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Nov 09, 2005, 08:25 PM
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DiveBombDave's Avatar
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Hey no sweat. I was thinking more about your nippy... I used an axi direct drive outrunner and compared it to a couple of gearbox 400 and 480 systems, and I'll give you some advice. Spinning a smaller prop faster, the direct drive setup needs a drag free airframe (and airfoil!) in order to develop lift with some speed. The gearbox deals swing a much larger prop slower, and can develop all types of static thrust but run out of pitchspeed with any real airspeed. Your fuse's drag will be as small as you can make it either way, so the airfoil is the important thing to consider. With my 11" chord wings, spans of 60,68,70,75, and 78.... when I make them with a thin 1" thickness of foil at the CoG, they run fine on direct drive small props (with the watts/lb math you were doing) - but I like the flight characteristics of the 1.5" thick foil (going from a 9% thick foil to a 14% thick) better, and it seems to drag this size/weight bird's airspeed down just outside of the efficient range of the prop. So, I started flying gearbox setups and am much happier.

What this means to you - if you like the nippy and it thrust's out OK (200 watts seems fine, what prop/rpm?) - maybe consider a 1.25" thick foil shape (overall, from bottom wing surface to absolute top, not rib height). My 70" in this thead is 1.5", but there is not much diff until you get down to 1". Those are fast and stall earlier when flaring on landing, and lose tremedous 'arch strength' overall (see above spar technique carefully).

Still working on the pics.

I'm going to build AP2b for backup to this one, around a 400 gb setup, same prop, but I know I'm internalizing the tail booms/servos into the wing. I may document it here, too, and maybe have it done by the time your FFF gets in.

Any questions feel more than free to ask.

Dave
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Nov 09, 2005, 08:31 PM
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DiveBombDave's Avatar
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Oh yeah, just saw your 30oz thrust post... sounds like my axi spinning apc 9x4.5E at 9800rpm. I would limit span to maybe 64-68" on the 1.25" foil, 11" chord. If you go with a much longer chord, like 15".... the 1.25" foil is 11.3% of the 11" chord, so the same foil enlarged to 15" would be 1.75" thick, and then you're talking monster foil drag. Really slow flying, and too slow can be bad when the wind picks up. Soooo - food for thought. Keep chewing.

Dave
Nov 09, 2005, 09:10 PM
Flying on Flux Capacitors
Flipper_118's Avatar
Thanks for the info, I don't know what kinda revs the motor is doing but I am spinning a APC 10*4.7SF. Amps seem to be outta the motors range specs but it runs stone cold and my packs don't heat up.

Curt
Nov 09, 2005, 09:26 PM
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DiveBombDave's Avatar
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Sounds like it'd fly just fine the project you're talking about.... some ppl say the SF props flex and lose a lot of pitch above 6000rpm or so, and I'd imagine you're at about 9000 at least. Consider having some E series props on maiden day, like the 9x4.5E. I can run it in motocalc if you can get me the model and packs info (I'm on proxy server and my motocalc isn't getting through to the online database thingamajig).
Nov 09, 2005, 10:47 PM
Flying on Flux Capacitors
Flipper_118's Avatar
Thanks for the MotoCalc offer but don't bother right now. Once I get some FFF then I'll start crackin on the build.
Nov 10, 2005, 07:15 AM
Registered User
Son of paleface....purlease....an Aussie that doesnt know what a ball and chain is?lol.thought u had one as part of the deal!!!
Nov 10, 2005, 03:21 PM
Ozzie Express wiggy pilot
SON OF PALEFACE's Avatar
HAR HAR HARDY HAR I was wondering wen someone wood go for that and sure'nuf weve caught a live one....CHOMP....
I DONT see in yaw public profile where U R from so I cant recipracate
Nov 10, 2005, 03:34 PM
Ozzie Express wiggy pilot
SON OF PALEFACE's Avatar
Quote:
Originally Posted by DiveBombDave
Paleface - Ah, "no worries, mate." Love to have you over here in the spring... chicks really dig the accent. We could go to the bars and put you on point, seek and destroy.

Flipper - You're loaded at about 9.14oz/ft2, so it seems it should glide OK, but you SS guys know the way that wing flies. I have motocalc if you have your motor specs - do you know the static thrust you're getting? I had an axi with 900g thrust that hauled up a 48oz beast for 100's of hours. Climb was respectable at 30deg and maybe 400-500fpm. This same plane I could "stall it down" with a little up elevator, it would come down like a real elevator. Maybe if you're trimmed for powered flight, when you cut the throttle try a few clicks of down trim and see if the speed up will help your glide angle/ratio. In other words, experiment with different elevator trims when gliding and see if you can get a little more outta your SS.

My wing is 70x11 and AUW is in the 45oz range with 8.2oz cam bundle and maybe 3 oz in forward LG alone. And the metal planetary I have runs my motor, prop, and ESC weight up to 230g, or about 8 oz, where your nippy is lighter. Just in motor system and LG this design seems like it could be done the same size at 40oz auw.

Of course not telling you what to do, just very passionate about my build and trying to help you with the stuff I've been through. Lemme know what you decide!

Dave
Dave I think "seek and ravage" wood B better I am rushing to the travel agent as we speak
Nov 10, 2005, 03:43 PM
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DiveBombDave's Avatar
Thread OP
hehehe....

note - added pic of the spar contruction on post 17 of page 2. Shows the shallow angle and trianglar area better than I could word.
Nov 10, 2005, 07:31 PM
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DiveBombDave's Avatar
Thread OP

Crashed and flew again.


