SMALL - espritmodel.com SMALL - Telemetry SMALL - Radio
Reply
Thread Tools
Old Dec 16, 2012, 10:16 PM
Registered User
Deadstick 8409's Avatar
Joined May 2010
1,042 Posts
Quote:
Originally Posted by justj View Post
I sure wouldn't trust running that much current through 20 ga! It's rated current carrying capacity is 11 amps. Sooner or later there will be consequences.

At the very least, a performance penalty. I am sure there is a voltage drop. I imagine it might not be too difficult to pull some bigger wire through using the existing wires.
Deadstick 8409 is online now Find More Posts by Deadstick 8409
Reply With Quote
Sign up now
to remove ads between posts
Old Dec 16, 2012, 10:33 PM
Registered User
Northwest Ohio
Joined Jan 2002
2,680 Posts
Quote:
Originally Posted by justj View Post
I sure wouldn't trust running that much current through 20 ga! It's rated current carrying capacity is 11 amps. Sooner or later there will be consequences.
The recommended setup runs 25 amps wide open on 3S and 29 amps on 4S static. I have run both packs through it at near full throttle with no issues. Additionally, I have tested performance between these wires and 14 gauge wires. There is a 4% drop in wattage between these wires and 14 gauge wires. Hardly significant. Besides the fact that the 4% loss of wattage will probably be offset by the 1 1/2 oz. savings in weight.

Please explain your statement "sooner or later there will be consequences". What will change from pack one to pack 20? Or 50?

Scott

www.ModelAero.com
Model Aero is offline Find More Posts by Model Aero
Last edited by Model Aero; Dec 16, 2012 at 11:01 PM.
Reply With Quote
Old Dec 17, 2012, 06:04 AM
Registered User
Aviefly's Avatar
United Kingdom, Aviemore
Joined Feb 2005
3,244 Posts
I ran 18awg in my standard Polaris no problems at all. I would have chosen a larger size for this given the choice but I can't see it causing any long term problems. The only issue I could see is heat build up damaging the insulation but I can't see that happening in the application. Maybe if you're pulling 30-35A for hours at a time but that's not going to happen here. I'm amazed at the 1.5oz weight saving between 14awg and 20awg, I think I'd take the risk for that.

Scott, thanks for looking into shipping to Europe. That price works out pretty good for airframe, motor, esc and servo's shipped, getting hit for tax would make it a little more rough but I think I'll take the gamble once all the Christmas expences are out the way.
Aviefly is offline Find More Posts by Aviefly
Reply With Quote
Old Dec 17, 2012, 06:22 AM
Registered User
justj's Avatar
United States, AZ, Chino Valley
Joined Feb 2012
417 Posts
Consequences

Good Morning Scott
High currents through small wires generate heat, 3 wires 'bundled' in a confined space increases the heat generated beyond simple addition http://www.interfacebus.com/Componen...uide_line.html gives a guide to all things related to wire size, insulation type and bundling effects. While the wires may never fail, the constant heating of the vertical fin will have some consequences. How much heat + stress during aerobatics = hard to explain loss of control. I wouldn't go so far as to use #14 but I would use #16 as it doubles the rated current capacity to near 50% of WOT.
justj is offline Find More Posts by justj
Reply With Quote
Old Dec 17, 2012, 10:02 AM
Registered User
Northwest Ohio
Joined Jan 2002
2,680 Posts
Quote:
Originally Posted by justj View Post
Good Morning Scott
High currents through small wires generate heat, 3 wires 'bundled' in a confined space increases the heat generated beyond simple addition http://www.interfacebus.com/Componen...uide_line.html gives a guide to all things related to wire size, insulation type and bundling effects. While the wires may never fail, the constant heating of the vertical fin will have some consequences. How much heat + stress during aerobatics = hard to explain loss of control. I wouldn't go so far as to use #14 but I would use #16 as it doubles the rated current capacity to near 50% of WOT.
All I can say is in real world testing this is a non issue. Even on 4S at full throttle for a couple minutes at a time, the wires do not get hot. And no one is going to be flying this plane like that anyway. The average current in normal flying will be closer to 15 amps.

