Puddlejumper (oz5910)

About this Plan

Puddlejumper. RC sport Seaplane model. This plan used a Midwest foam wing, so no ribs or wing details are shown.

Quote: "A simple but different flying boat, for the sport flyer. Midwest foam wing and stab, OS Max .10 and a quickly built fuselage and power pod add up to an excellent amphibian. By Ken Willard.

At the Model Aircraft and Trade Show in Anaheim last summer, Jim Newman of Midwest Products showed me their new Cardinal molded foam model. I was intrigued, particularly with the wing. It was the right size for a small, quickly built sport model, which many of you have been asking for. So, back to the drawing board for some ideas.

Let's make it simple, but different. How about a small flying boat, that could be hand launched and landed on grass or, alternatively, could be fitted with a quick removable landing gear? And, of course, it should perform well off water, since chaes the main idea. Out of all this daydrealiling came the Puddlejuniper. A real fun job.

One of the complaints we get at RCM is - Hey! Knock off that phrase, lying construction is straightforward: and give more detailed instruction! - So, let me begin the construction part of this article with detailed instruction on how to build the wing and stab: Reach into your wallet, pull out the price of the Midwest Cardinal foam wing and stab set, go over to your friendly hobby dealer's shop and pick them up! Not in stock? Have him order a set, it should arrive in a couple of days, just as you finish up the hull.

As for building the hull, it is simplicity personified - a straight box slab-sider, disguised to look rounded by the use of 1/2 in triangle stock for top longerons which are shaped so they fair into the top sheeting aft of the wing, and match into the forward hatch block ahead of the wing. The bulkheads establish the side curvature, and the flat bottom gives excellent water take-offs.

The T-tail keeps the stab up from the water - a good idea when you use the foam stab of the Cardinal set, because it isn't quite as strong as sheet balsa, but plenty firm for this model. The leading edge of the fin is curved so the flexible control rod can be epoxied directly to it and still have a radius of curvature which won't cause binding. It looks nice, too.

During the building process, I used various adhesives: Ambroid for the triangular stock, because it carves easily when dry; Formula 4 Hobby-poxy for the bulkheads since it sets fast and seals well; Weldwood contact cement for the plywood bottom forward of the step because it makes it easy to stick it in place. Cut the plywood a bit oversize (run the principal grain crosswise so it's easy to fit to the curve) and then trim after sticking it in place. Caution: Don't use Tite-bond unless you seal over it with dope; otherwise, it'll dissolve on prolonged contact with water.

Maybe it's an over-simplification, but if you look carefully at the plans, you can figure out the way that suits you best in putting the hull together.

The same goes for the engine pylon. ln fact, if you are so inclined, you can buy a Gryphon engine pylon kit for the Max .10 from Model Dynamics and modify it to lit the Puddlejumper. Note that the pylon is inserted into a cut-out in the wing and extends down to the bottom. Epoxy it in, and the center seclion will be even stronger than before.

The canopy, which is a commercially available size, is trimmed to fit the top of the forward hatch and the wing. It is, of course, strictly for appearance, and can be left off if you prefer. I didn't mount my canopy permanently - just held it on with a rubber band over the top..."

Puddle Jumper from RCM issue 07-73.

Direct submission to Outerzone.

Update 26/03/2021: Added wing plan, thanks to Balsaworkbench. This shows a replacement built-up construction.

Quote: "The Puddlejumper from RCM was designed for a foam wing and stabilizer that are no longer available. Here's a plan for a balsa wing to fit this plane."

Update 07/10/2021: Replaced the wing plan supplement with a revised version (fixes some typos), thanks to Balsaworkbench.

Supplementary file notes

Article.
Wing plan.

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