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Balsa Build Along 2017/18 - Hobbico 300S, Thinning the Herd

Joker 53150

Mmmmmmm, balsa.
So as mentioned on a previous build thread, I've decided against buying yet another plane to build for the 2nd Balsa Build Along, as my fleet of hoopties and projects has been growing out of control (as explained to me by my wonderful, caring, and understanding wife :) ). This time around I'm taking a different approach and using the Build Along as an excuse to thin the herd a bit and to also try some building techniques I haven't used before.


Two years ago I picked up a pair of Hobbico 300S planes at a swap meet - one was noticeably better than the other, and the seller said he was going to use the trashed one to fix the good one. Seemed like a great idea to me! :p So here's a finished shot I found online, minus the cowl. I think these kits came with covering on the wings and fuselage, but all parts I got were bare balsa.


Aaaaaand here's what I've got to make that a reality. I printed a copy of the manual, which will help quite a bit with the wing saddle design. The canopy is brittle and broken, so I'll either have to make a mold and vacuum form one or find another route. There was no cowl with my junk, um, "parts", but I found a company that makes fiberglass reproductions of it. I've also got both elevators and a rudder, although all three pieces are fairly rough and I may just build replacement pieces.


The white tray is actually the bottom center section of the wing, and the bags hold parts that may or may not have been for this kit. :)


The wings are an interesting part of this collection of stuff. I've got one complete wing (not in this picture) and two additional right wings. No left wings, and there is a slight difference. I could probably make them work if I had to, but since I have a complete wing I'll just use these to test out some ideas I've got for the project before throwing them away. Why not save them? Read on!


This is the better of the two spare wings. Sometime in the past this plane took some pretty heavy damage as the balsa is broken off the foam-core wing!


The ailerons are also all pretty rough, so I'll just cut new ones.


Oh, and the spare fuselage is no better than the wing. It's been broken in half at least once, and has a ton of epoxy inside holding it all together. It's also fuel-soaked. Could it be saved? Sure, but I'm drawing the line on this one!




By comparison, here's the GOOD fuselage! It's never had electronics added, so it should provide a decent platform to build upon.




The tentative plan is to go with either a .60 size 2-stroke glow engine or a .90 size 4-stroke. There is a swap meet at the end of the month that I'll attend to see what I can find. So now the parts all go back on the shelf for the next few weeks until the Build Along officially starts. As tempted as I am to jump in and get working, there are still other jobs that can be done first, and if the weather clears up I may also get some flight time in!

Joker 53150

Mmmmmmm, balsa.
Maybe? Although it's hard and brittle like old epoxy, so I'm assuming that is what it is. Since tomorrow is garbage day I threw that trashed fuselage out, after cutting the tail off to be used for templates. It was kind of satisfying, but hopefully it doesn't count as jumping the gun on the Build Along! :)

Joker 53150

Mmmmmmm, balsa.
Well, I needed the space to work so that's my "official" excuse! :) Earlier this year I picked up a couple nitro planes and am trying to get at least one of them ready to fire up - it's a Great Planes Zero, with a .61 Super Tigre engine. All it really needs before I can fire it up is for the fuel system to be re-done with new lines. Hopefully by Tuesday I'll take delivery on the new nitro lines and a nitro fuel pump. It's a little over-powered, but should be a blast to fly!

Joker 53150

Mmmmmmm, balsa.
Less than 2 weeks till the Build Along starts, and I just did an inventory of what I want to get done before it starts and before winter arrives. No way it'll all get done, but a punch-list is always helpful in making sure I've always got something to do.

