TARC frustration: advice needed

[neil_w]

Ah yes, now I see that in section 2.2.

Just did a quick sim, and assuming their rocket came near target altitude their duration was going to be absurdly long... two 21" chutes for the payload section. Yikes.

 

[JJSR]

I can't understand why they would spend all that money to register 3 teams, not knowing how to even build a rocket, or reached out sooner for help.

2 or 3 years ago we "the club" was approached by a school that complained about how much the entrance fee was.
They registered 10 teams, they had 40some kids interested, But when it was time to come out and launch the teacher never showed nor anyone from the school. ???

 

[neil_w]

Yeah, makes no sense to me. Just not a lot (any?) of thought put into the whole thing, and then kids left mostly to their own devices.

 

[Buckeye]

Buckeye,

I can, have done, and do all of those things, whenever there is a need for it. Flying three eggs in a cardboard TARC rocket on an F motor hardly justifies the effort. You are not my "professor", nor will I "jump through any more hoops" for you.

BTW - As you should already know thrust, drag, and air density are never "constant" and are highly variable. Solving for them is never valid, in terms of absolute accuracy. It makes no difference whether the solutions are generated by a computer or manual computation.

So, with that said, why don't you come up with something constructive to try to help these kids ?

Dave F.

Read it again. I said "varying" as in "non-constant" mass, thrust, drag, density. There is no closed form solution to those trajectory equations with non-constant parameters, so unless you use numerical methods, you haven't solved them. Rocksim, OpenRocket, RasAero, even ol' RASP can model those parameters very well with numerical methods. They capture the physics better than any hand calculation possibly can, and hence are more accurate.

You said you were going for Level 3. Simple approximations to make the equations tractable don't cut it when your rocket goes high, fast, and burns a lot of propellant. My money is on RockSim.

Go read the Electronics and Software forum. There is lots of good discussion on code, models, accuracy, and interpreting flight data. Computer models are ideal for TARC students.

 

[BLH]

Don't yell at me, but maybe they are the true rocket hobbyist! And don't really care about whether they win or not. Whether their rocket(s) fly or not. Don't care about sim(s) or math...

Naturally to us, It would be better if their rockets had a chance to work. But maybe they have three teams and just like playing with the glue and paint and enjoying time together as kids. I'll bet they even broke some of the eggs for fun.

Hope teacher at least made them wear gloves if they were playing with epoxy. White glue would have been more suitable. Just sayin.

 

[JJSR]

Ok ok we get it you use calculations and you use calculator
Enough
Lets try to help the kids

 

[neil_w]

Hope teacher at least made them wear gloves if they were playing with epoxy. White glue would have been more suitable. Just sayin.

No gloves!

Yet another weird thing (every post I have to include one ): They 3D-printed a screw-on retainer from a design they got.... somewhere. Apparently it took several prints to get the threads to work right. Except the hole in the screw-on cap is way too big, just a *hair* under 29mm. They'll need to add some wraps of tape on whatever motor to keep it in there securely. Nice that they wasted their time futzing with that rather than spend a few bucks on pre-made retainers. *sigh*

 

[Ez2cDave]

Is there a trick to removing generic 5-minute epoxy other than sanding? I don't know of one.

It may be possible to use a hair dryer to soften the epoxy . . . Then, it can be "peeled" out.

Dave F.

 

[Ez2cDave]

Read it again. I said "varying" as in "non-constant" mass, thrust, drag, density. There is no closed form solution to those trajectory equations with non-constant parameters, so unless you use numerical methods, you haven't solved them. Rocksim, OpenRocket, RasAero, even ol' RASP can model those parameters very well with numerical methods. They capture the physics better than any hand calculation possibly can, and hence are more accurate.

You said you were going for Level 3. Simple approximations to make the equations tractable don't cut it when your rocket goes high, fast, and burns a lot of propellant. My money is on RockSim.

Go read the Electronics and Software forum. There is lots of good discussion on code, models, accuracy, and interpreting flight data. Computer models are ideal for TARC students.

You don't listen very well . . . The "games" are over.

Rocksim won't help these kids right now. They need basic knowledge and skills, acquired through "hands-on" teaching.

Dave F.

 

[BLH]

It may be possible to use a hair dryer to soften the epoxy . . . Then, it can be "peeled" out.

Dave F.

Wow, Epoxy is a thermoset. Does this really work?

