38mm or 54mm?

I was asking all these same questions a few weeks ago. I wound up with a small stack of Cesaroni 38mm tubes and I could not be happier. 3G, 5G, and 6XL for me. Also I opted for a nice 54-38 adaptor and plan on 38mm 6XL reloads in my 54mm birds. Without closures for 38mm hardware, I have spent a small amount of money and have a massive amount of options.

taiwanluthiers said:

Well if I flew I'll likely fly with AARG, last I remember their field is only L1 capable...

Click to expand...

Calling a field L1 doesn't make any sense. If they have a waiver for class 2 rockets, it doesn't matter what level the motors are, just as long as they are class 2 and you stay under the waiver. You can fly a O motor and stay under 5000 ft if you have a heavy enough rocket. With that said, the local club may put restrictions on what size rockets or motors fly based on their GSE and available safe distances they can set up with. You should select your motor size based on rocket size and altitude you want to fly at "most" of the time and in the "average" conditions for the field. Fields on the east coast are much different then the ones out west and altitudes and recovery methods vary. All of that will play a part in what size rocket and motor you use.

For flights under 5000 ft, in a 2 - 4 lb 2.6" dia. rocket, I would stick with 29mm, if the rocket is 3" dia. and in the 4 - 6 lb range, 38mm would work pretty well. If the rocket is 8 - 12 lbs I would definitely go with 54mm. When you get to a field with a higher waiver, put the large 54mm in it and push for 10,000 ft. In the mean time, adapt down to 38mm and have fun.

gltruett said:

Loki does not offer a complete kit as do A/T and CTI, one reason being you reuse Loki nozzles so it is part of the hardware purchase rather than reload. In a future products thread someone suggested Loki develop a spacer system, don't know if that will happen but it is a possibility. Loki reloads are less expensive than CTI for similar impulse, that will save money over the long term. I have hardware from all 3 for convenience but I'm starting to use the Loki more often. Just something to consider, all 3 make a great product.

Click to expand...

Gorilla motors have spacers available. They are snap ring cases. They only have spacers for 54mm and 75mm. No spacers on the web site for 38mm, 98mm, or 152mm.

There are plenty of 38mm “J” reloads out there so you can get your Cert 2 using a 38mm motor. No need for a 54mm untill you want to fly “K”$$$$

boomtube-mk2 said:

There are plenty of 38mm “J” reloads out there so you can get your Cert 2 using a 38mm motor. No need for a 54mm untill you want to fly “K”$$$$

Click to expand...

You are absolutely right about the L2 on 38mm. The problem usually come with the altitude a J motor gets in a 38mm rocket. If you are on a field with a low waiver and the 38mm L1 fits well, you might be pushing the waiver or recovery area when you try the J motor. Bottom line, you have to learn to fly the field.

I think L1 field is understood to mean the minimum land area for a particular class of motor... I think that's in the safety code. So I can fly a O in a "L1" field if the rocket weighted half a ton, however the RSO may not allow it since the land is below the recommended area.

taiwanluthiers said:

I think L1 field is understood to mean the minimum land area for a particular class of motor... I think that's in the safety code. So I can fly a O in a "L1" field if the rocket weighted half a ton, however the RSO may not allow it since the land is below the recommended area.

Click to expand...

I guess the O motor was over the top, but...

Based on the Tripoli safe distances, you only need 1500 ft diameter/closest distance for H through M motors, or 1/2 the waived altitude. So if you have a 3000 ft waiver you can fly H through M motors on a 1500 ft diameter field as long as you stay below the waiver. It has to do with the waiver, not the motor size until you get over M.

If the field is too small for the M, its too small for the H also.

Handeman said:

I guess the O motor was over the top, but...

Based on the Tripoli safe distances, you only need 1500 ft diameter/closest distance for H through M motors, or 1/2 the waived altitude. So if you have a 3000 ft waiver you can fly H through M motors on a 1500 ft diameter field as long as you stay below the waiver. It has to do with the waiver, not the motor size until you get over M.

If the field is too small for the M, its too small for the H also.

Click to expand...

Looks like the latest version of NFPA 1127 got rid of the old chart showing Field size requirments by motor size.....the old chart is below.

TABLE 1: LAUNCH SITE DIMENSIONS
Installed Total Impulse (N-sec) Equivalent Motor Type Minimum Site Distance (feet) Equivalent Distance (miles)

160.01 - 320.00 H 1,500 .28
320.01 - 640.00 I 2,500 .50
640.01 - 1280.00 J 5,280 1.00
1280.01 - 2560.00 K 5,280 1.00
2560.01 - 5120.00 L 10,560 2.00
5120.01 - 10240.00 M 15,480 3.00
10240.01 - 20480.00 N 21,120 4.00
20480.01 - 40960.00 O 26,400 5.00

However based on the minimum safe distance alone it may not be enough, as L1 fields probably lack the proper distance for M's. Because if a M catos, its destruction would be bigger than a H.

