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Old Aug 16, 2012, 11:03 AM
Chop it, cut it, bash it
quitcherbitchen's Avatar
United States, CA, La CaŮada Flintridge
Joined Jul 2011
5,763 Posts
Like it, Like it, Like it. Thanks for the build log. I personally have a thing for flaps. Experiment with them all the time. I like your solution. Very realistic looking I'm sure. Can you get some air shots?
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Old Aug 16, 2012, 11:17 AM
The sky is the limit
BAF23's Avatar
Belgium, Vlaams Gewest, Hasselt
Joined Aug 2012
199 Posts
DC3 with sound

Monday morning I was happy the postman brought the sound module I had ordered on sale in the USA from MrRCSound.com half a week earlier as expected, quick delivery by US post and no custom fees in Belgium. I had bought the model to install in the FMS 140mm T28 but I was still collecting all necessary parts and decoration to start assembling it to represent a local stationed aircraft.

I couldnít wait to hear the module so I quickly decided to fit it on my already completed and flight tested Dynam DC3 (marketed as Skybus). Because I had already added a steerable tailwheel and 4 sections of individual flaps powered by a single servo, it became slightly tail heavy and I had installed 50gr lead in the nose and used my heaviest batteries to balance it to the correct cg. That limited the location of the sound system to between the forward wing attachment and the nose battery. I carved a 4cm diameter vertical tunnel out from the bottom to the middle of the fuselage (foam being 45mm thick there to support the wing glove), removed foam on the side and forward just sufficient to allow the sound unit to be slid under the roof, then lowered in a 6,5cm square trench halfway down the shaft. With all the removed material I glued carbon stringers along both sides of the fuselage for strength, and glued a mesh cut and formed from 3M plaster abrasive material on the bottom of the fuselage.

The long volume potentiometer of the sound system limits its orientation, and the sound card on the side was loosened from its Velcro fitting and slid deeper into the fuselage. I soldered 2 deans plugs with the sound unit power cables in between, making it easier to switch the system from one airplane to another. For the same reason I opted for Small Velcro triangles on the 4 corners of the speaker to latch it to the bottom of is housing. A lengthened servo cable was then added to make connection easier to the wing mounted receiver, through an additional y-cable (there already was a y cable towards both ecsís in the wing nacelle. It is a tight fit but doesnít require special dexterity or tools to install or remove the sound system (but youíll have to add weight in the nose flying without the sound module installed).

The sound system module weighs 190gr so makes up 15% of the weight of the aircraft. Having removed the nose weight and using the very light Grayson hobby 3S2200 battery (only 150gr) the DC3 balances nicely again but itís grossweight jumped from a box specification of 1200gr to 1470gr (tailwheel, flaps, scale tires, sound system, reinforcements, custom paint job plus varnish). With a wing area of 24,6dm2 this means it now has a wing loading of 60gr/dm2 and behaves much steadier in the air. The landing gear legs look scale but are only plastic and non shock absorbing so it has to brought in very gentle for landing.

After the engine change both engines donít start exactly synchronous anymore, but this now helps realism in the starting sequence. By very slowly opening up the throttle the sputtering ignition of the Pratt&Whitney sound comes in just a tad before the port nr1 prop starts rotating. With a delicate throttle advance the engine sound reaches idle rpm as the left prop rotates. Opening the throttle just a tad further pus the starboard nr2 prop in motion and taxying sounds fantastic, distracting flying pilots when you pass them on the way to the active. You see them look down from their aircraft to that DC3 because the sound is so unusually realistic for such e small 150mm foam model. Opening up the throttle doesnít cause the expected increase in decibels but you canít expect wonders from a 2inch speaker belching through a tunnel pointing vertically down.
In the air you still can hear it and it is lovely making passes in a bank pointing the speaker at the audience, the Doppler shift providing an acceptable sound. This became especially obvious when after a touch and go the sound stopped for a yet unexplained reason. When after the final landing I opened up the throttle to taxi in, the startup sequence initiated and the sound worked as advertised again. I still have to learn to throttle down in a way the props stop at the correct shutdown sound but even now it already is a bit of a crowd pleaser although itís not easy with our members being very used to the sound of large 4-stroke engines and even a Moki powering a 3meter wide super scale Beechcraft Staggerwing.

