Scale build off: Progressive Aerodyne Searey

[jayz 84]

Such a great looking build. For the over all size and weight of your build so far. You could definitely get away with a UMX/minis power setup keeping it light with stable flight characteristics. But you also have to think about it. Do you really wanna redo the wing to save around 6-7grams?

 

[Tench745]

Point taken. I may end up changing the aileron actuation at some point just due to stiffness/stickiness in the linkages, but I'll try it as is for now.

 

[Tench745]

A little bit of progress today. Balsa was planed and sanded into an airfoil shape for the wing struts,

additional formers were removed from the fuselage and the fuse and floats got a first coat of primer.


I've been cleaning up and organizing my work table lately, which means a number of the other projects which have been occupying its surface have been progressing as well. First off, a rack was built for my most often used tools.

I've also had some dress-up items for the Jenny simmering on the back burner for a while which are just about done now:
Dummy engine

Spoked wheels.
I'm not happy with the size of spider-wire I used for the spokes. The next will be done with black thread to see if I like that better.


And last but not least, I have been re-designing my Cafe Air racer once more to be more accurate to the original drawing. As such, I'm building the exposed engine as an experiment in paperless DTFB construction. So far I'm liking it.

 

[Tench745]

I got a little work done on this largely stalled project. The Pylon is mounted, and the wings have been modified to have internal servos for the ailerons instead of the cable I initially had. This way is actually a little lighter and much easier to build.

 

[Userofmuchtape&glue]

That is one beast of a motor!

 

[Tench745]

I've been feeling the need to balsa for a while now and old projects have been staring at me from their shelves. I cleaned, so you can actually see some of them now.
Any-hoo... almost three years later it might finally be time to close up the covering on the Searey wing. I figured while I was at it I would delete the flaps and save some weight. The hinges were cut out and some new trailing edges were built up. The new trailing edges are notched to take new thinner ribs. This should save a little (minimal) weight and be stronger than the old end-grain only connection. I also switched out for a shorter, lighter gauge y-harness on the ailerons, again, to save a bit of weight.
The wings then got their new covering patches and were again epoxied onto the center section.

While I was thinking about it I started drawing the wing and tail surfaces in CAD since nearly all my original plans are all hand drafted on tracing paper.


Coming back to this project after so long I think I overbuilt the wing panels and fuselage and under-engineered everything else.
The wing ribs could easily have been 1/16" sheet instead of 3/32", all the joints could have been notched for added strength, and the wing probably should have been built as a one-piece wing. I'm also going to look into the smaller quad motors to save a bit more weight, provided one can provide the power I need for the prop I want.

I imagine I'll modify the drawings to reflect these changes in time.

 

[Tench745]

Hey, speaking of modifying drawings, has anyone here tried to produce commercial quality balsa plans for a model before? It's freakin' hard.
Over the course of this quarantine period I went through the trouble of digitizing the paper plans I drew up when I started this SeaRey project.
But, being me, I couldn't just leave it at that so I started turning the outlines into a set of plans with sections and grain lines and everything. Here is what I have so far. Some things like the way the keel and spine interface with the formers have been modified to make assembly easier in the future.

I've also managed to overcome one of my biggest puzzles in building this model. I finally figured out how to assemble the struts. Two shaped balsa struts come together at the fuselage and are notched for a piece of 1/16" ply which connects the base of the struts and then slots into the side of the fuselage. The outboard ends are wraped with thread and epoxied to a piece of aluminum tubing. A piece of wire will run through the aluminum tubing between the strut fittings on the wing to hold the outboard end.

Servos for rudder and elevator were installed in the fuselage and pushrods were run for them. The pushrods I have aren't quite long enough to reach the control surfaces and I lost the control horns I had bought for them, so I'll have to wait on hooking all that up. That's what I get for waiting five years to start in on this again.

