New Products Flash Sale
Thread Tools
Old Aug 25, 2014, 06:11 AM
23Chaos23 is offline
Find More Posts by 23Chaos23
Registered User
Australia, QLD, Shoal Point
Joined Apr 2014
67 Posts
Build Log
SR-71 90mm edf

I origanaly started this build project as a balsa scratch build in the balsa builders thread SR-71 90mm edf , but quickly realized the cost of balsa and moved to 3D printing it instead.

So welcome the the first part of a journey that will take us to the end of 2015 and a first in RC 3D printed aircraft.

Enjoy the video
23Chaos23 is offline Find More Posts by 23Chaos23
Reply With Quote
Sign up now
to remove ads between posts
Old Aug 25, 2014, 07:47 AM
23Chaos23 is offline
Find More Posts by 23Chaos23
Registered User
Australia, QLD, Shoal Point
Joined Apr 2014
67 Posts
working away at the engine nacelle got some renders for you all





this one shows the different components
23Chaos23 is offline Find More Posts by 23Chaos23
Reply With Quote
Old Aug 25, 2014, 09:17 AM
CoolerByTheLake is offline
Find More Posts by CoolerByTheLake
Do it Right, the first time!
CoolerByTheLake's Avatar
United States, MN, Hermantown
Joined Dec 2008
6,550 Posts
What is the planned lenght and WS of this project?? Target weight??
CoolerByTheLake is offline Find More Posts by CoolerByTheLake
Reply With Quote
Old Aug 25, 2014, 10:19 AM
23Chaos23 is offline
Find More Posts by 23Chaos23
Registered User
Australia, QLD, Shoal Point
Joined Apr 2014
67 Posts
Quote:
Originally Posted by CoolerByTheLake View Post
What is the planned lenght and WS of this project?? Target weight??
2.4m L 1.2m W 0.4m H around 10KG hopefully under, i go over it in the video. im scaling it around the EDF units so the exact dimensions are still flexible plus or minus 10cm
23Chaos23 is offline Find More Posts by 23Chaos23
Last edited by 23Chaos23; Aug 25, 2014 at 10:26 AM.
Reply With Quote
Old Aug 25, 2014, 10:45 AM
CoolerByTheLake is offline
Find More Posts by CoolerByTheLake
Do it Right, the first time!
CoolerByTheLake's Avatar
United States, MN, Hermantown
Joined Dec 2008
6,550 Posts
Specifications (SR-71A)

General characteristics

Crew: 2 (Pilot and Reconnaissance Systems Officer)
Payload: 3,500 lb (1,600 kg) of sensors
Length: 107 ft 5 in (32.74 m)
Wingspan: 55 ft 7 in (16.94 m)
Height: 18 ft 6 in (5.64 m)
Wing area: 1,800 ft2 (170 m2

OK, that said, your projected length is 94.5", and WS would be 48.57" = 1/13.73 scale --give or take.

What are your ideas/plans for internal structure??
CoolerByTheLake is offline Find More Posts by CoolerByTheLake
Reply With Quote
Old Aug 25, 2014, 11:26 AM
23Chaos23 is offline
Find More Posts by 23Chaos23
Registered User
Australia, QLD, Shoal Point
Joined Apr 2014
67 Posts
Quote:
Originally Posted by CoolerByTheLake View Post
Specifications (SR-71A)

General characteristics

Crew: 2 (Pilot and Reconnaissance Systems Officer)
Payload: 3,500 lb (1,600 kg) of sensors
Length: 107 ft 5 in (32.74 m)
Wingspan: 55 ft 7 in (16.94 m)
Height: 18 ft 6 in (5.64 m)
Wing area: 1,800 ft2 (170 m2

OK, that said, your projected length is 94.5", and WS would be 48.57" = 1/13.73 scale --give or take.

