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Old Feb 06, 2012, 01:53 PM
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Just finished flying my XL with a much heavier battery -- went from 2200 mah to 3200 mah with a weight increase of nearly 100 gms. Even though it is just over 30 oz. now, the extra weight turned it into a slug. The motor comes down much hotter after lugging the extra weight and I don't get that much extra flight time. The little Tower pro motor (250 watts) just isn't up to the task. What is a good, lightweight motor in the 300+ watt range?
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Old Feb 06, 2012, 02:26 PM
Lawn Dart Specialist
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United States, PA, Williamsport
Joined Jun 2006
391 Posts
Time to share...

Well, I've been lurking here a long time, and it's finally time to share my results.

Specs:
  • All 6mm EPP construction, covered in 1.5mil Doculam
  • Power Up 400 Outrunner
  • APC 6x4E Prop
  • CC Thunderbird 36 ESC
  • HXT 900 servos
  • Turnigy 3S 2200mah 25C battery

This plane has been nothing but trouble!

I completed the construction back before Christmas. On the morning of the planned maiden, I was doing preflight checks in my basement. I walked away to get an allen key, and when I turned back around, the Polaris was on FIRE. Flames were spewing through the top of it. I quickly rushed over, yanked off the hatch, and ripped out the ESC to battery wires with my bare hands, getting a nasty little burn in the process. The motor had shorted and took the ESC with it. Luckily, the damage to the airframe was pretty minimal. It stank to high heaven. The wife was not amused.

Once I finally got replacement parts (shout out to Heads Up RC for no-charge replacement of the motor!) I set out to re-maiden. At that point there was not yet any paint on it and I lost orientation in the early morning light. It's really tough to keep track of an all-white plane. It came down HARD on concrete. EPP is amazing stuff though, and it literally bounced two feet back into the air. There was only very minimal damage to the nose, repaired in a few minutes.

I got smarter, and put some color on it before the next flight. It was pretty out of trim and the CG was off, but the next flight went well enough. Once I got it sorted, it was a whole different animal. It's an excellent cruiser and has a very wide speed envelope. It really grooves; high-alpha landings are a breeze. I love the way it scoots over grass! It's more fun than some R/C cars I've had.

The resilience of the EPP is great. The only downside is the flex. The wings start to bow if you try to pull out of a full-throttle dive. At relaxed speeds it's not an issue. The doculam covering keeps everything water-tight, doubles as the hinges, and ads a lot of stiffness to the floppy foam.

Overall, it's a great design and I think that a on a second build I could make a few revisions that will really make it sizzle.
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Old Feb 06, 2012, 03:14 PM
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Northwest Ohio
Joined Jan 2002
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Quote:
Originally Posted by bob93447 View Post
Just finished flying my XL with a much heavier battery -- went from 2200 mah to 3200 mah with a weight increase of nearly 100 gms. Even though it is just over 30 oz. now, the extra weight turned it into a slug. The motor comes down much hotter after lugging the extra weight and I don't get that much extra flight time. The little Tower pro motor (250 watts) just isn't up to the task. What is a good, lightweight motor in the 300+ watt range?
We offer the Suppo 2810-9 motor and either an APC 8 x 6 or Master Airscrew 8 x 6 three blade prop. I believe it puts out around 325 watts.

Keep in mind the XL is a cruiser and not a speed demon.

Scott

www.ModelAero.com
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Old Feb 06, 2012, 05:46 PM
59 years of RC flying
Daedalus66's Avatar
Canada, ON, Ottawa
Joined Feb 2006
16,015 Posts
Quote:
Originally Posted by bob93447 View Post
Just finished flying my XL with a much heavier battery -- went from 2200 mah to 3200 mah with a weight increase of nearly 100 gms. Even though it is just over 30 oz. now, the extra weight turned it into a slug. The motor comes down much hotter after lugging the extra weight and I don't get that much extra flight time. The little Tower pro motor (250 watts) just isn't up to the task. What is a good, lightweight motor in the 300+ watt range?
That must be a pretty anemic motor or you've got the wrong prop. Which motor exactly are you using and what prop?

