Seagull Chipmunk build SEA304(Y for RCAF yellow covering.)

[Mike.K 60]

As a mental relaxation break from building my second scratch build, Rothmans colour schemed Stampe, dispersal of another £350 to our Rob at Avicraft landed me a 80"/2032mm Seagull ARTF Chipmunk kit resplendant in the bright Cub Yellow colour of Royal Canadian Air Force ab initio livery. Great for dull days or at flying sites which have tall green tree surroundings. Models can tend to disappear on landing finals against such backgrounds and I`ve taken to putting yellow strips on leading edges of many of my other models to overcome the issue. This Chipmunk goes one better...its all bright yellow! Seagull also market a grey and green camoflaged version but I instantly rejected that as camoflage was the last thing I wanted!!

The kit requires a 120FS or suitable 20cc petrol equivalent or larger motor. Deano on You Tube flys one with a Laser 155 and it is best described as having a surplus of power..... Another modeller has fitted a 180 FS motor which the airframe apparently tollerates without disintigration. Certainly the examples I`ve seen flying on videos including electric versions, seem beneign in character and don`t seem to fly with any malevalence.

My example will be moderately powered with a Magnum 120FS glow engine. This Magnum is a badge engineered version of the well known SC or ASP engines. As I understand it, engines destined for the North American market sector seem to be known as a Magnum. Andrew White at Just Engines assures me there is no difference in parts or mechanical specification so parts from ASP/SC or Magnum may all be interchanged across the motor range. That said, the Chinese factory producing these motors has now closed so parts are getting somewhat scarce. In some instances Japanese OS parts fit the Chinese engines although thay tend to be rather more pricey than the cheapo Chineese components.  If you have a pile of Chinese engines and want to keep them functioning, buy parts immediately from JE BEFORE they run out. I`m told it won`t be long until that situation occurs.

The kit assembly went quickly and easily with no issues other than to note that I considered the fuel tank floor to be too high for my tank and engine combination. Ideally the centre line of the fuel feed pipe exiting the fuel tank should line up with the carburetter spray bar. Too high and the tank will tend to flood the carb and fuel will leak wastefully onto the ground. In addition the engine may run rich or lean during positive or negative G aerobatics. I chopped out the tank floor and lowered it to my needs. A second floor was installed above the tank and suitable extra reinforcement or modifications added as needed.

This Chipmunk suffers slightly from the same tail heavy build condition as the big Seagull produced Stearman bipe that I built a year or so ago. The tailplane is skinned in plywood and that directly causes weight and balance problems. Like the unit found on the Stearman, this tailplane is built to be able to swat a cricket ball. It is somewhat overbuiilt and several modellers have complained about this on Forum sites. Short of building a lighter tailplane, moving elevator and rudder servos forward and installing light weight carbon fibre push rods, the tail heavy condition cannot be avoided. Some six ounces of lead sheet are now located directly in front of former F1 together with a 2600 6v NiMh radio power battery.

It is also worth noting that all modellers that have made comment on the various Forums, all suggest the CofG be moved forward from 130mm from the LE at the root to 115mm at the root. That immediately helps the model towards improved and less reactive initial flying. My installed six ounces of lead obviously help towards achieving that desirable condition. (Yes, I do cuss the weight of the tailplane and may indeed later move the servos forward and install lighter carbon pushrods at a later date...I`ve no objection to lightening a model as a mass.)

So that is how my model turned out and I`m not surprise the tail heavy situation occured. Dependent on how this model performs once it has flown, I`ll decide what weight shifting and removal might be required. Many kit makers fail to get the C of G position to a sensible place when they write their build manuals. Quite why this issue constantly crops up is behond my comprehension.

The build was quick and reasonably straight forward. Only the tank from move and the C of G rework spoiled what would otherwise have been a five star kit. I`ll give it four stars only in view of these problem areas. All issues however are curable...its just that it is irksome to have to go to such lengths when you pay £350 for an ARTF kit....yes and that is with also having to stump up for the radio gear, IC motor or LiPo batteries and a chunkly electric motor. Total cost then is probably £750-£800 to get to a flying condition.

The model assembled and modified in just three ten hour sessions over three days. The results can be seen in the attached image selection.

More info once I`ve flown the model.

Mike

Edited June 12 by Mike.K
Typo corrections.