Grumman Tigercat (oz14679)
About this Plan
Grumman Tigercat. Radio control semi-profile scale twin model. All-sheet design, with Jedelsky wing construction.
Direct submission to Outerzone.
Update 14/7/2023: Added article, thanks to RFJ.
Quote: "Rip round the sky with the Projed Grumman Tigercat - a 34 in span Jedelsky-wing, profile model for two 0.10 (or 1 to 1.5cc) engines and 3 - 4 channel radio. Executed by Jeff Barringer, designed by David Boddington.
There is nothing like the sound of a twin-engined model in full song, the beat of the two motors in 'sync' stirs the blood and brightens the eyes. But - and there's always a but - what if one engine cuts at an inopportune moment? We have all seen, or heard of, the disastrous consequences when one engine fails, the model is in a spin before the pilot can react and the result is often fatal.
As a general principle, the smaller the twin-engined model, the more dire are the consequences of a one-engine situation. The Tigercat is not a large model and so it was with more than a little trepidation that I contemplated the almost inevitable occurrence.
We chose to fit diesel engines (PAW 1.49s) to the Tigercat, partly because they were immediately available, partly because the PAW mufflers are conveniently located and can be reversed - but mostly because I love the smell and mess of oily diesels!
Usually, when properly adjusted, they are reliable and non-critical; with this pair we didn't have the time to set them up individually and they decided to misbehave. On the first cut the starboard engine failed with the model at the far side of a right-hand circuit. The first intimation of this was a slight slowing down and a modest turn to the right. Not knowing for sure that one engine had stopped I applied a little left aileron and, keeping the speed up with level flight, continued with the circuit and flypast. Sure enough, there she was with the starboard propeller stopped. This confirmed that I had been turning towards the dead engine, not a recommended practice, but as it turned out, quite safe. My heart lightened considerably as a result of this experience -one which I would have been loathe to try deliberately.
Since this first single-engine flight I have had two more occasions where the starboard engine has flamed out, and one when the port engine stopped. With the former situation the Tigercat can be held with aileron and slight rudder correction. Port engine failure calls for some rudder but, most importantly, the warning of engine failure is sufficient to give ample time to make the control inputs. In both conditions it is possible and safe to carry out a full circuit on one engine.
Why should the Tigercat be such a pussy-cat on one? The model is certainly not a lightweight, so that is not the reason. My view is that it small enough to get into your car without dismantling, large enough to give a sparkling flight performance. Needle valve assemblies and silencers have been adjusted on the PAW diesels to suit the left and right hand locations.
derives from two design features. One is that the profile nacelles present much less drag than would be the
case with a fully rounded cowl. However, possibly the main contribution is the Jedelsky wing. It is surprisingly efficient and the method of construction with the swept trailing edge provides automatically for generous wash-out in the wing panels. This eliminates the risk of a wing drop and resultant spin.
Colleague and equally enthusiastic aerophile Jeff Barringer built the prototype model; he explains how he was conned into action.
Intrduction: Easter Sunday in front of spectators is probably not the best time and place to demonstrate for the first time a new model, much less a radical scale design of 34 in span, weighing over two pounds and with two 1.49cc diesel engines. But there we were, both engines screaming, the modellers watching in eager anticipation, and the Designer/Test Pilot urging me to hurl the monster into the wide blue, to whatever fate had in store..."
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User commentsOne of the prettiest airplanes that ever braved the winds - a close second to the DH Hornet in that respect! - this plan's top view makes it look like a Hampden!
Miguel - 14/07/2023
Going to use these plans to make a garden wind vane.
Otto - 14/07/2023
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