Lifting Body Aerodynamics, designing

Hi SmallBlimpers!  I've done a 7-foot frame-study model of my UltraLight [UL] SkyBoat "Marvin" and I like the looks of it enough to cover it and take it out in the wind.
    Now I have a basis for calculating the frame-weight of my lifting body, [LB], design. The frame is the major obstacle in designing an airship that weighs less than 254 pounds for qualifying as an FAA UL type aircraft. Granted, the propulsion system is the major weight component but that's easy to solve, just go with smaller generator/motors. The frame comes first. Without a frame there is no dirigible, just a floppy blimp. 

    the Wright Brothers built their own wind tunnel to test their aerodynamics and they still put the tail on the wrong end  ;-]   So maybe it's not the greatest, or only,  way to design something cool.

 Is wind tunneling the only way to test the lift and drag of an LB  design?

Swampie posted a method that senses deceleration to calculate drag. You could do it like Burt Rutan used to do, strap it to a pickup truck and test it while driving. 

http://smallblimps.lefora.com/2010/03/19/drag-estimation/4/

This method was used out west where you have long desert highways for miles.

Two things:

Winds can't be controlled. Outside of a wind tunnel, any vagrant wind could screw up a data run.

The original tests by the Wright brothers was based on mounting a wheel laying down on top of an axle attached to the handle bars. They found out it's hard to steer a bicycle and take data at the same time.

Well OK three things,

The aerodynamics of the car / truck interfere with the aerodynamics of your model. If you mount it on a long enough spike to separate the two, then you have to take the spike flexibility back out. And you have to explain to the state troopers what in the crap you're doing on their road with that dopey thing on your car / truck.

This guy sells lifting body kite/balloons which are awesome designs for a man-lifter, I believe.

http://www.allsopphelikites.com/?gclid=CN2FqfKFkaECFcNX2godzl4fNw

I think his max aerostatic load is 30 Kg. The average USA beer gut is over 90 Kg.

Nav;

Is this the relative proportion of your skyship?

Attachment: navigaiters_ship_top_view.bmp (900.0KB)

Attachment: navigaiters_ship_side_view.bmp (900.0KB)

Attachment: Navs_airship 150.txt (0.0KB)

So how about:

Attachment: Navs_airship.txt (0.0KB)

Attachment: navigaiters_ship_side_view_2.bmp (900.0KB)

Attachment: navigaiters_ship_top_view_2.bmp (900.0KB)

If you convert from bmp to jpg:

There's just three lines in the file:

   half_diagonal_1   3.4
   Total_area        182.624
   Total_volume      157.216

In a past post, Nav stated that he wanted a 150 M^3 ship.
This calculation shows the surface area for estimating the envelope weight.

This is also a POV-RAY example for making a 3D model to get some preliminary
numbers. The 3D model can be added to, to show how everything fits.

BTW, POV-RAY is free! just download from pov-ray.org

Very interesting images. I'll have to try that program out. 

Everything is better when your see it in 3D isn't it..

Yes.

If you want to put in 3D scale models, then you can see if your feet are sticking out the bottom of the gondola when you put the seat at the correct center of gravity place.

Notes about POV-RAY:

It uses a left hand coordinate system - not a big problem - just be SIGN careful when you use trig functions in 3D

It comes with copious examples - easy to get started quickly.

Most of the people who use it in contests are ARTISTS. Interesting people, but they use the other side of the brain, don't get in an argument with them, you'll just waste time getting an artistic answer to an engineering question.

If you e-mail POV-RAY: they're in Australia. Every e-mail costs them money because of the way their phone/email system works. If you ask them a question that is plainly in the documentation or their forum- they won't like it!

Outside of the above, it is the most comprehensive free program I've seen in all of my engineering years. It is a perfect Math laboratory and a great way to illustrate complex ideas. Even with animation.

this video from Berlin shows a lifting body blimp using aero lift to compensate for the H2 lift being at 85% of gross weight.

   This looks like Dude's type of design. It has a thin trailing edge with elevator flaps mounted. Looks EZ to make and scalable to an UL man-carryer.

   Looks like he sewed some baffles lengthwize to make the width bigger than the height, ie to flatten the envelope down..

I like that video. I wonder how he got that shape? How would you sew it and keep each side of the envelope a set distance apart? 

I'll bet he did baffles.

Or an internal frame. that's what I am designing. But it does look like he did several lengthwise baffles.

Which is the cheapest most light weight way of controlling shape. IF you extend the baffles to outside the skin on the bottom you wind up with attach points for other equipment.

I'm  wondering  just  how much  gas lift we  really need now .  Maybe  just  a little more than to  hold  the  envelope weight up ....???   I'm  a  avid paraglider  fan ,  and   the  wing is  small  in comparison to  a airship  but  the lift generated  is  quite enough  for lifting   man  and motor  and  even  trike  frame ...with ease  at  slow  speeds . I mean  , if you  can  launch  at  running  speeds   , thats slow wouldn't you say ? . 
  With this in mind,  What if  we think on  a small envelope  shape, like shown only  refined and big enough  to  do  the job  better  , that  uses paraglider wing  halves on  each  side .   The pilot is  still suspended in pendulum effect , only  now  with  the paraglider wings  He has full control  of  the ship for turns,  speed up  to climb,  and slow down to descend.  The problems of  adjustable buoyancy go  away , a lot of the lift gas expense goes away ,and we gain  a grate deal of control over the ship .  
  There is  a flight maneuver in paraglider flying called  pulling big  ears .  This is when  you  pull  lines to fold  the wing tips up and  fly  with just  the  center of the canopy . Its used for  descending  faster. With  a correctly  shaped envelope  as  the center body and doing  a  big ears maneuver could  let you  fly  the lift  envelope body alone, basically  folding up  the  wings , and possibly let  you fly  faster being  on  a  sleek  aerodynamic  pressurized  airfoil and retain  some control  with  weight shift for turns  . Like the Whoopee  flyer inflatable wing  in a way.  When you  re-deploy  the paraglider wings ,  you  slow down  but  regain  the  slow speed control for precision low  and slow flying and landings .