Minimum Diameter for L2 cert?!?

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Andrew_ASC

Andrew_ASC

UTC SEDS 2017 3rd/ SEDS 2018 1st
Joined
Sep 22, 2017
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Well I’ve already trashed the finspan on a Sandhawk kit today trying to cram J and K motors into it without flutter. Created pad wandering and coning issues noted by Jim and Eric. I don’t see how I can come up with worse ideas. Then again the day isn’t over.

Opinions!?!? I’m thinking eject a streamer at Apogee and then a main at lower alt on a min diameter. Toying with the idea of a Blackhawk 38 on a J-350 or J-500G. A rough sim looks like 10,000 ft is possible. As far as trackers I have a Telemini and TeleGPS. Might be one helluva walk to retrieve it. And one heck of a road trip to fly it. But hey L2 is a journey right?

Trying to back down from go itis.
 
I like reading your posts to see what your coming up with next. Don't ever stop coming up with new ideas. Some will work out some may not. That's just how life goes.

Go for it
 
Already flew one multistage L-1 named crispy boy this year. It only went M1.69 and 11,563ft for uni. Granted we were noobs and Apogee deployed it so it drifted 1.4 Miles into a swamp. So that hard lesson out of the way, I think dual deploy is a must do... other posters have said do not deploy a chute that high it’ll drift. And I’m not going back to Florida for HPR launches. Screw swamps.
 
crossfire said:
I like reading your posts to see what your coming up with next. Don't ever stop coming up with new ideas. Some will work out some may not. That's just how life goes.

Go for it
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I agree with this, but I would urge that you gain more experience on some of the basics before going for the gusto. You have improved greatly (I see it in your fillets) but some empirical knowledge gained doing less stressful attempts might give you stamina.
 
Andrew_ASC said:
Well I’ve already trashed the finspan on a Sandhawk kit today trying to cram J and K motors into it without flutter. Created pad wandering and coning issues noted by Jim and Eric. I don’t see how I can come up with worse ideas. Then again the day isn’t over.

Opinions!?!? I’m thinking eject a streamer at Apogee and then a main at lower alt on a min diameter. Toying with the idea of a Blackhawk 38 on a J-350 or J-500G. A rough sim looks like 10,000 ft is possible. As far as trackers I have a Telemini and TeleGPS. Might be one helluva walk to retrieve it. And one heck of a road trip to fly it. But hey L2 is a journey right?

Trying to back down from go itis.
Click to expand...


I would call Tim , order some new fins , the build the sandhawk properly . Here is my .169 scale Terrier Sandhawk. If it is of any interest to you , I will do a quick build thread. The booster is 3 inch with a 54mm mount for a K1100 , the sandhawk is 2 inch with a 38mm mount for a J350 . 7.5 pounds on the pad.
 

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The Terrier Sandhawk idea is cool. If you post a thread I’ll take a look. I’ve played with multistage MD for uni. I think I’d just wind up ripping the fins off the Sandhawk.

I mean I already got a 3D file of a sub min 38mm around a K1127... As far as Gusto I’m definitely not starting the BH38 on a k1127.
 
F2C3E3CE-9F83-4497-B2E4-631AD916739D.jpeg 6461901D-AC1B-4811-8376-2CA44AD8E38E.jpeg
This is the flutter data on the BH38. This is what’s driving my decision here. I can put anything from an H to a K into it and not break it in a sim first.
 
Other choices are GoDevil, Mongoose 38, or scratchbuild. To be honest I’m liking the BH38 because it’s RF transparent.
 
Choose what you would like to build and fly, it is your certification flight. Make sure you confirm with your TAPs that it is acceptable. Some will not sign off if they don't see the deployment, regardless of what data might be available.
 
#1 and most important: cert the way you want to cert. do what makes you happy.

#2 since you asked for advice: L2 on the Sandhawk with replaced fins is a far lower risk venture than a MD J. I flew a 2.6” Madcow Arcas on a baby J and it only has 1/16” fins. Just don’t stuff a Warp 9 or Super Thunder in it on your first flight and you’ll be fine. I’d target 8G or so on liftoff and call it good.

MD will be spectacular if it works. If it doesn’t it’ll go out in a blaze of glory but you won’t get your cert.

FWIW, YMMV, etc.
 
I did L2 with a PML Patriot kit that came with a 29mm mount. I used a 98mm K125 so the fins were glued in slots flush inside. The fins were not modified so they came out straight for a little more than an inch then swept back. Nose ballast was epoxy and Black Rock dust. Was all built on site.
I had to launch that day as it was the first day doing L2 certs, I didn't want to be one of the chumps certing after that day. : )

How did we ever launch anything without computer simulations and flutter analysis?
 
Personally I would do a 38mm motor in a 54mm body. That gives you a lot more room for electronics and recovery. A 54mm rocket is just a handy size. I'm in the process of rebuilding the red rocket in my avatar. It's been a test bed for all sorts of recovery schemes but it's going back to a traditional dual deploy. That little paper rocket has cleared 7K on a small J. I plan to push it higher at LDRS this coming year.
 
