Die Fledermaus (oz14523)

About this Plan

Die Fledermaus. Radio control sport model. Twin engined amphibian. Wingspan 61 in, wing area 575 sq in, for 2x .25 engines.

Direct submission to Outerzone.

Update 27/4/2023: Added article, thanks to RFJ.

Quote: "Die Fledermaus, by David Stevens.

For me, one of the joys of aviation history books is the photographic gallery they provide of those magnificent flying boats that graced the skies during the Firs! World War and into the mid-thirties. These craft carried nautical tradition aloft and seemed to fly on sails rather than wings, wings that were often clipper-like in layers. As many engines as proved necessary were hung wherever space permitted, pushing or pulling. Drag was treated vvith obvious contempt, and yet they flew very well, even venturing successfully into many unknown quarters of the world. Would flying machines ever have greater confidence, dignity or presence?

Dornier Doodlings: Thus inspired and with two Leo .25 two-stokes to hand, I started sketching layouts for a practical model that would capture the spirit of that golden age. But, because there's no suitable stretch of water close to home for regular use, it would have to be an amphibian. Large, multi-engine amphibians were neither required nor attempted in those days, but the products of the Dornier Company produced the clues I needed. They made a series of brilliant designs, sleek monoplanes with push-pull engines on top end tiny wings sponsons) below to give stability on the water. Could I devise a 'could have been' design where the wheels tucked neatly into those sponsons?

The doodles looked promising, indeed the typical position that Dornier had chosen for sponsons would also place the wheels in a good position relative to the CG. The wing could sit on the top of the cabin and serve as a lid to keep the water out, whilst the engine pod would - require only short struts. Better still, the distance required between each engine, to enable the propellers to clear the leading and trailing edges, would leave ample space for fuel tanks. The only tweaks necessary were slight sweep-back to compensate for the weight of the rear engine and very large tail surfaces to combat forward side areas and a short-ish moment arm.

The resulting design certainly had character, but wasn't exactly what a modern aerodynamic'st would have suggested. Would Die Fledermaus (German for bat) work just as those old-timers had, or would all those contradictions and compromises conspire against it? Having neither the mathematical mind nor the research facilities to assure the future, ! lifted my pencil with a rather shaky hand.

Experienced Applicants Only: Unquestionably a project for the more advanced constructor, Die Fledermaus could be built from a choice of materials according to personal preference or the desired appearance of the finished model. The hull offers the biggest opportunities. That of the prototype was made of liteply panels over foam board bulkheads and balsa longerons, though 1/8 and 1/16 ply bulkheads would be fine, and 5mm spruce longerons would be easier to steam into shape for the bow contours. Similarly the panelling could be made in balsa or even lightweight metal. Both the wings and tail surfaces offer less choice save in the type of covering material you choose, but the advanced modeller might like to apply ideas of his own.

The plan shows the construction materials used in the prototype, which came out at 7 lb AUW, and flight tests have proved this satisfactory. Whatever materials are used, be sure not to add more weight - excessive pounds ruin the handling of scale and scale-type models.

If you do choose liteply, a better finish will result by varnishing and rubbing down the panels at least five coats!) before trimming and fitting. Ensure that the thin edges are sealed against fuel seepage before you stick them in - purple 'fingers' creeping out after a few flights will spell failure!

Das Boot: The hull is built upside-down on the plan, with the cabin and decking added later. To avoid visual clutter the longerons aren't shown on the plan, but the notches in the bulkheads clearly show where they go. So, first cut out the bulkheads, ensuring the longeron notches are a tight fit for the wood chosen. Now pin down the deck-level longerons. I suggest you take the central one right through the cabin space, cutting it out later only when needed. Glue the bulkheads down using waterproof adhesive, ensuring that they're vertical and have shaped edges and notches to follow the tapers of the hull. Allow to set.

Starting from the rear, fix the lower longerons. Pre-shape those between F6 and the bow by soaking and / or steaming and allow to dry before gluing up. Sand the lower longerons to blend in with the hull shape, then add the strengthening cross-spars between F5 and F6 and the cross-spars for panel attachment at the steps..."

Supplementary file notes

Article.

Corrections?

Did we get something wrong with these details about this plan (especially the datafile)? That happens sometimes. You can help us fix it.
Add a correction