Hello all,
I'm trying to decide on an air frame/platform for a combination of local conditions and of course my own goals. So first I'll outlay the problem:
I live in Flagstaff, Arizona. Depending on where I am, ground level is about 7000-8000 ft ASL. So we're pretty high altitude. On top of that, for several months of the year and sporadically at other times, we have pretty high winds. 45mph, say, and I don't want to be grounded for half the year. (It can get higher but I think that's enough tolerance for most days).
As for my own goals... I'm rather interested in building a multicopter with as much endurance as possible (including an FPV and telemetry system).
My thoughts on an approach? Octocopter, with as much payload as is left over from the FPV, etc. put towards battery packs. The 8 motors should provide plenty of stability even with winds... though, of course, it's more power consumption, weight, and so on...
A smaller 3 or 4 rotor multicopter wouldn't consume as much power, but I'm not sure if it's better to have more motors + more batteries, or if the lower draw but less payload would work out better/longer endurance. And, of course, the altitude means significant derating for any prop system. I can expect ~80% of the thrust you'd get at sea level, maybe.
I've considered a fixed wing system, but I don't have any training with fixed wing RC craft and, while I do have space, my property isn't very flat, lots of trees (actually that's a good description of Flag in general)... I'd probably have trouble launching and landing.
Any suggests, thoughts, advice, etc is much appreciated. Budget is fairly deep. Thanks in advance!
Replies
Hi,
I live in Colorado at about 6000 feet and we also get strong winds in the spring and a fair amount of snow in the winter but with the right plane you will think of 45 mph winds with a smile on your face. I have flown tri-copters in a light breeze and they were a handful. Not fun. However, if you want a suggestion for a plane that will fly in all weather except maybe rain, get a Bixler 1.1 or 2 and an Orange stabilizer. After you fly awhile stock put a 2826-6 motor in it and cut the wingtips off at the ailerons and you can go looking for wind. Flying in 30-40 mph winds is too much fun and as long as your plane goes faster than the wind is blowing you are good. And if you fly in the snow you will really appreciate RTL mode of the APM. The B1 is a real cheap ride that you can get into for about $75 if you have a radio. And it works very well with the APM. Copters are fun when there is only a little wind but the B1 is better the other 80% of the time. I've lived in Flagstaff so I know what you are talking about regarding the terrain thing but with a little sim time you will be ready to play and it won't be long until you'll be landing in your yard. The B1 goes slow when you need it to and is very easy to fly. I could go on forever but you get the picture. If you want to fly a lot you need a plane.
Some aircraft is specifically designed to deal with high winds, like hurricanes, most model aircraft lacks wing strength. However, you can build strength into your platform. A fixed wing example: botmite-1 For flight training you can use Real Flight software. And while helicopters demonstrate dynamic maneuverability, the price for chopper agility comes at 16:1 energy usage versus fixed wing aircraft. So, if time aloft is the goal, fixed wing is the choice.
Thin wings typically weigh more and strength goes up by the 4th power with diameter - See: Mechanical Engineering texts.
Rite wing offers a hand launch platform with short landings and easy launches for rugged terrain - I have no affiliation.
I have discovered through experience that many scale models - while emulating the look of wonderful aircraft at full scale - lack the corresponding match in performance due to the vast difference in Reynolds' Number. This means to get really wonderful performance, a re-engineering, re-design of the airfoil and wing is essential. This may range from the non-trivial to the practical try and test methods. Now, there are excellent resources in books and software to cut down on the time and effort to exact a wonderful result. Happy flying!
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High there,
High altitude will reduce payload, but not the biggest problem. More motors will contribute to the problem as the efficiency definately will drop. So three Motors +1x servo could prove the optimum. Keep things light ! and motors strong enough. As bigger the props as better the efficiency.
High wind and multicopters is definately bad, single rotor heli (bigger size) copes much better!
To play around with efficiency and so on:
http://www.ecalc.ch/
45 mph wind is a no go for any model aircraft, is even not advisable for real sport aircrafts.
b.r.
Wolfgang