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Permalink Reply by Jon Cherba on November 20, 2011 at 8:13am

Nobody....

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Permalink Reply by Skydog222 on April 26, 2012 at 9:00pm

Hey Jon, 

 

A couple of simple observations I have from reading through your post.  (I have not run any performance numbers, these were just the things that I thought about while reading your post)

 

Mission:

First, what is/are the mission(s) you are designing this a/c to complete?  That is the main driving factor in aircraft configuration.  I see you listed HD or photography, but that is just a small part of defining the mission.  

 - How fast do you want it to fly? <--- major question that needs to be answered…I made a lot of assumptions around this one. 

 - How long do you want it to fly?

 - What are you videoing and where will it be relative to the aircraft? (you have some options listed, but you need to define the mission of the aircraft and then configure it to complete that/those mission(s). 

     - nadir?

     - side looking?

     - out the nose?

 - How fast/slow do you want to TO/land?

 - How do you want it to handle in the air?  (you had mentioned slow flying in your text)

 

Airfoil selection: (assumption: you want a slow flying plane)

Why did you choose this airfoil?  One thing I will caution you on is the extremely thin trailing edge.  That is going to be difficult to properly build.  Also, this would not be my fist pick for a slow flying plane.  I would be looking for something more like an SD7062 or something along those lines for a slow flyer (http://www.worldofkrauss.com/foils/1360).  Or you can always get away with a generic flat bottom airfoil of some sort for this size a/c.  It does not have to be that complicated.      

 

Wing Planform:

The tapered wing does look pretty cool, but if you are going for a slower flying aircraft, might not be the best choice.  The Hershey bar wing does not look as cool, but has the slow flying and STOL characteristics you seem to be looking for. 

 

Wing Details:

If you are going for a loitering slow flyer AP platform, I would suggest adding some dihedral to your wing (2-5 degrees).  This will add to the stability in the air.  I would still stick with having ailerons on the wings.  If you are looking for short field TO/landing, I would suggest some flaps, but they are not required. 

 

Side View Wing Position:

Where do you have your wing positioned relative to the fuselage and booms? Top?  Bottom?  Middle?  Again, for a more stable slower flying platform, the high wing configuration matches that mission more than the other two configurations. 

 

Fuselage Position:

Looking at you top view drawing, it look like you are going to need to extend the forward part of your fuselage to help make your CG end up in a reasonable location.  Built as you have it drawn, it would always have an aft CG without a lot of lead in the nose. 

 

Retracts:

Do you need them?  They do add to the coolness factor, but it another system that you might not want to deal with.  What is the reason to use retractable landing gear on a slow flyer?

 

I hope this helps a little.  I don’t want to discourage you, keep working at it and refining your idea until your come up with something that YOU like and performs the mission that you select.  Good luck!

 

-Skydog222   

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Permalink Reply by Jon Cherba on May 8, 2012 at 6:50pm

Sorry it took awhile to respond...I have been working on alot of homework and looking for a job. I have basically stopped working on this project because I don't have the software for design phase of the project. Honestly if I could get someone to help me with the design and if I could get either the wood or G10 parts cut I would probably jump back on this project. I have tried cutting the ribs by hand and it just didn't turn out to be as high of quality as I'm looking for. I have some wood and a 4' x 8' sheet of foam that is just waiting to get used. I really wish I could get a team together to work on this project with me. Thanks for the reply, I will try and sit down sometime this week to go over your questions and the info I have and answer the questions you have asked. Thanks again.

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Permalink Reply by Edward Strickland on June 4, 2012 at 1:13am

Jon I am in the process of releasing a cheap airframe design for free. It should be in the region of £5 for fuselage and £45 for a custom built wing. I have built a few large VTOL uav's but feel that there isn't a simple cheap and effective design available. The design I have is based around a 4" tube. I will dig an old photo out, of the machine from 2008. Have a look at my site on diydrones. I think maybe a simple cheap airframe would be a good starter.
Eddie

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Permalink Reply by Edward Strickland on June 4, 2012 at 2:42am

Jon I think I was having a bad day, Ive just looked at the BOM I had from 2008 the costs were as follows;

PART NUMBER Weight QTY. Total weight (gms) Price
Batteries 185 4 740   £95.00    
Electric Motor 126.94 2 253.88   £333   12.19 kgs thrust  
Receiver  3.9 1 3.9   £39.00    
Rear Fuse 680 1 680   £14.69 www.publicmissiles.com  
Fuse Plug 52.82 2 113   £5.00 www.publicmissiles.com  
Wing   1250 1 1250   £45.00     
Tail  111 1 111   £5.00 ply    
Elevator 221.6 1 221.6   £5.00 ply    
    3373.38   £74.69        
    3.37 kgs       
 without motor, reciever and batteries the basic cost is £74.69    
 wing costs are dependant on who builds it/yourself/outsourced

 

I had another design which is cheaper still BUT not as large an airframe. You can see though that the use of "rocket" airframes does produce a volumous airframe at low prices.

Hope this helps

 

Ed

Attachments:

• BOM CHEAP UAV.xlsx, 31 KB

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