## 2013-04-07

### Finished model 2013-I

This year’s modelling competition had the theme “What if…Sweden” and Kipper had one of his brilliant ideas—he bought up every 1:72 kit of Saab Tunnan he could find and pressed them in the hands of all modellers he met against the promise that they would build it, but not in the kit configuration. Mulling things over, I had a brainwave and accepted a bagged Heller Tunnan.

Several things came together in my head: the Prusa Mendel 2 3D printer I had just bought together with some friends (including Kipper), my interest in the Saunders-Roe SR.A/1 flying-boat fighter, the rotund shape that gave the Tun its name, and the wonderful diorama of a wartime S-17BS base in the Stockholm archipelago at a previous 08-Open, so I thought:
What if the Chief of the Air Force had been to the British Gas Turbine Week in 1951, where the SR.A/1 was displayed [Jones 1993], and had decided that it would be possible to convert the all-new Saab 29 Tunnan into a flying-boat reconnaissance version that could deploy from easily-constructed archipelagic bases, the road base system not yet having been built?

I decided that it would have been designated S29H, obviously popularly known as ”Vattentunnan”. Perhaps this would be a proposal interesting enough to extend the production run of fpl 29 beyond serial 29976 in 1956 [Flyghistorisk Revy 27], so I could depict an individual palindromically serialled 29992 (coincidentally $992$10 = 11111000002). Like all other seaplanes in the Air Force, the S29H would obviously be operated by F2 at Hägernäs, extending their life as aircraft operators. F2 aircraft did not normally wear squadron-specific colours or numbers, instead using the two final digits of the serial number on the fin [Hellström & Fredin, 2000], and I presume that F2 already being special in their marking schemes, they would never bother transferring to fin letters, so 2-92 it would be. However, they probably would use the high-contrast olive green fields prescribed for A29 and S29 from 1954 onwards (not least because it would add a little splash of colour). The result would be a Tunnan as it would have looked in the late 1950s.

For the actual design of the aircraft I foresaw giving it a boat hull directly based on that of the SR.A/1, retractable wingtip floats that could double as wingtip tanks, and a couple of holes in the wings for the cameras. The cameras mounted in the actual S29C recce aircraft were pretty bulky, necessitating an entire new nose section, but this design was dragooned by Colonel Beckhammar, whereas the original plans called for a rather simpler solution, so the S29H can be taken to be based on these original plans and some clever optics. The model turned out to have a convenient panel line running all the way from air intake to exhaust and I set the razor saw to work on this. Now I could tape together the two fuselage halves and scan their outline for later use.

Then I scanned Barrie Hygate’s SR.A/1 plans [Aircraft Archive, 1988]. Kipper tipped me off to Rhino 3D, which happens to have a free beta version for OS X, and during a modelling day at the Army Museum, showed me how to loft the hull profiles into a 3D structure. Then I stretched and squashed that structure in order to match it to the previously scanned Tunnan outline. I now clearly saw how much smaller Tunnan was than the SR.A/1. I created the wingtip floats, which had fewer constraints, so did them more or less free-hand. (All this took considerably more time and fiddling around than is obvious from this short description.)

The plan had been to print the hull and floats on the 3D printer, but that was a project in itself and I hadn’t even managed to get it to communicate with my MacBook yet. On the other hand, Kipper had gotten access to a Roland 3D router, and used it to produce the desired parts for me. The material used looked like some kind of light wood, but apparently was a resin. The resolution of the router was outstanding and I was very pleased with the bits. Except for the wing-tip floats, whose size I had completely overestimated—they were just little pods. I would have to rescale them by at least a factor of 2. Still, that could wait for later.

I continued putting the model together. Heller models from the 1970s, such as this, are really not bad, with good fit, and the cockpit was reasonably well detailed. I still added a thin copper wire for the ejection handle and a bit of plastic to represent the quite prominent canopy opening mechanism.

The new hull had a big lug left from routing which I had to spend a few hours to sand away with wet paper, as I’m a bit wary about resin dust, but eventually it was in a state to be mated with the (remains of the) Heller fuselage. It fit surprisingly well—I had apparently done a careful job scanning and lofting. The only trouble spot was at the air intake, where I’d sawed through the bottom part of it, this necessitating a bit of scraping and puttying. In retrospect I should have kept the intake as was, but so it goes.

In the wings I took out a section of each lower part, in order to create the attachments for the floats. I added various tubing to represent the retraction mechanism. In the meantime, the router had broken down, so Kipper was unable to supply me with resized copies, but being the man of bright ideas that he is, he came up with an emergency solution: pilfer the wing floats from a Tamiya 1:48 Rufe, and indeed they were perfect in size.

Soon it was time for painting. I went with straight Humbrol 56 overall, and Humbrol 30 for the olive green fields (really too green a shade, I should rather have used 116, I made a thinko). Finally, the day before the exhibition, it was time to add the decals. The kit-supplied national insignia went on without problems, but my Specialtryck Swedish numerals completely disintegrated on contact with water. On this short notice I had no option but to leave the aircraft unnumbered. As I arrived the next morning, looking very glum, older hands laughed at my ignorance of the short shelf-life of Specialtryck decals. Still, there it was, and so were all the other ones! Kipper’s campaign activity had paid handsome dividends, the What if competition category had to be divided in two: one for Tunnan entries, the rest for everything else and then about as many additional entries in the hors concours exhibition. This caused some amount of excitement even abroad, and I was chuffed as nuts to see my flying boat singled out for comment.

A couple of weeks later I brought the Tunnan along to the Helsinki competitions, where it received IIIrd prize in the Jets 1/99–1/51 category, though that was really an artefact of their no-sweeps rules, it was in fact way down the list, but all the entries ahead came from only two builders…

Much later, with the help of Microscale Liquid Decal Film, I managed to get the numerals to stick together, and then scratch-built beaching gear for the aircraft, trying out the hairspray method on it. And here it is:

#### Literature

“SAAB 29 Tunnan” at Aircraft Walkaround Center, 2003.
Aircraft Archive: Post-war Jets, Volume 3, 1988, Argus Books.
Kronmärkt – Målning och märkning av svenska militärflygplan under 1900-talet, Leif Hellström & Leif Fredin, 2000, Allt om Hobby.
J29-klubben, 2010
“Saro’s flying-boat fighter”, Barry Jones, Aeroplane Monthly, 22(7), July 1993, pp 34–41.
Flygplansritningar 4: Svenska Flygvapnets Spaningsflygplan 1926–86, Björn Karlström, 1988, Allt om Hobby.
”Saab 29 Tunnan · Västerås Flygmuseum”, at 4πsr, Lennart Möllerström, 2011.
Att flyga är att leva: Flygvapnet 1926–1976, Gösta Norrbohm & Bertil Skogsberg, 1975, Bokförlaget Bra Böcker.
Flyghistorisk revy Nr 27: SAAB 29 Tunnan, 1977, Svensk Flyghistorisk Förening.
Gula Divisionen, 1954, Terrafilm.