Detailing the Dirty Birdy

Feb 25, 2013 3 Comments by

Great Planes has been my favorite hobby supplier for decades. OS Engines power my planes, and their ARFs, especially the Top Flite warbirds, are excellent quality and top value.  GP products have served hobbyists well over the years.  When they resurrected Joe Bridi’s Dirty Birdy pattern ship it seemed like a great idea for us old timers and for everyone else looking for a smooth flying, classy looking aircraft.  I could hardly wait to get mine.

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The Dirty Birdy has been reviewed in Model Airplane News and several other venues.  The reviewers loved the plane, especially its flying characteristics.  Our purpose here is to make a few suggestions that make the assembly process more unique.  I’d say at the outset if you do get one you will love the way it flies and its overall quality.

There are three tasks I find tedious when assembling an ARF.  One is hinging.  Another is drilling and aligning the horns on all the surfaces.  I’m not a fan of cutting out cowls either.  As a bonus dislike, I’ll include installing retracts, both mechanical and air.  There was a time I actually liked these activities, but now that most of my building days are behind me, I’m really spoiled.  The more complete an ARF, the happier I am.  I want to fly, not spend my time in the shop.  Florida living does that to you.  That being said, its good news on all accounts with the Dirty Birdy!

For starters, all flight surfaces are finished-hinged out of the box, including gluing.  Hooray on that one, especially since they got it right.  Everything on my plane was aligned correctly thereby saving several hours, including some CA cleanup time with the debonding agent.  Being too aggressive with the CA is an occasional mistake I seem to make.

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Drilling for the horns was next.  Another great feature of the Bird is that the plywood horn pads are pre-installed and covered on all surfaces.  They are easy to locate, are very strong, and they make alignment a snap.  The job is really easy with the Dirty Birdy since the horizontal stab is installed on two carbon rods perfectly squared with the fuselage.  Rather than glue the stab halves on, I plugged them onto the tubes, marked the horn locations, and then removed the stabs to install the horns.  It was much easier that way than wrestling with that beautiful long fuselage if the stabs had been permanently attached.

When drilling for the horns try making one 1/16hole carefully and then enlarge it with a 5/64” hand held drill bit.  After installing the horn with the one bolt and backplate, lining up the second one is easy.  Just drill through the horn hole after starting it with a “T” pin, and then enlarge it until the bit sticks out a little on the other side.  Remove the drill bit, install the second bolt, and you’re done.   I’ve used this method for a long time, and it worked beautifully on the Bird, especially because I was holding the stab halves in my hand when I did the work.

I installed an O.S.61SF, an engine that was very popular in the late 1970s.  It is an appropriate choice for the Dirty Birdy!  I also substituted a slick looking black Macs muffler for the stock OS.  It really looks good on this plane, and it saved me four ounces of unnecessary nose weight as the OS weighed six+ ounces.  The plane balanced perfectly; total weight was only eight pounds, one ounce, right in the middle of the range in the instructions.

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Trimming the cowl was a drag, but it turned out well, and the Dremel did the job.  The cowl is top quality.  Be sure you align it correctly.  Mine measured slightly longer on one side than the other to allow for what looks like a bit of right thrust.  Four screws through the cowl into the edge of the firewall made a very solid mount.

Tri-gear retracts make the Dirty Birdy complete.  Like warbirds, pattern ships need retracts.  The Hobbico mechanical retracts are nice simple units and are recommended for this plane. The manual is very detailed and describes this installation perfectly.  To me, the downside of all mechanical systems is installing the servos and getting the wire actuators working smoothly.  Since the Dirty Birdy is a tricycle geared plane, that meant two servos and a steering pushrod in addition to the nose and main gear actuating rods. Compound that with a tight fuselage, and that system had me looking in another direction.  Air retracts have their own issues including the air tank installation and lines, extra field gear, and again a tight installation.  That only left one choice … electric retracts.

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I’ve become addicted to the Hobby King electric retract units in some of my warbirds.  I have a set in my Hangar 9 Spitfire and another in my Top Flite SNJ.   They are really nice and are reliable, inexpensive, and very simple to install.  A pair of these costs less than $16 with a few bucks added for shipping.  5mm struts are required, and the units are rated for planes up to 10 pounds.  They can handle more than that.  I use Top Flite struts in them exclusively; the TF Mustang 60 and P-47 60 struts work well at a price of under $9 a pair from Tower Hobbies.

I used a set for the mains in the Dirty Birdy.  The retracts dropped right in and fit perfectly on the rails with very minor trimming.  The complete units are smooth operating and very strong!  I touched up with red paint, and taped the wires with Scotch tape which works quite well and is durable.

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The HK electrics wouldn’t work as a nose gear because of mounting issues.  Even the unit they sell for that purpose would have required a significant installation effort because of the way the Dirty Birdy nose gear bay was configured.  It is sometimes difficult to make modifications in ARFs.  A simple solution was to go with a mechanical nose gear from Hobbico, the one recommended in the instructions.  I used a separate servo (a 180 isn’t necessary) for actuation, and another for steering which allowed an easy install.  I mixed the three gears to channel five and adjusted the speed of the nose gear servo so the retract cycle speed matched the electrics both up and down.  I also mixed the steering servo on a switch as a slave to rudder so that the steering rod doesn’t move after takeoff.  I switch steering off in the air and actuate it again for taxiing back to the pits.  I don’t like to couple steering to the rudder mechanically; it seems to me to be a snafu waiting to happen.

Speaking of weight, there was no penalty with my hybrid retracts; two servos and three retract units are the same requirements as an all mechanical setup.  The electrics were also much easier to install, and I think more reliable.  There are no worries with the main gear hanging up, since the electrics have a fail safe and will not burn up your flight pack.

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I finished the Dirty Birdy by adding some homemade decals and cleaning the plane with spray car wax which helps keep the goop off.

If you like to fly smoothly and think it’s really neat to fly huge loops, stall turns, Cuban eights and all the rest, you can’t go wrong with the Dirty Birdy.   Old-time pattern is back! Everyone at the field loves it too.   —–Tony  Iannucelli

 

Equipment used in the Dirty Birdy:
JR 9303 Transmitter on 72Mhz

JR 950S 10-channel receiver

Hitec 7965 x 2 for ailerons

Ace DS1213 x 2 for rudder and elevator

Tower Hobbies digital TS-150 for nose gear retract

Hitec 5645 for nose wheel steering

Hobby King electric retracts on mains, 10 pound capacity

Hobbico mechanical nose gear

O.S. .61 SF engine with Top Flite 11 x 8 propeller and Macs muffler

Kraft/Hayes 12 ounce ‘slim’ fuel tank

 

 

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3 Responses to “Detailing the Dirty Birdy”

  1. Tony Iannucelli says:

    After a dozen or so flights I think I’ve got the Dirty Birdy almost perfect for my limited style of flying. It didn’t take much. The retracts are working great, and the new-old OS61SF is running really well. It is a long stroke engine and I’ve switched to an 11-10 prop from the 11-8. It runs quieter, with more authority in the ballistic verticals. It is very fast. Landings are great too. Nose high on our grass field after a long run on final. This is a really nice plane. —Tony Iannucelli

  2. Dorin Mantoiu says:

    Hi there, which electrical retracts did you get from HK as I can’t see any at the price you mentioned.
    Many thanks,
    Dorin

  3. Tony Iannucelli says:

    http://www.hobbyking.com/hobbyking/store/uh_viewitem.asp?idproduct=14838

    Hi Dorin. The above link will get you to the retracts. –Tony Iannucelli

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