R/C SR-71 Hobby lab

I recently picked up a Hobby Lab RC SR-71 . Basically it was just a frame and now i got the rc working.
Trimming is the next step and after that, launch.

I know that it is recommended to fly with an E15-P composite. And that is where the problem lies. These are not easy to buy obtain in the Netherlands, nor an aerotech E15-W RMS (and then not using the ejection charge). Now i do have some D11P's lying around here. and they match with the required minimum lift off weight.
that is about 14,5 ounces.

And then my question, what would be the expected altitude appogee, if i were to use a D11P in stead off a E15-P?
Does anyone have experience with the above combination (SR71-HobbyLab, wirh D11-P)?


Thanks!

Thanks Jim!
Any idea how high this will go on a D12? I am trying to guestimate my "recovery height" as i take over control after boost. And, using the D12, do recommend to launch it vertically or under an angle (and of so, how much)?
Just for comparison, how heavy is your SR-71?

Not very high, 30-40m or so? Fly it straight up, you won't get a lot of lift from the wings trying to fly at an angle. The RC version will want to roll if you give it a lot of left or right. Use lots of expo in your transmitter if you can.

I remember some flights of my free-flight version would start to loop as the D11-P motor burned out, and just barely pull put a meter or so above the ground.

Good luck!

kj

That is helpful information. I am now convinced that i defenitley need a stronger engine than the D11P. I am now trying to convince one of the members of our rocket club to join in this project, that is supplying or renting out the engine. Also i am searching if i can find such motors in the netherlands.

One last thought: CHAD staging a D12-0 and a D11-P on this bird.
Any thoughts on that?

I had thought of that after my last message. I don't remember what the motor hook looks like on the kit, but you may have to bend it straight, then tape the D11 to it.

You shouldn't have an issue with the CG changing too much for boost.

kj

kjohnson said:

I had thought of that after my last message. I don't remember what the motor hook looks like on the kit, but you may have to bend it straight, then tape the D11 to it.

You shouldn't have an issue with the CG changing too much for boost.

kj

Click to expand...

Thanks! I am still curious to how high it will go. I started with some basic physics equations that i try to upload. It calculates the altitude based on the total impuls and burn time.
Then i thought that I might use rocksim to find out what the flight profile might look like.
So i found the estes SR-71 file, used the Cd of that and tried to make an upscale version in rocksim. Estes is 19 inch in length, and teh hobby lab is 34 inch, weight is 3.2 ounce versus 14 ounce (451 gr). The trouble i have there is that i want to do a mass override (rocksim calculates the mass at 350 gr) and move de Cg to the center of the motor. Does anyone know how to move the Cg to the just before the wing attachment, and move the weight up?

View attachment Motor keuzes.xlsx

View attachment estes_sr-71_blackbird Hobby lab.rkt

And another question, does anyone have a decal sheet for an SR-71 (estes of hobby lab ) that i can print?

heut said:

Thanks! I am still curious to how high it will go. I started with some basic physics equations that i try to upload. It calculates the altitude based on the total impuls and burn time.
Then i thought that I might use rocksim to find out what the flight profile might look like.
So i found the estes SR-71 file, used the Cd of that and tried to make an upscale version in rocksim. Estes is 19 inch in length, and teh hobby lab is 34 inch, weight is 3.2 ounce versus 14 ounce (451 gr). The trouble i have there is that i want to do a mass override (rocksim calculates the mass at 350 gr) and move de Cg to the center of the motor. Does anyone know how to move the Cg to the just before the wing attachment, and move the weight up?

Click to expand...

I meant: move the Cg forward in the RockSim file and increase the weight of the plane.
Any ideas?

I would be careful with this, chad staging another D on the end will move the CG back 3/4 to 1 inch I think, and that will probably put it behind the marginally stable point. You are adding 1.5 oz or so and the CG is at least 12" forward of that.

Frank

kjohnson said:

I had thought of that after my last message. I don't remember what the motor hook looks like on the kit, but you may have to bend it straight, then tape the D11 to it.

You shouldn't have an issue with the CG changing too much for boost.

kj

Click to expand...

This won't help you quite as much, but after the habitual "fold" at the battery bay that happens if you dork this model, I reinforced the model with two carbon fiber rods along the length of the model( inside along the motor tube all the way to the front), but batteries in the nose to counter the 32mm mount I added.

The model is a gorgeous flier if you do this , but it will go out of sight on the G12 Aerotech to over 1000' (this model is REAL fun to orient at that altitude), but if you are a good flier, you can have a good 8 second burn under power. The F23 is a perfect compromise.

