2M Dirty Birdy
 

I have one and wonder if there are any gremlins lurking in the box. I've built several of Joe's other kits and found them straight-forward. This looks the same, but I thought I'd check. I'll be putting a WVVS 1.6 in it and mounting gear on the fuse. TIA, Tex.

2M Dirty Birdy
 

I have not seen very much on this plane. It appears to be a scale up of the very popular 1974 design Dirty Birdy. This plane was designed for the pattern routines of that time which required limited knife edge ability and it flew fast with sweep wings and little fuse area. It would make a great sport plane but I have doubts that it could be competitive in modern pattern where one needs a slow wide body design with good knife edge flight capability.
PilotFrog

Big D. B.
 

Yup, but I know it will be a great flyer. I don't compete and like to use my thumbs, so I know what I'm getting into in that regard. I loved his XLT and Kaos derivitives so this should be another pleasing aircraft to fly. Tex.

2M Dirty Birdy
 

Absolutely correct. I just bought one of his last Dirty Birdy 60 kits. I do not compete in modern pattern either. All of Joe's designs are very pilot friendly....I would never think to fault any of his designs. You will be delighted with it for your type of flying.
PilotFrog

2M Dirty Birdy
 

I'm building Joe's Dirty Birdy 60 myself right now. Fuse is almost done! Starting on the Stab next week. A lot of fun to build, nice change from the typical commercial kits.

Dirty Birdie
 

Saberjock,

I scatch built a smaller version of the Dirty Birdie called the Tweedy Bird. On the second flight I put her in a nice easy spin. I don't like more than 3 turns on a new airplane until I am familiar with it's spin recovery characteristics. So at about 2 1/2 turns I started a recovery only to find that it made no immediate change in it's flight. Fortunately, after 2 more turns it recovered and I completed the flight with no problems.

After I landed a fellow club member that had a 60 size D.B. in the past came over and said "Nice spin-my 60 size would do a nice spin and not come out." And I said "Thanks alot for telling me that now, that nice nice spin lasted 2X longer than I wanted." He chuckled and said yea I know, you looked a little busy out there for a while.

My dear little Tweedy was done in by a Transmitter being turned on w/o the Freq. pin. I'm in the process of building another. I guess what all of this is about is that if the 2M D.B. has the same spin characteristics test spin it at a high altitude in the beginning. As I got used to the extra couple of turns in the spin I eventually tried a flat spin. After the rebuild, it flew just as well as before :rolleyes: .

Good Luck, I think you'll love it.

Mark

dirty birdy spins fine!
 

I have built and flown at least 5 D.B.'s in the past 23 yrs,, and have 6 more kits to go!
there is NO!!!! bad tendencies of spin recovery,, on any of mine when i released sticks on everyone i had there was IMMEDIATE stop of rotation,, this plane tracks and does what you want it to do to a tee!!i never had over rotation of one,, not one in probably after at least 2000 flights!!

im not saying your hasnt,, but if it does there must be a reason for it,, i dont think its in design,, but there are at least 2 other critical factors that affect spin,, CG,, and shape of leading edge,, you may have it too sharp,, im sure theres a thousand people out there that flew D.B.;s they were one of the most populay,, for good reason,, did anyone else have a spin problem??? did you find out why?? id be curious just dont want to find out on one of my next 6 i build!! maybe someone can help us all if there is a hidden flaw in design thanks all,,,RD

Dirty Birdy Spin
 

There are other factors that can cause a model to have a tendency to snap/spin or not recover. A wing warped with wash in, high wing loading, along with incorrect CG and sharp LE mentioned. Many WWII warbirds are bad for this mainly because of wing loading.
I had a Tweedy Birdy(.25 powered) and it came out a bit heavy since I used Coverite and painted it with SuperPoxy. It had the tendency to snap at low throttle when making approaches. Also a bit slow to recover from spins but never overrotated more than one turn when neutralized. Dead stick finialy did it in. Still have the plans and someday maybe I'll build another.
If you have a .60 size and it is in the 9+ lb range then you might expect to have spin recovery problems. I do not think that it will be a factor in the 2M Dirty Birdy as you have a much larger wing and the Renold's numbers work in your favor on the big birds.
PilotFrog

Say it ain't so
 

Ryansdad/PilotFrog

I agree with you that L.E. shape and C. of G. location are important to spin recovery.

