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SR-71 build using 64mm EDF or possibility of 70's

L Edge

Well-known member
#1
This is going to be an interesting project. I decided to find out if I build with 64's and it doesn't work, insert 70's sometime in the future. Some of the other problems are the long fuse it has, address the negative thrust line, long ducting, and I am going to move the EDF's so in the future you can add the nose cone(propellar cone?) and put cheater holes in the bottom to make it looks scale.

Goals:
1) Build super light to see if 64's will fly it.( How about Mach .0001)
2) Address wing and nose stress(especially battery location) problems.
3) Getting angles in 3d correct so there is very little twist, warp or whatever.
4) Use my 64 combo(already built, tore apart an old model) and TV to cover a bunch of issues.
5) Find out if short ducting changes has any effect.

History:
Designing past models of exploring ducting, "thrusters", using 2D thrust vectoring nozzles, leading edge devices have yielded tons of info that I am going to use. Will it work?, don't know, but I am going to try.

One- Decided to scale my SR-71 and move EDF's aft from CG (present is area of the neck) so it can be move the battery closer to reduce stresses on neck.
Two- Thrust angles are going to be very important for this plane so I added the TV gimbal in which I am going to tape and explore what is the best angle to use if needed.
When I built my Viggen in the user group, I used the TV nozzle to trim the nose down condition from the canard's +10 degrees to an end product of no angle of incedence to make it fly enen faster. Good way to handle the SR-71. Does it need 2-3 degrees down according to drawings?
Three- When I saw (kilroys07) pringle cans stacked, wow the length for 70's, does it loose power and how much? So I decided that my EDF,thrust tube,and gimbal setup will be 13" long.
This gives me 2 choices-- I now can add the inlet length (6" to cover the front, nose cone and cheater holes) after it flies to see if it looses too much power or now install a pair of 70's by enlarge slot and install new circular tube. No need to build another.
Four- like all experimental planes, it's nickname is bluebird due to the FFF.

I wish to thank kilroy07 for the scale model of the SR-71 which I picked off the ratio and angles and the pringle can picture that got me to move the position of the EDF's.

View attachment 149691

Here is the front and back end on my 13" setup in which I now go to scale it. Being old school, will have to do this project on paper so the size and scale looks good.

IMG_0320.JPG
 
Last edited:

PsyBorg

Wake up! Time to fly!
#6
wow that thing has some get up n go. It just jumped effortlessly into the sky. that color scheme rocks too. VERY visible with the silver and the black out line.

#FTTurbinesmakeithappen
 

L Edge

Well-known member
#8
After 3 rounds of trying to scale it, I finally got something on paper that will work properly I hope. Above is the set of nozzles showing the 64EDF and the TV gimbal to get it scaled. If there are any angle changes due to being nose heavy or tail heavy, I will untape the gimbal and retrim it out.

So cut out some parts to see how it will assemble.

IMG_0319.JPG

First step is to strengthen the fuse, EDF's and outer wing by using a carbon rod where I groved it, hot glued it to the fuse.

IMG_0323.JPG

Next installed elevons where they are large(roll should be okay, pitch with long nose don't know) . By the way I use Scotch "storage" tape (not packaging tape) for upper and lower surfaces and still have models 6-7 years old and the hinges are still good.
 

L Edge

Well-known member
#9
The hardest part of this project is trying to get the fuse, EDF's, rudders, squared up and the right angles. I must have measured and re-measured and adjusted numerous times before I hot glued the parts. Get it wrong and anything that is twisted or off will cause problems.

To get the strength to the outer wing, I needed to run the carbon rod thru the thrust nozzle and grooved the outer wing to about 1/8" from the end. This is not the first time I have done this. The most I have interfered with the airflow is place two thrusters and a carbon rod behind the fan and didn't lose much power since the airflows are not that fast.

Here it is so that the EDF's are parallel to the fuse, zero degrees on the thrust line .

But wait, they are in the wrong position. It is located 5 1/2" back. The total distance scaled is 18 1/2" to have after the fan. My gut feeling is that is quite a distance and maybe loose too much power.

I have done this for 3 good reasons.
1) Have move the gimbal and fan back away from the CG so it should balance the battery closer and possibly improve the pitch.
2) Have made dummy inlets (5+ inches long) to bring it to look like the scale model and guess what, you could add a dummy inlet cone(chokes the airflow) and add cheater holes under the bottom.
3) Want to see if there is any reasonable difference in EDF power with no dummy inlet and a 5+ dummy inlet.


IMG_0324(1).JPG
 

kilroy07

Well-known member
#12
This is going to be an interesting project. I decided to find out if I build with 64's and it doesn't work, insert 70's sometime in the future. Some of the other problems are the long fuse it has, address the negative thrust line, long ducting, and I am going to move the EDF's so in the future you can add the nose cone(propellar cone?) and put cheater holes in the bottom to make it looks scale.

Goals:
1) Build super light to see if 64's will fly it.( How about Mach .0001)
2) Address wing and nose stress(especially battery location) problems.
3) Getting angles in 3d correct so there is very little twist, warp or whatever.
4) Use my 64 combo(already built, tore apart an old model) and TV to cover a bunch of issues.
5) Find out if short ducting changes has any effect.

