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Rudder/Elevator Control Surface

I finally got around to cutting out the parts to assemble one of the rudder/elevator control surfaces today. The whole thing is built from 1/32″ balsa sheet material and some super glue.

Each rudder/elevator control surface is 8″ x 2″ and 1/2″ thick at the base, with 7 ribs.

The finished piece weighs in at around ~2 grams, and it feels as light as a feather. It’s so light that I now have no doubt that the tiny magnetic actuator will have any trouble moving it at all.

This turned out to be quite a challenge. I’m going to need more practice to get up to the level of quality I want for the finished airship. Although fairly rigid and strong once assembled, the balsa material is pretty fragile while working with it.

It would be great if I could find someone or someplace that could laser cut the material from my drawings. Just out of curiosity I think I will look around and see if anyone does work like this on a very small scale for a reasonable price. If not, I will just suck it up and get better at cutting out and assembling the parts myself! We’ll see..

U.S.S. Macon designed and built by Jack Clemens

I just found out about this incredible 1/40th scale R/C flying model of the U.S.S. Macon on the Airships.net blog. The airship, designed and built by Jack Clemens, is 20′ long and 3′ in diameter. It’s a BIG model airship and only fit in his two car garage diagonally. And it flies!

This really gives me a little more motivation to stop procrastinating and find more time to work on my own model airship.

Links:

Giant Radio Controlled Model of U.S.S. Macon
» http://www.airships.net/blog/giant-radio-controlled-model-uss-macon

FLY RC Snapshot: Recreating the USS Macon
» http://www.flyrc.com/aug11snapshot

You Built What?! A Colossal Flying Reproduction of a 1935 Airship
» http://www.popsci.com/diy/article/2011-04/you-built-what-retired-engineer-crafts-colossal-gliding-model-1935-airship

Airship with Engines (Rear View)

So after designing the engine cars it’s time time to mount them on the airfship. So I copied and pasted my engine car model into the main airship Sketchup file and spent some time mounting them to the airframe.

I am fairly certain that I will use either 1/16″ balsa or spruce sticks to mount the engine cars to the airframe, but I have also been thinking about using extruded square carbon tubes, or maybe even some small diameter carbon rod, for the extra strength. Some good 2-part epoxy would probably bond those together, and to the airframe, pretty well. I’ll have to think about it though, and maybe I will try both on the test section once I get it built.

Mounted Airship Engines (Close Up)

The engines will mount to the 13th and 15th rings near the tail so that the center of each propeller is 1 1/4″ from the ring it is attached to at a 45° angle. Since the propellers are 2 1/2″ in diameter this allows them around 1 inch of clearance from the airship.

Previously I had been thinking about designing a way to gimbal the motors to allow for some thrust vectoring to assist with the control system. For now I have opted to go for the simpler option, but may revisit the gimbal mount idea later on in the project. Stay tuned..

Engine Car (Front)

I know I’m skipping around a bit here, but all of this design work has to be done eventually. So why not now? This past week or two I have designed the engine cars that will hang off of the airframe and (hopefully) propel the airship through the air.

The diagrams show an opening of 1/4″ for the motor, but it will actually be 7mm (just slightly larger than 1/4″), the diameter of the tiny motors I purchased from MicroFlight.com.

To accomplish the bottom curve shown in the design I will probably soak the piece of balsa sheet in water so that it will bend without breaking. I will probably then shape it around a 1/2″ diameter piece of wooden dowel, then let it dry before adding it to the engine car. The top curve probably won’t require any soaking to get the right shape.

Engine Car (Rear)

The rear of each engine car will have a slight opening at the bottom rear to allow any heat from operating the motor to exit.

Each engine car will built entirely from 1/16″ (and possibly 1/32″) thick balsa sheet material.

I may also paint the engine cars silver to give a more scale appearance, although this will not be a scale model of any airship previously built. All of the design work is being engineered to work for this aircraft, without the limitations of imitating a craft 100x it’s size.