Guys this is an awesome thread and an interesting project but modding motors and doing horizontal flight are not topics for around here. I am not judging or raining on your parade but that sort of thing is beyond what we do here. if you have any questions please feel free to contact me or Kevin.
Cheers
fred

Fred,

Not sure if you were referring to my post or not, but mine is simply a modification to the R/C SR-71 Hobby Labs kit to make it fly longer in the air. The original (SR-71) R/C boost glider kit can be flown on the way up and down as most kits can. I was merely referring to a longer lasting version. All the kits from Estes to Aerotech have the same option. Perhaps there is a special R/C Boost glider section? If so, my oversight.

This is of course assuming you were referring to my post

David

Fred22 said:

Guys this is an awesome thread and an interesting project but modding motors and doing horizontal flight are not topics for around here. I am not judging or raining on your parade but that sort of thing is beyond what we do here. if you have any questions please feel free to contact me or Kevin.
Cheers
fred

Click to expand...

OK, I give up. Thats twice now you mentioned modding motors, once personally to me. Where in this entire post does anyone say anything about modding motors?

jimzcatz said:

OK, I give up. Thats twice now you mentioned modding motors, once personally to me. Where in this entire post does anyone say anything about modding motors?

Click to expand...

No where because I pulled the post.
Cheers
fred

R&R Model Aircraft said:

Fred,

Not sure if you were referring to my post or not, but mine is simply a modification to the R/C SR-71 Hobby Labs kit to make it fly longer in the air. The original (SR-71) R/C boost glider kit can be flown on the way up and down as most kits can. I was merely referring to a longer lasting version. All the kits from Estes to Aerotech have the same option. Perhaps there is a special R/C Boost glider section? If so, my oversight.

This is of course assuming you were referring to my post

David

Click to expand...

Is the rocket under power and flying horizontally on purpose? If not then I misinterpreted some elements of the thread perhaps?
Cheers
fred

Irregardless of your interpretation Fred, he never mentioned modifying a motor.

Fred,

I was referring to doing aerobatics under power ( much as is done with the Aerotech Phoenix, etc.), but mostly control on the way up and down. Many of the planes can be started as a rocket (boost) and flown in loops, etc., before their power goes out.

Most control on the high impulse part of the boost are for getting the model altitude and airspeed. The G-12 that I am referring to in this is excellent for getting to altitude and allowing gentle, powered aerobatics until the motor is spent. The problem with the Hobby Labs SR-71 was that it got too small too quickly with this motor and had to level out at about 700' (pointed away from the crowd) and do some mild aerobatics to burn off airspeed until it was safe to bring into a landing.

jimzcatz said:

Irregardless of your interpretation Fred, he never mentioned modifying a motor.

Click to expand...

Okay I pulled a post where somebody was talking about pulling apart or changing the interior of an estes motor. It was your post Jim. If your referring to Heut he did not and you are correct.
cheers
fred

R&R Model Aircraft said:

Fred,

I was referring to doing aerobatics under power ( much as is done with the Aerotech Phoenix, etc.), but mostly control on the way up and down. Many of the planes can be started as a rocket (boost) and flown in loops, etc., before their power goes out.

Most control on the high impulse part of the boost are for getting the model altitude and airspeed. The G-12 that I am referring to in this is excellent for getting to altitude and allowing gentle, powered aerobatics until the motor is spent. The problem with the Hobby Labs SR-71 was that it got too small too quickly with this motor and had to level out at about 700' (pointed away from the crowd) and do some mild aerobatics to burn off airspeed until it was safe to bring into a landing.

Click to expand...

Sounds great and I hope you keep discussing it. I personally would like to see the beast in action. Only thing i like better then an SR71 is a U2 Sometimes these things are a matter of fine interpretation and I do my best. In no way do I wish to shut down an informative thread such as this one. Please carry on.
Cheers
fred

Thanks, Fred. Wasn't sure on the rules.:handshake:

That said, I'll see if I can take some photos of the mods to the SR-71 as this will make sense of what I have written below. (this is only an overview, not a step by step)

The first mod is chucking the R/C system that comes with it (or just buy the boost- glider only version and convert). Nobody that flies R/C uses a system like the one that comes with the model (the one that comes with it appears to be a cheap surface-type system). You want the controls on one stick - the right stick (Mode 2) aileron/ elevator (elevons). Most inexpensive (real) radios nowadays are setup this way and have mixing capability (not necessarily needed). You can still use the servos that come with it which is setup as a mechanical mixer and seems to work fine.

With the extra weight of the bigger motor (no 24mm motor has enough ummph to get this in the air properly - we tried all even before the mods), the battery needs to go in the nose. I used two thin stick batteries for weight / current in parallel and ran the antenna to the new receiver down the inside of the central section.