History:
Designing past models of exploring ducting, "thrusters", using 2D thrust vectoring nozzles, leading edge devices have yielded tons of info that I am going to use. Will it work?, don't know, but I am going to try.

One- Decided to scale my SR-71 and move EDF's aft from CG (present is area of the neck) so it can be move the battery closer to reduce stresses on neck.
Two- Thrust angles are going to be very important for this plane so I added the TV gimbal in which I am going to tape and explore what is the best angle to use if needed.
When I built my Viggen in the user group, I used the TV nozzle to trim the nose down condition from the canard's +10 degrees to an end product of no angle of incedence to make it fly enen faster. Good way to handle the SR-71. Does it need 2-3 degrees down according to drawings?
Three- When I saw (kilroys07) pringle cans stacked, wow the length for 70's, does it loose power and how much? So I decided that my EDF,thrust tube,and gimbal setup will be 13" long.
This gives me 2 choices-- I now can add the inlet length (6" to cover the front, nose cone and cheater holes) after it flies to see if it looses too much power or now install a pair of 70's by enlarge slot and install new circular tube. No need to build another.
Four- like all experimental planes, it's nickname is bluebird due to the FFF.

I wish to thank kilroy07 for the scale model of the SR-71 which I picked off the ratio and angles and the pringle can picture that got me to move the position of the EDF's.

View attachment 149691

Here is the front and back end on my 13" setup in which I now go to scale it. Being old school, will have to do this project on paper so the size and scale looks good.

View attachment 149801
This is AWESOME for so long this beautiful bird was ignored and now we have three separate builds going!! 😍

As for collaboration, your welcome! I too struggled with where to place EDFs, thrust angles inlet cones. Etc.

I know you mentioned old school paper, but if my CAD files would help just let me know. I use MicroStation, but can export to just about anything.
If you have acces to a 3D printer I can pass along my STLs for the inlets and exhaust cones as well.

Great work so far! 👍
Good luck and I’ll be watching!
 

L Edge

Well-known member
#15
This is AWESOME for so long this beautiful bird was ignored and now we have three separate builds going!! 😍

As for collaboration, your welcome! I too struggled with where to place EDFs, thrust angles inlet cones. Etc.

I know you mentioned old school paper, but if my CAD files would help just let me know. I use MicroStation, but can export to just about anything.
If you have acces to a 3D printer I can pass along my STLs for the inlets and exhaust cones as well.

Great work so far! 👍
Good luck and I’ll be watching!
Yeah, also wonder if the negitive thrust line has to deal with low speeds or are we talking about Mach speed since it takes miles to make a turn in the upper atmoshere.
Hope to pass on what I learn if this beast(wonder more if 64 will make it) actually flies. Ducting, +/- thrusting, stress on long nose, battery location, and if I move up to landing gear, what happens. Could be a total failure.

The one that has kicked my butt over the years is VTOL. Failure is an option, but from that I learned how to STOL an EDF F-22 and best of all did my X-47B making it possible to have EDF jet without any rudders or vertical stabs just using a gimballed thrust vectoring unit and 2 servos. No gyro was used. Tried air brakes and result is horrible pitch/yaw problems you can't control and end up with a crash.

Can your 3D printer do a 2 axis TV unit? They are very scarce now and very costly. Yet, offer a different way to fly and in many cases, save me from many crashes due to being able to STOL it in and do only minor damages.

Have used cheater holes(slotted 45 inward on bottom of model) before in a store bought model and made a big difference in thrust. One thing I will pass on to you is do not reduce exit area of nozzle. If interested, will explain why.
 

kilroy07

Well-known member
#16
Always interested!

Currently I had my exhaust down to maybe 85 percent (Ben H. Pretty much said I was probably choking the edf and should go no more than 90. One thing about Pringle’s cans is they have that nice slick foil lining.

I have to redesign my exhaust anyway, I might make them 100% (no taper)

I plan making cheater holes where the blow by doors/vents are. 😉
 

L Edge

Well-known member
#19
IMG_0329.JPG

This is the underside showing the carbon rod going thru the ducting then sitting in a groove made in the outer wing. After insuring everything is zeroed out and no angle of incidence I then glued the rod and both sides of the each nozzle so everthing is now fairly stiff.

My main concern now is the long nose section that is going to be cantelever that is longer than this part of the fuse when you join it. So to prevent twist I routered out a groove and used a carbon strip(vertical) to prevent rotation. Will address the rest of the problem when I make the nose.

Now cut out the rudders and installed parallel and tipped in. Finally starting to take shape.

IMG_0325(1).JPG

That's it for today.
 

L Edge

Well-known member
#20
Today ended up putting the electronics on the ship.
IMG_0335.JPG

IMG_0336.JPG

One of the concerns was to insure there the control surfaces has no slop or bending of the wire, so I ended up using threaded(can change lengths) heli rods where the control surfaces have been glued and have threaded screws.

Made the upright nose section to see what it would look like and it's strength. Hot glued it together.

IMG_0334.JPG

Last part to make is the extra ducting to later insert if this puppy flies. Using free folding foam allows you to heat up and roll the foam to get that perfect circle. I accomplished this by using our hot water heating boiler whose temp is 180 degrees exiting a 1 1/4 " copper pipe. All you do is start rolling it and move down the length slowly. Add storae tape and your done after proper sizing.

IMG_0330.JPG