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

kilroy07

Legendary member
Alright time for an update;
Simply... Life.
Yup, life has gotten in the way. Specifically my job has had me on the road for WAY too much lately.
But (and let me be clear) This project is in NO way abandoned or forgotten.
In fact it is the single thing I plan on getting wrapped up by the end of the year (and believe me, that's taking priority over a LOT of other projects I have.) I'll be home next week (24-30 Nov.) and that will be the week #2 gets built. then I'm not back home till the last week in Dec...
So I think I have enough time (crosses fingers) to get this bird done and plans out by the end of the year!!! (That's the plan currently.)
I've been promised 3 weeks at home in January, but that doesn't help my goal of getting this bird done by the end of the year...

So sitrep; Good news (everyone);
New EDFs are in
Bad news;
New EDFs have motor leads coming out in a place that will not work on the SR.
Good news;
I have modified both EDFs and they are ready to go AND still fit a pringles can.

Good news;
New ESCs are in
Bad news;
I waterproofed them and now they need shrinkwrap.
Good news;
You can buy shrinkwrap on aliexpress really cheap.
Bad news
You have to wait a month for said shrinkwrap to arrive AND apparently the number (diameter) you order it by is NOT the starting diameter, but the finished shrunk diameter.... I seriously have some shrinkwrap now that you could slide on your fore arm!!! (No idea what I'm gonna do with this stuff...) :rolleyes:
Good news;
New (smaller) shrinkwrap has been ordered.

Good news;
Pretty much all the CAD work is done (I think...) so next week I'll be able to start slicing into foam right away.

So that's it everyone, mission is still a go.
I just need some time in my workshop and we'll get some progress done!
 

kilroy07

Legendary member
Hello everyone-

Been a tough year...
FF21 has restored my faith in humanity, AND given me the motivation to revisit the SR and "finally" get this project wrapped up.
A shout out to @FoamyDM and @localfiend thanks Brothers!!

I'll be honest, the foam version "might" take a backseat to a full on 3D printed one BUT I do plan on reworking the design to shed some weight.

So, August is the month/target for the re-maiden.
Weekly updates will be coming.
 

kilroy07

Legendary member
Wouldn't it be easier to try the foam and get it to work before attacking the 3D version?
I wish! LOL

The plan is to use ideas along the FT master series kits, use bulkheads/formers and a molded skin.
So, there isn't much from the body (V1.0) I will be able to use. I think the outboard wings and such might still be good.
I really like some parts of my design and printing things like the nozzles out in LW-PLA has given me renewed hope she will one day fly.

That said, a trick LocalFiend gave me at FF might just take the 3D version to the prototype stage within a week (I "might" have several 3D models of the SR plus what I've done for the foam version to pull from). And there is probably several days (if not a week) of printing ahead.
At first I will go with a 350x350 printing area, but (if it flies) I might look into cutting it into smaller sections for smaller printers (no promises though.)

I just checked out your build (awesome!), I found it fascinating we came up with similar locations for the fans. Mine were 120mm from the inlet face (4.72") For the second version, my inlets are going to be thin vanes rather than a cone (think profile planes).
I was also thinking about "cheater holes" fortunately, the blow by doors on the SR will keep that scale looking! LOL

Thanks for the feedback/interest, I need someone to keep me on point!
 

FoamyDM

Building Fool-Flying Noob
Moderator
Hello everyone-

Been a tough year...
FF21 has restored my faith in humanity, AND given me the motivation to revisit the SR and "finally" get this project wrapped up.
A shout out to @FoamyDM and @localfiend thanks Brothers!!

I'll be honest, the foam version "might" take a backseat to a full on 3D printed one BUT I do plan on reworking the design to shed some weight.

So, August is the month/target for the re-maiden.
Weekly updates will be coming.
AWESOME!!! I have eyes on this and a pom-pom for this project. if you need a beta builder, I have foam!
 

L Edge

Master member
I went back to my build site and found my successfull flight video will not come up. Let me know if you would like to see it, PM me.
 

kilroy07

Legendary member
Okay, weekly promised update. :cool:

Lots to report.

The trick @localfiend shared with me DOES indeed work with my CAD software (MicroStation)!!
Thanks again!!

I am struggling on how exactly to break this puppy into manageable pieces though... My first thought (seen in the bottom left corner of the screenshot) is to take my existing design for the engine nacelles and incorporate it into a 3D printed body. This would get V.2 in the air the soonest as I can reuse my existing design for many of the sub assemblies. it might not be the most realistic approach, but I think it will be the best bang for the buck (time invested.) I'm looking at the true scale approach and really think the ducted fan just won't get the airflow it needs.

I also have my 3D printer tuned (re-tuned) for LW-PLA (lost my prior setting in an update (thanks Cura!!) :mad:
It's currently printing out the Plane Print Eagle (a great design BTW!)
And have 2 rolls of Black on-hand for this project.

