Won Too Free

Greetings!

I just happened across a Polecat 10" goblin, and grabbed it up hoping to ( eventually ) do my L1, L2, and L3 certs on the same airframe. I understand that at I-class I'll need to make sure I've got enough oomph off the pad; and that at M-class I'll want to make sure I don't rip the fins off. Given all that, and with the idea of minimizing purchase of motor adapters and/or motor casings:

• What I-class motors would you recommend?
• What L2 motors would you recommend?
• What M-class motors would you recommend?

Thus far ( and looking into the future ), it seems as if I could do I-class and L2 in the same 54mm adapter. Is it possible to do these in the same motor casing? If so, keeping the overall plan limited to two adapters with their appropriate casings and reloads seems like a good plan.

Regards,
-dh.

PS: Off to keep researching Someday Electronics.

Welcome DH!

Take a look over at Thrustcurve.org. There you can enter some basic parms (diameter, length, weight), and you'll see how various motors will perform. It will get you in the neighborhood. Actual sims on other software will refine the numbers even more.

dhbarr said:

Greetings!

I just happened across a Polecat 10" goblin, and grabbed it up hoping to ( eventually ) do my L1, L2, and L3 certs on the same airframe. I understand that at I-class I'll need to make sure I've got enough oomph off the pad; and that at M-class I'll want to make sure I don't rip the fins off. Given all that, and with the idea of minimizing purchase of motor adapters and/or motor casings:

• What I-class motors would you recommend?
• What L2 motors would you recommend?
• What M-class motors would you recommend?

Thus far ( and looking into the future ), it seems as if I could do I-class and L2 in the same 54mm adapter. Is it possible to do these in the same motor casing? If so, keeping the overall plan limited to two adapters with their appropriate casings and reloads seems like a good plan.

Regards,
-dh.

PS: Off to keep researching Someday Electronics.

Click to expand...

I would recommend further research into the L3 processes of Tripoli Rocketry Assocation and the National Association of Rocketry as they are the two certifying organizations. I am not sure how possible it is to even attempt what you are planning, since L2 must be achieved before even starting the L3 process. Hopefully some TAPs and or L3CC members will chime in on this as they are the certifying observers/representatives of the two organizations. Welcome TRF and take the time to enjoy rocketry and soak up the huge amount of information on this forum.

TRA is closest; NAR is further away. My thought here is to do the L3 requirements when building the L1 airframe, and reuse those same build details in certifying for L3.

I definitely look forward to critiques!

-dh.

for the l3 process: plans are normally submitted and approved before the build. Contact your local club.

Don't know about TRA rules but from the NAR website:

1.0 Flyer Requirements
1.1 Any individual attempting NAR Level 3 Certification must be a Level 2 high power certified
NAR member in good standing.
An individual may not submit a design for a Level 3 Certification project review to the L3CC
until Level 2 certification has been successfully accomplished.

Submit, certainly. My thought was preparing-but-not-submitting L3. Only those details needed for L1-on-I-class for L1, etc. for L2, L3.

rcktnut said:

Don't know about TRA rules but from the NAR website:

1.0 Flyer Requirements
1.1 Any individual attempting NAR Level 3 Certification must be a Level 2 high power certified
NAR member in good standing.
An individual may not submit a design for a Level 3 Certification project review to the L3CC
until Level 2 certification has been successfully accomplished.

Click to expand...

Translation:

If you want to certify L3 with NAR, you have to submit your proposed rocket design to a NAR "L3CC" member before you start building the rocket. You must be Certified at L2 before you can submit your design.

This means, with NAR, the L3 rocket can not be the same rocket used for L1 and L2.

I would talk to a tap first. Frankly, this is worrisome to me not knowing your background and experience.

I think there is a lot to be learned at each cert level, and plenty of flying to do before moving from L1 to L2, and again going from L2 to L3.

That said, please tell us how you plan on building this rocket. Details would be useful to evaluate and to advise.

