20 Foot blunt nosed Kraken - How would you do it?

[Pie]

I'm considering building a 20 foot blunt nosed Kraken (or at least Kraken like).

I've built a 10 foot blunt nosed Kraken already (and several "smaller" ones). I've attached pics of the 10 footer.


My thoughts -
Must be able to be transported in a mini-van. I'd like to take it to Flitefest 2016. I'm thinking three pieces (middle section and one wing on each side. About 7 feet per section.

I was planning on using these servos:

2 servos per elevon.
Re-inforce the servos in the foam

2 motors - counter rotating.
2 speed controls and batteries.
LED Lights in the wing - connectors for when the wing is taken apart.
Separate 3S system for lighting/accessories.
Under 55 pounds (FAA).
extend the wing tips to get to 20 feet (slightly cheating... but it's still 20 feet.)
differential thrust
Try to keep it light,
CG must be right.
Test fly somewhere local with a longer grass patch.
main spar (vertical aluminum/foam sandwich, maybe ply) not sure how to do the joining of the wings...
Use some carbon fiber (I have a couple of 40" carbon fiber square tubes).
very very very light spray paint for visibility/orientation. Although i'm guessing a 20 foot plane doesn't disappear easily.
Take pictures during the build.


My major questions:
What motors? I'm not sure how big to go (Anyone know what motors are in Peter's huge Guinea?) Can I just run 4 motors like this http://www.hobbyking.com/hobbyking/store/__15201__HobbyKing_Donkey_ST4010_820kv_Brushless_Motor.html
Prop?
ESC and Battery to match (target 5-10min flight time)
Wheels? I'm not sure how to do the wheels, They would be heavy, what size "wire"? what is the lightest option?
Should I run a separate 5V system for the servos? - I've never done this, but I think it would be wise considering the servos.
How thick do you think the wing should be in the middle? How wide? (i usually just start cutting without much layout).
I'm not sure how to do the main spar.... I know the middle must be rigid, but i'm thinking a little flex toward the wing tips will be ok. Anyone know how they built the spar for the Giant Cri Cri at Flitefest 2015?
Is there anything else I need to worry about?

Let me know what you think. I'm planning on getting started soon.

 

[Electric Mike]

Pie,

I'm too new at scratch builds to really help you on this one, but WOW your 10 foot Kraken looks amazing! Can't wait to see what you do for the biggee. Pls post lots of photos!

Mike

 

[TheIvarine]

if you are not planning to go inverted or put too much stress on the airframe you could take hinges and have the wings fold up into each other and secure the top wing portion with tape and hot glue, also zip ties and balsa reinforcement would do the trick.

 

[HilldaFlyer]

For the spars - I would suggest some non-flitetest techniques.

Carbon fiber and fiberglass will get you the strength you need - see Balanced Pusher Wing for instructions.

Also, Willsonman is making them with foam core and heavy fiberglass

For the motors - if you liked the performance of the 10' - then double the watts of the motors. Should fly!

 

[AkimboGlueGuns]

Very carefully.


I'd definitely use a beefed up box spar at a minimum. I think carbon would be a much better option though, more rigidity less weight.