Additive Aerospace "fly-away" rail guides ruined my big flight. How does this even happen?

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pugachu said:
Sorry About the altitude loss. What camera setup did you use? The pictures look good. You have a downward view, and usually that means you have something sticking out. I have a min dia 54mm that I'm flying this weekend, it has a camera in it, but I'm using a small mirror mounted on the side to point it downward. I don't like how much it sticks out, and the drag penalty it gives to a min dia bird. I'm looking for better ways to mount a high def camera without adding too much d
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80BACF22-F085-4DCE-A3B5-85EB8C0C9F75.jpeg
Might look a little clunky, but she flies, straight and true with this rig.
 
neil_w said:
I wonder if they would be a touch more reliable if segmented into at least, say 3 or even 4 hinged sections rather than 2. It seems like 1/3 or 1/4 of a ring would be less likely to inadvertently hang onto the rocket than 1/2.
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I think it just needs beefier springs. The opening action is not very energetic.
 
Porkchap said:
I think it just needs beefier springs. The opening action is not very energetic.
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Sorry, don't want to belabor the point, but was the guide placed right next to (meaning right on "top" of) the fin can? Based on the still shots, I think the guide was placed too high on the airframe and this is not in line with the directions from Additive. Isn't this the root cause of the issue in this case?
 
rfjustin said:
Sorry, don't want to belabor the point, but was the guide placed right next to (meaning right on "top" of) the fin can? Based on the still shots, I think the guide was placed too high on the airframe and this is not in line with the directions from Additive. Isn't this the root cause of the issue in this case?
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I answered this in post 32.
 
Buckeye said:
Are you saying fin strikes are less likely when the FARG is more than 24 inches above the fin???? I have never seen anybody put one that high on a rocket, and it seems nearly impossible and impractical to do so (you lose 2 feet of guidance). Also, this is counter to the recommendation to put the guide directly above the fins.

Do you mean greater than?
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As you move the FARG further forward above the fins, the chance of a fin strike is reduced. My preliminary data and calculations indicate that the chance of a fin strike is near zero at 24 inches for all but the highest accelerating and larger fin rockets. I hope to fly in November or December my first 500Hz instrumented rocket with a 500Hz instrumented FARG.
 
With that giant taped on camera, I don't understand why a FARG was being used in the first place. There was nothing to be gained aerodynamically, and FARGs are prone to a variety of issues, as described in this thread.

Personally, I have tried FARGs from 38mm to 75mm, and have decided they are only usable on rockets that don't need them. If speed and altitude are your goal, a tower is the only way to reliably achieve that. The photos posted by the OP show a great example of why that is the case.


Tony
 
techrat said:
There was a small vendor I ran into at URRF that was selling raindrop-shaped rail guides, which were supposed to reduce drag as opposed to "normal" rail buttons. Can't remember their name right now, but once I get home, I'll try and remember to look them up... because I've got a sticker from them on my range box. That's the ONLY way I can remember vendors. From stickers on my Range Box.
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Did that sticker look like that red and black logo up to the left !?!?
 
mtnmanak said:
Personally, I like the ones from SCP: https://scpconcepts.com/rocketry/airfoil-rail-guides/
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This is the vendor I ran into at URRF. These are the machined rail guides, they were metal, and much tougher looking than they needed to be. Your rocket could get completely destroyed, but the rail guides will still be salvagable to use on your next build. I bought a set for a 1010 rail, but haven't used them yet. Waiting for the right project...
 
techrat said:
This is the vendor I ran into at URRF. These are the machined rail guides, they were metal, and much tougher looking than they needed to be. Your rocket could get completely destroyed, but the rail guides will still be salvagable to use on your next build. I bought a set for a 1010 rail, but haven't used them yet. Waiting for the right project...
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I am surprised I didn't see Scott there! I had no idea he was making metal airfoils - some clubs do not like it when you use metal rail buttons because they can damage the rails. I thought he was making his buttons out of Delrin.
 
manixFan said:
With that giant taped on camera, I don't understand why a FARG was being used in the first place. There was nothing to be gained aerodynamically, and FARGs are prone to a variety of issues, as described in this thread.

Personally, I have tried FARGs from 38mm to 75mm, and have decided they are only usable on rockets that don't need them. If speed and altitude are your goal, a tower is the only way to reliably achieve that. The photos posted by the OP show a great example of why that is the case.


Tony
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I used it simply as a matter of convenience and wanting to try it out - if it improved performance slightly, all the better. Screwing in rail buttons wouldn't work for obvious reasons and I've had a conformal rail guide snap off while putting the rocket on the rail before, thus scrubbing the launch. Several suggested using a tower, but those aren't exactly readily available. Our club doesn't have one and neither did the club at Bayboro.

This seemed like a fun alternative to try. Maximum performance isn't so much my goal as much as "big motor in little rocket go zoom!!"

As for the camera, it gets a lot of hate. It's not as big as it looks, and getting those breathtaking images from it are my favorite part of the hobby. I won't fly without it. The camera stays, the FARG goes. I epoxied on conformal guides with JB Weld last night (properly this time).

Loading her up with a 6-grain CTI K711 for a redemption flight tomorrow. Not quite an L805, but still pretty spicy! Stay tuned for epic video...
 