On the aforementioned Tweedy Bird, the L.E. was sharper than Mr. Bridi calls for on the plans and the C. of G. was at the rear most of the range.

Even with all of that it blew my mind that this thing had such terrible spin recovery traits. With all that rudder below the vert.stab and generous horizontal tail volume I thought that recovery would be immediate or faster!

As far as (intentional) snaps go - WOW. As far as snapping on landing - never. ( Of course I never tried to grag it in like you can with a Kaos!) Knife Edge was coast to coast, Loops, what ever size you wanted. Power was a MECOA .32 w/ stock muffler.

As far as warps nope- no warps.

As far as any other D.B.'s the other one is my friend's, now that's going back 20 years. So no particulars on that one.

Would I build another You better belive it. I'll have one for next spring. I've built and flown several other Bridi designs and love all of them. I did want to improve the snap performance so possibly I did sharpen L.E too much, but I don't think so?

Finally, I'm not saying that the 2M D.B. will have this trait, however, my purpose in jumping in on this thread was to inform of my experience with a similar although smaller version of the airplane in question and that if it did have a similar characteristic it would be nice to learn about it with an extra 100 feet or so of altitude. Of course I think it's a good idea to investigate a new planes habits alittle higher than normal even if it's a "proven" design. Just my opinion.

Mark

Spins with the Dirty Birdy
 

Don't know how the 2M Dirty Birdy spins but knowing Joe, I expect it will spin at least as well as the 60-size. I flew a OS .91 -powered Dirty Birdy 60 this past season in SPA Expert where the last maneuver was a 3-turn inverted spin. With the right amount of elevator, the DB will give a nice, sharp stall break (required in the maneuver) without dropping a wing until you throw in rudder (with some aileron to get it rotating quickly). It will spin fairly slowly and will break out of the spin very crisply when controls are neutralized with almost no overshoot (1/8 rotation or less). It will do this very consistantly in wind or no wind. My DB weighs in at 7 lbs dry and the CG is at 40% MAC.

I've experimented with the CG and have had it as far back as 55% MAC with no nasty surprises, it just doesn't track quite as well in loops as it does with the CG at 40%. By the way, it definitely knive-edges quite well if it's kept light.

The Big Dirty Birdy...(2mt.)...
 

You were asking about any "Gremlins" in the box ?
I just put one up this year. Glass the whole fuse
with some thin cloth, and about 1 ft. wide in the
center of the wing. The tail feathers are ok....just
resin and paint.

Dave. :)

2M DB
 

Dave, It looks like you sheeted the wing too. What's that up front? I'll be puting gear on the fuse. Tex.

Saberjock...
 

.....mines not sheeted, it's open-rib. Covered with that
Hanger 9 UltraCote from Horizon....yellow w/silver polka
dots, and the carbon/kevlar on the control surfaces. The
underside of the wing is done in big 2" checkers.

Up front is a S.T. 3000 (1.8), but I'ts vibrating the plane
apart. Gotta figure out the engine balance, or put a
different :( motor in it.

Large S.T.'s
 

Dave, If you can, trade the 3000 for a 2500. I've used both a lot when I was into slime and the 2500 is far smoother and has the same H.P. just operates a bit faster. I think the new line has a 2350? which should be good too. Tex.

2M Dirty Birdy
 

I've got 3, 3000's now....the first one I put in the D.B.,
and it is not useable. After about 6 short flights....it
litterally "powdered" the balsa around the CA hinges
on the tail surfaces. You would have to see it to believe
it....the rudder almost fell off, and the elevator is about
half loose. :mad:

I've never seen a plane vibrate that badly......

Dave. :(

2M Dirty Birdy
 

I'm glad we talked. I'll put H.D. Kletts in mine, because while the WVVS is a pretty smooth runner, it still shakes. The larger props create quite a bit of pulsing as the air goes by the tail feathers too. Tex.

Yo, Tex.....
 

....I'm gonna rubber mount a Magnum 1.20 in mine I
guess, and putt it around . I have the plane set aside
now, because I've been messing around with it for
months, and it needs another going over. I can't tell
you how dissappointed I am with the S.T.'s. Like i said
I got two more of them for other big plane projects, and
the one I tried is UNUSEABLE. :mad:

I got some Robart #308 steel pin hinge point jobbers
I'll try in the Big Dirty Birdy. I'll put a bunch of them in
this time.

Tex...DO GLASS THE FUSE, and "dry it up real good" with
the squegee to remove as much resin as possible.