Cirrus Fuselage (Wood) (oz9876)
About this Plan
A Cirrus Fuselage in Wood. Plan showing construction of a replacement fuselage for the Graupner Cirrus (oz8532) sailplane, made out of wood (to replace the kit ABS fuselage).
Quote: "EVER suffered a Cirrus fuselage break? Join the club chaps! Cold weather and hard impact take their toll of these plastic fuselages. Here's a way to make your own replacement in standard balsa construction, tough enough to stand up to typical British conditions. Performance-wise it may not match the original in every respect but it does the job well in a model that could be called a stand-off Cirrus. It sports repaired Cirrus wings and tail, but a very much boxier fuselage than normal. The model gets away adequately, but doesn't have the edge that one usually associates with the original. AND it looks nowhere near as pretty!
Now, why didn't the builder duplicate the sleek lines which had probably prompted him to part with hard-earned (we hope) cash in the first place? Well, it's easier to build a box; it is debatable whether there's much to be gained in performance for the effort involved, it's lighter... here, wait a minute. Just what is this game if it's not involved with small refinements and marginal advantages? Put a rule around the perimeters of a box job and an elliptical or circular section fuselage and what do you get? Of course, a greater outline dimension of the box with a greater drag co-efficient, in effect, a bigger fuselage when seen from the front and of a less efficient shape. Oh yes, bigger fuselages imply more material, more material means greater weight, and by now we're disenchanted with the undertakers' favourite section if we cherish any ambitions at all.
So what's stopping us? Well, isn't it complicated? Don't we need to be experts to build smoothies? And don't we need a lot of expensive block to carve away to nothing? Take heart, for the load is about to be lightened. YOU TOO can be the envy of your friends without breaking the bank. And here's how.
The basis of the prescription is a generally acceptable size of component bearing in mind current R/C gear and present popular sizes of models. The draughting methods are so simple as to be capable of reproduction by anyone wishing to indulge individual fancies of style within the general idea. The wood sizes are easily available and formed to the curves required; the rear half of the fuselage needs no formers of the conventional type, but a mandrel is used (this is always a useful commodity for a modeller to have around anyhow, so time spent on this could be regarded as an investment). The mandrel can be of any desired proportion to match a modified front-end. For economy, formers are almost all made in three parts, this allowing careful economisers to juggle the shapes around on the sheet more easily before cutting than when one-piece formers are used.
Construction. Basic sides cut from 3/32in medium balsa, and a crutch constructed using the rectangular strips from the centres of each former. These can be of any convenient thickness so you won't have to carve up any new sheet for these parts. It is advisable to stay with 1/8in or 3/32in stock, medium sheet, or 3/16 in medium soft, or a combination of all or any of these. Just be sure to check that all the X-members fit at right angles to the datum line when gluing in place. The lower former sections can now be cut out. Here is the really sneaky bit of this design. With the exception of F1, all the lower sections have a common radius profile, and a constant depth..."
Note this is not a complete plan for a model. This is a plan showing how to build a replacement fuselage. See the Graupner Cirrus (oz8532) plan for more detail of the full model.
Supplementary file notes
Article pages thanks to RFJ.
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