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I think Ben Harbor has done some thrust testing to optimize thrust tubes on some of his builds. He is the one to hit up for technical stuff like that I think.
SR-71 build using 64mm EDF or possibility of 70's
- Thread starter L Edge
- Start date
I think Ben Harbor has done some thrust testing to optimize thrust tubes on some of his builds. He is the one to hit up for technical stuff like that I think.
L Edge
Master member
What is his codename?
Grifflyer
WWII fanatic
Got your message, answered a lot there. Now I see you have gear; DON’T THROW IT!
Use the gear, let the takeoff be fast and gradual, don’t yank it into the sky. Climb shallow. Tip stalls on delta-wings are NASTY (don’t ask me how I know) 🤣
Also, I wouldn’t bother with differential thrust, even if you don’t have active rudder. This is the kind of plane that will need speed to fly anyway, and if you have that speed, the vertical tails should do a good enough job of keeping your nose straight.
Use the gear, let the takeoff be fast and gradual, don’t yank it into the sky. Climb shallow. Tip stalls on delta-wings are NASTY (don’t ask me how I know) 🤣
Also, I wouldn’t bother with differential thrust, even if you don’t have active rudder. This is the kind of plane that will need speed to fly anyway, and if you have that speed, the vertical tails should do a good enough job of keeping your nose straight.
L Edge
Master member
Hey, thanks for all those tips, and agree with you except that I just chose to add differential because of the possibility of saving a roll over or some other unforeseen position on the flight.
My main concern is all that area on the long nose. Afraid of airflow getting (over/under ) the nose and driving it one way or the other. Had that problem when I designed the X-47B due to sensative pitch problem(no long nose).
Last edited:
L Edge
Master member
What to do?
Mid7night recommended a long takeoff and gradual. Found out the road leading in to the club's field has deep ruts and will most likely be that way until spring when graded. The paved runway is about 200 ft long. Wheels are too small. So that's out for now.
Went to an business site that was empty and decided to see if the SR-71 would lift off the ground and find out at what distance. Made 5 dry runs(each one longer) and nose just came off ground at around 250 ft!!!! Ain't gonna work at field either.
So, back to, "WHAT TO DO?", and do I release it moving forward with fingers at CG? about a foot off the ground? It went before so---
Added a good clip of up elevator trim and went for it. It started to climb, dropped power and it leveled off and slowly accelerated and I tried slight ailerons and the differential and it worked. Cut a couple notches of power and it settled back down. Max height was about 2 feet and now I know what to do. Flight and rollout covered about 400 feet.
As of now, the SR-71 is sitting near my boneyard in the cellar till the spring. Like the XB-70, it is going to take a large area to get going, making large shallow turns and a good speed on approach to complete landing for the maiden flight.
Reviewing my problem, the reason why it doesn't get off was the nose is not inclined enough(learned that working with movable canards and a F-22). Not bothering with that until I see what happens.
Score:
SR-71 ----------------one
Ground Gods---- Zero
Mid7night recommended a long takeoff and gradual. Found out the road leading in to the club's field has deep ruts and will most likely be that way until spring when graded. The paved runway is about 200 ft long. Wheels are too small. So that's out for now.
Went to an business site that was empty and decided to see if the SR-71 would lift off the ground and find out at what distance. Made 5 dry runs(each one longer) and nose just came off ground at around 250 ft!!!! Ain't gonna work at field either.
So, back to, "WHAT TO DO?", and do I release it moving forward with fingers at CG? about a foot off the ground? It went before so---
Added a good clip of up elevator trim and went for it. It started to climb, dropped power and it leveled off and slowly accelerated and I tried slight ailerons and the differential and it worked. Cut a couple notches of power and it settled back down. Max height was about 2 feet and now I know what to do. Flight and rollout covered about 400 feet.
As of now, the SR-71 is sitting near my boneyard in the cellar till the spring. Like the XB-70, it is going to take a large area to get going, making large shallow turns and a good speed on approach to complete landing for the maiden flight.
Reviewing my problem, the reason why it doesn't get off was the nose is not inclined enough(learned that working with movable canards and a F-22). Not bothering with that until I see what happens.
Score:
SR-71 ----------------one
Ground Gods---- Zero
L Edge
Master member
No. I have explored EDF's for the past 8 years and this low release procedure (see thread response number 38 for steps) to find the proper CG position(using high winds) and to do maiden launch(no wind) works for me. Point is never launch with a high angle or you will end up with major damage due to height.
Have you explored TV nozzles by any chance?
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