Hawker Hurricane Project Diary Part 1

The Vampire is my only previous venture into the realm of PSS (Power Scale Soaring) and, since selling it on in 2010, I must admit that I hadn't given much more thought to the genre. However in 2016 I accompanied my wife to the AGM of the Quilters' Guild of the British Isles in Llandudno. Well, I didn't attend the actual AGM of course but instead went up onto the nearby Great Orme where, by happy coincidence, the PSSA were holding one of their fly-ins.

No longer having the Vampire, I had taken along the venerable SAS Thing to fly, but the main motivation for the visit was to see what the PSS boys were flying nowadays. There was a wide variety of models on show, ranging from gutted ARTF foamie EDFs through to scratch built models from a variety of materials including balsa, foam and Correx (the corrugated plastic used in estate agents' "For Sale" boards). Many of the models were of jet protoypes which, by their nature, tend to have small wings and consequently high wing loadings. This is no problem on high lift sites like the Orme but not so appropriate to the more modest hills and lighter winds which I tend to frequent.

There were though plenty of other types being flown. One which caught my eye was a Hurricane. It turned out that this was an as yet unflown prototype built by Matt Jones. The lift on the day was light by PSS standards but still pretty steady and reliable so a maiden flight was attempted. This did not go well, the model proving to be seriously tail-heavy, descending down the front of the hill in a series of stalls. By a combination of skill and good fortune, Matt landed the model on a small grassy outcrop halfway down the hill with no damage sustained. Some while later, after the retrieval party returned, lead was added to the nose and a number of further flights were made. Once properly balanced, the model flew well.

Then, in 2017, RCM&E published a plan for an English Electric Canberra for PSS. The Canberra, like the Vampire, is an aeroplane that I remember seeing in the Lincolnshire skies in my schooldays and I was quite attracted to the idea of building one. However, at just over 43" span, it seemed a bit small for my purposes but by now the PSS itch was beginning to need scratching. Then I discoved that the Hurricane had been chosen as the subject for the PSSA's mass build of 2018. . .

May 2018
I usually try not to undertake a significant build over the Summer in order to give priority to getting out flying. I'm not quite sure that I can defend the logic but somehow I used this concern to justify buying the short kit from Sarik Hobbies. This includes pretty much all the shaped wood parts, a canopy and a moulded nose - as well as the plans of course. The wood is of pretty good quality so, after a bit of online shopping for bits and pieces, I made a start on the wings. These are built on the lower skins of 1/16in balsa, a process aided by the fact that the rear part of the wing section is almost flat.

As drawn, the ailerons are driven by a single central servo via long torque rods. I decided that wing mounted servos seemed like less trouble so I mounted Corona DS939MG servos through the appropriate ribs.

The other modification made was to the dihedral braces which join the outer sections of the wings to the flat centre section. These are supplied pre-cut to a depth that implies that they should be fitted after the wing has been fully sheeted in, rather as one would with a veneered foam wing. On a built up wing though, my personal preference is to fit them internally. This avoids the need to sand the edges of the ply braces against the much softer balsa skins and also enables one to ensure that the brace is clamped securely to the spars when it is glued into position.

To increase the gluing area further, I fitted a piece of 6mm balsa between the spars at the same time.

After a pretty miserable early Spring, May turned out to be an excellent flying month, so building so far has been a fairly leisurely and intermittent affair. However, having the luxury of pre-cut ribs has meant that the basic structure of all three panels is complete and they can be clipped together for a first dry-fit of the joints.

For a bit of additional interest, I decided to incorporate working landing lights. One advantage of the PSSA mass build going on is that there are several people coming up with ideas and sources for bits and pieces. So it was that I was alerted to Ross Mansell of Lighting for Aeromodellers. He was very helpful and supplied two Powerchip 5mm LEDs, complete with appropriate resistors and a pack of 10mm reflectors.

The last achievement of the month was making the cutouts in the leading edges and temporarily wiring the LEDs for testing before the wires get buried in the wing.

June 2018
With the wiring installed and the dihedral braces in place, the top surface of the outer panels was then sheeted in. I opted to do this in two stages, joining the panels along the main spar. During this process, a 1/16 x 1/4in strip of balsa was placed under the false trailing edge to induce the recommended washout.

There has been a bit of discussion on the PSSA forum about the need to induce a twist into the solid balsa ailerons, by use of ammonia or steam. I reckoned that there was just enough surplus depth on the trailing edge stock to achieve the required shape by judicious planing and sanding. This picture, taken from behind the wing shows the result, which I think should be okay. The bonus of this method to my mind is that avoids the risk of ending up with a wavy trailing edge.

The tips, trailing edges and leading edges were fitted to the outer panels next, in order to minimise the amount of work to be done on the unweildy one piece wing. The tips were only roughly shaped at this stage though, in the hope that the inevitable hangar rash that will still be incurred can be sanded out before covering.

