petergaultney
New member
I sure do hope someone here can put me on the right track.... this hasn't been the best introduction to foam building. 
[CONTEXT]
My wife and I are relatively new to the hobby - she got me an E-Flite Apprentice for Christmas, and we've been flying a ton ever since. She got herself a Hobbyzone Duet and has been loving it.
We decided to try to get into scratch building both because it's cheaper and because we like building things. Unfortunately, this hasn't been quite as smooth a start as we've had with the prebuilt planes.
We wanted something that was as slow and lightweight as possible, and we wanted a speed build kit so we wouldn't have to stress over whether we did a bad job cutting things, so we got the Old Fogey speedbuild. We didn't buy the Power Pack kit because we have a bunch of components (motors, props, etc) we bought in bulk from a local hobbyist who's getting out of the hobby.
I'm very familiar with aerodynamics because I have some background in general aviation. I've also done a ton of reading and research into the hobby over the last few months.
[BUILD]
Our servos (9 gram Hextronic) and control surfaces are working great. Receiver is range-tested and working. Batteries are fine, ESC works fine, etc. The wings have 2 inches of polyhedral on each end (I made a foam guide to make sure they'd be exactly the same height, and I adjusted them to have slightly less polyhedral than the laser-cut kit suggests, because I've seen elsewhere that the standard amount of polyhedral has given a lot of folks trouble with dutch roll. I'm using 9x4.7 slowfly props from Hobbyking, and I've balanced them with tape. The propeller is definitely mounted 'forward' - the plane blows air backwards and pulls itself forward through the air when the throttle is turned up.
[THE PROBLEM]
Not enough lift! Which is clearly due to not enough forward speed/thrust. I've run down a hill holding the plane in my hand above my head, and it strongly wants to pull upward out of my hand. But no matter what I try, I've not been able to get the plane to pull itself forward fast enough to create the lift it needs.
I've tried two different motors. First, a 25g 1400kv Turnigy (think it's a 2822-azj or something like that - you can't really buy them anymore). It was way underpowered. On a 2 cell battery, it wouldn't fly farther than I could throw it before just hitting the ground. On a 3 cell, it was willing to stay in the air, but I measured the current draw using an inline meter on the table and it was WAY higher than the 7 amps the motor is rated for. And it made the motor way, way too hot to actually consider using.
So I decided to try one of our larger motors. I switched to a roughly 50 gram, 1000kv Turnigy (D2830-11). Now, I understand that 1000kv will ultimately produce less thrust than a 1400kv motor at the same voltage, so I immediately recognized that there was no way this would work with a 2 cell. Which is a shame, because they suggest that flying the Old Fogey on a 2 cell will make it more docile, and that has been our desire/plan all along. But I've now tried it with a 3 cell (1300mah), and it still won't fly. From the moment it leaves my hand, it's like it's on a perfect glide slope for a landing - it usually makes it about 20 or 30 feet before finally contacting the ground. At 100% throttle. Frankly, I just can't understand it. I've tried two different motors, 2S and 3S batteries, 9x4.7 and 8x6 props - all of which supposedly are within the ballpark of what this plane needs. But it simply can't keep itself in the air.
All-up weight is right at 500 grams, and without the 3S 1300mah battery it's at 400 grams, so it's right around the expected battery-less weight of 373g/13.3 ounces.
[OTHER ISSUE]
I've had some difficulties getting a prop mount that really works. I've been trying to use the tapered cone-style prop savers as seen here, but I find that over 50% throttle gives me vibration and prop whine. So I've resorted to other, weirder methods of getting the prop to mount properly. I'd appreciate advice on this, but this isn't really my main issue. I am pretty confident that the prop is actually rotating at the speed of the motor, because I know what it sounds like (and what it feels like) when it doesn't.
[SUMMARY]
The Old Fogey was supposed to be a relatively slow flyer. And supposed to be able to run off a 2S on a 1400kv motor. But it doesn't even come close. And I can't even get it to fly on 1.5x the voltage (3S) with a 1/1.4 kv motor (1000kv). Something clearly isn't right. I don't really want to buy yet another motor when I already have two that should at least theoretically work (even if the small one would definitely burn out eventually at 3S/11.1V). Does anyone have any ideas what we might be doing wrong? I'd really appreciate some help, because this has been a surprisingly frustrating intro to scratch-building, and it's a hobby I'd like for my wife and me to stay in for a long, long time.
