Polaris Seaplane Parkflyer - Page 1879 - RC Groups
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Jan 11, 2018, 09:04 PM
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elewon's Avatar
Quote:
Originally Posted by rkrishnan
scootracer,
I am starting my first time Polaris build with DTFB - Did you take the paper off and add add just a bit of colored packing tape in your build ? I can't quite tell from looking at the pictures.
Hi there, not sure if you made progress on your build. Look at post #26522 - my DT FB polaris. I did not remove paper so not water friendly but take off is easy on grass field.

I still have the plane after over 2 years, although nose section is in bad shape. I find landing the plane a bit challenging, specially during flare right before touch down. Even slightest up elevator will result in plane flaring up way too much and then plonking down on ground. I guess this is intended on water but hard ground isn't that kind with the nose section.

The plane is lot of fun otherwise.
Last edited by elewon; Jan 12, 2018 at 08:03 PM.
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Jan 12, 2018, 06:58 AM
Registered User
Try adding some exponential to the elevator control. Double check the actual amount of throw called for.
I found that flairing the plane is not needed, it settles in by itself.
Jan 12, 2018, 07:08 AM
Youtube channel : solentlifeuk
solentlife's Avatar
Quote:
Originally Posted by jollyroger
Try adding some exponential to the elevator control. Double check the actual amount of throw called for.
I found that flairing the plane is not needed, it settles in by itself.
Agreed .... due to shape of nose and the generous upsweep .. I never flare ... just nose up a touch due speed and glide on in ... snow, grass, concrete, water ...

Nigel
Latest blog entry: The egotistic nature of some !
Jan 12, 2018, 10:28 AM
Registered User
One other thing: Do not use the supplied pushrods that come with the kit. replace them with 2-56 pushrods. The ones that come with the kit are too flimsy and are easily bent and stall with very little force.
Mine crashed because the elevator could not respond properly due to the flimsy pushrod.
When I build a new one all pushrods will be replaced with 2-56.
Jan 12, 2018, 11:15 AM
Youtube channel : solentlifeuk
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I generally use bicycle spokes .... unless its a light model that really needs light rods. But even then you can use CF rods with good ends and have stiff rods with no weight literally.

A trick I have used when I have found kit rods flex in flight. I have taken thin CF rod and CA'd with small bits of paper tape to the thin flexing control rod to stiffen ... it only needs a section around the middle to prevent the bowing of the rod.

Another way is to get old servo horn and drill out a larger hole ... pass rod through it and glue end into structure to provide a guide ...

Nigel
Last edited by solentlife; Jan 12, 2018 at 11:22 AM.
Jan 12, 2018, 12:16 PM
60 years of RC flying
Daedalus66's Avatar

Polaris Seaplane Parkflyer


Quote:
Originally Posted by jollyroger
Try adding some exponential to the elevator control. Double check the actual amount of throw called for.
I found that flairing the plane is not needed, it settles in by itself.


On some models, the problem IS the expo.
The basic issue in ballooning is that the elevator control rate is simply too high for a smooth flare. If you try to cure this by adding expo you create a situation in which the expo makes the first part of the elevator action quite gentle, but beyond 50% up elevator the rate increases very quickly. If you can restrain your use of elevator to less than 50% on landing, this approach works, but if you pull more than that you get serious ballooning — or worse.
I find that using low rates for landing is a far more satisfactory way to go. I now typically set high rate (100%) elevator to give about 1/2” throw on the up side, with low rate set to about 60%. This low rate gives plenty of control for takeoff, flying around smoothly and landing in low rate without needing a lot of expo — I generally use 20% or so. The result is that elevator action remains pretty consistent over the whole range, because as you pull back gradually for the flare the moderate expo compensates for the reduced elevator power as the model slows down.
For high rate up elevator and high and low aileron I generally us 35% expo.
By the way, on Polaris I use 0% expo on down elevator and also use more throw than on the up side.
EDIT
If the model “settles in by itself” that means you got the flare right. That’s how you’re supposed to land — coming back on elevator gradually to raise the nose just a little and allow the speed to bleed off. If you don’t come back on elevator, it will touch down too fast and skip back up.
Last edited by Daedalus66; Jan 12, 2018 at 12:21 PM.
Jan 12, 2018, 12:32 PM
60 years of RC flying
Daedalus66's Avatar

Polaris Seaplane Parkflyer


Quote:
Originally Posted by jollyroger
One other thing: Do not use the supplied pushrods that come with the kit. replace them with 2-56 pushrods. The ones that come with the kit are too flimsy and are easily bent and stall with very little force.
Mine crashed because the elevator could not respond properly due to the flimsy pushrod.
When I build a new one all pushrods will be replaced with 2-56.

The pushrods supplied are perfectly adequate and have enough flex to accommodate the slight bending needed to allow a small diameter piece of tubing to be used to keep the water out. The tubing acts as a support to ensure there is no excess bending.

