Blackbird fly... blackbird fly, Into the light of the dark black night. Twin 69mm EDF SR-71 Build/Project

[kilroy07]

Blackbird singing in the dead of night
Take these broken wings and learn to fly
All your life
You were only waiting for this moment to arise...

All my life I've LOVED the Blackbird. More than the Valkyrie, Viggen, the F-4, heck even more than the Eagle....
The SR is by far, my favorite jet.

I know I'm not alone, so why don't we have a foamboard version?!! (Time to change that!)
I have found 3 SR projects started here but none I see finished... Not sure why that is. But I am determined to find out.

My goals;

1. Design and build a "Scale" representation of the SR-71.

2. Make it easy to build so the average builder can complete one.

3. Have it's public debut at Flite Fest 2019.


Problems (opportunities) to overcome;

1. Inlet spikes (EDFs like airflow, find a way to represent the spikes without choking the motors.)

2. Rudders (Do we need them, if so, how to make them work while not have pushrods flapping about everywhere.)

3. Retracts (FINAL version will not only have retracts, but they will be tri-wheeled!) prototypes will likely be belly landers.

4. Control surfaces (I actually think I have this one worked out, proof is in the maiden.)

5. Easy hatch system for batteries. (I expect to use at least a pair of 2200 3S, and up to 4!)



As always, comments, guidance, support and CONSTRUCTIVE criticism welcome!

Won't you join me?



"Scale" will be a relative term, as it is already clear certain allowances have to be made for equipment and foamboard.

 

[kilroy07]

Reserved for plans

 

[kilroy07]

Reserved for flight video(s)

 

[kilroy07]

To be honest, I have no business starting another project...
I already have 4 solid projects on my workbench (with an ever expanding HoneyDo list.)

But I was working on the Swordfish 2 the other night when it occurred to me I might have an answer for the issue of building the nacelles on a SR. Pringles cans! Yup, turns out the EDFs I have on hand (69mm I purchased back in August during a Hitec Weekender Warehouse clearance sale Thanks Ben for the heads up) fit perfectly.

The last hurdle was my laser has needed a new tube for awhile now and I finally got that replaced/tuned this last weekend.

So I can cut plywood again (needed for the spar as you can see a test below.)





Once I checked the fit, this project was off and running.

 

[JTarmstr]

i have two of those EDF's...... hmmmm.... need a alpha builder? one problem, i don't eat pringles, so i dont have any nacelle parts, anything else that could be used?

 

[Grifflyer]

Nice looking project I hope you can finish it!! One thing the pringle thrust tube will work but you want the exhaust area to be around 75-85% FSA.

 

[kilroy07]

i don't eat pringles

They really are ideal! They are light, tough and (as I mentioned) the PERFECT size!
Once I get to where I have the whole thing laid out, remind me, I'll send you a couple cans with an Alpha build kit.

I had thought about rolled foamboard, but the problem was the attachment method to the wings...
Maybe it could be done, but I think the forces would be too strong for just foamboard.

With the cans, I have a sturdy connection with the plywood spar (really sturdy!)
I'll work on the full spar this week, I plan on incorporating cutouts for the retracts as well...

The one thing that's really got me stumped is getting to the batteries... I almost want the nose to come off... but then the nose gear gets in the way... I was thinking a box core to the fuselage, then foam board overlay (or, I hate to say... poster board) to get the blended effect.

 

[kilroy07]

Nice looking project I hope you can finish it!!

Thanks! And I'll finish it!... I'll finish it.

I really don't know why the others had problems... although, I just started the build... so maybe there are some bad tendencies in the design, but to be honest, I can't see them, I mean it's basically a huge delta... (almost a full wing with the chines....)

One thing the pringle thrust tube will work but you want the exhaust area to be around 75-85% FSA.

YUP, perfect for the tail cone!

I was "Testing" (read playing around with) the motors last night and being totally scientific here... they put out a BUTTLOAD of thrust...
With two of them I can't see how it won't "fly"... (just have to see how well...)

 

[JTarmstr]

I was "Testing" (read playing around with) the motors last night and being totally scientific here... they put out a BUTTLOAD of thrust...

I havent taken a video of my Viggen with one of those in it, but that thing has 90 grams nonessential weight (bomb drop and noseweight) and it still screams vertical, so much fun. It was suggested i re-learn to fly on a 3 channel airplane so i am doing that.

View attachment 119795

They really are ideal! They are light, tough and (as I mentioned) the PERFECT size!
Once I get to where I have the whole thing laid out, remind me, I'll send you a couple cans with an Alpha build kit.

