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Old May 05, 2009, 02:01 PM
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Milpitas, CA, USA
Joined Apr 2009
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For simple endurance, you might get almost as long by leaving off the burners and heating it up on the ground. I'm seeing 5 or 6 minutes with ~700 cubic foot thin plastic bag, your bigger envelope might carry just propulsion for 2 or 3 times that long. Of course you'd loose altitude control, it might climb 1500' or more (better check RC range...) and landings would take more planning. On the advantages side, you could use a big 20lb propane tank. Thanks for all the pics & stories!
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Old Aug 14, 2009, 09:44 AM
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Joined Feb 2009
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New Update!

This project sat idle for a few months while I waited for new motors, but I'm back working on it again now. The old Turnigy motors were replaced with Reaper GR-60s, which not only turned out to be more powerful but also freed up one pound of weight by being considerably lighter. So the motor problem is fixed.

The steering problem is not fixed however. I tried a single bottom rudder controlled by a winch servo on the gondola, with control cables running out to the fin. This type of setup might work in gas blimps where the envelope pressure is much tighter and more constant, but I don't think it is workable for a small RC hot air blimp. Hot air blimps have flimsy fins and low pressure envelopes that vary in tightness depending on the internal temperature. Thus the cables leading to the rudder will go slack sometimes and become worthless. You also can't put any tension on the cables without pulling the entire fin attachment towards the gondola. I just don't see it working, and the long cords make for entanglements during packup and additional time spent hooking them up during launch. Maybe a servo could be attached to the fin itself and control a rudder that way, but my fins are just sheets of fabric with no real hard point to attach anything to. Not to mention my blimp is already tail heavy as it is, and moving the gondola forward is one hell of a lot of work. The two chamber design also requries the gondola to be as close to the center point as possible. So I'm nixing the rudder idea.

I'm going back to independently throttled props like the orignal design, since it is simpler, keeps weight off the tail and makes launch and deflation easier. Only this time I'm going to extend the props out away from the gondola by about two feet on each side. This gives a 2.5 foot moment arm around the vertical axis, which could generate seven or eight pounds of torque when only one motor is run at full speed. Since this whale of a blimp is a slow moving beast for calm weather flying only, it doesn't matter if it can't make sharp turns.

Stay tuned!
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Old Aug 18, 2009, 12:19 AM
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Kentucky
Joined Oct 2008
189 Posts
Awesome project, Pyro! I should have checked this one out sooner.
Rigging it to were you can turn both motors on or one at a time would probably work for steering it and forward propulsion.
I'm sure if you use reversible ESC's on those GR - 60's in a "full port engine and reverse starboard engine and visa-versa" that they'll have no problems turning that big baby!
Not to menchan awesome forward and brake/reversing speed.
I noticed on your original post that you inquired as to info like the (reversible)ESC's used in r.c. cars.
Most ESC's (including reverible ones used in r.c. cars) are compatible with most any receiver even aircraft radios.
The way my twelve foot blimp is set up it has a reversible ESC that controls the tailfin motor that controls yaw. This comes directly from the Futaba receiver.
This may also be another option that you could look at (tailfin motor that turns the craft).
Because the tailfin motor is all the way out at the end of the blimp, it requires MUCH less power to steer the blimp instead (just think about the leverage physics) of the high torque needed at the gondola to be able to steer (yaw) the blimp. Just something to ponder...
However, I believe the GR 60's will have no problem turning the blimp.
ESPECIALLY if you set it up were they run in opposite directions when you steer as I menchaned above.

It shouldn't be to hard to accomplish this. I'm not sure how many channels you are using with your current set up, what with the burner controls and all.
How many channel radio are you using?
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Old Aug 18, 2009, 09:26 AM
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Joined Feb 2009
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I have six channels to work with, although the landing gear channel broke on my transmitter so I really only have five working channels now. I rigged both burners up to the same channel, then there's a channel to shut off the pilot light so all fire can be snuffed out when landing. If a valve ever stuck open during a burn I'd be screwed though since I don't have a channel to shut off the fuel supply at the source. That would be a very bad situation so I have to fly the blimp tethered until I can fix that potential hazard. When the pilot light is shut off, the main fuel lines can still be run, which is neccesary to cool the coils after a landing by blowing unignited gas out the burners for a few seconds. Otherwise the hot vaporizer coils would melt a hole through the fabric if the wind caused the envelope to roll over on them.