What are your ideas/plans for internal structure??
well most of the design is alread roughed out in my head, just started modeling the sub structure in maya 3 days ago. ill be doing a weekly video showing my progress and to talk about the substructure and how it will be printed and put together. built in 4 main parts nose fuse, center body fuse, and the outer wings and engine nacelles. RC gear and FC systems in the nose fuse, batteries and ESC units in the center fuse. the hardest part is finding places to squeeze in the servos for the vert stabs and outer elevons, but i think i have it worked out.

if its to tight a squeeze ill go ahead and round it down to 1/13 scale.
23Chaos23 is offline Find More Posts by 23Chaos23
Reply With Quote
Old Aug 25, 2014, 11:39 AM
23Chaos23 is offline
Find More Posts by 23Chaos23
Registered User
Australia, QLD, Shoal Point
Joined Apr 2014
67 Posts
for anyone interested, i have gone as far as to select an actual SR-71 to base mine off of,
SR-71A#61-7976 (17976)
23Chaos23 is offline Find More Posts by 23Chaos23
Reply With Quote
Old Aug 25, 2014, 12:19 PM
Eddie P is offline
Find More Posts by Eddie P
Official Boat Bum
Eddie P's Avatar
United States, NV, Reno
Joined Mar 2000
7,875 Posts
Awesome stuff! Look forward to your work here.
Eddie P is offline Find More Posts by Eddie P
Reply With Quote
Old Aug 25, 2014, 09:06 PM
23Chaos23 is offline
Find More Posts by 23Chaos23
Registered User
Australia, QLD, Shoal Point
Joined Apr 2014
67 Posts
anyone know how to embed a video in a post? ill do the second part today and every Tuesday from now.
23Chaos23 is offline Find More Posts by 23Chaos23
Reply With Quote
Old Aug 25, 2014, 10:40 PM
23Chaos23 is offline
Find More Posts by 23Chaos23
Registered User
Australia, QLD, Shoal Point
Joined Apr 2014
67 Posts
ok part 2 of the video blog is up here
23Chaos23 is offline Find More Posts by 23Chaos23
Reply With Quote
Old Aug 26, 2014, 05:31 AM
23Chaos23 is offline
Find More Posts by 23Chaos23
Registered User
Australia, QLD, Shoal Point
Joined Apr 2014
67 Posts
update time

23Chaos23 is offline Find More Posts by 23Chaos23
Reply With Quote
Old Aug 26, 2014, 10:31 AM
daniel lö is offline
Find More Posts by daniel lö
Registered User
Sverige, Hallands Län, Varberg
Joined Jul 2006
99 Posts
I am sorry but i rely don't understand your engine setup. Two edf units in line have been tested before and don't work very well at all. But you add a convergent tube behind the first edf and expect a increase in pressure. To have a gas increase in pressure you need a divergent channel but disregard that for a moment why do you even need a pressure increase in the first time.
In the convergent channel you have now you get a velocity increase and a pressure decrease.
A edf need very clean air going in to work in a efficient way. Your second edf work in the exhaust of the first and only that create turbulence but you added the mixing of a slow moving air and very fast moving air witch create even more turbulence.
The impeller in a edf work just like a propeller and they do produce less thrust the closer you get to it's perfect pitch speed so a high airspeed in is bad.

With that all i want to say is that you are much better of going with two more power full edfs. Less money, less weight and less parts.
daniel lö is offline Find More Posts by daniel lö
Reply With Quote
Old Aug 26, 2014, 10:54 AM
23Chaos23 is offline
Find More Posts by 23Chaos23
Registered User
Australia, QLD, Shoal Point
Joined Apr 2014
67 Posts
Quote:
Originally Posted by daniel lö View Post
I am sorry but i rely don't understand your engine setup. Two edf units in line have been tested before and don't work very well at all. But you add a convergent tube behind the first edf and expect a increase in pressure. To have a gas increase in pressure you need a divergent channel but disregard that for a moment why do you even need a pressure increase in the first time.
In the convergent channel you have now you get a velocity increase and a pressure decrease.
A edf need very clean air going in to work in a efficient way. Your second edf work in the exhaust of the first and only that create turbulence but you added the mixing of a slow moving air and very fast moving air witch create even more turbulence.
The impeller in a edf work just like a propeller and they do produce less thrust the closer you get to it's perfect pitch speed so a high airspeed in is bad.

