RE: Aurora 60 Build Thread - Electric Power
 

Dan Hines' email is [email protected] I think his web site is in the works.

RE: Aurora 60 Build Thread - Electric Power
 

Thank you rainedave...I've messaged him and looking forward to his reply!!

RE: Aurora 60 Build Thread - Electric Power
 

I've mounted the wings to the fuselage using Gator RC's adjustable system.

After mounting the leading and trailing edges to each wing panel and then trimming/sanding, I readied the lite ply inner ribs to mate with the Gator adjusters that were now mounted to the fuselage from the inside. As you can see in the one photo, I've left plenty of room for the Gator mechanism to move either way for incidence adjustments. The process I use is self-explanatory if you follow the pictures. After I achieve a nice fit of the ply ribs to the fuse (they readily slide on and off the locating dowels), I then glue the wing panels to those ply ribs using zap. Both wing panels now slide on/off the tube/fuselage rather nicely and I managed a good fit WRT wing panel/fuselage gap.

Next step is to cut out the ailerons, hinge them to the wing panels, and then tack-glue them back into place before I proceed with final sanding. The tips will also be installed at that time.

RE: Aurora 60 Build Thread - Electric Power
 

Well..If that's not Kewl Lookin'..I'm not sure what is!!

Have Fun...

Chuck

RE: Aurora 60 Build Thread - Electric Power
 

Damn Jeff!!

That is Awsome!
What kind of speeds do you think you'll be hitting?
The other week we clocked a little EDF Rafale at 177mph! And if 2s guys say they would miss that sould of a screaming engine, they never heard this little motor scream! I think I would go electric before 4s.. That EDF was just screaming


DM

RE: Aurora 60 Build Thread - Electric Power
 

Guys, glad you're enjoying the build.

Top speed...that's a good question. Due to the thinner wing and modified airfoil, I'd estimate the overall coeficient of drag of the airframe (primarily induced + profile) to be a tad less although the stab is noticeably thicker to accomodate the Gator adjustable stab mechanism.
I think the determining factor will be the electric powerplant and the larger diameter 13 X 13 APC prop. I don't have PCalc #s handy but I expect the plane to be a bit slower in level flight but with killer vertical performance. And given the prop "braking" potential on downlines of these electric setups, it could amount to more of a constant speed type of presentation ?? Chronos from Montreal really likes the way his flies and he's using the same setup. Should be interesting!

RE: Aurora 60 Build Thread - Electric Power
 

Jeff,

What do you expect the prop RPM to be at full battery charge.

RE: Aurora 60 Build Thread - Electric Power
 

8178, I just PM'd Chronos about this. He only mentioned the wattage achieved using the 13 X 13 which was pretty darn impressive. Hopefully he can tell exact #s as opposed to my extracting approximates using the calculator.

RE: Aurora 60 Build Thread - Electric Power
 

Hi guys,
FYI
With the 14X12 (1500W-in setup) we had around 7.8-7.9k rpm and clocked the plane at 180kph straight & level.
The 14X14 was too much for the esc (1900W-in setup), but we could see the plane accelerating vertically... impressive... well beyond 180 kph and the esc limits (the ESC caught fire later on)!

The actual setup (not flown yet) is around 1700-1800w-in and should also be well above 180kph

Chronos

RE: Aurora 60 Build Thread - Electric Power
 

By the way,

Did I mentioned I liked the 14X14?

RE: Aurora 60 Build Thread - Electric Power
 

I know nothing about electrics other than what I occasionally see at the flying field and they are mostly hanging on little foam stuff. I would have thought the larger motors would turn more RPM so you could turn a smaller prop with more pitch. The small motors I’ve seen sound like they are turning 15K or more. I did see one catch on fire in the air though and that was pretty cool/hot? I guess the HP is not related to the engine RPM. What would the top RPM be for a typical large motor? I like the smell of burning caster and nitro so I expect electric is not for me.

RE: Aurora 60 Build Thread - Electric Power
 

Today I decided to tackle the stab.

The first photo shows my false rib layout scheme using a felt marker. I've also cut the false ribs from lite ply which will be trimmed after I cut the slots in the foam and test fit them.

2nd photo shows the 3mm slot cut into the foam and the airfoil outline on the false ribs that denotes what I have to trim prior to gluing all in place. The Gator phenolic sockets have been cut and the ends capped with approx 7mm hanging out of the foam. Keep in mind that 3mm of the 7 will be absorbed by the lite ply false rib that will 'cap' the entire inside of each stab half....that's later in the process.