Of course, if you change the pushrod setup so there is no support in the middle, you will need to go to somewhat heavier wire (or CF). But there’s no need for 2-56 threaded rod or bicycle spokes. That’s what we used to use on 5lb models with a .40 IC engine on the front and servos the weighed 40g each.

Nigel’s suggestions for stiffening the rods or adding a guide make a lot of sense where they can be used. The Mako for example, uses relatively thin CF for pushrods with guides midway.
Jan 12, 2018, 12:46 PM
Youtube channel : solentlifeuk
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Personally I avoid the 'holes' into fuselage by having wing mounted servos.

The Rudder and elevator servos are mounted high on the pylon.

Combination of these gives me watertight and short control setups...

Never needed to add waterproofing to the wing servos ... I fit and then use Vinyl Emulsion paint on the bottom all over up to 'tide-mark' - same as used in bathrooms ... that seals everything.

Nigel
Latest blog entry: The egotistic nature of some !
Jan 12, 2018, 02:52 PM
60 years of RC flying
Daedalus66's Avatar

Polaris Seaplane Parkflyer


I’ve tried all ways with various water planes, and properly done all of them worked about equally well. The standard setup in my Polaris #1 worked well for 8 years (till I pulled out a little low and turned a figure 8 into a figure 9). I used the same configuration with numerous other members of the Polaris family with very satisfactory results. In different models, on the other hand, I have used tail-mounted servos and wing mounted ones.
I agree that splashing is not a problem, but always take the precaution of sealing seams in the case and around the cable. Also a little Vaseline round the output shaft.
The only problem I have ever had with a servo quitting because of water occurred in unusual circumstances. It was the rudder servo in a Polaris XL, mounted upside down through the radio deck as usual. I made three mistakes: (1) I didn’t seal around the cable exit, (2) I didn’t leave the rear of the radio compartment open as I normally do, (3) I left the model sitting tail-down for two weeks. Next time I went flying, the rudder went hard over soon after takeoff and the model crashed. On removing the rudder servo, I found it had half filled with water that had been trapped in the space around it. After fairly minor repairs and drying out and sealing the servo the model served two more years before succumbing to pilot error (one of my students).
Anyway, the lesson here is that there are several ways to skin a cat, but each introduces its own potential for failure.
Jan 12, 2018, 03:05 PM
Youtube channel : solentlifeuk
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I know there has always been a modicum of opposition to my 'changes' to Steve's Polaris. I accept that.

But will say this .... I have a number of waterplanes ... and none have suffered servo failures by any reason other than stripped gears ... and funny enough with the Polaris - its always been the rudder ! I have changed a couple of wing aileron servos because of a glitch ... but they have proved to be fine after removal.

Each to their own ....

Mine is now is getting ready for replacement not due to servos - but due to my rough use ! Sacrilege I know - but I like look of the Arctic Cat in Hobby King ...

But I know - I will be flying the Polaris always .... it is such a good machine whichever way you set it up.

Nigel
Latest blog entry: The egotistic nature of some !
Jan 12, 2018, 08:08 PM
Registered User
elewon's Avatar
Folks, thanks for the tips on flare. Low rate on elevator for take off/landing is a good idea.

The other thing I want to try is to push CG back a bit. I think my plane is bit nose heavy and that's why it's coming in bit hot and needing more elevator than required for flare.
Jan 13, 2018, 05:02 PM
60 years of RC flying
Daedalus66's Avatar
Quote:
Originally Posted by elewon
Folks, thanks for the tips on flare. Low rate on elevator for take off/landing is a good idea.

The other thing I want to try is to push CG back a bit. I think my plane is bit nose heavy and that's why it's coming in bit hot and needing more elevator than required for flare.


Good idea to experiment (carefully) with shifting the CG back. I generally find that up to 1/4” behind the step works well.
As for the amount of up required at touchdown, it depends of course on the elevator rate and CG, but anywhere between half and full up may be needed for a minimum speed smooth landing. On the other hand, a faster skimming landing looks very nice — if you get it right!
Jan 21, 2018, 12:56 PM
Youtube channel : solentlifeuk
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SoloShot 3 Polaris 21 Jan 2018 (9 min 10 sec)


Back in the air again ....

Love it !

Nigel
Latest blog entry: The egotistic nature of some !
Jan 21, 2018, 04:42 PM
Registered User
pmdevlin's Avatar
Nice Nigel, the red scheme is very effective. So are you filming that with the hatcam you appeared to have? how are you doing the zooming in?

Paul
Jan 21, 2018, 10:11 PM
60 years of RC flying
Daedalus66's Avatar
Very nice color. Good to see such smooth flying.
But 8 minutes on a 1700 battery when running a 6x5 prop was expecting a bit too much.


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