The large tube that houses the 24mm engine tube is only screwed in place as they had it setup to also house a gas motor if you wanted to. This makes the mod to 32mm easy. You can still use the original mount, but I would throw it away myself.

Two, 1/8" carbon rods are inserted along the inside of the frame along the engine tube up to the nose. This adds a ton of strength and hopefully you can avoid breaking the back of this model if you put it in hard.

The best motors are the 32mm "F's" that Aerotech offers. They give reasonable flight time without it going beyond visual. The G12 will make this get small very quickly! I still would only do these mods if you are a decent pilot. It is a hard model to orientate in the air (black is not the best color from 500'+ away) and is very easy to lose. When it comes to piloting this model at events, I let my friend and test pilot (for my models) do it.

David

David, what is your new AUW, the G-12 is about 3 oz more than the aerotech e-15's I used to use in mine. What is your battery weight?

Frank

Fred,

I haven't flown it since last summer, so I will have to take some measurements and photos and post later (work is hell ).

I wish I had video. I (actually, my friend) will be flying it at NSL in May, so hopefully we can get some video.

David

Ok, guys, here it is. The overall weight (without motor or casing) is 15.6 oz. You can see from the photos that I have extended the hatch to access the existing servos (this was an original R/C version) and chucked the old receiver / battery case.

The two stick batteries (in parallel) are put right in the nose along with a little extra weight for proper balance. The receiver is a standard 72Mhz version, but I recommend a 2.4Ghz version. Otherwise you have to run an antenna (stuffed in the yellow nyrod tube) along the length of the model and above the elevator servo.

It is hard to see, but the carbon rod (solid, .125") runs along the engine tube and near the fuse inner edge. Just stuff from the back and tack in place.

Receiver is just velcro'd in place. Note that the new 32mm motor mount slides into the same place as the old. Also note the nice "fold" common to this model at the battery hatch position due to anything other than a perfect landing.

Hope these help.

David

Here are the rest.

David

There is one of these on Ebay, with a by it now of $79, I already have one, do not need another
https://www.ebay.com/itm/SR-71-Blac...pt=Radio_Control_Vehicles&hash=item4ad0b14360

Shipping is a little High

heut said:

I know that it is recommended to fly with an E15-P composite. And that is where the problem lies. These are not easy to buy obtain in the Netherlands, nor an aerotech E15-W RMS (and then not using the ejection charge).!

Click to expand...

If you can obtain E15-4 or E15-7, you can adjust the amount of BP on these motors: manufacturer recommends removing the rubber stopper on top of ejection charge and adding or removing powder as your rocket needs. Your particular rocket needs you to remove all powder then replace the rubber cap.

Fred--I hope I'm not stepping on anyone's toes with this. As best I can tell, this is not a motor modification, and in line with manufacturer recommendations for these single-use motors. Let me know if you feel different.

Ari.

R&R Model Aircraft said:

(no 24mm motor has enough ummph to get this in the air properly - we tried all even before the mods)

Click to expand...

David, I'm curious about this. Probably irrelevant to OP as he may have difficulty procuring AP motors, but I'm sure you know that CTI makes 24mm reloads up to full G. I've flown many many F30s, and I have a G65 waiting for its turn. These are excellent glider motors for larger models.

Ari.

I took the plunge and bought one of these yesterday. The $50 shipping is steep, but the total price is low. As I recall I bought one of these 10-15 years ago and the total price was was close to $200, so a total price of $129 is not bad. We shall see what the merchandise looks like when it arrives. I have used the idea of taking ejection charges out of composite motors before for gliders. In some ways this may even be better, because then model has tracking smoke. I had this model before and it worked fine on E15's. My downfall was using it on a windy day and another time running into a barbed wire fence on landing. Needless to say, I have learned my lesson about gliders and windy days. If it's windy, either don't fly or have a non-glider model to fly. With a glider it is better to survive and fly another day!

The SR-71 arrived in pretty good shape except for the battery housing in the rocket glider and in the transmitter. Luckily, I saved the transmitter from my HobbyLab SR-71 that I crashed years ago. Old corroded AA batteries were still in this new transmitter. I tried scraping the contacts, but that didn't work and, in fact one of the contacts far inside the transmitter broke. So, I took the crystal out of the corroded transmitter and put it in the old transmitter that I had saved. Likewise, the 4 AAA battery housing in the glider was corroded and would not work after scraping. I have several 4 AAA battery housings in my inventory, so I replaced the corroded housing. Everything now works fine.

I got the impression that the seller was someone that might deal in estate auctions. There was no bidding, I just paid the listed price. Later, the seller lowered the shipping cost by $16, so that the final cost was $113. The box was original, but had been opened and then resealed. The package came with everything that I had bought years ago. There were four single use E15-P's included.