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Rubber powered Curtiss F9C Sparrowhawk



If any of you have been waiting for the Sparrowhawk plan to finally appear, I must commend you on your patience - you have waited a long time! Anyway, at last it is done, and you are welcome to download it. The model was designed specifically to suit the BMFA indoor scale rules, so there is far more structure in there than a model designed for maximum duration. Rib spacing on all flying surfaces is scale, and all control suraces hinged. As I was working on it, I knew it would only have to stay up for 15 seconds to get a qualifying flight!



The only intentional deviations from scale are an enlarged tailplane and a touch more dihedral (about 1/8" extra on all wings). It flies in a very stable fashion, and as you have probably read elsewhere, won the open rubber class at the 2004 BMFA Indoor scale Nationals

There are bound to be some areas on the plan that are not described fully, so here are some close up shots of what I think might be tricky or unexplained areas.



Though not mentioned on the plan, I made the trapeze hook gantry removable by gluing short wires in the bamboo legs, and aluminium tubes let into the sheet next to the upper wing root ribs. The wires are a loose fit, the theory being that if the model hit a wall, the whole assembly would just spring off.



This photo shows the shape of the front upper wing root fairing



and this the rear upper wing fairing. I carved both from soft balsa, but you could also use foam.



The lower wing rear fairing is a tricky little thing to shape.



The undercarriage strut arrangement is probably not very clear on the plan, so hopefully this photo will help. I could not think of an easy way to spring it, so the whole thing is rigid. This has caused damage to the surrounding structure on a couple of heavy landings, so beware. The wire runs through the front struts that join the pants to the lower fuselage.

Other things to notice here are the doubled rigging wires (fishing nylon) and the way the front wires pass through a slot in the outer undercarriage strut. Most odd, but that's how it was.



Finally here you can see an underside view of the upper wing fairing, and the thin card panel I added behind the cowling to simulate a metal panel on the real aircraft.

Although I have noted on the plan that the exhausts are from balsa, looking at this photo reminds me that I actually used plastic tubing. This means they are straight when they should be slightly curved, but at least I have hollow exhausts!

If you have any specific questions about the the model and its assembly, just drop me an e-mail .

You can read more about the model here (rubber, prop, finishing etc.)



To read and print the pdf file you need Adobe Acrobat Reader, which is a free download from www.adobe.com

The plan should print off full size if you set your printer settings to A4 paper, even if it has got different sized paper in the printer. If in doubt, check against the small T shapes on the plan sheets which are spaced 50 mm apart.

Click here to download plan in pdf format (108 KB)

Click here to download plan as zipped bitmap files (146 KB)





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