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Old Sep 12, 2011, 08:18 AM
Earthbound Skyhound
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Quote:
Originally Posted by 2500GENE View Post
Pusher props are for models that use 2 motors to offset torque. One prop is a normal and the other a pusher, like a Multiplex Twin Star. They work fine on our type set ups but are not necessary.
It sort of mystifies me how people can mistake how to apply a prop, if they'd only look at the thing & consider how it works. Each blade has a heavier usually more rounded edge and an almost knife-sharp edge. The heavier is the leading edge - the sharp one is the trailing edge. The heavy edge acts as a frame or 'backbone' for the whole blade, to hold it in shape while it works, and provide the 'heft' to rip into the air it encounters as it spins without deforming the frame or shape. That heft isn't needed as much as you move along the blade to the trailing edge - hence the taper to the knife edge. Dual benefits there; less mass & weight, requiring less energy to operate, and the thin trailing edge allows air to come off more cleanly, producing less 'backwash' which acts as a sucking force, working against the prop's purpose.

Next, observe that the blade is canted across the hub - and this is the telling factor. One edge (the leading) will bite into the air, and as it slices thru, push or 'leverage' the air it slices off towards the rear of the plane, or, opposite of the direction you want the airplane to move. That in itself tells you how the prop blades physically operate, and how one should be mounted - so the leading edge will lead as it's spun - and the only thing remaining is to know which direction the motor spins the prop, so you can mount it so it'll do its job.

Internal combustion engines have no choice in this, but therein lies a huge advantage brushless motors provide - the ability to reverse their operating direction. Slap a prop on with the leading (thicker) edge frontmost, and if it doesn't blow air to the rear, simply change 2 wires & reverse its direction!

Of course, when considering one to order you don't (usually) physically have one in hand to look at and consider its shape or profile. But the fact we can make our BL motors spin either way, basically makes tractor vs pusher props moot -- you can order either and be assured it can be made to work.
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Old Sep 12, 2011, 09:11 AM
Earthbound Skyhound
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United States, NC, Richlands
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[QUOTE=Ole Joe;19286739]
Quote:
Originally Posted by StarHopper44 View Post
Well, if pictures are what it takes, I'll show ya mine if ya show me yours! *LOL*

And the last one, an end-on view. Note the motor doesn't even touch the 'lands' molded in.
--------------------------------------------------------------------------
Of course the motor doesn't touch the lands molded in. If it touched it would
impede the rotation of the motor bell an likely cause a reduction in RPM and
an increase in motor current.
Good point. But keep reading.

Quote:
I suspect that it was noticed at the factory
and they cut the land at the 7 o'clock position away so there would be no
interference.
But "they" didn't cut the land away - the motor did when I first fired it up. Hence, it was touching up until that point in time.

If they were "paying attention" enough to notice, much less to make any adjustment, this simply wouldn't have happened. The RESULTS are more indicative to being as I said - squirt, plop, moved while drying.

Quote:
If it would have been assembled correctly, it would have cleared
that land. Like I stated earlier, the BL motor with ply motor mount can be
positioned in the nacelle to be neutral, like yours, or rotated to have
either left or right offset.
To what degree, and why? IF a design standard was established, if anything is obvious, it's that they aren't following it!

Quote:
If installed correctly, the motor shaft will be offset
to the left, as viewed from the front.
Look....we could argue this 'til the cows came home, and it wouldn't change either of our minds. I believe you're speculating, based on what you've seen in the molded form - which I haven't - and trusting the accuracy or perfection of the molds. As I'm speculating, based on what I've seen, and experienced. Towards 'perfection' of the molded form - just look at the forward motor vent opening in the motor nacelle -- is that a perfect circle? Not on mine!! And that's just one of several 'less than perfect matches' in the halves.

The bottom line is, we (severally) have shown there are differences, and they don't hugely matter. I like the way mine flies, I'm happy with it, and I didn't build my plane to please anybody else. I'd suggest the best recourse is to agree that we disagree....there's no need to establish a 'right & wrong', & move on.
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Old Sep 12, 2011, 09:32 AM
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Quote:
Originally Posted by Flypoppa View Post
See post 8018. This is the replacement motor that I use.
thanks,,ordered it, $12 alot better than $40!
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Old Sep 12, 2011, 09:52 AM
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United States, CA, Sebastopol
Joined Dec 2010
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Quote:
Originally Posted by StarHopper44 View Post
It sort of mystifies me how people can mistake how to apply a prop, if they'd only look at the thing & consider how it works. Each blade has a heavier usually more rounded edge and an almost knife-sharp edge. The heavier is the leading edge - the sharp one is the trailing edge. The heavy edge acts as a frame or 'backbone' for the whole blade, to hold it in shape while it works, and provide the 'heft' to rip into the air it encounters as it spins without deforming the frame or shape. That heft isn't needed as much as you move along the blade to the trailing edge - hence the taper to the knife edge. Dual benefits there; less mass & weight, requiring less energy to operate, and the thin trailing edge allows air to come off more cleanly, producing less 'backwash' which acts as a sucking force, working against the prop's purpose.

