Plantraco Custom Zeppelin (NOT blimp!) - RC Groups
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Dec 02, 2006, 11:45 PM
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Plantraco Custom Zeppelin (NOT blimp!)


I just ordered my Plantraco starter kit, and decided to go with a small indoor zeppelin instead of a plane. Looking for suggestions and tips on the design... Planning on balsa frame in 2 detachable parts with the envelope inside. I'll need to figure out what shape to use to minimize the frame's weight, as well as how small I can make it before loss of structural integrity due to miniaturizing the balsa sticks becomes an issue... Also looking for bag material; I have some nifty plastic wrap I got off some clothes from Sears that feels like (extremely thin) silk I was thinking of using, as I want to avoid ordering a special material online if possible, at least for the time being.

And, to emphasize, it's going to be a rigid airship, not a blimp - Zeppelins rock the faces off blimps, just because the word starts with a 'Z' (imo).

This will be my first of any kind of original design, so help is appreciated!
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Dec 03, 2006, 05:30 AM
Mostly harmless
first off... balsa wood is "heavy" and pretty fragile if you build in in the wrong way. I'm currently building a semirigid airship with fixed keel hanging on the envelope (I intend to get better load distribution this way). I have used two 5 x 0,5mm balsa strips with 10mm spacing between them and then crisscrossing balsa strips in between. It is very lightweight (only about 15 grams per metre) but extremely strong for its weight. string bracing can be considered. (look at the attachment).

With zeppelins... the initial shape of the zeppelin is determined by the framework. In terms of load however, these small model ones should have one strong keel at the bottom of the framework (ie. the bottom longeron is replaced by a rigid keel I presented). the other longerons would only make up the shape and provide some extra strength. This would hopefully help to share the load more evenly across the framework and allow more thinner balsa longerons to be added.

the ring frames holding the longerons together should be made of laminated balsa. Glue two thin strips of balsa wood together and perhaps include some pre-loaded strings between the strips. You should consider using two or three gas bags instead of only one. If there's space between the separate gas bags, you can install reinforced rings (strings going from every corner to the middle, the ring's got better integrity). with these radially reinforce rings are essential to keep the frame together and prevent it from twisting vertically. the other rings then would help to keep up the shape of the frame as well as providing some extra strength.

The shape of the envelope: For these sizes every gram of lift counts. WW1 cigar shaped zeppelins are out of the question if you have certain length limits. besides being very long and slim these can turn out too fragile. I'd go for something similar to USS Akron or R 100 if you want to build it to resemble some historical zeppelin. the bigger you build it the easier it is to compensate for the framework's weight. the example picture I made resembles something close to R 100's shape. it has only 115 grams of lift, so the balsa framework would have to be Extremely light (70grams tops to allow RC gear on board). I'd say 1,5 meters is the minimum if it still has to look like zeppelin instead of a sphere ... Bigger would b better

It is really hard to say for sure, there are so many variables, but these points should help you to get started... And while I was searching the net for flying model zeppelin, I stumbled into this: http:
www.starksravings.com/shenandoah/shen_model.htm
It is made by Tony Avak (I quess he is mentioned hre earlier), but he had his problems with lift it seems.

I hope this helps in some way
Last edited by Kernwrech; Dec 03, 2006 at 06:09 AM.
Dec 03, 2006, 12:09 PM
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Hmm... Looks like I need to do some research on the structures of the actual zeppelin type airships. Since the whole thing is curved, should I wet the balsa and bend it to shape, like the hull of a boat, instead of using smaller segments?

Also... While I am going to have to shave down the size of my balsa strips, I've noticed that - in general - structural integrity for weight tends to increase as one gets smaller in size. I'm thinking the resilience of small animals for scale stresses - I've seen my cats flip a mouse into a wall, which would be something like the equivalent of launching a person into the side of a 6 or 7 story building, without hurting the mouse... The same seems to apply to a certain degree to model aircraft; i.e. peanut scale models aren't anywhere near as complex as real aircraft.

So... Would such complicated measures really be needed to lend the thing structural integrity? I was originally thinking of an oversimplified octagonal or hexagonal shape made long enough to accomodate enough helium. I guess the other thing you have to take into consideration is what kind of stresses you expect it to have to endure. I'm using it for strictly indoor purposes, like flying around my house, so I wouldn't expect it to need as much strength as you're talking.

