Building a new fuselage for a Fournier RF6B

A Fournier fuselage being built

After careful measurements, a sixteen-foot bench (originally built for another Fournier model) had to be extended by three feet to accommodate the longer fuselage of the RF6B - Credit: Bob Grimstead

Certification issues prompt the build of a new fuselage for the Fournier RF6B. However, the project turns out to be far more complicated than envisioned fro Bob Grimstead...

I had a bit of a puzzle, and a possible solution. My recently-acquired Fournier RF6B G-BLWH was on an EASA Certificate of Airworthiness, with all its onerous requirements and precluding the possibility of incorporating even the most minor modifications. But the Light Aircraft Association’s Chief Engineer, Francis Donaldson, had suggested a way forward by getting my  Fournier on to a (much better) British Permit to Fly. ‘All’ I had to do was build a fuselage. 

Blue prints for Fournier fuselage

In order to move the RF6B from the EASA register to a less limiting British Permit To Fly, building a new fuselage was “all” that Bob needed to do. Of course, though, the devil was in the detail - Credit: Bob Grimstead

Obtaining blueprints 
Obviously, I first had to obtain drawings. I found that Club Fournier International (CFI) President Michel Leblanc could sell me a CD containing all the drawings available−a total of 248 factory blueprints which had been reduced from full-scale to A4 size, scanned while in transparent sheet protectors, saved as tiffs and compressed into zipped files. The results were generally lacking in contrast, and sometimes wrinkled or cropped. 

So I had to open these large files in Photoshop and take half an hour over each, resizing it to improve brightness and contrast. The bigger ones were so detailed I had to crop off and enlarge one quarter or even just a small portion of them to obtain a legible result before saving them as smaller jpegs. This was a laborious and time-consuming process. 

Even decrypting, reformatting and tidying the early version of an Excel spreadsheet containing the drawings’ index took a whole afternoon. I had to translate that index from their original technical French into understandable English. Have you tried translating aviation French with Google? It can be great fun if you enjoy puns, malapropisms and spoonerisms and have all the time in the world. I didn’t, so I resorted to cross-referencing words from René Fournier’s original French and English-language editions of his excellent and informative autobiography Mon Rève et Mes Combats (My Dream and My Aeroplanes) before saving everything in a Word document. 

Bulk head design blueprints for Fournier fuselage

Detail of the original bulkhead design with notes in French - Credit: Bob Grimstead

No instructions and no materials list 
But when those painstaking tasks were finished, I still didn’t have the sort of drawings homebuilders usually get. These were no Bowers, Vans, Jabiru or Ikea-style ‘Fit bolt A through holes B and C in components X and Y’. These were commercial factory production drawings and rather incomprehensible to me. 

Next, I had to work out just how much Douglas fir and Finnish birch plywood I would need. Aircraft quality wood is expensive and not easy to source but, again unlike proper homebuilders’ plans, there was no materials list. I didn’t want to buy too much because that would waste money, but worse would be to buy too little and have to go back for a small additional amount, so I had to figure out this stuff myself over the weeks by poring through those drawings again and again. 

The resorcinol adhesive (Prefere 4050/5750, formerly known as Aerodux) comes in big, expensive tins but has only a short shelf life, so I didn’t want to buy that until I had cut out most of the main components and was ready to start gluing things together, otherwise it would just be wasted. 

Meanwhile, to alleviate my frustrations at having to do all this unnecessary work merely to fulfil a bureaucratic requirement, I distracted myself by roughing out a couple of alternative colour schemes, with the upper fuselage in Oratex yellow instead of its current black, which Francis didn’t like because it might heat up in the sun and affect the glue (although I thought this unlikely, given the many Fourniers operating for decades in hot, arid climates, including my Australian one). I wanted something approximating as closely as possible the earlier RF4D’s original scheme as presumably designed by le maître, René Fournier, and a sixties classic. 