Then the big join-up could be put off no longer. The dihedral brace was clamped to the spars which were spaced with 6mm balsa as for the outer panels. The inboard R3 ribs were fitted after the panels were joined. This way there is no problem in getting the pairs of R3 ribs aligned!

The last step was to sheet in the top of the centre section. This does require a bit of care and patience since the sheets have to be fitted precisely between the outer panels. Indeed, it would appear that I was concentrating so hard on the job that I forgot to take any photos.

So, with the wing more or less built, I swapped the plan sheets over and contemplated the fuselage. The nose section is built out of ply around a balsa battery tube. This slots together quite well but there is always a bit of a 'fits where it touches' feel to such structures, so a few scraps of triangular section balsa were used give a bit more gluing area.

So, a reasonable month's progress. I reckon I'm still on schedule for the September mass build fly-in. I won't be making the trek up to the Great Orme but it would be nice to fly the Hurricane in virtual formation on the same day down here in the south.

July 2018
Construction of the fuselage itself starts in the normal way by joining the fuselage sides on the formers around the wing seat area, then pulling them in around that battery box assembly.

A slab of 10mm balsa is applied to the underside immediately in front of the wing seat, then the foremost section is built up out of more thick balsa before all being sanded back.

The sides were then pulled in onto the aft fromers. The 'official' way of building this model is to first join the lower and upper fuselage side pieces (both of 1/8in balsa), fit the lower sections onto the formers and then mould the upper portions into shape having soaked them in ammonia.

I've read about this ammonia process several times and, whilst I have no doubt that it works, I can't say I fancy the idea so I'm concentrating on the lower half first and plan to plank the more curvaceous upper surfaces later.

Aligning the tailplane with the wing is always an important step so it seemed like a good idea to sort out the wing fixing before tidying up the back end of the fuselage.

The wing mounting plate is shown as 6mm ply on the plan but it is supplied in the Sarik kit as two pieces of 3mm to be laminated together. This makes for a fairly weighty lump of wood but, since the plate does stiffen up the fuselage at an otherwise vulnerable area, I didn't want to make the plate any smaller. I did though save a gram or two by only doubling up the front half of the plate, where the bolt actually fits.

Some while ago I bought some 6mm threaded inserts (from the excellent Modelfixings.co.uk) so I thought this would be a good idea to see if they work as an alternative to the traditional 'T'-nut. My main concern was how to ensure that the insert was properly aligned as I started screwing it in to its hole. In the event, this was simply achieved by temporarily fitting the wing, pushing the bolt into position then running the insert onto the bolt a couple of turns before driving it into position using an allen key. Acutally far less hassle than fitting a T-Nut.

The wing seat took a little fettling to achieve a fairly good fit and happily seemed to align nice and square to the fuselage.

Before closing in the bottom of the fuselage, it seemed like a good idea to get the servos and snakes installed. I'm using smaller servos than shown on the plan and found that they can be mounted on ply bearers which rest on the top of the wing seat doublers. Those bearers by the way were made simply by bisecting the unused portion of the second wing bolt plate lamination which was oddly satisfying. Looking again at these photos, I wonder whether I'm a bit over zealous in securing snake outers!?

To enable the lower corners of the fuselage to be rounded off, 3/4in triangle stock is to be fitted to the fuselage sides. I had only 1/2in in stock so had to build up the lower face afterwards. At this point I was about to close up the underside with 5/16in balsa as per the plan, then a posting appeared on another build thread reporting that, to balance his Hurricane, the builder had needed to add 1lb of lead to the nose.

So, with a timely reminder of the importance of keeping the tail end light, I added another 3mm of balsa to the triangular strips and also to the formers before sheeting the underside with 3mm balsa.

I had just set to with the razor plane to round off the underside corners when I remembered having been caught out this way once before - fitting the wing fillets around the trailing edge area is much more easily done before making the fuselage too curvaceous. So, the razor plane was parked and bases for the wing fillets were made out of 1/64in ply and fitted, followed by a couple of supporting formers and a 1/16in balsa skin. I find this aspect of the build is always a 'cut and try' operation and in the event none of the supplied pre-cut parts were used.

For most of the building I try to work with the mindset that the use of filler is an admission of failure. However, wing fillets are one area where I long ago abandoned that doctrine so, once the basic structure was in place, the ply base was trimmed back a bit and a good dose of filler applied to blend everything in. I was tempted to carry the fillet on over the front portion of the wing but I know from past experience that it's a lot of work and results in a shape that is practically impossible to film cover. So, just a smear of filler as a token gesture is all I've done.

That washer under the wing bolt is temporary, by the way!

So that's it for another month. I think the time has come to turn my attention to the top half of the fuselage and the big decision - to plank or not to plank?! This page is already far too long so please click here for part 2.