2.4m DIY Twin boom for Aerial Photography, Video, GIS, Photogrammetry

Hi Forum, I am a fairly new user to APM2 (made about 4 successful flights on a skywalker.) And I am looking at building a twin boom aircraft for taking Aerial Pics to be used for GIS, land surveying etc.. I initially built an off the shelf twin boom called the URSUS, but due to its wooden spa construction, it broke in half in mid air. I have added glue, carbon and ply reinforcements, but now its too heavy to fly. Therefore I thought i'd try and build something myself using its power system

Here are my objectives

  • Must be able to accommodate a roll gimbal (I made this for the URSUS)
  • Must fly for 45 + mins
  • Must be shower/rain proof
  • Must Fit in the back of a Volvo V50!
  • Must be able to fly slow or fairly fast into wind
  • Airframe without power system should weight less than 1.5kg (based on weights taken from other airframes in this size range)

Based on some research, I have discovered that aircraft in the 2.2 - 2.6m range can achieve this. I have a moderate amount of building experience, using polystyrene, depron. But have never tried to build anything that performs well. 

I am going to make the Fuse out of fiberglass, and the wings out of EPP. 

Some technical details...

Wings 

  • Wingspan - 2200mm
  • Chord - 250mm (giving an aspect ratio of 1:8.8 )
  • Profile - Clark Y (noticed a lot of these aircraft use a clark-y profile)

Fuselage

  • box section - 120mm x 120mm x 600mm (excluding nose cone and tail cone)
  • Booms - 51cm, From trailing edge of wing to start of vertical fin

Power System

  • Esc - Castle Creations Phoenix 45
  • Motor - Ultrafly F/18/10 1000KV Brushless motor (model number uf-mtr-f1810)
  • Prop - 10 x 7
  • Lipo - 2 x 5000mah 3s 11.1v

Some pics... there will be a nice cowl on front and back of fuselage, but i cant do that with my limited CAD skills! 

This thread and idea is a product of realizing that the lower end off-the-shelf airframes are not capable of what I want to achieve. I have reached that conclusion in my Arial Photography thread here.. The Skywalker is great, but can't fit a roll gimbal in it (I keep getting pictures at different angles). The Ursus is nice, but the construction is too weak for my needs. Whilst working on a new airframe, I will be continuing to use the overweight ursus to perfect my roll gimbal. However a new airframe is needed to get longer flight times. I quite like the medium priced hugin, but thats a little out of my price range right now. 

I can get EPP wing cores cut for £40, and a fiberglass fuse made for next to nothing.

I have a few questions - 

  1. What distance should there be between the booms?
  2. What is the best aspect ratio?
  3. What thickness should the carbon booms be?
  4. What height should the rudders be?
  5. Is it best to go with an inverted V or H tail?

If anyone with aerodynamic knowledge has any fairly simple calculations to see if this will work, please could you let me know! or any other thoughts for that matter, positive or negative!

Cheers

 

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Permalink Reply by Richard on July 19, 2012 at 6:38am

Hi Martin, that thought also went through my mind - But i am a bit impatient when it comes to this sort of thing. And I have already spent £30 on 4mm ply to make the wing boom joiner boxes. I've found an entry level scroll saw in b and q for £60 - i'll give it a try and if all goes well it will greatly improve my building time! My only dilemma now is do i go to screwfix or b and q!

Permalink Reply by Martin Poller on July 19, 2012 at 11:15am

Have you thought about a CNC machine, would it fit in the back of the car! LOL

Martin.

Permalink Reply by Jake Stew on July 19, 2012 at 2:23pm

I use a scroll saw.  But in any case you want to cut outside the line and sand down to it.  Don't try to cut it perfect right off the bat because you also want all the sections identical and it's easiest to get this by holding or clamping them together and then sanding them down together.

I use a belt sander on it's side.  I just lock the trigger running and sand down to the lines.  I usually cut the pieces then sand one down perfect, then hold them together and sand down to the perfect one.

I've also seen some people clamp all the wood together and then use a scroll saw or band saw to do them all at once, then sand them down.

Permalink Reply by Richard on July 20, 2012 at 8:19am

Hi Jake, i am only cutting a few wing caps from ply - hopefully the scroll saw will do a far better job than my coping saw - which goes inside and outside of the line! I bought a nice sanding block as well, not sure if i'll be able to fit a Bench top sander in the lounge! 

Hopefully it will cut 4mm ply without too much trouble

Permalink Reply by Jake Stew on July 20, 2012 at 8:30am

A scroll saw will rip through that with no problem.  For light stuff like this a spiral/circular blade will work also.  Regular blade is also fine, but will cut faster.

Permalink Reply by Richard on July 20, 2012 at 8:48am

I guess multi directional blade is what i need - not sure if they sell them in screwfix, which is where i am collecting the saw from this arvo, got this one in the end, it doesnt have vriable speed, but should be a good buy...

Permalink Reply by Jake Stew on July 20, 2012 at 4:45pm

Wow!  Nice saw.  Mine's just a little Delta I got from a pawn shop for $20.

A regular blade will work just fine, you just have to turn the wood as you go.  With a round blade you don't really have to turn the wood and just push it around whatever direction.

Permalink Reply by Richard on July 23, 2012 at 6:21am

I think i am gong to take it back - the blade seems to have about 5-7mm of sideways movement when the saw is on - It cuts fine, but hard to get it to bite on the line - going to get a replacement and see if it works any better - what do you expect for £70!

Permalink Reply by Wrongway on July 27, 2012 at 10:41am

Awsome Project Richard!

Keep us posted!  I want to build one too.

Thanks!

Permalink Reply by Richard on July 23, 2012 at 6:25am

Update - Alloy tubes cut, carbon tubes cut, wings test fitted, and nose shaped...Tail boom tubes upgraded to 16mm dia (not shown).

Next steps - complete wing/boom joiner boxes.

Permalink Reply by Richard on July 29, 2012 at 7:18am

Things are going well - wing joiner boxes are glued together and test fitted - the AUW is coming in at 3.2kg so far - it will go up though as i haven't covered wings yet, and that doesn't include the motor i will be using...

I am thinking about a parachute deployment mechanism .. does anyone know of anything like that being used on an airframe of this type?

Permalink Reply by Richard on August 6, 2012 at 1:07am

Quick update - Things are progressing well - The Tail is mid way through assembly, the booms are secured, just go to cover the tail, pick a power system, add landing gear & servos!

I'm going to cover it in bright orange solarfilm!

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