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..."
Did we get something wrong with this plan? That happens sometimes. Help us make a correction
Do you have a photo you'd like to submit for this page? Then email firstname.lastname@example.org
* Credit field
The Credit field in the Outerzone database is designed to recognise and credit the hard work done in scanning and digitally cleaning these vintage and old timer model aircraft plans to get them into a usable format. Currently, it is also used to credit people simply for uploading the plan to a forum on the internet. Which is not quite the same thing. This will change soon. Probably.
This model plan (like all plans on Outerzone) is supposedly scaled correctly and supposedly will print out nicely at the right size. But that doesn't always happen. If you are about to start building a model plane using this free plan, you are strongly advised to check the scaling very, very carefully before cutting any balsa wood.
© Outerzone, 2011-2018.
All content is free to download for personal use.
For non-personal use and/or publication: plans, photos, excerpts, links etc may be used, provided that full and clear credit is given to Outerzone with appropriate and specific direction to the original content i.e. a direct hyperlink back to the Outerzone source page.
Unauthorized use and/or duplication of this material without express and written permission from this site's owner is strictly prohibited. If we discover that content is being stolen, we will consider filing a formal DMCA notice.