I picked up a BH 38, the fins are thick, and it's going to be a "heavy" bird, ~32oz with GPS and DD alt, recovery gear etc.

As for the L2 certification do what you want for the attempt. Quality build practices, sound electronics setup, proficient at prepping the rocket for DD flight, passing the test, ground testing, video and pics, these are things I thought a lot about.

I flew my MC SDX3 on a Loki J320r motor to 4000', just in eye sight, rso had eyes on apogee event with binoculars, and was good test for myself of what I have learned in HPR over the last year+ going L1, and L2.

Now that I have the cert I can grow into the larger L2 motors.

Like most things in life its a jouney, not a destination.

~John
 
Doing initial costs analysis it’s looking like it’ll take $373 to complete L2 38mm MD project. (BH38 Airframe, magnetic switch, J motor with hazmat shipping, MJG firewires, and FARG.)

Already have 38-720 casing, hardware, and Altus metrum electronics. With either Sandhawk or MD build I’m risking $364 of Altus electronics unless I change my game plan.

I could step it up to a 54mm MD and an L1000DMS, but at this point I don’t feel comfortable flying something that high performance and cost wise it’s more. That seems to invite trouble.

The 38mm J in MD gives me something I can cut my teeth on and learn cheaper that scales up tactic wise. I’m more familiar with smaller diameter MD builds because of the SEDS multistage experiences. 29-38mm... The biggest difference is change from apogee deploy to dual deploy on main.

I’ve been messing with the electronics setup and programming on the bench lately.
I’ve set Apogee lockouts to 10s on Telemini with the main firing at 300m. The apogee channel should auto detect highest alt then fire. I’m comfortable running the TeleGPS and Telemini on separate channels. I can swap frequency at ground station in real time and receive data for either device at base. This gives the tracking an RDF backup to GPS. The coolest thing is I can verify if altimeter/gps is on through the laptop before the RSO fires the rocket off.

Biggest fear is the main not deploying by altimeter and losing a lot of electronics. I guess I should take the plunge and trust the electronics. Second fear is a TAP not approving the flight so I guess I better ask around first before spending the time and money on this path. It will go beyond visual. And they may not like that.

In either case I really need to ground test the altimeters with a vacuum cleaner to get it to fire the pyro charges and test recovery gear on ground. Size holes, size charges, ground test, and test more. Then develop a checklist would be a good idea.

Right now the hold up is my parents want me to get an engineering job before I buy anymore rocket stuff for 2019. Dad wants to see this L2 cert attempt, we’re both excited about the min diameter. It’s killing me I have about $881 right now but not permission yet. Anyways just mulling it over and rambling more.

It may not be the cheapest or least risk way to do an L2 but I sure feel excited for it.
 
Andrew_ASC said:
Doing initial costs analysis it’s looking like it’ll take $373 to complete L2 38mm MD project. (BH38 Airframe, magnetic switch, J motor with hazmat shipping, MJG firewires, and FARG.)

Already have 38-720 casing, hardware, and Altus metrum electronics. With either Sandhawk or MD build I’m risking $364 of Altus electronics unless I change my game plan.

I could step it up to a 54mm MD and an L1000DMS, but at this point I don’t feel comfortable flying something that high performance and cost wise it’s more. That seems to invite trouble.

The 38mm J in MD gives me something I can cut my teeth on and learn cheaper that scales up tactic wise. I’m more familiar with smaller diameter MD builds because of the SEDS multistage experiences. 29-38mm... The biggest difference is change from apogee deploy to dual deploy on main.

I’ve been messing with the electronics setup and programming on the bench lately.
I’ve set Apogee lockouts to 10s on Telemini with the main firing at 300m. The apogee channel should auto detect highest alt then fire. I’m comfortable running the TeleGPS and Telemini on separate channels. I can swap frequency at ground station in real time and receive data for either device at base. This gives the tracking an RDF backup to GPS. The coolest thing is I can verify if altimeter/gps is on through the laptop before the RSO fires the rocket off.

Biggest fear is the main not deploying by altimeter and losing a lot of electronics. I guess I should take the plunge and trust the electronics. Second fear is a TAP not approving the flight so I guess I better ask around first before spending the time and money on this path. It will go beyond visual. And they may not like that.

In either case I really need to ground test the altimeters with a vacuum cleaner to get it to fire the pyro charges and test recovery gear on ground. Size holes, size charges, ground test, and test more. Then develop a checklist would be a good idea.

Right now the hold up is my parents want me to get an engineering job before I buy anymore rocket stuff for 2019. Dad wants to see this L2 cert attempt, we’re both excited about the min diameter. It’s killing me I have about $881 right now but not permission yet. Anyways just mulling it over and rambling more.

It may not be the cheapest or least risk way to do an L2 but I sure feel excited for it.
Click to expand...

Concentrate on getting the job. That’s the real certification.
 
