RE: Dirty Birdy Build Thread
 

good looking plane.

RE: Dirty Birdy Build Thread
 

Conventional gear with a swept leading edge is okay on paved runways, but not practical for grass fields.


Ed Cregger

RE: Dirty Birdy Build Thread
 

The plans show a location for conventional gear that is 3 1/2" in front of the CG. The plans do not show a wheel well location or any retract locations for conventional gear. I ended up locating the retract in the 4th bay which located the wheel well in the second bay just ahead of the spar. This puts the main gear at 4 1/2" in front of the CG - 1" farther forward than the plans show. The gear will also be about 3/4" taller than the fixed gear.

I made 5/32" 5 layer plywood rib doublers for the retract plate which is also 5/32 5 layer plywood.

The location of the wheel well required trimming the lower balsa spar. I re-inforced the spar with a 5/32" shear web.

The wheel wells are 1/8" A grain balsa. I just have to cut them to the proper length and cap them. Then I can sheet the leading edges of the wing.

The last photo shows the CG location - It's the thin balsa strip behind the spar.

I really don't think the conventional gear is going to pose any problems with nosing over. I've had a couple P-51's and never ended up in the "warbird pose". ;)

RE: Dirty Birdy Build Thread
 

Jeff,

I am thinking that adding the shear web may not be enough to make up for the lost strength due to material removed from the spar. Keep in mind that you have removed material near the center of the wing where the bending loads are going to be the greatest. I think that adding a small plywood doubler (1/16 or 1/8 thick, the same depth as the spar) with the main grain running in the same direction as the spar might be a safer alternative.

Good luck,

Teo

RE: Dirty Birdy Build Thread
 

All and Teo


I agree , the picture shows my twin spar because I never play Russian roulette.
(Picture is of a Taurus wing used on an Orion).
Also the D-Tube is already disturbed, sheeting and silk and dope (folie) are removed on that wheel location.

Cees

RE: Dirty Birdy Build Thread
 

I don't see how adding any more material to what I have is going to add any rigidity over the original construction.

RE: Dirty Birdy Build Thread
 

All, This would be ideal

Cees

RE: Dirty Birdy Build Thread
 

Cees,
Nice graphics! I understand what you're saying, but I feel the 5/32" ply epoxied to both halves of the cut spar, lower spar and both adjoining ribs makes a solid structure. We'll see after the first couple of blenders if the wings fold. :D

RE: Dirty Birdy Build Thread
 

I'll be off from work the rest of the week so hopefully I'll get some more done on the Dirty Birdy. I'm having ShockWave therapy done, not to be confused with Shock therapy - which I've been told I could also benefit from. [&:]

RE: Dirty Birdy Build Thread
 

Blender?!? be careful.

RE: Dirty Birdy Build Thread
 

Deleted

RE: Dirty Birdy Build Thread
 

Allthegoodnames....,


You've put alot of work and $ into your project, it would be a shame to lose it for the lack of $0.25 in wood and 30 minutes of time. If you keep the wings as shown and your ply "shear web" (Which is now Spar AND shear web.) has the grain running parallel to the spar you may be Ok in positive G manuvers. However in Negative G manuvers I fear that will be the really weak point. Remember wood is 2 -3 times stronger in tension than compression, when the stress is with the grain.

Good Luck

Mark

RE: Dirty Birdy Build Thread
 

Jeff,
I just did want to show you this possibility, my way of doing this.
Success Cees

RE: Dirty Birdy Build Thread
 

I have flown many tail draggers and P 51's over the years, never had nose over issues with them. The DB was another animal all together, you really had to be lively on the stick to prevent nose over’s.

That being said my wheel location is very similar to yours. Although I made my mods on a foam wing, I too am skeptical as to your spar mods for the wheel well, I think Cees has a great compromise that will give you peace of mind, and it doesn't look like a lot of extra work to do the mod. Weight gain would be very minimal.

In the end its your bird and your choice, but I don't think it would be worth loosing it after all the hard work put into it.

RE: Dirty Birdy Build Thread
 

Well folks, even though I feel the ply doubler/sheer web would have been sufficient, I am forced to go with a design similar to Cees'.

When looking to install the wheel well, it turns out I had to whittle out the ply doubler/sheer web so the wheels will clear.

Since I have the retracts and wheel well/ spar situation figured out, I've started on the other wing panel. I apologize about the poor quality photos in this thread. I've had camera problems and have been using my cell phone.

I heard a rumor that my local flying field is installing a new, much larger alphalt runway. I heard it is going to be - get this - 100' by 1000' long!!!! Holy cow! I hope the rumor is true.

