Harmon Rocket III


A three-way review appears in the November 2011 issue of RCM&E. It's an attempt to place three similar low-wing models together and see if they're comparable and would all suit a low-wing beginner. This, the Harmon Rocket from Seagull is one of them but what follows is a stand-alone assessment of the model.

First introduced in 2004, Seagull’s Harmon Rocket hasn’t appeared in the pages of RCM&E so it’s nice to have the opportunity to examine this popular low-wing trainer/aerobat. The model draws inspiration from the full-size machine designed by John Harmon which you’ll have quickly surmised, is closely based on the Vanns RV-4. A development of John’s two-seat Rocket II, the III is built for speed and speed alone so no surprise that the slick machine is capable of 250-300mph. The kit has remained in production for seven years, a testament to its popularity and Seagull has ensured that build quality has improved in line with the efforts they’ve made with newer releases.

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This Rocket is for standard two and four-stroke i.c. engines and, while an electric conversion is perfectly feasible, this kit pre-dates Seagull’s policy to include an electric conversion kit while a removable top hatch isn’t in evidence so wing removal will form part of the battery change routine.

Now, I’ve got a little bit of a problem with this model and at the same time it’s not really a problem at all. Cast a quick glance and you’ll see that a servo for rudder and two for elevator are piled right down at the tail – it looks clunky and adds weight at the rear, weight that’s not needed there. And here’s the thing; there’s bags of room in the fuselage for plenty more servos and, like me, you’ll need to add nose weight to balance the model, perhaps a trifle more than the 80g my SC .52 demanded, if fitting a .46.

The pilot figure is horrible, far too small and a candidate for replacement.

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As I say, it’s not critical, the wing loading never creeps into danger territory but those protruding black blocks do seem a bit of an eyesore on what is a very pretty aeroplane while the dual elevator servos add an unnecessary mixing requirement although the elevator joiner included in the box (yet not referred to in the instructions) could be harnessed to reduce the elevator servo count.
The instruction manual hasn’t kept pace in the undercarriage dept either – the undercarriage legs now bolt flush with the underside plate instead of slipping through an aperture and exhibit a slightly forward rake angle. It’s not a problem though and the laser-cut airframe slips together effortlessly enough, fit and finish is good, the hardware fine too.

Seasoned Rocket campaingners often point to the spats as a source of weakness – fibre glass they may be but it’s pretty thin stuff. A problem then? Well I’m not so sure, I’ve found that this means they’ll flex rather than crack when the going gets tough although I’ll admit to having a smooth grass surface from which to fly, just as important, wheel clearance is generous.
A long cowl means there’s plenty of room for any .46 – .60 size two-stroke although the slim front end means a good deal of trimming to accommodate a standard silencer. Do it though or fit a Pitts muffler. A four-stroke would be fine although down-to-earth sportsters like this seem at home with a two-stroke doing the pulling.

As far as pre-flight prep is concerned, use the recommended C of G range – it works well. Control throws should be at the lower settings if this your first low-winger while the higher suggestions should suit intermediate and experienced pilots. A little sprinkling of exponential can be added to suit individual taste.

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Ground handling is excellent where the revised undercarriage arrangement no doubt helps and, with a smidgeon of rudder correction, the model will rise gracefully after a short run. The Rocket tracks well, it’s predictable and safe with the .52 providing just the perfect amount of power. Low wing tyros will be fine using a good .46 but I’d strongly suggest that experienced pilots consider the larger motor.

Ground handling is very good.

The model will happily accommodate all skill levels although, as I say, experienced pilots will find the low rate settings deliver a sedate performance that’s hardly in keeping with the Rocket’s racy persona. On the aerobatic side, the model could be described as entirely traditional in its repertoire yet still capable of impressing non-the-less – big loops come easily helped by the pull from the .52 and the large rudder ensures that knife-edge can be held with very little coupling adjustment. Like many models, a fraction of right rudder helps hold the vertical line but this could easily be mixed out or adjusted with the addition of a little more side thrust.

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Inverted flight requires a little forward stick pressure at the suggested C of G yet here also, the model tracks well and will soon encourage those low inverted fly-bys. Like all racers, the Rocket looks pretty enough through a simple low banked pass, better still, a fast one, yet, at the other end of the spectrum, it’s a very friendly aeroplane with fine slow speed handling, the sedate stall coming at a point where you’ll only have yourself to blame if it comes as a surprise.

Landing the Rocket is just a case of bleeding sufficient speed in the approach, more than you’d at first think, to ensure that the rigid undercarriage doesn’t re-launch the model at every touch down. A low, fast downwind dead-stick situation has been proof of the Rocket's ruggedness. Faced with a model that would have ended up in the boundary hedge, I yanked in some elevator and pulled her round, the ensuing turn killed all speed to the point of stall dumping the model down from 4ft or so yet enough only to crack the cowl. 

This Harmon Rocket III is suitable for competent beginners moving up from a high-wing trainer or for anyone seeking a straightforward low wing aerobat. I’d just quantify the first sentence though. The words ‘competent beginner’ means just that though – a pilot able to fly a trainer in any weather, and land through a cross wind.

Clearly Seagull need to revise the instruction manual and box art to help builders appreciate production revisions. The Harmon Rocket has sold very well over the last few years and it’s not difficult to see why. It’s well made, strong, attractive, flies well and remains exceedingly well priced for a semi-scale model. In these days of strictly defined model flying genres you could argue that the Rocket is a machine that’s difficult to categorise, perhaps one that doesn’t know what it wants to be, yet thousands of satisfied pilots are testament to the fact that not every model needs a badge, the Rocket is fine being just what it is.

Name: Harmon Rocket III
Model type: ARTF sports
Manufactured by: Seagull
UK distributor: J.Perkins Distribution
01622 854300
RRP: £117.99
Wingspan: 50” (1280mm)
Fuselage length: 51.6” (1310mm)
Wing area: 558 sq. in.
All-up weight: 6.5lbs
Wing loading: 26 oz / sq. ft.
Suggested engine: .40 – .46 two-stroke or
.52 – .82 four-stroke
Engine used: SC .52 two-stroke
Servos (functions): Ailerons (2), elevator (2), rudder (1), throttle (1).

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