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Sep 16, 2017, 12:15 PM
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Build Log

A-4 Skyhawk 80mm EDF Jet by Freewing


Got this one as an "Arf Plus" kit from MRC for $249 - including shipping to Cali :

http://sz-freewing.com/

https://www.motionrc.com/products/fr...mm-edf-jet-arp

https://www.motionrc.eu/collections/jets-and-ducted-fan

https://www.rc-castle.com/index.php?...th=470_507_508

This thread in German : https://translate.google.com/transla...ing%26pp%3D100

Will install my own 80mm inrunner motor fan with a yep (yge) 150A esc,

https://www.rcgroups.com/forums/show...EDF-fan&pp=100

Was not going to use the outrunner fw fan that comes with the pnp kit, although the performance should be rather similar, at least to the comparable FW inrunner version.

The original Douglas A-4 Skyhawk had a wingspan of 8.38m and an overall length of 12.22m :

https://en.wikipedia.org/wiki/Douglas_A-4_Skyhawk

whereas the model has a wingspan of 940mm and a length of 1430mm, which gives as an overall scale for the model of ~ 1: 8.91 (from the wingspan numbers).

The paint scheme on mine represents an A-4P of the Argentinian air force around ~ 1982 so it's usualy referred to as the "Falklands" ("Malvinas") scheme.

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Videos added :

A-4 Skyhawk by Freewing - FMS 80mm fan 4K (3 min 2 sec)



A-4 Skyhawk 80mm EDF by Freewing with FMS inrunner fan (3 min 38 sec)




A-4 Skyhawk 80mm edf Takes Off in a Stiff Crosswind (3 min 37 sec)




A-4 Skyhawk FW 80mm landing (0 min 37 sec)




A-4 Skyhawk FMS 80mm Fan - Small Dot in the Blue Sky (0 min 37 sec)
Last edited by Herb; Feb 26, 2019 at 06:10 PM.
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Sep 16, 2017, 12:27 PM
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Did not want to have one more Skyhawk that looked like everybody else's Skyhawk in some colorful us navy scheme...

On the internet one can find some rather good plastic model renditions of the "Falklands" A-4 Skyhawk, mostly by Hasegawa, Eduard and Fujimi.

These help quite a bit with the decals (I make my own), and with matching the paints with my Tamiya airbrush XF collection.

Among the ones below, some look rather pristine while others exhibit a very well done subtle weathering.

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Last edited by Herb; Sep 16, 2017 at 12:34 PM.
Sep 16, 2017, 12:38 PM
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The base paints are actually very simple, Tamiya XF-80 navy gray for the top and XF-2 flat white for the bottom. The other paints (argentinian light blue) are simple custom mixes.

I don't use household paints (behr, ace etc) since they are way too heavy for edf models, the Tamiya paints are very thin and light with alot of pigment. And easy to airbrush.

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Sep 16, 2017, 12:45 PM
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The FW A-4 Skyhawk is quite comparable in size to my old composite 90mm edf JePe A-4 which flew like a bat out of hell (sold a few years ago to Andrew ) .

https://www.rcgroups.com/forums/show...21&perpage=100

The wingspan on the 80mm edf FW one is 37" whereas on the 90mm edf JePe one it's around 36".

https://wn.com/a-4_skyhawk_jepe_90mm_edf

https://wn.com/a-4_skyhawk_jepe_90mm_edf

so the Freewing one is ~ 3% bigger (in wingspan).

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Last edited by Herb; Apr 24, 2018 at 08:00 PM.
Sep 16, 2017, 12:56 PM
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For the first few flights I will try out this (modified) fms 80mm fan with 32mm inrunner motor that I already had lying around.

https://www.banggood.com/FMS-80mm-12...p-1125125.html

It seems like a decent fan with what looks like a decent quality inrunner ... The rotor was out of balance and had to be statically balanced like many of my other edf rotors.

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Last edited by Herb; Sep 18, 2017 at 11:35 PM.
Sep 16, 2017, 12:59 PM
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Next step is measuring the intake and exhaust area, and closing up that bottom cheesegrater intake ...

Did not like that phillips screw that holds the alu spinner in place, a socket head is a lot easier to tighten, and it's the only thing that keeps the rotor on Added loctite as well.

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Last edited by Herb; Sep 20, 2017 at 12:35 PM.
Sep 18, 2017, 01:24 PM
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What did the pilot and cockpit look like ?

There are many pics on the web, here's some (possibly relevant) info also from the Skymaster A-4 page:

http://www.skymasterjets.net/a4.htm

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Last edited by Herb; Sep 24, 2017 at 02:10 PM.
Sep 19, 2017, 01:53 PM
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All setup & connected and ready to go into the Scooter

Bench tested the fan at low power and it seems to run pretty smooth. Final test will be with on 6S with a wattmeter & fan installed in the plane....

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MOV09687 (0 min 6 sec)
Last edited by Herb; Sep 20, 2017 at 12:48 PM.
Sep 19, 2017, 04:03 PM
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Nice work Herb! Love the scheme options you are looking at.
Sep 19, 2017, 06:01 PM
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Thanks Eddie ... Something different
Sep 19, 2017, 06:05 PM
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FMS 80mm fan with 32mm inrunner motor installed (I should say: test fitted), it seems a good match dimension-wise.

Luckily that plastic cheesegrater popped right off, almost no glue is sometimes a good thing !!

Stock outlet right now is 66mm.

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Sep 19, 2017, 06:07 PM
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The two intakes join into one with some curvature ...

Both intakes are pretty much a nice straight shot to the fan

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Sep 20, 2017, 01:36 AM
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I measured the combined area for the two intakes at ca. 4300 mm^2 - or around 102% FSA (4220 mm^2 ) for the fan I am using.

That would indicate that the cheater hole is not really needed, the fan should get plenty of air just from the two intakes.

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Last edited by Herb; Sep 20, 2017 at 01:44 AM.
Sep 20, 2017, 01:41 AM
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I decided to close off the cheesegrater intake ... If done with a flat plate that would still leave / create a lot of turbulence just before the fan, not good.

I chose therefore to make a foam plug to close up that huge hole, and improve a bit on the airflow just before the fan.

To make the cheater hole plug, I needed the right dimensions, so I cut out some paper templates and then from those cut the foam plug.

It's not perfect, but it should do the job ...

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Last edited by Herb; Sep 22, 2017 at 06:04 PM.
Sep 20, 2017, 05:10 AM
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Excellent work Herb!


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