 

[Tench745]

Poked a this a little more today. The hull got a coat of gloss white and the struts were painted silver. I ran out to the hobby shop and picked up some new music wire for pushrods and some new control horns.

The last of the hinges were superglued into the control surfaces. Unfortunately, the glue worked into the joint and stiffened the hinge action significantly, but not so much that the servos can't move them. Pushrods were bent up for the ailerons as well as the rudder and elevator. Once the pushrods were made the new control horns could be glued in place.

Finally, I glued a bit of Velcro to the center spine to hold the receiver.

All this was made more difficult by the orange DSMX module I need to bind a DSMX receiver to my Taranis. I don't have a servo tester, so to center my servos I had to use the radio, and it's always a fight to get the module to bind properly. I have a new multi-protocol module coming which will hopefully make this easier in the future.

There are just a couple things left to do to finish this one. I'll need to form some sheet plastic into a canopy, add some cf rods to hold the wing struts in place, and add some thread to reinforce the tail. The last thing to do is balance it out with a battery. Current weight with a battery is 12.6oz

 

[Tench745]

Did a little work on this last weekend. I cut away the formers in the forward hull to make space for a battery. Even with the battery all the way forward, I was flirting with tail heavy. I don't want to add any balast if I don't have to, so I started looking at places to save weight.

The most obvious was the motor. The turnigy 2822 I have weighs in at 60grams. I found a quad motor of the same KV and shaft size which weighs only 27grams. Unfortunately, it is also shorter, so I will have to pad out the motor mount enough for the prop to clear the wing. This will move the motor aft a little and give up the advantage of some of the weight loss, but I figured it was worth a shot and ordered the new motor.
The motor and a little bit of carbon fiber rod should be in this week to finish things off.

In the meantime, I made up a windshield and secured it with some canopy glue and aluminum tape.

I also did a float test; she sits right on her lines.

 

[Tench745]

FedEx surprised me on Monday and delivered my motor and carbon two days early. So, last night I made up a new motor mount for the lighter motor, stuck the carbon fiber rod in the wing strut mounts, and gave her a little balance test. It was still right at the edge of tail heavy, so today I moved the RX forward as much as I could without lengthening wires and now it seems to balance just right.


Current flying weight with the new motor and motor mount: 11.6oz. Between the motor, lighter motor mount, and balsa removed for the battery, I managed to cut a whole ounce of weight off. Wing loading is sitting at right about 10.8oz/sqft for a cubing wing loading of 10.4. That's a little heavier than I would have liked but well within the parameters set at the beginning.
Estimated stall should be around 14.3mph at approximately 13° angle of attack.

I tested current draw with the 6x4 3-blade on a storage-charged 2s battery; 10.9 amps. That should give me about 7 minutes of flight time at full throttle. It feels like this one could fly on about half throttle, so I should be able to get 10+ minute flights with no trouble.


Next step is some taxi testing and then a maiden.

Oh, I also got the multi-protocol module for my TX and now I don't have to fight so hard to bind to Spektrum.

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[Tench745]

I posted this elsewhere but never updated this thread. Here it is, the completed SeaRey.

The park I fly from had some pretty big puddles this spring so I was able to do some taxi testing on water with my little Sea Rey.
It has a tendency to hop as it picks up speed and starts to plane.
I decided to go for a high-speed taxi for my last test run. This was probably a mistake. The plane hopped a little too hard, pitched nose down, and "pigrooted" as we call it in sailing. The nose buried itself in the water and drove the plane far enough under to stick in the silty mud at the bottom of the puddle while the fuselage filled with water.
Minimal damage, it cracked the wing struts on the port side. I probably won't be flying it from water again soon, maybe ever, we'll see. I might have to tweak the angle of the wingtip floats to help its behavior on the water.

I bet if it was bigger it would behave more predictably. If I had the storage space I'd go 150% or 200% size.

 

[cyclone3350]

I know that planking was a little time consuming, but in the end, it looks like it was worth it. Nice job!