Is overbuilding turning into a thing we should reconsider?

[Bat-mite]

One thing I find a bit annoying is when I see a more "experienced" rocketeer telling a newb that they should replace their rubber shock cords with kevlar, and toss their plastic chutes and get nylon, etc...on low or low-mid Estes rockets, or similar.

I don't do this, and I don't consider it my business to "inform" or "correct" other rocketeers (except my kids) on how to enjoy the hobby. However, I want to ask a question regarding this post.

When you use the word "should," it brings to mind someone who is overbearing, who delights in showing other people how much he knows. Someone once told me that there are two types of people in the world -- knowers and learners. Knowers talk more than they listen, and respond to any topic by telling you what they know, rather than listening first to see what you know, and asking questions.

I find this to be very different from someone who sees a less experienced rocketeer struggling, and casually says, "Hey, you might want to consider _______. That has worked well for me."

Are we agreed on that?

 

[burkefj]

In my opinion for a lot of highpower that I do, cardboard is overkill even, don't get me started

Frank

 

[Tyler P]

I don't do this, and I don't consider it my business to "inform" or "correct" other rocketeers (except my kids) on how to enjoy the hobby. However, I want to ask a question regarding this post.

When you use the word "should," it brings to mind someone who is overbearing, who delights in showing other people how much he knows. Someone once told me that there are two types of people in the world -- knowers and learners. Knowers talk more than they listen, and respond to any topic by telling you what they know, rather than listening first to see what you know, and asking questions.

I find this to be very different from someone who sees a less experienced rocketeer struggling, and casually says, "Hey, you might want to consider _______. That has worked well for me."

Are we agreed on that?

Oh, most definitely agreed! If it was done in the way you describe, it changes the tone completely. There was really nothing wrong with the person offering the advice, but more in the way he did it. I like to see a more nurturing approach to the hobby. Unless someone is clearly doing something unsafe, what business of it is mine?

I'd like to consider myself a learner. I've learned a tonne so far just hanging out here and watching build threads. Having not ventured past mid-power myself (L1 attemp in the Spring), I've picked up many good tips and I've only been "told" what to do by one person.

Working in retail hobby business, I deal with a lot of "knowers" every day, haha! Anytime you can share a bit of personal experience of what has worked and what has not worked, it feels good. I find the biggest part of that is sharing the 'why' portion of it. The person can make their own decisions from there.

I guess my original post didn't completely address the original topic. I like to think I build to what I need. Like had been stated earlier about RC airplanes, I build to fly, not to crash. Coming from the RC plane world, I see a lot of people doing things like reinforcing landing gear plates before they fly the plane. Learn to land properly, and that doesn't need to be done! Same thing applies with rockets, I think. Sim your flight, plan your recovery properly, and don't over-motor a build, your rocket should survive. If you have some sort of snafu with your recovery, there's really not much you can do to save the rocket at that point, lol.

 

[dr wogz]

I've only been "told" what to do by one person.

that wasn't me I hope!!

it is one thing to offer advise, when advise is warranted or asked for. Its another to imply a change should be made based on personal experience, on a comment not really looking for advice..

 

[Tyler P]

that wasn't me I hope!!

it is one thing to offer advise, when advise is warranted or asked for. Its another to imply a change should be made based on personal experience, on a comment not really looking for advice..

LOL, nope, but you advised me to take said person's advice with a grain of salt...

...and if you 'told' me what to do, I'd probably listen, knowing that you know what you're talking about!

 

[AfterBurners]

Yes I think a lot of us do overbuild to extremes! I do know it is personal preference how one decides to build, but I guess you have to determine what it is you want from the rocket you are building. Is it low and slow or high and out of sight? For me I tend not to over build. When I get a kit I tend to stay to the original design and concept and replaced inferior parts, like cheap shock cords and sometimes chutes, but not always and upgrade the motor retention. If I use internal or external fillets I don't glob loads of epoxy inside the fin can, because you really don't need it. The most I would use are moderate fillets and then maybe foam the fin can if needed. believe the lighter the rocket is the better it will fly and cause less damage upon landing under chute. I try not to use heavy duty hardware, thick monster fillets and thick plywood rings, of course there will be times when you may want to use this type of building, but for MPR and HPR L1 type rockets say 4" or less nah I can't see it.

