HM.280 (oz16241)

About this Plan

HM.280. Pistachio scale (6-inch fuse) free flight model, for rubber power. Wingspan 9 in.

Quote: "I first came across a three-view drawing of the HM-280 in a construction article on the British Pou, an HM-14 (Model Builder, April 1981). To me, the more streamlined nose and graceful elliptical wing shapes of the HM-280 had an immediate appeal over the more pugnacious and awkward HM-14. Compared with photos, the three-view of the HM-280 appears to be very accurate, with one small exception in the cowl area. I made this correction in the front view on the lower part of the cowling. This curve appears on the plan but not on the three-view. You can see it easily in the photo.

I won't echo the French newspapers by dubbing this Scale model "everyman's airplane." Beginners should study the plan and perhaps take advantage of some of the technical information and choice construction hints - but save this project until they've honed their skills on easier models. The parasol configuration is very attractive but fragile and difficult to execute and align. I've included enough detail so that seasoned scratch-builders can create an accurate and most unusual WWII Jumbo Scale or Coconut Scale version. A compound gear setup similar to that devised by Bennett and Wetherell (see Flying Models, October and November 1988) would overcome the disadvantage of the short fuselage in the larger versions.

Current Pistachio Scale rules (6 in fuselage or 8 in span) favor a configuration like the HM-280's with its short fuselage and long but wide-chord wing. Lower wing loading, lower prop speed (aided by a large span which allows a bigger prop), and lower flight speed with its resulting lower drag all add up to longer flights. The Miami Indoor Airplane Model Association rules allow single-covered surfaces without penalty, thus saving weight and adding camber. There is enough scale detail on this French military Flea to bring tears of joy to the eyes of the most hard-boiled Seale judge. At the end of this article is a list of my favorite suppliers of every material you'll need to build this little beauty.

Construction: The fuselage of the HM-280 is not the usual slab-sided box with wings poking out of it. Since the cross section narrows toward the bottom, we begin by constructing upper and lower 'decks.' I use tape instead of pins, which makes the longeron curves more accurate. Build the uprights joining the two decks. Add the bottom former. F2A, angled forward as on the side view.

The keel is hot soaked and preformed over the side view. Shape it with your fingers until it stays in the correct curve, then tape it down until dry. After gluing the keel to F2A and the bottom of the tail post, install the keel braces, nose plate, top formers, and arches over sections F5 and Fb.

Remove the crosspieces (illustrated by the dashed lines on the plans) between sections F1 through F6 to clear the rubber motor. Add diagonal braces to the fuselage sides. Add 1M stringers to the front at top and bottom.

The cabin roof can be carved from light foam or built up from .015-in balsa sheet with no difference in weight. I used very lightweight balsa (5.5 to 6.5 lb per cu ft) for all parts except the struts. Try a test break with a few strips of your light balsa. You're looking for stringy, light balsa, not that punky brittle stuff. If yours does test out to be brittle, use thinner pieces of slightly heavier balsa instead..."

Direct submission to Outerzone.

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