BUT, I'm not as experienced as I act either... I've built and flown a Delta Dart, and I've almost completed a Guillow Javelin (still making the landing gear and propeller assembly from scratch because I got the kit on eBay) and that's about the only experience I have so far with model aircraft. I also bought a Raidentech blimp and managed to get it to fly for a bit after attaching a pair of party balloons to it to increase the lift (radio was too heavy) before the radio got too glitchy to fly, and the envelope suddenly burst at the seam (curse you Raidentech!!).

Your post is definitely helpful, at any rate; it points out how much I don't know...
Dec 03, 2006, 08:58 PM
Registered User
See also this thread https://www.rcgroups.com/forums/show...highlight=R100.

The point about structural integrity and scale is right up to a point, but fingers don't scale with models. The biggest loads on small models, particularly airships, are handling loads. All breakages on my R100 were accidental damage during building and handling. And once the structure is covered, fixing a break is well nigh impossible (without stripping and recovering).

IMHO, if you're going to build a rigid, it has to be scale. What's the point otherwise?
Dec 03, 2006, 10:58 PM
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Thank you for that link, I've bookmarked it. And the bit about handling stresses is a point well taken. I was actually thinking about making the frame very sparse but using normal thickness balsa strip; the problem then becomes the ease of tearing the resulting large tissue surfaces. I am also considering carbon rods, but I don't know anything about how to work with them.

As for why I want a non-scale rigid... Well, the reasons are several. One, I like them better on principle. Two, I would prefer trying to make a balsa frame look pretty over trying to make a metalized nylon or plastic envelope look pretty. Three, I intend to build rigid airships in full scale some day, and I see this as a learning excercise.
Dec 04, 2006, 06:11 AM
Marcus Franco
Guga's Avatar
Quote:
Originally Posted by Kinotoko
This will be my first of any kind of original design, so help is appreciated!
Kinotoko...
A while ago there was a post about this guy that built this rigid R-100 ...
I saved the pictures but I donīt think the post exits no longer...
Dec 04, 2006, 09:55 AM
Registered User
Kinotoko's Avatar
That's a beautiful ship. Thanks for the encouragement; I couldn't find the post either but I'll study those pics.
Dec 08, 2006, 05:09 AM
Marcus Franco
Guga's Avatar
Kinoto...
I just Found the name of this gentlemen that made this R-100 is Allan Sherwood...
You can see the original pics at http://www.ctie.monash.edu.au/hargra...cof2003_2.html

He is from Australia and he is a member of the Rcgroups...you can send him a PM at https://www.rcgroups.com/forums/priv...=newpm&u=64706

Good Luck...Guga
Dec 11, 2006, 08:08 AM
rc blimp manufacturer
powerblimp's Avatar
may be you can directly glue thin balsa or carbon rods on the PU gas bag, then cover the whole thing with mylar.
the structure will appear.
it will be sort of semi rigid blimp structure only "for the look"

cheers phil
Dec 15, 2006, 11:51 PM
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Well, I changed my mind for now and decided to make a BUMP.

*sigh* so much for being a radical non-conformist.

But, I'll still do this - soon. Probably after I get the equipment and can see how much it weighs, etc... I'll need a couple more pager motors too, and I'll need to figure out how to rig the receiver to work with motor throttles instead of actuators... I've never worked with an R/C radio before.

The R100 - Alan Sherwood did that?? I'm surprised he hasn't posted in this thread then :(

I'll have to PM him about it.
Dec 18, 2006, 03:33 AM
Registered User
Quote:
Originally Posted by Kinotoko
The R100 - Alan Sherwood did that?? I'm surprised he hasn't posted in this thread then :(

I'll have to PM him about it.
Kinotoko, does your memory leak like a balloon made of flyscreen? Look back to post #4. You even commented on what I said in your next post!
Dec 18, 2006, 06:52 AM
Mostly harmless
We are all only human beings, mistakes are what we do best after all

Alan, do you have any detailed info for us about your R100? I'd like to know how much weight does that framework have and how much lift is left over.
How many gas bags do you have inside or is that all filled with helium?
Dec 19, 2006, 10:10 PM
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Haha, wow... I feel dumb. I remember your post now, but I didn't remember it being you - and I guess I somehow missed your link...

I changed my mind again and decided to build a profile guided mite. I know, my aspirations are getting higher and higher.

Actually, the reason for that is that the BUMP isn't even scale-like - I figure if I'm not making something that at least looks scale, I might as well make a profile model and save myself some effort... I wanted to try to design my own, but I have no idea how to build to a certain weight - not enough experience.