 

[Sooner Boomer]

Estes Flying Colors, 3oz bt60

https://www.estesrockets.com/rockets/arf-almost-ready-to-fly/002486-flying-colorstmView attachment 375172

If only it were really full of candy!

 

[Sooner Boomer]

I've built a lot of stuff right up to the edge of high power using cardboard, balsa, and yellow glue. I'd build for bigger motors, except I'm not certified at any level. I've used kevlar, 1/4" braided line, for recovery leader, because I was given several pieces of "mule tape" that was used to pull network cable. If you know what you're doing, you don't have to go with superman builds. Most of the time, yellow glue is as strong (if not stronger) than the materials you are bonding together. The only reason I use epoxy right now if when assembling components that slip together and yellow glue could "grab" at the wrong time.

Now you young kids get offa my lawn!

 

[TALON]

When I was a BAR 8 years ago, I was on the net absorbing all the info I could get! It was fantastic all the info I could get! (opposed to only being able to stare at an Estes Catalog until the print came off, circa 1967). I absolutely over built (because of all the new [to me] info). I had an Estes Phoenix kit that I had for 20 years. I decided to build it to use 24MM AP motors w/ an Aeropack retainer. Since I was using JB Weld w/ the retainer & that wood glue could deform the BT and the "grabbing problem, I decided to use the JB on the motor mount, centering rings and when attaching/inserting to the BT. Reading all the info on the Apogee web site, I also gusseted the centering rings and built an anti-zipper harness with braided kevlar! I also created epoxy rivets by poking holes in the BT and the fin roots and applying the JB. I used Titebond molding glue for the fillets. And of course, I papered the fins.
I think that would qualify as overbuilt. It never flew and met its end in an accident during painting.

I will still use JB Weld on motor mounts, I use Kevlar for a leader for the shock cord. The leader is usually attached to a centering ring. Snap swivels to attach the chute. I still make rivets but with TB wood glue w/ double glue joint and TB molding for the fillets. I will use Aeropack retainers when applicable and BSI epoxy for internal fillets. IMHO this is reasonable overbuilding, like airplanes before computers, they were designed 15% more that stated!

 

[jlabrasca]

Well talking about a ballistic entry weight has no effect on velocity: the gravity constant of 9.8m/s per second, until terminal velocity or impact.

Estes Flying Colors, 3oz bt60

https://www.estesrockets.com/rockets/arf-almost-ready-to-fly/002486-flying-colorstmView attachment 375172

Because I already did most of the work while indulging my pedantic priggishness elsewhere on the forum and, because you can't spell "pedantic prig" without O-C-D, I tried to work out about how fast that Flying Colors might have been moving when it hit the roof of the trailer.


Making some guesses about the drag coefficient and the density of air on the day, and using the numbers from the Estes catalog page for the mass of the rocket and the maximum height from which it might fall, I get values between 26 m/s and 40 m/s (58 - 105 mph) depending upon the drag coefficient.

The dashed lines are computed values for a rocket massing 20 grams more than Estes' estimate. Using OpenRocket's mass densities, this is just about what you'd get if you substituted CF for the paper body tube (with the same wall thickness as the Estes paper tube).

Of course, thats also assuming that it falls from rest through still air of uniform density (as opposed to nosing over and starting downward under thrust in thin air, or encountering some vertical current in the air column as it falls, etc.)

If anybody wants to check my math



The behavior of the big drag rocket is pretty interesting. Increasing the mass by 25% doesn't increase the terminal speed very much, but it gets up to speed in a much shorter distance. I don't think I made an arithmetic error (if I did, I made it both when I entered the equation into the graphing app and when I worked the impact roof-impact speed by hand).

EDIT: Spotted my error, but the editing window will close before I will be able to fix the plot. Terminal speed for the 80 gram rocket and a drag coefficient of 0.3 should be 47 m/s. Which means it would have hit the roof at about 38 m/s (85 mph).

EDIT [2]: Didn't take as long to fixit as I thought.

 

[jlabrasca]

EDIT: Spotted my error, but the editing window will close before I will be able to fix the plot. Terminal speed for the 80 gram rocket and a drag coefficient of 0.3 should be 47 m/s. Which means it would have hit the roof at about 38 m/s (85 mph).

