Official Freewing Twin 70mm SR-71 Blackbird with Gyro EDF Jet Thread

[kallend]

Or is it?

https://www.hobbysquawk.com/forum/rc-airplanes/rc-jets/419430-official-freewing-twin-70mm-sr-71-blackbird-with-gyro-edf-jet-thread?p=420072#post420072

"Always" is not the same as ""sometimes"

"Very few" is not the same as "none".

Incidentally, the last several FW models I have bought did not have unfinished white EPO inside the tailpipe. They were painted grey.

[Evan D]

Or is it?

_DSC0040.jpg (900×598)

[kallend]

I'm a major "scale" guy and I think your black thrust tubes look great. Light absorption could be an issue if you did choose to add afterburners but I think the black thrust tubes look better than the white stock ones personally.

Your model, your choice, but don't pretend it's scale.

[kallend]

Okay, thanks. Let's see if I want to try an "afterburner" after all. Since it reduces the jet power rather than increases it, I'm just not a fan of this whole afterburner thing so far.

Even that statement is disputable, since some designs (but not all) actually do a good job of fairing in the blunt rear end of the motor.

[Aros]

You're right, I think the EPO thrust tubes are ugly, cheap... they look like toys. Black is good for me, I've never used these afterburners in any jets that partially glow when idling, I don't think they're particularly realistic. But as you say, to each his own, they're not real jets.

I'm a major "scale" guy and I think your black thrust tubes look great. Light absorption could be an issue if you did choose to add afterburners but I think the black thrust tubes look better than the white stock ones personally.

[EDF-Jetpilot]

There's only one brand that glows while idling (and even there the fix is simple). The good ones do not. You should get out more.

https://www.rcgroups.com/forums/showthread.php?4311903-Freewing-Tailflame-afterburner-problem-and-solution

And if you're at all handy, you can make one that behaves exactly how you want it to, since it's fully programmable:

https://www.rcgroups.com/forums/showthread.php?3313547-Make-a-Do-it-Yourself-EDF-afterburner

Since it can drive two tailpipes independently it would be perfect for this SR-71.

Okay, thanks. Let's see if I want to try an "afterburner" after all. Since it reduces the jet power rather than increases it, I'm just not a fan of this whole afterburner thing so far.

[kallend]

I've never used these afterburners in any jets that partially glow when idling, I don't think they're particularly realistic. But as you say, to each his own, they're not real jets.

There's only one brand that glows while idling (and even there the fix is simple). The good ones do not. You should get out more.

https://www.rcgroups.com/forums/showthread.php?4311903-Freewing-Tailflame-afterburner-problem-and-solution

And if you're at all handy, you can make one that behaves exactly how you want it to, since it's fully programmable:

https://www.rcgroups.com/forums/showthread.php?3313547-Make-a-Do-it-Yourself-EDF-afterburner

Since it can drive two tailpipes independently it would be perfect for this SR-71.

[EDF-Jetpilot]

Photos of real jets show otherwise. The pictures I posted were of real F-104, F-14, F-15, F-16, F/A-18, F-35, Mig-29 and SU-35 none of which are black inside. Actual B-1B nozzles below - not black inside either. Jet exhaust stopped being sooty sometime in the 1960s. Afterburners burn off any soot anyway.

But if if floats your boat to paint them black because you like it and think the authentic coloration is ugly, that's your prerogative. They're your models and you can paint them anyway you like.

(Black wouldn't help with any simulated afterburners.)

You're right, I think the EPO thrust tubes are ugly, cheap... they look like toys. Black is good for me, I've never used these afterburners in any jets that partially glow when idling, I don't think they're particularly realistic. But as you say, to each his own, they're not real jets.

[kallend]

Yes, OK... but the white, like the EPO jets, is just ugly and unnatural. I like black best on any jet and thanks to the exhaust fumes it's somehow logical and natural. The coatings are good, but on the model it looks artificial, I think.

Photos of real jets show otherwise. The pictures I posted were of real F-104, F-14, F-15, F-16, F/A-18, F-35, Mig-29 and SU-35 none of which are black inside. Actual B-1B nozzles below - not black inside either. Jet exhaust stopped being sooty sometime in the 1960s. Afterburners burn off any soot anyway.

But if if floats your boat to paint them black because you like it and think the authentic coloration is ugly, that's your prerogative. They're your models and you can paint them anyway you like.

(Black wouldn't help with any simulated afterburners.)

[Evan D]

They look good to me.

