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Dumas Walnut Scale DHC-2 Beaver RC conversion (a build-along-ish log)

Craftydan

Hostage Taker of Quads
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#1
Time to stop procrastinating . . .

So after getting tired of not building anything while my workshop was in disarray (stupid water heater!) I decided a few days back to start a kit I've had siting on my desk since I picked it up in May:

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Great kit, comes with two lasercut sheets, quite a bit of 1/16th stock of various widths, a pack of white tissue and ascetate, a few odds-n-bobs, two sheets of plans (one to build on and one with construction details) an instruction booklet (with a few minor variants). Pretty much just add glue and elbow grease (lightly) and she's supposed to come out a bit like this:

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Pretty little thing. After running a few nights, I noticed the Winter Balsa Build-Along had just started, so into the ring she goes.

A couple of planned changes . . .

First, floats are a nice scale touch, but she's going to be a flying model -- Fixed LG. I've also got the combined guts from a Parkzone Night Vapor and a Champ, so she's getting the RC treatment. A good combo -- servos on the brick, decent power motor and lights to string into the wing and fuse. Finally, I've got to make an access hatch to get to the electronics and battery after everything is covered.

so, on with the build logging . . .

Night 1:

So first night, naturally, I wasn't thinking about it and snapped one nessie-quality pick of the "finished" product:

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Pretty simple so far. Lay out the pieces on the side view of the plans and glue, cutting the sticks to size around the laser-cut pieces. Assemble two sides, then glue in the horizontal spacers between the halves in all the right spots, bending to get the tail together. Glue the two front side-cheeks onto the fuse, then glue on the firewall with a slight down-angle.

Easy-peasy and everything is still open and accessible. That will change, but some decisions have to be made before that . . . particularly how the motor will mount while keeping it accessible, where to mount the brick, and how to get to it for service and battery.

Night 2:

Doesn't seem like much:

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. . . but made a few decisions.

The motor will mount to the front cowl block. a quick check showed the motor can be trimmed a bit to fit inside the keyhole in the firewall, so all I'll have to do is removeably secure the cowl to the firewall and everything fits in nice . . . and the motor pops out with the cowl if I nee to fix something . . . so on the stringers go over the top and sides.

Tomorrow the hatch and cowl . . . in a bit better detail . . .
 

PsyBorg

Wake up! Time to fly!
#2
I take it this is gearing up for indoor season? That looks aweful tiny to be an outdoorsy thing unless perfect conditions are happening.

I used to love building models when I was younger. Now between the eyes goin bad and the nerve damage and shakes I'd spend more time un-gluing my fingers then building with something that small. I had to use granny glasses AND a lighted magnifying glass to do the soldering on my Alien build. My luck I would have to add another looking glass and end up setting the wood on fire from the ceiling light getting magnified so much :p

Will keep an eye on this build to see how you engineer the changes along the way.
 

Joker 53150

Mmmmmmm, balsa.
Mentor
#3
Nice start! Since this was designed for rubber flight hopefully you don't have to fight balance issues like those converting other kits to RC. I'd guess keeping as much weight in the nose as possible would be the safe way to go.
 
#4
I'm really fascinated by these stick and tissue conversions. As a kit I always wished I could control my rubber power planes, now the technology supports it pretty cool.
 

Craftydan

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#5
I take it this is gearing up for indoor season? That looks aweful tiny to be an outdoorsy thing unless perfect conditions are happening.
Not entirely . . . but here in Georgia, we've been know to fly "indoors" in the heat of summer (no, it's not as pleasant as it sounds). Indoors is less of a season and more of a state of mind ;)

At 18", She's a walnut scale model (13-19" wingspan), so she's at the boundary between indoor and outdoor. The freeflight version would have to be trimmed tight on the circles indoors, but outdoors a fair wind could carry her a ways -- she's very comparable in size (and hopefully weight when I'm done) to a parkzone Champ, so I expect the RC conversion to be about the same -- big gym or small field with no wind. Fine for a calm day at dusk.

I used to love building models when I was younger. Now between the eyes goin bad and the nerve damage and shakes I'd spend more time un-gluing my fingers then building with something that small. I had to use granny glasses AND a lighted magnifying glass to do the soldering on my Alien build. My luck I would have to add another looking glass and end up setting the wood on fire from the ceiling light getting magnified so much :p
I am getting awfully close to the building board when making cuts . . . haven't been poked in the eye yet with the back of a T-pin, but gotten close a couple of times ;)



Nice start! Since this was designed for rubber flight hopefully you don't have to fight balance issues like those converting other kits to RC. I'd guess keeping as much weight in the nose as possible would be the safe way to go.
Thanks :) I'm about a week behind on this log -- I just started :p -- but I should be caught up to real time in by either tonight or tomorrow.

Balance is a concern that's easy to forget until many of the options are gone. On the positive side, the Motor/prop DOES weigh more than the rubber propeller and bearing, but yeah, not by as much as I'd care for. Most of the mods happen at or forward of the CG . . . except the tailfeather hinges and linkages. Particularly if I stick to scale, I'm going to have to run some thin music wire to connect the elevator halves and add on a tiny tail wheel -- all nice detail, but that far aft? yuck. While I'm still not building heavy, I'm not going light on the forward mods, and some of the tail structures for the rubber band will get trimmed out. Even still, I expect some ballast will come into play. Beyond that, the best I can hope for at this point is the AUW doesn't get crazy (for the size) high, and the big brushed motor up front makes up for everything.