Next, observe that the blade is canted across the hub - and this is the telling factor. One edge (the leading) will bite into the air, and as it slices thru, push or 'leverage' the air it slices off towards the rear of the plane, or, opposite of the direction you want the airplane to move. That in itself tells you how the prop blades physically operate, and how one should be mounted - so the leading edge will lead as it's spun - and the only thing remaining is to know which direction the motor spins the prop, so you can mount it so it'll do its job.

Internal combustion engines have no choice in this, but therein lies a huge advantage brushless motors provide - the ability to reverse their operating direction. Slap a prop on with the leading (thicker) edge frontmost, and if it doesn't blow air to the rear, simply change 2 wires & reverse its direction!

Of course, when considering one to order you don't (usually) physically have one in hand to look at and consider its shape or profile. But the fact we can make our BL motors spin either way, basically makes tractor vs pusher props moot -- you can order either and be assured it can be made to work.
I agree with all you said except something I just realized recently. And, it's probably not a big deal. But what about when right or left thrust offset is built into the model? This depends on the prop turning in a specified direction. I was considering getting a 6x4 for my Bix and just thought of this. As I said, probably not a big deal.
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Old Sep 12, 2011, 10:14 AM
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floats for bixler

Quote:
Originally Posted by jj604 View Post
Harry, what floats did you use?

Any pictures of the set up?

Thanks

John
John, I posted a picture at post #7891 and the floats are here: http://www.parkzone.com/Products/Def...ProdID=HBZ7390

harry
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Old Sep 12, 2011, 10:22 AM
SARG5
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10 Miles north of Russell, Ks. on US281 hy
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SHE DID A GREAT JOB.
Flew the Sky Surfer maden flight last evening . Every thing went great. Had to do a little trimming. But all and all, flew like it was on RAILS.
SARGE5
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Old Sep 12, 2011, 11:03 AM
Earthbound Skyhound
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United States, NC, Richlands
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Quote:
Originally Posted by moon12 View Post
a short vid of bixler water take-off and landing: http://www.vimeo.com/28875619

video from the plane: http://www.vimeo.com/28874058
This is a great little versatile plane!!
harry
NICE!.....rig and video!!
Hope to take mine there some day.
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Old Sep 12, 2011, 11:17 AM
Earthbound Skyhound
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Quote:
Originally Posted by erkq View Post
I agree with all you said except something I just realized recently. And, it's probably not a big deal. But what about when right or left thrust offset is built into the model? This depends on the prop turning in a specified direction. I was considering getting a 6x4 for my Bix and just thought of this. As I said, probably not a big deal.
Best answer:
http://www.rcgroups.com/forums/showp...postcount=8414
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Old Sep 12, 2011, 11:23 AM
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Originally Posted by StarHopper44 View Post
Yup... I read that. Agree...
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Old Sep 12, 2011, 11:28 AM
Earthbound Skyhound
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Quote:
Originally Posted by moon12 View Post
John, I posted a picture at post #7891 and the floats are here: http://www.parkzone.com/Products/Def...ProdID=HBZ7390

harry
Is the 'main trick' to find the CoG for the floats, & rig 'em to align that directly under the Bix's CoG point?
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Old Sep 12, 2011, 11:39 AM
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Quote:
Originally Posted by StarHopper44 View Post
It sort of mystifies me how people can mistake how to apply a prop, if they'd only look at the thing & consider how it works. Each blade has a heavier usually more rounded edge and an almost knife-sharp edge. The heavier is the leading edge - the sharp one is the trailing edge. The heavy edge acts as a frame or 'backbone' for the whole blade, to hold it in shape while it works, and provide the 'heft' to rip into the air it encounters as it spins without deforming the frame or shape. That heft isn't needed as much as you move along the blade to the trailing edge - hence the taper to the knife edge. Dual benefits there; less mass & weight, requiring less energy to operate, and the thin trailing edge allows air to come off more cleanly, producing less 'backwash' which acts as a sucking force, working against the prop's purpose.

Next, observe that the blade is canted across the hub - and this is the telling factor. One edge (the leading) will bite into the air, and as it slices thru, push or 'leverage' the air it slices off towards the rear of the plane, or, opposite of the direction you want the airplane to move. That in itself tells you how the prop blades physically operate, and how one should be mounted - so the leading edge will lead as it's spun - and the only thing remaining is to know which direction the motor spins the prop, so you can mount it so it'll do its job.

Internal combustion engines have no choice in this, but therein lies a huge advantage brushless motors provide - the ability to reverse their operating direction. Slap a prop on with the leading (thicker) edge frontmost, and if it doesn't blow air to the rear, simply change 2 wires & reverse its direction!

