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-   -   Little help on this one (?) (http://www.oldrocketforum.com/showthread.php?t=21389)

MrTwisty 02-20-2023 09:40 PM

Little help on this one (?)
 
So I have an issue here

Rocket #1
105 grams- weighed as launched.
Package says 800ft. on a C6-5.
Can also use B4-4, B6-4.

Rocket #2
82 grams- weighed as launched.
Package says 800ft. D12-3, D12-5.

Same manufacturer.
Wording on engine selections was different which I'm trying to convey in the face card descriptions.
I'm avoiding using the brand or models on purpose to get legitimate opinions on the issue.

Rocket #1 was launched with a B4-4 on its maiden flight.
Climbed to about 50 feet then crashed down on the roof before ejecting the parachute.
Massive damage.
Repaired it (superglue fixes anything) and have launched it with C6-3/5/7 without issue. (7's are a nail biter but I'll make another thread for that).
Contacted the manufacturer about it- I wasn't worried about mine but if some kid built this and had the same experience that might be discouraging enough to walk away from rocketry so I wanted the packaging fixed
Manufacturer's contact said "it should have enough power" and closed my ticket.

I'll post the specific models in question but what do you guys think?
Calculator says 105g on a B4-4 is a no-go.

Bad motor or sloppy R&D?
For the record, rocket #1 is "modified" version of one of their other rockets (which I personally think is the root of the issue)

BEC 02-20-2023 10:58 PM

Projected altitudes are, in general, rather optimistic. From what you have shared, I’d more likely believe the 800 feet on a D12-5.

It seems that an unhealthy B4-4 (or a sticky launch rod) are the most likely.

But knowing what the models actually are will help.

Per the NAR cert data and time/thrust curves here https://www.nar.org/standards-and-t...ied-motor-list/ the initial thrust spike of both the Estes B4 and B6 motors is about 12 Newtons, and the B4 gets there a little sooner. 105g is a little over the recommended max liftoff weight for B4-4 per the same data…though based on the time/thrust curves I don’t understand why the recommended max is lower than the B6-4.

Estes C6 has a bit more initial thrust, but it takes 0.2s to get there.

MrTwisty 02-20-2023 11:25 PM

I have no problem posting the actual kits I was just looking for some unbiased opinions.
Forgot to add that theyre both the same size BT (kind of important there I guess) and about the same length.

Obviously 800 feet with an 82g rocket on a D-12 is not equal to 800 feet with a 105g rocket on a C6.
I'm just kind of pissed the rep blew me off when this is a legitimate issue one way or the other.
Even if the 105g rocket can be safely launched with a B4 the "projected heights" are so far off that we're talking about the difference between recovering and "bye, see you never" kind of launches in a known launch site.

I already bought a replacement for the 105g rocket so maybe I should just launch it again with a B4 and record it dying (?) as it lawndarts.
I spent a lot of time with the paint and slips on that rocket and even with the damage it's one of my favorites so I didn't want to kill it
But this is seriously bothering me so anybody have a better option to prove to the manufacturer that they're wrong?
Or is this on me somehow? (I clean my launch rods meticulously, but I'm not perfect and an underpowered motor is still on the table).

BEC 02-20-2023 11:54 PM

I have LOTS of altimeter data on a number of models because I fly an altimeter in almost everything I fly that’s big enough (and with really tiny altimeters, almost anything is big enough). I have seen estimates that are 20% off or more on many occasions. For example, the Checkmate two-stage mini-engine model has a catalog maximum altitude estimate of 900 feet. I have over 40 flights on three examples of that model, and 700 feet is really about the best it can do.

The estimate for the Super Orbital Transport is off by nearly a factor of two (based, unfortunately, on only three flights so far).

But they are just that, estimates. I know recent ones are generally out of RockSim, having bugged the Estes R&D department about the Checkmate and the Sterling Silver in particular on this point.

Historically, these estimates have varied. Over the Alpha’s 55+ year history it’s varied between 1000 and 1500 feet. Today’s Alpha is heavier than the original but it can, under good conditions, get to about 1000 feet on a C6-7. One built to an earlier, lighter configuration, can get there more easily and a little higher. The Alpha III’s performance is also pretty accurately represented.