[EDF-Jetpilot]

Always? Some nozzles are ceramic coated and are indeed white. Others are natural metal. Very few are black inside.

this is my awesome back side my planes

[EDF-Jetpilot]

Always? Some nozzles are ceramic coated and are indeed white. Others are natural metal. Very few are black inside.

Yes, OK... but the white, like the EPO jets, is just ugly and unnatural. I like black best on any jet and thanks to the exhaust fumes it's somehow logical and natural. The coatings are good, but on the model it looks artificial, I think.

[kallend]

. I also always paint the inside of the thrust tubes black, most of them are delivered in white,.

Always? Some nozzles are ceramic coated and are indeed white. Others are natural metal. Very few are black inside.

[EDF-Jetpilot]

Good point. I will probably do the first couple of flights with the stock gyro then see about switching over. I like to fly with SAFE. Part of the hobby is tinkering.
I'm hoping to hear from others who switch to Spektrum AS3X receivers.

Also,part of the hobby is model detailing. Not much to do with this one. A lot of models come with black control horns and control-rod ends, so why, oh why did Freewing opt for white ones on the Blackbird? Detailing list: paint the control rod heads and servo horns flat black (carefully so as not to interfere with their operation); take a Sharpie (rather than paint) to the screw heads (it is surprising how much difference in ground appearance this makes); probably going to do this up as a NASA plane and get Callie Graphics instead of using the included water decals; maybe trade out the stock pilots for 1/17 scale (smaller) if I can find some.

Yes, I would do that too. I fly everything with Spektrum (AS3X and Safe, sometimes for landings in gale-force winds) and I'm very happy with it. But I'll definitely leave the SR-71 in its original state for the first few flights. But the white control horns... ugh, you said it! I'll paint them with a black felt-tip pen before the maiden flight, I'm just as meticulous as you. I also always paint the inside of the thrust tubes black, most of them are delivered in white, i.e. raw EPO, so ugly. Maybe I'll set up the SR-71 with AS3X and Safe afterwards, we'll see, but first see how well it flies with the original gyro.

[GliderGuy]

Hi Evan…Appearance is not always reality. When the AL-37 connector melted, I dissected it and noted the “rolling” of the springy banjo part. I assumed this was a problem which might have been caused by the excessive heat or was a contributing factor to the heat generation. My bad!

Thanks for the education.

_____________

With the AL-37, PJ-50 and B-2 all running 2100 KV motors and the SR-71 using the more powerful 2210 KV motors, I am going to change the SR-71 to the split barrel type ASAP. I’ll sleep better.

_____________

It is also evident that the goal of a 4:30 flight like the B-2 and PJ-50 is unlikely even at 50% power. 4 minutes maybe….with throttle management.

Cruising around at 75% is gonna mean 3:00 to 3:30 flights and require throttle management with a single 6000 mAh battery with 3.8 V remaining as I have measured so far. I have yet to do a full power pass. Doing that = 3 min max.


-GG

[Evan D]

GG, on the "banjo" type ones I have the springy banjo part is not soldered to the pin part and can roll on it. Maybe you have some where a little solder got on soldering the pin on the wire or something?

Here’s my experience…male (airplane side) EC5 melting. It first happened with an AL-37. Investigating…it was determined the contact screen/spring had deteriorated and became highly resistive. The P = IxIxR heat melted the blue plastic.

The fix = new EC5 or replace with the split barrel flower petal type (no contact screen).

Mind you it took lots of flights before the EC5 got to this point of deterioration. Any of the single-battery 70 mm fan ships “might” have this happen. Here’s a summary from my ships: AL-37 = once, PJ-50 = 0, B-2 = 0, SR-71 = 0, A-10 = 0, F-4 = 0, MIG-29 = 0.

It’s no secret that some of these birds have over 1,000 flights, so the EC5 melting issue isn’t common. Otherwise, I would have seen it more than one time.

If you don’t like the split-barrel flower petal type EC5, and each type has its detractors, then frequently inspect with a bright light the condition of your connector’s barrel spring/screen. Each connection “spark” blows away some of the connection spring/screen. This type connector will succumb to this spark effect eventually.

Now to go see what type connector design the SR-71 has. It has the spring/screen type connector.
Added note: Even early on, the solder or braze between the inner shaft and the spring/screen could fail making for a high-resistance connection = heat and melt early in its life.

-GG

[Evan D]

The issue of over heated/ melted EC5's has happened a few times over the years and as far as I can tell is caused by one type of male pin on the connectors. There are two types of EC5 pins, see the picture attached. The left is what I call split type and the right "banjo". The split as GG notes is a much more robust type.

