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Old Mar 07, 2015, 12:12 AM
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Idea
Royal Marine

Hi guys! This is my first build log over on this site, so please bear with me. For that matter, please don't hesitate to let me know if I'm doing anything wrong.

I spotted the plans for this plane on Outerzone, and since I've always liked flying boats, figured I'd give it a shot. It has been described as the world's most beautiful flying boat, and I can see why.

There is an article from American Aircraft Modeler from May of 1970 by the builder/designer, Yuji Oki describing the work he did developing the plane. I searched all over, and only found one other build, a few years back on RCU, where the fellow built it as an electric flyer, and he said it flew well.

Anyway, I got started a couple of weeks ago, and am about 2/3 done at this point. I followed the plans pretty closely until I got to the wing, which I changed a bit. The design has 3 hardwood spar assemblies, and calls for 3/32 balsa sheeting over the entire wing. I chose to go with a more standard D tube with partial sheeting and cap strips. By the way, to further complicate the build, all of the surfaces are tapered, both in chord and in thickness.

Anyway, here's a few photos.
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Old Mar 07, 2015, 06:10 AM
boat butcher
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Whittier CA.
Joined Oct 2009
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Lookin' good .

Mark
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Old Mar 07, 2015, 12:08 PM
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There was a good deal of confusion involved with the plans for this plane. It was listed as having a 96" wingspan, to be powered by twin .40 glow engines. That seemed a bit off, so when I got the plans printed out, I measured the wingspan at 68", a lot more reasonable for twin .40s. The other build that I mentioned came out at 86", just to further muddy the waters.

Through the changes I made to the wing, including changing the rib spacing, mine will come out at 71". I have a pair of Thunder Tiger GP .42s set aside for this project, and they will be running diesel conversion heads.
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Old Mar 07, 2015, 12:21 PM
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The fuselage is standard formers and stringers. The plans call for 1/8" balsa over everything, followed by fiberglass cloth. I opted to go with 1/8" on the hull only, and 1/16" everywhere else. The 1/16" would be easier to form tight curves. I'll use 2 oz. cloth on the hull, and 1/2 oz. cloth elsewhere. This should come out a bit lighter. I'll paint the fuselage with Nelson Hobby paint, which will be a first for me.

Once the fuselage was built up and the bottom covered, I gave the inside a couple of coats of thinned epoxy to keep the wood dry, then put in foam pieces to add some buoyancy.

The wing pylon will be firmly attached to the wing, then sit down in the well in the fuselage, and be held down by a couple of 1/4 x 20 nylon screws.
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Old Mar 07, 2015, 12:28 PM
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Now onto the wing construction. After cutting out all the ribs, I drilled them all for my wing jig, then glued it all up. I chose to use 1/4" Sitka Spruce for the spar, located at the high point of the ribs, instead of the multiple 3/16 spars called out on the plan.
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Old Mar 07, 2015, 12:36 PM
# Scale is a way of life
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United States, OH, Avon Lake
Joined Apr 2010
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That foam will actually reduce your buoyancy,, it's just dead weight,, buoyancy is a result of water displacement and weight,, it will only help if the hull fills full of water

otherwise great build
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Old Mar 07, 2015, 12:42 PM
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Onto the engine nacelles. Now I figured out the downside to my idea of changing the spars around. My way left no room for the fuel tanks without moving the engines about 2" farther forward, which I was unwilling to do. I hit upon the idea to cut the top spar, and form an arch to tie it back together. The tanks can fit under the arch, and the arch will be the former for the nacelle itself. It seems to be pretty solid.

The plans call for the engines to be mounted to 3/8" hardwood covered by 1/8" sheet aluminum. I chose to go with 1/4" ply covered with 1/8" light ply extending aft behind the spar. The idea was to mount the throttle servos in the light ply. The problem I ran into was that the ribs are spaced too close together to allow a standard aileron servo to fit, at least without some of it hanging out in the spray. The solution was to mount the aileron in the nacelle, next to the throttle servo, then run a rod out to the aileron, and use a bellcrank mounted in one of the bays.
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Old Mar 07, 2015, 12:43 PM
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Quote:
Originally Posted by the goon View Post
Lookin' good .

Mark
Thanks Mark!
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Old Mar 07, 2015, 12:48 PM
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Quote:
Originally Posted by scale_only View Post
That foam will actually reduce your buoyancy,, it's just dead weight,, buoyancy is a result of water displacement and weight,, it will only help if the hull fills full of water

otherwise great build
I never thought of it that way. Its all glued in now, so I'm stuck with it. At least its only a few grams in weight, and centered around the CG. Thanks for the tip!
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Old Mar 07, 2015, 12:56 PM
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The plans call for the pontoons to built with a 1/8" balsa spine, 1/8" balsa formers, and 3/16" square balsa stringers. I went with 1/8" lite ply for the spine, 1/8" balsa formers, and 1/8" square stringers. The bottoms were then covered with 1/8" balsa sheet, and the tops were covered in 1/16" balsa sheet. These too will be covered in 1/2 oz. cloth, then painted.

The designer called out 1/8" aluminum sheet for the pontoon's pylons, but I went with 1/8" birch ply instead. He mentions attaching them with rubber bands, but this method does not show anywhere on the plans, and I couldn't figure out what he meant. I intend to use either heavy duty Velcro, or 3M Command attachment strips. Either way should allow enough give in case of a pontoon strike.
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Old Mar 07, 2015, 01:02 PM
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The tail surfaces are a bit of a challenge, in that they are tapered in every direction, then slid over plywood spars that are actually extensions of a couple of the rear formers. This will all get covered with 1/2 oz fiberglass cloth to add strength to the joint and smooth it all out.

Robart hinge points are going to be used, and all the holes have been drilled for them. I also found some NOS Robart hinge/horn combo pieces that I'll use on the split elevators and the rudder.
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Old Mar 07, 2015, 04:00 PM
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United States, NJ, Frenchtown
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I also pack boats & seaplanes full of foam. Less water can come in to ruin electronics & batteries.
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Old Mar 08, 2015, 01:40 PM
An itch?. Scratch build.
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South Wales U.K.
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Twin .40's ?, shame, electric twins are a lot safer from one engine out, (and quieter)

Nice build.
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Old Mar 08, 2015, 01:44 PM
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Motor itself is quieter. But the prop noise is the same loudness. Some props are louder than a muffled motor. Apc E are very quiet. Noise means wasted prop power.
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Old Mar 08, 2015, 06:08 PM
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Diesels normally run until they're out of fuel since they don't have a glow plug. They tend to run a good deal quieter than glow, and turn a bigger prop at slightly slower speed too. I've built in 3 degrees of out thrust on both engines just in case of engine loss. I'm not terribly worried.

In the construction article, the designer mentions building the plane with a single .60. I thought about building another wing in order to do that, and may yet try that later.
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