2-0turbo said:
I was also impressed with the still captures. You posted a pic of the camera, but I can't find info. Which brand/model is that? Thanks.
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Sorry, it's the Mobius Mini ActionCam. You can pick them up on Amazon for about $70. Definitely go to the website in the instreuction manual and download the "ms setup" program. That allows you to plug it into your PC and play with all the settings and features - of which there are a surprising number.
 
mtnmanak said:
I am surprised I didn't see Scott there! I had no idea he was making metal airfoils - some clubs do not like it when you use metal rail buttons because they can damage the rails. I thought he was making his buttons out of Delrin.
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You are correct - the guides from SCP are CNC machined from one solid piece of Delrin.

I want to start getting to more launches, my wife and I had SO MUCH fun at the URRF event and can't wait for more.
 
This thread is weird to me. I know this is just anecdotal but it seems like I saw an awful lot of successful FARG flights at Airfest with some stupid fast flights...
 
Porkchap said:
I used it simply as a matter of convenience and wanting to try it out - if it improved performance slightly, all the better. Screwing in rail buttons wouldn't work for obvious reasons and I've had a conformal rail guide snap off while putting the rocket on the rail before, thus scrubbing the launch. Several suggested using a tower, but those aren't exactly readily available. Our club doesn't have one and neither did the club at Bayboro.

This seemed like a fun alternative to try. Maximum performance isn't so much my goal as much as "big motor in little rocket go zoom!!"

As for the camera, it gets a lot of hate. It's not as big as it looks, and getting those breathtaking images from it are my favorite part of the hobby. I won't fly without it. The camera stays, the FARG goes. I epoxied on conformal guides with JB Weld last night (properly this time).

Loading her up with a 6-grain CTI K711 for a redemption flight tomorrow. Not quite an L805, but still pretty spicy! Stay tuned for epic video...
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The stills you posted are great – the quality is very good, and they clearly show what happened. My goal in trying out FARGs was to avoid having to use a tower when flying smaller MD rockets where rail guides do have a negative impact. That’s why I was surprised at the use of a FARG in this instance.

If anything, you’ve inspired me that I finally need to buy a camera and try it out. Your comment about adjusting the settings was very helpful, I’ll be sure to try that out.


Tony
 
Thanks, Justin.

Your pictures are similar to the others I have received. In Super-roc competition, the FARGs are mounted above the fins and the FARG has time to open and clear the fins before a strike can happen. Mounting the FARG, so that it rests on the fins, results in the FARG sliding down the fin(s) opposite the rail.

The still pictures and video evidence, I've received, predicts a high probability of a fin strike from a FARG. I still need to determine how a fin strike affects a rocket in flight. On low <5 T/W ratio rockets, FARG fin strikes result in a high probability of a flight path deviation. T/W ratios between 8-35, I see little visual evidence of flight deviations from FARG strikes. This area will require flight instrumentation to determine any effect. The two flights with T/W ratios >75 resulted in total destruction of the FARG.
 
Spacedog49Krell said:
Thanks, Justin.

Your pictures are similar to the others I have received. In Super-roc competition, the FARGs are mounted above the fins and the FARG has time to open and clear the fins before a strike can happen. Mounting the FARG, so that it rests on the fins, results in the FARG sliding down the fin(s) opposite the rail.

The still pictures and video evidence, I've received, predicts a high probability of a fin strike from a FARG. I still need to determine how a fin strike affects a rocket in flight. On low <5 T/W ratio rockets, FARG fin strikes result in a high probability of a flight path deviation. T/W ratios between 8-35, I see little visual evidence of flight deviations from FARG strikes. This area will require flight instrumentation to determine any effect. The two flights with T/W ratios >75 resulted in total destruction of the FARG.
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unless they have changed greatly most of the Super-Roc FARGs are lightly built units, not the heavy units we are seeing most of these pics. I have a set of FARGS similar to the OP's and a set I downloaded and printed myself neither are very lightweight nor do they snap open as quickly as the ones I have seen laser cut from plywood and used in model rocket competition (those almost jump off the rocket when they open). I believe you are correct that high acceleration has a lot to do with placement, really there is probably a point of X number of G's where a FARG should be abandoned in favor of a tower simply because its not going to stay put on the airframe or open fast enough if it does.
 
rharshberger said:
unless they have changed greatly most of the Super-Roc FARGs are lightly built units, not the heavy units we are seeing most of these pics. I have a set of FARGS similar to the OP's and a set I downloaded and printed myself neither are very lightweight nor do they snap open as quickly as the ones I have seen laser cut from plywood and used in model rocket competition (those almost jump off the rocket when they open). I believe you are correct that high acceleration has a lot to do with placement, really there is probably a point of X number of G's where a FARG should be abandoned in favor of a tower simply because its not going to stay put on the airframe or open fast enough if it does.
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Thanks for your input. When I built my first 400Hz flight computer, I was interested in motor and flight performance details. What I discovered was that most of the interesting data occurs during the 250ms - 500ms after ignition. The dynamics of a "rod" launch are very unique compared to tower or rail launches. Now, I'm studying FARG strikes.
 

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