  • DONE - Finalize programming on the EVA Bipe, and set up better control throws (maiden was VERY twitchy).
  • Hit a swap meet next Sunday!
  • Sneak new planes from the swap meet into my shop.
  • DONE - Add a little downthrust to the Kadet Senior motor (it climbs too much with power).
  • DONE - Build new motor mount box for Kadet Mk.1, stuff as much weight in as possible.
  • Apologize to my wife repeatedly for my RC addiction after she finds the new planes.
  • Do a maiden flight of my Great Planes Zero with a glow engine. It's tuned and ready!
  • Hit hardware store for nylon bolts for wing mounting on Kadet Senior and Kadet Mk.1.
  • But wife flowers as a peace-offering and promise to stop buying planes (eventually).
  • Build a plane stand to stack some larger planes, and get them out of the garage for winter.
  • Build a storage rack for the big wings on the 1/3 and 1/4 scale planes.
  • Buy bigger house for plane collection, or maybe a smaller house with a bigger workshop.
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Joker 53150

Mmmmmmm, balsa.
Reading the instructions doesn’t count as “starting early”, does it? :rolleyes: I’m just checking it all out to make sure I’ll be able to get all needed parts to finish splicing these planes together, and so far it looks good. I’ll need to scratch build all new tail surfaces, which should be easy enough. Not sure what I’ll do for a canopy yet, but may have to try my hand at vacuum forming. A cowl will be purchased, and hopefully I find a good 60 size glow engine at the swap meet this Sunday.

I’m also kicking ideas around for a finish on this plane, and may have something special figured out. I don’t know if it’s feasible or not yet, but it’s something I’ve wanted to do for a while.

I’m taking a few days off this week, making a 4 day weekend, and hope to get a few projects cleared up. Can’t wait!

Joker 53150

Mmmmmmm, balsa.
I guarantee she will not be happy with me on Sunday afternoon. :) That's one of the big problems with my addiction to giant-scale planes, they're darn near impossible to hide unless I rent a storage locker somewhere.

Joker 53150

Mmmmmmm, balsa.
So far they've all been in the northern half of the state, probably because it's finally getting too cold to fly much and building-season is about to start! The first one I've seen this year was on the EAA grounds in Oshkosh. This next one is also about an hour north of Milwaukee, and there is also one that same day towards the center of the state. The big one for the Milwaukee area is probably in January or February, and then there is another big one a bit west of Chicago. Hopefully there will be another one or two that I don't know about yet. :)

The trick is finding out about them. Sometimes they are advertised on Craigslist, other times on RC Groups, or it seems like most clubs are notified as well so you may ask around at a few different clubs.

Joker 53150

Mmmmmmm, balsa.
Having a cold sucks, but having it when you took time off to enjoy a 4-day weekend sucks more. I wanted to get a lot of stuff done before winter hits, but just wasn't up to it with the cold and windy weather. Instead I spent a little time playing around with the Extra 300S, and even though it's not November 1 yet I did a little preliminary work. :eek: I hacked up the tail section to see what was inside so I could make sure there was enough balsa stock on-hand to rebuild these pieces from scratch. The horizontal surfaces are built-up while the vertical surfaces are simply solid sheet. The plan is to simply re-create the original design with a few simple mods as needed. Details to follow!

Joker 53150

Mmmmmmm, balsa.
Arrgh, sitting here at 3am, up dealing with a cold since midnight and waiting for the NyQuil to kick in, I may as well get some work done. I'm starting on the tail, which needs considerable work. The donor fuselage included all the tail surfaces, but they are all beat up and only good as templates. First task was to see how the original pieces were made so I could make sure there was sufficient balsa stock on-hand to do the work.


A little quality time was spent peeling back some sheeting on the horizontal stab, revealing a built-up structure with 1/16" sheeting. Two hardwood 1/4" x 1/4" pieces are also included to help keep the piece rigid. It's a fairly generic design and should be easy to reproduce.


Graph paper was used to trace the outline, and the drawing was then checked to make sure the sides were uniform. Once done, perimeter pieces were added using my smaller metal sheet and magnets.


The original design was followed pretty closely, although I omitted a spacer near the trailing edge which I assume was installed to make drilling hinge holes easier. I also used the hardwood lengths for durability. Once this dries it can be sheeted, sanded, and drilled for hinges.


