Dirty Birdy Sport/Pattern .60 ARF Review - RC Groups

Dirty Birdy Sport/Pattern .60 ARF Review

Chris Mulcahy takes a look at the Great Planes ARF version of the classic Dirty Birdy.



Wing Area:690 sq in
Weight:7.5lbs - 8.5lbs
Wing Loading:25 - 28 oz/sq ft
Servos:Futaba S3004, Hobbico CS-63
Transmitter:Futaba 8J
Receiver:Futaba R2008SB
Battery:Nimh 2100mah
Motor:O.S. 65 AX
Manufacturer:Great Planes
Available From:Hobby Retailers

Joe Bridi is a pattern icon, both as a designer and as a masters level pilot. Back in the early days of pattern competition, most masters level pilots designed and built their own aircraft. Joe Bridiís designs are the most popular classic pattern designs of all time. Some of his more famous designs include the Sun Fli, Kaos, Dirty Birdy, Escape, XLT, and UFO. The Dirty Birdy was/is one of the most popular classic pattern planes of all time Ė and for good reason. Itís a very competitive pattern ship with an eye catching shape that is instantly recognizable. The Dirty Birdy is also a popular sport plane due to the honest flying characteristics. In the past, if you wanted a Dirty Birdy, you had to build one. To be honest, carving that sleek rounded fuselage from blocks of balsa was a daunting task. Later a fiberglass fuselage and foam wing kit was offered. The fiberglass fuse eliminated the carving and sanding, but a lot of work is was required to finish the plane, including painting.
Great Planes has now made owning your very own Dirty Birdy, without the need to actually build one, a reality. The new Dirty Birdy ARF holds true to its original design, and offers modelers a beautiful plane that flies as good as it looks!

Joe Bridi with the Dirty Birdy, circa 1975.

Kit Contents

The Dirty Birdy arrives in a large box, and includes many accessories to help you complete the model. As well as the airframe, you get all the hardware needed to assemble the model, including fixed landing gear, fuel tank, and a spinner. The fuselage is all fiberglass, and is incredibly light, with a beautiful glossy paint job to match. Out of the box, the covering on the wings and stabilizer was immaculate. However after a few days of sitting in the house the wrinkles started to appear, and everything needed going over with an iron. All of the parts were individually bagged and taped securely in the box, and I was pleased to see that there was absolutely no damage due to shipping.

Also provided for the review:
O.S. 65AX
Macs Quiet Tuned Pipe (and related accessories)
Hobbico Mechanical Retracts
Hobbico CS-63 Retract Servos
Futaba S3004 Servos
2100mah Nimh Flight Battery



Construction begins with the wing. The wing starts out as two pieces, which must be glued together to form a one piece wing. The ailerons are already glued in place, as are all the control surfaces, something that I am not particularly fond of due to misalignment issues that can occur at the factory. For the most part, the control surfaces were centered and all looked good. The only issue I noticed was that one of the ailerons was ever so slightly off center. I went back and forth a few times on whether or not I should cut the aileron off and re-hinge it, and ultimately decided that it was such a minor issue that I would leave it for now (I could always redo it at a later date).

I installed the aileron servos and their extensions, and installed the control horns to the ailerons. I planned on using mechanical retracts, but at this point I popped in the fixed landing gear to see how it looked. After removing the fixed landing gear I opened up the covering that concealed the pre made retract bay. Before installing the retracts I had to glue the wing halves together. Epoxy is the recommended adhesive for this process, and this is what I used to laminate the three piece wing joiner. The joiner is made up of a piece of aluminum sandwiched between two pieces of plywood. I took special care to make sure that I had epoxy smeared over the entire surface area of the aluminum, and used clamps to hold it together while the epoxy cured.

