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Mar 24, 2009, 09:39 AM
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Build Log

My First "real" Rc Airship


Hello, LTA fans!

Here is some informations about my first "real" rc airship, built as a 1:18 scale model (2,8 x 0,95 m).

All started 2 years ago, after a flight with the Zeppelin NT in Friedrichshafen. To extend the magic of this flight, I built 2 little rc blimps named JOMOD 1 and JOMOD 2 from modified toys. The toys original enveloppes were used, but the gondolas were modified or rebuilt with my homemade vacuumformer and a crew was added.
But it wasn't enough, so I decided to build a bigger one, looking like a real airship and able to take a little camera. My first 2 blimps showed old airships with gray gondolas, but this one shows a modern one. The gondola shape is inspired by the Russian AU-30 airship, some details by the Zeppelin NT (propellers and dashboard), and others are from my own.
To calculate the overall shape and dimensions, I used the "airship design4.xls" file designed by a member of the "airship regatta" yahoo group. To calculate a new enveloppe shape I added points generated by the "airshipworldprofilegenerator-05" software from airshipworld.
Some parts were vacuumformed in a clear thin plastic material, but I didn't try to optimize the weight, focused on the "scale" look. So there is also a working landing gear and navigation/flashing/landing lights.
The 2 motors are scrapped from cd/dvdrom players, it's the brushed motors used for the tray ejection, these motors use only a little current intensity and are light (20 g), so small light lipo batteries. I use the vectoring thrust system with only 1 servo, 2 gears and a rod, the motors can tilt about 270. The props are small (AirAce 3 blades props), always for the scale look.
I had a lot of problems to build the enveloppe with balloon foil material, so I built it with polyurethane just 1 week before the first flight (found it at the last moment in MisterZepp's website http://www.mediazepp.com/). Without Dominique help, my enveloppe wouldn't have been ready in time. It is very easy to work with PU, but more heavy than balloon foil material, so a bigger length/diameter than the intended one to have enough lift. The enveloppe is now about 1,3 m3.

With only 2 motors, it's difficult to turn (only 1 motor running), and these little props not optimized (toy props) don't fix that. The flights in a gymnasium with temperature variations and permanent airflow were stressful, especially with a lot of people below! For my next project, I will add a third motor in the stern. MisterZepp, happy with the result of my "JOMOD 3", made for me a NT shape enveloppe as you can see here http://www.youtube.com/watch?v=eSPDgEMeam0&fmt=18
Below are some details and pics about the building process.

Hoping that you will like it, greetings from France.
Denis
Last edited by Bowman813; Mar 25, 2009 at 06:58 AM.
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Mar 24, 2009, 09:51 AM
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Gondola


The master is made of several MDF sheets, cut then sanded. After a primer coat and some scribing, it's ready for the vacuumforming process. The gondola shape prevents to vacuumform the all part into one operation, especially with a homemade vacuumformer without vacuum pump! So it's done in 2 operations.
2 bronze bearings are used for the carbon rod rotation. The functioning landing gear is made with an old rc car modified damper, the 2 tires are shaped with a small lathe.
The crew is made of paper characters, same method for the dashboard.
Mar 24, 2009, 10:13 AM
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Motors And Electronics


The 2 motors are held in place with a cut bracket (?) from an old computer. The hoods are vacuumformed, I had to add tape to strengthen these parts because it tends to deform with paint. 2 prop cones are vacuumformed then airbrushed with ALCLAD paint to have a chrome finish.
The electronics used: a BLUE ARROW 6 channels micro receiver, 2 TEAM ORION AVIONICS PILOT 7 ESC, a vtail mixer (I use a cheap ESKY transmetter with no programming functions), a lipo saver, a LAZERTOYS light system and a GRAUPNER C261 servo.
Mar 24, 2009, 10:24 AM
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Enveloppe


