Seamaster II (oz5899)

About this Plan

Seamaster II. RC sport seaplane model.

Quote: "A practical seaplane for .20-.25 size engine. Seamaster II, by Ken Willard.

The Seamaster II was designed expressly to fill a void in the existing designs for amphibious radio controlled aircraft. In the past, there have been several designs in the .049 to .15 powered models, and in the .40 to .60 size jobs. For some reason or other, the power range from .15 to .30 has been neglected - perhaps because models in this power range were not as popular as the other sizes. Now, however, engines in this displacement category are becoming increasingly popular due to their economy as well as their improved reliability.

Couple those factors with the rapidly rising popularity of seaplanes and flying boats, and a .20 to .25 powered flying boat design is a natural. Add a removable landing gear so the model has the versatility to fly off water or your favorite runway, and you've got the best of both worlds. The Seamaster II fulfills that requirement, and is a good intermediate trainer as well.

And why is it named the Seamaster II? Simple answer; most of you are aware that I designed the Seamaster Sport 40, so named because it uses the wing design and stab design of the Headmaster Sport 40 (oz5877) which was published some time ago in RCM and later put in kit form by Top Flite. Well, even before that, RCM had published the original Headmaster (oz1977), a smaller version which used .15 to .35 size engines, and also was kitted. Well, if you're going to design an amphibious flying boat for that size engine, I say to myself, why not use a well-proven wing and stab combination, and mount them on a flying boat hull? So I did. Not too long ago, Top Flite had updated the Headmaster (the smaller one) and identified it as the Headmaster II, so it seemed logical to me to call this new flying boat the Seamaster II.

Mind you, it is not a scaled down version of the Seamaster Sport 40. On the contrary, it is a totally different design. Full planing hull instead of boat-tail, vertical sides instead of tumble-home - which makes it a bit easier to build - and a T-tail to keep the stab up out of the water when taxiing. Finally, the hull bottom forward of the step extends out from the sides to provide a combination chine and spray rail configuration that gives excellent transition for displacement to planing mode. It also gives the model good handling characteristics in a comparatively heavy chop. You'll love the way it handles, both on the water (or runway with gear attached) and in the air. Finally, its simple construction makes it easy to build, easy to repair, and easy to carry around.

There are a couple of things worth mentioning before you start building the Seamaster II. First, with respect to the wing. Although the construction is essentially the same as the Headmaster II wing, there are minor differences, and one major difference.

The major difference is in the amount of dihedral and the addition of ailerons. True, you could fly the Searnaster II with rudder and elevator only, but the performance would suffer, so I don't recommend it. Use the dihedral shown on the plans. Even that amount is not really required with aileron control, but it 'looks right.' And some dihedral does help prevent the wing tips from dipping in the water when taxiing crosswind; the tip floats do the rest.

The other point worth mentioning is that it has been my experience that most modelers make deviations from any set of detailed plans - particularly in radio and engine installations. Therefore, the installations shown on the plans are largely schematic in nature. You may have a different size set of servos, or radio, or battery - and you may want to use an engine that has a slightly longer crankshaft so the prop will be further forward. No matter; it isn't critical. Mount your equipment where it fits best. Just be sure, when you do, that the center of balance is not moved too far one way or the other. Keep it within a quarter of an inch either forward or aft of the location shown for best performance.

Finally, if you don't want to make the model amphibious, and just fly it as a flying boat, you probably will have to add some ballast in the nose, it will depend on how you install your equipment.

Look the plans over carefully before you start - and particularly observe the construction sequence for the hull. It will save you a lot of headaches when connecting the flex rods to the control surface and the flex cable to the engine up on the pylon..."

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