CATO is about the safest failure. Land sharks, unstable rockets, and ballistic returns are the scary events.

High altitude ballistic recoveries scare the crap out if me.


Because I am addicted, this is coming from my phone.

Ravenex said:

I got my level one and level two motors as cti cert specials and got a 38mm 3g and a 54mm 3g case free. Even though I need more hardware to fill out the sets it was a good deal.

Click to expand...

I did the same, and love that all I need to do is pick up a 6 grain case and another spacer, and I can fly almost the entire family (minus the xl, of course).

rharshberger said:

IIRC USPS won't take HazMat shipments the exception being ORM-D (Other Regulated Material-Domestic), all HazMat eligible material have to be shipped through a certified HazMat carrier. I maintain my CDL with HazMat endorsement, and move a lot of it. Also iirc Black powder motors and motors up to certain Gs are excepted as ORM-Ds instead of the more specific Has Mats. 49 CFR 172.101 is the section of the Code of Federal Regulations pertaining to transporting HazMat. ORM-Ds are things like hairspray, bug killers, brake cleaners etc.

Its way more complicated than it needs to be, but there are 38mm motors that ship w/o Hazmat charges, none for 54mm (although some motor dealers, will absorb the fee for large enough orders, or have it priced in).

I'm probably going the route of 54mm MMTs, adapted for 38mm until I can acquire the hardware so I can fly the big Ks.

Click to expand...

0.) All rocket motors are Class 1 materials which can not be reclassified as ORM-D.

1.) The USPS will only accept assembled rocket motors containing not more the 30 grams of propellant and reload kits with individually packaged propellant grains weighing not more than 30 grams.

2.) You can go to the USPS website and download the exact requirements for obtaining permission, and the labeling and packaging requirements.

Bob

bobkrech said:

2.) You can go to the USPS website and download the exact requirements for obtaining permission, and the labeling and packaging requirements.

Bob

Click to expand...

But you still must be submitted by the manufacture as an approved shipper of their product

soopirV said:

I did the same, and love that all I need to do is pick up a 6 grain case and another spacer, and I can fly almost the entire family (minus the xl, of course).

Click to expand...

Take a good look at the available reloads and the rockets you would fly in, too. I was planning on a 6G case but the given the reload selection and the aft sections of my current birds it did not make any sense. No point in simply filling out the product line!

Handeman said:

For flights under 5000 ft, in a 2 - 4 lb 2.6" dia. rocket, I would stick with 29mm, if the rocket is 3" dia. and in the 4 - 6 lb range, 38mm would work pretty well. If the rocket is 8 - 12 lbs I would definitely go with 54mm. When you get to a field with a higher waiver, put the large 54mm in it and push for 10,000 ft. In the mean time, adapt down to 38mm and have fun.

Click to expand...

I have rockets that are 54mm that i have never flown with actual 54mm motors.

Having been around research motor makers, you always hear a term, "the smallest motor i will make is...?", and it seems that the more motors the person has made the larger that number becomes. 1 guy actually told me a 75mm is the smallest motor he will make. You would think that might come from arrogance, but in effect it's actually becuase of efficiency in scale. I make lots of 38mm in pourable, and its as hard as a 15lb M motor. Just eventually, you quit working hard to accommodate for less.

I was once a proponent of put a big hole in it and adapt down.... but not so much any more. it's work. repeated work. work that will never end.
For me 38mm is the ultimate high-power motor. from G al the way up to the K... such a broad swath of motors. rocket - motor combinations are the best youll see.......
54mm is a very Niche diameter, here the biggest benefit you'll find, is it opens up to moon burners and non-typical dual thrust motors, or odd grain geometries, you dont see in 38mm(or above I impulse because of L/d ratios), but in a smaller than 75mm or 98mm price point. this doesn't exactly drive my go, so it was logical for me that i went directly to 75mm after that. the 38 stops where the 75 begins for standard bates grain type motors.
I have a 12 lb rocket that i can fly on an M/6000ns motor, or a J 800ns motor.... but, i could even put in a 75mm k. without additional work.

I am not a rich affluent guy, so i cant buy it all... So I went and skipped 54mm investment altogether. I fly mainly loki 38/740 38/1200 76/8000 98/12500, and have a 75/4000 mostly missiles case.
as you can see, all i would need is one 75mm x 2000ns case... this would let me play the entire range of impulse with out a lot of hardware.


So, i have 38 and 75, i never adapt down because.... its work, and there's usually a motor that will drive the way it needs to. save the oddball 54 rockets for 1 off projects of moonburners or dual thrust altitude attempts...