This is not TARC related either so my bad.

How about building new rockets just for fun TRAC or not. They should be able to build some in a couple weeks. I still think they just want to have fun!

 

[Ez2cDave]

As I see it, the kids have zero chance of going to the finals.

So, what I suggest is to take this time to really teach them the fundamentals of Rockery . . . Throw the TARC rules out the window and properly prepare them for next year.

Dave F.

 

[boatgeek]

At least too long a hang time is relatively easily fixed by reefing chutes.

For team registrations, I like to start enough teams to hold all of the students who say they’re interested at 10/team. For each team, I just register 4-5 students who are returning and I’m pretty sure will keep showing up. Newcomers who stick with it can be added before the first scored flight. That saves a lot of dropping students who drop out of the club midway through the year.

 

[Ez2cDave]

Wow, Epoxy is a thermoset. Does this really work?

This is not TARC related either so my bad.

How about building new rockets just for fun TARC or not. They should be able to build some in a couple weeks. I still think they just want to have fun!

Epoxy can be softened by heat. That's why people use JB Weld ( 600 F ) on Motor Mount Tubes in HPR.

Dave F.

 

[BLH]

Maybe that's way my motors keep "flying through"!

Can't the kids just fly regular rockets? Why does it have to be TARC? In a hobby, competition is over rated...

 

[boatgeek]

They also have a nonzero chance of going to nationals. I wouldn’t bet any money on them but I’ve also seen teams hit lightning in a bottle on test flights. If I were mentoring them I’d want them to fix this rocket up and fly it. Learning by fixing mistakes can be pretty effective.

 

[Ez2cDave]

Why does it have to be TARC? In a hobby, competition is over rated...

Because TARC "dangles this carrot in front of the kids noses" . . .

QUOTE:

"A pool of over $100,000 in cash and prizes is shared by the top 10 teams, with Raytheon Company sponsoring the winning team’s trip to participate in the International Rocketry Challenge."

END QUOTE:

Dave F.

 

[BLH]

Because TARC "dangles this carrot in front of the kids noses" . . .

QUOTE:

"A pool of over $100,000 in cash and prizes is shared by the top 10 teams, with Raytheon Company sponsoring the winning team’s trip to participate in the International Rocketry Challenge."

END QUOTE:

Dave F.

Ah ha! Do the kids get the money?

 

[BLH]

The math and money may have gotten me off-track yet the question remains why some TARC team(s) built rocket(s) without some kind of build advisor or someone who knows about flying rockets?

Seems like the ones taking the money in should check that out...

How could builders be more locatable and/or involved in the educational system for TARC so they don't get glue in the holes and other common pitfalls rocket flight?

Also, maybe teach F=Mass*Accl and CP, GG, stuff like that...

 

[JJSR]

TARC website has a list of mentors, all "they" teachers & kids have to do is read.

 

[neil_w]

There was an NAR-affiliated individual allegedly assigned as a mentor; don't remember his name but I briefly checked him out online and he seems legit. I have no idea how much (if at all) he was consulted in any of this. And as I said, I attempted to make myself available to the girls on the team through my friends, but I have no channel to the advisor and until last week my offer never was taken up. I had hoped to get the girls together in the summer or early fall to do one or more intro sessions about rocket, but again it never materialized. I tried.

As for the appeal of TARC vs. just building rockets: you'd have to ask each of the kids for their own views on this, but in general it's just very different to be part of a team focused on a goal in the context of a competition vs. just doing something for fun. Likewise, most robotics clubs (AFAIK) are focused on F.I.R.S.T or whatever competition. *Some* kids might be in it for the rockets (or robots), but others just want to compete at something. I would not presume to redirect the activities of a TARC team into recreational flying, unless they officially want to throw in the towel for this year (they don't, at least not yet).

 

[Ez2cDave]

There was an NAR-affiliated individual allegedly assigned as a mentor; don't remember his name but I briefly checked him out online and he seems legit. I have no idea how much (if at all) he was consulted in any of this. And as I said, I attempted to make myself available to the girls on the team through my friends, but I have no channel to the advisor and until last week my offer never was taken up. I had hoped to get the girls together in the summer or early fall to do one or more intro sessions about rocket, but again it never materialized. I tried.

No "Math" or "Money" . . . I promise !

Is that Mentor located in NJ ?

