Wicked powered SR-71 - Page 41 - RC Groups
Thread Tools
Oct 21, 2011, 06:49 PM
Indoor Free Flight Modeler
watts = volts * amps
volts = watts / amps

So if you have 1000 watts at 70 amps then your lipo is at 14.28 volts under load which is very low for a 4000 40C lipo. So either your lipo is not fully charged or if it is fully charged then it has been discharged too far after flying and has damaged the "C" rating of the lipo. On that lipo I would expect your voltage under load to be closer to 15 volts or higher. It is a lipo battery issue only since it is voltage sag. I would expect that kind of voltage sag if you were pulling 40C or higher which would be over 160 amps.
Sign up now
to remove ads between posts
Oct 21, 2011, 07:16 PM
Registered User
sanman55's Avatar
Thanks for the info Don,, it was actually only cold charge, 90% charge..and the numbers I gave were not exact just approx..will do a better test later ..I never discharge below 80% and never over amp...its a fairly new battery..The cells internal resistance is around 3.4 milly ohms, according to my fma charger...quite low..I should have been more accurate with my info...
I was disappointed because I thought that with the smaller diameter of the tubes I would have gotten more output than I had on the su-34.
Last edited by sanman55; Oct 21, 2011 at 07:22 PM.
Oct 21, 2011, 07:27 PM
Indoor Free Flight Modeler
If you are running ~80% FSA I usually do not see a wattage difference in these fans in this watt range. When you start running 70% I have seen an increase happening.
Oct 23, 2011, 02:25 PM
Registered User
sanman55's Avatar
Well ...she is ready to go, just want to taxie down the road for stearing...I still do not have the parachute ready..maybe later...I left the bottom door I cut in place with magnets to replace later..
Probably tue...thats my regular flying day with my friends...I feel confident that it has the powdr and is ready...just need to remember to keep the speed up,, esp. in landing.....hope I can keep it soft on landing so the gear will last..
Ended with final weight of 52 ounces..about 338 watts per lb...
I think the red intakes and the flames on the verticle will help a lot in seeing it....
Oct 24, 2011, 09:50 AM
Registered User
sanman55's Avatar
Stearing is great ..the forcast for tomorrow is GREAT..

I do have one more question before take off if anyone is out there

The nose wheel is not even with the other gear..mains 2 1/4 high at axle and nose 3 3/8...this gives it quite an up on the nose...when taxieing the nose would bounce up a little...cg is right at the back of the receiver hatch...
Is this going to be a problem??? These are the gear that came with it...One of my bud tells me that the real sr has a high angle on take off...There is really nothing I can do about it ..just curious...I could hold down elevator till I build up speed?
Thanks for the input..
Oct 24, 2011, 02:56 PM
redlite's Avatar
The high nose gear will help the model rotate off the runway by giving it a good angle-of-attack. The initial SR takeoff was quite level until the plane was off the ground a bit...then the AOA was much steeper. Your model sounds like it is right on the mark. This plane is very roll sensitive, so it likes to rock the wings...the settings recommended in this thread for the elevons is a must. Keep it level on your first flight and a long approach, using the throttle to maintain decent will help the landing. Don't cut the power until touchdown...the model is very light and is really not that hard to fly, just a bit hard to control when it gets into trouble...best to fly fast and level, like the big one!

Good luck and best wishes...Joe
Oct 24, 2011, 06:19 PM
Registered User
sanman55's Avatar
Thanks..good info...
Oct 25, 2011, 11:55 AM
Registered User
sanman55's Avatar
Ok guys hear is the report.....
She flew Boy was there power...she climbed like a rocket and flew around at about 40 per cent power...WOW..
had 40 % expo.. but wings still rocked but controalable...
Very hard for these old eyes to see..even with the flames...once it went straight down but pulled out with no problem..will have to do some bright painting...better to see it or crash it...
Ok...did short flight, maybe 3 min.. and it seemed ok...rocking calmed down..set up and had great approach...nailed the landing
Only problem was that I let it roll off the runway into the grass and all three wheels snapped off..