For the zeppelin, when I make it, I'm going to design it on paper first, then do all the math and make sure the envelope can provide more than enough lift, before I even start building it... My Plantraco gear finally arrived today (!) so I can start experimenting comfortably.

One thing I need to know; can I connect a pair of pager motors to my Plantraco receiver instead of actuators, to use in a traditional tri-fan control setup for an LTA craft? I should think so, since I think their microblimp uses the same receiver.

AFAIK the Plantraco HFX900 is just a normal radio system, albeit on a smaller scale, using 'digital'(?) 900mhz...

EDIT: Kern, a note about filling a rigid ship entirely with helium - You would have to displace the air inside first somehow, which would be a challenge. Either that or make a bare frame and inflate an envelope inside, which wouldn't be anything like traditional rigid construction. I was thinking about a complicated process of leaving an opening for air to escape, then inflating an envelope inside, then sealing the rigid frame's opening, and deflating the inner envelope and pulling it out at the same time... if that makes sense. Bit too complicated for the weight saved, though, and just as big a pain to repair.
Dec 20, 2006, 01:48 PM
Mostly harmless
Kinotoko
That methode would actually work! An envelope (nothing fancyer than a sack larger than the hull) filled with air, emptyed by the force of the helium and finally extracted... The airship would be lighter but more complicated in terms of structure. and having the framework inside the gastight envelope would make it impossible to repair in case of a fracture

Hmm... Wouldn't it just be best to keep simple and simply have couple of gas bags inside the hull? Weighty it might be, but simpler in terms of filling and building. and: if you have gas bags, there is no reason for the outer hull to be airtight. thus, the filling wouldn't be a problem, emptying would as presented here: www.starksravings.com/shenandoah/shen_model.htm Besides, If you crack the frame for some reason, it can be repaired by simply cutting away some of the outer cover, making repairs and re-covering the gap with similar material.

One different possibility is to simply build a blimp envelope of suitable size and shape, and then glue those flexible carbon fible sticks to it, forcing it to have rigid lines. it could be inflated/deflated almost as a blimp envelope, but it would have some "zeppish" outlook...

One extra poin to this soup of speculation: I always make large glider wings (>180cm) in several sections that can be assembled together on site (allowing the transportation of the wing in car trunk). So, to allow somewhat larger zepp to be built, why not to make the hull in two or several parts, which are lined by some kind of pin-collet system and held together by rubber bands or something? It would be more transportable, and if done carefully, the seam would have very sublte outlook (if the lineup mechanism was installed inside the hull). by transporting the hull in pieces might also reduce the risk of breaking it.

I finished the rigid keel section of my new blimp (It consists of two pieces that are joined together by pin-collet system). the keel is 1,5m long, very strong, but it weights only 6 grams. I made it out of one 0,5x5mm and one 1x0,5mm balsa strip, which are connected by crisscrossing intermediate balsa pieces. it is only sligthly flexible, and holds up its form nicely. Now only the envelope remains to be finished (got 5 out of 6 gores glued so far, with varying success).

Sorry, When I get carried out, I write novels. I hope you'll have the patience to read my postings
Dec 21, 2006, 02:52 AM
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Kern, your posts are nothing compared to some I've made in the past (on other forums).

I was planning on making the frame in 2 parts, actually, to facilitate filling and removing/replacing the bags. Normally you would go physically inside the airframe, but models aren't big enough for that... Now that I think about it, I think I'll make the frame in 3 parts total; 2 parts for the lifting frame and 1 part for the gondola. I'll figure out a good way of putting the parts together and make a nifty design based on that arrangement.

As for something Alan mentioned, I'm not going to make a scale model - but I AM going to make it 'scale-like'. I'll try to use cellophane or something to add windows to the underside, like on the Hindenburg, etc.

On a related note, I was in Bed, Bath & Beyond today and they had 4-channel blimps with tri-fan controls plus a light show on clearance for $24.99. I was with my parents, so I made a new christmas gift request... Hopefully this one (from Megatech) will be better than my Hong Yan brand heavier-than-air blimp that operates on the most heavily trafficked frequency in my house... They also had differential-thrust planes like Aero Aces, but an off-brand; they didn't LOOK particularly sub-par, but they were the same price as real Aero Aces so I passed. They might have been made of EPP though, not sure.


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