My Twin Boom UAV Construction Log

[Mark Harris]

I was starting to take over the Twin boom pusher thread, so i thought i'd start my own.

This is a 60% scale version of the UAV which i am designing. The entire aircraft is scratch built (as you can see from the progress) and is using plans which i have created. These plans will not be availiable, sorry.

This continues from where i left off here:
http://www.rcgroups.com/forums/showpost.php?p=7276684&postcount=80

I've got one wing's construction finished and all sanded down. The other wing is 70% constructed (needs support sections, servo mount and 2 more spars glue into place (already cut).

The right wing is starting to get covered :)

[Brandon Crash]

looking good mark!

What chord have you got on that wing?

Cheers Brandon

[Mark Harris]

Its about 270mm from memory. I think its possibly too big, the wing is very very wide haha.

[fritzdecat]

excellent
What I'm wondering is how do you mount a gas tank in a pusher so that it works? Backwards? or do you use a different style of tank?

[Mark Harris]

No idea.. this prototype will be powered by a 10 size electric motor.

[Mark Harris]

Got the wing fully covered.. only had a small amount of time today sadly.

Top is yellow :) Need to make the final spar plywood on full size.. if solarlite screws up the spar, solarfilm is going to bust it apart completely.

No pictures, just re-installed windows.

[RaptorAP]

excellent
What I'm wondering is how do you mount a gas tank in a pusher so that it works? Backwards? or do you use a different style of tank?

Backwards. That way when the nose pitches on takeoff the fuel runs toward the clunk, a few extra inches of fuel line work okay, Ive installed a header tank from a Raptor heli inline between the tank and engine works with the tank backwards too.
Mike

[Mark Harris]

Managed to spend a bit of time on sunday working on the plane. Wing are all done, just need ailerons and the top covering on the left wing.

[Mark Harris]

All covered. Wings complete sans ailerons.

[Connexxion]

Looks neat Mark!

Can't wait till this bird takes off.

[Mark Harris]

Just ordered a pusher prop for it, had to get it from a USA site as i couldnt find one in australia. Sigh. Work on the fuselage starts on wednesday or thursday. Alot of that may be planning rather than building though.

[CAFplanekid]

Not sure if you are aware, but for electric motors, a 'pusher' prop is not needed. Just reverse the direction of the motor (for brushless, switch any two wires, for brushed, switch both). We have a bunch of APC 'Pusher' 9x6 electric props, and they are exactly the same as the regular 9x6, just reversed.


Cool plane, looking forward to seeing it come together :)

[Mark Harris]

Thanks for the advice CAF, oh well. I've got a APC 10x6 ordered though so i guess we will see :).

The full size petrol will need to have a pusher though :)

[Crash Pilot]

Mark

Your progress is looking really good. I hope to start my scratch build soon now that I have returned from holidays.


Crash Pilot

[Mark Harris]

Cool Stuff, i ended up playing with rocket planes today rather than working on the fuselage. Didnt have any plywood the right size :(

[Mark Harris]

Ok so got a bit of work in on the plane today. Fuselage sides all made, all cut for the structural supports, boom holders cut and in place.

Took a really long time to make the boom holders. Booms fit in REALLY tightly though so it was worth spending so long on it.

Booms get bolted in place with 3x16mm screws, once unbolted the booms can slide all the way to the front of the plane, just enough sticks out the back for the tail to sit on. This means hopefully it shouldbe pretty transportable.

Motor will end up getting mounted on ~2.5 degree downward angle which hopefully will help level flight at low power.

The whole thing looks like it will end up at approx 1700gsm when complete. My motor with 10x6" prop gives about 2.2kg of thrust at full power (36amps) so we should be laughing :D

[Connexxion]

Hi Mark,

Looks good and sounds nice.Keep us posted,we're watching you :eek: .


Connexxion

[Mark Harris]

I went and got the last of the balsa, bolts screws, wheels, landing gear, clevis', pushrods, hinges, control horns, etc that i need to finish it off from work today.

Got the fuselage all glued together with the fingered pieces. very nice and strong :)

Put in the wheels to test position and fit. Sadly i think the font wheel is going to be too far forwards for a camera mount on the front underside.

Have to do some filing on the boom mounts, they are not quite straight when bolted in place, one is slightly higher than the other. This is just because of 3 out of 10 mount pieces being slightly off and causing one boom to sit downwards and the other upwards. Easy enough to fix.

Its starting to look pretty sexy IMO :) I really like the pattern on the hubs of the ultra cheapy wheels at the back. They only weigh 8g each so i may bump them up to larger wheels. The mounts are for 40 size aircraft and i'm hoping this will work on a 10 size brushless outrunner @ 11.1v with a 10x6 prop. I'm certain i'll need to take bigger wheels with me for testing flights as the ground at our friends farm is pretty "unflat".

[Connexxion]

Where is YOUR cat?

Almost every uav-er seems to have a cat. :D

[Mark Harris]

I hate cats. I have a dog :D

[clolson]

My dog is an integral component in my autoland and retreival system! Just got to tape over the teeth marks before the next flight ...

[Unterhausen]

Not sure if you are aware, but for electric motors, a 'pusher' prop is not needed. Just reverse the direction of the motor (for brushless, switch any two wires, for brushed, switch both).
I saw some reversed electric props online somewhere. I thought about using one just to be contrary. I guess you need them for contra-rotating props.

I like the idea of this plane. What I've found using a Sig Kadet is that people don't respect it because it looks like a model airplane. Thinking about building a twin boom with as little effort as possible, I have way too much to do at work.