EDIT [2]: Didn't take as long to fixit as I thought.

... one more try. I updated the numbers on the plot, but screwed them up in a different way in the text of the post.

For my own -- very fragile -- peace of mind: I got a range of 38 m/s (Cd = 0.6) to 47 m/s (Cd = 0.3) when the rocket has fallen through 190 meters.

 

[Hooked On Rockets]

Hi Folks!...
Just a newbie here, but I want to say that YES, I do overbuild....
I got a couple of kits almost a year and a half ago and didn't know much about anything with rockets.
**I couldn't imagine that a paper tube with fins and a nosecone could not self destruct with only "elmers" holding it together! LOL
I read the directions (and I hadn't yet discovered this site) and I used epoxy on a couple of Estes Pro 2 series kits that said "use carpenters glue".
I also used a short section of coupler tube (cut to .2 to .25") glued to the body tube ahead of the top CR to reinforce the "glue bond" along with a fitting section underneath the CR epoxied to the MMTube. My thought was again, see above **.
I absolutely considered weight vs. strength, I chose strength.
I discovered Open Rocket and worked up the weights of the parts and it probably would go higher without epoxy, but I also have this mentality that "I could put a bigger motor in this puppy".

Now that I've built a few small kits, I still want to "put a bigger motor in this puppy", so I continue to overbuild.
I started an Estes V-2 kit, I installed a 29mm MMTube, working it up on OR I discovered that I needed a longer bodytube, which I bought (18"),
I discovered that it also needed 3ish oz of noseweight with the longer BT to keep the CG/CP in order.
Come to learn (from this website) that the balsa fins probably wouldn't hold up....so I'll probably have to glass the fins/boat tail.
I don't mind that because that will give me experience doing something I haven't done before.
Will it be stabile??? I don't know, gotta glass it and weigh it.
But it WILL be overbuilt!
It WONT look like a V-2 either...but it will be a learning experience.

I've been working on a Loc 4" Goblin and I still used the reinforcement sections of coupler tube to strengthen the MMT to BT, My mind says it don't need it but my heart says make it tough.

Don't get me wrong, when I got my rocket kits as a gift and started looking on the net, I considered them to be like a disposable lighter...actually more like a wooden match...you may only get to light it once!!!
No matter how pretty they are!
LOL

Thanks!
SS

 

[hball55]

I bought a fiberglass rocket kit and the nosecone was tipped with aluminum that was so pointy that it punctured the skin so easily that it scared me. It was a weapon, so I took my dremel tool and took the point off. Still, I have no doubt that if it came in ballistic, it would penetrate the roof of any car. I am a firm believer in putting tilt on the launch rail so that it never will come down near spectators. I'll just have to walk further to retrieve it, and my legs aren't what they used to be.

 

[kevindcornwell]

I only got back into rocketry and got into HPR a couple years ago, so I still think of myself as a newb. In that time, however, I've come to feel like there's an emphasis on building in excess of what is actually required for most people.

Fiberglass, carbon fiber, 30-minute epoxy with fillers, 2-part expanding foam, brick shithouse fin cans, aluminum-tipped FWFG nose cones, etc. What percentage of launches actually *require* that kind of construction?

If you're breaking Mach 2, exceeding 50 Gs, touching the edge of space, trying to punch a hole in a tank, etc. I get it. But who is?

Should we take a step back and focus more on "cardboard, plywood, and Titebond or five-minute epoxy will be fine unless you're doing crazy X thing?"

I'm just spitballing here based on personal observations. Personally in the last year I've built some stupidly heavy rockets and now I'm wondering "why?"

Since then I've become much more enamored with "light, cheap, and sufficient" for a given thrust. The minimum construction required seems like a much more interesting problem than just "go bigger and heavier than you think you need."

It has always seemed illogical to me to build a recovery system with 750lb forged swivels and 1000lb kevlar for a 5lb rocket. Given that the Apollo had some specs that ran within 5% of design maximums, I find it a far greater and more interesting challenge to engineer solutions that use clever over brawn. If Apollo did it, then so can I. But that's just me. Do my rockets sometimes fail? You bet. And each time, I learn some more. The greatest fun at rocket shoots is to see how the rest of you did it. So many opportunities to learn something new to build a better (safe and efficient by design) rocket. And now to toot my horn: I built two identical rockets for my lvl 2 effort. Sim weight was in the 2800g range. When finished, both were within 2g of each other and 6g of the sim weight (CG was dead on). To the OP, I find careful planning and execution to be more effective than overbuilding. Recognizing that every decision comes with its own unique set of compromises.

