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Old Jan 30, 2008, 09:56 PM
niner555 is offline
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Build Log

GWS A-4 kit bash..... IAF A-4H single seat conversion!


This is my first build log, so go easy on me

When I saw GWS's A-4 prototype a long time ago, I knew I had to have it when they finally started shipping. Of course I am never happy with anything in it's stock form, so my ultimate GWS A-4 foamy EDF would be no exception. Here is the basic outline of what I will be trying to accomplish and the hardware I will use to make it fly much faster than GWS ever intended this chunk of foam to go !

The airframe:

* I have always admired the Israeli Air Force and for years they flew the A-4H extensively. I did some research and found some really great pics...so I chose to modify the GWS A-4 into a single seat A-4H model with a paint scheme from 1967, around the time of the Six-Day War.

* I will be setting this jet up to be as light as practical....as I will be hand-launching it.

* Since the inlet ducting is WAY oversized for the Minifan I will be using, the inlets will be cut-down to not only reduce drag, but make the jet more scale in appearence....more on that later. I will be also be making full fiberglass inlet ducting for maximum EDF efficiency.

* For strength and ding resistance I will be glassing the whole airframe with a single layer of .56 oz. glass.

* Paint will be custom mixed acrylic....cheap and simple to apply with a brush.

The powerplant:

* My tried and true Wemotec minifan with an ARC 28-47-2 motor running on a 7S, 2100mah lipo set-up. This gives me right at 880 watts, 50 oz. static thrust, and 8 minutes of mixed flying. My outlet is set-up for 80% of FSA. This is a great power package....I recommend it to anyone!

* Suppo 70 amp ESC.....it's way cheap, but has performed flawlessly to date.

Matt

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Last edited by niner555; Jan 31, 2008 at 12:49 AM.
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Old Jan 30, 2008, 10:20 PM
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OK, first things first....

Before I build anything, I like to know where I am starting from. I measured all the important dimensions and came to the following conclusions:

* To get the single seat conversion looking right, I will have to extend the inlets forward about 1 1/2 in. and the canopy will obviously have to be trimmed and sculpted back into the airframe.

* I made a template to measure the inlet cross sectional area. After tracing it on some graphing paper, it's easy enough to count squares and get a good estimate of the area.

The area came to 3.13 in.sq. per side for a total of 6.26 in. of area. Since a minifan is right at 4.52 in. sq., that makes the stock inlets 138% of FSA !!!!! WAY too big and draggy....it will be fixed!

* The wing measures out to be only 8% thick....not too bad...should be fairly efficient for high-speed flight.


Matt

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Last edited by niner555; Jan 31, 2008 at 06:16 PM.
Old Jan 30, 2008, 10:29 PM
corsair nut is offline
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fly like an EAGLE ;)
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dang, i knew the fsa was bigger, but not that big!! guess ill be sizing them down to scale
Old Jan 31, 2008, 12:37 AM
AIR SALLY is online now
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deltas are cool
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C/N you forgot to sell him one of your A-4 single seat canopies
Old Jan 31, 2008, 12:48 AM
gunracer is offline
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diligentia vis celeritas
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signing on...7 cells?...i like it!...
Old Feb 01, 2008, 01:03 AM
gunracer is offline
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diligentia vis celeritas
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very nice...i'll have to give your single seater mod a try...
Old Feb 01, 2008, 01:14 AM
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Nice. And you've already got a single seat canopy pulled or did you buy one from Corsair Nut?
Old Feb 01, 2008, 02:12 AM
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diligentia vis celeritas
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it looks like the stocker cut back...
Old Feb 01, 2008, 07:08 AM
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Quote:
Originally Posted by jridge
Nice. And you've already got a single seat canopy pulled or did you buy one from Corsair Nut?
Thanks, it is just the stock canopy trimmed down. I had to angle/trim the rear of the canopy down about 1/8 in. to get the rear hump to blend in right. I just eyeballed it till the transition looked smooth.

Matt
Old Feb 02, 2008, 03:52 PM
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After looking at some additional photos of the A-4H, I think I may have over estimated the amount the intakes needed to be moved forward. It appears that the lack of an intake splitter plate is what makes it appear that the stock GWS intakes are too far back.

Well, since I needed to reduce the inlet size of the intakes to better match my Minifan's FSA anyway, I decided to install scale sized splitter plates and at the same time size them to get a final air inlet area of 100% FSA.

They are not difficult to make, but are very tedious and time consuming. I think they are worth the effort, IMHO they really add a nice scale look and are very functional as well.

Matt

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Last edited by niner555; Feb 02, 2008 at 05:59 PM.
Old Feb 02, 2008, 04:23 PM
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A-4 nut!!
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Nice!

So are you going to move the cockpit back now?
Old Feb 02, 2008, 05:30 PM
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Quote:
Originally Posted by skyhawk
Nice!

So are you going to move the cockpit back now?

I think I will leave it as-is. Here is a photo of a square-tail A-4H that has a canopy that appears to be moved farther forward than the color illustration I have at the beginning of this thread.

Since the photographed A-4 looks more like the way my GWS A-4 is without anymore modifications, I think I will follow the photo Makes my life easier this way than having to move the canopy back .....

It isn't 100% scale, but it's close enough to make me happy.

Matt

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Old Feb 02, 2008, 06:52 PM
Cap232ac is online now
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there is no spoon...
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'picked up some Depron today for the duct work. I like your intakes. It's enough to inspire me to do the same.

Aaron
Old Feb 02, 2008, 11:50 PM
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Cool...It's nice that GWS has done most of the hard work for us with this airframe. We can spend our time on the detail/scale stuff and make something unique.

Good luck on your project.

Matt


Quote:
Originally Posted by Cap232ac
'picked up some Depron today for the duct work. I like your intakes. It's enough to inspire me to do the same.

Aaron


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