Rare Seagull SEA50 Ultimate bipe kit.

[Mike.K 60]

Having rebuilt a rare Ramair Ultimate (Red and white colour scheme) recently, the yearn for a Seagull version still pulled hard. The chances of obtaining the now discontinued Seagull rendition though was pretty slim. I`d despaired of ever finding such a kit, either as a built and may be used example or as a new un-built kit. It`s been about five years since Seagull took the Ultimate out of production and I`d almost given up of ever obtaining one.

A chance phone call to Rob at Avicraft suddenly and quite unexpectedly produced a chap in Selsdon with an unflown Seagull Ultimate that was for sale. Immediate negociation and a super fast arrival at his home sourced a bare stripped out airframe without any hardware fitted. The canopy had a crack in it but I`ve managed to find a replacement via Rob. Other than that damage, the model was in great and almost unmarked condition. This suited my needs to perfection and at a reasonable cost.

The F1 engine mount bulkhead required the blocking up of various mounting holes and other wounds inflicted when the previous owner had mounted his particular power plant. Repairs were made before both sides of the bulkhead were overplated with 0.8mm ply faceing plates to cover up and make good those issues. The motor box sides were reinforced again with ply as these areas have proven to be somewhat weak in service. I also took the opportunity to dispense with link rods which join the upper and lower ailerons together. The model now has four servos operating ailerons instead of two. To achieve this modification, I had to cut into the upper wing panels, remove a couple of wing ribs, then make four new ribs and locate them within the structure before making up ply servo mounts. Obviously replacement of some covering material was also needed to disguise my modifications. Fortunately that was on the upper wing lower surfaces so the overlapped covering replacement doesn`t show too badly.

Another modification was to make new elevator servo mounting points under the tail plane of the model. Use of a big and heavy SC180FS motor dictated some weight shift aft would be needed. I`d considered installing a 120 motor but that size motor has to work hard when flying this sizable airframe. I felt the use of a 180FS would give quieter and more relaxed flying. Removing mild steel push rods from the fuselage took some aft weight out of the equation but moving the servos then added to the situation. I used previous experience to attempt to come up with a reasonable Centre of Gravity. To my joy, the finished model C of G worked out perfectly with the 180FS, muffler, fuel tank, prop and spinner installed together with the motor servo and 2600NiMh power battery all installed as far forward as I could get them.The stated C of G is between 125mm and 150mm aft of the top wing leading edge. Internet Forums suggested the model flies well with the C of G at around 135mm from the leading edge. Pleasingly, my C of G came out at exactly that with no additional lead ballast needing to be used to correct any deficiency.

I`ve mounted the 180FS inverted which almost coincided with cut outs done to the engine cowl by the previous owner. A little more material was removed to suit my engine installation. Most modification work was needed in the siting of the fuel tank which would have been far too high in the fuselage and would have caused significant carburetter flooding if left as it was. The fuel tank mounting plate required to be lowered by about 30mm to align with the carburetter spray bar. Internal structure removal and replacement is not one of my favourite jobs but in this case I had few other options. A 20oz tank provides a reasonable fuel storage given the big 180 sized motor installed.

The model is a very sizable 54" span biplane with a goodly amount of wing area. My slightly smaller Ramair example weighed in at 10.8Lbs and flies quickly and accurately. As expected its landing speed is quite brisk. By comparison, this Seagull version weighs in at 11.7Lbs but is larger and has more wing area. Seagull suggest a finished weight of between 9.6Lb-10.6Lbs. Even with a smaller 120 fitted, I think one would struggle to get the model much below an 11Lb weight. I`m not displeased with an 11.7Lb finished weight with two extra servos fitted and the rather heavier 180 installed. Some examples (dependent of engine installation and placement of servos) have pushed the weight up to 13Lb. They must be quite a handful at slower landing speeds! I don`t expect any issues with my Ultimate at a weight of 11.7Lb.

Construction of this ply and balsa ARTF model follows typical Seagull practice. The model is well made apart from already known weak areas around the F1 engine mount. Those issues are easily delt with. The build of this and several other similar Seagull models is quite straight forward being generally well designed and produced. Whilst more complicated than a typical foam model build, a modeller with some experience, a basic tool kit and some common engineering sense should have little difficulty assembling any of the Seagull kit offerings. If still made and offered for sale by Seagull, this Ultimate model would probably retail for around £430. This represents good value for money with all the hard work done and with the bonus that the model should fly without issue straight from the box. My pre-owned model came to me for less than £200 which makes the purchase even sweeter! Those considering building a Seagull or indeed any other makers ARTF offerings will also need to budget of radio and power plant costs in addition to the pre-covered basic kit.

So this model is now complete and ready for its maiden flight. News on that in due course.

Mike