And now it's starting to look like something! :) As I've done on most of my balsa projects, I try and use a little "old" balsa in the project. With this plane I've added some old sheet on the bottom of the horizontal stab and an old piece at the bottom edge of the rudder. I estimate these pieces are at least 40 years old, as they were in my dad's possession when I was young.



Joker 53150

Mmmmmmm, balsa.
Something has been confusing me on this plane, and I haven't figured it out yet. From what I can see, Hobbico sold this as an "AWARF", which meant All Wood Almost Ready to Fly. It came covered and ready for the builder to do some actual fabrication work. However, the fuselage I'm working on was never flown (no screw holes were made for the servos, a dead give-away) but it had the covering removed. I found traces of the original covering, plus a slight residue from it. That makes me wonder if it was purchased with the plans of re-covering it, or if the original covering was just so bad it was removed. Strange... :confused:

Vertical surfaces are next, as I jump around between projects on this plane. You can see the original pieces are fairly well trashed. They're made from solid sheet, and done in a way that minimizes waste and makes them fast to manufacture, and I don't like 'em. The way I see it, there are two problems - first, the balsa can flex/warp/curve easily along the grain. Second, I'm not a big fan of that much end-grain being exposed. The entire leading edge of the stab and trailing edge of the rudder is end-grain. It isn't as easy to shape uniformly and for the finish I'm planning it won't look as nice.


To fix what I consider problems I came up with this design. It was more work, but now the leading and trailing edges are all long-grain edges and not ends. The bottom of the rudder is also a fairly old chunk of balsa, and much harder than the rest. I'm not sure yet what I'll do for the tail wheel, but this may be a benefit later on. I won't do too much more with these pieces until the rest of the plane starts to come together, because...


...they may need to be modified like this Extra 300 from Red Bull. I forget what they call it, but the rudder comes out forward and becomes part of the vertical stab. The tentative plan is to make this change, but first I need to do the test-fitting on the plane with the fuselage assembled farther. Right now the rudder appears to be about 1/2" too tall, even though the original was used as a template. I'm probably just missing some material near the tail wheel, but want to make sure before I make any big changes.


Joker 53150

Mmmmmmm, balsa.
I'm lucky enough to have found a set of instructions for building this plane, and the pair of planes I got included plenty of parts to do it. But not ALL parts were included. :( Here is a good example - this pocket is in the top of the wing and is meant to hold the aileron servos. However, all of the pieces that make up the servo tray are missing. Lucky for me, the instructions actually call out the size of each piece! :)


I'm making them all out of 1/16" ply, all drawn to the sizes shown in the instructions. Lucky for me, they all fit! The two pieces to the right line 2 of the 4 sides of the servo pocket, and the piece marked "servo tray" will be further cut to fit standard size servos


Here are all the pieces installed. Per the instructions I coated all exposed foam surfaces with epoxy, then glued in the tray, followed by another coating of epoxy. Another layer will be used to complete the servo tray and give it strength for the mounting screws.


Another piece that wasn't included is used to locate pins in the front of the wing, which fit holes in the fuselage and lock the front of the wing in place. I had to do a bit of guess-work on this one, as there were no details, and only one picture. The part is being epoxied to the LE of the wing. So far I like how the plane is taking shape, although that could just be the cold medicine talking.



Aviation Enthusiast
I believe the rudder design in the picture has a counterbalance so when he is flying knife edge it wont take as much rudder pedal force, but I think there is a trade off with less rudder authority. I could be wrong here, but I believe I heard this on a air racing show.

The Great Planes Extra 300 that I am interested in has the same rudder design.

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Joker 53150

Mmmmmmm, balsa.
The rudder may or may not make much difference for my lack of flying skill, but it's a detail that I think looks pretty good.

That's a nice looking plane, probably MUCH lighter than my fully sheeted version!