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May 29, 2021, 10:54 AM
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Build Log

RC Goodyear Blimp


Hello, this is a build log for my attempt at creating a medium size outdoor RC blimp. I wanted to make a flying scale model of an actual blimp, so I chose the first Goodyear Blimp, called Pilgrim, from 1928.

I chose to model the Pilgrim as it was a single engine airship. I have built a few airships in the past. All of them used differential thrust or vectored thrust to steer, this time I want to use the elevators and ruder to steer (like on the actual blimp). The Pilgrim is also simply a good generic blimp to model.

Specs for the model
• Length- 7ft/2.1m
• Envelop diameter- 29in/73cm
• Volume- 19cubic feet / 0.53 cubic meters
• Total lift (approx.)- 500g
Last edited by Q airships; May 29, 2021 at 03:29 PM.
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May 29, 2021, 10:56 AM
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Video of the Pilgrim


Here is a short, interesting video of the blimp landing on the roof of a building.
USA: QUIRKY: "Pilgrim" Goodyear airship lands of roof of U.S department store (1928) (0 min 29 sec)
May 29, 2021, 03:45 PM
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To make the envelop for this blimp I decided to try a material that I have never used before, model airplane covering film. It is a heat sealable material that comes in a long role, it is not ideal for weight, as it is a reasonably thick material. However, it is heat sealable, durable and easy to use, it is also comes in gray (the right color for the blimp). The material is gas tight, I made a small test balloon and even with a book on top of it, I could not see any difference in its pressure for quite a few days.

The envelope will be made from 6 gores. Each gore weighs 31g for a total envelope weight of 186g.
unfortunately, I could only fit 4 gores on my role of material so I had to order a second sheet to make the remaining 2 gores.

In the meantime I will be working on the gondola and fins.

The specific material I am using is: "Dancing Wings Hobby RC Airplane Covering Film 60 x 200 cm Silver Heat Shrinkable Covering Film"
May 29, 2021, 11:29 PM
Melbourne, Australia
Looks grand!!

How are you going to do the end bits? (e.g the nose cone and tail cone?). I always have trouble with those bits using heat sealing, at least if I'm trying to get the seams on the inside...!

By the way, I think your model spec says around 2.1m length, but your gore material is only 2m in length? Are you modifying the design slightly?
May 29, 2021, 11:53 PM
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2.1m gores


As for the gores, thank you for pointing out the gore length issues. The 4 gores that I cut from the original sheet (shown in the photo) are 2.1m long, as the original sheet was about 5 meters long. It seems that I did not realize that the new sheet I have ordered is only 2 meters long. Hopefully I will still be able to cut the remaining 2 gores from the sheet diagonally, if not, I will have to make them work in another way.

I will make another post soon about how I might tackle the nose and tail cones.
May 30, 2021, 12:08 AM
Melbourne, Australia
P.S. very interested to hear how the material goes - I haven't use heat shrinkable plastic, but I can see where it could be very neat when trying to make replica rigid body models... do you know what the weight is per square meter?

P.P.S. - I'm still not sure about your width measurements :-) ? If you're doing 6 gores on an airship with a 73cm diameter, I'd expect the gores to be 73cm x pi / 6 = 38cm wide? So getting four of those out of one of your sheets wouldn't be possible, so maybe you've adjusted your design? The gores look very slim though, so I'm wondering if you've made them 1/12 rather than 1/6 (which would be cool by the way, it would look smoother..!)

On the offchance it could be useful, I've run off two gore designs from my airship designer program, both for a 210 x 73 teardrop airship, similar (but not the same as) your goodyear blimp - the 8 gore design has a width under 30cm so you could get two out of each sheet (although you'll need a separate tail to get to 210 if you're using 2m length sheets. Or if it helps I'd be happy to run off something else to fit inside the 2m length :-) ?

And yeah, to get the extra length you can try top-and-tailing them at a bit of an angle, but I've never had that much luck myself!
May 30, 2021, 01:33 AM
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Very interesting. I've been working on designs for a Navy L class (Goodyear) blimp myself. You should be in good shape at this size, even with the slightly heavier envelope material.

Have you given much thought to how you'll construct the tail surfaces yet? There's not a lot of lift available in the tail end so anything attached back will need to be extremely light. And you'll have to balance the buoyancy with heavier things in the front. The weight of the car will help, but it's not very far forward.

You might find you have more than enough lift to float her with all the required parts, but not enough lift to level her out with dead weight in the nose.
May 30, 2021, 10:04 AM
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Tail surfaces-part 1


You are right, the tail surfaces will need to be quite lightweight, especially on the Pilgrim where the fins are surprisingly large compared to the overall blimp.
There will also have to bee three 5 gram servos back there. The reason only three, not four is because the top fin did not have a rudder.