So two channels are used on the burners, with a third channel getting added for fuel shutoff in the future. Two other channels are used for independent left and right throttle on the motors.

I never did wind up using reversible ESCs because I couldn't find a suitible one, so currently I can't reverse the motors. At full speed they draw about 40 amps, so I'd need at least a 50amp reversible ESC for brushless motors that can handle six LiPo cells. Seems like most of the reversible ESCs for cars were for two wire brushed motors. I never could find a reversible ESC for brushless motors with the current capacity and cell count I needed.

I did contemplate a tail fin motor and it was planned for the original design, but I ran into too many problems with the blimp being tail heavy even with nothing but the fins back there. Since the blimp must be divided into two chambers to control runaway pitch from rolling hot air, I am limited in how far forward I can locate the gongola. Since both burners are attached to my single gondola, the chamber divider wall must be located directly above the gondola. It's already about as far forward as I can make it, and even now I have to burn over twice as often on the rear burner to keep from going tail heavy. To locate the gondola more toward the front would requrie adding a seperate gondola for the rear and splitting the two burners between them. This way the divider wall could be left at the center of the envelope regardelss of gondola position. This would complicate the design, add more weight and increase the setup time however. I like the simplicity of the single gondola design I currently have (if the word "simplicity" can even be used when talking about something as inherently complex as a hot air blimp!)
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Old Aug 18, 2009, 09:48 PM
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After getting a taste of how expensive it is to fill helium airships, I really have more appreciation for this hot air blimp! It really costs almost nothing to fly it by comparison. I think it works out to $2.50 per 30 minutes for the propane fuel, which I buy in 10 gallon increments from a hot air balloon refueling station. It would cost you a small fortune to fly something this big on helium! For really big recreational blimps, hot air is the way to go. You get to walk around inside a thermal blimp while it is inflating too, which is kind of neat to see from the inside. It actually seems bigger from the inside because you can view the entire volume all at once.
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Old Sep 12, 2009, 10:45 AM
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Joined Nov 2004
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I'm all for the portability of a hot air blimp/airship. Here's a follow up to the HeiDas project which may be of interest since the team have gone on to develop an airship

http://www.isoluftschiff.de/englisch/english.html

Although the details are sketchy, I believe they use internal stringers to maintain the structual integrity of the hull shape and utilise a double layered material (may be expensive). I was wondering if one could use balloon ripstop (Gelvenor) for the outer outer envelope and the metalised fabric described on this site (www.flyingkettle.com) for an internal envelope and use steam to pressurise the envelope to maintain its' shape.
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Old Sep 12, 2009, 11:23 AM
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A steam airship would be the most difficult type of airship to build, even as an RC model. Containing the high temperatures to avoid condensation is a real materials challange. Trying to maintain that high temperature without burning through a bunch of fuel requries a type of insulation that is both light weight yet with low thermal conductivity-- two requriements that tend to be mutually exclusive. HeiDas has produced some very good materials for this and they are closer than anyone has ever been, but I don't think they are there yet. There is also the problem of envelope pressurization. Hot air blimps have poor speed limitations and limited flying conditions because their envelopes can not be pressurized as much as a gas blimp. The same problem is going to be there with a steam airship. The other problem is generating the steam for the initial fill. This either requires a cumberson boiler setup with a large supply of water or an expensive oxygen/hydrogen mixing machine like what the HeiDas guys use (with heavy and expensive oxygen and hydrogen gas tanks to be refilled for each flight). Neither one is very practical for a hobbyist to haul out onto the flying field.