But….what do you really want to be done? The one that crashed you should submit as a warranty claim, and they’ll probably send you a new one and a pack of B4-4s (I am assuming we’re talking about Estes, here). As for fixing the estimates….well….I’ve tilted at that windmill some, and so far haven’t much to show for it. It’s not like they’re going to recall all the catalogs and face cards so they can change the numbers and it doesn’t make sense to ask them to.

MrTwisty 02-21-2023 12:40 AM

I'm actually glad the Super Orbital Transporter is off that much (just got one and have limited field space so hopefully after trimming the glider it will stay on the grass).

What I want is accountability.
Legitimate numbers.
Not for me.
For the kids.
If my first rocket lawndarted I probably wouldn't be here today.

But novices look at those face cards and plan accordingly.

tbzep 02-21-2023 08:53 AM

Quote:
Originally Posted by BEC
It seems that an unhealthy B4-4 (or a sticky launch rod) are the most likely.

But knowing what the models actually are will help.

Yes, knowing the models will help. Some seem to defy their listed weights, and almost all of them end up heavier than what is listed in the specs.

105g is 3.7 oz. A Big Bertha's catalog weight is 2.2 oz. and is about all a B4-4 or B6-4 wants. I would want completely calm air to make sure it was a 100% vertical flight. An Estes Mercury Redstone is listed at 3.7 oz. and absolutely needs a C5-3 or C6-3. What is the kit that crashed?



.

Bill 02-21-2023 09:12 AM

Quote:
Originally Posted by tbzep
Yes, knowing the models will help. Some seem to defy their listed weights, and almost all of them end up heavier than what is listed in the specs.

105g is 3.7 oz. A Big Bertha's catalog weight is 2.2 oz. and is about all a B4-4 or B6-4 wants. I would want completely calm air to make sure it was a 100% vertical flight. An Estes Mercury Redstone is listed at 3.7 oz. and absolutely needs a C5-3 or C6-3. What is the kit that crashed?



.

Estes used to recommend an A5-2 or A8-3 for the Big Bertha, not not today. Did she get big and heavy and fat with age or did motors lose power?

http://www.ninfinger.org/rockets/no...a/69est016.html


Bill

A Fish Named Wallyum 02-21-2023 09:48 AM

Quote:
Originally Posted by Bill
Estes used to recommend an A5-2 or A8-3 for the Big Bertha, not not today. Did she get big and heavy and fat with age or did motors lose power?

http://www.ninfinger.org/rockets/no...a/69est016.html


Bill

Wow. Bertha on an A8-3 would be a back yard bird. Not sure it would even reach the level of the top deck.

ghrocketman 02-21-2023 11:25 AM

Motors have lost initial thrust over the years due to weakening of the black powder.
The weakening of the black powder is due to lack of DECENT QUALITY CONTROL of the charcoal used in the mix.
In other words, the black powder of 2023 is CRAP compared to the black powder of 1973, which is appalling and ABSURD.

MrTwisty 02-21-2023 01:20 PM

2 Attachment(s)
Quote:
Originally Posted by tbzep
Yes, knowing the models will help. Some seem to defy their listed weights, and almost all of them end up heavier than what is listed in the specs.

105g is 3.7 oz. A Big Bertha's catalog weight is 2.2 oz. and is about all a B4-4 or B6-4 wants. I would want completely calm air to make sure it was a 100% vertical flight. An Estes Mercury Redstone is listed at 3.7 oz. and absolutely needs a C5-3 or C6-3. What is the kit that crashed?



.


Rockets in question are ESAM-58 for the 105g (the one that crashed on a B4-4) and the 82g is Red Nova.
I'm wondering if they took the Sasha and made the HL ESAM without any further testing.
Even on a C6 the ESAM is not exactly a high flier, it's nowhere near 800 feet. It's a sub 400 foot rocket, maybe even more like 300.
Pics of my ESAM and Red Nova face cards, Sasha courtesy of the internet.


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