uncle_vanya
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I listened to a little voice in my head and allowed a J420R to be used in my Funnel Roc'. The rocket was/is a skirt fin design using an automotive funnel as the only fin. The design is a modification from a design I found on EMRR.
The rocket simulates as stable in a couple of different programs - it's over 5' long with the nose. I used a modified Big Daddy nose with a ton of weight and foam the nose weighed about 1.5 LBS! In any case, it seemed stable and had flown on a couple of different motors in the H range. That's when I got cocky...
I was not originally planning to try for L2 yesterday - but the wind appeared to have died down and the conditions just looked good. Our field is a bit tricky to recovery single deployment from higher than 2500' so I was pushing things - but the 5 lb rocket was very draggy and I figured it would be ok in that respect.
The rocket took off beautifully. There was no room for a rail button system due to the funnel but I had conformal lugs sized for a 1/2 rod. No rod whip was observed - the rocket seemed to be headed for a great flight. A beautiful bright red flame was shooting out of the rocket which was aesthetically pleasing given the white and red rocket. Seemed to be ok...
About 100 or so feet in the air the rocket turned 90 degrees - now it was a cruise missile. It was still under power - and still flying straight after that quick left hand turn. The rocket made a beeline for the treeline - which was of course the narrow dimension of our field.
People with better eyes that I have said that they saw it pop the 'chute just beyond the trees - in another field - so I might recover it. The impending thunderstorm made this into a race against the weather and time as it was also getting late in the day and the light was likely to fade quickly.
To make a long story a bit shorter - I found the rocket. I first spotted the 'chute (one of PlasticPaul's - sorry about that loss) hanging in a tree. The nose cone was attached but the rocket was nowhere in sight. The Tree was just short of the barley field I was walking in. The barley was 2' tall - the 3" rocket body would be lost if it were in the field without a 'chute.
I scouted at the edge of the woods and noticed that it was a swamp filled with brambles and mud. Joy. The boots were back at the car. I finally spotted the rocket near the base of the tree - it was "intact" as far as I could tell. Several attempts later I finally found a route that only tore my skin a little and left me with muddy - but not soaked - shoes. I recovered the rocket - it was bent. The paper mailing tube body had dented and warped severely. From the flight pattern and the behavior of the rocket it had to have happened post burn-out.
The rocket motor (38/720) was recovered - which was my main objective.
This next statement is WRONG - I mistakenly saw something that was not there - the loop was folded under and the stray string I saw was a bit of frayed end that I forgot to cut off. I then noticed that the 1500 lb test Kevlar (flat braid) that I use in the main body to anchor back to the motor mount was severed. No burn marks, no fraying - just a fairly clean cut. The loop was intact! I just inspected it again and I feel like a fool! I also noticed that phenolic extension to the rocket (the upper 18 inches of the rocket) was chipped with two round cuts like it had hit a branch. These chipped out semi-circles were sharp.
I'm still trying to think this through. There has to be a clue as to what happened in here somewhere. We had wind gusts from time to time but at the surface they had been in a different direction than this. The rocket was under thrust during the turn and did not go wiggly or out of control at all other than the 90 degree turn - what happened? The kevlar is exceptionally strong - how did it break? It didn't - see above
Ideas?
Oh - and as far as Stability. The programs I have estimate the CP to be down close to or within the Skirt (funnel). The CG was more than 12" forward of this - approximately 20" ahead of this. The 1.5 lb nose really makes a difference.
The rocket simulates as stable in a couple of different programs - it's over 5' long with the nose. I used a modified Big Daddy nose with a ton of weight and foam the nose weighed about 1.5 LBS! In any case, it seemed stable and had flown on a couple of different motors in the H range. That's when I got cocky...
I was not originally planning to try for L2 yesterday - but the wind appeared to have died down and the conditions just looked good. Our field is a bit tricky to recovery single deployment from higher than 2500' so I was pushing things - but the 5 lb rocket was very draggy and I figured it would be ok in that respect.
The rocket took off beautifully. There was no room for a rail button system due to the funnel but I had conformal lugs sized for a 1/2 rod. No rod whip was observed - the rocket seemed to be headed for a great flight. A beautiful bright red flame was shooting out of the rocket which was aesthetically pleasing given the white and red rocket. Seemed to be ok...
About 100 or so feet in the air the rocket turned 90 degrees - now it was a cruise missile. It was still under power - and still flying straight after that quick left hand turn. The rocket made a beeline for the treeline - which was of course the narrow dimension of our field.
People with better eyes that I have said that they saw it pop the 'chute just beyond the trees - in another field - so I might recover it. The impending thunderstorm made this into a race against the weather and time as it was also getting late in the day and the light was likely to fade quickly.
To make a long story a bit shorter - I found the rocket. I first spotted the 'chute (one of PlasticPaul's - sorry about that loss) hanging in a tree. The nose cone was attached but the rocket was nowhere in sight. The Tree was just short of the barley field I was walking in. The barley was 2' tall - the 3" rocket body would be lost if it were in the field without a 'chute.
I scouted at the edge of the woods and noticed that it was a swamp filled with brambles and mud. Joy. The boots were back at the car. I finally spotted the rocket near the base of the tree - it was "intact" as far as I could tell. Several attempts later I finally found a route that only tore my skin a little and left me with muddy - but not soaked - shoes. I recovered the rocket - it was bent. The paper mailing tube body had dented and warped severely. From the flight pattern and the behavior of the rocket it had to have happened post burn-out.
The rocket motor (38/720) was recovered - which was my main objective.
This next statement is WRONG - I mistakenly saw something that was not there - the loop was folded under and the stray string I saw was a bit of frayed end that I forgot to cut off. I then noticed that the 1500 lb test Kevlar (flat braid) that I use in the main body to anchor back to the motor mount was severed. No burn marks, no fraying - just a fairly clean cut. The loop was intact! I just inspected it again and I feel like a fool! I also noticed that phenolic extension to the rocket (the upper 18 inches of the rocket) was chipped with two round cuts like it had hit a branch. These chipped out semi-circles were sharp.
I'm still trying to think this through. There has to be a clue as to what happened in here somewhere. We had wind gusts from time to time but at the surface they had been in a different direction than this. The rocket was under thrust during the turn and did not go wiggly or out of control at all other than the 90 degree turn - what happened? The kevlar is exceptionally strong - how did it break? It didn't - see above
Ideas?
Oh - and as far as Stability. The programs I have estimate the CP to be down close to or within the Skirt (funnel). The CG was more than 12" forward of this - approximately 20" ahead of this. The 1.5 lb nose really makes a difference.