RE: Dirty Birdy Build Thread
 

Jeff,

Blenders, with a Dirty Birdy [sm=eek.gif] That's like asking your Granny to limbo dance - possible but a bit inappropriate.

Ray

RE: Dirty Birdy Build Thread
 

Gents,

All my advices are the results of a long development program including intensive testing of positive and negative lift G- forces and study of the results of impact of foreign objects.(FOD)


Do not forget,

The max generated G forces are not limited by the speed of you thumbs during normal flying maneuvers.

First it is the speed of the servo’s you use. For that the most negative moment for your wing can be that moment you receiver does switch over in the failsave mode in a case of a “black hole in the space of the electromagnetic waves” of your radio communication installation or other BLIP.

Second moment can be in case of a moment of separation and forced back with a big bang of the LE of the wing on the wing saddle in an uncontrolled inverted loop etc, when your wing is still mounted with rubber bands. (Classic Pattern)

Third in case of an mid air collision with a Haematopus ostralegus, or other orbjects. See example picture 1 and 2

So, do not forget, fly safe isn’t only a case of the choice of the maneuvers or the receiver, sometimes you have more profit of your good old analog elevator servo, mounting that wing yourself or even a “back up wing”, see picture three.

Cees


footnote just an example of a twin prop, but I know more!!: http://www.rcuniverse.com/forum/fb.asp?m=7284719

RE: Dirty Birdy Build Thread
 

You totally lost me, Cees.[:o] It's Oktoberfest, isn't it? :D

Guys, I built this plane to practice Classic Pattern as it as flown back in the 70's and 80's. I'm not a 3D pilot - I think hovering is lame.

RE: Dirty Birdy Build Thread
 

Roger on the lameness.

RE: Dirty Birdy Build Thread
 

No problem Jeff, when I did read this in an earlier post of you I already did expect that this could happen.




Cees

RE: Dirty Birdy Build Thread
 

Roger everything you have written on this post! (Cees' piece of wood is a good idea though. Not the fence post...)
Chris...

RE: Dirty Birdy Build Thread
 

stuntflyr,

Which piece of wood? Vertical?
How about your King Cobra

I decided to fill the aileron cove and use Robart hinges at about 20% of the aileron chord. Using a rounded aileron leading edge. Typical horn on the bottom with "a servo per wing" type set-up. I'm cleaning up all of the construction and with the dings and water spots about all sanded off it looks OK. I'll probably use Stix-It to make sure the cover stays stuck in case something creeps out of the wood's fibres.
Pix later, I promise.
Chris...


It did cost me 15 minutes to make that graphic for Jeff!
Cees

RE: Dirty Birdy Build Thread
 

Hi Guys.

I'm back from the Dr and spent some time on the DB. I have the second (left) wing panel mostly framed up including balsa blocks on the trailing edge for the Robart hinges - same thing I did to the Stab.
The next course of action is to duplicate the retract mounting plate and make a Cees style lower spar splint. ;)

I haven't purchased a retract servo yet and I'm out of glue. I'll be heading to the LHS tomorrow. Pictures coming soon.

RE: Dirty Birdy Build Thread
 

Jeff,

sorry for perhaps asking the obvious but are you not able to bend the struts forward to allow the wheels to retract into the area between the spar and the LE? I'm aware that the wing tapers in airfoil as you approach the LE but still, using the wheels shown, I'd imagine the gear would retract without exposure. Is that possible?

I ask because I essentially did this on a small HOB FW190 (which is of course designed in full scale for retract gear in that location) on which I installed retracts in the same way you are and had no problem getting the gear to tuck away without exposure near the wing LE.

If you can, you of course wouldn't have to deal with any spar issues.

David.

RE: Dirty Birdy Build Thread
 

David,

You did not ask me, but I want show you!

It is not a good idea to bend the leg in flight direction, the contra-rotation of the spring. This direction of bending is bad for the material, steel.

Read about titanium adviced by Berusty on page 2! I do not use exotic materials, I am a pianowire man!

http://www.rcuniverse.com/forum/fb.asp?m=7924505



WHEN YOU LOOK AT THE PICTURE, I DID DRAW THE SIDEVIEW UPSIDE DOWN!

When you can rotate the shaft of the wheel in the angle (a) then you can mount the mechanic also in that angle (a).
The gear will track with zero degrees "toe in/out" in this situation.

You can keep some room / space in the wing (light green), for safety reasons. so you system is more "fail safe" and you have not bend back the leg in the first time of a happy landing.
(There is a third posibility, rotate the mechanic also, look to the spitfire, in that plane the main gear is nearly retracted beside the tailwheel, the USA people can hide the mains somewhere under the ailerons, LOL!)


Cees