So, basics here. The Goblin is short and stubby, correct? What do you think it will weight without motor?

I did a little look at this. I really do not think you can do a L1 with this...too big and heavy. I start doing some quick sims, and you start looking at big K motors to get close to 1800-2000 feet. By large K mean a CTI K2000.

dhbarr said:

Greetings!

I just happened across a Polecat 10" goblin, and grabbed it up hoping to ( eventually ) do my L1, L2, and L3 certs on the same airframe. I understand that at I-class I'll need to make sure I've got enough oomph off the pad; and that at M-class I'll want to make sure I don't rip the fins off. Given all that, and with the idea of minimizing purchase of motor adapters and/or motor casings:

• What I-class motors would you recommend?
• What L2 motors would you recommend?
• What M-class motors would you recommend?

Thus far ( and looking into the future ), it seems as if I could do I-class and L2 in the same 54mm adapter. Is it possible to do these in the same motor casing? If so, keeping the overall plan limited to two adapters with their appropriate casings and reloads seems like a good plan.

Regards,
-dh.

PS: Off to keep researching Someday Electronics.

Click to expand...

If you are looking to get certified, you could only get a L2 with a Polecat Goblin.

Could you tell us a little about your background, any previous rockets you have flown, if your part of the NAR or Tripoli, any clubs you go to, where you're located? Then we will be able to actually help you pick a rocket and get certified.

dhbarr said:

Greetings!

I just happened across a Polecat 10" goblin, and grabbed it up hoping to ( eventually ) do my L1, L2, and L3 certs on the same airframe. I understand that at I-class I'll need to make sure I've got enough oomph off the pad; and that at M-class I'll want to make sure I don't rip the fins off. Given all that, and with the idea of minimizing purchase of motor adapters and/or motor casings:

• What I-class motors would you recommend?
• What L2 motors would you recommend?
• What M-class motors would you recommend?

Thus far ( and looking into the future ), it seems as if I could do I-class and L2 in the same 54mm adapter. Is it possible to do these in the same motor casing? If so, keeping the overall plan limited to two adapters with their appropriate casings and reloads seems like a good plan.

Regards,
-dh.

PS: Off to keep researching Someday Electronics.

Click to expand...

If you are looking to get certified, you could only get a L2 with a Polecat Goblin.

Could you tell us a little about your background, any previous rockets you have flown, if your part of the NAR or Tripoli, any clubs you go to, where you're located? Then we will be able to actually help you pick a rocket and get certified. By the way, most L2 motors and I know any L3 motor will never use a 54mm motor adapter, they are 98mm.

(P.S. I wouldn't recommend thinking about the price too much right now if you want a L3, the motors cost more than the actual rocket, and 50-100 bucks won't really matter when you're spending $600 on M and N motors)

Certainly I don't mean to alarm anybody with my idle speculation I think I've answered all the above question groups; all pardons if I missed a section.

* Yes, have been over to thrustcurve, and compared / contrasted with the NAR S&T combined certified list.
* Tulsa Rocketry ( Tripoli ) is the closest club, and I am a newbie in both NAR and TRA.
* I have reviewed other 10" Goblin builds, as well as FatMan and/or Thumper also from Polecat.
* I don't know what building techniques I'll use, since I haven't decided how fast I'll want to go on this airframe.
* Barrowman, Dahlquist, and Galejs will have a lot more to say about this stubby 20-pounder than I will.
* It's not money I want to limit, necessarily; it's just fun to play with constraints
* I didn't buy the Goblin10 because I want to cert tomorrow; I bought it because it was in stock

I suppose a more scope constrained version of the initial question could be in order: What's the fattest thing you've seen go up on an I? Which I was it?

Probably a Loc kit ion their 5.5" airframe. I have seen quite a few mini Mags on a variety of higher thrust I motors.

RocketryBill said:

You can't buy a I motor legally until you even get your L1, are you certified? If you want to get L1 certified you have to do it on a H motor you can't skip a H and do it on a I motor.

