LOC 4" IRIS question

[scotte]

QQ for those who know this rocket - has anyone had success using a 29mm Loc-n-Ring adapter to fly the LOC 4" IRIS on a G motor? I've seen people here and elsewhere advocate for it as a good L1 cert vehicle, and I'm 95% sold on it. But before I hit the buy button I'd love to have someone give me an assurance that I'll be able to flight test it before the cert attempt. RockSim has it leaving the pad at < 19mph on a G80... this concerns me. But I'm loving the 500' apogee on that motor. Has anyone tried it?

 

[OKTurbo]

This is a big rocket. I can’t imagine any 29mm G being able to fly it.

For the sake of argument let’s do a standard RSO check…. 80 N / 4.45 N/lb = 18 lb
5:1 ‘safe’ thrust to weight. 18/5=3.6lb. If you can get the weight to 3.6lb…..may be ‘ok’ish’

LOC says it weighs 5.5lbs

 

[chrocket]

Me too would not recommend to fly this on a G motor.
Even As OKTurbo wrote it hardly would be on a stable flight and I cannot imagine that you get past RSO check.
Use a nice I motor (I180) and do not worry about the test flight, which would be most probably unssuccessful with a G motor.

 

[Scott_650]

I’m assuming the OP is another pilgrim searching for that illusive “perfect” L1 certification attempt rocket that they can fly afterwards on all kinds of motors. Take this little bit of advice from someone who tried walking that path - it’s not impossible, others have done it, just ask yourself why this is the approach you’ve chosen. I ended up building a heavy, sturdy, draggy rocket for my L1 attempt (worked perfectly!) that was just safely flyable on common SU G motors with an adapter - flew the heck out of it to make sure my techniques were sound, then put it up on a “baby” H for an easy cert flight. Not the only way to go, maybe not the optimal way but it’s the way the very experienced, very senior HPR folks in our club advised me to go.

Ask yourself that “why” question - when you’ve answered it to your satisfaction move on to the “what” - it could save you some frustration. All that universal rocket solution does is…save you from building more than one rocket. What’s the fun in that?

 

[waltr]

Yes, finding a rocket that can fly on G's as Class 1 plus do L1 cert is tough. Most common way is a shortish fat rocket with high drag. I used the LOC 4" Goblin for L1 to 956 feet on an H238. But can still fly it at local field as Class 1 on G's.

I also have the LOC 2.2inch IRIS with DD. It weights about 1200 gram and will fly on an F67 to about 400'. Typically fly on G's to 1200-1400'. This could be flown on a baby H for a L1 cert but expect 2000+ feet.

The 4" IRIS, like chrocket said, needs more ommph off the pad.
Sim show launch weight at 2.6kGram.
As in OKTurbo's calculations, 2.6 * 10 (near 9.8m/s/s) * 5 (5:1TW) = 130N minimum average thrust. Theoretically, A G138 would work but not as Class 1 or without an L1 Cert.

 

[scotte]

I’m assuming the OP is another pilgrim searching for that illusive “perfect” L1 certification attempt rocket that they can fly afterwards on all kinds of motors. Take this little bit of advice from someone who tried walking that path - it’s not impossible, others have done it, just ask yourself why this is the approach you’ve chosen. I ended up building a heavy, sturdy, draggy rocket for my L1 attempt (worked perfectly!) that was just safely flyable on common SU G motors with an adapter - flew the heck out of it to make sure my techniques were sound, then put it up on a “baby” H for an easy cert flight. Not the only way to go, maybe not the optimal way but it’s the way the very experienced, very senior HPR folks in our club advised me to go.

Ask yourself that “why” question - when you’ve answered it to your satisfaction move on to the “what” - it could save you some frustration. All that universal rocket solution does is…save you from building more than one rocket. What’s the fun in that?

My fellow Scott,

You assume wrong My actual goal is to do exactly what you did - fly my L1 on a rocket that will barely support a G for a test flight, and then be low and slow for the cert flight. I came to this approach through the advice I've read given to others here and on other forums, and in conversations with the folks at the club. This is why I came with a specific rocket / motor question and not another "new to rocketry - what rocket can I use to cert L1 / L2 on the same day next weekend?" I want both my L1 and L2 rockets to be very simple, and fly the minimum qualifying motor to a nice, low apogee and safe recovery. C's get degrees. I want to bore the hell out of myself on the cert flights. What motor I buy from the on-site vendor and load into the same rocket 5 minutes later? Beyond that I want the rocket to be extensible to support future learning initiatives prior to planning whatever my L2 rocket is - this is where the IRIS appealed to me. But it's just too heavy to meet my need. Thank you all for making that very clear to me and also showing your work - I've learned here.