I think for RC blimps the hot air method is best because it is more simple, cheaper and you can keep changing out fuel tanks in the field since the blimp flies around the same spot. For a real passenger carrying thermal blimp then steam would allow twice as much lift as hot air, but there are still hard problems to overcome like insulation and pressurization. Hopefully someone like the HeiDas group will succeed some day. The main problems can only be solved by advances in material science.
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Old May 14, 2013, 10:54 PM
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Colombia, Bogota
Joined Jun 2010
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Help to Rc blimp Colombian Project.

Quote:
Originally Posted by powerblimp View Post
hmm power is small

we do use on a 6m blimp 800W motors and 4s batt + 14'' props!

so i think you are really under powered as you shape is much less streamlined as a helium one..

but very nice work may be the future as helium is more and more rare!
Hello. I need some help with setup blimp 6m. My setup : 2 x Turnigy C3042 1000kva + 3 x Lipo 3S 5000 mah + 50amp Hobby king ESC + 12 x 4 Apc E props. Thi is the best configuration for wind between 4 to 6 mah.

What do you recommend ? Thank for help me.
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Old Jun 30, 2013, 11:21 PM
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United States, FL, Niceville
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wow! This looks great
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Old Jul 03, 2013, 04:39 AM
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Switzerland, VD, Crans-près-Céligny
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i will suggest 3 x lipo 4S 3000 mAh .. and 14*7 prop or less pitch
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Old Aug 06, 2013, 07:42 PM
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Pyronaught:

Great work and information! My interest is in a project building a new family of super economical to operate, super safe and super cheap to build personal flying vehicles, first as remote controlled models and then as manned prototype aircraft.

Several lines of research and development are currently closing in on these objectives. One line of research seeming to be near a practical solution is a bicycle or motorcycle fitted with many propellers or thrust ports controlled by computer and a joy stick.

Another line of development could be the hot air Turbo Zeppelin design. Instead of pushing the air around the vehicle, the air in the path of the vehicle is sucked in a funnel shaped nose to feed a central axis mounted pulse jet engine which runs on hydrogen gas as fuel. The hydrogen fuel adds to the lift and payload of the vehicle at take off, is cheap, can be made at home, is widely available and burns clean. The heat from the simple pulse jet or V1 type engine is captured along the length of the central tube with fins into many chambers, but the exhaust gas of water vapor, steam and water droplets exits the back.

The hot airship that pyronaught built was said to use 2 lbs of propane every 15 minutes or about 8lbs of propane an hour to keep it operational. Heat is transferred in only 3 ways, conduction, convection and radiation. Radiation from a 200 degree F. ship to and 50 degree F. air can not be too great. Convection is leakage of heat in hot air out of holes in the fabric and heated air moving at the external surface of the ship. Conduction of heat across the very thin and light material of the envelope is probably the costliest factor in maintaining lift..

Aerogell insulation developed by NASA that is extremely light and efficient would make a better skin for a hot air vehicle.than what is used now, but it is rigid and would best be used in a hexagonal or octagonal cross sectioned rigid vehicle. Rocket jet and pulse jet engines put out more thrust than electric motors and their heats of combustion can be converted to lift when their heat is captured and transferred to air along the central tube that is feeding the air and compressing the air that used to be pushed out of the way now is used for the engine.
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Old Sep 05, 2013, 10:16 PM
Team WarpSquad (Ground Crew)
Côte d'Ivoire
Joined Jun 2012
978 Posts
First of all, compliments on all the development work you have done, Pyronaught. I've been following hot air airships for 20+ years, and I believe there is still room for improvement.

I was also delighted to read that you are hoping to scale up this project to man-carrying size. That is exactly how I moved from RC to manned flight many years ago. (I think you mentioned that you fly hot air balloons also.)

