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Mar 13, 2019, 03:37 PM
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warhead_71's Avatar
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Looking at different motor options...

Empty airframe: 1300g

Motors:
Tomcat G10 1150kv: 110g
Turnigy G10 810kv: 140g (not in stock)
RimFire .15 1200kv: 102g ($$$)
Eflite Power25 1000kv: 190g ($$)

40-50A ESC w/BEC: 35-45g

6x 9gr servos: 54g

RX: 12-16g

3S 2200mah lipo:188g
3S 3300mah lipo:256g

Tomcat G10 1150kv and 2200 lipo, you'd be at 1699g (59.9oz)
18 oz/sf (56.2g/dm^2)
9.8 WCL
prop: 11x6 APCe
battery load: 17.4C
time: 4.9min
power: 400.5watts
draw: 38.25amps
static thrust: 65oz (1843g)
speed: 55mph (89kmh)

Turnigy G10 810kv and 2200 lipo, you'd be at 1729g (60.1oz)
18.03 oz/sf (56.2g/dm^2)
9.9 WCL
prop: 12x8 APCe
battery load: 13.9C
time: 5min
power: 324watts
draw: 30.5amps
static thrust: 68.3oz (1937g)
speed: 55mph (89kmh)

RimFire .15 1200kv and 2200 lipo, you'd be at 1741g (61.4oz)
18.4 oz/sf (56.2g/dm^2)
10.1 WCL
prop: 11x6 APCe
battery load: 19.2C
time: 4.6min
power: 439watts
draw: 42.2amps
static thrust: 68.7oz (1937g)
speed: 57mph (91kmh)

Eflite Power25 1000kv and 3300 lipo you'd be at 1861g (65.7oz).
19.7 oz/sf (60.1g/dm^2)
10.8 WCL
prop: 11x7 APCe
battery load: 12C
time: 8min
power: 410watts
draw: 38.25amps
static thrust: 73.3oz (2078g)
speed: 60mph (97kmh)

Looks like whatever motor you use, on 3S you aren't going to wring a lot from a bigger motor unless you use a huge prop and draw lots of amps = less flight time. Not very efficient and adds unnecessary weight. But they all give you better than 1:1 thrust/weight... so IMO it becomes a matter of trying to keep your wing-loading low. If you can run of a single 2200mah 3S instead of 3300 or 2x 2200 then that would go a long way to keeping the weight low. I only ran mine on 2 because I needed the nose ballast... but I didn't have floats either.

And the HeadsUp Power Up 15 1000kv or Gforce 15 I think will be right in the sweet spot.
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Mar 13, 2019, 03:55 PM
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Beaver power


Wow,
Thanks so much, it's like having my own personal engineer encyclopedia! Which helps a lot as I,m still trying to figure out all the electric jargon, my old days of 72mhz and glow engines are nothing like what's out there now.
I probably shouldn't have hot wire cut solid foam wings and made my float mounts out of aluminum and made solid foam floats, would have saved a lot of weight otherwise. I tend to overbuild everything bad habit when it comes to planes.
I talked to the guy with the eflite ( text) but the shipping here may be an issue so I,ll wait on his response and then maybe go with one of your suggestions instead.
Your have been more than helpful , very much appreciatted!
Mar 14, 2019, 10:41 AM
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Yeah I wonder how much your solid foam floats weigh. The solid wings are not adding a whole lot of extra foam because they are so thin anyway. But the floats sure are. Might be worth weighing them sepparately to see how much they add. I'm guessing they would be 1/3 the weight if you built them up instead. The extra weight is really penalizing you and forcing you to go with a bigger/heavier powertrain. I wonder even how well it will ROW with the extra water displacement. It wouldn't take longer than an afternoon to build-up new ones for it.
Last edited by warhead_71; Mar 14, 2019 at 11:33 AM.
Mar 14, 2019, 11:30 AM
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You might also consider adding wing fences and "wingtip droops" to increase lift and aileron control at low speeds, reduce stall speed. On the full-scale they claim this "STOL kit" adds 30% lift, even without the use of flaps.

The fences would be easy to add... scale the pattern and make 4 of them from old credit card/gift cards/etc. I would give them a few "teeth" on the inside radius so they actually bite into the wing before you glue them.

Wingtip droops would take a bit of careful modification to keep both sides equal, but I think you could cut them from "meat tray" foam that already has a preformed curve to it.
Mar 14, 2019, 12:41 PM
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Once again all great ideas! I almost feel like the glow 15 size ( eflite electric replacement motor) might still be underpowered, but of course not sure. I,m also thinking of putting a small pad on the top surface of the wing and through bolting my wing struts as they are just held on by small screws in the plywood underneath, I can see me pulling a coup,e of g's with the extra weight of the floats and ripping them right out. But of course I don't want to turn it into a submarine, lol! I think the droop tips I can shape out of solid foam and add to the existing tips maybe. I,m really not clear on how the wing fences work but I do see them on full scale around here a lot. Originally I was going to make foam plugs and then make the floats out of fiberglass but decided I was more interested in going flying than spending all my time building. This whole thing started as a result of getting snow ( a very big rarity where we are in these Islands) and not wanting to do anything much outside. lol!
Mar 14, 2019, 01:44 PM
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So you got me thinking so I pulled the floats off to see what they weigh, with the aluminum spreaders they are about 360 grams. I also have light plywood reinforcement inside them to attach the aluminum spreaders to.
Mar 14, 2019, 01:46 PM
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The empty airframe without floats is 900 grams
Mar 14, 2019, 01:59 PM
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STOL kit


This is the plane I sort of copied the leading edge of the wing on the STOL kit is apparently part of the increase in lift. This particular beaver is owned by the Engineering firm my son works for.
Mar 14, 2019, 04:17 PM
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warhead_71's Avatar
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Nice livery!

One more option for the motor... on mine I ran the DT750 (I thought it was a Donkey brand back then but maybe I'm mistaken). They are bullet-proof and super efficient. Since then they came out with the more powerful DT850 (D4023 850kv) which you can run on 3S with a 11x7 or 12x6.

60 oz. thrust (1700g) @ 29 amps, apc 12 x 6e, 2200 mah 3s @ 300 watts Check Dr. Kiwis tests.

https://hobbyking.com/en_us/d4023-85...ner-motor.html $15
Last edited by warhead_71; Mar 14, 2019 at 04:24 PM.
Mar 14, 2019, 05:34 PM
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I love the price! Isn't that the same Moore as in the fly zone DHC-2?
Mar 14, 2019, 10:22 PM
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Looks like it.
Mar 15, 2019, 07:45 PM
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Hi Warhead
I think I may finish building my foam cutter and hot wire the wings from pink solid foam. Do you forsee any problems with that idea?
I will cut channels for the servo wires, CF Arrowshafts and sticks to hold wings together. Finally, will then either cut pink foam fillers for the channels where needed or use low expansion foam to fill the channels then trim when it sets up solid. I am also looking at paper covering all and then acrylic Rustoleum paint and pen striping from my nearby Canadian Tire.
Mar 15, 2019, 09:53 PM
Registered User

Wings


Your planning on doing pretty much exactly what I did , hot wired the wings , I don't think the weight for the wings will be an issue but having said that , mine with floats is plenty heavy. I covered mine with Kraft paper and painted it with tremclad.
You can look back in the thread and see my weight measurements. My floats came in at 1/3 the airframe weight that's a lot.
Means I'll end up with a AUW of just under 4 lbs with batteries and electronics. Can't take credit for some of the calculations as Warhead figured it all out. But the Hotwire wings I believe will be ok ( only in my opinion) haven't flown mine yet?


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