Scott

www.ModelAero.com
Model Aero is offline Find More Posts by Model Aero
Reply With Quote
Old Dec 17, 2012, 10:03 AM
Registered User
Joined Apr 2008
949 Posts
Quote:
Originally Posted by justj View Post
I sure wouldn't trust running that much current through 20 ga! It's rated current carrying capacity is 11 amps. Sooner or later there will be consequences.
Hi justj,

Regarding of the thin gauge wire, I have done the testing flight with 4S 2600mAh 35C more then 30 flights (also 80% on full throttle - 4mins flight and the weather temp. is on 28 degree ). The thin gauge wire is no problem also just warm not hot.. Also the plane ventilation is good enough for ESC / Battery cooling that should be better for related motor extension cable. My testing plane is still very well Please don't worry..
Thin gauge wire can be reduced some weight..
The following is my test plane flying video link on July. for sharing with you.
http://v.youku.com/v_show/id_XNDI3ODU2OTI4.html

Thanks,
Tim
Tim Wan is offline Find More Posts by Tim Wan
Reply With Quote
Old Dec 17, 2012, 05:44 PM
60 years of RC flying
Daedalus66's Avatar
Canada, ON, Ottawa
Joined Feb 2006
16,967 Posts
Ultras Arrived

Just got back from picking up the Ultras (one for a friend). First mistake I made was leaving a car seat in the back of my compact wagon. It was a squeeze!

But we made it home safely and here's what it looks like.
Daedalus66 is online now Find More Posts by Daedalus66
Reply With Quote
Old Dec 17, 2012, 06:59 PM
Registered User
Northwest Ohio
Joined Jan 2002
2,680 Posts
Glad to see the kits arrived intact, although the one box looks like it took a hit.

Scott

www.ModelAero.com
Model Aero is offline Find More Posts by Model Aero
Reply With Quote
Old Dec 17, 2012, 07:05 PM
60 years of RC flying
Daedalus66's Avatar
Canada, ON, Ottawa
Joined Feb 2006
16,967 Posts
Regarding the gauge of wire, I'll be interested to see how it works out when I get mine in the air. I've long believed that the usual recommendations for motor wires are much too conservative. I use 18g speaker wire for the regular Polaris, which runs 20A in the air at WOT (about 3A less than static). There is no sign of even getting warm. So 20 gauge is not too much of a stretch. And it saves at least an ounce compared to 14 gauge which is sometimes recommended.

One thing to keep in mind is that we are dealing with three wires, not two, So 25A to the ESC gets reduced to the equivalent of about 16A (2/3) to the motor in terms of average heating effect. Also, take a look at the size of motor wires.
Daedalus66 is online now Find More Posts by Daedalus66
Reply With Quote
Old Dec 17, 2012, 11:02 PM
60 years of RC flying
Daedalus66's Avatar
Canada, ON, Ottawa
Joined Feb 2006
16,967 Posts
Quote:
Originally Posted by Model Aero View Post
Glad to see the kits arrived intact, although the one box looks like it took a hit.
Scott
www.ModelAero.com
That's the one I opened and everything inside was fine.

I'm really impressed with how the parts go together. The wings are a nice tight (but not too tight) fit into the fuselage and the tail likewise into the fin. The finish is very good as you can see in the picture.
.
It looks as though the whole thing should go together very easily. I hope to have some time to work on it tomorrow and will report on the assembly process. It looks as though there should be ample room for the battery and receiver (I'm thinking of an AR400 as nice and compact with lots of antenna separation), and the servo locations are all provided for.

The cooling for the ESC should be fully adequate, though I plan to smooth out the intakes for better airflow, an easy job (because of the molding process, they are not fully open). The exit looks ample. I would guess that the total intake area after that will be about like one of the plastic spoon scoops I use for a vent on the regular Polaris and XL. By the way, I once experimented with various vent sizes and found that one spoon in and one spoon out was just right -- more made hardly any difference in ESC temperature in the air.

So first impressions of Ultra are really positive. I can't wait to get it in the air. But it may take a while as the weather is none too promising. Today we had freezing rain. I'm waiting for some nice snow for the initial flights. Perhaps by Christmas.
Daedalus66 is online now Find More Posts by Daedalus66
Last edited by Daedalus66; Dec 18, 2012 at 10:59 AM.
Reply With Quote
Old Dec 19, 2012, 12:52 PM
Crash & Burn
rmgmag's Avatar
Glastonbury, CT
Joined Nov 2004
2,503 Posts
It looks like there's the option to use the blacked out cockpit or a pilot? Glad to see it, since I was planning on painting the canopy black, now I don't have to. Can't wait for mine to arrive. I think it's going to ship in 3-5 days.

