Grumman Aleutian Goose (oz1220)

 

Grumman Aleutian Goose (oz1220) by Pres Bruning from Flying Models 1993 - plan thumbnail

About this Plan

Grumman Aleutian Goose. Twin seaplane for rubber power.

Quote: "Twins are tough subjects for rubber power, but this turbine conversion of the Grumman amphibian lends itself well for a freeflight scale subject. Aleutian Goose, by Pres Bruning.

Most people are familiar with the original Grumman Goose with the big radial engines, but when I opened Air Classics, May '74 magazine on page 58, my eyes popped out. An Aleutian Goose with 'projected' performance. Wow, what a startling conversion with long nacelles for the turbine engines and dorsal fin addition, stretched body, and retractable wing tip floats. Ideal subject for rubber power, and handsome to boot.

This conversion was used by the Department of Interior for Alaska survey work. The twin turbos are Garret Airesearch turbines. Must have been a hot performer! I used a three-view drawing of the original Goose and superimposed a side-view photo reduction of the conversion over the original to see what changes occurred in outline and generated new three-views from which to do the model construction.

Construction of the fuselage is a simple box section type with half round bulkheads on top and triangular hull sections below, with 1/20 square stringers added in. To ensure square right angle accuracy, slip in a cardboard square at F3 to be removed later after the stringers have been added. Remember to leave the top of fuselage open from F4 to F7. Finish the fuselage construction after the wing and engine assembly are built up as a unit with the dihedral indicated on the plan.

The covering of the engine nacelles is tedious, so take your time. Cover in strips between each stringer, using Elmer's glue thinned out 50-50, brushed on the perimeter only of each section.

The fuselage covering was somewhat difficult as I pieced the red and white tissue paper pieces together as indicated on the plan with Elmer's glue, sealing it with dope at the overlap before covering the fuselage sides. The top surface of the wing between the nacelles is a similar situation; so be patient when covering this portion.

The tail surfaces were built with symmetrical rib sections. The vertical stabilizer added to the fuselage with butt plates to glue on the horizontal stab halves. Add in the covered dorsal fin.

The last to be covered are the windows. I developed window patterns for canopy and windows on both sides of the fuselage laid out with a ballpoint pen. A thin color key film was made and each windowpane was cut out outside the pen lines and epoxied into place. This technique outlines each window, making the model seem more realistic in appearance. Pilot and instrument panel were carved from blue foam and painted with acrylics before installing into positions indicated on the plan.

Do not shrink any of the tissue until the entire model is assembled. You may want to rig up a model support out of a cardboard box to hold wings and tail in position until tissue is dry and after clear doping 50-50 with thinner. This guarantees a warp-free model.

I built in paper tubes rolled over thin wire for a plugin removable landing gear so you can fly from a hard surface. The tip floats were hollowed out in two halves split down the centerline and glued back together again to keep them light. They were stained with a crimson red dry mark pen to match the red tissue.

The wheel wells were airbrushed on separate pieces of tissue, cut out and doped into place on both sides of the fuselage. When flying the model (hand launched) a paper wheel disc was taped over the wheelwell to simulate the retracted position.

The propeller blades were cut from a cottage cheese container on a 15 degree angle for right and left counter rotating propellers, using the pattern provided on the plan. These blades were super glued into a balsa hub in the slots provided. A lock washer provides the spiral catch. Reverse bend another one for the opposite turning propeller assembly. Glue in position with Super Glue. Build in about 3 degrees down thrust in each thrust button. Vacuform a spinner cap for each.

All the graphic decorations - name, Alaska seal and flag - were photo copied the appropriate size on white tissue, then attached with spray adhesive to the model locations on the plan.

I built a ballast box into the nose of the hull. It turns out that some clay is needed to achieve a CG position at the main wing spar location. Test glides were made with the propellers off. Horizontal stabs were lightly tack-glued to the butt plate for ease of adjustment. Add super glue when satisfied for a more permanent attachment.

The model weighed 24 grams without rubber, 28 grams with rubber motors added.

Powered flights were achieved in calm air using tan rubber 3/32 inch wide, each motor 15 inches long. Fifty turns with a 16 to 1 ratio winder were put in. The flight pattern was a gentle climb straight out and flat wide circles to the left were achieved using slight left rudder trim. No torque problems with opposite turning propellers. To date, I'm very encouraged with the first flights. Now let's up the turns to 70 and see what she will really do. Sure looks pretty in the air at sunset.

Postscript: Since this article was written, changes have been made, based on flight testing at the FAC Nats in Geneseo this year. Power has been increased to 1/8 inch tan rubber, 16 inches long; and props were switched, improving climb out (blades turning inward at the top instead of outward). However, there is still a bit of Dutch roll. More nose weight seemed to cure some of it. I'm guessing, but I think more stab area may be needed, so rudder and stab extensions will be tacked on with further flight testing.

References:
Grumman Aircraft Since 1929; Rene J Francillon, p 99.
Air Classics; May 1974, Vol 10, No 5 pp 56-58."

Update 15/09/2019: Added article, thanks to RFJ.

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Grumman Aleutian Goose (oz1220) by Pres Bruning from Flying Models 1993 - model pic

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