Quote:
Originally Posted by pyronaught View Post
After getting a taste of how expensive it is to fill helium airships, I really have more appreciation for this hot air blimp! It really costs almost nothing to fly it by comparison. I think it works out to $2.50 per 30 minutes for the propane fuel, which I buy in 10 gallon increments from a hot air balloon refueling station. It would cost you a small fortune to fly something this big on helium! For really big recreational blimps, hot air is the way to go. You get to walk around inside a thermal blimp while it is inflating too, which is kind of neat to see from the inside. It actually seems bigger from the inside because you can view the entire volume all at once.
I couldn't agree more on this! Unless you have deep pockets and lots of manpower, helium is just too expensive and a pain to handle. Now that we have brushless motors and LiPo batteries, chances for an improved hot air airship design may be better than ever.

Quote:
Originally Posted by pyronaught View Post
The old Turnigy motors were replaced with Reaper GR-60s, which not only turned out to be more powerful but also freed up one pound of weight by being considerably lighter. So the motor problem is fixed.
Any update on how the Reaper GR-60s worked out for you? It's been a couple of years since your last update. Maybe you are working on the manned version of your hot air airship now, and reporting on your progress somewhere else?
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Old Sep 05, 2013, 10:28 PM
Team WarpSquad (Ground Crew)
Côte d'Ivoire
Joined Jun 2012
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Originally Posted by M.Boelling View Post
It think it will help doing rudders on the bottom fin. As the propellers are blowing onto the fin it will react very good and as there are very small and light servos available that should not be too difficult.
In a big hotair airship we do the same. Full engine and then rudder and you nearly turn around on a point. The top fin doesn't get the prop stream so I would test it just with the bottom fin and point the engines directly to it.
Good comment about prop wash generating airflow over the bottom rudder, Michael. Especially since you have lots of experience in the airship arena, both with hot air and helium!

Freut mich übrigens dich hier zu sehen, Michael. Ist schon elend lange her, dass wir für die Konferenz der Airship Association zusammen in Friedrichshafen waren. Ach ja, mit Kindern ändern sich unsere Prioritäten.

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Originally Posted by powerblimp View Post
i will suggest 3 x lipo 4S 3000 mAh .. and 14*7 prop or less pitch
Is that you, Jodoc? It's been even longer since you were launching MiniZepp and we saw each other in NYC. You've obviously had time to learn about brushless motors and LiPos and implement them on your RC airships.

Quelle bonne surprise de te retrouver sur ce forum! On dirait que tu as passé la torche à d'autres propriétaires pour tes dirigeables RC. J'espère que la transition a été gérable et que ton nouveau job te fait plaisir aussi.

Gentle winds and soft landings!
-Roland
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Old Sep 06, 2013, 08:26 AM
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Quote:
Originally Posted by EarthCopter View Post
First of all, compliments on all the development work you have done, Pyronaught. I've been following hot air airships for 20+ years, and I believe there is still room for improvement.

I was also delighted to read that you are hoping to scale up this project to man-carrying size. That is exactly how I moved from RC to manned flight many years ago. (I think you mentioned that you fly hot air balloons also.)



I couldn't agree more on this! Unless you have deep pockets and lots of manpower, helium is just too expensive and a pain to handle. Now that we have brushless motors and LiPo batteries, chances for an improved hot air airship design may be better than ever.



Any update on how the Reaper GR-60s worked out for you? It's been a couple of years since your last update. Maybe you are working on the manned version of your hot air airship now, and reporting on your progress somewhere else?

This thread is a build log for my earlier attempts at making a hot air blimp. There is a second build log that contains the details of the finalized design which was a success: http://www.rcgroups.com/forums/showthread.php?t=1405313

I have not started work on the manned version yet, that is still some years away. Currently I am building a CNC fabric cutter to make this job easier, which I will test on an RC balloon first followed by a full sized balloon envelope. The cutting table is 6ft x 16ft and I was just barely able to squeeze it into my garage! I might post a build log on making the table, or at least a link to the build log I plan to put on cnczone.com.

BTW, Reaper Brushless Motors apparently went out of business, which is unfortunate because the GR-60s worked great and they made a really nice motor for a reasonable price.
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