Dirty Birdy 60 Build
 

Hi all,

I'd like to post pics from this Dirty Birdy 60 build. Started with the wing tonight. I want to push this through quickly. Doing a build thread always gives me motivation to keep up the progress.

It is an all-wood Blue Jay kit that I got from the LHS. I was so surprised that they had it that I bought it on the spot. They mostly have ARFs at the LHS.

I'm going with fixed gear, nosewheel.

I'll be using a brand new OS .61 FX that I bought as a spare for the Curare. I've seen the other threads discussing the nose heavy issues so I'll do a center tank and aft servos.

I have every intention to use this as a contest bird and compete in novice this year. I hope it works out. I'm ready to burn some vacation and I bought a slide-in camper for my truck. Now all I have to do is follow through.

Mitch

RE: Dirty Birdy 60 Build
 

Is that a commercial wing jig, or did you build it yourself. I am in the market for a jig for when I start work on my Utter Kaos.

thanks

John

RE: Dirty Birdy 60 Build
 

The Bluejay kit comes with laser cut ribs with the 1/4 inch jig holes.

I just bought some poplar scant wood at the home improvement store and some 1/4 inch steel rod at the tool store. You have to be very careful to drill the holes accurately in the wood endplates. Measure it twice and rework if it's not perfect.

I had to polish the steel with some sandpaper and relieve the holes in the ribs with a 1/4 inch drill to get everything to cooperate.

You can see that I've braced the center of the steel rods so they won't sag.

RE: Dirty Birdy 60 Build
 

Please post weights as you biuld, if possible.

Thanks,
Jim

RE: Dirty Birdy 60 Build
 

Will do Jim. Remind me if I forget :)

RE: Dirty Birdy 60 Build
 

This wing design seems to have no shear webs between the spar caps!!! Can that be true?

RE: Dirty Birdy 60 Build
 

Hey Mitch,

Good to see you doing another build!

Joe seemed to omit shear webs on a few of his designs. Instead, he favored very large spars such as 3/8" square or perhaps even larger on some models. Not quite the same but nonetheless. I just redrew Joe's DB40 and for good measure decided to add webs to the wing. You might want to consider doing the same with your wing. I left the last three bays of a 10 rib panel open.

David

RE: Dirty Birdy 60 Build
 

Hey David,

Great input! I'm looking forward to your support of this build.

I don't think that the engineer in me will let me finish this wing without shear webs. I'm trying to decide where I can make up the weight. I think the trailing edge sheeting can get narrower.

Here's a pic of how it looks now:

RE: Dirty Birdy 60 Build
 

and just for fun, here's a pic of my rig:

RE: Dirty Birdy 60 Build
 

Mitch,
I have a Bridi DB kit that I want to build, eventually. I have been thinking about making the wing fully sheeted and wondered about the weight of the open bay version.

Jim

RE: Dirty Birdy 60 Build
 

If you do sheer webs, they will be about cg and should not have any effect.
You are talking grams in weight if you use 1/16" wood.

RE: Dirty Birdy 60 Build
 

good point

RE: Dirty Birdy 60 Build
 

Please take lots of photos Mitch. Thanks for the thread.

Mike

RE: Dirty Birdy 60 Build
 

Just a tip. If those of you wanting to build a wing jig try to buy "drill rod". Very straight and smooth finish when you buy it. Excellent material for true built wings.

RE: Dirty Birdy 60 Build
 

You can use 1/64" or 1/32" ply for shear webs. Almost no weight and still strong enough to do the job. Can cut with scissors, too. If you think it's not strong enough try bending ply on edge!

RE: Dirty Birdy 60 Build
 

jmb52760,

Being you have a Bluejay kit, the canopy is totally wrong for the DB60. While it looks somewhat like it should, when compared to the correctly shaped canopy you'll see major differences. Very shortly, there will be DB40 and DB60 canopies available. Molds are being made from original canopies and they will be available from parkflyerplastics.com. If you (or anybody else) is interested, I'll advise when they are available. I'm not associated with the vendor, just a very satisfied customer. Check out the below link and you'll see what I mean.

More info and Pics here.
http://www.rcgroups.com/forums/showp...8&postcount=14



FB

RE: Dirty Birdy 60 Build
 

Probably going to stay home and build today. While the temperature is great outside, the winds are forecast to be 30 gusting to 39.

