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Old Mar 16, 2012, 07:23 PM
No Hangar Queens!
Maryland
Joined May 2009
1,656 Posts
Build Log
Art Chester's "The Goon" scratch build

So, As I finish another build and learning techniques for a long-term build I am starting another build to hone my finishing skills on composite aircraft. The Subject is Art Chester's "The Goon". A 1930's air race plane I liked due to the nice lines and relatively simple construction to go forth with. Wing span is 31.5" so its in the park flyer range but the power plant will eliminate that all too quickly.
Turnigy SK3 3542 1200Kv 755 watts max
55A ESC to limit the amps on the motor
4S 4000-5000mAh variety. Planning on a NanoTech battery here
8x10 APC Sport propeller
Its all a bit too perfect. The 8" prop will just barely clear the bottom of the fuselage so the belly landings will not rip the motor off or break a prop. The front opening will direct air right over the ESC and vent out the side. Cooling should not be a problem as this should end up being a 100MPH+ cruiser.

I've already started the wing as it was easy. Airfoil templates made from Profili using GOE 459 airfoils. Tips have -1 degree alpha (twist) to help with tip stalls and stability in general. The top of the wing is to be flat inducing slight dihedral in the wing bottom due to airfoil thickness reduction from root to tip. A CF Arrow shaft from Walmart does the job with Gorilla glue holding it there. I covered it with DAP light weight spackle mixed with some polycrylic to make it a bit more hard. The aileron cutouts are lined with balsa and 8mm of balsa at the trailing edge takes care of the ding factor there. Assembly all with white gorilla glue. Each balsa joint is glued with punctures into the foam to allow the glue to expand and grab better. Please comment and lemme know your thoughts. Covering to come on this part as well as tail piece preparation.
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Last edited by Willsonman; Mar 16, 2012 at 07:30 PM.
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Old Mar 16, 2012, 09:47 PM
treefinder
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SE MI
Joined Oct 2004
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Been looking at this guy for a while, but other committments.... I'll be watching this great plane come together.
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Old Mar 16, 2012, 11:54 PM
Foam Av8r
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Joined Sep 2008
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I am watching
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Old Mar 17, 2012, 08:01 AM
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As you know I made the Real Flight model of this bird so I'm very interested in this build. Its off to a good start.
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Old Mar 17, 2012, 08:49 AM
Up-Out-&-Gone
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Charelston SC U.S.A.
Joined Mar 2007
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Great project Wilson! very cool!
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Old Mar 17, 2012, 11:23 AM
No Hangar Queens!
Maryland
Joined May 2009
1,656 Posts
Yes Boof, It is what inspired me to make this model. Great lines and a practical setup. Glad to see others watching.
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Old Mar 17, 2012, 05:27 PM
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What method did you use to cut the foam?
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Old Mar 17, 2012, 07:44 PM
No Hangar Queens!
Maryland
Joined May 2009
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Hot Wire Boof. Only way to make a foam core wing. Profili makes some great templates and you just super 77 spray them and stick them to reddi board from $tree. Cut out with a razor and line the edges with some of the metal ducting tape. Way simpler than making wood ones.

Progress tonight. Sanded down the spackle across the spar and trimmed down the wood trim in the aileron slots. Started making the ailerons as you can see from the pictures. I had some leftover linen color solartex from a previous build so I used that here for a better scale appearance and it fairly well matches the color I'll use. I'll take a sample in to the Home Depot and have it color matched for some paint. Easy peasy. $3 for a tub of custom paint is not bad.
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Old Mar 17, 2012, 07:45 PM
Fremont, CA
United States, CA, Fremont
Joined Jan 2009
1,591 Posts
Nice looking plane!
Suggest to increase tail feathers by about 25-30%.
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Old Mar 17, 2012, 07:54 PM
No Hangar Queens!
Maryland
Joined May 2009
1,656 Posts
in area or what?
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Old Mar 17, 2012, 09:06 PM
A Day @ a Time - Matt. 6:25-34
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North AL, USA
Joined Nov 2009
1,864 Posts
This is cool... IMHO it would be kinda funky if it was just a slow-flyer.
The thrust line in comparison with the wing and stab is interesting, they are nearly aligned; how much down and/or right thrust do you think you'll need?
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Old Mar 17, 2012, 09:36 PM
SlingWinger
San Bernardino, California, United States
Joined Oct 2004
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Quote:
Originally Posted by djacob7 View Post
Nice looking plane!
Suggest to increase tail feathers by about 25-30%.
Many scale models can have stability and handling issues when the tail is to scale. Models of slow, easy to fly planes such as Cubs or Champs generally do fine.

But airplanes that were designed for high speeds, such as Mustangs, Spitfires, and racers often had tails that were only just big enough to get by.

You can probably get by with the scale tail feathers if you are are a good pilot, but the CG range will be very short, in comparison to the model that was designed to be a model, or a model of a trainer or other type of airplane designed to be easier to fly than a hot rod type.

I once made a foamy Spitfire slope glider. I made the simple flat foam tail surfaces about 160% of the scale size, then while out flying her I kept cutting them down until she got kinda spooky, then I added a little back on until I liked her again. Back at the shop I made nice looking new ones, as I recall they were about 20% larger than scale, in both span and chord.
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Old Mar 17, 2012, 10:03 PM
No Hangar Queens!
Maryland
Joined May 2009
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Interesting dayhead. I've not had the experience to try that sort of experiment. All my numbers seem to suggest it will fly just fine given the areas and weight projection. Perhaps a bit of caution should be taken here just for the sake of this thing not going into someone's car at the field. 20% would be quite doable without changing the overall look too wildly. I was definitely planning on a rudder. I've read around that this sort of bird needs it on the slow end to direct things where they need to be.

ruff I'm initially planning on none. The beautiful thing about foam is I can cut the firewall off and glue on right back on if I need to change something. With a small prop in relation to wing area I am not sure much back torque from the motor will be present. Thus not much to offset. I'll see how she flies before I call it perfect. My last scratch build went right in on the first flight... turned out to be over compensation of control surfaces causing a stall on take-off. I know my design methods work but we shall see on this subject.
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Old Mar 18, 2012, 03:43 AM
Build straight - Fly twisty
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Australia, QLD, Little Mountain
Joined Feb 2010
4,142 Posts
My prediction is that the scale tail-feathers will be fine for The Goon. (Not so for The Jeep)
Thrust-line 0,0 and just a touch of right rudder will be the go.
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Old Mar 18, 2012, 08:04 PM
No Hangar Queens!
Maryland
Joined May 2009
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Finished the second aileron and made the torque rods that go through the wing. Lighter and metal rod method. No pictures as you can imagine its rather dull and to be completely honest you do not need to see my mistakes where I went through the wing... over and over again. Thats the beautiful thing about foam... so forgiving. More light weight spackle drying.

In an additional consideration for the tail feathers I had forgotten about my cosnideration of the top and side profiles of the fuselage. I'm posting the 3-view I am working from to illustrate this better. From the top view you can see how the top profile creates a very good shape for laminar flow. There should be no issues with interference on the H-stab due to maintaining good flow close to the fuselage. From the top and side view you can see where almost the entire area beneath the V-stab along the edge of the rudder... that whole area is basically like the Gee Bee sportsters where the yaw stability is more or less a result of the fuselage. Imagine a Gee Bee in a hall of mirrors all stretched out... just put an inline motor in it rather than a radial. Not exactly but I am sure you can see my point. So with this in mind and the ratio of areas of the surfaces in relation to the main wing area and projected weight... I am keeping the scale size tail.
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