For joining the two wing halves together I chose to use "Gorilla Glue". I've used gorilla glue many times before on giant scale planes with great success. The main reason I wanted to use this glue on the wing halves was for its expanding properties. I figured that if there were any voids in the pockets where the wing joiner is located, the gorilla glue would fill them. I prepared the wing halves for joining by taping off around the edges of the root to protect the covering from any glue. I inserted the wing joiner into one of the wing halves, and coated the same wing half with glue before sliding the second half over the joiner. I then cleaned up any glue and taped the wings together to prevent any movement while the glue cured. At the last minute I threw on a few clamps for extra security.

After the glue was cured, I pulled off the tape and cleaned up what little glue had seeped out of the edge. It was then time for the retracts. The mechanical retracts were a drop in fit, and very straight forward to install. Most of the time working on the retracts was taken up with cutting and trimming the main retract servo bay in the top center of the wing. An exacto knife and dremel sanding drum were the tools of choice, and I soon had the bay clear, ready for the plywood mount and aileron servo. I bent the pushrods for the retracts per the instruction manual (which had templates) and everything functioned perfectly. I did use the sanding drum to cut away a little material on the side of the retract bay for the spring part of the strut, and sealed the exposed foam with epoxy. The final touch to the wing was to glue on the fiberglass belly pans with some thin C/A. I traced around the small belly pans and used a soldering iron to retrace the inside of the line, giving the thin C/A somewhere to run. With that, the wing was finished!


On to the fuselage! I began with the stabilizers. The stabilizers are glued to the fuselage, and have two carbon fiber tubes running through them for location and strength. I decided to install the elevator and rudder pushrods before actually gluing the stab in place, just to make things a little easier to work with. There are two pushrods for each elevator half, and they are connected to each other using two wheel collars. Coming from giant scale, I wasn't used to this kind of setup, but my friend reassured me that it worked just fine, and he was right. All of the measurements you need for the pushrods have already been worked out for you in the manual, which cuts down on assembly time.

I roughed up the fuselage with some sandpaper where the stabs connected, cleaned it thoroughly with some alcohol, and used epoxy to glue the stabs in place. I made sure that the carbon tubes had a thorough coating of glue also. Any excess epoxy was cleaned up with alcohol, and the stabs were secured with a little tape to prevent movement while the epoxy cured.

I had a couple of friends helping out throughout the build, and I must say that this was half the fun! Having a second set of hands (or a couple of sets!) definitely helps when you are working on a project like this. After all the gluing was finished, I moved on to the engine mount and fuel tank. The firewall is pre drilled, and the motor mount can be mounted sideways or right side up. We did a little experimenting and found that you could mount the O.S. 65AX either way. However, because of the tuned pipe I planned to use we decided to mount the engine sideways, allowing the pipe to run along the bottom of the fuselage. I cut the cowl to fit, free handing most of it, and only cutting off a little at a time until I was happy with the fit. With the engine mounted, and I moved on to the fuel tank.

Ah the fuel tank! There has been a lot of discussion online about the size of the fuel tank, and whether or not it is big enough to get a good amount of flight time. The stock tank is about 8.8oz. The instruction manual for the O.S. 65AX calls for a 350cc (11.8 ounces) tank for a 10-12 minute run time. My buddy Jeff picked up a Sullivan 16oz cylindrical tank (S414), and I decided to go with that. This new tank fit perfectly in the fuse with the two tank support formers removed. With the tuned pipe on the 65AX, running cool power 15%, with an 11x8 prop, I can run full throttle for just over 8 minutes. Using the stock tank with the same setup would have given me 4-5 minutes. That being said, you are not going to be flying full throttle for the whole flight, and there are other options such as adding a small header tank to increase capacity, but when all is said and done I am glad I went with the larger tank.

The final part of the fuselage assembly was the nose gear retract. Great Planes have provided templates in the manual for all the wire bending that you need to do for the nose gear. After cutting a few small holes for the pushrods in the nose gear retract bay, and installing the servos, the nose gear was completed in a very short amount of time. Even the length of the nose gear strut has been figured out for you, and you just have to measure and cut. At this point I also added the switch and charge jack.