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This is incorrect information. From the NAR certification page... "The modeler must demonstrate his ability to build and fly a rocket containing at least one H or I impulse class motor."

I've flown a LOC Warlock (7.5" airframe, 100 oz with no motor) on an I297 to ~1500' and I540 to 1850'. If you don't mind adapting from 75mm to 38mm, a Cesaroni I540 or Aerotech I500/I600 might be possible. Definitely a flight to simulate first though as it will be quite low...

Best software for simming widebodies? Obviously I'm not going to have a whole caliber between CP/CG, and I'd like to avoid doing the Galejs works manually ( but I will if I need to ). I600 looks interesting...

dhbarr said:

Best software for simming widebodies? Obviously I'm not going to have a whole caliber between CP/CG, and I'd like to avoid doing the Galejs works manually ( but I will if I need to ). I600 looks interesting...

Click to expand...

Both Apogee's Rocksim ($123.00) and OpenRocket (free) require workaround tricks to simulate short fat rockets, its known as base drag correction. Unlike longer rockets Short Fats are stable on less than one caliber due to base drag.
Check out post #3 in the following link, you will need to download the Apogee Newsletters specified. https://www.rocketryforum.com/showt...t-Rockets&highlight=Rocksim+Short+Fat+rockets

Awesome, thanks for the tip. I've already been using OpenRocket, the base drag correction was exactly what I was looking for.

RocketryBill said:

If you are looking to get certified, you could only get a L2 with a Polecat Goblin.

Could you tell us a little about your background, any previous rockets you have flown, if your part of the NAR or Tripoli, any clubs you go to, where you're located? Then we will be able to actually help you pick a rocket and get certified. By the way, most L2 motors and I know any L3 motor will never use a 54mm motor adapter, they are 98mm.

(P.S. I wouldn't recommend thinking about the price too much right now if you want a L3, the motors cost more than the actual rocket, and 50-100 bucks won't really matter when you're spending $600 on M and N motors)

Click to expand...

L1 motors are available in 29mm to 54mm, L2 are in 38mm to 98mm, and L3 motors are 75mm and up (though Loki is soon to release a 54mm M). There are plenty of L1 motors in 54mm, and the majority of L2 motors are 54mm. While it is true that the expense associated with L3 is necessarily high, that doesn't mean that someone going for it should be any less conscious of their spending, or that they have to spend $600 on M and N motors when there are $250 M motors available. My question for dhbarr is what he is hoping to accomplish. Do you plan on flying L3 regularly? If it is your goal to get your L3 as soon as possible for whatever reason, the safest route would be to gain experience by building a smaller rocket that will safely fly on L1-L2 motors for those certs, and then take your learning from those build(s) and apply it to your L3. You may find on the way there that I motors or even F motors are enough fun that you don't need to spend more to enjoy the hobby.

You're being too nice eggplant. The harsh reality is that there is no such thing as jumping into a extremely easy rocket kit for under a thousand bucks, flying it on every motor A to Z while getting your L1, L2, and L3 for under a thousand bucks. My point is that if he want's to get his L3 3 days into the hobby, he shouldn't be taking advice from us on how to do it. When your a baby you don't learn how to run before you learn how to walk, and this guy has his L3 and what motors to waste his money on before he even sets his mind on starting out with something simple that he can fly legally with no certification.

So far he has dodged every single question of mine, and used clever strategies to get around the truth. I can tell that he has never flown a rocket, and he never successfully will if he doesn't show me back some respect. At this point he is getting hysterical.

eggplant said:

L1 motors are available in 29mm to 54mm, L2 are in 38mm to 98mm, and L3 motors are 75mm and up (though Loki is soon to release a 54mm M). There are plenty of L1 motors in 54mm, and the majority of L2 motors are 54mm. While it is true that the expense associated with L3 is necessarily high, that doesn't mean that someone going for it should be any less conscious of their spending, or that they have to spend $600 on M and N motors when there are $250 M motors available. My question for dhbarr is what he is hoping to accomplish. Do you plan on flying L3 regularly? If it is your goal to get your L3 as soon as possible for whatever reason, the safest route would be to gain experience by building a smaller rocket that will safely fly on L1-L2 motors for those certs, and then take your learning from those build(s) and apply it to your L3. You may find on the way there that I motors or even F motors are enough fun that you don't need to spend more to enjoy the hobby.

