Internal Ducting in a Delta Airship

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hiflier

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Dec 18, 2014
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Did some quick calculations on the model's dimensions. I'm not that encouraged. Too much weight. I can get a thruster at around 4oz. that has a roughly 5 lb thrust but it's overkill by a long shot. Thinking of going to a blower cage type propulsion as an option.......AND lighter skin material. Robbing a counter rotating blade set up from an RC helicopter is something I'm looking into for weight reduction purposes. I have a Blade MCX RC and the whole thing weighs only an OUNCE! It developes around 23 gms of total thrust. Not nearly enough considering the total CFM I may require. In the larger picture I'm a bit hazy but more thrust potential is better than maxed out all the time IMO.

This is getting into an area that I knew I'd eventually have to deal with HVAC. After all, if it's going to be a true LTA then using HVAC specs may in the end be the way to attack the issue. The balance of weight-to lift-to vector kind of puts me on the airship drawing board. I'm too stubborn to give up on the design though. Mainly because there is NOTHING out there that even comes close to this idea. It's been 4 years on my mind and two years researching the possibility. I'm on the verge of now jumping in and building this starting Jan 2015- about two weeks from now. Time to either go to work or get out of the kitchen and walk away.

Going to work will be better.
 

hiflier

Active Member
Joined
Dec 18, 2014
Messages
37
Location
Old Orchard Beach, Maine USA
Did some quick calculations on the model's dimensions. I'm not that encouraged. Too much weight. I can get a thruster at around 4oz. that has a roughly 5 lb thrust but it's overkill by a long shot. Thinking of going to a blower cage type propulsion as an option.......AND lighter skin material. Robbing a counter rotating blade set up from an RC helicopter is something I'm looking into for weight reduction purposes. I have a Blade MCX RC and the whole thing weighs only an OUNCE! It developes around 35 gms of total thrust. Not nearly enough considering the total CFM I may require. In the larger picture I'm a bit hazy but more thrust potential is better than maxed out all the time IMO.

This is getting into an area that I knew I'd eventually have to deal with- HVAC. After all, if it's going to be a true LTA then using HVAC specs may in the end be the way to attack the issue. The balance of weight-to lift-to vector kind of puts me on the airship drawing board. I'm too stubborn to give up on the design though. Mainly because there is NOTHING out there that even comes close to this idea. It's been 4 years on my mind and two years researching the possibility. I'm on the verge of now jumping in and building this starting Jan 2015- about two weeks from now. Time to either go to work or get out of the kitchen and walk away.

Going to work will be better.
 

hiflier

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Old Orchard Beach, Maine USA
I've located a local source actually for 1/8th inch matt board but a mylar skin might make more sense now that you mention it. Depends on the look I'm after as well as the weight considerations. I now have an internet source for a counter rotating blade/motor system that will produce about 4 lbs of thrust. next will be securing mylar sheeting of course even if it's not for the exterior. It's for at least making the custom ballonet(s). I have a source already for the better high grade helium that welders use.

Expensive? Yep. I see throwing about $200 or more at this and that's only if I don't blow it by loosing all the helium because of a leak in the shakedown cruise. Air testing will be job one ;) Hope to get going on the shell and ducting in the next three weeks. I think hanging the components from a spring scale will nail down the weight parameters before making the ballonets. Could mean a change in height from 1 foot to something more. As it is the volume is only 17.5 cubic @ 1oz. of lift per cu. ft. Might like to get that to around 24 cu. ft. or better. Rounding the nose would also increase volume.
 

bmcj

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Hiflier... not quite the track you want to be on, but I think there might be a possible market for a personal sized (4-6 seat) version of your craft or similar.


We obtained Gov't. surplus weather balloons locally, cheaply. Few years later, knowing we used Natural Gas as home fuel, and that a capped valve was available in the basement, I filled one to about 4', noting 2 things: lots of lift, and lots of GAS permeating the pores! Right away I envisioned a static spark, and I would be history!
LOL, we used a gas mix of oxygen and acetylene from a welding setup (smaller balloons). Fill them up, tie on a crepe paper ribbon, light the ribbon and let the balloon go. It would float away, to be followed by a big flash-bang. One of my cohorts found out that static electricity (from the balloon rubbing against blue jeans) could set them off... no injuries, except for some missing (singed) eyebrows and several days of deafness (tinitis overload).
 

hiflier

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Ah yes, LOL, the singed eyebrows. More than a few of us have been down that road. It's a wonder there are any Darwin awards left to give out for Pete's sake. And yeah, not a route I'd take although the gas mix was something I didn't know about. It's these kinds of stories that teach those who might give such move a try reason to pause. A good thing IMO. At least the neighbors weren't picking toothpicks out of their pets.:shock:

The inherent difficulties associated with this design are many. A stealth look and sound is the goal. The smaller individual goals aimed at getting there each have their own set of problems to solve as you can imagine. Someone I know mentioned using a quad copter set up for better control of pitch and yaw. That's fine but it presents it's own complete set of hurdles for arriving at the ultimate end product. One upper surface intake (4?) and 4 ducts. Now how does that happen? I think one central power plant with ducted thrusters for direction is the simpler approach........minus the oxygen and acetylene mixture of course.......I'm still chuckling over THAT visual. Glad everyone was OK though.
 

FritzW

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We did the same thing with hydrgen made in a glass coke bottle with lye, aluminum foil and a little water. Fill up a ballon, tape on a toilet paper "fuse", light it, and let it go at the drive in movie theater. ...ah, those were the days.