[RaptorAP]

If you dont install the factory decals on the LT40 especially the windows, it resembles a UAV more. I run my electric tractor props reversed on my pushers, they are mounted and turn just as they were in tractor configuration.

[rcdoma]

If you dont install the factory decals on the LT40 especially the windows, it resembles a UAV more. I run my electric tractor props reversed on my pushers, they are mounted and turn just as they were in tractor configuration.

I am a newbie lurker who just got into electrics and pushers. I thought it would be fine to simply reverse the rotation of the motor with a tractor prop, but was told to reverse the prop such that the leading edge of the prop is thicker than the trailing edge.

[HELModels]

Yeah, you want to make sure the fat edge of the prop hits the airstream first.

Cats are cool, but try taming 2 ferals. Their cool but quirky. They have rules of engagement, zones of security, handling protocols, feeding protocols, etc. Interesting creatures to say the least, not unlike people in many ways. Violate the terms and they bolt. It took 5 years of negotiation. I felt like I should have taped it and sent it to the discovery channel. They could have called the series "Man meets Cat".

This week our resident fool tries to pet the deadly pygmy panther and his efforts are rebuffed with teeth, spitting and raised paw. Will he remain undaunted and unthwarted in his quest to tame this angry little beast.

[RCWorks]

Now I don't feel odd, I have a bird and a mouse... no cats here either.
The bird is my consultant (Hold them wings out for another measurment) and the mouse is my test pilot. (Fastest mouse in California! Try an catch him pre-flight!)

Plane looks good, I am still working up my small version (24"), then refine it at 48 inches. with the final at 84 inches. I am hoping to go electic on the big one, I have grown accustomed to no fuel residue and I think it is easier on the electronics.

[Crash9]

Looking good Mark, lots of progress. Your garage looks like mine during project time :D .

[Mark Harris]

I think you can see about 4 different projects in there lol. I had to move my car out to make room. On the other side of the other car there is a 3m x 12m area for R/C build too (benchs, vices, other power tools i havent relocated and more wood/cf/metal storage) etc. My garage is a total mess, but i know exactly where everything is, so do my friends haha.

Ok so no progress updates.. been working really really hard on the OSD so havent had a chance to even think about the UAV.

I've got an OS-46LA for this, its going to be too heavy for the 10 size electric. Putting $500AU into a new motor/batteries/speedie just for a few test flights seems silly. So $98AU for the motor and fuel tank!

Pusher Props:
On electric not so much a problem, just reverse the motor. Cant do that on nitro though hehe. Going to go with a 9x6 instead of the 10x6, scared the vibration of the motor may be just enough to make it dip down to the boom and that would be pretty fatal. That extra clearance is just peace of mind.

[Crash9]

Speaking about OSDs, How's the new one coming?

[Mark Harris]

Beta units went out yesterday, more going out today.

[Mark Harris]

Okey so i spent some more time on the prototype today :)

- Ailerons built, covered, attached.
- Wing servos in
- Motor attached/Tested.. need to finish fuselage before testing further. Fueselage goes like jelly
- Proper wheel mounts on, still need to finish up though.
- Steering all done

Still to do....
- Tail section
- Inner part of fuselage (for radio gear/batteries to sit on.).. must make it more rigid, whole thing goes to jelly when the motor is at 20-35% thrust.
- Fuselage covered
- Test Fly!

[Crash9]

Good progress Mark, it looks like it's coming together nicely :) .

[RaptorAP]

Hey Mark you might want to consider turning your tank around, if its mounted level when you take off or go nose high the clunk will be in the air inside the tank and itll quit. It looks like you could run another 6 inches of fuel line to turn it around.

Heres a pic from my Grey Ghost RPV, its mounted with the clunk to the rear, works good:

[RaptorAP]

Also Mark it looks like you need a solid floor in the fuse, I use as thick a balsa sheet I can get, itll help strengthen and keep everything together.

[Mark Harris]

Thanks for the tip on the fuel tank, its a pretty tight fit and that was the only way around i could get it. I may have to go get a smaller tank to fit it around the other way.

I ahvent finished the fuselage, there is going to be a plywood deck in there with arching of sorts underneath it to support it. It should end up very rigid and strong.

I'm trying to not cover the bottom of the plane with anything solid so i can mount cameras or other sensors there easily.

[kd7ost]

RaptorAP is right.

The clunk still needs to go where the flight forces are going to make it go. To the rear. It's looking good.

Dan

[RaptorAP]

I must give credit where its due though. I learned that trick from Dave Jones at AUAV, he definitely knows pusher airplanes! You can possibly position the tank at a 45 degree angle with the clunk forward, that way when you climbout the tank will be level, Dave showed me that on one of his prototypes. Thats an alternative if you cant mount the tank with the clunk to the rear.

[Mark Harris]

With a bit of cutting and re-arranging i've managed to swtich the tank around the other way :)

I have the CF support/brace rods for one wing attached, gotta do the other. Makes the wing far more rigid and less prone to flapping about when i tap the UAV hehe.

[Mark Harris]

well... no working on the uav for another 10 days :(

just got back from the hospital... 5 stitches. I gotta be more careful.

[Connexxion]

Sounds painfull.What happened?

No pic's of the wound? :D

[kd7ost]

Ouch Mark,

Where did you slice yourself?

Dan

[Mark Harris]

I use really sharp blades, so it didnt hurt in the slightest :) the doctor was really impressed with how neat the cut was hahahha.

Cut about 2cm long down the outside of my thumb. Spread open about 5mm once i cut, could see the bone. was pretty cool.