Extra 300 R/C Model Aircraft
By: Ed Smetak
Welcome to my Extra 300 Radio-Controlled (R/C) Aircraft web page!
I have to admit that I am very excited to finally post some construction photos of my latest radio-controlled (R/C) model aircraft project – a Goldberg Extra 300. It’s been a labor of love that has filled many of my spare moments for an entire year, and it’s really starting to take shape now.
Here is how Goldberg Products Ltd. describes this model aircraft:
“When you're ready for something extra... Here's a model that delivers stunning aerobatic performance, handles like a dream, and lands like a trainer. It’s the CG version of Walter Extra's 300 hp Unlimited–class aerobatic masterpiece, and it’s tough to beat for all–around RC enjoyment.”
Well… I hope they’re right!
My Extra is now structurally and mechanically complete. I probably have 200-300 hours invested in the effort so far and am looking forward to the covering and finishing work that will “polish off” this wonderful airplane.
I hope you enjoy looking over my shoulder at the photos on this set of pages. I have been in the R/C hobby for ten years. You can also visit my other R/C pages at http://www.smetak.com/ed/rcaircraft.
If you want to take a look at another beautiful model Extra 300, take a look at Tom Pierce's Mac Daddy.
If you are interested in seeing some photos of the real thing, visit Patty Wagstaff Airshows.
Goldberg Extra 300 Specifications
Wingspan: 68 in
Wing Area: 852 sq-in
Fuselage Length: 61 in
Weight: 10 lb (actual weight of my completed model)
Radio: 6 channel (dual aileron servos and dual elevator servos)
Power: Saito 120 4-Cycle
Links to Construction Detail Photos
My incarnation of the plane is pretty true to the Goldberg blueprints with the following notable exceptions:
· In an attempt to achieve unlimited vertical performance, I chose to go to the high end of the engine range with a Saito 120, 4-Cycle.
· Significant modifications were required in the area of the engine firewall to accommodate the muffler and exhaust tube for the Saito 1.20 inside the engine’s cowl.
· A heavy-duty aluminum J-Tec engine mount was used. The mount was re-drilled to move the engine back toward the firewall as close as possible to help compensate for the effect of the heavier engine on the aircraft’s center of gravity.
· The first fuselage former behind the firewall was moved further aft to enlarge the fuel tank compartment enough to accommodate a 16-ounce fuel tank. This modification also required making a cut-out in the front of the wing to accommodate the new location of the former.
· The cutout in the front of the wing also moved the front wing mounting dowel aft, which increases the shear load carried by the wing dowel (since less load is carried by the bolts at the rear of the wing). As a result of this, and the overall heavier weight of the aircraft due to the engine and engine mount, I decided to go with two dowel pins to secure the front of the wing into the fuselage.
· All of the radio components in the radio compartment were moved aft of the recommended locations to further compensate for the heavier engine. A diagonal member was added at the front of the radio compartment to compensate for the fact that the radio and servo mounting skid was omitted from the front of the compartment, resulting in a loss of structural rigidity in that area of the fuselage.
· Again, to help compensate for the heavier engine, the single servo for the elevator mounted in the radio compartment was replaced by dual elevator servos mounted aft near the front of the horizontal stabilizer.
· A heavy-duty aluminum landing gear was used in place of the supplied steel landing gear rod.
· Fiberglass engine cowl and wheel pants were used in place of the ABS plastic supplied with the kit.