I used the battery to set the center of gravity, and it ended up right underneath the servo tray for correct balance. No extra weight was needed, and the final plane came in at 7.5lbs dry. A quick check of the control throws, and they were very close to the recommended throws in the manual. I programmed the Futaba 8J that I was using with this plane, setting the throttle kill and setting the throttle servo. The pipe was temporarily mounted until we were able to take it outside and "tune" it.

Tuning the length of a header for a tuned pipe was also something new to me, and fortunately my friend Jeff had some experience with this. We used a tach to get some numbers from the engine, first with no muffler, then with the stock muffler, and then with the header and tuned pipe. We then started to cut a small amount of length off of the header (quarter inch increments) and re-tached the engine. Progressing this way saw the rpm's increase with each cut, and once that number started leveling out, we knew to stop cutting. We also had to bend the header a little so that the pipe would sit correctly under the fuse. A propane torch made bending the header a lot easier!

Numbers are peak using 15% Cool Power, OS 8 plug.
Stock muffler:
11x7 - 13,000
11x8 - 12,400

Macs long header cut to 4.5" and 1060 muffled pipe (there was no gain in RPM from 4.75 to 4.5"):
11x7 - 14,800
11x8 - 14,000

Full throttle run time with 16oz tank, 11x8 prop, on pipe at ~ 13,600 RPM. - 8 min 15 seconds. (Roughly 2oz/min)

Once all the engine tuning was finished, the Dirty Birdy was ready for its maiden flight!



Having run several tanks of gas through the engine on the ground, I was confident that it would be trouble free during its first flights. After topping off the battery and range checking the plane, it was time to start up the engine. The O.S. 65AX was easily hand cranked, and it purred contently with a smooth transition to full throttle. I taxied it about to get a feel for ground handling, and didn't find anything unusual.

Taking Off and Landing

I opened up the throttle for take off and the Dirty Birdy shot down the runway and eased into the air. I had to add a little right aileron trim, and then remembered that I hadn't balanced the plane laterally. Only a small amount of trim was required, so I continued the flight. I had to adjust my approach for landings, as the Dirty Birdy takes a while to slow down! It glides very well, and doesn't have any tipping tendencies during stall. Smooth landings were easy to accomplish, even if some of them were a little "hot" to begin with! Retracts up or down didn't seem to affect the CG, and it certainly looked pretty cool on those low passes with the wheels up. :-)

Aerobatics/Special Flight Performance

All I can say it "Wow". I'm not sure what I was expecting performance wise, but the Dirty Birdy blew me away with its flight characteristics. It's fast, and practically accelerates on up lines. It flies large maneuvers with ease, and can eat up the sky quickly. As for rolls, this plane LOVES to roll, and it does so extremely well. Few planes have I flown that roll as straight and consistently in BOTH directions as the Dirty Birdy does. I just couldn't stop, and the DB looked like it was on a rail throughout. Inverted flight required a touch of down elevator, and the DB didn't seem to care if it was right side up or upside down. Knife edge flight was equally as impressive, and it was then that it occurred to me that I wasn't detecting the need for any mixing, as the DB seemed to have no coupling. In fact, over the 15 or so flights I have on the DB now, I still haven't had to add any mixing at all.

Is This For a Beginner?

The Dirty Birdy was designed as a high performance competition plane, and flies as such. Not for a beginner.

Flight Video/Photo Gallery

Youtube Link


I am really impressed with the Dirty Birdy, it is a joy to fly and it performs extremely well. It definitely caught me off guard with just how good it is, and I still can't get the grin off my face each time I fly it. It was easy to assemble, looks great right out of the box, and is an extremely precise plane. I even found myself wishing there were some local pattern contests that I could enter it into. For now I am content to just chase the clouds and keep it rolling!

