CG Extra 300
 

Howdy folks, here's some pix of a build I recently completed kit I had lying around for a few years.
I heavily modified the original (can never leave anything alone...) to accommodate a OS 110 Alpha.

The firewall was moved 3/8" forward to make space for a 14oz tank, a platform was fabricated to mount the tank and the whole thing is accessed thru a hatch built into the bottom of the front end. Several lightning holes were drilled to save weight and the plane balanced nicely with 2 low profile servos in the tail for elevator.

The fillet around was the vertical fin is solid balsa because I could never get the 1/32" planking to fit right. Aileron servos were mounted per current practice instead of under hatches. The vacuum molded cockpit floor was ditched in favor of 1/16" balsa sheeting. Finally the landing gear is a 1/8" aluminum unit from TNT. The all up weight is 8.25lbs, which allows the OS 110 to move it around the sky nicely.

The result is a great sport plane good for up to intermediate IMAC.

RE: CG Extra 300
 

the pix.

RE: CG Extra 300
 

Nice build, I wasn't able to open the photos to full enlargement but it looks like it came out clean. Don't suppose you made a parts template?? I'm still in need!!!:(

RE: CG Extra 300
 

No, sorry, no parts template.

RE: CG Extra 300
 

One of the guys read your post and is making me up a set so my world is going to be a better place!!! This time I will make sure I never toss out my templates again!! My stupid!!
Not too many years ago the CG Extra was seen a lot in IMAC, it really is a wonderful plane!!

RE: CG Extra 300
 

Yes, I agree that it's a good and easy airplane to fly. I've also built the Great Planes Extra 300 S and though it's arguably a prettier airplane, IMHO the Goldberg version is the better flyer of the two. The lower wing loading and mid-wing design make for a more neutral and forgiving airframe.

RE: CG Extra 300
 

Looks great. Any idea how much weight you saved? 8.25lb is pretty light for that plane from what I've been told.

RE: CG Extra 300
 

I built one of the old Texas Twins kit Extra 260, it too was a very pretty plane, flew great but my old CG still flew better. Bipes did a great job on his build and made a good choice of engines too. Now for a report on how he likes flying it!!

RE: CG Extra 300
 

SmithCreek, unfortunately I have no way of knowing how much weight I saved, but I can tell you I did drill holes pretty much everywhere structural integrity wouldn't be compromised. An example are the wing spars, which IMO are way over-designed on this plane. I therefore drilled 5/32" holes vertically thru the spars every 1/2" or so for the last (outer) 3 rib bays.

Other than the holes, I try to go easy on the epoxy, using it only where absolutely necessary, like landing gear block mounts, firewall, wing joining, stab&fin mounting. Everything else was glued with either thin or medium CA.

Graybeard, I now have about 10 flights on the CG Extra and have experimented a little with props and C of G. I have settled on a C of G at the back of the recommended range, which allows me to fly inverted with only a little fwd pressure on the stick. The OS 110 seems to like the APC 15X6 best for this plane. Vertical penetration is pretty decent, but not unlimited. Still, it allows for all "classic" maneuvers this plane was designed for. Landing approaches are a joy, the plane coming in on a nice flat approach with no tip stalling tendencies. Compared to other aerobats I've flown over the years (the Caps and Gilles, most notoriously....) this Extra is a pu$$ycat.

A little on the engine. I think OS really got the design right on this one. Those hoping for 120 class power will be a little disappointed, because truthfully, the engine is not a powerhouse. What it IS, is a very easy-handling and clean running lightweight engine. It weighs virtually the same as the old OS 91 4-stroker, but produces more power. The lack of a crankcase breather (the oil is recirculated internally) helps keep the plane much cleaner than other 4-stroke engines. I ran one tank on the ground, then just flew a few flights 500 rpm on the rich side. The engine never stumbled and the only adjustment required was to close the low speed needle about 1/4 turn. Idle can be set very low and transition is excellent. Nitro is very expensive in Europe, but the OS runs just fine on the 5% nitro, 18% oil fuel I feed all my other engines.