The XL at 30oz is a real lightweight and flies great even on the regular Polaris motor (2212-6) . With the 2810-9 that Scott offers it has very good performance at even 40oz.
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Old Feb 06, 2012, 05:57 PM
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United States, CA, Yucaipa
Joined Nov 2008
542 Posts
It's a pretty sweet plane and I might attempt to make one one day... but I just want to note that this thread has 1,416,989 (+ 1 from me right now) views.... making it 2nd after the Blu Baby? 1.5mil views... you know you made something good when it gets that much attention.
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Old Feb 06, 2012, 06:06 PM
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Joined Sep 2006
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Thanks Scott and D66,

Reconsidering things, I am flying in a rather small area so I am probably better off sticking to the lighter batteries and maintaining the extra manuverability of the lighter airframe. If I get the XL to a lake this summer I will probably upgrade the motor. But you're right, it is a cruiser.

Bob
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Old Feb 06, 2012, 08:13 PM
59 years of RC flying
Daedalus66's Avatar
Canada, ON, Ottawa
Joined Feb 2006
16,015 Posts
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Originally Posted by bob93447 View Post
Thanks Scott and D66,

Reconsidering things, I am flying in a rather small area so I am probably better off sticking to the lighter batteries and maintaining the extra manuverability of the lighter airframe. If I get the XL to a lake this summer I will probably upgrade the motor. But you're right, it is a cruiser.

Bob
It still sounds as though you aren't getting the power you should. Here's a video of the XL with the regular 2212-6 motor driving a 6x4 prop on a 2200 battery at about 32oz all up weight. No shortage of power to get off the water there!

By the way, the motor and ESC get no more than slightly warm.

Polaris XL on Water (3 min 26 sec)


With the 2810-9 motor I find it quite lively. Not terrifically fast, but fast enough to be real fun.

Polaris XL Aerobatics (2 min 34 sec)


As you may have guessed, I love this thing!
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Old Feb 07, 2012, 05:41 AM
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Germany
Joined Jun 2010
34 Posts
Hello guys,

I've been reading this thread for quite a couple of weeks now and have started to build my own Polaris now. Actually, I have already built up the fuselage, wings and nacelle, so they are nearly ready to be glued together. But I still need to sand the ailerons in shape a little and would like to know how you guys did that.

As Steve wrote in his manual, the trailing edge should have a slightly tapered shape. So did you sand the entire lower edge or only the ailerons and the tips? I'm afraid then the floats wouldn't fit good enough or at least have a different angle. Some pics would be of great help.
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Old Feb 07, 2012, 07:52 AM
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Crewe England
Joined Nov 2005
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Originally Posted by project80 View Post
Hello guys,

I've been reading this thread for quite a couple of weeks now and have started to build my own Polaris now. Actually, I have already built up the fuselage, wings and nacelle, so they are nearly ready to be glued together. But I still need to sand the ailerons in shape a little and would like to know how you guys did that.

As Steve wrote in his manual, the trailing edge should have a slightly tapered shape. So did you sand the entire lower edge or only the ailerons and the tips? I'm afraid then the floats wouldn't fit good enough or at least have a different angle. Some pics would be of great help.
On my first Polaris I sanded the upper surface of the ailerons only down to 1/8" On subsequent models I have not. There is no decernable difference in flight between the models as far as I can detect.
I try to keep down the amount of sanding as it breaks the surface of the virgin depron making it difficult to regain a surface which will take paint or finishing film well.
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Old Feb 07, 2012, 08:47 AM
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United States, CO, Thornton
Joined Nov 2004
18 Posts
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Originally Posted by Daedalus66 View Post
And my over-reaction to your comment on the video!

I'm interested in your reference to flaps (using dual aileron servos I presume). I haven't found programming the ailerons as flaperons (i.e., drooping them) very helpful. But using them as spoilerons (i.e., raising them about 20 degrees) produces an interesting, stable and controllable steep approach. You just have to be careful to get the speed down first, as otherwise there is a strong pitch-up (which landed me in a tree last fall!). I plan to try programming in a slow deployment of spoileron when I flip the switch.
I have my radio programmed to lower the ailerons about 15 and raise the elevator about 15 when I turn on the landing system. Without turning it on, you can land it easy enough, but you have to come in pretty steep and hot. When I turn on the landing system, it comes in much slower and flatter, but I have to keep the power on, or else it stalls and just falls out of the air. Learned that the hard way, but I'm always up for a learning experience, and the damage was minimal. There seems to be a very fine line where the thing just stops flying, probablly due to the shape of the wing and the fact that it's flat.
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Old Feb 07, 2012, 08:48 AM
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United States, CO, Thornton
Joined Nov 2004
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Quote:
Originally Posted by acecall View Post
On my first Polaris I sanded the upper surface of the ailerons only down to 1/8" On subsequent models I have not. There is no decernable difference in flight between the models as far as I can detect.
I try to keep down the amount of sanding as it breaks the surface of the virgin depron making it difficult to regain a surface which will take paint or finishing film well.
I sanded only the top side only
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Old Feb 07, 2012, 09:14 AM
59 years of RC flying
Daedalus66's Avatar
Canada, ON, Ottawa
Joined Feb 2006
16,015 Posts
Quote:
Originally Posted by project80 View Post
Hello guys,

