Dirty Birdy Build Thread
 

I don't think there's a build thread on the Dirdy Birdy, so I'll start one.

This is a Bridi kit from ~2001 based on the newspaper that was stuffed in the box as padding.

I will be using a new NovaRossi C60F with a tuned pipe. Southern Pro Retracts (main gear) set up as a tail dragger. Other details like servos and hardware are TBD.

The box includeds a bunch of balsa blocks, some ribs, sheeting, some sticks and a smatterning of hardware including a nylon motor mount.

The plans are well drawn and I believe one could easily scratch build this plane from the plans.

The instruction manual is more or less a novel with no pictures or illustrations.

It looks like there will be plenty of carving and sanding on the fuse to make that elegant shape. I really enjoy carving and sanding. I find it therapeutic. ;)

Here's some starter photos...sorry about the quality, I took them with my phone.

RE: Dirty Birdy Build Thread
 

Hi:
The Dirty Birdi is a GREAT plane, I've built 3 of them all .40 size as trikes. These may well be the best flying models I've ever had, good choice. Here are a couple of pictures of mine.
Frank[img][/img]

RE: Dirty Birdy Build Thread
 

OOPS!
messed up 2 of the pictures but you get the idea
Frank

RE: Dirty Birdy Build Thread
 

Very nice Dirty Birdies there acobra! I love the black one!

I'm building the .60 size.

RE: Dirty Birdy Build Thread
 

Cool.....I have a 40 size in the bones that I will finish one of these day. I built it from scratch as I was building one from a kit for I guy who used to be in our club. I had a DB 40 back in the 80's when I was a kid and couldn't resist the offer to build one again, although his and mine have foam wings since I have a foam cutter.

RE: Dirty Birdy Build Thread
 

Here is a (stock) photo of the engine and pipe. I ordered them from plannethobby.com for $200 as a combo. I hope it lives up to is performance numbers.

High Speed Ball Bearings; Bushed Rod; True ABC Piston Sleeve Design; 8 Intake Ports; Weight 22.5 oz. Power: 2.3 H.P. at 16,500 RPM; 17mm Shaft; 1/4 x 28 Threads; Standard Glow Plug

RE: Dirty Birdy Build Thread
 

Time to start the Dirty Birdy. I am waiting, as I have an interest in that plane.

Crankpin

RE: Dirty Birdy Build Thread
 

Allthegoodnamesaretaken,

YOU DA MAN!!!!:D I'll be following your thread with keen interest. I'm sure I'll learn quite a few things following your build. That Rossi 60 and pipe should make your plane Ballistic.

Thanks so much for doing the build thread.

RE: Dirty Birdy Build Thread
 

Thanks guys. Right now I'm studying the plans and instructions. Seems pretty straightforward. Right now I've got a 35% on my big building board that's just about framed up, but since I'm single, I might just start the DB on the kitchen table. :D

Anyone know if the Dave Brown / Southern Pro retracts will hold up to an 8lb bird?

RE: Dirty Birdy Build Thread
 

Call 'em up. DB Products: 513-738-1576.

RE: Dirty Birdy Build Thread
 

Those gears will be fine, even with 5/32 wire. We used to use them with planes of 10+ pounds.

RE: Dirty Birdy Build Thread
 

Went Flying.

RE: Dirty Birdy Build Thread
 

OK, the kitchen table it is... :D

I got all the pieces sorted by sub assembly.

RE: Dirty Birdy Build Thread
 

I joined the fuse halves and lined them up using a straight edge and some angle stock. I glued the doubler in place and weighed it down until it was dry.
By the way, I'm using Titebond 2.

After the glue was dry I pinned the fuse halves together and lighly sanded the halves until they were identical.

Now it's time to mark the bulkhead locations on the fuse sides.

RE: Dirty Birdy Build Thread
 

Gotta love the Dirty Birdy. If I may offer a few notes on construction, check this thread http://www.rcuniverse.com/forum/m_47...tm.htm#4768795

In particular I had a small issue with the position of the wing dowel holes and offer a simple fix in the referenced thread, along with a few other notes.