Shaving and sanding everything to match the rib contours:

RE: Dirty Birdy 60 Build
 

Yeah, I thought it looked funny. I'd prefer a fiberglass canopy. Are the parkflyer canopies going to be clear or fiberglass?

Mike,

Very good suggestions. I had to do extra work on these steel rods to get them smooth and straight.

Any idea on the weight difference between 1/16th balsa and 1/32 ply? The balsa is certainly cheaper.

RE: Dirty Birdy 60 Build
 

Properly (tightly) fitted 1/16 or 3/32 "C" grain balsa, grain vertical, is fine for sheer webbing on a wing of this size. Sheer webbing between the trailing edge sheet pieces, though tedious to fit, are good, too.

Best if the webbing for the main spars is tightly fitted between the spars, but flat against the rear face of the spars is much easier to install, if not quite as effective.

Jim

RE: Dirty Birdy 60 Build
 

Mitch,

The weight issue of 1/64" ply vs medium 1/16 balsa has been looked at several times in the context of foam core skins. In Europe, the veneer HW skins have been adopted for some time. On this side, back in the day, some used veneer to provide additional stiffness and a somewhat easier finishing surface for paint. However, I believe there is little doubt today that light 1/16" balsa results in an overall lighter wing, reason why it is used so pervasively.

With that in mind, I'd say that using 1/16" balsa shear webs is a lighter path. But, given the amount of material, I don't really think either type of shear webs would affect the overall weight of the wing considerably. My preference for balsa (even 3/32" balsa) is due to the lower cost, ease of fitting (if scratching) but mostly because the properties of the wood are not paramount provided the grain is used in the correct direction (which applies to balsa but not ply of course). The structural stiffness of the D-tube comes from the interlocking of the three components: spars, ribs and webs. If the webs are not bonded tightly to the ribs but just to the spars, the overall stiffness of the wing is considerably less.

Other methods such as using a truss zig-zag bracing approach has been used and according to some reports is lighter yet and even stiffer. I don't have any empirical figures to confirm or deny this but I have built a couple of wings like that and can say that it is very effective. 1/8" x 1/4" stiff stock can be used and applied with the 1/4" width against the spars and ribs.

I guess I exhausted that one, didn't I? :eek:

RE: Dirty Birdy 60 Build
 

Nice one Jim. I'd venture that mating the top and bottom TE sheeting by "end bonding" the webs would allow classic designs to use considerably less wide TE sheeting probably also lightening the wing slightly (perhaps the glue would cancel any weight savings). But the coupled D-tube and "V-tube" would be interesting to build and very stiff.

Definitely something I'll try and relatively easy to do on a wing with a straight TE and constant inter-rib spacing.

David

RE: Dirty Birdy 60 Build
 

Mike, the canopy will be clear, PFP does outstanding work, some of the best pulls I've ever seen and they use .030 PETG.

FB

RE: Dirty Birdy 60 Build
 

Sorry for the confusion but my name is Mitch. I was addressing that next comment to Mike.

I'll definitely order one of the canopies when they are available.

Top skins applied:

The upper surface of the leading edge skin was whetted with warm water to help it take the shape. LE skin goes to half the width of the spar per the plans and instructions so I marked a centerline on the spar cap.

I like the idea of a web between the TE sheeting. Would it be just between the spar caps? That would certainly be easier. I'm sure it improves the stiffness in that important area.

RE: Dirty Birdy 60 Build
 

Adding shear webbing won't hurt but this wing doesn't need them. It's built plenty strong.

By the way, if you haven't seen my notes on the Dirty Birdy instructions, take a look here http://www.rcuniverse.com/forum/m_9520759/tm.htm

Dave

RE: Dirty Birdy 60 Build
 

That's really good stuff Dave! Now I remember seeing this thread. For some reason it didn't show up in a search that I did before I started (or maybe it was way down on the list and I didn't get to it). It's a good thing that I didn't get too far with the build before you showed up. I'll follow as many of these tips as I can.

I'm obviously not following the sequence as I've started the wing before the fuse. I'll suspend wing progress and move on to the fuse when I need it to make further progress.

The right wing is out of the jig and the left one has been started. Here are the landing gear doublers going in: