Korda 25 (oz3319)

About this Plan

Korda 25. Rubber cabin model.

Quote: "To the first free full size plan, a very welcome one for Vintage fans, Harry Purser's Korda 25. As the name suggests it’s a 25 in wingspan version of the classic Korda Wakefield. Not quite a rib for rib replica... with a standard plastic propeller it is a good looking small field flyer for calm summer days."

Update 08/12/2020: Added article, thanks to Algy2.

Quote: "Korda Wakefield Replica. Build Harry Purser's reduced-size version of the famous model and fly it - just for fun.

The Korda Wakefield has always appealed to my eye, but as I am anything but a competition flyer I find that full sized Wakefields are too large for my purposes. I therefore chose to produce a reduced sized version with a wing area similar to the Keil Kraft Eaglet (oz597). No attempt has been made to provide a rib for rib replica and a standard plastic airscrew is used. The result is a good looking small field flyer ideal for calm summer evenings.

Building: I have tried to include all necessary details on the plan as ownership of the plan in the future does not necessarily mean ownership of the relevant issue of the magazine for the instructions. Anyone who has built similar models should have no problems as the construction is entirely conventional. Careful selection of balsa will help in final weights, but do choose strong and stiff material for longerons, spars and leading edges. I still prefer balsa cement for balsa construction but Cyano is useful for other materials providing that it is used sparingly and parts properly aligned before application.

Please use packing pieces under the front of the trailing edge to obtain the required wing section. I had intended to make the tailplane and fin detachable but this was not so simple and neat in practice, so these parts were tacked in place (very lightly) with Cyano to allow adjustments for trimming. Only when the trim is in order should the tail feathers be more firmly fixed. Even then they should be knock-off-able, so don't over do it.

Care is required when covering and doping to avoid unwanted warps but do not forget the wash-in to the right hand wingtip (raise the TE 1/8"). Also do please ensure that the covering properly adheres to the undercambered wing ribs or you may as well cut flat bottomed ribs, which I think would spoil the model.

Flying: The plan shows all revised angles and centre of gravity position as found necessary during trimming. The model has a similar performance to the Eaglet and Achilles, perhaps more predictable than the latter. I started with no downthrust and quarter chord centre of gravity and, whilst the model flew, there was clearly scope for improvement. Downthrust was applied and both wing incidence and tailplane elevation angles increased. To improve the glide the

centre of gravity was moved rearwards by fitting a small amount of lead in the rear fuselage. With a small amount of wash-in on the right wing tip and slight fin offset the model now flies quite smoothly in right hand circles of about forty metres diameter. The glide is not particular good and I do not anticipate losing this model in a thermal - but a name and address label is always a good idea. Please understand that I usually fly radio control aerobatic and small scale models (plus the occasional helicopter) so my models are not noted for their lightness. Power is provided by four strands of one eighth inch rubber pre-tensioned to suit the fuselage length. There are no doubt experts about who are capable of trimming this model to handle more power with a corresponding increase in performance.

Conclusion I am well pleased with this little Korda which suits my liking for simple, economic modelling with very little preparation required for (often unplanned) evening flying sessions. It's well worth persevering with careful adjustment and trimming to obtain the best results. Careful building will be rewarded by owning a very elegant little model with a pedigree to suit. My best wishes to potential builders."

Supplementary file notes

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