bentwings

What is the dihedral of the wing on the DirtyBirdy?? ...dead straight down the center line, flat across the top, or some value greater??

You would think I'd remember this having built a dozen or so of them back in the day along with the UFO's and MK Arrows I had....it's just been too long. haha

I do remember cutting a wing apart and epoxying it back together on advice of a couple of the respected pattern guys back then. I don't even remember the condition it was supposed to correct.

Thanks

doxilia

My Feedback: (3)

Probably knife edge tuck.

I'll check the plans for dihedral although someone else will likely draw faster

David

MTK

If I recall, set the dihedral with wing upside down with a 1/4" block under the center.

Poor dihedral angle causes roll coupling with top rudder application.

If the wing has less dihedral than necessary, (flatter than necessary),you will get adverse roll couple which means the wing will roll in the direction opposite applied rudder-ie- left rudder produces right roll couple

If the wing has more dihedral angle than necessary you will get proverse roll couple. Means the wing will roll in the direction of applied rudder-ie- right rudder, right roll, sorta like a top wing trainer that rolls with rudder to make a smooth turn.

dbacque

My Feedback: (3)

The plans don't show the dihedral but the instructions state "turn the wing panels upside down and move the root ribs of both panels together. With the spar at the tip rib down on the building board, block the center of each wing panel up 3/8" of an inch."

Yes, it says 3/8" of an inch.

Dave

MTK

It's been over 30 years since I built the last dirty birty. Memory isn't what it used to be but heck, I was pretty close, eh?

doxilia

My Feedback: (3)

Dave,

I checked my RCM plans and the dihedral is shown (per the instructions above you posted) just above the center of the fuse top view (see attached). Are you referring to Blue Jay plans that don't show the dihedral?

David

bentwings

That's great information. Thanks

I'm just starting on a project. the plane is called "The Monster" from plans from Flying Models I think. About 1981. I got plans from AirAge plans. It's a 90 in version of a modified DB as close as I can tell. There are no instructions at all and there is only a 3 article story about it. Overall the construction is nearly identical to the DB except for a foam stab. The stab is a diamond airfoil which had some popularity at the time as i recall.

I have to eat dinner so I'll be back. yum yum

Thanks guys

dbacque

My Feedback: (3)

Yup. What I quoted was from the instructions in a Blue Jay kit. But that's not a bad thing. BlueJay plans and instructions are straight from Bridi as purchased by Blue Jay. And most importantly, a Blue Jay Dirty Birdy built to spec is an awesome flying airplane.

Edit: Yup, the plans often show more than we see. Doxilia is right, the Blue Jay plans show exactly what he pointed out in exactly the spot he pointed out. Did I say their plans were straight from Bridi? I did a quick once over and didn't spot the dihedral but I knew where the instructions were and went for that. Doxilia got it right, same number but yes, it's on the plans. And the Blue Jay plans are identical.

Dave

bentwings

Wow that was great dinner. My wife broiled a sirloin steak.....the first in many months. Pink in the middle, a little corn on the side.

Anyway here is a link to the AirAge plans.
http://www.airagestore.com/the-monster.html

I tried to add the pdf of the articles and the page with the picture but there is a "non recoverable error" on the page and it won't down load here.

It is very similar to the DB only with a shorter nose to make up for the weight of the big gas motor. G-62 in my case. It will have higher compression and a tuned pipe (muffled). probably 20-12 or 18-14 prop for higher rpm. The plane is really clean. It's only 4 1/4 in wide. The airfoil is quite thin for this size plane...3". 1650 sq in better than twice the DB. It should come in about 18-19 pounds if I can build light for a change.

I'm going to do just a little Solidworks on it to get the servos positioned just right on some kind of servo mount. I also want a more realistic canopy so thanks again for the drawing. I'll use it for reference and not scaling.

This will be just a sport plane for me. I saw this plan set years ago and I always thought it would be a fun plane to have. I would like a rear intake motor so maybe I'll break down and get a DA or something else in the 50-60 cc range.

If it still is not fast enough our 5.8 will silp right in.

To answer the original question.. I think I'll make the wing flat on top but build it with a 3/8 thick W-1 so I can saw it in half if necessary. I really wanted wing tubes but the first wing will have to be one piece so it can be easily reworked. then I can build a 2 piece wing. Transportation is not a problem as I have a 1 ton dually with an 8 ft bed and a 34 ft Goose Neck trailer if necessary.

I'll do a build story on it when I get started.

Thanks again for the help

bentwings

doxilia

My Feedback: (3)

How apropos for you to be asking about dihedral bent wings!

Took a peek at the photo of the Monster - looks a bit more like a Deception than a DB. But that matters little other than the fact that the Deception has a flat top wing and a rather different airfoil.

I'd be interested in reading the articles when you're able to post them. Note that the PDF's have to be 6 MB in size or less to upload.

David

cvint

Is the Dirty Birdy airfoil the same as the Sun Fli 4 airfoil (also a Bridi design)?

doxilia

My Feedback: (3)

If memory serves, the Sun Fli has a similar or identical foil to the Kaos - very thick. The DB has a 15% NACA foil which has a max thickness further forward than the older models. The UFO is even thicker particularly the stab.

Putting the stab and wing foils of each design side by side would be illustrative.

David

bentwings

I agree on the DB vs the UFO. I have a partially completed UFO and the wing is much thicker and rounded than the DB. they flew a bit slower and mine seemed to land much slower or at least they could be flown at a lower speed.