There has been ONE reported case of the issue with the SR71 and in my opinion it is caused by the amount of power, Amps, drawn by two fairly powerful fans running off a single battery through a single connector. Each fan is capable of pulling 80+Amps so a freshly charge battery may supply 150+Amps (there would be some dragging down of the battery at this level of current). This is more that even a 8S 90mm EDF would draw so we are seeing this for the first time on FreeWing planes.

So what can we do? Well first, it is going to be rare and probably when someone has a good battery, more than likely a high C or HV battery that can supply the amps to do the damage. And probably when someone flies long periods of full throttle. And as GG notes repeated connecting of the connectors is deteriorating the springy thin banjo part of the pins so after time you may develop the issue.

What to do?

First, if you ever feel your connector, any connector, is hot find out why, it means there is electrical resistance in the connection and that will only get worse.

Also again, this may never be a problem on your plane. Just reducing timing or limiting full throttle usage to a few short fast passes may prevent it from happening. Going to better connectors would be a better way. If you are happily using EC5s and have a lot of batteries with them changing the male pins in the ESC connector with the split type pin should also work. And of course going to larger connectors like AS150's would solve the issue though I think that is over kill, especially if you have a lot of batteries and planes with EC5's.

Another thing is the spark when connecting the battery, that will wear out your connector and adding an anti-spark in line could also help, I would say not prevent but help.

Another choice would be to run two batteries in the SR, one to each ESC so each would see the 80A instead of the full 150A and this may be a great choice for some that have a supply of 6S 3300mAh but would require splitting the battery leads from the two ESCs and soldering connectors and some extensions to the wires. This could have the side benefit of larger battery over all for longer flight times and as the SR has two bays I think some may already be thinking of doing this.

[GliderGuy]

Here’s my experience…male (airplane side) EC5 melting. It first happened with an AL-37. Investigating…it was determined the contact screen/spring had deteriorated and became highly resistive. The P = IxIxR heat melted the blue plastic.

The fix = new EC5 or replace with the split barrel flower petal type (no contact screen).

Mind you it took lots of flights before the EC5 got to this point of deterioration. Any of the single-battery 70 mm fan ships “might” have this happen. Here’s a summary from my ships: AL-37 = once, PJ-50 = 0, B-2 = 0, SR-71 = 0, A-10 = 0, F-4 = 0, MIG-29 = 0.

It’s no secret that some of these birds have over 1,000 flights, so the EC5 melting issue isn’t common. Otherwise, I would have seen it more than one time.

If you don’t like the split-barrel flower petal type EC5, and each type has its detractors, then frequently inspect with a bright light the condition of your connector’s barrel spring/screen. Each connection “spark” blows away some of the connection spring/screen. This type connector will succumb to this spark effect eventually.

Now to go see what type connector design the SR-71 has. It has the spring/screen type connector.
Added note: Even early on, the solder or braze between the inner shaft and the spring/screen could fail making for a high-resistance connection = heat and melt early in its life.

-GG

[Aros]

Woo Hoo! 4 more fantastic and FUN flights at sunrise before the wind came up…24F brrr.

NAILED IT! 50% expo on both the aileron and elevator channels is the sweet spot. She feels GREAT and behaves as you’d expect. Not pitchy on the approach at this expo.

She feels really good at 75% throttle, but good at a bit more than 50%, too. She needs added up elevator in the turns…especially steeper banks. What a presence in the air and on a lower height fly-by!!!!

Fairly normal EDF approach. Plan it like you do your other EDFs. I was high and fast on one base leg and chopped the throttle 0 thrust. Glide on final and then just a touch of power to reduce the sink rate. She did fine.

All were normal main-first touch downs. And she sticks without bouncing.

Right now, I’m staying with 3:30, but will experiment more at lower power cruise to get to 4:30…maybe. She feels so solid at 75% power, lower throttle will take some getting used to.

Get your CG right and 50% expo dialed in. You are going to LOVE this RC plane. Thank you FW/MRC for putting this unique beauty plane in our hands!

-GG

Another nice report, thank you! Funny, by instinct alone I put my dual rates at 50% expo before reading this post. Just "felt right". I have the recommended throws for now. CG will be manufacturer's recommended.

Compared to the wildcat that was the LX version, this bird looks like she flies much more tame.

Hearing someone had their EC5 connector melt or something on the RCG thread. Now some folks are worried about needing to switch out their connectors. You have flown yours several times on a single 6S I assume without any issues?

Evan D has had a lot to say about the matter and would love for his expertise to weigh in here.

[Aros]

Someone at FW or MRC who has some hours on the SR-71 should get high over the field and try it. Then post a “how to” for the other owners.

I will gladly borrow yours to try it out!