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Old Aug 21, 2012, 03:06 AM
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serjuro's Avatar
Romania, Europe
Joined Aug 2009
282 Posts
Hello, Skyman, are you talking about mixing the motors ?
In my plane, I did not use mixing for motors, just put them into separate channel and link them togheter. I think that mixing motor channels can lead to acrobatic behaviour and potential dive spins, wich is not this plane intended use...
As for propeller, I have used two RH ones, not counter-rotating ones and it flew very nice, no drift observed...
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Old Aug 22, 2012, 04:41 AM
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The SKY MAN's Avatar
uk/england
Joined Jun 2008
341 Posts
Just thought i could use my tx to provide the mixing of throttle and link it to a switch so when airbourne i can switch it off ! but then flying might be fun useing dif throttle in flight we will see.

Need dif throttle for taxiing on water seems the best way to go!

Got my 6mm and 3mm depron last night so have started to assemble the craft, i only hope that it looks half as good as ak68s
Iain
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Old Aug 22, 2012, 10:02 AM
low tech high tech
vtdiy's Avatar
Southern Vermont
Joined Feb 2007
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Sky Man, throttle mixing was a big topic on the original Puddle Twin thread, and successfully used by Meatbomber the OP, and many others. You might want to check that thread out. He also used a switch to add it.

I used a water rudder, and there is a video which shows my plane struggling to head upwind on the water at low speeds. This is much more do-able with throttle mixing.
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Old Aug 24, 2012, 03:28 PM
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Nederland, ZH
Joined Dec 2011
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Hi all,

Some testflights have just been done tonight. Sharing some sticktime here in HD so go full screen:

Taxiing testing rudder input and diff throttle:

puddle twin taxiing 1 lap (0 min 27 sec)


Some more laps:
puddle twin taxi rounds (0 min 48 sec)


And flight nr 3. Trying to improve touchdowns:

puddle twin flight 3 (4 min 37 sec)


And finally flight nr 4. Thats the weekly upload limit for now. Enjoy:

puddle twin flight 4 (2 min 6 sec)


AK68
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Last edited by ak68; Aug 24, 2012 at 04:13 PM.
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Old Aug 25, 2012, 02:19 AM
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The Netherlands
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This is really cool, AK68! I like the gracefulness in the air, and also the smooth handling during taxi.

For landing, I think a bit expo will help against the bounces (as you already suggested). It's easier to control the flare before touch down. As you see during take off it lifts up very easily (actually sometimes I think that in some taxi-phases you are already flying ), so that means that during landing it will bounce easily back in flying mode . So drain the energy very low above the water until you feel you need too much up elevator and then let it drop softly. I think your first landing in the last video was close to that.

But you really really make me feel ill, my PT2XL building project is still stuck at it's retracteable front wheel...

But anyhow I enjoy your videos!
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Old Aug 25, 2012, 07:43 AM
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serjuro's Avatar
Romania, Europe
Joined Aug 2009
282 Posts
Very nice AK68, nice bird.
As for diff throttle, how did you mixed the channels ?
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Old Aug 25, 2012, 10:35 AM
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Wormboy's Avatar
Australia, WA, Madeley
Joined Jul 2011
677 Posts
wow I'm really pleased to see so much action on this thread!

AK your PTIIXL is looking great, I think the suggestions above, to increase your expo will certainly sort out your landings and just lower your speed.
Whenever I skip on water landings it because I've come in too hot

The diffferential thrust looks like its working very well.

I'll be attaching the wing floats and taking off the wheels from my build tomrrow. I have to make the most of the lake before it dries up for summer. I havn't forgotten about the request for a photo of the landing gear, I'll take one before I pull it off.
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Old Aug 25, 2012, 04:55 PM
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ak68's Avatar
Nederland, ZH
Joined Dec 2011
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Quote:
Originally Posted by serjuro View Post
Very nice AK68, nice bird.
As for diff throttle, how did you mixed the channels ?
All thanks for commenting and watching.
Serjuro: The mix is not in the Tx or Rx.
It is done with 200 step external V-tailmixer. Rudder and trottle From Rx to V-tail mixer inputs. Two esc's connected to the two outputs.
Actual rudder servo added to Rx rudderoutput with Y-harness.