 

[cbrarick]

I still get grief when I show up with my LOC Hi-tech "Woody" just because there's nothing other then wood glue. Flys fine, everything stays together. A little research with the tight-bond site and a conversation with Jeron even steered me to the tight-bond for the retainer.
It was a fun project and definitely not overbuilt It's even fillet-less...gasp.....

 

[cwbullet]

I still get grief when I show up with my LOC Hi-tech "Woody" just because there's nothing other then wood glue. Flys fine, everything stays together. A little research with the tight-bond site and a conversation with Jeron even steered me to the tight-bond for the retainer.
It was a fun project and definitely not overbuilt It's even fillet-less...gasp.....

Nothing wrong with wood glue, but I wouldn't use it on a level 3 project.

 

[jlabrasca]

Nothing wrong with wood glue, but I wouldn't use it on a level 3 project.

Challenge accepted!

Oh. Wait. $300+ for a reload...

One of the contests at last years NXRS involved launching stock PSII rockets on high power loads. In correspondence between some of the folks in the club afterwards -- on the news that the PSII kits were fading away -- there was talk of running a follow-on contest as a kind of Pinewood derby. Give everybody the same kit, restrict the adhesives to wood glue and CA, allow only deletions without substitution from the supplied/allowed parts, etc.

The conversation didn't go very far. There is not an easy or obvious way to translate a formula like "block of wood + nails + plastic wheels" to rocketry. The biggest problem with the idea was coming up with something to measure to determine a winner. If you are trying to see who can build a rocket that won't shred when attempting highest apogee, largest impulse motor, greatest maximum acceleration, etc -- some of the rockets are going to shred.

Hi Folks!...
Just a newbie here, but I want to say that YES, I do overbuild....
I got a couple of kits almost a year and a half ago and didn't know much about anything with rockets.
**I couldn't imagine that a paper tube with fins and a nosecone could not self destruct with only "elmers" holding it together! LOL

Thanks!
SS

Hi SS. Welcome to the we-burn-money-to-launch-rockets-at-nothing club.

"Overbuilding" has a couple of different meanings. What you are describing, is hardening a rocket -- so that it will stand up to greater stresses.

Folks tend to overestimate the kinds of stresses that will develop during the thrust phase of the flight, and it isn't always obvious which parts of the rocket need to be made stronger to launch on motors with higher impulse or higher maximum thrust.

A rocket built tougher for the going-up part of the launch is also a tougher and heavier projectile in the event of a recovery failure (or a rocket going sideways under thrust).

 

[cwbullet]

Challenge accepted!

Oh. Wait. $300+ for a reload...

One of the contests at last years NXRS involved launching stock PSII rockets on high power loads. In correspondence between some of the folks in the club afterwards -- on the news that the PSII kits were fading away -- there was talk of running a follow-on contest as a kind of Pinewood derby. Give everybody the same kit, restrict the adhesives to wood glue and CA, allow only deletions without substitution from the supplied/allowed parts, etc.

The PSII rockets are great mid to lower high power kits. I have seen many of them fly on Hs and Is. These small kits on wood glue are vastly different than an M or N powered rocket. I did not say it was impossible. I said I wouldn't use it nor would I recommend it. Then again, I have seen several level 3 rockets cleaned off the field due to poor bonds and too much thrust that were prepared with epoxy.

A rocket built tougher for the going-up part of the launch is also a tougher and heavier projectile in the event of a recovery failure (or a rocket going sideways under thrust).

There is a fine line in making it safe. I would say a heavy rocket is no more dangerous than a light rocket that flys apart in flight and litters the field with parts. It is much easier to dodge a single part then 10s to 100s.

 

[jlabrasca]

There is a fine line in making it safe. I would say a heavy rocket is no more dangerous than a light rocket that flys apart in flight and litters the field with parts. It is much easier to dodge a single part then 10s to 100s.