I'm really fascinated by these stick and tissue conversions. As a kit I always wished I could control my rubber power planes, now the technology supports it pretty cool.
Agreed, and surprisingly approachable. If you can kit-bash and scratch-build, this stuff is more of the same . . . only smaller. That and I can't remember a big swap-meet or such event that some of this radio gear wasn't on someone's table for cheap. While I am concerned with the strength of the materials (every stick of balsa in this kit is light, and the laser-cut sheets is at best medium weight), this kit has been designed to fly well with nothing more than slight adjustments and warps in wings and surfaces. There's no reason even the tiny surfaces she has won't do well in nudging her around the sky . . . and when back to neutral she should gracefully fly on her own. I don't expect her to be aerobatic, but as a 3 channel scale model? If she flies well, she'll be a beauty to watch in the air :)
 

Craftydan

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#6
Night 3:

So for tonight I add on the stringers. Formers are glued at regular intervals to frame, mostly to the bottom (there are two on the top of the "engine compartment" and a set built into the side-cheeks, but those were done the night before).

Pretty typical . . . but I want a hatch.

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If you want a hatch between two formers (which I do), it's easy-peasy to build so long as it's done before you attach the formers. Take the two formers that will become the bulkheads the hatch will ride against, and use some stock/scrap of the same wood to make two more. Now I've got matching sides for bulkhead and hatch :)

To install, mount the bulkhead-side formers to the frame and finish running the stringers up to the edge of the hatch, sand the bulkhead former lightly to clean up any overhanging stringer and glue. Then lay the hatch formers against the bulkhead formers and cut a single piece of stock to span the gap forming a backbone of the new hatch structure. When you dry fit the backbone into the gap (formers pressed against formers, held in place by the backbone) everything should fit snugly. Put a drop of glue between the hatch formers and the backbone on each side (careful to not get any between the hatch and bulkhead formers) and dry. You can then carefully remove the "I" beam hatch a bit so you can add in stringers (hey! the formers have notches ready for stringers ;) ) and any additional structure you might need. I added two more beams right out at the edges.

P_20161130_232700.jpg

once dry, sand the glue joints to clean up and the structure should fit snugly. Hinge and retainers for the hatch will wait until covering time . . .

So on to the landing gear . . . The plans had a conventional fixed gear variant, but it needed a few pieces cut out of stock, and a bit of .035 music wire. Cut out pieces, bend wire to plan, and glue in place . . . Done, done and done :)

P_20161130_232853.jpg

Finally, for the night, the cowling block is made from 6 laminated parts -- two disks for the bearing surface, two rings for the decorative cowling look, and two on the back to key to the firewall. They only have to be centered with each other, but as with any good lamination, it's best to glue each layer cross-grain. Glue and set aside to dry overnight . . .

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. . . and we're done for Night 3. good progress. looking more like a real plane :)

Night 4:

So night 4 starts out where 3 left off . . . pull out the sanding block and shape the cowling into something cowling-ish.

a bit of sanding later and looking at the motor, the bearing hole will need to be reamed out a bit, for the prop-shaft gear and a notch cut for the drive gear and a notch . . . cut/fit/cut/fit . . .

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Trim the sides of the motor mount and add a bracket to mount to the motor, dry-fitting and checking the angle and spacing . . .

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Glue the motor bracket to the cowling, and slip it onto the firewall to check . . . .

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Perfect. The motor will fit loosely in the key slot for now . . . still debating on attachment, whether band and hook or blind nut and bolt, but it needs to resist pulling out, but remove the fastener and out it pops.

Add on a prop . . . Hey, that looks like a fuselage!

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Tomorrow, on to the wings!
 
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Joker 53150

Mmmmmmm, balsa.
Mentor
#8
It will be interesting to see what the final weight is, compared to the weight of the plane the electronics were made for. I've read a few build threads from guys doing this kind of work and some of them get clinical about removing every single gram of excess weight possible.

As I keep telling my dad with the regular park flyers he builds, the plane has got to be built to FLY, not to survive a crash. He likes everything to be solid, but solid = weight. Doing a build like this could be a good exercise for him. I did a Hobby King Red Swan glider kit a few years ago, and then built a second one trying to shave as much weight as possible from it to see if I could get better performance out of it. In the end, the 2nd one was about 20% lighter and it certainly does glide better. That build taught me quite a bit about trying to balance light weight and strength.
 

LitterBug

Troll Spammer
#9
Looking really nice Crafty Dan! I have two Guillow's planes that are 80% done on my winter to-do list. Have a Piper Cherokee 140 and Stearman PT-17. I've been debating making them RC or just shelf/hanging models. From what I've read, they are a bit heavy for RC conversion without major modification (lightening/balance). Thought about using the guts from my Sport Cub S for power and control. It got smashed up pretty bad (IE run into by bigger hungry props) during last year's indoor season and replacement parts are too expensive to justify a rebuild. Cheaper to buy a new plane instead. I have the AS3X programming cables from a different controller. Need to see if the Cub brain will let me make adjustments for different configs.

Cheers!
LitterBug
 
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