Unfortunately the Dirty Birdy in that thread was recently demolished but the kit for the next one is already in the closet.

Best wishes on your project.

Dave

RE: Dirty Birdy Build Thread
 

Thanks Dave. Your DB looks very nice. The Bridi kit doesn't hve the holes pre-drilled for the wing mounting dowls.

I've run into a small snag. Former 3 is 1/4 inch shorter than what it shows on the plans. I'm studying the plans to see if I'm interpreting them wrong or if the former is cut wrong.

I got my NovaRossi yesteday. :D It's beautiful! This engine has in-flight mixture control. Someone educate me on its use. Why and when would you want to adjust the mixture in-flight?

RE: Dirty Birdy Build Thread
 

The plans show bulkhead #3 has vertical grain. Try turning it 90 degrees. The fuselage is exactly as wide as the fuse top. The sides are edge glued to the bottom of the fuse top, the triangle stock is added and then the whole corner is carved away. (Did that make any sense?) I kept thinking the parts were wrong too.

You're right, the wing dowel holes were not predrilled. But the instructions have you drill them before fuselage assembly. My point on the other post is that if you drill them after setting the wing incidence you'll be able to position them exactly where needed.

Dave

RE: Dirty Birdy Build Thread
 

Thanks Dave.

The photo shows that the bulkhead is orientated with the grain verticle. I tried turning it 90, but there's no way it would work. Take a look at my photos. I'm just going to cut a new one.

Got ya on setting the wing incidence. [sm=thumbs_up.gif]

RE: Dirty Birdy Build Thread
 

After one season of flying my Deception with 5/32" struts, I switched over to 3/16" struts. I got tired of having to bend them back so that they would retract cleanly without hanging up.

We had to land downhill during the first half of the year and our grass field was really rough. Try that with an eight and a half pound Deception and you'll learn very quickly that 5/32" struts aren't up to the job.

However, had we had a smooth, level runway, the 5/32" struts might have been just fine.


Ed Cregger

RE: Dirty Birdy Build Thread
 

Well, we flew on a turf farm, so I guess we were lucky. It was pretty smooth

RE: Dirty Birdy Build Thread
 

Laminate some Carbon Fiber to one side.
You may also try some 2 oz glass cloth. Should help.
I don't know which is easier for you, make new former or laminate.
Your pick.
I would use CF.

Crashlander.

RE: Dirty Birdy Build Thread
 

I've made a new former #3 and carved out the hole for the pushrods. I deviated from the instructions in that I've joined the fuse halves together with the formers instead of glueing the formers to the top block and then bringing the fuse sides together.
I've also mocked my engine and mount together and determined that the firewall had to go back about 3/16. I wanted to side mount the engine so the pipe exited under the plane, but with 2 deg down thrust, the pipe would be angled up into the wing.

Once the firewall cures I'll add the top blocks. I might wait to add the bottom block unil I get pushrods installed.

RE: Dirty Birdy Build Thread
 

A few more.

RE: Dirty Birdy Build Thread
 

You won't need the downthrust on the DB if you don't jack the wing's leading edge into positive incidence.


Ed Cregger

RE: Dirty Birdy Build Thread
 

**

RE: Dirty Birdy Build Thread
 

Ed,

Why did Joe design it that way with 2 deg down thrust and ~1 deg pos on the wing?

RE: Dirty Birdy Build Thread
 

Dirty Birdy Build...

The following posts are to provide additional perspective about the historically relevant Joe Bridi, Dirty Birdy. The work was completed the Fall of 2006.

My kit is from the last remnants of Joe's inventory featuring the built-up wing. I sent the wing plans, root and tip ribs to the new owners (circa 2006) of WING Manufacturing, to create a set of foam wings. WING, I believe, is now in Michigan and should therefore, have the wings available?