So...I need landing gear and will start hear...any suggestions???
Link to some??
Only used 1400 mah after 3 min. flying of 4000 mah available
Going to have some nice flight time
This is going to be a great bird ...Thank ful they did not fold up on the run way...landed hot but looked so cool....
Last edited by sanman55; Oct 25, 2011 at 12:00 PM.
Oct 25, 2011, 05:58 PM
Registered User
sanman55's Avatar
Well, I found out that my su-34 gear will work just fine...at lot more beef
Have the mains done and just have the nose left...
What a day...overall I am happy..

I hate to do this but I just can not see this bird..so I am thinking about florcesent green or orange on the verticles...does anyone have any suggestions that would help??
I almost lost her 3 times and my buds said they were glad I was flying and not them...I was thinking reflective silver but don't think thats good enough...
Last edited by sanman55; Oct 25, 2011 at 07:51 PM.
Oct 26, 2011, 11:00 PM
redlite's Avatar
Congrats on your maiden...

Oct 27, 2011, 08:34 AM
Registered User
sanman55's Avatar
Landing gear installed and the new color scheme...Like it or not I think this will help with the sighting and orientation
Now to poor the throttle on and see what she can do....
Oct 30, 2011, 05:54 PM
Shameful Warbirdaholic.
Aros.MotionRC's Avatar
Since the Habu is my favorite all-time bird, I cannot say I love the trim schemes I'm seeing.

Now do I agree with the need in the RC realm? ABSOLUTELY! In that spirit, I say, "Well done!"
Oct 30, 2011, 07:26 PM
Registered User
sanman55's Avatar
If you think thats bad you are going to hate what I did...I still could not see it .. barely got it back...so its now all yellow on top and black on the bottom...if that does not do it than I am switching to orange...
This baby is fast ...had to go to 1/4 throttle to stop it from climbing...The landing gear held up fine..I am at the point now that what ever it takes it gets It kind of grows on you...........................
Last edited by sanman55; Oct 30, 2011 at 07:39 PM.
Oct 30, 2011, 07:39 PM
Shameful Warbirdaholic.
Aros.MotionRC's Avatar
Make no mistake about it. This is the most difficult plane I have ever attempted to fly in my 5 years in the hobby. Now, before you go assuming I've flown nothing but trainers let me assure you, I have flown tons of EDFs, tons of warbirds (some composites with high wing load like the full scale, some with low wing load like most foamies), high wings, low wings, you name it.

There's a reason (or two) I've owned 6 of these planes.

One, because they have crashed time and time again. Two, because my love for this plane outlasts my common sense which says in bold letters: MOVE ON ALREADY!

No other plane is built like this one. That's what makes it so much fun to fly! The fuse is SO long. The delta wings are SO short and SO far aft. Makes for a fun recipe, eh?

If I had a dollar for every failed hand launch and sortie, I could buy a new airframe from BH. Yet, here she sits in my garage. Complete with a fancy afterburner kit thanks to Joe...With a new nose (thanks to yet another failed hand launch) ready to brave the skies again.

Man, I have wasted over $2,000 on this bird.

And I wouldn't take a single cent back.
Oct 31, 2011, 08:44 AM
Registered User
sanman55's Avatar
It is addictive I think I have the parachute worked out...When I deploy I also have the elevator go full down to help keep the nose on the ground...have some trouble steering on landing cause of the speed and the nose keeps bounceing and will not stear
I have not even been able to put her thru her paces yet...when I can finally see her the fun will begin...if I don't crash her first...think I have used up a lot of my luck points so far

Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
SR-71 for EDF 50 (Closer than we might think) Thomas B Electric Ducted Fan Jet Talk 187 Feb 22, 2011 11:56 PM
SR-71 anyone? steve neill Electric Ducted Fan Jet Talk 71 Oct 08, 2007 08:34 AM
hobbylab sr 71 bushpilotx1 Sport Planes 7 Mar 06, 2002 01:53 AM
Electrics that can outperform the SR-71? SchiessCo Electric Plane Talk 4 Jul 30, 2001 09:44 PM