Motors :

Rctimer.com

Banggood

Even eBay if above don't have ....

Nigel

Gentlemen,, I have had regular Polaris and XL (RIP), I also have Northstar, Skipper and XL,
Now I have some projects in my head and would like to pic your brains regarding weight !
What is your experiance regardng increased weight,, lets say 20, 50, 100% over the designed criteria ??,, I intend to do some tests but would like to be a bit prepared because my aerodynamical knowledge is a bit limited in this respect...//Rob

I know the standard can carry quite a bit more weight and I was estimated about 30% overweight on my first ... it flew perfect.

I then on subsequent builds lightened them.

Nigel

Yes that is my experiance aswell,, My fist PolarisXL was at 1.6Kg and flew wery well,, A Skipper I have I use to put a GoPro on the CG Think its about 2-300gram more (about +25-35%),, Except from a higher stallspeed,, what more is to be considered from an aerodynamic point of view.. ?? //Rob

The ideal weight is around 20oz, but to achieve it you have to use a battery of about 1500 mAh. Most of us use a 2200 and the weight goes up to 22-24oz (25% increase). The model still flies very well

The heaviest I have flown at was 30oz (with ballast), or 50% above design weight. The model was no longer the light and lively Polaris I had come to love, though it still flew well. I would not want to go higher.

If you want best handling, keep it light. If you are planning FPV with heavy equipment, it can handle around 50% over weight.

One thing to keep in mind is that as the weight increases, the vulnerability to damage in a hard landing increases.

Originally Posted by Daedalus66

The ideal weight is around 20oz, but to achieve it you have to use a battery of about 1500 mAh. Most of us use a 2200 and the weight goes up to 22-24oz (25% increase). The model still flies very well

The heaviest I have flown at was 30oz (with ballast), or 50% above design weight. The model was no longer the light and lively Polaris I had come to love, though it still flew well. I would not want to go higher.

If you want best handling, keep it light. If you are planning FPV with heavy equipment, it can handle around 50% over weight.

One thing to keep in mind is that as the weight increases, the vulnerability to damage in a hard landing increases.

Like a big & heavy object is going to get more damaged.. Yes the greater mass the more damage,, I am thinking more about aerodynamics and wing load,, Polaris flat wing versus a symetrical airfoil like Northstar or assymetric like the Skipper,, There must be significant differences that will reveal at the extremes.. Just guessing.. ??
//Rob

Typically, a flat plate wing section generates about the same lift at moderate angles of attack but higher drag at high angles of attack than a symmetrical section. A flat-bottom or semi-symmetrical section will generally produce more lift that a flat plate.

Of course it takes significantly more power to haul a model at high angle of attack. If you don't have enough power, you can find the model flying at full power "on the back side of the curve" where more lift is needed but increasing the angle of attack increases drag. The only way out is down. If you have enough height, you can put the nose down and pick up speed to get out of the trap.

One of the biggest effects with a flat plate wing in fact is not so much the drag but the turbulent air that gets created as the angle of attack increases. Because you do not have a curved rounded L/E which has a large transition range for clean airflow split - the flat plate has a very sharp and narrow range of such transition and on even a low angle of attack can create seriously turbulent flow over top of the wing.

Watch a modern day fighter with its thin wing when it pulls those G's in turns / pitch up ... the condensed vapour trails that come of the wings L/E .. he and your model need the same solution ... POWER.

Nigel

Originally Posted by solentlife

One of the biggest effects with a flat plate wing in fact is not so much the drag but the turbulent air that gets created as the angle of attack increases. Because you do not have a curved rounded L/E which has a large transition range for clean airflow split - the flat plate has a very sharp and narrow range of such transition and on even a low angle of attack can create seriously turbulent flow over top of the wing.

Watch a modern day fighter with its thin wing when it pulls those G's in turns / pitch up ... the condensed vapour trails that come of the wings L/E .. he and your model need the same solution ... POWER.

Nigel

Mmmm,, I heard many years ago from a teacher that "one can make anything fly,,, even a barn door" he ment the same thing,, enough power !!
I suppose that aair foil will carry more load,, any ideas about how much more before it falls out of the sky ??? Thinking about same pre condition air speed for flat, semi and assymetrical air foils //Rob

Originally Posted by solentlife

One of the biggest effects with a flat plate wing in fact is not so much the drag but the turbulent air that gets created as the angle of attack increases. Because you do not have a curved rounded L/E which has a large transition range for clean airflow split - the flat plate has a very sharp and narrow range of such transition and on even a low angle of attack can create seriously turbulent flow over top of the wing.

Watch a modern day fighter with its thin wing when it pulls those G's in turns / pitch up ... the condensed vapour trails that come of the wings L/E .. he and your model need the same solution ... POWER.

Nigel

It's that turbulence that causes the drag. There are only two basic forces at work: lift and drag. Plus of course gravity and thrust.

Originally Posted by Daedalus66

It's that turbulence that causes the drag. There are only two basic forces at work: lift and drag. Plus of course gravity and thrust.

Thank you ... because the transition from clean lift to turbulent is the basis of the drag and rest.

I can remember way back in early 80's when a guy published a 3/16th ... 1/4" flat plate F15 mode with 20 Glow up front in RCM&E... people I can remember laughing on the flight lines till they saw what it could do. It wasn't fast ... it had a nasty tendency to stall abruptly if power wasn't kept up... BUT it flew and I would put it as one of the models that changed our way of thinking ...

Nigel

Steve, the designer of the Polaris has some interesting things to say about flat plate airfoils:

There is one other point I'd like to make about flat plate airfoils--while they work very well on foamy parkflyers like the Polaris, they do not work well on larger heavier models. That's largely because of scale effect. The performance of most airfoils is degraded at low Reynold's numbers due to viscosity effects, and thicker or more-cambered airfoils generally suffer greater penalties.

The thin flat plate section is unique in that it is not affected much by scale, however, it can generally only achieve a max lift coefficient of 0.7--at any scale. A symmetrical airfoil can achieve a max lift coefficient of 1.2.

https://www.rcgroups.com/forums/show...ostcount=20160

This point is very important for the question raised by the OP, which concerned the maximum weight of a Polaris. I should have stressed a little more clearly that I think 30oz (50% over design weight) is getting towards the limits and the low lift coefficient of a flat plate is an important aspect of why.

EDIT
This is the detailed discussion of flat plate I was thinking of:

https://www.rcgroups.com/forums/show...postcount=9949

Originally Posted by Daedalus66

Very neat. Please tell us more. Do you have videos?

I had an idea for a Polaris bipe but never followed through.

No, I don't have video, have not joined that generation yet. But moot anyway as I have not flown it. Although built some time ago I have not been to my field for a while--in fact almost 2 years since I have flown, although I do keep building. Distance and time the issue. My club hopes to have a second field open this summer that is only 5 miles from my house (instead of 35 in Wash DC traffic), so am hoping to change that this year.

Can say it is 29oz without the battery, 450 sq inches of wing, which gives it about 12oz/sq ft flying weight for an 8oz battery...Pete M

Is there anything on the CD that comes with the Polaris Seaplane besides the pdf file that is on the Model Aero website?

I ordered one & the cd doesn't work.

Originally Posted by gman350

Is there anything on the CD that comes with the Polaris Seaplane besides the pdf file that is on the Model Aero website?

I ordered one & the cd doesn't work.

There may be some pictures and plans of other models (I haven't got a recent one) but nothing you need to build Polaris. The Construction Guide is it.

http://modelaero.com/pdf/Model%20Aer...on%20Guide.pdf