The photos show how I prefer to mount retracts (conventional) using a light plywood box which is glued into the wing prior to sheeting. The design provides for using the top sheeting, bottom sheeting and the foam to provide a significant amount of strength with weight LESS than a conventional 1/4" plywood plate and dowels. It is very important that the "box" fit very snugly for the most strength and least amount of glue. I add a 3" square piece of 3/4 ounce glass closth on the top and bottom of the box, between the sheeting prior to the sheeting process.

The cut-outs are made using 1/8" light ply templates and Sam Turner's KISS System...good luck finding this must have little gadget. The retracts are EZ- Supra for .60 size models from Central Hobbies. The 5/32 piano wire struts will be replaced with titanium versions also from Central Hobbies...much lighter.

Scheduled work shop time October 2008 - November 2008.

Rusty Dose
Team Futaba
Team YS Parts and Service

RE: Dirty Birdy Build Thread
 

Dirty Birdy build...

This post is to provide an additonal perspective on building the Dirty Birdy. The techniques have been stolen, copied or adopted by me from many of you and in no way do I take credit for their origination.

Just as an earlier post described, my rear fuselage former was too short so I added a filler piece. The hole was cut with forstner bit.

The elevator pushrod is mounted to the rear, the rudder servo is elevated with 1/4" light plywood and will use cable for actuation. The elevator pushrod uses an MK item which puts the elevator pushrods on the outside of the fuse with very short rods driven by an arrow shaft. It is very tight, remains tight over time, requires no maintenance. Some builders have changed the drive pushrod to cables by fabricating a new horn.

The model will be powered by an OS .61 to meet the SPA rules by keeping the retracts down. The photo shows a white shim added to the left nylon engine mount for "right" thrust. The tank plumbing detail was executed prior to gluing the various top blocks in place. The Rossi .61 is shown with the Scott Anderson "Deception" canopy and the stock plastic canopy...it would be pretty cool...?

Rusty Dose
Team Futaba
Team YS Parts and Service

RE: Dirty Birdy Build Thread
 

-


My theory is that the old guys from that era were still designing models with reed flying setups. Old habits die hard. Another thing that is detrimental to model designing and thinking is flying full size planes. Many general aviation pilots can't shake their old habits when thinking of models, or designing them. That is one of the things that ruined many of Sig's earlier model offerings.

We fly models in an almost continuous circle, or stretched lines with quick turns. Full size aircraft (an older reed sets or escapement models) were designed to be stable and fly for extended lines. As a result, the models did not fly all that well. This is just me analyzing the situation and nothing more. No one has to agree in the slightest manner.

Downthrust is mostly used to defeat zooming when power is applied. This assumes that the model will climb because of an assymetrical airfoil, which is biased to provide lots of lift with increased airspeed, or a wing that has been canted with the leading edge going up (positive incidence). Again, this is a holdover from the days of yore and is totally unnecessary, in fact is detrimental to a model supposed to perform equally well whether upright or inverted.

It is also possible that downthrust was used to offset the drag of the fuselage above the wing, which will make the model move toward the canopy side of the model when in knife edge flight. Cancelling this move with downthrust is also accompanied by unintended consequences in other flight modes.

It all depends on which way you feel comfortable in compensating for idiosyncrasies that pop up after we make our "best compromise choices". If you don't mind holding a bit of down elevator in knife edge flight, then the downthrust isn't necessary. But be sure that you are going to be holding a correction some place else in another flight mode.


Ed Cregger

RE: Dirty Birdy Build Thread
 

One of my most unforgetable memories is how precisely solid and stable Joe Bridi's Dirty Birdy seemed to fly through the pattern at Lake Charles in the mid '70s. Out of all the great flyers that I observed back then, those JB/DB flights left the longest lasting impression. He surely knew a secret or two about how to set up (and fly) an RC pattern ship. I'm gonna build my (at least the first one) Dirty Birdy to that spec.

It seems similar, to me, to the way B. Hebert advises to set up a plane with some 'triangulation' to create solid, predictable flight behavior. Works on planes on G3.5.

Terry in LP

RE: Dirty Birdy Build Thread
 

-


The beauty of modeling is that everyone can have it their way. I just love to speculate about history and their design concepts.