After opening up the yet unventilated cockpit cover I was surprised how cool the sound unit felt, I even could keep my finger on the amplifiersí heat dissipater and I had run the potentiometer almost full up during that flight. Battery consumption also was lower as anticipated and after that 7 minute flight (but 12min ground ops) I still had 40% left over from the 3S2200mahn powering the engines, servo and sound system.

For a first look Iím satisfied with the product, but not overly enthusiast, but probably that comes because of the speaker being too deep in a foam tunnel (I needed to keep some structural strength for the wing fuselage interface). In the T28 Iíll make sure to find a spot almost flush with the underside so the sound can spread more sideways. Further ground testing also revealed very little difference in the selectable sounds. For the sale price (shipping included to Belgium) it certainly was worth the 101 Euro I spent, it enhanced the attractiveness of the DC3 to a great extent, without penalizing its flight characteristics, to the contrary providing a more stable platform less susceptible to wind gusts. I was surprised the budget sound system type could be made to fit in such a small diameter fuselage.
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Old Aug 16, 2012, 11:26 AM
The sky is the limit
BAF23's Avatar
Belgium, Vlaams Gewest, Hasselt
Joined Aug 2012
199 Posts
Quote:
Originally Posted by quitcherbitchen View Post
Like it, Like it, Like it. Thanks for the build log. I personally have a thing for flaps. Experiment with them all the time. I like your solution. Very realistic looking I'm sure. Can you get some air shots?
The only airshot I have is from the real flying N49AG this summer at Koksijde airshow (Belgium) and illustrates how the flaps deploy in sections, but a good photographer could take exactly the same shot of my Dynam model and you would hardly see the difference.
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Old Aug 16, 2012, 12:09 PM
Chop it, cut it, bash it
quitcherbitchen's Avatar
United States, CA, La CaŮada Flintridge
Joined Jul 2011
5,763 Posts
Now that's what I'm talking about! Nice
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Old Aug 16, 2012, 12:24 PM
What tree??.......Doh!!
Smokin_Joes's Avatar
USA, WA, Seattle
Joined Aug 2007
766 Posts
BAF23,

Simply AWESOME!

Any video with sound unit?
Does start-up only work with first motor and no additional start-up sequence when second motor starts to rotate?

Cheers~

Neil
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Old Aug 16, 2012, 02:22 PM
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WVrailfan's Avatar
United States, WV, St Albans
Joined Jul 2011
1,777 Posts
I've pretty much finished painting my Army C-47. I'm installing a set of Ram lights (set 187) which includes landing lights, wingtip nav lights, a white strobe and a white tail light. I will have to extend some of the wires a few inches.

I ordered decals from Callie Graphics which should be here soon and I can finishe the cosmetic work.

I painted the landing gear silver and replaced the tires with Dave Brown 2 3/4 treaded tires which look much better.

Jim
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Last edited by WVrailfan; Aug 16, 2012 at 02:31 PM.
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Old Aug 16, 2012, 02:24 PM
The sky is the limit
BAF23's Avatar
Belgium, Vlaams Gewest, Hasselt
Joined Aug 2012
199 Posts
Quote:
Originally Posted by Smokin_Joes View Post
BAF23,

Simply AWESOME!

Any video with sound unit?
Does start-up only work with first motor and no additional start-up sequence when second motor starts to rotate?

Cheers~

Neil
Sorry, no videos yet, got to find some younger guys who are good at that, I'm only into flying. I promise to post some if ever available.

The sound unit is hooked up through a y-cable between the factory y-cable going between the receiver to the esc's. In my case by veeerrry slowly advancing the throttle the startup sounds kicks in just before the port engine starts rotating. When it stabilizes I advance a tad more and the starboard props start rotating without any change in noise (unless you install 2 separate systems this will always be the case). I had to experiment a bit with the throttle trim position to get to that point.

The slight difference in left and right engine doesn't affect flying at all because with the sound system I advance the throttle trim to a point the engines don't cut when throttling all the way back (avoiding the shutdown sound when the aircraft still is in the air or landing).

Back at the parking and running on idle I then trim the throttle down slowly for a full cut, aiming for a synchron shutdown noise as both props stop rotating. I then advance the throttle trim to my known startup position to be ready for the next flight. I'm using an old Spectrum DX7 with an AR500 receiver and have mixed my 3-position flap switch through the gear channel on the receiver.

