eastlondoner

Hi guys.
Relatively new to the forum, although I had registered quite some time ago.

Back in the late '80's, I was finally in a position to get into R/C planes. I was intrigued by a design called a 'Pipe Dream', a petrol-powered stick design with an aluminium tube for a fuselage, with a pod arrangement around the main wing area. It was produced by Byron Originals, if memory serves me correctly. It kinda stood out from their normal mainstay of big warbirds etc. The 'Duraplane' designs also intigued me a few years later. For some reason the sheer simplicity of the designs appealed, and the in-you-face detour from the conventional balsa/ply zealots also appealed.

I then discovered the SPAD designs and website some years ago. Again, while the simplicity of the concepts caught my attention, I still wanted to have a conventional R/C wing and conventional tail surfaces.

Due to various issues and studies, I had to shelve the hobby until a few years ago. Various other pursuits and interests have limited my flying somewhat, but the challenge to design and build my own super-simple design, which anyone could put together and also somehow bridge the gap between ARTF's and scratch-building, to some extent... How? Well the er.. fuselage is just a 20mm square aluminium tubing, 1 metre in length when bought but trimmed down 50mm once the design work was all done.
The wing is a conventional foam/veneer construction, constant chord and nice, relatively thick semi-symmetrical section.

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6mm sheet balsa make up the tail feathers, with 6mm square anti-warp strips on the ends. Triangular balsa gusseting adds gluing surface area to the boom (with epoxy, after 'scoring' the aluminium and balsa to improve the bonds). The battery pack and receiver are housed in a thin-walled plastic electrical box, and a future design will have one for the tank as well to keep the design a bit neater in appearance.
The engine mount is a laminate of 2x 6mm birch ply sheets, bolted on and epoxied as well, and again supported by balsa gusseting.
Carbon fibre undercarriage and tail skid. The u/c is bolted onto a 6mm birch ply plate, which in turn is attached to the aluminium 'fuselage' with epoxy and 2 countersunk screws, and again supprted by balsa gusseting to spread the load and gluing surface area.

What took the most time, by far, was to make a simple enough way to attach the wing to the aluminium fuz, and I eventually settled for a simple cradle. This consists of an 80mm piece of hardwood, which is 20mm square, thus the same thickness as the aluminium. I then cut 2 wider 6mm ply plates and glued these either side of the hardwood strip. These 'cover' the sides of the alumium tube, so that it can carry the 2x titanium bolts which hold the wing nto the fuz. I then drilled 2x 6mm holes for the titanium wing bolts. I also cut 2x 2mm aluminium sheet plates and glued these onto the sides of the 2 ply plates, to ensure that the titanium bolts don't wear around the the titanium bolts, after frequent removal and assembly. These were also then drilled for the titanium wing bolts, using the pre-drilled ply plate's holes as guides. I then inserted the 2 wing bolts, to ensure that the cradle is secure and square on the aluminium boom/ fuz. It was then ready to be glued ionto the wings.

This whole cradle was held in place by the 2x 3mm ply wing joiners (100mm in length), which had a recess cut into them to help hold the cradle. Part of the foam core was also removed to accommodate the cradle. I then spent time making sure that the cradle was sitting right in the wing before gluing, including 2 degrees of positive wing incidence and all square with the aluminium fuz. Once satisfied, it was epoxied into place. After that, a wing-joining kit was used to further secure both the cradle and wing join itself.

It came out OK, and the wings were covered with Profilm/ Oracover. As this was such a deviation from the usual Stick/ Stik fuz design, yet still similar in concept to the various electric Slo-Stik designs, I used some 'different' Maltese Crosses for the markings, care of stocks of my other interest, i.e. motorcycles.

I love 4-strokes, so settled for Saito's great .62a. I included 3 degrees of side-thrust when I cut the engine mount out of the ply. A small hole was drilled in the front of the plastic R/C gear housing, to feed the small throttle servo lead through and connect to the receiver. Similar slots were drilled at the back of this box for the other servos and to fit the switch harness and charging jack. The plastic container was bolted to the fuz with 3mm bolts.

4mm self-adhesive foam strips acts as a 'seat' for the tank and, importantly, absorbs the vibrations from the engine. Wing seat tape helps prevent the cable tie rubbing directly onto the fuel tank. A thin slot along the plastic container holding the R/C gear lets the cable tie 'loop' around. These slots were all made with the ever-handy Dremel.

The rudder and elevator servos were fitted to a 6mm birch ply cradle and slid up and down the boom with the short carbon pushrods, until the balance point was achieved. (usual third from the leading edge).

I got my good pal Paul to 'maiden' the plane for me, while I filmed the take-off and took pics of low fly-bys with my iffy digital camera. The plane flies well, much to my relief! :-)

Yes, this design is obviously not as light as a conventional fuz construction, but it's also not much heavier, much to my surprise. No covering, sealer, etc.. and hell yeah, it's damn quick and cheap to build that fuz! Yeah, it bridges that ARTF v/s scratchbuild gap in some emphatic way, LOL.

I'm really happy how well the plane performs and I'm keen to build one with a 2 metre wingspan with OS200 four-stroke up front, some kind of ode to that Pipe Dream from Byron Originals that originally inspired me all those years ago.

Any improvements, apart for the use of another cover for the tank? Yup, Paul noted that there may be a slight tendency to drop the wing in turns, even though it's a constant chord and reckons maybe me trying 1 or 2 degrees of washout to compensate on a future design. He reckons maybe the lack of fuselage area may be a factor. It doesn't fishtail or anything, I made sure that the substantial fin and rudder area would keep things nice and straight in flight. Any suggestions? Keen to hear any input.

Regards,
Dave.

eastlondoner

A few more pics; my bad for attaching a few of the same pics in the first post..