Wormboy: thanks in advance for posting a pic of temporary undercarriage. Looking forward to (maiden) video and testimony. Land and water.

Mavlo: Get well soon.
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Old Sep 10, 2012, 11:42 PM
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Nederland, ZH
Joined Dec 2011
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Hi all,

Here some more inspirational short video for scratchbuiders concerning depron Puddle Twin with differential throttle. Handling in water and air is great fun now Cog is adjusted.
Enjoy.

Taxiing:
puddle twin XL (1 min 31 sec)


Flying:

puddle twin XL. Flying (1 min 27 sec)






AK68
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Last edited by ak68; Sep 11, 2012 at 04:42 PM. Reason: adding pictures
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Old Sep 13, 2012, 02:45 PM
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mavlo77's Avatar
The Netherlands
Joined Oct 2008
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Very nice flying style AK68! I like this! In your turns in the air you used the rudder with the differential thrust, correct? I saw some slipping.

Nice camera work too.
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Old Sep 23, 2012, 04:49 PM
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ak68's Avatar
Nederland, ZH
Joined Dec 2011
658 Posts
Here is some material done by Mavlo77. If you like this: His other videos are certainly worth checking. Thanks Mavlo77 for being audience, camera crew, editor, driver & coach.
R. Merk Thanks for the plans.

My first steps into loop, roll, inverted, knifeedge, sideslip, low pass & waterslides with Puddle Twin XL: Enjoy:

Puddle Twin II flight, pilot AK68 (5 min 31 sec)
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Old Oct 21, 2012, 02:13 PM
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uk/england
Joined Jun 2008
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THOUGHT I'D POST THIS
so as to gain some interest

Iain
PS i should be flying mine soon!!!!!!!!!!!!!!!1
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Old Oct 25, 2012, 03:52 PM
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ak68's Avatar
Nederland, ZH
Joined Dec 2011
658 Posts
Quote:
Originally Posted by The SKY MAN View Post
THOUGHT I'D POST THIS
so as to gain some interest

Iain
PS i should be flying mine soon!!!!!!!!!!!!!!!1

Yes you do gain interest: I saw your FFF eagle. Interesting bird. Any preflight pic's and details of your puddle twin? Whereabouts in the UK do you fly? Is it OK in the UK to just find a quiet roadside spot and fly or is it frowned upon?
Looking forward to video evidence of your PTII. Have a good flight (maiden?)


AK68
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Old Oct 27, 2012, 03:27 AM
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The Netherlands
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New building progress...

Thanks to AK68 I picked up the building of the PT2XL!

I got stuck engineering the front wheel doors mechanism (I am making a full amphibous with retractable gear). I am close to a solution for this system, however AK68 advised me to continue with the wing to make some progress. And he is right: at some point it needs the wing to fly.....

So here we go. See images below. So far the wing is extremely symmetric and straight. Hopefully it stays this way after glueing the top skin...

Wingspan is now exactly 146.5 cm.

Engineering decisions:
- Balsa wood LE at the middle section for stiffness. This strengthens the motor mounts/nacelles and also the wing mount to the fuse.
- Dihedral minimum. Top of the wing close to flat, bottom has the tapering up because of smaller ribs to the tip. This way there is some effective dihedral since the camber lines define the dihedral.
- Slotted flaps (2 pieces 7 x 27 cm), not cut out yet. Big flaps for steep approaches in tight spaces. I made the span of the middle section a bit wider to have more straight flap span. In the images you see the 45 degree bulkheads which close the flaps slots. But they continue till the 2nd rib in the side wing panels (have to make it yet). I thought of slight aileron droop (flapperons) too but this is occupying too many radio channels and a v-tail mixer not flexible (no possibility to change mix ratio).
- Motor will be 2x 1100 kV driving 2x counter rotating 9x6 props at 3 cell lipo.
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Old Nov 11, 2012, 11:33 AM
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Some more progress... Flaps are cut out, and I installed the linkeage system for controlling the flaps. As you can see it's an internal system.
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