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Feb 10, 2018, 03:47 PM
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Build Log

Easy to build indoor airship


Hello LTA fans!

Here is my indoor airship, based on the open source Silent Runner model from Windreiter team http://silent-runner.net
(3 min 41 sec)

Specs:
2,30 x 0,64 m (92 x 25.6"), about 0,5 m3
Turnigy 2211 2300 kV motor
Hobbyking XC-10A reverse ESC
Hobbyking 3 blade 5x3 prop
Turnigy nano-tech 2S 25C 950 mAh
Payload after fitting battery 56 g, more on that later...

After a big 1:7 scale WW1 observation balloon https://www.rcgroups.com/forums/show...vation-balloon, I wanted to build a small indoor airship able to carry a light camera and more maneuverable than my first one, a long time ago... https://www.rcgroups.com/forums/show...eal-Rc-Airship
I found the Silent Runner, designed by our German friends, simple to build and with good maneuverability.
After a failed first try with old balloon foil material (too old?), I built the envelope with 70 microns Polyethylene (PE) painter tarp. I also made my own design for motor gondola and fins supports.

PE film being fragile, I slightly under inflated the envelope to avoid problems in case of wall bumps. So the payload has been reduced and I taped a Runcam HD on wires under the envelope instead of the Gopro clone previously planned...

She's a wonder to see in flight, you can fly very slowly or with a good speed, I even flew a few inches above the floor without any problem.
So I can say MANY THANKS Windreiter team, you did a good job!

Denis

EDIT: just published my alternative 3D printed parts on https://www.thingiverse.com/thing:2819524
Last edited by Bowman813; Mar 08, 2018 at 04:14 PM. Reason: modification of diameter (0,64 m instead of 1,64 m !) + 3D printed parts link added
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Feb 10, 2018, 03:53 PM
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Envelope


First I tested Helium retention with several PE tarp thicknesses. The 70 microns one had the better retention with a suitable weight to build an envelope not too large.
As always for calculations, I used the spreadsheet developed by a member of Airship Regatta Yahoo group.

The disadvantages of PE film are a less good He retention compared to PU film, and fragility. But it's very cheap and you can weld and cut in the same pass.

I used a mix of techniques from my previous models, with metal sheet on the table to improve heat transfer and wax paper to prevent PE film from sticking to the clothing iron. So from bottom to top:
- table
- metal sheet
- wax paper layer
- two PE film layers
- wax paper layer
- paper gore shape, easy to follow with clothing iron
The iron is run along paper template with an angle of about 45°. I had to do it in 2 times because my table was not large enough.
Once done it was easy to take off the outside PE film, the seam is very thin and not a single leak after air inflation
Feb 10, 2018, 03:57 PM
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Fins


Based on the original Silent Runner fins shape, cut out from 3 mm depron, with homemade 3D printed fins supports.
I wanted to design these parts in two halves, so that fins can slip between. The halves are glued with a soldering iron tip, it's enough to melt PLA.
The front tip of each fin is velcroed to the envelope.
Feb 10, 2018, 04:01 PM
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Motor gondola


As for fins supports I designed my own 3D printed gondola, wanting to avoid the three front carbon rods from the original Silent Runner design.
So it's two rings with carbon rods between for strength, and two longer carbon rods taped on envelope. Small lengths of heat shrink tubes protect the rods tips and tape is applied on envelope where rods tips are. If gondola strikes floor during a bad landing, the fragile envelope is not punctured. It works, trust me!
Feb 10, 2018, 04:03 PM
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Electronics


I used a small reverse car ESC, allowing reverse flight.
The two tail servos are plugged to rx with a four wires extension as explained on Silent Runner website, with + and - shared for the two servos, and two signal wires, one by servo.
Feb 11, 2018, 09:08 AM
Melbourne, Australia
Bravo! Nice work :-)

Did you happen to weigh your 70 micron painters tarp? It would be interesting to know what the gsm weight was (or alternatively, the weight of your envelope?)