Job means more money for rocket stuff. You have a L1 so play there until you need the L2. Tons of fun you can have with H's and I's.
 
Thanks guys, I may be starting at VW Chattanooga next week as an engineering intern again pending an interview. They canceled the interview today and rescheduled it to next week. The internship could lead to full time employment since I have a diploma now based on company needs and my performance.

In the meantime I ordered 3x H130W’s.

Leaning towards a Wildman BH38 or a mac Hyper54 MD for L2 pending internship.
 
You graduated, right? An internship sounds like a bad deal. Is it more of a probationary engineering job (paid & full time with benefits, but a "we can fire you for any reason" period)? If it's unpaid, run very far away. Either way if it's called an internship, keep looking for a full time job. Be humble, but don't settle either.
 
It’s the back door entry into the car factory. Two of my friends got hired on full time last time I did the internship as an undergrad. Yes I graduated. It’ll pay about $5.5k/mo. The graduation status was why I wasn’t hired full time the first round.
 
GrouchoDuke said:
You graduated, right? An internship sounds like a bad deal. Is it more of a probationary engineering job (paid & full time with benefits, but a "we can fire you for any reason" period)? If it's unpaid, run very far away. Either way if it's called an internship, keep looking for a full time job. Be humble, but don't settle either.
Click to expand...

In my full-time job, they no longer hire any entry level position directly. Lab or engineering. Everything goes through temp agencies and internships first. And -everything- is ‘we can fire you for any reason‘. Even after 10-20 years. That’s what ‘at will’ and ‘right to work’ mean.
 
I emailed HARA for clarification if a MD cert L2 is acceptable or practical. The BH38 idea on a J350W pushes 10.7k ft which is awfully damn close to their 10.8k ft hard deck. The Hyper54 on a j-250 DMS pushes 7k ft but has metal fins. Also asked if it’s okay for rocket to go beyond visual sight for a certification. I mean there’s no alt limit stated in a cert so I would like to push something beyond visual as long as they are comfortable with signing off on that. Of course obeying the FAA waiver and RSO hard deck below waiver. What ponders me is lateral drift area and the Max height flown at that field.
 
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Charles_McG said:
In my full-time job, they no longer hire any entry level position directly. Lab or engineering. Everything goes through temp agencies and internships first.
Click to expand...
I guess that’s one way to skin the cat. Hopefully they’re not unpaid internships that seem to plaque some industries.
 
Andrew_ASC said:
I emailed HARA for clarification if a MD cert L2 is acceptable or practical. The BH38 idea on a J350W pushes 10.7k ft which is awfully damn close to their 10.8k ft hard deck. The Hyper54 on a j-250 DMS pushes 7k ft but has metal fins. Also asked if it’s okay for rocket to go beyond visual sight for a certification. I mean there’s no alt limit stated in a cert so I would like to push something beyond visual as long as they are comfortable with signing off on that. Of course obeying the FAA waiver and RSO hard deck below waiver. What ponders me is lateral drift area and the Max height flown at that field.
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Personally if it was me RSOing, when flying close to waiver I'd rather you have a previous flight on a smaller motor with the airframe to prove the simulation data accurate. I learned this hard way before when I screwed this up trusting a simulation for altitude without getting a flight on the airframe on a smaller motor. Good luck on the high flying lvl 2 flight, I finally decided to step up and do a min diameter for my level 3 flight. Figured if I'm going to partake in the hobby I might as well do what I can to get the most out of it for myself.
 
Flying within 1% of the max allowable altitude is risky.

In addition to possible simulation errors, there are individual motor variations. You could test the sim altitude with an I motor that happened to be from a wimpy manufactured batch and think you are safe to fly that J350W. Then you get a J350 that happens to have 5% more thrust than what was certified, and you can easily bust the waiver.

I often get altimeter readings that are 15% off from the simulated apogee. Humidity, winds aloft, motor variations, sim errors all probably play a part.

It’s ultimately up to your RSO and whoever signs off your L2, but if you are using an altimeter deploy, you could get asked for the apogee reading, and pay the price if you bust the waiver.
 
Andrew_ASC said:
I emailed HARA for clarification if a MD cert L2 is acceptable or practical. The BH38 idea on a J350W pushes 10.7k ft which is awfully damn close to their 10.8k ft hard deck. The Hyper54 on a j-250 DMS pushes 7k ft but has metal fins. Also asked if it’s okay for rocket to go beyond visual sight for a certification. I mean there’s no alt limit stated in a cert so I would like to push something beyond visual as long as they are comfortable with signing off on that. Of course obeying the FAA waiver and RSO hard deck below waiver. What ponders me is lateral drift area and the Max height flown at that field.
Click to expand...

I can tell you that HARA will have no interest in someone with limited practical experience and questionable judgement wanting to take chances with their waiver or surrounding landowner relationships. No club would, but especially in the Southeastern United States where finding and keeping good launch sites is a huge challenge. I would recommend flying quite a few more flights on H and I motors for you, Andrew.
 

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