Bob
rmgmag is offline Find More Posts by rmgmag
Reply With Quote
Old Dec 19, 2012, 01:29 PM
Registered User
Northwest Ohio
Joined Jan 2002
2,680 Posts
Quote:
Originally Posted by rmgmag View Post
It looks like there's the option to use the blacked out cockpit or a pilot? Glad to see it, since I was planning on painting the canopy black, now I don't have to. Can't wait for mine to arrive. I think it's going to ship in 3-5 days.

Bob
The cockpit is painted black, with a clear canopy over the top. The entire assembly functions as the battery hatch and is attached with magnets.

Scott

www.ModelAero.com
Model Aero is offline Find More Posts by Model Aero
Reply With Quote
Old Dec 19, 2012, 01:36 PM
Crash & Burn
rmgmag's Avatar
Glastonbury, CT
Joined Nov 2004
2,503 Posts
OK, thx. It was hard to tell from the picture. I guess I'll be paining it after all, just personal preference,no big deal.
rmgmag is offline Find More Posts by rmgmag
Reply With Quote
Old Dec 19, 2012, 05:01 PM
Registered User
Northwest Ohio
Joined Jan 2002
2,680 Posts
Quote:
Originally Posted by rmgmag View Post
OK, thx. It was hard to tell from the picture. I guess I'll be paining it after all, just personal preference,no big deal.
But if you paint the canopy black, how will the little fella see where he's going??

Scott
Model Aero is offline Find More Posts by Model Aero
Reply With Quote
Old Dec 19, 2012, 07:19 PM
We shall serve the Lord
kingsflyer's Avatar
United States, TX, Kingsland
Joined Sep 2005
5,157 Posts
My Ultra arrived today in great shape. Wonderful packing job! Parts looked excellent!

Now that I've started my build, here are a few of my first impressions ----

I'm glad they included a pilot figure, but he seemed a little small to me, so I cut down a Horizon T-28 pilot for mine. When I was fitting my pilot, the paint on the cockpit area began to flake off on the edges. I first tried to use a sharpie, but it only made a larger area flake off. I ended up shooting some black enamel over the area and its all better now.

I was working on mounting the motor and found a couple of items. NOTE -- I'm not using the recommended motor, so some of these issues may not apply if you use the Model Aero motor.

First, my motor shaft extended out behind the motor mount too far and it hit the plywood motor pylon brace. Rather than cut out the plywood, I shortened my motor shaft.

Second, I measured the distance from the firewall to the end of the plastic cowl and found that I needed 1-7/8" (48mm) for the prop to clear the front of the cowl. For my motor, I needed to add 3/8" spacers for the prop to clear, or I guess I could have cut 3/8" off the cowl.

Third, I tested the ESC extensions to confirm they were adequate for my motor. My motor will use a 4-cell battery and an 8x6E prop to produce about 400 watts. For my test I used a 65C 5000 mah 4-cell battery at about 80% capacity. I chose this big pack so that it would maintain voltage and wattage even under heavy loading. Here are the numbers without the extensions -- 14.6 min pack Voltage, 28.2 max Amps, 415 max Watts. With the extensions, the numbers were -- 14.6 min pack Voltage, 25.1 max Amps, 371 max Watts. The extensions never even warmed up, but it looks like they will cost me about 10% power reduction. I'll still have over 150 watts per pound, which should be just fine.

So far, I'm very happy with my purchase. Now I need to get back to work.

McD
kingsflyer is offline Find More Posts by kingsflyer
RCG Plus Member
Latest blog entry: LEDs on my T-28
Reply With Quote
Reply


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Sold Complete Power set up for a Aero Models Aqua Cat or Polaris RTflyboy Aircraft - Electric - Power Systems (FS/W) 1 Dec 08, 2012 06:52 PM
For Sale cassini aero models usa p 51d mustang 120 arf asteroidguy Aircraft - Fuel - Airplanes (FS/W) 2 Mar 17, 2012 06:21 PM
Discussion Model Aero Polaris Seaplane Auction Model Aero Hot Online Deals 1 Mar 11, 2012 12:28 PM
For Sale cassini aero models usa p 51 mustang 120 arf asteroidguy Aircraft - Fuel - Airplanes (FS/W) 0 Feb 22, 2012 01:14 PM