Handeman said:

I guess the O motor was over the top, but...

Based on the Tripoli safe distances, you only need 1500 ft diameter/closest distance for H through M motors, or 1/2 the waived altitude. So if you have a 3000 ft waiver you can fly H through M motors on a 1500 ft diameter field as long as you stay below the waiver. It has to do with the waiver, not the motor size until you get over M.

If the field is too small for the M, its too small for the H also.

Click to expand...

From a code sense your right, but from a practical sense its just wrong. It's true the waiver application is reviewed and the launch site dimensions plays to the altitude granted. probably for sites with more than a 1500 feet diameter..Site dimension almost always controls that altitude, because it also includes recovery of the vehicle. The table shows that if you have a min launch site of 1500 feet, you can fly up to M impulse. But, that ignores the requirement for safety distance. You have to fly the rocket where you can ensure that it never leaves the waiver cylinder, and this means that you can have a launch site that can fly H all day long, but never be able to provide 500 feet of safety distance due to roads, buildings and other things like landowner restrictions, while ensuring that the M flight does not exit it's waiver. Altitude, isn't the only part of the planning in what can be flown, drifting under parachute and safety of spectators or non-participants are other factors. 100feet safety distance is a lot easier to accomodate, and still stay in 3,000 agl with a 1500' diameter, than it is if you have to maintain 500. so, it does have to do with the motor, and more importantly making sure we are in compliance with code and safe practices every flight. whats the addage, just because you can doesnt mean you should.

one of my frequented sites, i have flown up to L motors, could go bigger, easily M, if not even N/O. 22,000 agl. while it is by code, allowed, those rockets are simply not flown there because there's no convenient way of doing so because of safety distance and pitfalls like a ravine near the recovery zone.

launch setup dictates most impulse limitations on all ranges i've seen it implemented, not the waiver.

bobkrech said:

0.) All rocket motors are Class 1 materials which can not be reclassified as ORM-D.

1.) The USPS will only accept assembled rocket motors containing not more the 30 grams of propellant and reload kits with individually packaged propellant grains weighing not more than 30 grams.

2.) You can go to the USPS website and download the exact requirements for obtaining permission, and the labeling and packaging requirements.

Bob

Click to expand...

Bob, the better answer is also the most simple, YES, USPS will not ship class 1 materials, however. The federal government was nice enough to give "us" an exemption to that hazmat requirement. SP-7887. This is how and why usps can ship some rocket motors. https://www.aerotech-rocketry.com/c...RegulatoryDocuments/DOT/dot-sp_7887_19th_.pdf
however, i will add, they were going to do away with sp-7887 .

tbonerocketeer said:

But you still must be submitted by the manufacture as an approved shipper of their product

Click to expand...

all in an honest days work for the man. More paperwork = more fun and profit! Lol.

ClayD said:

Bob, the better answer is also the most simple, YES, USPS will not ship class 1 materials, however. The federal government was nice enough to give "us" an exemption to that hazmat requirement. SP-7887. This is how and why usps can ship some rocket motors. https://www.aerotech-rocketry.com/c...RegulatoryDocuments/DOT/dot-sp_7887_19th_.pdf
however, i will add, they were going to do away with sp-7887 .


all in an honest days work for the man. More paperwork = more fun and profit! Lol.

Click to expand...

You are totally confused and your statement is incorrect.

The Unites States Postal Service is a US government agency that delivers mail and packages within the United States. It is not allowed to transport Hazardous materials by Congress, but it is not regulated by the United States Department of Transportation which is another US government agency that regulates the commercial (non government) transportation of materials, both hazardous and nonhazardous, within the United States.

What the USPS will and will not transport is delineated in Publication 52. https://pe.usps.com/text/pub52/welcome.htm The USPS considers certain hobby rocket motor and reloads to be non-hazardous in their transportation system and allows them to be mailed with certain restrictions. https://pe.usps.com/text/pub52/pub52apxc_002.htm It allows rocket motors with not more than 30 grams of propellant, and reload kits with individually packed propellant grains not exceeding 30 grams of propellant, to be mailed by Ground Parcel Post by individuals who have obtained prior written permission from the USPS.

Transport of Class 1 materials is allowed in commerce under DOT regulations but rocket motors are always considered a hazmat regardless of size or quantity and you will be charged a hazmat fee. DOT-SP 7887 simply permits Class 1.4S materials to be reclassified as Class 4.1 Flammable Solids which are easier to ship as hazmat. It's still a Hazmat, and it still requires a Hazmat Fee.

BTW: I am a signatory to DOT-SP 7887, 8451, 10996 and 13133 so I do know what the rules are.

Bob

View attachment current-7887-201308439 - Renewal Letter.pdf