In other good news, If we go with the nacelles as above, I think the body will fit on common 220x200mm build platforms (kind of the standard for 3D printers.) In version 2.1 I might redo the engine pod and get rid of the pringles can (but I admit, I find it a bit of the design's charm. LOL)

Until next week.
SR-update_1.jpg
 

L Edge

Master member
Suggest that you run a carbon tubing thru the body thru the exhaust tube to the outer wings to prevent fluttering and give it strength. Go look at my EDF thrust vectoring, thruster project and it will not disturb the airflow to loose thrust. Solved that with a water U-tube and pitot tube. That is a lot of blockage that I had on the F-22 EDF trying to hover.
 

L Edge

Master member
Played around with nose cone for a SR-71.

nase cone 1.JPG


nose cone side.jpg


Glued nose cone to frame.
From back, figured out area blocked.
Added on 3" overlapment of blue foam in front of fan blades. (taped it)
With tac, measured full rpm's with charged battery. Recharged battery to same voltage.
Cut out cheater holes on lower surface of foam to equal area + 2 sq in(gut instinct).
Inserted nose cone frame into foam in front of fan and hot glued.
Ran, tac it and had only a drop of about 350 RPM. Did a hand chuck and still it blasted off. Used rudder(differential thrust) to correct and landed it. No way to tell losses.
 

kilroy07

Legendary member
Played around with nose cone for a SR-71.
<Snip>
Ran, tac it and had only a drop of about 350 RPM. Did a hand chuck and still it blasted off. Used rudder(differential thrust) to correct and landed it. No way to tell losses.

Awesome info, Thanks!
I've played with a couple designs and settled (at least for V.2) for the "profile" nozzle (Green in the image.)
On V.2 I planned on modeling cheater holes where the bypass doors are.
(I'm leaning more and more towards a fully 3D printed nacelle)

I have an arrow shaft going down the middle and yea, how to brace it laterally through the nacelle is the $1M question at this point.
On V.1 I had a pretty stout spar made of plywood (well, the prototype was MDF, no wonder she was overweight) which had the option for retracts and it worked great (very little flex) but it was heavy... too heavy. (I tend to over-engineer stuff...)

V.2 might use a mix of carbon, plywood and/or regular PLA.
SR-update_2.jpg
IMG_1512.JPG
 

L Edge

Master member
Awesome info, Thanks!
I've played with a couple designs and settled (at least for V.2) for the "profile" nozzle (Green in the image.)
On V.2 I planned on modeling cheater holes where the bypass doors are.
(I'm leaning more and more towards a fully 3D printed nacelle)

I have an arrow shaft going down the middle and yea, how to brace it laterally through the nacelle is the $1M question at this point.
On V.1 I had a pretty stout spar made of plywood (well, the prototype was MDF, no wonder she was overweight) which had the option for retracts and it worked great (very little flex) but it was heavy... too heavy. (I tend to over-engineer stuff...)

V.2 might use a mix of carbon, plywood and/or regular PLA.
View attachment 204494 View attachment 204495

?
 

kilroy07

Legendary member
Okay so um.... has it really been 4 YEARS?!!!! :oops::poop:

I was at Flite Fest this year, and a young gentleman came up to me and asked "Hey, are you that Kilroy guy who did the SR-71 on the forums?"
I replied "Yea..." "So... you done anything on it in awhile?..." He asks... (Oh, the shame!) :LOL:

So, if you are that young man... Please PM (Personal Message) me, I have something for you for taking the trouble to give me the kick in the pants I needed to get back on track with this!

Hopefully... I will have something for everyone else after this weekend... It's not the "perfect" answer, but more of a quick-build (yes, I will share the plans).
 

kilroy07

Legendary member
Good to see you back in the saddle.
Yea, this project really has suffered from the old adage "Perfection is the enemy of completion."

This is my second most favorite aircraft and I really wanted to do it justice. So I fell into the trap of over engineering, too many barbels and too perfect.

Now I have three ideas, the first (and probably what will come out of this weekend is to use a diamond (box) fuselage for something that honors the old FT tradition (That will be the FT-71) then take some inspiration from John Overstreet's designs and make something closer to my original vision (this may or maynot happen, see #3) and finally my third idea is after speaking with Localfiend... Revise the entire design to be 3D printed.... (an idea which the perfectionist in me loves!)

So, thanks for the encouragement everyone... now, let's get'er done!
 

mastermalpass

Elite member
Well hey, I dunno how I missed this thread, but I'm glad I've found it before it's over! Plus it makes me feel less guilty about my stagnant Albatross DVa thread (I'm sure I can get a prototype flying before January). 😂

I got high hopes for the return of this beast!