Drawing plans for yellow Fournier

In the design phase, Bob considered a couple of different colour options, eventually settling on yellow - Credit: Bob Grimstead

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The big box full of documentation I inherited with ‘Whisky Hotel’ included Flying and Maintenance Manuals. Both contained three-view and isometric general-arrangement airframe drawings. I made photocopies to sketch out several alternatives, but they all looked oddly elongated and disproportionate compared to the RF4D model, from which the RF6B (my aircraft) had been derived. So I measured Whisky Hotel’s fuselage side between its canopy and the wing’s upper surface, comparing that with the fuselage depth of the RF4D. To my surprise, the RF6B was actually shallower and longer by several centimetres, which is why the RF4D scheme looked so narrow when transposed onto it. So I modified it appropriately. 

There was another problem. I could easily cover the underside with black Oratex because that was comparatively shallow. But I wanted to use one big sheet of fabric over the whole upper fuselage, so there would only be a single joint line along each side, which I should easily be able to disguise by painting over it with a cheat-line. But I know that Oratex fabric, although nominally 180cm wide, is usually a bit more. The fuselage tapers so, while there should be enough yellow fabric to cover the rear part of the fuselage down to the upper cheat line, around the cockpit it might come up short. 

I carefully measured my actual bolt of fabric, and then draped a seamstress’s tape measure over the fuselage. But what on earth could I use to mark things clearly on this glossy black paint finish? I know! Back in the eighties, when I was a budding journalist using a portable manual typewriter, I used gallons of Liquid Paper and Tippex to blot out my mistakes. It came in little plastic bottles with small brushes inside their lids. I wondered if I still had any of that?  

Yes, I did, and it turned out to be the ideal medium, so I could determine that my yellow Oratex would be just wide enough to cover the upper rear fuselage to the back of the canopy and down to the top cheat line. I would need to use another piece for the forward fuselage over the fuel tank, and then extend that in a narrow strip along both sides to overlap the rear area, but that is what I did with my other Fournier (a RF4D) when I re-covered that a few years ago, so I had no qualms there.  

Four small models of Fournier planes

Starting small (and sensibly nerdy)... Bob built, as models, a formation team that included his RF6B, a Zlin, a Fuji and a Champ - Credit: Bob Grimstead

Walter Mitty moments 
Paul Hendry-Smith invited me up to Little Snoring for a reprise of their Oratex application course, and that was very useful. I learned more techniques and how to control better the temperatures required in activating the adhesive and shrinking the pre-painted fabric without making marks on it. 

I am derisive of any homebuilder who obsesses about his colour scheme or instrument panel layout before even starting to nail parts together, believing them to be Walter Mittys−but here I was, doing exactly that. I even cut out a little wooden model with my new band-saw, at approximately one-fortieth scale, to match other models I had already made (a Champ, a Zlin and a Fuji). I was becoming an RF6B nerd. 

I also thought, if I have to re-cover it anyway, why not revert to the white-and-red colours of my other Fournier, RF4D RedHawk, with its wing-top sunbursts? So I coloured in some more drawings, and felt the results were aesthetically pleasing. 

I also had to lengthen my sixteen foot bench to nineteen feet for that new RF6B fuselage. Originally designed for the RF47 fuselage, which is 15.8 feet long, this only just fitted into our garage between my workbench and the main roller door. However, careful measurement suggested that the necessary extension might just be possible, and in reality that turned out to be one of the easier jobs. 

I simply hammered, wedged and screwed two five-foot lengths of well seasoned four-by-two timber into the rectangular-section ends of my long bench sides. I then covered those extensions with Medium Density Fibreboard (MDF), finally wedging that in a couple of places and screwing it down to ensure it was both rigid and dead level with the pre-existing bench top. Then I painted it white along with the rest of my bench because I intended marking out all the fuselage frames in full size on it before constructing them. 

A man learning to use Oratex for plane building; pictured covering a mock control surface

You can never know enough: Bob took a course on how to use Oratex on his Fournier. Here he is seen covering up a mock control surface - Credit: Bob Grimstead

Orphan model 
Whisky Hotel’s existing fuselage could go on to the floor on the far side of my garage, where I would have easy access to strip off its fabric, remove the upper plywood skin and measure and check my new structural components against the original ones as I made them. But the more I worked around it, the more I hated to vandalise this pristine, jig-built, professionally-made, painstakingly restored, re-covered and painted fuselage. It seemed sacrilegious to scrap it in favour of an amateur alternative constructed by my unskilled hands. 

