Estes Hyper Bat Exploded

Hello everyone, I'm new here. I have built several single-stage Estes rockets with my son and launched them without any issues. But last weekend we was our first attempt at a 2-stage rocket. I had bought the Estes Hyper Bat and we spent about a week and a half putting it together and painting it in our spare time. For the first stage we used a C6-0 and the second stage was C6-5. We followed the instructions to the letter during assembly but when we launched it, it shot up about 30 feet, spun around in a circle a few times, and then shot straight into the ground and exploded. I don't know what caused the initial spinning but I think the explosion may have been caused by the first stage not properly separating. Then the 2nd stage fired, building up pressure between the two, and then exploding. It seemed a little tight when assembling the two stages together (not super tight) but I thought the 2nd stage would have enough power to push off the first stage.

Has anyone else had issues with 2-stage rockets not separating and exploding like this? Any ideas on the cause?

- Geoff

Hi Geoff,

At midwest power this year, someone flew a hyper bat that did something similar to what you are saying. I don't know the motors used, but clearly it was not flying normally. The two stages should fit together fairly loosely (almost loose enough to have the second stage fall off if you shake the upper stage). This might have been part of your problem, or the design itself is somewhat unstable. What was the wind like?

djs said:

Hi Geoff,

At midwest power this year, someone flew a hyper bat that did something similar to what you are saying. I don't know the motors used, but clearly it was not flying normally. The two stages should fit together fairly loosely (almost loose enough to have the second stage fall off if you shake the upper stage). This might have been part of your problem, or the design itself is somewhat unstable. What was the wind like?

Click to expand...

It was a little breezy but nothing too bad.

The instructions state to tape the 1st and 2nd stage engines together with cellophane tape. Then add about a turn of masking tape in the middle of each engine, but not touching the cellophane tape. Then insert into the rocket. I'm assuming the masking tape is to hold each engine in place to keep from sliding in each stage and the cellophane is to hold the two engines together during assembly so the 1st will ignite the 2nd properly.

This sounds like a normal setup- cellophane tape shouldn't have much holding force, unless there was a strong friction fit between the two stages. The hyper bat has a larger fin shape, so it could be more affected by the wind- it sounds like an unstable design though.

You are correct though that the ignition force on the second motor should separate the motors.. sometimes it does a little more, like my video below where the staging force on my vigilangle knocked the nose cone off, and the rocket kept going:

[video=youtube;BIYYElMU7Aw]https://www.youtube.com/watch?v=BIYYElMU7Aw[/video]

Do you still have the spent motors? Any damage to the rocket? Thinking motor casing burn or a nozzle might of blown out one first stage. 30 feet on first stage is very short.

cobra1336 said:

Do you still have the spent motors? Any damage to the rocket? Thinking motor casing burn or a nozzle might of blown out one first stage. 30 feet on first stage is very short.

Click to expand...

I tossed the motors but kept the pieces. I'll take some photos and post later tonight.

Stagers can be tricky beasties as you've discovered. Can you describe the spinning a little more ? End over end, like a pinwheel or somersaulting, or spinning around the long axis ? Stagers have alot fin area that can catch the wind, even a "little breeze". Also when taping the booster to the 2nd stage engine you really only want 1 wrap with very little overlap. Another thing I've done is use at least a 4 foot launch rod to provide a little more guidance. I've also substituted a 3/16 launch lug for the kit's 1/8 inch lug so I can use a stiffer launch rod.

If you tried to align the fins on the upper and lower stages, that may have caused the instability problem. You see, it is virtually impossible to perfectly align the fins on both stages. Some fins will be in line, but others will be slightly out of alignment and the air will flow over the upper-stage fins and then hit the lower stage fins at an angle and create a large aerodynamic force like an airplane wing flap/vane. This can make the rocket corkscrew but still go "up" or it can make the rocket tumble end over end if there are two fins deflecting the bottom of the rocket in the same direction.

I always interdigitate my multistage fins so the all get clear airflow.

Also, the balsa nose is very lightweight, so if you sanded the fins so much that their size changed or if you added a lot of heavy paint on the back end of the rocket, that could shift the c.g./c.p. to the unstable side.....

There is a reason why the recommended first-flight engine combination is B6-0/A8-5.

The C6-0/C6-5 combination puts more weight in the rear of the rocket. It should not have been unstable with the 2 "C" motors... but your description "spun around in a circle a few times and shot into the ground" - causes me to think maybe it was unstable.

Sadly, Estes has nothing in the instructions about CP or stability to help the average modeler.

samb said:

Stagers can be tricky beasties as you've discovered. Can you describe the spinning a little more ? End over end, like a pinwheel or somersaulting, or spinning around the long axis ? Stagers have alot fin area that can catch the wind, even a "little breeze". Also when taping the booster to the 2nd stage engine you really only want 1 wrap with very little overlap. Another thing I've done is use at least a 4 foot launch rod to provide a little more guidance. I've also substituted a 3/16 launch lug for the kit's 1/8 inch lug so I can use a stiffer launch rod.