BTW - this is also why I'm not doing a self-design for my cert flights. I'll take a proven platform for the certs and leave the complex learnings for the in-between times. Literally the only reason I care about certs is because they are the gatekeepers to what I really want - flexible thrust options.

One more "BTW" - when I first started back on this rocketry journey I was sold an Apogee Peregrine by a very kind, certified flier at the Apogee office. I was told that it would be a great platform for L1 so long as you modify it do not do DD, and then you can fly it for L2 also. Reading through this forum has shown me that for many reasons, that rocket is a poor choice for L1 certification and I wouldn't fly it for L2 either. Moral of the story is "DYOR before you pull out your credit card"

Thanks again to all of you!

Scott

 

[scotte]

This is a big rocket. I can’t imagine any 29mm G being able to fly it.

For the sake of argument let’s do a standard RSO check…. 80 N / 4.45 N/lb = 18 lb
5:1 ‘safe’ thrust to weight. 18/5=3.6lb. If you can get the weight to 3.6lb…..may be ‘ok’ish’

LOC says it weighs 5.5lbs

Me too would not recommend to fly this on a G motor.
Even As OKTurbo wrote it hardly would be on a stable flight and I cannot imagine that you get past RSO check.
Use a nice I motor (I180) and do not worry about the test flight, which would be most probably unssuccessful with a G motor

Yes, finding a rocket that can fly on G's as Class 1 plus do L1 cert is tough. Most common way is a shortish fat rocket with high drag. I used the LOC 4" Goblin for L1 to 956 feet on an H238. But can still fly it at local field as Class 1 on G's.

I also have the LOC 2.2inch IRIS with DD. It weights about 1200 gram and will fly on an F67 to about 400'. Typically fly on G's to 1200-1400'. This could be flown on a baby H for a L1 cert but expect 2000+ feet.

The 4" IRIS, like chrocket said, needs more ommph off the pad.
Sim show launch weight at 2.6kGram.
As in OKTurbo's calculations, 2.6 * 10 (near 9.8m/s/s) * 5 (5:1TW) = 130N minimum average thrust. Theoretically, A G138 would work but not as Class 1 or without an L1 Cert.

Thanks to all of you. I won't go this route. Going back to the lab, loaded more knowledge.

 

[thzero]

Yes, finding a rocket that can fly on G's as Class 1 plus do L1 cert is tough. Most common way is a shortish fat rocket with high drag. I used the LOC 4" Goblin for L1 to 956 feet on an H238. But can still fly it at local field as Class 1 on G's.

I also have the LOC 2.2inch IRIS with DD. It weights about 1200 gram and will fly on an F67 to about 400'. Typically fly on G's to 1200-1400'. This could be flown on a baby H for a L1 cert but expect 2000+ feet.

My L1 would happily fly on Gs as well as Hs. Its 2.6" fiberglass tube and fins, but with an Aerotech 2.6" nosecone (from crashed Aerotech Initiator that I rebuilt), but to save weight it has 29mm LOC motor mount and plywood rings. Did well with a H180 for the L1 flight; was about 2400'. G79 goes about 900' with 50fps off a 72" rail. Sure a pure LOC build around 2.6" would work well with Gs and baby Hs; but probably bit more towards 3000' feet.

 

[Scott_650]

My fellow Scott,

You assume wrong My actual goal is to do exactly what you did - fly my L1 on a rocket that will barely support a G for a test flight, and then be low and slow for the cert flight. I came to this approach through the advice I've read given to others here and on other forums, and in conversations with the folks at the club. This is why I came with a specific rocket / motor question and not another "new to rocketry - what rocket can I use to cert L1 / L2 on the same day next weekend?" I want both my L1 and L2 rockets to be very simple, and fly the minimum qualifying motor to a nice, low apogee and safe recovery. C's get degrees. I want to bore the hell out of myself on the cert flights. What motor I buy from the on-site vendor and load into the same rocket 5 minutes later?

No worries about being wrong - I’ve been married for nearly 40 years

My L1 rocket is a Discount Rocketry 4” Crayon rocket that I slightly modded to allow adding/removing additional nose weight - very easy mod with the way the nose cone bulkhead clamps in place. That kit is OOP but they still sell the fins and rings, 38mm motor tube, recovery gear and hardware to use your own Fantazia brand crayon bank (if you can find one). I liked it so much that it was rebuilt from a new bank after an awesome CATO. I fly it at nearly every club launch sans the added weight on an adapted G motor.

Sounds like you have a good idea of what you’re trying to achieve - knowing why (so you can have fun with what I think could be the next big thing in hobby rocketry since DD - thrust vectoring - explains it well).

Good luck and post updates as you go!

