Bobcat (ish) long range plane

[Kai-003]

Hello everybody, if you are like me, you go to the flying field, fly, charge up batteries, and fly again. But the problem is my flights are generally about 4 minutes max, so to help fill in the time, I designed a plane that could ideally fly for a while, preferably until the next battery is charged. I designed the plane to carry a lot of weight, and to be really efficient. With school finally over I can start putting in more effort and time into my projects, so if you want me to post updates as I build, I could do that, or I could wait until the maiden, just let me know whats best. Of course from the pictures, you can see all the imperfections which i didnt bother fixing due to me being unsure if the plane would fly, but i plan to fix it. Enough talking tho, so heres the design.

here is a video, but try to ignore my dads terrible video skills:

the wingtips are angled 10 degrees upwards to help stabilize it, but I dont think its needed. In terms of flight time (its main purpose), I got 5 minutes from a 4s 3000mah, and after landing and checking the battery, to my suprise, I found it was at 70% still. I could probably get 15 minutes with one battery, and 30 minutes with two, but personally, 15 is enough for me. It uses the motor from the ft power pack F, and 5 servos. I'm working on landing gear for easier launching. It is 41" wingspan, and 46" long. If enough people are interested, I will get some pfd plans for yall to make your own.

In terms of flight characteristics, it's very easy to fly, with no flaps or airbrake (which could probably be added if wanted). Its not meant to be an aerobatic plane, but it certainly is capable of some. I think it would also make a nice fpv plane, as there is no prop obstructing the view. I think it would also be able to be converted to a vtol failry easily, but I have enough projects as of now. That is for a future idea. I also had an idea to put a (*spicy*) edf on it, but I'm out of money. Thanks for reading, and leave any questions below.

 

[John (ACEPILOT109)]

very cool aircraft!

 

[quorneng]

Kai-003
I had similar thoughts when I flew my first RC plane. It flew well enough but the duration was short, 5 minutes max and that was with careful throttle management so I decided to do better.
For practicality I also retained a pusher arrangement but I know enough about aerodynamic to realise that duration was primarily a weight issue and power consumption was proportional to speed, so it had to have a generous wing area, be as light as possible and still have good aerodynamic efficiency.
It took some development, testing and time to arrive at a 'good' solution but ended with the 'Endurance II'.

It uses a 5000 mAh 2s with a 100W Blue Wonder 1200 kV out runner turning an 8x4.7 prop. It weighs 436 g (15.4 oz).
It can maintain height (just) throttled right back so it is drawing just 1A. At that power level (8W/lb!) even the radio and servo consumption becomes significant but it has a theoretical endurance of 5 hours.
My longest ever continuous powered flight was 2 hours and a minute but it was me that gave up not the battery.

 

[BayDesigns]

This is interesting... I've been looking for long range ideas and I'm working on a pusher high-wing t-tail in my CAD program. Planning on building that since it's a testbed for a low-cost portable SAR/LE aircraft. That Endurance II looks really interesting... a lighter model like that could be a lot of fun for just seeing how far I can go. If I can get around to it this summer, that'll be on the list.

 

[quorneng]

To be fair the Endurance was specifically designed not to go anywhere fast with its very slow flying speed.
For distance the equation would alter slightly favouring aerodynamic efficiency (a thinner low drag wing section with a higher aspect ratio and a slightly smaller higher pitch prop) but it would require a bit more power at the cost of a reduced duration.
Above a certain speed the pusher/wing pylon configuration would be less efficient that a more conventional tractor 'powered glider' type design.

 

[Kai-003]

For me, 2 hours is more than enough. I dont like long flights just flying in circles like what the Endurance would be doing. The bobcat is a somewhat aerobatic plane, and has decent speed and payload capacity. You could also modify it to have 2 motors, maybe add a larger wing and carry stuff to drop. I built it around parts I had laying around, so there are some parts that could have been chosen that would be better.

 

[BayDesigns]

To be fair the Endurance was specifically designed not to go anywhere fast with its very slow flying speed.
For distance the equation would alter slightly favouring aerodynamic efficiency (a thinner low drag wing section with a higher aspect ratio and a slightly smaller higher pitch prop) but it would require a bit more power at the cost of a reduced duration.
Above a certain speed the pusher/wing pylon configuration would be less efficient that a more conventional tractor 'powered glider' type design.

Good to know. I like the pusher/pylon/pod configuration for keeping the prop out of the grass and having a pretty small body, just enough for electronics and a battery. I’ll probably do a preliminary model for a tractor-glider type airframe and one for a pusher-pylon. CFD should give me some idea what’ll do best at what speeds. Is your battery a LiPo or Li-ion? I would imagine that if you picked the right motor and prop, you could get decent speed and still great endurance. Were there CFD checks involved in the design of Endurance II? Obviously a tremendous amount of build experience is involved in getting everything done durably and still lightweight, but aerodynamic optimization is huge. For the concept in my head right now I’m thinking a fuselage pod (as small as possible) made of LW-PLA, wings and tail feathers done in XPS (density decided as a combination of strength and light weight), and either a balsa or LW-PLA tail boom. Winglets or some sort of raked wingtips would probably also be printed. Sorry for the long post and it’s definitely not my intention to hijack this thread, but long range planes came up and I’d like very much to get some feedback to see if my ideas are likely to yield an acceptable result.

 

[quorneng]

To say Endurance was 'designed' is not the full picture. It was really 'developed' over a period of 2 years which involved a lot of trial and error testing. Once the span had been set at 48" the target was to see how long I could get it to fly using a 1000 mAh 2s but carrying ballast equivalent of the 5000 mAh 2s. Much of the development was actually improving & rebuilding bits to reduce airframe weight. I eventually achieved 1 hour & 1 minute At that point Endurance II was a 'new' build that incorporated all the improvements learned.