Rhubarb (oz13832)

About this Plan

Rhubarb. Radio control sport model, for 1 cc engines.

Quote: "Rhubarb. Frustrated at the need to fly in small fields, Tim Rose took matters into his own hands and designed his own answer.

Luckier than most, I have the opportunity to fly my model aircraft whenever I want near our farm cottage. Unfortunately the field I'm allowed to fly in is far from suitable. It is fairly small, gently sloping and surrounded by menacing, plane-grabbing trees (my brothers glider has already been victimised by one such tree). Trying to fly your average sports plane around these obstacles, especially when coming into land, is a bit of a handful, so what I needed was a small, easy to fly and manoeuvrable model capable of flying from this site.

My first reaction was to sift through a pile of free plans I had collected over the past few years, to look for a suitable model but nothing really fitted my exact needs. After a lot of thought, the decision was made to design the Rhubarb. The advantages of small models have been well explained in columns like 'Weekend Pilot' and 'Engine Bay', but the question was how small to make it? I had a spare old PAW 80 (no throttle) out of a broken control line plane and also a set of Fleet Micro Radio gear extracted from a hand launch glider, so I thought I would design it around them.

Small models can often be twitchy and difficult to fly (ever seen Bob Ryan's micro fly? How does he do it!). The Rhubarb had to be stable and easy to fly so I employed large tail areas and moment arm into the design, using the theory of trainers. The rest of the plane is fairly standard.

Construction: The Rhubarb is very quick and easy to build and shouldn't present any problems to someone who has built a few models before. As with all models, especially small ones, try to keep Rhubarb as light as possible. Careful wood selection will help here as well as lightweight radio gear. I used cyanoacrylate glue for most of the construction, except in high stress areas such as the nose and wing joints where I used 5 minute epoxy. The ready to fly weight turned out at 15oz, but anything up to 20 oz will be OK.

Fuselage: The fuselage is made up of a simple box section. First of all, using medium grade balsa, cut out the two sides, wing doublers, formers, strengtheners and hatch supports. Make up F3 using 1/4 x 1/8 balsa. Then glue the wing doublers, hatch supports and strengtheners on to the fuselage sides making sure you have built a left and right hand side.

On to either side, glue the formers F1, F2 and F3 in their correct positions ensuring that they are at right angles to the sides. Use 5 minute epoxy for the plywood Fl. Once completed, attach the other side to these three formers and then glue on the 1/16 ply bulkhead facing.

The tailplane, fin, elevator and rudder can now be cut out of light 1/8" sheet balsa and made up. The 1/8 x 1/8 tips on the tailplane and fin have the grain running in the opposite direction. This stiffens them and also prevents them from warping..."

Rhubarb from R/C Model World, August 1991.

Direct submission to Outerzone.

Update 14/6/2022: Added CAD drawing (in SVG format), thanks to HJ van Tol.

Quote: "Dear Mary and Steve, This model I've put on my 'to do' list. It seems simple enough for me. But I noticed the resolution is a bit low. I set out to redraw some parts and I ended up with a new drawing. Along the way I filled in some gaps. You could consider offering this SVG-file to the modelling community so anyone can correct my mistakes. Thank you for your noble work. Greetings from the Netherlands,"

Update 28/8/2024: Replaced the CAD zipfile with a revised version, thanks to HJvanTol.

Quote: "Hello Mary, Hi Steve, Please replace the earlier version of this plan with this new version. A minor mistake is corrected and it is a bit more refined. It is now...perfect! [Jeremy Clarkson smugness]. Also included are two A3 pages with all the parts. Greetings, H.J. van Tol."

Supplementary file notes

Article pages, thanks to RFJ.

CAD file

This plan is available for download in CAD format.

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