3rd photo shows all the 'internals' glued into place, the sheeting cut and prep sanded, as well as the cores sanded and vaccumed. Once again, make sure you've removed all residue from the wood and foam surfaces that will be glue together. As I write this, both stab halves have been sheeted and the 3 hour epoxy is drying.


8178, ref electric motors, with a few exeptions you'll notice that those electrics flying around have a disproportionately large propeller for the airframe when compared to their glow engine counterparts. Although I'm hardly qualified to speak about electrics, it seems these motors have natural torque curves based on winding pattern and winding #s and when I first started researching which motors I could use, I quickly found out that very few electric motors are able to efficiently make the required big power using smallish props.... the 11 and 12" ones we're used to using on these airplanes.....and somewhat restricted to due to ground clearance issues.....holy run-on sentence Batman! Anyway, I'll let someone else rescue me from this one but I hope to see more motor options available for these types of conversion projects in the future.

RE: Aurora 60 Build Thread - Electric Power
 

From experience,

Electric motors are able to efficiently turn at high rpms even more naturally than big props at low rpms. Remember: The lower the winding, the higher the kv (rpm per volt), the higher the amp rating.
There are scientific reasons to that but lets keep everything down to earth.
FYI, I am preparing a crazy flying wing, the motor (electric) will spin a 5.25X6.25 @ 42-43K rpm... talk about rpm!!!

Inrunners have a natural tendency to spin at high rpms (even higher than glow's) which is good for EDF/cars/boats/helis but not for airplanes or sailplanes. Thus people:
1. matched high kv inrunners to gearboxes
or
2. created low kv inrunners like Neu's ORK/Mega/ Plettenberg all of these are good stuff by the way, but they don't like spinning at rpms below 10-20K

Then people came with the idea of a rotating case, and here came the outrunners. They have more torque, but can also spin at high rpm depending on the winding. To reliably spin at high rpms, an outrunner should have a well balanced cage and at least 2 ball bearings to support the cage. They are less efficient than inrunners but doesn't need a gearbox (which eats part or all of the inrunner's advantage in efficiency)

So why people are putting oversized/low pitch props on their electric model? I have an opinion based on facts, thus we can't infer it is a fact as it is a mere interpretation of observations.
Before lipos battery packs were heavy to fly a .45 plane, you needed a 18sub-C cells pack weighting 42oz. To be able to fly it securely, you needed a lot of thrust thus an underpitched prop.

Nowadays big props are mostly for 3D flyers, parkflyers or everything needing thrust like sailplanes (I will use a 18.5X12 on a new project).

my 2c

RE: Aurora 60 Build Thread - Electric Power
 

After the skins were glued in place, I added the trailing and leading edges and trimmed as required. I then cut the elevators from each stab half and glued the required edge pieces either side of the hinge line. I used 1/4" thick balsa ahead of the hinge line and 1/2" behind it. I prefer 1/2" behind the hinge line so that I have plenty of balsa left after the front of each elevator is beveled.

Next step is to make up the 2 lite ply inner ribs, trim them roughly to shape and then install the Gator stab adjusters. The stab adjusters will be mounted to the inside of each rib and countersunk into each stab half when the ribs are mated and glued to the stabs. For each stab half, access to the stab incidence/locking screw adjusters will be via a single small hole on the underside on the skin. After the adjusters are in place, I glued the ribs to the stab halves and trimmed/sanded as required.

Next step is aligning the stab halves on the fuselage and then gluing the phenolic socket which houses the aluminum stab tube in the fuselage.

RE: Aurora 60 Build Thread - Electric Power
 

Electric hotliners come close to duplicating the kind of performance you would get from a '70s/'80s pattern ship.

Tom

RE: Aurora 60 Build Thread - Electric Power
 

Except that hotliners use 15 to 17 inch square props (15X15 to 17X17). They are using short bursts (less than 10 sec) at 200amps from a geared setup.
A pattern ship use an amount of continuous power + short to medium bursts at a maximum of 100amps. The geared setup offers no avantage as old pattern ships don't need such big props..

RE: Aurora 60 Build Thread - Electric Power
 

I just finished the complete stab assembly including hinges and mounting to the fuselage.

As far as techniques finishing the stab halves and elevators, it's all standard stuff. Of note, the stab tips are 2 X 1/2" balsa sandwiched around 1/32nd ply. The ply helps me keep track of center when carving/sanding the tips but more importantly, it makes for tough tips able to withstand a reasonable amount of hanger rash.
The difficult and time consuming peice was aligning the stab halves to the fuse and permanently gluing the center section of the Gator phenolic socket. I spent about two hours trying to get it right and even then I had to go back and re-do it once. I thought I had it nailed but after I tack-glued the socket and re-measured, I found it was off just enough to piss me off! My biggest obstacle was getting glue to the socket when both stab halves had to be snug to the fuselage to obtain a valid measurement. In the end, I used a syringe to get the glue where I needed it and the stab is perfectly parallel to the wing and aligned within 1 millimeter when looking from above. After the stab alignment was done, I had to carve and sand the lite ply inner ribs here and there to get a nice looking fit as the fuselage sides in the area of the stab narrow towards the direction of the vert stab.