No guarantee this system works with other brand transmitter or receivers, or even with individual ESC's delivered to other customers. Finding out such things is half the fun, but do it at the flying field if you want to keep the neighbors friendly
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Old Aug 16, 2012, 03:39 PM
Chop it, cut it, bash it
quitcherbitchen's Avatar
United States, CA, La CaŮada Flintridge
Joined Jul 2011
5,763 Posts
You might want to upgrade the AR500 receiver if you want to keep that plane intact. They have a very bad reputation and Spektrum doesn't even sell those anymore.
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Old Aug 16, 2012, 09:50 PM
Plane Fanatic
DeathWarmedUp's Avatar
Australia, QLD, Gympie
Joined Jul 2007
890 Posts
Quote:
Originally Posted by BAF23 View Post
....but do it at the flying field if you want to keep the neighbors friendly
AND the Wife - lol

Very nice job on your DC-3 and the sound system. I have looked at the MrRCSound.com units and am very tempted.
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Old Aug 17, 2012, 12:28 AM
Always puts it on the numbers.
Spookeay's Avatar
United States, AL, Sylacauga
Joined Jul 2012
1,150 Posts
Quote:
Originally Posted by WVrailfan View Post

I ordered decals from Callie Graphics which should be here soon and I can finishe the cosmetic work.
You know, they make decal paper for ink jet printers. You print out what you want and then spray the paper with clear coat. After that, soak in water and stick them on.

Water slide paper Link
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Old Aug 17, 2012, 01:51 AM
Registered User
WVrailfan's Avatar
United States, WV, St Albans
Joined Jul 2011
1,777 Posts
Quote:
Originally Posted by Spookeay View Post
You know, they make decal paper for ink jet printers. You print out what you want and then spray the paper with clear coat. After that, soak in water and stick them on.

Water slide paper Link
I've used the ink jet water slide decal sheets and never really been happy with them. Callie makes just what I want, in the correct size and colors. Her quality is great and her prices are very fair.

Years ago I had an Alps printer which does not use ink it uses a wax/rosin ribbon which it heats to fuse it to what ever you were printing on, including water slide decal paper or even vinyl film. You could even print white, silver and gold with it, and the finished product was water proof. But it died and they no longer sell them in the U. S. If they ever do, I'm buying two of them.

Jim
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Old Aug 17, 2012, 04:10 AM
The sky is the limit
BAF23's Avatar
Belgium, Vlaams Gewest, Hasselt
Joined Aug 2012
199 Posts
Quote:
Originally Posted by quitcherbitchen View Post
You might want to upgrade the AR500 receiver if you want to keep that plane intact. They have a very bad reputation and Spektrum doesn't even sell those anymore.
I have 3 of those receivers I intensely use even on my B25 bomber I fly at serious distances, never had problems with them. I still fly exclusively DSM2 with more than 10 various types of original Spectrum receivers in all kind of planes and never encountered a radio related problem.
Oh, and concerning keeping the wife happy....I'm a single woman who finds happiness through model airplanes
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Old Aug 17, 2012, 06:09 AM
Plane Fanatic
DeathWarmedUp's Avatar
Australia, QLD, Gympie
Joined Jul 2007
890 Posts
Quote:
Originally Posted by BAF23 View Post
keeping the wife happy....I'm a single woman who finds happiness through model airplanes
COOL!! We need more females in this hobby/sport. Well done!

Now, I just have to convince my Wife that my hobby can produce happiness for her too (fat chance)
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Old Aug 17, 2012, 10:46 AM
Registered User
United States, WI, Fond du Lac
Joined Sep 2008
1,740 Posts
Quote:
Originally Posted by quitcherbitchen View Post
You might want to upgrade the AR500 receiver if you want to keep that plane intact. They have a very bad reputation and Spektrum doesn't even sell those anymore.
I too have several AR500 and they are excellent. I've been flying them for years and never had a problem.
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Old Aug 17, 2012, 12:31 PM
Registered User
Canada
Joined Jul 2009
6,976 Posts
I have a couple AR500s and so far so good. I think it was one particular batch that had problems. That happens with many products and we shouldn't condemn a whole product line just because of that. Remember the Spektrum DX6i? There were 2 serial number runs that had a recall. On the most part those are good TXs.
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