I think maybe i will just find someone who does eat pringles and then requisition some of his trash

 

[Scooter The White Rabbit]

I havent taken a video of my Viggen with one of those in it, but that thing has 90 grams nonessential weight (bomb drop and noseweight) and it still screams vertical, so much fun. It was suggested i re-learn to fly on a 3 channel airplane so i am doing that.



I think maybe i will just find someone who does eat pringles and then requisition some of his trash

Pringles! Pringles here! Get your fresh empty Pringles cans here! Oh, and spike idea. Tight metal (Aluminum) window screen shaped into the cones, servo wire supports inside... paint black. Z-bends can be used to hook into the inlet of the tubes. This will also keep bug FOD down a ton. (FOD Foreign Object Damage).

 

[kilroy07]

Tight metal (Aluminum) window screen shaped into the cones

Oh, I LIKE THAT... A LOT!
Awesome idea!!
I plan on adding the bypass doors as cheater holes, but the screen "should" be transparent enough I hope!!

 

[Scooter The White Rabbit]

If you have to use the Bypass doors, I suggest screening them as well. Okay, I have this thing about... bug goo, dirt, grass, twigs inside my planes. Sue me. LOL That's what happens when your first ARF is shot down in your first night flight. eh... (shrugging, with smirk)

 

[kilroy07]

That's what happens when your first ARF is shot down in your first night flight.

June Bug?!

In all seriousness, I've taken a June Bug hit to the forehead on my Motorcycle at 70mph... Damn near knocked me out!

 

[Scooter The White Rabbit]

Georgia... on the back of a friends Hog... near that speed. Face shield. didn't help... much. Luckily I had a good grip on the seat side rails. My neck hurt for a week!
Shot down as in shotgun blast from a tower guard, Korea-1970's. Chem sticks on the plane spooked the guards. Was a pretty green spray lightshow for a few seconds.

 

[Scooter The White Rabbit]

Okay... thinking again. (Dangerous, but fun!) Pringle's cans gave me and idea. 69 mm EDF's fit in the end? Maybe as my spring project testing "Air Straightener" system for EDF's rear mounted... Pringle's cans for thrust tubes. Also looking to possibly fiddle with vectored thrust system. I think with some effort and two 5 gram servos I might be able to work up a light weight version with just enough throw to give some acrobatic assist to ships like the Viggen. Hmm. (Wheels creekin', smoke floating out ears... firing up the old gray matter boilers!)

 

[kilroy07]

Yes, I know.... It's been really quiet around here... But I have been working in the background.

I'm basically building her from the inside out... It's going to be "easy" to skin her later (easy being a relative term.)
So I've been focusing on what I think (hope) will be the hardest part, the main spar.

Here's the first mock up

LOTS of notes and... modifications....

Here is the second.

MUCH better, but still a couple minor tweaks.
And here it is with the gear extended (again, mock up... final version will have 3 mains as is proper for an SR.)


And oh, here it is in action...

Just MDF for now, I'll save my plywood for later.

It seems a bit smaller than I imagined... sometimes it's hard to see things 1:1 in CAD... But the nose isn't on her yet....

Need to fix servo geometry and a few other things... Then it's off to the battery bay.

 

[Scooter The White Rabbit]

Yes, I know.... It's been really quiet around here... But I have been working in the background.

I'm basically building her from the inside out... It's going to be "easy" to skin her later (easy being a relative term.)
So I've been focusing on what I think (hope) will be the hardest part, the main spar.

Here's the first mock up
View attachment 122043
LOTS of notes and... modifications....

Here is the second.
View attachment 122044
MUCH better, but still a couple minor tweaks.
And here it is with the gear extended (again, mock up... final version will have 3 mains as is proper for an SR.)
View attachment 122046

And oh, here it is in action...

Just MDF for now, I'll save my plywood for later.

It seems a bit smaller than I imagined... sometimes it's hard to see things 1:1 in CAD... But the nose isn't on her yet....

Need to fix servo geometry and a few other things... Then it's off to the battery bay.

Um... Somehow when you said seems smaller than you imagined... I'm wondering about the fuselage myself. Isn't the fuselage diameter the same as the nacelles? I'll have to look at my line drawings again.

 

[kilroy07]

This is the file I'm working off of... (Mainly because it had sections.)

And again, I'm going for an "easy Scale" appearance...

Maybe once I'm retired I'll spend 2+ years building a giant balsa one, but have too many other planes I haven't even built yet for that.

 

[kilroy07]

The "Drawing Board"...

 

[Mid7night]

Lookin' awesome mate! I really like your laser-cut center spar. Very smart. Can't wait to see it in Ohio! 2019 is DEFINITELY the Year of The Jet!