Engine Car with 2.5" Diameter Propeller

The image to the right gives an idea of the actual scale of the engine car. The propeller is 2.5″ in diameter.

1/16″ square mount points for the struts are shown in this image.

I plan to test the motors while in the engine cars sometime soon to see if they get hot. I have a temperature gun I will use to determine the temperature they reach while running at full throttle for 5 minutes. And of course I will post the results of those tests here.

More Rigid Tail Ring

So after taking a few months off to work on a couple of other projects, I am now trying to get the model airship project going again.

I decided to ease back into it  with redesigning the tail and nose rings to make them a bit more rigid. My fear was that while in flight the tail section might crack or break with the added stress of executing a turn if it were built solely out of 1/16″ balsa sticks. (This is again assuming the tiny motors will be enough to get her going and enough air flowing over the control surfaces)

So I have decided that the 1st (nose) and 17th (tail) rings should be built from 1/16″ (maybe 1/32″ if it will work) sheet balsa, or maybe even light plywood. Cut out just enough in the middle to accommodate the diameter of the gas bag.

More Rigid Nose Ring

There’s no getting around the fact that the airship will be a little fragile. I just want to minimize potential damage where I can.

And now it’s getting really close to time to actually start building this thing! As noted before I will start by building a complete tail fin, which will allow me to complete my weight and lift estimates.

It has also occurred to me that the bracing thread will be much more critical for rigidity than I had previously thought..

Hopefully I will be able to finally post some build photos (and maybe some video too) in the near future. Stay tuned!

Dallas Rangemaster (Germanium NPN)

It occurred to me that it had been a couple of months since I had posted an update on the airship project here. So I just wanted to let everyone know that the project is still alive, I just got sucked into another couple of projects. Recently I have been building some guitar effects pedals. To see photos of that stuff click the photo to the right.

I still have quite a pile of various sizes of balsa wood sticks, other materials, and tiny R/C parts waiting for me in the living room! Work will start again very soon, and I should hopefully have another update within the coming weeks. Thanks for your patience, and stay tuned!

Tail and Control Surface Frames

Now that I have finished calculating the lifting capacity of the whole airship I also wanted to finish calculating the weight of the entire airship frame.

So I still need to calculate the frame weight of the nose and tail sections. I decided to start with the tail section, since it’s the most complicated. To start I redesigned the tail fin sections since I didn’t like the idea of framing them up with the 1/8″ and 1/16″ balsa sticks the rest of the airframe uses, they would just be too thin and not very aerodynamic (assuming the tiny motors get her moving fast enough for aerodynamics to even matter).

Tail and Control Surface Frames

So I have now finished redesigning the tail fins, they’re 1/2″ thick in the middle. They will be built entirely from 1/32″ balsa sheet material. The 2″ long control surfaces will be so light that I am starting to think the tiny 0.4g 5.1mm actuator might actually do the job of turning them. I will probably test with both though.

Since there are quite a few curved cuts it would be difficult to figure out what the tail fins will weigh in balsa wood. So the plan is to build a tail fin for practice, then weight it whole. This way I will have a pretty accurate idea of what the 4 fins will add to the tail weight, glue joints and all. So the next step is to build a tail fin, weight it, then calculate the weight of the rest of the tail frame..

7mm 2.9 gram Motor and Prop

A couple of small motors and propellers I recently ordered from MicroFlight.com showed up in the mail today!

I ordered two of the small 7mm 1.7Ω 2.9 gram Plantraco electric motors, they were $4.29 each, and two small 65mm (about 2½ inches) propellers, which were $3.25 each.

The plan is to run three of these small motors on the airship, and the radio kit I plan to buy already comes with one. Now that I have a couple to work with I can see how they look next to the test frame I’ve been messing with lately. So far I think they are the perfect size, I just hope the ~11 grams of thrust each one puts out will be enough to get the big ship moving.