Click to expand...

I meant he'd be spending at least a few hundred dollars until he gets all his certification.

RocketryBill said:

You're being too nice eggplant. The harsh reality is that there is no such thing as jumping into a extremely easy rocket kit for under a thousand bucks, flying it on every motor A to Z while getting your L1, L2, and L3 for under a thousand bucks. My point is that if he want's to get his L3 3 days into the hobby, he shouldn't be taking advice from us on how to do it. When your a baby you don't learn how to run before you learn how to walk, and this guy has his L3 and what motors to waste his money on before he even sets his mind on starting out with something simple that he can fly legally with no certification.

So far he has dodged every single question of mine, and used clever strategies to get around the truth. I can tell that he has never flown a rocket, and he never successfully will if he doesn't show me back some respect. At this point he is getting hysterical.

Click to expand...

"too nice", "harsh reality", "hysterical"? Jeez, some people are taking this way too seriously. As has been mentioned in this thread, his original plan is not possible. People have been bringing up different strategies that he might try to accomplish his goals, while others are trying to scare him away by saying that he hasn't "respected" them enough. John Coker jumped right into the large end of HPR after building four rockets, half of them LPR. Now he runs what is arguably one of the most useful resources for rocketry on the internet. As a community, should we scare people away because they are eager to start? I don't think so, especially when they are as receptive of our suggestions as he has been.

You completely misinterpreted what I was saying. He's a grown person, I'm sure we're not scaring him off, but I'm trying to tell him that he shouldn't rush into L3, and I'm sure John Coker didn't either.

I've answered most questions in a fairly straightforward and civil tone, I would think. If that didn't come across the wire, *shrug* text is funny that way.

I don't know where "a thousand bucks", "easy", or "every motor from A-Z" came from . Some great responses upthread, thanks for shaking loose more things for me to think about!

I do see people getting 20-25 lbs up on I600's while keeping well inside NFPA 1127 4.9.1; although it's not necessarily a very -good- idea

Apparently "One rocket for L1-L3 in a single day" is a common thread to have; this is not that thread This is the thread for the guy who wanted to buy a Big Ol' Goblin, so he bought one.

Cheers!
-dh.

The hardest part about the 20-25lbs on I600 is actually building a rocket that is specified at that weight at that weight most of us tend to build heavier.

This is the best example of a large rocket on a tiny motor (6" x 7ft on a 29mm G75), but this is purpose built out of all carbon... But with a full I and decent light weight build techniques it might be possible to do what your suggesting. I think I remember a forum member building a blue tube rocket that could fly from large high thrust H motors up to significant M motors, but I don't remember the specifics.

Ravenex said:

This is the best example of a large rocket on a tiny motor (6" x 7ft on a 29mm G75), but this is purpose built out of all carbon... But with a full I and decent light weight build techniques it might be possible to do what your suggesting. I think I remember a forum member building a blue tube rocket that could fly from large high thrust H motors up to significant M motors, but I don't remember the specifics.

Click to expand...

Do you recall the weight of the carbon one? Any links to a build? 6" diameter is a lot of drag for a 29mm! Impressive.

McKailas Dad said:

Do you recall the weight of the carbon one? Any links to a build? 6" diameter is a lot of drag for a 29mm! Impressive.

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PML has one on it's website under "composites".........



https://publicmissiles.com/UltimateIo.htm


https://publicmissiles.com/product/composites



Edit: by the way the highest thrust I motor that was found during my search...CTI -I-800 V-max 210lbs. 4 grain 38mm

I'm sorry, I must have been really tired, I meant to post the link. It's the public missiles one blackjack linked.