 

[cls]

My L1 rocket is a Discount Rocketry 4” Crayon rocket

Yay! My L1 was a crayon too, a blue one. Rather than add nose weight, I built it light with all 1/8" plywood rings and fins. Has baffle holes in the top MMT plate, and vents in top of the over long MMT.

Flies ok on F40s, very nicely on Gs, and H97s... And H180s and H165s too.

 

[Tim51]

FWIW: I built a Loc Fantom 438 for my L1, and I bought two 38mm motors - a CTI G115 WT for a putative test / shake down flight and a CTI H125 for the actual L1 cert.

But on the day of the cert I asked myself 'why a shakedown flight?'. I decided that since my L1 was a simple pop and drop motor eject set up, flying to under 2K', with no tracker, the test flight would not really prove/test anything, except maybe risk damaging the rocket in some way before the actual cert attempt. So I flew the H first, passed the L1 cert, then flew the G115 afterwards, as a celebratory 'victory lap'.

My other observation would be about ensuring you fly something unlikely to sustain damage. The LOC Iris looks a great kit, but fins are bigger than necessary, and draggy. On my Fantom, I replaced the stock clipped delta fins with trapezoidal ones, to reduce the risk of any damage if say, you hit a rock at touchdown. Hard ground can be unforgiving, even when your chute seems to be the right size.

YMMV of course. Good luck with your build and your L1 certification.

 

[scotte]

No worries about being wrong - I’ve been married for nearly 40 years

My L1 rocket is a Discount Rocketry 4” Crayon rocket that I slightly modded to allow adding/removing additional nose weight - very easy mod with the way the nose cone bulkhead clamps in place. That kit is OOP but they still sell the fins and rings, 38mm motor tube, recovery gear and hardware to use your own Fantazia brand crayon bank (if you can find one). I liked it so much that it was rebuilt from a new bank after an awesome CATO. I fly it at nearly every club launch sans the added weight on an adapted G motor.

Sounds like you have a good idea of what you’re trying to achieve - knowing why (so you can have fun with what I think could be the next big thing in hobby rocketry since DD - thrust vectoring - explains it well).

Good luck and post updates as you go!

I just looked up that crayon kit. So awesome! I might chase that down outside of the certification realm.

Automating flight controls using sensors and programmable microcontrollers during all phases of flight is my ultimate goal. Thrust vectoring is definitely gonna be huge as the tech is made safer and more accessible. Exciting times ahead!

 

[scotte]

FWIW: I built a Loc Fantom 438 for my L1, and I bought two 38mm motors - a CTI G115 WT for a putative test / shake down flight and a CTI H125 for the actual L1 cert.

But on the day of the cert I asked myself 'why a shakedown flight?'. I decided that since my L1 was a simple pop and drop motor eject set up, flying to under 2K', with no tracker, the test flight would not really prove/test anything, except maybe risk damaging the rocket in some way before the actual cert attempt. So I flew the H first, passed the L1 cert, then flew the G115 afterwards, as a celebratory 'victory lap'.

My other observation would be about ensuring you fly something unlikely to sustain damage. The LOC Iris looks a great kit, but fins are bigger than necessary, and draggy. On my Fantom, I replaced the stock clipped delta fins with trapezoidal ones, to reduce the risk of any damage if say, you hit a rock at touchdown. Hard ground can be unforgiving, even when your chute seems to be the right size.

YMMV of course. Good luck with your build and your L1 certification.

Thanks Tim. This thread made me realize that I was overthinking things. If my goal really is to make the cert flights as boring as possible, then I should just get a rocket that’s been a proven winner consistently over time. So I ordered a LOC IV. No flair, just a proven cert flyer. $100, quick build, good enough motor range to support my need for a test flight. It’s a no brainer. It should be here in a couple of days.

As for whether to risk a test flight, my take is that I’d rather work out the bugs behind the scenes. If it’s gonna break on the test flight then it would have broken on the cert flight. But as you said, ymmv, and so long as safety isn’t compromised I’m great with either approach. I’m a little bit type-A, so I’m gonna do a test run.

Thanks a ton for the input! The fin issue is huge and is something I’ll be paying attention to even on the LOC IV. It’s one of several reasons my Peregrine is sitting on a shelf in a bag.

 

[T-Rex]

LOC IV should work well. Mine was a Madcow 4" Little John on an AT H238T to about 1500ft. No test flight, just went for it.
Good Luck!!

 

[waltr]

A LOC IV is a good L1 rocket.
After you have L1 and want to start experimenting for electronics (I have a 10DOF board I have been flying to learn with), add a payload bay. Easy to do with a LOC BT and Coupler. The LOC IV is short so adding length is easy and will still fly well.