And great to see more Silent Runners being built :-)

(P.S. I think at the beginning you mean to say "2,30 x 0,64" m, rather than "2,30 x 1,64 m" ?
Feb 11, 2018, 11:24 AM
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Thanks! It was a pleasure to build and fly.
The weight is 62 g/mē. And thanks for the diameter error, it's now corrected

Denis
Last edited by Bowman813; Feb 12, 2018 at 12:54 PM.
Feb 11, 2018, 07:22 PM
Melbourne, Australia
So I have an unhealthy interest in fabric weights... :-)

The aluminised film I use is around 25-29gsm - I find it horrible stuff to work with, but it is cheap and light. I'd guess your airship has around 4m**2 of fabric, so the envelope weight would be around ~250g? If it was made of 25gsm foil it would be around 100g, giving an extra 150g of payload?

Which said, it looks like the PE film worked really well, and it looks a lot more robust than the Al film version. Do you happen to know how quickly your helium leaks? On an equivalent sized airship I tend to find I lose about a gram / 3 minutes or so, but that may be bad seams - a lot seems to depend on whether it's pressurised to a tight surface or not as well.

I love the printed parts by the way - very neat work :-)

- Chris
Feb 12, 2018, 12:54 PM
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I know what you mean about this "horrible stuff".
I have some old rolls from balloonkits.com (seems to not exists anymore), my first seams for envelopes with this material were a success in 2009, but last year the foil seemed to be more fragile than 10 years ago and I didn't manage to build an envelope for the Silent Runner... So I did it the cheap way this year with PE, even if heavier (my envelope is 3,8 mē).

PE is not robust, it was ok when under-inflated, but at the end of the indoor meeting I slightly over-inflated to keep Helium a longer time because I had to bring back the He bottle to store... A friend wanted to maintain the envelope and his thumb punctured it
So I don't know the leakage ratio, in 2004 a French guy said that it's 0,4 m3 hyperblimp 30 microns PE envelope was loosing about 0,01 to 0,015 m3 every days.
Now time to use another material

My 3D printed parts are an alternative to the original Silent Runner ones, I must optimize and clean stl files before uploading on Thingiverse.
Denis
Last edited by Bowman813; Feb 13, 2018 at 12:42 PM.
Feb 13, 2018, 03:35 AM
Melbourne, Australia
Hmm... I picked up some 50gsm aluminised material from a chinese supplier a year ago - it was too heavy for me, but it was a *lot* more robust. I had to pay a bit extra for them to do a short sample for me (they usually ship in 500kg rolls apparently!) but they were pretty happy to do it - I think it was about $150 for 100 m**2?

However the Silent Runner folks seem to have some good material - not sure what it is or where to get it, but it looks great:
sr7 destruction tests (1 min 44 sec)
Feb 19, 2018, 03:20 AM
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The red foil is a PE/Nylon composite and roughly 45g / mē.
This is a little heavier than the metalised Al/Nylon/PE Material we use normally (35 g/mē). But itīs the most robust material we had so far with the strongest seams and sturdiest surface.

We can ship both materials, just give us a note. Best is via email to info>@<windreiter.de
Mar 08, 2018, 04:15 PM
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Added link for my alternative 3D printed parts in Post #1
Mar 29, 2018, 04:18 PM
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And have a look on this steam punky built of the silent runner from Australia!

Chitty Chitty Bang Bang Airship test #1 (long video) (4 min 8 sec)
Mar 31, 2018, 11:46 AM
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Quote:
Originally Posted by wemperor
And have a look on this steam punky built of the silent runner from Australia!
Great Andreas!
I like this style of flying and V-tail is very efficient. Good job!

Denis
Jul 03, 2019, 10:26 PM
azadhindfauz

Envelope design and construction


Could you provide a step by step guide on envelope construction. Silent runner seems to be very crude in this regard.


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