I am going to try two different designs for the first fin.
Design 1: first, I will try cutting the fin shape out of foam poster board, I used the foam board to make the fins on a model of the Zeppelin NT and they were very light.
Design 2: If possible I would like to make the fins out of balsa wood coved with the same material as the envelope, this will probably be heavier but will give a more realistic appearance.

If the covered balsa is significantly heavier than the foam fin, I will use foam for all the fins.
Last edited by Q airships; May 30, 2021 at 10:10 AM.
May 30, 2021, 11:02 AM
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An 8 gore airship!


"6 gores on an airship with a 73cm diameter, I'd expect the gores to be 73cm x pi / 6 = 38cm wide?" Thank you for this information. You were correct, my gores are too skinny for a 6 gore airship, the are 28cm wide, not 38cm. After redoing my calculations, I realized that I have actually made an 8 gore airship!

73cm x pi / 8 = 28cm -(28cm) =width of my gores

This will mean that I will need another 2 gores, which means I will need another sheet of material. The upside is that an 8 gore envelope will indeed look smoother than a 6 gore envelope.
Also, to get a 210cm gore from the 200cm sheets, will mean that I will have to splice the extra 10cm on at the nose or tail.

Finally, I believe the the material is 38 grams per square meter.
May 30, 2021, 12:21 PM
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Here are some photos of the Pilgrim's gondola (which still exists in a museum).
When I build the gondola for the model I will try to include as many scale details from real airship's gondola as I can.
May 30, 2021, 12:41 PM
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12 gores would get you closest to the scale envelope, if you can manage cutting 12 gores exactly to shape. Every dimension error gets multiplied by 12. Not to mention the extra work...

38 grams per square meter is not the worst. Buy comparison, fluffy foil is just over 29 grams. Emergency blanket foil is only 6.6g (if you can find a way to glue/tape it). If you find you don't have enough lift left after this build you have options.

How much "stretch" does this material have? If it's got some give you can use inflation pressure to smooth out any discrepancies. You're gores will not be ideal, no matter how you calculate them. This is essentially a round object constructed of flat surfaces. Pressure will force the flat sides of the gore out, causing the edges (seams) to bunch up and wrinkle. If the material can stretch, the center of the gore will expand until the curve matches the seam and the wrinkles disappear. The real blimp envelope was also constructed with gores, but the gores themselves were made from smaller strips (the vertical lines) that would have been tapered to give the gore a complex curve shape

If IRC, this material is designed to shrink with the application of heat to smooth out wrinkles covering aircraft, but I suspect it will probably be too sensitive to make use of this quality to remove envelope wrinkles. If you can pressurize the envelope significantly and very, very carefully apply heat along the seams you may be able to draw them in to a wrinkle free smooth shape. But you're more likely to overshoot the heat and cause the material to shrink to far. It's surprisingly easy to turn an envelope into a lopsided mess. I don't think I'd risk it. An ideal material would soften and stretch more with heat so you can gently stretch out the center section of the gore to match the curve. That's the opposite of what this material is intended for.
May 30, 2021, 12:51 PM
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Anyone know when she got a "wheel" under her? Most early photos show her having a simple bumper bag.
May 30, 2021, 01:14 PM
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I do not know exactly when the landing wheel was added, possibly after the blimp got a new envelop in April, 1929, and was christened "Pilgrim (II)"

I plan on including the wheel in my model.
May 30, 2021, 08:50 PM
Melbourne, Australia
Very nice! And 8 gores will make a nicer shape; as Rozam says its always a bit of a kludge, but I generally find reasonable results with 8. Try 'top and tailing' the gores at an angle on your sheet, you might just be able to squeeze in the extra 10cm, especially as with 28cm width gores you've got a little more play...

Re the foam fins - if you're really hard up for weight, you can always sand them down a bit - depending on the type of foam, I find fine paper will thin them out quite nicely, and you can leave the base thick for good attachment.
May 31, 2021, 05:52 PM
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Quote:
Originally Posted by pegacat
P.S. very interested to hear how the material goes - I haven't use heat shrinkable plastic, but I can see where it could be very neat when trying to make replica rigid body models!
I have thought of a rigid airship using heat shrinkable airplane covering material. It would make a nice finish because it can shrink and become tight over a framework.
I might try something rigid after I finish this Blimp
Last edited by Q airships; May 31, 2021 at 07:43 PM.


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