[CONTEXT]
My wife and I are relatively new to the hobby - she got me an E-Flite Apprentice for Christmas, and we've been flying a ton ever since. She got herself a Hobbyzone Duet and has been loving it.
We decided to try to get into scratch building both because it's cheaper and because we like building things. Unfortunately, this hasn't been quite as smooth a start as we've had with the prebuilt planes.
We wanted something that was as slow and lightweight as possible, and we wanted a speed build kit so we wouldn't have to stress over whether we did a bad job cutting things, so we got the Old Fogey speedbuild. We didn't buy the Power Pack kit because we have a bunch of components (motors, props, etc) we bought in bulk from a local hobbyist who's getting out of the hobby.
I'm very familiar with aerodynamics because I have some background in general aviation. I've also done a ton of reading and research into the hobby over the last few months.
[BUILD]
Our servos (9 gram Hextronic) and control surfaces are working great. Receiver is range-tested and working. Batteries are fine, ESC works fine, etc. The wings have 2 inches of polyhedral on each end (I made a foam guide to make sure they'd be exactly the same height, and I adjusted them to have slightly less polyhedral than the laser-cut kit suggests, because I've seen elsewhere that the standard amount of polyhedral has given a lot of folks trouble with dutch roll. I'm using 9x4.7 slowfly props from Hobbyking, and I've balanced them with tape. The propeller is definitely mounted 'forward' - the plane blows air backwards and pulls itself forward through the air when the throttle is turned up.
[THE PROBLEM]
Not enough lift! Which is clearly due to not enough forward speed/thrust. I've run down a hill holding the plane in my hand above my head, and it strongly wants to pull upward out of my hand. But no matter what I try, I've not been able to get the plane to pull itself forward fast enough to create the lift it needs.
I've tried two different motors. First, a 25g 1400kv Turnigy (think it's a 2822-azj or something like that - you can't really buy them anymore). It was way underpowered. On a 2 cell battery, it wouldn't fly farther than I could throw it before just hitting the ground. On a 3 cell, it was willing to stay in the air, but I measured the current draw using an inline meter on the table and it was WAY higher than the 7 amps the motor is rated for. And it made the motor way, way too hot to actually consider using.
So I decided to try one of our larger motors. I switched to a roughly 50 gram, 1000kv Turnigy (D2830-11). Now, I understand that 1000kv will ultimately produce less thrust than a 1400kv motor at the same voltage, so I immediately recognized that there was no way this would work with a 2 cell. Which is a shame, because they suggest that flying the Old Fogey on a 2 cell will make it more docile, and that has been our desire/plan all along. But I've now tried it with a 3 cell (1300mah), and it still won't fly. From the moment it leaves my hand, it's like it's on a perfect glide slope for a landing - it usually makes it about 20 or 30 feet before finally contacting the ground. At 100% throttle. Frankly, I just can't understand it. I've tried two different motors, 2S and 3S batteries, 9x4.7 and 8x6 props - all of which supposedly are within the ballpark of what this plane needs. But it simply can't keep itself in the air.
All-up weight is right at 500 grams, and without the 3S 1300mah battery it's at 400 grams, so it's right around the expected battery-less weight of 373g/13.3 ounces.
[OTHER ISSUE]
I've had some difficulties getting a prop mount that really works. I've been trying to use the tapered cone-style prop savers as seen here, but I find that over 50% throttle gives me vibration and prop whine. So I've resorted to other, weirder methods of getting the prop to mount properly. I'd appreciate advice on this, but this isn't really my main issue. I am pretty confident that the prop is actually rotating at the speed of the motor, because I know what it sounds like (and what it feels like) when it doesn't.
[SUMMARY]
The Old Fogey was supposed to be a relatively slow flyer. And supposed to be able to run off a 2S on a 1400kv motor. But it doesn't even come close. And I can't even get it to fly on 1.5x the voltage (3S) with a 1/1.4 kv motor (1000kv). Something clearly isn't right. I don't really want to buy yet another motor when I already have two that should at least theoretically work (even if the small one would definitely burn out eventually at 3S/11.1V). Does anyone have any ideas what we might be doing wrong? I'd really appreciate some help, because this has been a surprisingly frustrating intro to scratch-building, and it's a hobby I'd like for my wife and me to stay in for a long, long time.
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