Well, talking about spar strength....

Took AP2 to shoot a vet clinic/commercial area in a town named Waco, no less. Yes, very ominous.

7-10mph wind, flew great, glided great, ya ya ya. Still had to keep on thumb lively on elevator and rudder when full throttle (so much power it can get pointed the wrong way quickly).

Here's the pilot error - talking to 4 generations of ppl, crowding around to see the video, maybe 6-9 ppl standing all around. No prob, done this before. Lost concentration on final approach into a small field, swung out wider than I had wanted to because I was looking the other way having a conversation. Noticed she had settled behind some wires that I hadn't noticed because I hadn't checked out every angle on the field (I assumed launch this one way, land this one way, and looked at nothing else).

Well, I gassed it about one full second before the strike, and only lifted enough that the forward LG hit the wire. Fluttered straight down about 40-50 feet, but luckily did a belly-flop at the last instant.

Inspection showed LG had loosened slightly from the balsa block that's internal, and the fuse had crumpled in the dead area between the cam and the wing front. Looked like a broken nose, just a little crooked. Everything (thorough inspection) was fine, threw in new batts and pitched back up for a final flight. Flew and landed well.

Odd note - while landed and inspecting, a full scale came over trees 80' tall, at about 200' max alt. I didn't see/hear it until it was like 200 yards away, cresting those trees. He pulled into a 60 degree bank over our heads at 200'. I don't have my license yet, but I know that is a huge NO NO. He left the area within 30deg heading to his original flightpath (like he came to see my plane and turned on the spot and left).

I was doing my shooting at about 400'. What's the deal with this? I'm not as concerned about my plane, but when I saw how all these old people standing around me started scrambling.... it was AIR SHOW scary the move he pulled.

Alright - what does this mean? I can still fly her, but the rush to get a less prototype looking AP3 built is on hot. I'll be doing all the 'if I had it to do over again' stuff in my head tonight.

Here's a pic of the area, real pretty little community. Friendly people.

Dave
Nov 10, 2005, 08:10 PM
Flying on Flux Capacitors
Flipper_118's Avatar
200'! That is definatly a no no NO. I have only seen 1 type of plane fly low like that where I live, but he's a crop duster, and he flies over crops, not people! I live out in the sticks so there is one guy down the road that has his own runway for his little cessna. Always flys way up so I have no fear of him buzzing me, but if I here a prop other then my SS, I usually get down quick, and I get down super quick if I'm flying at speck altitude.

Good thing the only damage to you bird was a slightly broken nose, now you have an excuse to spend more money and time on your plane. Rebuilding is always fun, design usually improves.

Curt
Nov 10, 2005, 10:33 PM
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DiveBombDave's Avatar
Thread OP
Yeah, I was offended and I'm really hard to offend. The only other time's it's happened was in FL and my old lady was laying in the back of my boat naked sunbathing, and a cessna spotted her with binocs and flew past the lake and came back at 100' off the deck over the lake (now as far as no nos go, that's even bigger over water). I literally could've casted my bait and hit him going over.

I came home tonight and (topic: old lady) she looked at me smiling really big and saying, "I just crashed AP2...." I was thinking about how nice it was to be forced to start a job I'm dying to do, but she just keep looking at me like, "When is he going to Manson-Out on me?" I've had a couple of instances in the past of giggly-type Jack Nicolson/The Shining laughing-because-youre-so-hacked-off thing, and she thought she was on the brow of a biggie.

Dave
Nov 20, 2005, 12:45 AM
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DiveBombDave's Avatar
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Well, just wanted to let everyone know that I've started the new build, a backup to this bird, that I'm calling AP3. The booms and servos are internalized, the motor mount is refined, spans 72x11 with 1.375" thick foil, kinda selig 3021/kinda eppler 214. I'll be started a new thread for it's build pics once I'm done. Right now I have the wing ready to close up with spar, servos, and tail booms in place. I have left to do the inverted V tail, mock up a fuse, and mount the motor and rcvr. I expect AUW to be 37oz unloaded with a belly skid fuse (no heavy LG, maybe mono wheel up front and strut in rear at most).

I have some pics so far, but I'm more interested in finishing her than posting - here's two just for kicks.

Dave
Nov 20, 2005, 01:51 AM
Flying on Flux Capacitors
Flipper_118's Avatar

Yesss!


I love your builds and I am still waiting on my foam (its such a kicker when you currently don't have a AP plane to fly, and then you get a beautiful day like it was today, we should have 6 inches of snow, but today was above 10C!)

Are you going to have a flexy tail like your last, or are you keeping the tail solid mount? I'll be following this one very close.


Good luck, and please, don't skimp on pictures. Just snap as you work and post later, that way your work won't get interupted, and I can still get my fix.

Curt
Nov 20, 2005, 02:18 AM
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DiveBombDave's Avatar
Thread OP
Hey Curt!

This one will be locked down really nicely. It's steel pinned into the spar, epoxy over that, then blocked with balsa and chocked up with a chopstick (that gives me 2 deg of wing angle to the air, been using 3). I think the only thing I'll do diff with the tail booms from where she stands now is I'll add chopsticks wrapped with spectra to the undersides just behind the wing (this made the CF spar crazy stiff). Only adds .2g/inch or 4g per side. .3g/inch with epoxy bed. Here's a couple more pics that'll give ya some ideas.

Dave


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