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Old Apr 25, 2012, 10:53 AM
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This morning was perfect weather for blimp flying so the maiden voyage of the new blimp was completed! The new burners fixed the lift problem and it actually got off the ground no problem this time. One of the pressurization fans threw a prop shortly after liftoff however so the envelope slowly lost pressure and the tail started to sag after about five minutes. I need to get a new ESC for the tail motor that works with a 3s battery, since I accidentally ordered the wrong one and have been using a 2s battery which is not strong enough to turn the blimp reliably.

The blimp is tail heavy when flying with only two tanks of fuel, so I either need to move the gondola forward or fly with four tanks of fuel to balance it out.

I have some video below, but I was not able to film the actual flight due to the impossibility of taking video and flying at the same time. So this just shows the inflation right up to the point of actual lift off.

Blimp Test Inflation (1 min 38 sec)


Here's a picture to prove I actually did fly it a short distance:
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Old Apr 26, 2012, 09:47 PM
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The weather is looking good for more test flights for the next two mornings. I fixed the pressurization fans and ran them in for the full duration to make sure they won't break again. Reprogrammed the ESC on the tail thruster to get more thrust out of it and also sewed a weight pouch onto the nose for adding counterweights. I also modified a hat to have a head-mount iphone for hands free video, so I should finally be able to get video of this thing flying
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Old Apr 27, 2012, 11:08 AM
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This flight was plagued with problems and a head mounted iphone doesn't produce the best video in the world, but better than nothing I guess. The front burner kept blowing out its pilot light, the load cables are too long and is putting stress on the envelope above the gondola and the tail fan needs a bigger battery. All these problems led to aborting the flight.

Test Flight #2 (3 min 30 sec)
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Old Apr 27, 2012, 11:31 AM
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congrats!
it si really cool! well HOT!!!

keep going

cheers phil
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Old Apr 27, 2012, 01:20 PM
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Next time I will just put a normal video camera on a tripod at a fixed viewing distance and film it that way. Anything else just moves around too much.

I think the next flight should have all the bugs worked out. There's four major things I have to fix and that should do it. One involves ordering a new ESC that can handle 4S LiPo though. The tail motor currently has 3S and that is not enough thrust for turning. It's a 400 KV, 1400 Watt motor with two 12" props on it and can go as high as 8S if needed.

Do you use car/truck type ESC for your tail motors to get the reverse capability? I can't find any plane ESCs that have reverse, only car ESCs.
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Old May 05, 2012, 11:25 AM
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Here's some stable video of the blimp actually flying this time. Still problems with the front burner though, which is why it kept nose diving at the end. Turning takes too long, so next is more power to the tail motor via bigger battery.

RC Hot Air Blimp Test #3 (11 min 50 sec)
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Last edited by pyronaught; May 05, 2012 at 11:57 AM.
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Old May 05, 2012, 02:51 PM
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better and better !
really cool work.
thank you
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Old May 05, 2012, 10:40 PM
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Thanks powerblimp! I think this project is really getting to the final stages now. About the only thing I need to work on is getting the tail fan to have more thrust. I'm currently using a 1.5KW 400KV motor with a 3S battery and two blade prop on each end of the shaft. Originally I had a 4S battery for it but bought the wrong ESC so am using 3S for now. The new ESC is coming though, so hopefully that does the job. What kind of ESC do you use for your tail props? I've been using the car/truck types because they seem to be the only ones that have reverse. The boat ESCs have reverse too but they are designed to be water cooled so that is unusable in an aircraft. It seems like the car ESCs don't drive the motor with as high RPMs for a given battery/motor combo as compared to the airplane ESCs. Do you know if that is true?
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Old May 06, 2012, 01:19 PM
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hello i use the CC controller for crowler buggy
they have both way without timing like brushed motors
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Old May 06, 2012, 02:16 PM
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I should also just go ahead and add a rudder to the lower fin and see how well that works compared with the fan. It would certainly be a lighter weight solution.
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Old May 09, 2012, 08:22 AM
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Interested

Hi pyro,

As I am disabled and use a wheelchair, I am looking for someone to build one of these for me to use. Please can you give me an idea of costs and where I would be able to buy parts etc. I currently fly heli's and multicopters so I'm hoping to purchase a thermal airship next. Thanks
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Old May 09, 2012, 02:12 PM
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Quote:
Originally Posted by Hobby guy12 View Post
Hi pyro,

As I am disabled and use a wheelchair, I am looking for someone to build one of these for me to use. Please can you give me an idea of costs and where I would be able to buy parts etc. I currently fly heli's and multicopters so I'm hoping to purchase a thermal airship next. Thanks
Costs are over $2000 just in parts alone for a ship this size. Then you would need a $1000 sewing machine to even get started, not to mention a 6 foot wide x 48 foot long table for cutting the fabric. There are no plans or documentation for building these, I'm pretty much pioneering this myself. The verdict is not in yet on the practicality of using these as I'm still tweaking the design. It is not something you would want to put way up in the air though, due to the expense and hazard that would occur if it got away from you. Thus it would be a lot of money to spend on something to just lumber around below 50 ft altitude. The challenge of trying to maintain proper buoyancy while flying is fun though.

Here's some interesting stats:

4K thermal blimp
-----------------
4000 cf volume
43 ft long
14 ft dia
3.1 finess ratio
52 lb lift @ 13 lb/1000 cf (200'F flying temp on 80'F day at sea level)
220 square yards 1.3 oz fabric

Weights
============
Gondola: 21.4 lb (9707 g) no fuel tanks
Envelope: 20.5 lb (9276 g)
Fins: 4.38 lb (1985 g)
Tail Fan: 2.18 lb (987 g) everything except battery
Tail Battery: 0.55 lb (197 g) 4S, 1.8 A/Hr
1 fuel tank: 1.87 lb (850 g) filled

Total Flying Weight w/2tanks: 52.6 lb (23852 g or 24 Kg)
Total Flying Time on battery limits: 20 min max

Batteries
============
2 2s 2.1 A/Hr pressure fans <- flight time limiting factor 18 to 20 min max
1 3s .8 A/Hr valves
1 4s 1.8 A/Hr tail fan
2 6s 4.9 A/Hr motors
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Old May 17, 2012, 12:03 AM
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I have both the burner problem and turning problem fixed now. The burner problem was an issue with nozzle geometry. The turning problem was fixed by switching to a new ESC, going to a larger battery and switching up to three blade props. Turning is very easy now.

Now I just have to learn how to fly this thing before posting another video. I have no RC flying experience so I'm still struggling with trying to manage three or four variables at once (throttle, turning, burner and keeping proper orientation relative to ground winds). Launch time from back of truck to airborne is still a 40 minute process. Other than getting a more powerful inflation fan, there's not much I can think of to speed that up.
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Old May 17, 2012, 04:32 AM
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hello you may use an inflatable castle bouncer blower, we use that to inflate our big envelopes

a 50 m3 envelope is filled in less than 8 min

you can find that on dealextreme or aliexpress.com
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Old May 17, 2012, 04:37 AM
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http://www.aliexpress.com/product-fm...olesalers.html
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