I am pretty sure I disagree with that statement. Excluding the really big stuff that flies from the away cells; divide a typical HPR rocket into 10s or 100s of parts as it disintegrates under thrust. Most of the parts will be low-mass and not particularly aerodynamic. The parts that you would need to dodge are going to be the stable and low drag parts (the nose cone) or are dense enough that the drag forces are small compared the other forces acting upon them (weight for stuff just falling off the rocket, weight+thrust for the motor).

A rocket that loses just one fin and goes sideways towards the gallery under thrust, OTOH, is a scary prospect. Likewise a motor that blows through the top of the airframe, or a that blows out the back at ejection... lots of very good reasons to strengthen parts of a rocket.

And I seriously was not suggesting trying to cert. L3 on a paper and balsa rocket (although I really like the idea of somebody smarter than me trying it). <smile>

 

[cwbullet]

There are multiple ways to look at it. My point is I would rather have a heavy single rocket coming in under control or even ballistic than a bunch of parts coming in.

 

[Hooked On Rockets]

Hi SS. Welcome to the we-burn-money-to-launch-rockets-at-nothing club.

LOL...Thanks for the welcome! I have a few bills and plenty of matches!!!


"Overbuilding" has a couple of different meanings. What you are describing, is hardening a rocket -- so that it will stand up to greater stresses.

Exactly, just what I consider when I build, weight vs. motor vs. can I put a bigger motor in this pup vs. IS IT SAFE???

My thought is that it's a bit safer to have a failure on decent with a recovery failure, which you MAY have enough time to get out of the way as opposed to a "powered up" failure that you may not have enough time to get out of the way of.
I've been looking at the post with an "R" build, that thing is amazing and SCARY!!!!
I would much rather have to duck from its freefall instead of it breaking loose from its "rocket container" going "full-tilt-boogie"
I'd be scared to mount that to my JEEP...let alone something that's just pointed at the sky.....
But MAN...that Thing is AWESOME!!!!! 7½ feet tall MOTOR CASE!!!!

As CWBullit Says:


There is a fine line in making it safe. I would say a heavy rocket is no more dangerous than a light rocket that flys apart in flight and litters the field with parts. It is much easier to dodge a single part then 10s to 100s.[/QUOTE]

I totaly agree

P.S. Not sure if I've figured out the quote process here....if not, My Apologies...

SS

 

[Hooked On Rockets]

Apparently I haven't figured it out....Jeez.....the quotes I quoted didn't work this time!
Head slap!!!!

 

[Steve Shannon]

Apparently I haven't figured it out....Jeez.....the quotes I quoted didn't work this time!
Head slap!!!!

The easiest thing is to just click on “quote” when replying, but if you want to do it manually you need a quote tag at the beginning and an end quote tag at the end. The beginning tag is just “quote”, except replace the quotation marks with square brackets.
The terminator or end quote tag has a forward slash after the left side square bracket.

Like this

 

[jlabrasca]

Exactly, just what I consider when I build, weight vs. motor vs. can I put a bigger motor in this pup vs. IS IT SAFE???

My thought is that it's a bit safer to have a failure on decent with a recovery failure, which you MAY have enough time to get out of the way as opposed to a "powered up" failure that you may not have enough time to get out of the way of.

Look up thread to the math I (almost) did in post #70

That was for a light-weight Estes rocket falling nose down.

The "Flying Colors" is 53 cm long by 4.1 cm in diameter. At an altitude of 190 meters, as it turns over at apogee and is perpendicular to your line-of-sight, it will present a visual angle of 0.15°. (Assume clear skies and no glare from the sun, a young person with good eyesight can just see something that subtends an angle of 0.02°).

But it is only going to be as large as that in your visual field at apogee. After it makes the turn, it will present a much smaller profile to folks looking up. For the folks standing closest to its path of decent it will be invisibly small until it is within 120 meters -- about 2.3 seconds before impact.

And, of course, that assumes you were following the flight up and have a view of the sky not obstructed by your EZ-up when you hear someone call "Heads Up!"