Pros Cons
Beautiful Finish Small Fuel Tank
Classic Design Aileron Hinge off Center
Easy to Assemble
Fantastic Performer

Last edited by Angela H; Jun 12, 2012 at 01:59 PM..
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Jun 12, 2012, 04:41 PM
Registered User
are those wing sheeted with balsa?
Jun 12, 2012, 04:42 PM
Team Futaba
CSpaced's Avatar
Yes, they are foam cores sheeted with balsa.
Jun 12, 2012, 10:49 PM
Registered User
Would a os 60 fsr work well? It looks just like the plane ive been craving for. Would this be a decent plane third plane or so? Im currently flying a scanner and i can fly the basic manuvers alright. I still consider my self a beginner since im learning everytime o go to the feild or am with in ear shot of a rc plane
Jun 13, 2012, 06:41 AM
Registered User
Looking good! love the multiple rolls, faaaaaast plane!
Jun 13, 2012, 10:38 AM
Team Futaba
CSpaced's Avatar
Originally Posted by scrubmonkey
Would a os 60 fsr work well? It looks just like the plane ive been craving for. Would this be a decent plane third plane or so? Im currently flying a scanner and i can fly the basic manuvers alright. I still consider my self a beginner since im learning everytime o go to the feild or am with in ear shot of a rc plane
My sources tell me that the .60 FSR would be a great match for the Dirty Birdy, with an 11x6 or 11x7 prop. It would also be a period correct engine, as it was released in 1974.

Originally Posted by enkei
Looking good! love the multiple rolls, faaaaaast plane!
Thanks! It is a fun plane to roll.
Jun 13, 2012, 11:34 AM
Registered User
Hi Chris,

Thank you for a really thorough and great review.

Glad your enjoying this wonderful throwback !! Hope this sparks even more ARF's of the same.........

Jun 13, 2012, 01:43 PM
Why you type so loud?
Generic Member's Avatar
Chris is a great pilot. He flys giant scale planes ( 3D and IMAC ). He can also wring the snot out of a helicopter. I don't think he understood my attraction the old classics.
I was planning on buying this plane from Chris once the review was over since he knows how much I miss my kit built DB.
Once he landed the plane after the first flight (the beginning of the video) and I shut off the camera, I couldn't help but notice the HUGE grin on his face. I knew right then the DB was no longer for sale...
Jun 14, 2012, 12:12 AM
Cranky old fart
Balr14's Avatar
I flew one like that in the 70s. It took me a hundred hours to build and 10 minutes to destroy. What size electric motor would it take?
Jun 14, 2012, 09:15 AM
Why you type so loud?
Generic Member's Avatar
Originally Posted by Balr14
I flew one like that in the 70s. It took me a hundred hours to build and 10 minutes to destroy. What size electric motor would it take?
There's a guy on RCU that built one with an electric motor. Here's the link:

Jun 14, 2012, 12:04 PM
Time for me to Fly...
Mr. Wiz's Avatar
Beautiful plane and nice review but you said a mouthful with your last two sentences. I had a Wind 110E for two that never saw any competition. Just not much happening in the pattern world these days. It's kind of a bummer more people don't want to compete.
Latest blog entry: Some new engines some older
Jun 15, 2012, 12:00 AM
Keep 'em flying!
adam757's Avatar
Fantastic video of a classic pattern plane! Love how it tracks so straight and true.Just can't go wrong with a Bridi design.:-)
Jun 15, 2012, 11:32 AM
Cranky old fart
Balr14's Avatar
Originally Posted by Generic Member
There's a guy on RCU that built one with an electric motor. Here's the link:

Cool! Thanks a lot. I've gotten real used to not cleaning sticky residue off everything and have no desire to go back.
Jun 15, 2012, 11:41 AM
CPA# 39
EscapeFlyer's Avatar
Bridi's color schemes present very nice in the air! Wish I could have seen him fly one of these!

The flying was a blast to watch! Thanks for posting!!!

Jun 16, 2012, 11:56 PM
Registered User
I can assure scrubmonkey that an OS 60 FSR would be a great combo in a Birty Birdy. I built a wood one from a Bluejay kit and it came out to 7 pounds 3 ounces with pipe and Rhom retracts and I use an OS FSR 61. Couldn't be happier with it. MIne turns a 11X8 APC 1,.500 on the ground and I don't have the pipe cut as short as I could because I like the way the engine handles with a pipe just a bit longer than peak length.

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