Then, in December 2018, and to my complete mystification, in the LAA’s magazine Light Aviation, I saw that lots of similar but no more deserving British-registered types had suddenly been allowed to transfer to Permits to Fly, immediately before Mike Poole’s retirement from the CAA. Why weren’t Fournier RF6Bs included? Possibly because the relevant folk in both the LAA and CAA (who should have known better but clearly didn’t) incorrectly refer to the RF6B as an ‘RF6’, and the RF6’s Type Certificate is owned by a big European aviation conglomerate, EIS. 

The RF6 (with no ‘B’ suffix) is a completely different, bigger, heavier, four-seat, O-360 Lycoming-powered and ultimately unsuccessful aeroplane of which three examples were built by Sportavia in Germany. On the other hand, the RF6B (B for biplace) was this smaller, daintier, Continental-powered two-seater of which forty-four were made by René Fournier’s company, le Société de Construction et de Diffusion des Avions Fournier at Nitray in Touraine, France. Although the RF6B has been an orphan for more than forty years with no proper factory support, its Type Certificate recently reverted to EASA ownership. 

Again I pestered the LAA, pointing out this ‘administrative oversight’ and the likely reasons for it, but Francis and CEO Steve admitted that, while they would like to see these un-supported, orphaned aeroplanes operating on Permits to Fly, ‘their hands are tied’ by EASA and apparently particularly ICAO intransigence. The best advice they could then offer was “Maybe after Brexit...”. 

A year later there was some unexpected hope of progress because the Slingsby T67 series of aeroplanes directly derived from the RF6B (indeed the first handful of wooden T67As were RF6Bs, but assembled in Yorkshire) had been orphaned by Marshalls of Cambridge, who had latterly held their Type Certificate. The LAA was working towards getting the first eleven T67As (of which only three were still airworthy) on to Permits to Fly, so I desperately tried to piggy-back the three British progenitor RF6Bs on to that process. 

Sadly, shortly afterwards the head of the CAA’s engineering department, a former homebuilder and ‘our type of chap’ left his post and the whole thing came to a halt again. Government Transport Secretary Grant Shapps then declared that Britain would leave EASA, so maybe there was still a chance. Meanwhile the remaining years of my flying life are ebbing away. 

An old Fournier plane

'Whiskey Hotel' in a previous life, years before Bob undertook the restoration project (which was actually aimed only at getting her onto the British Register) - Credit: Bob Grimstead

The weight of papers 
Whenever I consider this RF6B fuselage that I’m supposed to be building, or think back to that previous RF47 project, or even dwell on my RF4D reassembly that preceded it, the same de-motivating thoughts infect my mind. I now realise that dwelling on these frustrations is what has caused these projects to progress so slowly, but I don’t think I’ve mentioned it in my articles. I hate to admit that mere negative thoughts could have such a serious retarding effect on my progress, but they really do. 

The thing is that, time after time when I went to pick up my tools to move forward with any of these three projects, I found myself sighing a huge sigh and only starting slowly and reluctantly because so often I was either undoing something that should never have been done in the first place, trying to repair something that should not have been so wantonly damaged, or attempting to move forward on a path I know is both illogical and impractical merely because it is a bureaucratic requirement. 

So late 2019 should have seen me building an RF6B fuselage, but every time I went into my garage and saw that glossy black existing one, I just couldn’t bring myself to strip it, scrap it and make another. Luckily, I am persistent. 
 

A D-EASK plane, grounded

In 2018 a number of aircraft models were transferred onto Permits To Fly, but the RF6B was not included in the list. Did the authorities confuse the RF6B with the similarly named, but different, four-seat RF6 (D-ENNI, and the D-EASK pictured here)? - Credit: Bob Grimstead