P.S. Not sure if I've figured out the quote process here....if not, My Apologies...
SS

The forum uses BB code. There should be a button or a link somewhere at the bottom of the post to "reply" (which quotes the post to which you are replying) or "quote" (which banks quoted text with the BB tags in a buffer so that you can then insert them by closing "insert quotes")

EDIT: Seriously just sat back down at the computer to check the weather for tomorrow. I have paying work to do and chores and a dog to walk and a family ... plus which I am way too bugged by the mis-transcriptions in the derivation of the speed versus altitude equation that that I spent way too long type-setting...

edit [2] SERIOUSLY -- I have got to stop trying to do arithmetic in front of you people! 2.3 seconds, not 0.23 seconds.

 

[Ez2cDave]

Over-building causes more problems than it solves . . .

Dave F.

 

[Ez2cDave]

I only got back into rocketry and got into HPR a couple years ago, so I still think of myself as a newb. In that time, however, I've come to feel like there's an emphasis on building in excess of what is actually required for most people.

Fiberglass, carbon fiber, 30-minute epoxy with fillers, 2-part expanding foam, brick shithouse fin cans, aluminum-tipped FWFG nose cones, etc. What percentage of launches actually *require* that kind of construction?

If you're breaking Mach 2, exceeding 50 Gs, touching the edge of space, trying to punch a hole in a tank, etc. I get it. But who is?

Should we take a step back and focus more on "cardboard, plywood, and Titebond or five-minute epoxy will be fine unless you're doing crazy X thing?"

I'm just spitballing here based on personal observations. Personally in the last year I've built some stupidly heavy rockets and now I'm wondering "why?"

Since then I've become much more enamored with "light, cheap, and sufficient" for a given thrust. The minimum construction required seems like a much more interesting problem than just "go bigger and heavier than you think you need."

Agreed . . .

My nomination for the most over-used building material is All-Thread !

Here is a prime example . . . An "H"-powered rocket, built by a guy from MIT . . . What the Hell is MIT teaching people, nowadays ?

https://web.mit.edu/mouser/www/rocketry/fleet/nerdmagnet/

QUOTE :

"The bulk of the construction took place at the MIT Hobby Shop with lots of good advice from Ken Stone and Roy Talanian, as well as copious amounts of entertainment from Q while I was waiting for epoxy to cure.

END QUOTE :

https://studentlife.mit.edu/hobbyshop

"The MIT Hobby Shop is a fully-equipped wood and metal shop that teaches students the art of thoughtful design."


Dave F.

 

[lakeroadster]

As a retired Engineer I worked for the most part in fabrication shops where we built everything with a 3:1 Safety Factor. But I did work a couple years in Aerospace, where Safety Factors were nearly 1:1.

I like building things "Hell-For-Stout". And that's how I build my scratch built rockets. Altitude doesn't mean much unless you are in a competition, I'd rather be able to launch a rocket 50 times and enjoy it... verses once or twice and watch it shred itself.

It's an exhibition... not a competition. Please... no wagering

 

[DaveW6DPS]

Why is use of epoxy conflated with "overbuild"? A light application of epoxy can be stronger and lighter than an average application of wood glue!

There are a variety of adhesives that are suitable for low power rockets. Epoxy is one of them, with few disadvantages.

I still have not seen anyone come up with a workable definition of "over-built".

I have seen many mishaps caused by "under-building", many mishaps caused by stability problems, and many mishaps caused by failure to deploy a recovery system. All of these can be exacerbated by not aiming the rocket away from the people.

I am still waiting to see a problem caused by "over-building".

 

[Ez2cDave]

Why is use of epoxy conflated with "overbuild"? A light application of epoxy can be stronger and lighter than an average application of wood glue!

Dave,

I think what is often referred to as "over-building" with Epoxy is when, for example, builders pour "wells" of Epoxy between fins inside fin cans ( not "pre-fabbed" fin cans ).

Dave F.

 

[DaveW6DPS]

Dave,

I think what is often referred to as "over-building" with Epoxy is when, for example, builders pour "wells" of Epoxy between fins inside fin cans ( not "pre-fabbed" fin cans ).

Dave F.

Who would do that? It just adds weight and nothing of value.
I got the impression from some posts that just using epoxy rather than other glue is "over-building".

A rocket coming in ballistic is a recovery failure, no matter how much it weighs.
An unstable rocket is an unstable rocket, no matter how much it weighs. In fact, lack of adequate nose weight when needed is a serious stability issue.
A rocket that shreds during boost is either over powered or under-built.

I still have not seen a good definition of "over-building".