I don't suppose for an instant that I know a millionth as much as Joe Bridi. He is my design hero. Yet, I have improved upon his original specs "for my style of flying". I'm sure that if everyone builds their models absolutely stock they will have superb handling models.


Ed Cregger

RE: Dirty Birdy Build Thread
 

Thanks for the photos BERUSTY. Your plane is looking good.


Ed,
I fullly understand your thinking and appreciate your post. I had already epoxied the firewall in place though so this one is going to be built stock. Like you said, it should fly great.

The attached photos show the tank top block that's been relieved a bit on the inside as per the plans. - I guess for fuel tank clearance.

I've got the rear top block glued in place.

Next will be the front top block and finishing out the nose. I'm going to save installing the rear bottom block until I get the pushrods in place.

Cutting the slots in the side of the fuse for the stab is going to take some time.

RE: Dirty Birdy Build Thread
 

I kept thinking about side mounting the engine, and I decided to go ahead and make the modification. I removed the firewall and made a new one. In doing this I discovered that the firewall is also cut incorrectly. It's the right width, but the one supplied in the kit is cut square instead of rectagular as shown on the plans. So, now all is good. The firewall is the correct dimension and the engine will now be side mounted. :D

RE: Dirty Birdy Build Thread
 

I've got the nose block beveled and installed. I need to fit a piece to the upper nose block to fill the hole that would normally be filled by the upright engine.

At this point I'm trying to decide if I should build a hatch to get to the tank or just open up former #2. I wont fit the chin block or tank floor block until the wing is done. I want to be able to access the front side of former #2 when I drill for the wing dowls.

RE: Dirty Birdy Build Thread
 

Rusty:
That is a nice set up. I'll be doing essentially the same set-up with one additional item; and that is to honeycomb the wing and add some CF reinforcement via a balsa-CF-laminated spar on each wing section top and bottom. I can guess at removing about 0.5 ounces per panel. This may not sound like much, but it is removing weight from the outer most portion of the wing, keeping the mass of the wing closer to fuselage. This allows fore better snapping and roloing manuevers, it stops instantly.
I'll do a little build thread on hoeycobing. I too did not imnvent that system, but copies from others.
I do this on my AMA pattern planes presently.

Crashlander

RE: Dirty Birdy Build Thread
 

Easily will hold up to an 8 pounder. If you are not comfortable with that, then save yourself some weight as follows:

Cut the steel struts leaving about 1" stub. Epoxy carbon tubing directly over the stubs. Cut the carbon tubes to length desired and also glue in a set of aluminum axles to the bottom. You will save about 3 ozs total and will make the gear actuate easier with the typical retract servo

MattK

RE: Dirty Birdy Build Thread
 

An even better solution to the KISS is the Hot Knife. This is a simple handle with a 5" long rod that gets heated hot enough to melt foam. You only need to work from one side of the foam and really don't need templates. A 12V 1A supply is required to drive it. If I remember right, I bought it from CST.

It's nothing more than a length of nichrome wire, insulated with ceramic insulation and inserted into a 1mm stainless tube. The distal end of the tube is crimped directly onto the NiCr. The proximal end's insulation is passed through the tube without grounding out. That's the trick. The electrical connection is made between the proximal end of the NiCr and the stainless tube, to complete the circuit. Extremely simple idea and extremely functional

MattK

MattK

RE: Dirty Birdy Build Thread
 

Matt:
Does the CF hold up to rough landing such as landing on grass.

Orlando

RE: Dirty Birdy Build Thread
 

I wasn't aware of them. I found a quote on the website:

"As a rule of thumb, titanium has only three fifths the weight of the steel used in steel struts. So if your steel struts weigh in at 60 grams a pair (roughly 2.12 ounces), you can cut 24 grams off the gross weight of your plane by simply switching to titanium struts of the same diameter and length. Yet, while saving weight, you also add a lot of durability and strength to the landing gear."

Only catch is they're $17.95 a piece.

Tom

RE: Dirty Birdy Build Thread
 

They also bend, and, once they are deformed, throw them awayexpensive.

Crashlander