I've been reading this thread for quite a couple of weeks now and have started to build my own Polaris now. Actually, I have already built up the fuselage, wings and nacelle, so they are nearly ready to be glued together. But I still need to sand the ailerons in shape a little and would like to know how you guys did that.

As Steve wrote in his manual, the trailing edge should have a slightly tapered shape. So did you sand the entire lower edge or only the ailerons and the tips? I'm afraid then the floats wouldn't fit good enough or at least have a different angle. Some pics would be of great help.
Just round the edges. It makes no discernible difference aerodynamically. In fact, you can leave everything square and it will fly fine. It's only a matter of appearance. (And you're right to be concerned about fitting the floats. Put them on before you start sanding in that area.)

The one place where tapering matters is on the vertical tail, where you want a nice rounded nose and tapered rear part so the high speed air from the prop can flow smoothly over it and there no abrupt step in front of the rudder.

Round the top corners of the fuselage slightly but leave the bottom corners square (i just take the very corner off, so when I add the duct tape to protect the bottom it folds neatly over the edges).

My philosophy of Depron building is the less sanding the better on flat areas. Wipe off the glue while building and you shouldn't need to sand. In particular, don't sand the wings as you will make nasty grey smudges from the CF spars!
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Old Feb 07, 2012, 09:24 AM
59 years of RC flying
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Canada, ON, Ottawa
Joined Feb 2006
16,015 Posts
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Originally Posted by justinspanier View Post
I have my radio programmed to lower the ailerons about 15 and raise the elevator about 15 when I turn on the landing system. Without turning it on, you can land it easy enough, but you have to come in pretty steep and hot. When I turn on the landing system, it comes in much slower and flatter, but I have to keep the power on, or else it stalls and just falls out of the air. Learned that the hard way, but I'm always up for a learning experience, and the damage was minimal. There seems to be a very fine line where the thing just stops flying, probablly due to the shape of the wing and the fact that it's flat.
My comments about gliding applied of course to the situation without flaps or spoilers. Their purpose is to add drag and they will therefore require either a steep approach or power on. That way, you can make the approach as flat as you want.

The delta configuration is inherently low drag at low angles of attack and high drag at high angles. So it gives you a great deal of control without using flaps or spoilers. The standard Polaris without any flap action is easy to land, power on or power off, provided you understand this.
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Old Feb 07, 2012, 09:55 AM
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Crewe England
Joined Nov 2005
142 Posts
I always fly my Polaris onto the ground just like a modern fullsize airliner rather than glide it down like an engine in the nose tractor prop job. The Polaris does this remarkably well and it looks good because it doesn't come to a full stop after touch down, at this point I let it roll straight for a few yards to reduce speed before taxiing to the pits. Here in the UK we mostly fly in gusty winds of 10+ knots or more (not by choice) and this method of landing is the safest in these conditions.
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Old Feb 07, 2012, 09:58 AM
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United States, CO, Thornton
Joined Nov 2004
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Originally Posted by Daedalus66 View Post
My comments about gliding applied of course to the situation without flaps or spoilers. Their purpose is to add drag and they will therefore require either a steep approach or power on. That way, you can make the approach as flat as you want.

The delta configuration is inherently low drag at low angles of attack and high drag at high angles. So it gives you a great deal of control without using flaps or spoilers. The standard Polaris without any flap action is easy to land, power on or power off, provided you understand this.
Perfectly said. This is my first delta plane, so I'm still in the process of learning the nuances of flying it. I also like to tinker with stuff just to see what happens (flaps,spoilers, etc.).

I usually like to mix a little rudder in with the ailerons, but after about an hour of flying this plane, I found that it seemed to fly better when I didn't mix in any rudder. Anybody else have any experience with this?
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