the hangar roof - part of the emergency conning position. There's a lot of gubbins on the hangar roof, it's going to take a while to figure it all out.



Then I started chopping wood. At this point I was still planning on just giving the superstructure a new bridge and making do with the rest of it...

My model's Sea Dart launcher, hiding under a thick layer of paint, looked to be a bit basic so I'm replacing that too. Another tricky one to design as there are so many different shapes! This is the 42's main armament - the GWS 30 Sea Dart launcher. Pictured in the loading position with the arms slewed to the vertical position and a single drill missile loaded. I've designed it in bits so it'll be able to be posed in different positions. Something entirely missing from the existing resin launcher was the loading arm on the port side. A delicate bit in 1/96 but it printed OK.

For a 1960s design this was a fearsome bit of kit, with a rocket booster getting the missile airborne and up to speed for the kerosene-fuelled ramjet to take over and accelerate it up to mach 2.5+ and hit targets up to 30 miles away and at altitudes of up to 82,000 ft. However, it was expected to be used in the open ocean, not close in to land, and in the Falklands conflict the associated radar kit was badly hampered by ground returns, resulting in several failures to lock - thus contributing to the loss of HMS Coventry. On the flip side, as the Argentines also had a pair of type 42s, they knew that flying at high altitude anywhere near a type 42 was pretty much suicidal, so they chose to stay at extreme low level, costing them a lot of fuel and restricting their time over the islands.



Next up, the Vickers Mk.8 4.5" gun. More tricky shapes. My model already has a pretty decent resin gun (Sirmar I think) but in for a penny and all that. This will be printed in 4 bits - barrel, main body, the short ladder section attached to the underside and the base itself, so that the gun turret will be able to rotate.

The 4.5 printed out pretty well, though I got a repeat of the issue of resin piling up underneath the flat base. As it's out of sight, I'm not going to revisit to fix this. Or at least that's what I thought at the time.



Now, the Oerlikon 20mm cannon. Two of these, mounted either side just aft of the bridge. Of WW2 vintage and absolutely sod all use if you're trying to hit a fast moving jet. These are aimed entirely by eye, moved manually by the gunner and reloaded manually too by swapping out the big magazine drum on top. Falklands experience led to more modern cannons being mounted, and type 42s eventually ended up with the far more lethal Phalanx CIWS. I've thickened up a lot of details on this in the hope it will print OK while still looking vaguely accurate. We'll see!



...this little printer continues to impress, I didn't hold out much hope for some of the finer detail on this (e.g. the handles on the magazine and the gunsight), but it's all there.

This took a few days! Westland Lynx HAS.2. Coventry's main anti-submarine and anti-ship weapon, able to carry torpedoes, magnetic anomaly detector, nuclear depth charges, Sea Sku air to surface missiles (first combat use was by Coventry's Lynx in 1982) and - in a fit of improvisation involving an office chair base - a door gun! Obviously not all at once. This could be a proper project in its own right, but I've gone for minimal detail as it'll be pretty small at 1/96 scale and I could be here for weeks otherwise.



I split this into a number of parts to print - forward cabin, rear cabin, tailboom being the major portions. The rotor head and rotor blades were seperate too (idiotic idea to try and have them both rotating) and took several iterations before I was happy with their strength.

LAS - Lookout Aiming Sight - a pair of these were mounted on little sponsons midships. Equipped with a variety of optical sights, the guns and Sea Dart could be visually aimed using these sights should the need arise, and as the name suggest were also used for basic lookout. Exposed to the weather, operators had the option of wearing a heated suit, which - along with the intercom headset - gave the wearer regular electric shocks to keep them awake. This was not by design!



Then I decided that I might as well do the upper superstructure. Forward bulkhead full of holes to save weight & resin. Holes in the upper deck for similar reasons, and to give access for a motor to rotate the radar.



Another view of the upper superstructure, with the various other bits connecting to it displayed too.The white domes cover satellite communication dishes; sadly for HMS Sheffield, it was comms on this system that interfered with one of her ECM systems that could have picked up the incoming Exocet raid that hit the ship and left her as a burning wreck.

Blimey, it all adds up... controller for scale.



Around this time I compared my newly printed bridge with photos of the real thing, rather than the drawings I'd been working from. And was gutted to discover how far out the drawings were compared to reality. So, with the aid of many many photos I started re-doing the bridge, and with more experience of printing, also handled the roof in a different way to avoid the problem of resin piling up. Basically I left the roof off and printed it seperately. Now, that means I do have to glue it on... or... I could leave it as a removable item and show off the interior. Guess I better model the interior then. Do you know how big a single button on a control panel is when you print it at 1/96 scale? No, I hadn't thought about that either. Still, kept me off the streets for a few days.



New bridge and new bridge roof in place... some of the wipers broke off but they'll get fixed later.



Interior. All of the consoles printed as separate bits to ease painting, then glued into the bridge walls.



Rear of the bridge. Bit of a mixture of stuff you'd have found in HMS Coventry (and any 42) and more modern kit, as I have no photos of this area of Coventry's bridge.

So, cunning plans. Having designed the bridge roof to be removable, I temporarily forgot that the rear end of the roof was partially covered by the 909 radome, which would prevent roof removal. Unless I only stick the radome down to the removable roof, and not to the main superstructure, in which case I could use the radome as a handle to pull the roof off. But if I do that... I need to have a radar inside the radome, right? So here's the type 909 target illumination radar (big dish) and its associated missile reference aerial (dome on a stick at the top) and jamming assessment aerial (the mini dish top left). The ship had two of these 909s in the big domes, so the ship didn't have any blind spots.



Soooo... attentive followers of this build may have spotted a bit of a theme of me deciding to do more and more of the ship from scratch. So I started on the main superstructure itself. The light blue rectangle at the bottom left is the size of the 3D printer's build area; as you can see this is going to mean chopping up the superstructure into many bits if I'm going to do it all. We'll see...

So yeah, I designed the main superstructure in 3D and got on with printing it - in 9 big chunks! To avoid that resin-piling-up issue all parts are printed with the top surface on the build plate, so any additional detail bits to go on the decks will be added later.



Altogether it broke down into 9 major chunks, with 2 additional parts to make up the torpedo deck extensions, seen here all stuck together.



LAS sponsons, more bits to tack on to the superstructure. These sit underneath the SCOT domes and stick out to give the LAS operators a clearer view fore and aft.



Torpedo deck extensions. Ironically the photos of Coventry rolling over before sinking provided the basis for the underside detail I put in here. The circular bit is where the STWS mount is attached to the deck above.

Coventry, as with all 42s, was powered by 4 gas turbines - two Rolls Royce Olympus and two Rolls Royce Tyne. These could be operated in various combinations to drive the two prop shafts. They were hungry for air, and on the batch 1 ships this was the design for the intake block.



The intake grids came out pretty well - they'll look good under a coat of paint.



Then I revisited the forward life raft shelves to cut them down to the 3-raft fit Coventry ended up with. There were 5 originally but they were found to be capable of holding more men than expected, so to reduce top weight, first 2 rafts each side were removed, then the empty mounts were cut off in a refit.



Life raft shelves and LAS sponsons in place...



And after much sanding and gluing and a visit to the spray booth, she's really beginning to look the business. Various parts just positioned roughly for the photo - much more to do!