6 gores of Pu are weld with an iron set to 150 C (302 F), without forgetting wax paper. The seams are cut to 10 mm, then all the enveloppe is returned like a sock so that the protubering seams are inside. Leaks are detected by soapy water, some patchs are glued with polyurethane glue to fix that.
3 fins are held in place with plastic "U". I didn't want to attach gondola with velcro tape, so I used the Guga method as said in another thread. The inflation valve is also made in Guga with the syringe method. THANKS GUGA
Last edited by Bowman813; Apr 06, 2009 at 06:50 AM.
Mar 24, 2009, 05:36 PM
Marcus Franco
Guga's Avatar
Very nice Airship Bowman...
And nice workmanship...
Welcome to the world of RC Blimps...
Marcus
Mar 25, 2009, 06:56 AM
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Thanks Marcus, it's a very fascinating world.
Some new pics with details on motors and landing gear.
Mar 25, 2009, 08:00 AM
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That's really neat Bowman, I enjoy all things scale, and your airship is no exception. Fine job!
Mar 25, 2009, 09:20 AM
Potential Future Has-Been
Great job on the gondola. The vaccu-forming stuff is very cool!
Apr 03, 2009, 11:47 AM
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Airboatflyingshp's Avatar
Very impressive workmanship.
Apr 03, 2009, 12:20 PM
Mostly harmless
Very cool work on the gondola!

BTW, how did you manage to join the gores so cleanly? what type of seams did you use? I might be interested in buying a custom made envelope (my owns are comely but wrinkly due to material and primitive tools)
Last edited by Kernwrech; Apr 03, 2009 at 12:56 PM.
Apr 03, 2009, 01:31 PM
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Quote:
Originally Posted by Kernwrech
BTW, how did you manage to join the gores so cleanly? what type of seams did you use? I might be interested in buying a custom made envelope (my owns are comely but wrinkly due to material and primitive tools)
Hi Kernwrech

With a very simple way: 2 gores are held with sticky tape, wax paper is applied above then iron with the iron set to 150 C. A 10 mm width MDF stripe is used to mark the seam border. Once done, another gore is taped on the top gore already weld, and do on... After all gores are weld, I cut the seams borders with scissors. After leaks tests and re-ironing if necessary, all the enveloppe is returned so the seams are inside.
You can do that easily, the only problem is to find PU.
I saw your work in this forum and Airshipmodeler, great, but your material is much lighter than the PU I used. Mine is 125 g/m because my PU is 0,1 mm (4 mil) thick. So I had to over-inflate the enveloppe to have enough lift.

Hoping that it helps.
Denis
Apr 07, 2009, 03:52 AM
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That's what I did to the last seam of the HB-8's nylon envelope... The only problem with laminated nylon is the fact that it only seals dull-to-dull, not dull-to-shiny or shiny-to-shiny. Is there a nylon material that would seal the both ways? Or is there PU light enough for such a small airship as mine (talking about weights less than 20 grams per square meter)???

How did you seal the end plugs without wrinkling (sealing the material under the patch to itself)?
Apr 07, 2009, 09:10 AM
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Quote:
Originally Posted by Kernwrech
That's what I did to the last seam of the HB-8's nylon envelope... The only problem with laminated nylon is the fact that it only seals dull-to-dull, not dull-to-shiny or shiny-to-shiny. Is there a nylon material that would seal the both ways? Or is there PU light enough for such a small airship as mine (talking about weights less than 20 grams per square meter)???

How did you seal the end plugs without wrinkling (sealing the material under the patch to itself)?
Why don't you try to do the same thing with laminated nylon, welding dull-to-dull side for all gores then returning all the enveloppe? I tried that sometimes ago but failed, see my other post https://www.rcgroups.com/forums/showthread.php?t=932915 (hoping to re-test it later, if it works it would be a good technique to look like enveloppes of old airships).
There is thinner PU, but I don't know the weight. I think it would be anyway too heavy.

No problems for the front plug, the 6 seams were overlapping a little. Just a little leak, with the glued patch, no more leak. There isn't rear plug, it's a hole where the little syringe/valve is set with rubber band.
Apr 07, 2009, 02:28 PM
Mostly harmless
It would be interesting to know the tensile strength of the PU film you are using. Might it be used on larger blimps?

I had my problems with the laminated nylon, but the first nylon envelope (with lap joints and silicone glued end caps) turned out to be just fine. However, being more than a year old now it starts to get leaky. Perhaps I should inspect it for holes soon...

Does your envelope have any sort of active pressure control? I was thinking of installing another nylon bag inside the envelope to be hooked to a magician's balloon inside the keel framework. This would keep the envelope under slight overpressure regardless of small changes in temperature and leak.


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