Click to expand...

End over end in a forward roll.

Here are some photos of the aftermath:





I did not use the usual black color scheme because we were shooting rockets off in the high desert of Southern CA. I needed something bright to stand out.

Looks like the engine in the booster stage is still there but I cannot dig it out.

- Geoff

Thanks for the info and pictures Geoff. Here are my best guesses:

- the rocket may have been a little tail-heavy and hit a little wind as it left the launch rod that started it tumbling. A longer launch rod and/or a few grams of clay in the nose cone may have helped correct this.

- with motors taped together (only one wrap needed) that grey coupler should have been a very loose fit, only providing some additional alignment between the booster and sustainer. Some binding there for a split second after the 2nd stage lit resulted in the "explosion".

Hope this helps.

BTW it's the prerogative of every rocketeer to change a kit's color scheme !

And welcome to the forum ! Hope your next post will be about a more successful outcome. Since I fly with a club I always recommend that when possible for two main reasons:

- it's fun to see many rockets flying.

- you can take advantage of the accumulated knowledge when prepping a flight and also get some on the spot expert analysis when thing don't go quite as planned.

samb said:

- the rocket may have been a little tail-heavy and hit a little wind as it left the launch rod that started it tumbling. A longer launch rod and/or a few grams of clay in the nose cone may have helped correct this.

- with motors taped together (only one wrap needed) that grey coupler should have been a very loose fit, only providing some additional alignment between the booster and sustainer. Some binding there for a split second after the 2nd stage lit resulted in the "explosion".

Click to expand...

The fitting between the 1st and 2nd stages seemed a little tight to me. And also, it was a bit windy when I launched it. On the same day I launched an Estes Amazon and each time it flew up and then veered into the oncoming wind, almost parallel to the ground.

Thanks for the feedback everyone!

I just went to the Estes website to look up the engine combo's,

https://www.estesrockets.com/rockets/by-engine/007217-hyper-battm

and the suggested first flight for this kit is actually a B6-0 & B6-6. The C6-0 and C6-5 are on the recommended list, and honestly, I would have gone with the some combo first time, since it was ok by the instructions, and you do staging because you want to fly high!

If you built the kit to the letter (and you had a bunch of successful launches before, and what you describe about connecting the motor sounded right), then it should have worked. I really wonder what went on with the upper stage motor...

At this point, my suggestion would be (and I'm not joking) get another kit, and try it again!

Yup, I already ordered one and it will be in my sons Christmas stocking. I also bought him an Estes QCC Explorer and, to jump to the next level, an Estes Ventris.

That's great! It isn't how many times you fall, it's how many times you get back up!

My only other suggestion, after you do everything else, when you prep the model for the flight with the engines & everything, do a "swing test" to make sure it is stable (i.e., the CG and CP are in the proper relationship). What you described doesn't sound that that was really the issue, but, if we can rule that out, then it will be one less thing to scratch our collective heads about.

djs said:

... This might have been part of your problem, or the design itself is somewhat unstable. What was the wind like?

Click to expand...

I gotta jump in here. Several people have questioned if the design is "unstable".

I bought and built my Hyper Bat about two years ago, and if the design IS unstable, then my rocket is the exception to the rule. It flew well, and it performed just as it should have.

I also positioned both the booster fins and the upper stage fins in line, and experienced no problem. I would think if you "clocked" the bottom booster, say, 45 degrees, you might then be cramping the launch rod by a fin. Yes, I know, no two fins are ever in exact alignment.

During final assembly, I have to state that I spotted several errors in the instructions that I called to the attention of Estes. I spoke with their engineer long distance at their dime, for almost 20 minutes one day, and he impressed me with his frankness and attention to my concerns. Together, we reviewed the diagrams and he agreed that the diagrams of trying to glue in the upper motor mount had incorrect drawings. However, some common sense indicated that you could use the coupler and two taped motors together to get the correct "fit" or positioning. (I know I'm not being clear here, but I don't have those plans laid out in front of me.)

Also, there was at least one icon of glue that had come free in the instructions' paste-up before being sent to the printer, and that icon had "floated" over to another page, where it was obscuring a dimension or something minor. (**Remember this!)

In the course of our conversation, the engineer admitted that the entire instruction was going to be undergoing an over-haul because of the need to reprint the "TRI-lingual" short instructions. This would permit them (Estes) to sell in foreign markets. When that happened, they would be catching these errors.

I mention this so that you can check your set of instructions. If they are in 5 languages, you have the new version. However, if you have found the "floating glue icon"**, you can bet that your "following the instructions to the letter" has caused you grief.