On the model, what about a light frame made out of Balsa or Bass sticks with a little very light ply where needed, Cover it with something light like mylar or silkspan (it wouldn't have to be airtight). Then make the gas cells out of something like dry cleaning bags?
 

hiflier

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Hi FritzW, just got off being 30 minutes on the stupor-net trying to at least find out about the permeability of dry cleaning bags. I finally gave up typing in every description as I watched google completely ignore and dance around the subject of helium in dry cleaning bags as well as any inquiries on permeability. Folks here at home wonder why it takes me so long to research stuff. Of course my friends say if I was normal and researched normal stuff I'd save an enormous amount of time but I ask you....where's the fun in that? I'll bet I could find Justin Bieber's newest tattoo in about .005 nanoseconds though, eh?. Uh....sorry....rant over.
 

FritzW

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... I'll bet I could find Justin Bieber's newest tattoo in about .005 nanoseconds though, eh?. Uh....sorry....rant over.
LOL Sad but true.

Those big honking mylar "happy birthday" balloons might do the trick. They're cheap and light. If they were only half full they would conform to odd shaped interior spaces. They hold helium really well, especially if they're only partially filled (not under pressure).
 

hiflier

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That was my thinking too actually in customizing mylar into an oversized pie wedge that wouldn't have to be fully inflated. You know, make it an inch bigger all the way around to allow for nesting around structures and such as you say. When I see the top and bottom of the shell begin to bulge slightly then stop filling. There should be lots of slack in the ballonet at that point which will reduce the chance of stressing a seam.
 

hiflier

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Gotta add here, you have a good problem solving aptitude. Thanks for sticking with this. I've been keeping a list of folks so that credit is given where credit is due. There are three others that are local store owners that have been very helpful as well; mostly for leads and sources for materials. I forget no one as I claw my way to stardom LOL.
 

etard

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It's a heck of lot of fun trying to figure out how to make things work.

I wish more folks had this attitude, it's much easier to come up with reasons why it won't work. Shame, that is.

This thread needs at the very least a napkin sketch of what you are proposing. I still don't know if your ship will look more like a stingray or maybe one of these:

marine_2_lg.jpg
 

hiflier

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Old Orchard Beach, Maine USA
I agree on the attitude thing but I think many here DO have the right frame of mind in the way of solving problems with flight. Oh, BTW, I have a couple of images on page 2 post #21 if that helps. Thanks for the comments.
 

bmcj

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I agree on the attitude thing but I think many here DO have the right frame of mind in the way of solving problems with flight. Oh, BTW, I have a couple of images on page 2 post #21 if that helps. Thanks for the comments.
Looking at that, I'd have to say that you are placing yourself at a disadvantage. A sphere holds the highest volume for a given surface area... your very thin profile with long pointy corners is going to require a lot more heavy envelope material than is needed. Go look at some of the more rounded or bulbous shapes from the NASA lifting bodies for inspiration. You can gain a lot more gas volume with a lot less structure weight, and still have a shape that provides aerodynamic lift. Rounder inflated shapes are also more self-supporting, requiring less support structure inside.

Look here, too: Dynalifter International | The Next Generation of Air Transportation
 

hiflier

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Old Orchard Beach, Maine USA
Hey, the last coupla posts are on the money for shape. I've been all over Dynair inside and out for quite a while with schematics on my computer since around late 2011 or so. The rendition on the "tarmac" was simply to give an idea for the configuration of the craft. It's waaaay too thin as shown to have it work. It was only for shape illustration. Being black doesn't mean it can float LOL. I've decided on some better materials as it is. After the wedge-shaped bag is fabricated inside a light wire frame for holding shape the skin will be 1/8 inch charcoal packing foam. Light as a feather and easy to cut and work with.

I think just doing that will drop the weight by at least 2 pounds! The same material with dry cleaning bag material lining the inside can be used for ducting as long as the ballonet doesn't occlude the air passages when inflated. I foresee the ducts as being triangular shaped chases instead of any other design so adding angled strips down the fuselage will be all that's needed.

Could be time to show some stuff I've collected over the last several years about internal (tunnel) propulsion? Maybe not, but I've not seen the real world application to an airship in anything really- blimp, dirigible, or otherwise- rigid or not...........I'm hopelessly hooked on this concept.
 
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dirk_D

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Sep 22, 2010
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Victoria, Australia.
I was looking at the d y s o n brand fan recently thought it would make a cool airship shaped like a tube, an airfoil lathed in section.
Patents are recent, you'd have to pay royalties though.
 

Sockmonkey

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I have a notion. One could mount thrust ducts on the outside of the gasbag without much weight if they were of the fabric type used in ram-air parachutes. In addition to thrust, they might be made to function like a combination of blown slots and fluidic control structures. Below is a crude representation of the idea. Half of them only reach partway back to show that they would be over several different areas to control airflow at various points for steering and thrust.
 

bmcj

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I have a notion. One could mount thrust ducts on the outside of the gasbag without much weight if they were of the fabric type used in ram-air parachutes. In addition to thrust, they might be made to function like a combination of blown slots and fluidic control structures. Below is a crude representation of the idea. Half of them only reach partway back to show that they would be over several different areas to control airflow at various points for steering and thrust.
Thanks. With a picture, it makes more sense. My biggest concern is that you will have duct loss due to the drag in the long ducts, effectively eating away at the power for whatever provides your thrusting air. I think that open props provide you the best efficiency, and distributed, vectorable thrusters (props) would give you the same maneuverability without the duct loss.
 
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