Of course, when considering one to order you don't (usually) physically have one in hand to look at and consider its shape or profile. But the fact we can make our BL motors spin either way, basically makes tractor vs pusher props moot -- you can order either and be assured it can be made to work.
True. The only reason I can see to go with the pusher prop is so that the motor is spinning in a direction that would tighten rather than loosen the prop nut. But, as has been said already, if you tighten it down properly to begin with it will stay on just fine. I am using a standard 6x4 with no problem. I still will try a pusher just to see if that theoretical side thrust/pusher prop/standard prop effect can actually be seen and demonstrated or if it exists in theory only (which is what I suspect since they all seem to go straight regardless).

Gord
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Last edited by Gordks; Sep 12, 2011 at 11:46 AM.
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Old Sep 12, 2011, 12:18 PM
Earthbound Skyhound
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Training session....

Got some more stick time in yesterday! Wheeeeee!!!
Day's lesson was flying Figure-8's, coordinating turns with opposite rudder & in fairly stiff wind. My main difficulty is keeping the nose up (level)....she wants to 'dive off' in turns & haven't yet developed the feel for completely counteracting that, but getting better. Sensei Mike told me next lesson would be inverted Fig-8's (while showing me how easy it was).....I told Sensei Mike he was certifiably NUTS!

Had a couple of unexpected thrills during the day. Besides the couple of OS moments I saved *LOL* (getting better at that too). Since Irene blew thru, mosquitos and gnats have been horrible. Out in the yard cleaning up damages, the zekes will about haul yo' butt OFF....come back inside & for next hour it's like you're on fire. Gnats on the other hand....with the windy conditions it's extremely dry out around the airfield, and they will almost literally COAT you, getting in your eyes, nose & ears looking for moisture. I broke out an almost new can of OFF & shared with the members & families - it was near empty before long....and them dang gnats soon licked that off & came back for more!

One REAL 'OS moment', I was in mid-turn supposed to level out & fly down the runway (as instructed), and I inhaled one! And I mean it stuck right in the sweet spot of my coughing mechanism....I couldn't even breathe! Thank 'the rules' or whatever, that Mike was right there to grab the box while I was in convulsions - and I was that! Not fun!!!

I mentioned families. We also used the day for a couple-weeks-early club meeting/planning meeting for a Big Bird Fly-In we're hosting Sat. Oct. 1st. We also had a cookout, thus the families were invited. The other 'thrill' was, with 4 slow-&-low parkflyers furballing it just above the runway, a 3-year old kid (you know how they can get gone in an eyeblink) decides to break away from Mom & run out across the runway. Mom saw him too late, screeches & takes out after him, so there's HER on the runway.....and the 2-yo she set down to go after the 3-yo, decides to take out after the running mom! Can you say "pandemonium"?? Mom then banishes Mr. 3yo to the confines of their SUV....soon after which he discovers Mr. Headlight Switch, & Mr. Car Horn. Only took mom about 5 minutes to do anything about it. Mr. Spanking was apparently not in attendance. << Mr. Rolleyes. *LOL*

One other thing....Mr. SuperCub came in Sat'dy via FedEx, so I'd arrived at the field a little early to put it together. Our CSO arrived a few minutes after, gave it the once over & declared it un-flyable. It uses a 'banished frequency', due to a history of causing interference with other radios. Couldn't just swap over to another receiver & use my regular Tx as I thought -- it uses 5-wire servos & the ESC is built into its Rx. *sigh*
Looks like this'n will have to be my secret 'Cornfield Trainer' until I can do a full upgrade.

So....there's my weekly flight training report, & my luck in action.
And th' beat goes on.
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Old Sep 12, 2011, 12:21 PM
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Originally Posted by StarHopper44 View Post
Is the 'main trick' to find the CoG for the floats, & rig 'em to align that directly under the Bix's CoG point?
I'm no expert, but that is what I did..(CG is maintained) here's a picture of them...This was a temporary set up so don't laugh to hard at the "tape job"
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Old Sep 12, 2011, 12:21 PM
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Quote:
Originally Posted by Gordks View Post
True. The only reason I can see to go with the pusher prop is so that the motor is spinning in a direction that would tighten rather than loosen the prop nut. But, as has been said already, if you tighten it down properly to begin with it will stay on just fine. I am using a standard 6x4 with no problem. I still will try a pusher just to see if that theoretical side thrust/pusher prop/standard prop effect can actually be seen and demonstrated or if it exists in theory only (which is what I suspect since they all seem to go straight regardless).

Gord
I think the main difference you'll see (if you do) will be how tight it'll turn one way vs the other. I'd suspect you'd have to have a lot of experience to really tell.
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Old Sep 12, 2011, 12:32 PM
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Originally Posted by moon12 View Post
I'm no expert, but that is what I did..(CG is maintained) here's a picture of them...This was a temporary set up so don't laugh to hard at the "tape job"
Expert or no, it obviously works! Thanx for that info....will bear it in mnd when I get some floats. (Which, come right off 'another plane' I just got!)
How conveeeeeeeennnnient.
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