All this being said, my personal guess is that your two stages were taped too tightly, as the cellophane wrap should melt through and allow separating very early on.

My first flight was on a B6-0/B4-4 and I'm pretty sure that I did a second flight with B6-0/C6-3 or something similar. I got five flights, two that were 2-staged.

As I recall, the booster stage did separate rather low... (30 feet up maybe?) and was on the ground very quickly, compared to the second stage, which floated down nicely with all further flights.

Hope this helped. And yes, you can find flight reports on www.rocketreviews.com which indicate others have successful flights also!

Here's the direct link to my review, with the specific errors and corrections laid out for you: https://www.rocketreviews.com/hyper-bat-3169.html

Rocket-Geoff said:

The fitting between the 1st and 2nd stages seemed a little tight to me. ...

Click to expand...

I have an Estes Air Commander where the booster coupler fit way, way too tight. I had to sand half the red coloring off the coupler tube before it would fit decent. After reading all this, I may sand it a bit more to be sure. Fingers crossed when I launch it, so far I'm 0 for 2 when it comes to two-stagers...

You could always add a little nose weight to the new you will be building. If you have B motors you might want to try those first.

Its always sad losing a rocket, but I bet you won't forget that launch for quite a while!

Rocket-Geoff said:

On the same day I launched an Estes Amazon and each time it flew up and then veered into the oncoming wind, almost parallel to the ground.

Click to expand...

This was a hint not to launch multi-stagers. The winds over your head may have been a lot stronger than you thought. That might be good practice - launch an overstable single stager first. If it flies straight, go for the two-stage.

Agreed - I use the Amazon as a wind gauge for other rockets sometimes.

Perhaps clubs ought to invest in some sort of scaled down, fully-functional Nike Smoke rockets...

Rocket-Geoff said:

It was a little breezy but nothing too bad.

The instructions state to tape the 1st and 2nd stage engines together with cellophane tape. Then add about a turn of masking tape in the middle of each engine, but not touching the cellophane tape. Then insert into the rocket. I'm assuming the masking tape is to hold each engine in place to keep from sliding in each stage and the cellophane is to hold the two engines together during assembly so the 1st will ignite the 2nd properly.

Click to expand...

"It was a little breezy but nothing too bad." Famous last words.

How breezy was it? How much did the rocket weigh?

A 2-stage rocket can be especially susceptible to aerodynamic stalling in a crosswind due to the "forward" upper stage fins. I've seen many underpowered rockets launched in breezy condition get to 30'-50' above the pad and spin until the motor burned out. If you thought it was "breezy", it was probably to windy to launch the rocket.

Bob

Kirk G said:

In the course of our conversation, the engineer admitted that the entire instruction was going to be undergoing an over-haul because of the need to reprint the "TRI-lingual" short instructions. This would permit them (Estes) to sell in foreign markets. When that happened, they would be catching these errors.

I mention this so that you can check your set of instructions. If they are in 5 languages, you have the new version. However, if you have found the "floating glue icon"**, you can bet that your "following the instructions to the letter" has caused you grief.

Click to expand...

I haven't built many Estes rockets since coming back, but I have found their instructions to be much poorer than I remember in the past. The apparent need to print in multiple languages and have the sheet relatively clutter free seems to have resulted in some confusing/ambiguous instructions in some cases, with a lot of arrows but not much in the way of explaining (or maybe, just flat wrong instructions).

I think it was a Cosmic Explorer; somebody wrote in about having done something wrong on the forum, and when I went to check my instructions, I noticed there was a pink addendum insert that corrected some instructions, that the original poster didn't notice until I pointed it out.

Rather than relying on my fallible memory, I searched and dug up the link...bottom line, maybe the Estes instructions weren't as reliable as we would wish for this kit? Thanks for pointing this out, others will have to double check it...
https://www.rocketryforum.com/archive/index.php/t-121962.html

Usually on a two stage rocket the booster motor is friction fitted snuggly into the motor tube, the coupler between the booster and the sustainer needs to be loose or light friction so that when the cellophane taper burns through the pressure ejects the booster motor which being snugly fitted into the motor tube takes the booster stage with. I had a similar event with the second stage of my Comanche 3.

Email the pics to Estes. Explain what happened.
Looks like motor failure to me from the burn marks.
They should send you a new kit and motors.
PM me for email address.
I have a Hyper Bat on the bench in primer.
It's a pretty small rocket for first flight on C6's
I always shoot a multi stage single stage for first flight.

Woody's Workshop said:

Email the pics to Estes. Explain what happened.
Looks like motor failure to me from the burn marks.
They should send you a new kit and motors.

Click to expand...

I Have to agree. I had thought someone had already suggested this.
With the photos you have, Estes should make this good for you. Their customer service is very good.