With that all i want to say is that you are much better of going with two more power full edfs. Less money, less weight and less parts.
you find me a 90mm EDF that produces as much thrust as the ones im using. 3.6kg at 8s and just over 4kg at 10s. i understand how EDF like to use clean air, the first EDF uses near ATMO pressure while the second one over comes the velocity increase of the airflow with higher pressure. secondly the airflow in the second EDF will have slower new air around the outside where the impeller is at its higher velocity and the inside will be propelling the higher pressure air where the rotational force is higher.

i get what your trying to say and i faced the same issue when i started and decided to use twind EDFs to make up the thrust shortfall. from what ive learned with gas flow dynamics in gas forge building and what i researched on exhaust thrust reclamation. with some fine tuning i should get up to 5.5 even 6 KG with a 10s setup, thats nearly as much as a gas turbine with similar dimensions.
23Chaos23 is offline Find More Posts by 23Chaos23
Reply With Quote
Old Aug 26, 2014, 11:20 AM
daniel lö is offline
Find More Posts by daniel lö
Registered User
Sverige, Hallands Län, Varberg
Joined Jul 2006
99 Posts
with e-jets jetfan-90 and Het 7068 1200kv and 12s lipo you get 5,3kg thrust at 95A.

But go ahead with you setup i am curious to see how it's going to work out
daniel lö is offline Find More Posts by daniel lö
Reply With Quote
Old Aug 26, 2014, 10:00 PM
23Chaos23 is offline
Find More Posts by 23Chaos23
Registered User
Australia, QLD, Shoal Point
Joined Apr 2014
67 Posts
Quote:
Originally Posted by daniel lö View Post
with e-jets jetfan-90 and Het 7068 1200kv and 12s lipo you get 5,3kg thrust at 95A.

But go ahead with you setup i am curious to see how it's going to work out
you mean this one as much as i love CF and i REALLY LOVE CF, this wont work. first off all the specs on this i can find for the various models only got to 8s, so 12s would be dangerous.

this site says
Thurst is 3,6kg for 95A in 8s configuration. Can be up to 4,6kg and higher with higher voltage configuration.

JETFAN Ducted fans are already balanced.

Description :

Length : 58,6mm
Rotor diam.: 88,6mm
Indisde diam.: 90mm
Outside diam.: 93mm
For: 3-12s Lipo (11,1 to 44,4v)
Input power: 750-5500 watts
Max RPM: 55 000
max static thrust: 6,5kg

Rotor: 9 blades
Weight: 122g
Motor housing: accepts 36-41mm DIA motors
Shaft adapter: accepts a 5mm DIA motor shaft
Delivered without motor !
also the wires come out the back, which i really dont like, to get the most of your thrust you need the EDF as close to the exhaust as possible and that means running the wires back around. At around $300 without the motor they are quite pricy, but hey im looking at over $1000 for 4 EDF units. if you know of a bench test video that tests the thrust for this motor i would like to see it, i like my mercury alloy EDFs but im still open to better options. all in all there is very little information on this product that i can find, i googled it and this thread came up in the top ten results soooo let me know what you know
23Chaos23 is offline Find More Posts by 23Chaos23
Reply With Quote


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Discussion Waiting for a Scale 90MM SR-71 Aros Foamy EDFs 21 Mar 17, 2011 11:36 PM
SR-71 for EDF 50 (Closer than we might think) Thomas B Electric Ducted Fan Jet Talk 187 Feb 22, 2011 10:56 PM
Discussion 90mm SR-71 -- Collaborative effort! Willmsy Electric Ducted Fan Jet Talk 116 Jul 11, 2010 11:33 AM
Discussion Looking for a Solidworks Design Partner - SR-71 (90mm) Willmsy CAD/CAM 1 Jul 08, 2010 10:28 PM
airfoil shape for edf sr-71 Vince Ruhe Modeling Science 0 Jul 02, 2002 11:12 PM