F Engine Nomenclature Question

[tfrielin]

I'm trying to puzzle out the difference between an F50-6T and an F50-6FJ, specifically the latter letters.

Are the "T" and the "FJ" indications of the rocket fuel formulations? But not indicative of the respective engines' performance?

 

[rharshberger]

Correct, T is Blue Thunder propellant and FJ is Black Max propellant both are Aerotech motors.
You need to see the thrust curve graph to get an idea of the two motors performances. Even though both are 50 ns average the Blue Thunder should have a higher initial thrust and shoter burn.

 

[tfrielin]

Correct, T is Blue Thunder propellant and FJ is Fast Jack propellant both are Aerotech motors.

Ok, thanks. So, in looking at my instruction sheets for my Estes Mammoth and my Nike Smoke, I should be able to use the F50-6-- engines for both irrespective of those trailing letters because the performance of the "T" and the "FJ" remain the same??

I'm trying to order engines that will work in both (Obviously..)

 

[rharshberger]

Ok, thanks. So, in looking at my instruction sheets for my Estes Mammoth and my Nike Smoke, I should be able to use the F50-6-- engines for both irrespective of those trailing letters because the performance of the "T" and the "FJ" remain the same??

I'm trying to order engines that will work in both (Obviously..)

Check out Thrust Curve .org you can run simple simulations on it and its available as a Android app. Also Open Rocket is a free design and simulation software.
The one motor depending on total impulse may push the rocket a bit higher and faster than the other.

 

[Rex R]

from what I see in the catalog, the mammoth will tend to disappear (and stress the fins) on an F50, while the smoke goes to approx. 1100'. might be best to consider a smaller motor for the mammoth.
Rex

 

[scsager]

I'm trying to puzzle out the difference between an F50-6T and an F50-6FJ, specifically the latter letters.

Are the "T" and the "FJ" indications of the rocket fuel formulations? But not indicative of the respective engines' performance?

You are correct on the formulation - T (blue thunder) fj (fast jack)

I'm not sure where you saw an F50-6FJ I this a new motor, or ...??? The only F50 I know of is the F50-T (blue thunder) With a 6 second delay you are looking at 1200-1500 ft in altitude. With this motor you will need a big recovery area minimum of 1000' x1000'.

The mammoth will get a respectable 600' or so with a smaller E20-4T motor (adapter needed). Might be a better choice for a first flight.

 

[tfrielin]

You are correct on the formulation - T (blue thunder) fj (fast jack)

I'm not sure where you saw an F50-6FJ I this a new motor, or ...??? The only F50 I know of is the F50-T (blue thunder) With a 6 second delay you are looking at 1200-1500 ft in altitude. With this motor you will need a big recovery area minimum of 1000' x1000'.

The mammoth will get a respectable 600' or so with a smaller E20-4T motor (adapter needed). Might be a better choice for a first flight.

TheF50-6FJ is listed as an engine choice in my Estes Mammoth instructions sheet.but in shopping for one, I admit, I'm not seeing any.

 

[rharshberger]

TheF50-6FJ is listed as an engine choice in my Estes Mammoth instructions sheet.but in shopping for one, I admit, I'm not seeing any.

F26-6 or 9FJ is the 29mm single use FJ. There is also a Econojet F23-FJ as well in 29mm.

 

[Rex R]

yep that is what the instructions say. That is a typo, Estes/ aero tech did not have an F50-6fj. I would NOT suggest either the G40 or the G80 for the mammoth .
Rex

 

[MALBAR 70]

I've flown my Mammoth a few times on the Estes black powder F 15-6 motors and have gotten quite respectable flights out of it.

 

[DavidMcCann]

This is a G38-4FJ

And an F50T

Motors get slightly confusing around this size. check out the data for these two-

https://www.rocketreviews.com/aerotech-f50t.html
https://www.rocketreviews.com/aerotech-g38fj.html

I didn't pick them for any specific reason, just they matched the two propellant types you asked about. But while one is an F, and one a G, they're only separated by 16Ns of total Impluse. And though the F is smaller, it hits much, much harder right off the pad. Just looking at the name of a motor sadly doesn't tell the whole story, it's best to check out more detailed specs.

I wouldn't limit yourself to whats in the instructions. The 4 econojet motors should do nicely as well. F20W, F23FJ,F27R and F42T.

 

[bill_s]

The smokey formulations burn slower and are less powerful for their size. Check the total impulse ratings. Unfortunately the smokey motors are also quieter. There are also sparky motors and smokey sparky motors such as Skidmarks and Dark Matter. Certification is required to buy and fly them, along with a fire-safe launch area, but they look and sound crazy and therefore are worth every Newton-second of impulse reduction. Another option is the white smoke motors such as the White Lightning. These are almost as powerful and loud as Blue Thunder and fairly smoky (white smoke), but sometimes are hard to light (best purchased from high turnover sources, or used in reloadable form so you can scrape some oxidation from the grain).

The total range of each letter size designation is 2:1, so checking actual impulse matters. Thrust and burn time can vary widely, for example the F10 burns for 8 seconds vs. an H399 eats through 4 times the propellant in about .3 seconds ;0 .

 

[tfrielin]

Well, I admit the aesthetics of the exhaust were not something I considered until now(!). Since my total composite is one F26 launch (lots of black smoke)

But since my tastes have been elevated, I do prefer a deep throaty roar and lots of yellow flame. Didn't care much for that thick black smoke!!

 

[DavidMcCann]

White lighting is your ticket.

 

[Bat-mite]

Impulse class .. Average thrust .... Delay time . Propellant Type
........ | ............ | ............... | ............ |
........ F ............ 50 ...... - ..... 6 ............ T


Regardless of what Estes says, weigh your built rocket in flight-ready condition with the motor and recovery in it.

ex. "2.5 pounds"

Convert the weight to ounces.

ex. "40 ounces"

Use this formula to see if you get at least a 5:1 thrust:weight ratio --

weight in oz. X 1.40625 Newtons per ounce

ex. "40 X 1.40625 = 56.25 N"

Hmm, maybe not enough thrust for this rocket. In reverse, of course, divide the average thrust by 1.40625 to get the maximum weight that you should try to launch with that motor.

50 N / 1.40625 N/oz = 35.6 oz

If you are using a 50N motor, then you know your final rocket weight needs to be under 35.6 oz.

The above is a broad generalization that does not take in the specific characteristics of individual motors. That is why you need to look at the thrust curve. A motor with 50 N of average thrust may get most of it in the first half-second, which means it will launch the rocket just fine. However, if the thrust peaks later, after it is off the pad, you may be underpowered on the pad.

NAR recommends a minimum 3:1 ratio, but most RSOs I know will only accept a 5:1 minimum ration. But again, it is up to the thrust curve.

As someone recommended, thrustcurve.org will give you the speed off the pad, which is truly the determining factor. It will tell you which motors are safe, and which are unsafe.

There could indeed be a situation where two motors have the same average thrust, but one is safe and one is not.

As wind speed increases, increasing thrust is a MUST! Your requirement for speed off the pad increases to compensate for the wind.

Finally, the total impulse of the motor will help determine its expected altitude. Total impulse is "avg. thrust X burn time." For example, 50 N x 1.4 s = 70 N-s, which puts it in the "F" impulse class.

So, when thinking about altitude, an F50 with a 1.4s burn time will go higher than an F50 with a 1.2s burn time.

Make sense?