This PDF file lists all of the Mentors for this year, along with Contact Information ( Location / Phone Number / Email ) for each one.

https://www.nar.org/wp-content/uploads/2019/01/Mentor-List-24-Jan-2019.pdf

BTW - There is an 8-MONTH period before the Qualification Deadline ( plenty of time to teach Rocketry skills, design and fly some "non-TARC-specific" rockets, and for them to formulate the things they want to incorporate . . . Egglofting, Descent Rates, Target altitudes, etc.) The rockets would not "be" the TARC rocket, but they would employ all necessary skills.

Dave F.

 

[firpisto34]

Im currently leading a Tarc team and their rocket weighs 480 g and they're using a F39-6 motor. They've only done one test so far it was about 80 ft under 856. It was really windy that day so I cant figure out if it was so low cause of the weather or the rocket just needs more power. Any ideas on which it may be or maybe some higher thrust reloadable motors they could use that would fit the 24 mm motor mount they have (currently using a 240-40 case but a 24-60 case is available also)

 

[neil_w]

The mentor is on that list, to the extent that it matters.

One slight complicating factor is that these kids are moving up to High School next year, so it is unclear if they will do TARC again. I'm not sure that planning for next year will accomplish very much right now. My feeling is that we should try to get as much done as possible within this year's competition, even if it is not very much at this point. Next year is "who knows".

 

[afadeev]

Im currently leading a Tarc team and their rocket weighs 480 g and they're using a F39-6 motor. They've only done one test so far it was about 80 ft under 856. It was really windy that day so I cant figure out if it was so low cause of the weather or the rocket just needs more power. Any ideas on which it may be or maybe some higher thrust reloadable motors they could use that would fit the 24 mm motor mount they have (currently using a 240-40 case but a 24-60 case is available also)

F39-T (50 Ns of total impulse) is the most powerful reload you can put into 24-40 case.
24-60 case has F35-W motor with 57.1 Ns of total impulse, but it has a slightly lower initial/max thrust, and burns a little longer (1.6 secs vs. 1.3s for F39).

You really need to run both in OpenRocket, and see if you gain enough extra altitude with F35W to worth the bother. If not, you might have to purchase CTI 24mm cases (Pro24-2G/3G) and try F51/F70/F79 reloads.

Wind would cause non-vertical flight, and lower total altitude.
But you can't preclude the possibility of a windy day during certifying flights, so you want to be capable of flying higher than target, then add ballast as necessary.

HTH,
a

 

[Ez2cDave]

Im currently leading a Tarc team and their rocket weighs 480 g and they're using a F39-6 motor. They've only done one test so far it was about 80 ft under 856. It was really windy that day so I cant figure out if it was so low cause of the weather or the rocket just needs more power. Any ideas on which it may be or maybe some higher thrust reloadable motors they could use that would fit the 24 mm motor mount they have (currently using a 240-40 case but a 24-60 case is available also)

Is that 480gr the liftoff weight, with 3 eggs and altimeter aboard ?

Their problem is compounded by flying 24mm Hardware . . . 29mm opens up many more possibilities and power levels.

If they are "stuck" with a 24mm motor mount, the best option might be to move them over to Cesaroni 24 X 133 motors.

The F39 is only 50 Nt-Sec and higher thrust is less important than a longer burn with more total impulse.

The OTHER option is to build another Booster Section, with a 29mm motor mount and pick up new 29mm Hardware and reloads ( CTI or AT ).

Dave F.

 

[shreadvector]

I've seen MANY good flights with the 24/60 RMS loads (F35, F51) as well as single use F32.

Ditto for F26 and F42 single use 29mm

Finding them and getting them in time is the issue for many teams.

 

[BLH]

Finding them and getting them in time is the issue for many teams.

True that. It seems this time of year all the F's are fast sellers. I was looking for some for my non-TARC rocket and I think I may be done flying that rocket for several months. I wonder if Areotech and CTI plan for this.?.?.?

 

[shreadvector]

I have seen only one team recently flying clusters of Estes D12 motors. They did very well. In the first few years of TARC, clusters were fairly common.

 

[neil_w]

I would think clusters would tend to even out the variability among engine thrust.

 

[Ez2cDave]

I would think clusters would tend to even out the variability among engine thrust.

I wonder how the "powers that be" at TARC would react to the use of a "PVC Spider" for cluster ignition ?

https://meatballrocketry.com/pvc-spider/

Dave F.