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

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Porkchap

Porkchap

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Drove over 700 miles to get to a high enough waiver to fly my MAC Performance Hyper54 to about 17,000' on a CTI L805. The rocket severely corkscrewed for most of the boost phase when the guide hung on for a couple seconds. Still made it to 13,413 feet and recovered with no damage. Very disappointed, though.

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Porkchap said:
Drove over 700 miles to get to a high enough waiver to fly my MAC Performance Hyper54 to about 17,000' on a CTI L805. The rocket severely corkscrewed for most of the boost phase when the guide hung on for a couple seconds. Still made it to 13,413 feet and recovered with no damage. Very disappointed, though.

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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. Best to put these as low as possible.

Agree with @Buckeye, if its a full send flight, best to use a tower.

Sorry to see that...
 
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.
 
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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That might improve it, but it might also make it less stiff and less reliable.
 
I'm starting to see that rocket "science" is also about 50% luck. Things can go wrong no matter how much prep you put into it. And even the commercial aerospace folks have problems, and when those happen, someone's multi-million dollar satellite burns up while still connected to stage 2. You simply cannot account for everything, and that's a reality that will continue to bug you for life.
 
Porkchap said:
Drove over 700 miles to get to a high enough waiver to fly my MAC Performance Hyper54 to about 17,000' on a CTI L805. The rocket severely corkscrewed for most of the boost phase when the guide hung on for a couple seconds. Still made it to 13,413 feet and recovered with no damage. Very disappointed, though.

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In my opinion, Flyaway rail guides are an unhappy medium between a rail and a tower.

If absolute maximum performance isn't a major concern, the drag impact of rail buttons or guides is relatively minimal. Just use them. Even Kip Daugirdas used normal rail buttons for his flight to ~290,000 feet.

If you are going for absolute maximum performance, then a tower is absolutely the way to go.
 
I first noticed this issue a few years ago, when a friend's experimental rocket fin sliced through his fly-away-guide. Since then, I have been studying fly-away fin strikes, which I find are a very common occurrence when the guide is <24 inches above the fins.
 
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.
 
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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Apogee has them
https://www.apogeerockets.com/Build.../Rail_Buttons/Standard_Airfoiled_Rail_Buttons
 
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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Something like these:

https://www.apogeerockets.com/Build.../Rail_Buttons/Standard_Airfoiled_Rail_Buttons
 
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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I have to imagine that was Teddy from Onebadhawk. He has been carrying airfoil buttons for a while now.

When I use rail buttons, I have pretty much exclusively shifted to airfoils. I especially like the Unistrut airfoils - they are beefier than the round ones and hold up a 100+ rocket nicely.

Apogee does have them.

Personally, I like the ones from SCP: https://scpconcepts.com/rocketry/airfoil-rail-guides/

Scott at SCP has made the Unistrut ones in the past and I believe Kenny from Performance Hobbies had some of the SCP Unistruts on hand last time I talked to him.

Teddy's airfoils are interesting because they are a two piece design: http://onebadhawk.com/onebadhawk-airfoiled-rail-guides.html

I have seen others around, but those are vendors I trust and I have used their airfoils.
 
As far as fly-aways go, I own all the sizes of the Additive Aerospace guides and, if you are going to use them, they are about the best I have found.

It is important to fit them properly to your rocket. First you need to get the cork spacers right. If they are too loose, you could damage your fins. If they are too tight, the mechanism may bind.

I also test the release on a rocket before I fly it. I have found it useful to sand/file in between the plastic blocks that hold the rail buttons. When they close together, if they are too tight, they can bind.

I do like to place them right on top of the fins in order to minimize the likelihood of the rocket sliding through the guide and then the fins slamming into it.

Generally, I use fly-aways on lighter rockets that I am not worried about performance or flying it with a super fast burning sledge hammer of a motor. If I am going to fly a LOC IV with an H motor, fly-aways make a lot of sense to me. Basically, I have become lazy and don't want to deal with installing rail buttons on rockets I am just bringing to a launch to have some lower altitude fun :) .
 
mtnmanak said:
I have to imagine that was Teddy from Onebadhawk. He has been carrying airfoil buttons for a while now.

When I use rail buttons, I have pretty much exclusively shifted to airfoils. I especially like the Unistrut airfoils - they are beefier than the round ones and hold up a 100+ rocket nicely.

Apogee does have them.

Personally, I like the ones from SCP: https://scpconcepts.com/rocketry/airfoil-rail-guides/

Scott at SCP has made the Unistrut ones in the past and I believe Kenny from Performance Hobbies had some of the SCP Unistruts on hand last time I talked to him.

Teddy's airfoils are interesting because they are a two piece design: http://onebadhawk.com/onebadhawk-airfoiled-rail-guides.html

I have seen others around, but those are vendors I trust and I have used their airfoils.
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I am almost certain Teddy and Apogee are selling the ones made by SCP.
 
cwbullet said:
I am almost certain Teddy and Apogee are selling the ones made by SCP.
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I am not sure about Teddy... If you look at them (I have some, I can take some better pictures than the ones on his site), you can see they are a two piece design. The ones from SCP are CNCed from a single piece of Delrin. The plastic on the ones Teddy has feels lighter. I have used them, though, and they work well.
 
Buckeye said:
Such as?
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One has been listed above. You have to be as far down the rocket as possible. It must grip the rocket tightly when it is closed. Lastly, it has to release energetically where the rail is removed. The successful flight I have seen all had the guide push away from the rocket.

I have seen quite a few flights that are successful. I have seen a smaller number of failed flights. Almost all of the failed flight failed to clear the rocket or broke during boost up the rail.
 
techrat said:
I'm starting to see that rocket "science" is also about 50% luck. Things can go wrong no matter how much prep you put into it. And even the commercial aerospace folks have problems, and when those happen, someone's multi-million dollar satellite burns up while still connected to stage 2. You simply cannot account for everything, and that's a reality that will continue to bug you for life.
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I've seen hi power flights with buttons take the rail up with them....
 
I've had good luck with the smaller ones (54mm or less) with motors that aren't too punchy. Double up on the the rubber bands to ensure that it pops off quickly. With larger rockets and/or bigger motors, they seem very prone to breaking... I've had them break on the first flight. My favorite was the GLR Firestorm on a K2045... the rail guide pretty much disintegrated right after it left the rail. The only intact rail guide that I have left now is a 29mm.
 
Spacedog49Krell said:
I first noticed this issue a few years ago, when a friend's experimental rocket fin sliced through his fly-away-guide. Since then, I have been studying fly-away fin strikes, which I find are a very common occurrence when the guide is <24 inches above the fins.
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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?
 
One of the keys to a FARG is to make sure its sitting against the fins from the beginning as there is no amount of "grip" that will release later that will keep one from slipping rearward as the rocket accelerates which then slams it into the fins. BTDTGTTS...
 
I have a hypothesis that the angle of the fins' LE is a big factor in the success of a lot of FARGs. I have messed with the foam-sheet KISS-FALL discussed in its own thread on this forum. The LE of the fins on the rocket was swept considerably less than 45 degrees behind perpendicular and the guide hung on each of several flights. First time, shed a fin and crashed the rocket. Second time, it hung on the fins and caused a slow, spiraling boost to a low altitude like in this thread. Barely ejected the streamer before it hit the ground.

That rocket was hammered enough I tossed it in the trash, but will try that design again later with a tower. I will probably try the FALL again on a rocket with a lot more sweep on the fins (probably something Little John-like) to see if it drops the FALL or at least lets it slip off the fins cleanly.
 
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 drag
 

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