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Mar 12, 2011, 03:00 PM
Potential Future Has-Been
Thread OP
Build Log

2nd Generation RC Thermal Blimp


Some of you might remember my build log for a thermal blimp a few years back. I've completely redesigned a new blimp and will be going another build log for it here. The new blimp is mainly just nicer looking, but it does have new features like vectored thrust, emergency fuel shutoff, fuel pressure gauge, better burner construction, modular gondola components, foldable props for storage, single continuous gore construction and carbon fiber fin support rods.

Here's the CAD drawings of what it will look like:
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Mar 13, 2011, 03:04 AM
Registered User
Just a thought, but wouldn't it be a good idea to paint the blimp black to absorb more of the suns radiation?
Mar 13, 2011, 12:04 PM
Potential Future Has-Been
Thread OP
The fuel savings from a black envelope would be minimal. You can only fly thermal airships at sunrise or sunset anyway due to their inability to handle any kind of wind, so the sun is at a low angle on the horizon during flight and not much of a heat source.
Mar 14, 2011, 01:22 AM
Potential Future Has-Been
Thread OP
Finished the frame in one day today! The burner assembly was already completed last week.
Mar 14, 2011, 11:10 AM
rc blimp manufacturer
powerblimp's Avatar
dear pyronaught,
congrat! that's really nice and innovative work!

i really think you may use dynamic tails even at low speed they are much more efficiant than a motor thruster like designed
if you really need to ues a back motor you should place it on end of the zepp so you will have more efficancy.

about the shape you could do a over pressurized sort of frame or skeleton that run from noze to back like a kite surf structure..

so you may have more strength and a better airdrag..

what's authonomy of your burner?

let's say at 20C ?

cheers phil
Mar 14, 2011, 01:52 PM
Potential Future Has-Been
Thread OP
The real purpose of building this airship is to prototype a full size version which I hope to build eventually. In the full size version there is actually a rudder on the bottom fin behind the vector fan, so that's why the fin is set back from the tail in that area. I just deleted the rudder from the model because I probably won't include it on the RC version, at least not at first. I'm leaving the space there in case I want to add it later though.

The envelope actually is pressurized via ducted fans on the burner. These fans serve the dual purpose of pressurizing the envelope while also driving out byproducts of combustion and feeding fresh oxygen to the burners continuously.

Not sure what you mean by "authonomy."
Mar 15, 2011, 08:47 AM
rc blimp manufacturer
powerblimp's Avatar
how long can you fly with te 2 propane tank
Mar 15, 2011, 12:19 PM
Potential Future Has-Been
Thread OP
Two tanks will handle inflation plus 15 minutes flying in 80'F weather, or about 20 min in 60' weather. After swapping out with two new tanks you can get 20 more minutes. The pressurization fan batteries will run out after 40 minutes, so unless you swap them out then that's the limiting factor.

A hot air blimp is a lot more sluggish and slow to respond than a helium blimp of same size. The mass of the air is about twice that of helium, so you have all that extra inertia to overcome when starting and stopping. It really doesn't fly well at all by comparison, especially since you have to always be focusing on burning at the right time and duration to maintain the proper lift. I've only flown them teathered, maximum 50 feet off the ground just doing small circles. It's good for attracting attention due to the large size however. I have an HID light system I hang inside to make it glow for night flying too.
Mar 16, 2011, 11:52 PM
Potential Future Has-Been
Thread OP
More progress today. Burner system is fully operational. A piece of teflon thread tape got into one of the valves and jammed it up, so I had to disassemble the whole thing to get it out.

The total weight of gondola with full load of fuel is going to be 22 pounds! That's a 7 pound gain over my previous gondola, so the new envelope will have to be slightly larger. This is probably the heaviest RC blimp gondola ever to fly!
Mar 21, 2011, 11:33 PM
Potential Future Has-Been
Thread OP
I got the propulsion system done over the weekend. The final gondola weighs in at 23 pounds fully fueled!

Well, that was the hard part. Now for the sewing
Mar 26, 2011, 08:31 PM
Master of Flying Wings......
im impressed!
Apr 04, 2011, 01:23 PM
Whats a search engine?
inventing_man's Avatar
Quality Workmanship Pyro . Well done
Ive often wondered why in THA 's ( the real ones) you would want to use prop wash to pressurize the envelope and tail feathers . Seems to me that a pneumatic skeleton of high pressure tubes , especially in the nose , A back bone and maybe side ribs too , plus tube pressurized tail fins would not be better and allow the ship a better weather window . . I realize the need for air exchange inside the main envelope for the burners and thus also providing envelope pressure . I also see and know why You need everything to deflate all at once , because ground handling can be a
BIT 6h ! But I still dont see where inflating a stand alone super pressure back bone, side ribs and a nose cone would not hurt if there was a way to deflate them too when landing to pack up . The tail fins Could be inflated once the ship is standing up Just Before take off to help with ground handling . I Kinda see the tail fins working like fins on a fish . The way they stand up and lay back with a thinner profile and a solid leading edge henged from the envelope that allows them to "fish fin" with the pneumatic pressure making them stand up .
Just thoughts here . Again Your Quality of workman ship is forthright !
IM.
Apr 04, 2011, 11:11 PM
Potential Future Has-Been
Thread OP
I've seen a design for one that uses pressurized tubes for the nose cone area to prevent cavitation. It was pressurized off the prop wash just like the typical tail fins however. For the real blimp I eventually hope to build I actually am working on a design for the fins which uses an inflated bladder constructed like inflatable rafts with all the tubes to give it rigidity. The main problem is venting excess pressure as the ship goes higher and then reinflating it as it goes lower again. Each fin must have it's own battery operated inflation unit. This method allows you to build a narrower fin with less drag, is easier to manufacture and stays inflated even when the main prop is not running (which is important for the way I plan to fly my blimp, which will involve lots of quiet drifting in the wind with the motors off and only using propulsion to get to a good landing spot or points of interest to the left or right of the wind direction along the way).

Deflating the fins will be the tricky part. I don't think you can run the inflator in reverse and suck the air out because it will just suction the passageway closed and block the air flow.
Apr 05, 2011, 04:20 PM
rc blimp manufacturer
powerblimp's Avatar
Quote:
Originally Posted by pyronaught
I've seen a design for one that uses pressurized tubes for the nose cone area to prevent cavitation. It was pressurized off the prop wash just like the typical tail fins however. For the real blimp I eventually hope to build I actually am working on a design for the fins which uses an inflated bladder constructed like inflatable rafts with all the tubes to give it rigidity. The main problem is venting excess pressure as the ship goes higher and then reinflating it as it goes lower again. Each fin must have it's own battery operated inflation unit. This method allows you to build a narrower fin with less drag, is easier to manufacture and stays inflated even when the main prop is not running (which is important for the way I plan to fly my blimp, which will involve lots of quiet drifting in the wind with the motors off and only using propulsion to get to a good landing spot or points of interest to the left or right of the wind direction along the way).

Deflating the fins will be the tricky part. I don't think you can run the inflator in reverse and suck the air out because it will just suction the passageway closed and block the air flow.
and why you don't make structure like kitesurf?
very high pressure structure with valve..
Apr 05, 2011, 11:48 PM
Potential Future Has-Been
Thread OP
I'm not sure what kitesurf is. I've heard of kite surfing, but I don't think those are inflated. They are more like very small parachutes.

A valve for venting air when flying higher would not be hard to do. A valve that deflates the entire fin in a reasonalbe amount of time for packing after landing might be more tricky due to the large size it would have to be. I'll have to calculate the volume of one of these fins and see how much air flow would be required to deflate one within about 10 minutes time.


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