Next in line is finishing both wing halves. Cutting the ailerons out, installing the wing tips, and trimming the wheel wells and aileron servo bays.

RE: Aurora 60 Build Thread - Electric Power
 

Looking beautiful, Jeff. What type of power supply do use for your lipo charger? It must be of pretty high amperage (I'm curious, because I just converted a computer PS for my Triton2 yesterday). I remember taking about two hours or more aligning the anhedral stab on my UFO. I cut over-sized holes in the fuse and shimmed it in place the same way you'd hand a window or door frame, then filled it in and covered the joints with microballoons. Is there a practical way to add fillets and/or fairings when you use adjustable surfaces?

RE: Aurora 60 Build Thread - Electric Power
 

RainDave, ref lipo chargers....don't have a clue yet. I'm "brailing" my way thru this entire electric powerplant aspect.

As far as fillets, that's an aspect I'm still undecided on.
The stab is easy as I've managed to achieve a good fit to the fuselage and I'm not going to bother with fillets. If you look at the attached photo of Steve Helm's Aurora (I'm going to use the same scheme and colors), you'll notice that the lack of a stab fillet will not be a big deal at all given the demarcation line between the blue and the adjacent fuse colors. Not having a fillet will actually make it easier.

The wing fillets are another story. I think I have no choice but to install them otherwise it will look a bit odd. As well, I have small gaps between the wings panels and fuse that would be difficult to eliminate. So how do I maintain some degree of adjustability for each wing panel if I build fillets? I guess I'll have to leave a slightly larger gap between the wing skins and the fillets, somewhere between 1/16" and 3/32"? I trust my incidence measurements so if I have to adjust a panel, only a minute adjustment should suffice....I hope. Otherwise I'l have to hack and slash as required. As to when to build the fillets, I'm going to follow 8178's example where he built his fillets after having glassed the fuselage.

RE: Aurora 60 Build Thread - Electric Power
 

Hi Jeff,

Great build thread. Love the plug-in stab and wings. Some may not like it, but certainly will make radio/battery install in the fuselage much easier. Ryan moved his tank back in his and had some "fun" words when telling me about it. I also remember mounting the tank in the mid-fuse on mine and it wasn't fun.

As for fillets, build them onto the wing root. I've seen it done on other planes and it works fine. It then becomes an adjustable fillet. Since you probably aren't going to have to move your wing much, it should be fine.

RE: Aurora 60 Build Thread - Electric Power
 

JAS, I never thought of that approach. It would certainly solve the asthetic problem as long as the fillets have a nice fit with the fuse.

Any photos out there for reference?

RE: Aurora 60 Build Thread - Electric Power
 

For the power supply ramboy in its time on ebay provided good ones for 12$. Otherwise you can get a good one for 30$.
Stay away from PC power supplies... good ones are more expensive require some modifications. Used ones are often disposed because they don't work. I also doubt you will be able to charge a 8S-9S pack at 4 amps from a PC power supply.
The good ones are switching at 13.8V while holding 15amps

Jeff your Aurora sure looks good. I love it!

RE: Aurora 60 Build Thread - Electric Power
 

I picked up a PS at CompUSA on sale and added a couple of Radio Shack banana posts and two 10 ohm - 10 watt resistors and I'm getting 12.39v at the terminals. Computer power supplies are switching and provide very smooth and clean DC current; perfect for our battery chargers. Since I doubt I'll ever be charging any of those $600 9A lipos this PS is all I need:

RE: Aurora 60 Build Thread - Electric Power
 

This setup is not in the same league as what Jeff needs for his aurora.
It would take him at least 2 hours to charge 1 pack using all the hardware at full specs

RE: Aurora 60 Build Thread - Electric Power
 

The Astroflight 109 is a better choice than the Triton2 for those gigantic $600 FAI lipo packs. It will charge up to 9 cells in series at 8 amps, but only handles lipos. Bantam has a charger that will handle 12 cells and charge at up to 9.9 amps and also charges Ni** batteries. The Triton is limited to 5 cells in series at 7 amps. Astron makes some good quality switching high amp power supplies in the 10 to 25 amp range that will allow faster charging. Of course, don't forget your gas powered generator to power your power supply!

http://www.astroncorp.com/sps.shtml