Overbuilding

[Neutronium95]

I was just looking at the new issue of sport rocketry, and I found an article about building an extremely strong Estes Guardian. The modifications included:
Quest style shock cord, but with much thicker Kevlar
Wrapping all body tubes with three wraps of 2oz fiberglass
Modifying nose section for altimeter
Fiberglassing the fins on
screwing the nose on to the top section
tip to tip fiberglass on the lower fins
epoxy for all construction
modifying motor mount for Aerotech reloads

This is just crazy. Also because of the excess weight, if it comes in ballistic, it could have the potential to survive and do some damage.

 

[powderburner]

I posted #23 on https://www.rocketryforum.com/showthread.php?t=10016

(It would seem that RoyAtl also agrees with us)

I don't even like seeing this sort of construction on high-power models. Seems like this is the first approach used (knee-jerk?) instead of building something lighter/simpler and finding out if super-building is even necessary. And when you are finished, many of these monsters don't go any higher than a simple low-power rocket because they are too heavy.

I still have that image of the fairly unscathed high-power rocket that speared through the windshield and into the front seat, right next to the driver's seat. Not good.

 

[RoyAtl]

Indeed. I still have memories of the time we lost a field back in 1992 when an under-1lb model rocket, made of a LOC tube and nose, had an ejection failure and fell ballistic *through* the roof of a home (under construction at the time with workers present). The rocket had only a few scratches on it. And that was without any reinforcing.

You're right about the knee-jerk reaction, though I think it is more somewhat of a Tim "More Power!" Allen reaction. It is very true that a lot of early high power failures were shreds or zippers due to tubing coming apart, but some have gone overboard with heavy duty solutions.

I do think that, at some value of mass and density, the point become moot, as the kinetic energy is going to be so great that it doesn't matter if it's made of cardboard or aluminum, it is going to cause some damage to whatever it hits. I still think that model rockets should be built only strong enough for normal flight stresses.

 

[Gillard]

I think i'm somewhere inbetween to the two extremes in this case.
i do nearly always up grade a model kit when i build it, but not massively so.
a better shock cord system with kevlar to me makes sense - i've had a few eleastic cord burn through.
epoxy as a glue is stronger than most glues, ans i do use it on some of the bigger model rockets.
a better motor mount so you have the option of using RMS cases makes sense if the model you are using is known to be underpowered on a C6.

however, i do agree that fibreglassing a small model rocket tube and fins is over kill - and the added mass reduces performance.

for most standard model kits however i use wood glue and with the exception of the recovery system build them stock.

 

[BEC]

Hmmm, I saw that article but haven't read it yet. However, if it really does advocate glassing the whole thing with 2 oz. fiberglass I'd have agree with the rest. This is coming from someone who has enjoyed the benefits of lightly loaded (because they are light) RC airplanes for many years and who has never launched any rocket with anything bigger than a C (though I did do 3-B14 clusters 35 years ago when I was in Jr. High).

Build to fly, not to crash and one gets MUCH better performance and often fewer repairs because lightern not only flies better it crashes less hard.....!

Since I've been BAR'd and gone on a rocket building spree I routinely use a kevlar line attached to the motor mount rather than a three-fold paper shock cord mount, but that's about the extent of any "beefing up" that I generally do.

 

[MarkII]

"Build it to fly, not to crash" as Bernard said, is a great principle to follow at any level of the hobby. I really like that statement.

I haven't even received the issue yet, but I think that if you are constructing your rocket so that it can penetrate steel without breaking, then you are building something other than a sport rocket. And I don't think that I want you coming to my launches. Now get the hell off my field. :hot:

Mark K.

 

[Micromeister]

Ditto:
I've alway built with the idea make them as Lightweight as possible. To FLY better Not crash. Overbuilding is a bane of the hobby. People should strongly discourage these practices whenever we seen them.

Changing the Shockcord mount is not really considered overbuilding i've been using what you referred to as the Quest mount since the mid-70's. It's simply a better method of mounting the shockcord then the old Estes Teabag system and short shockcords which lead to Estes Dent, body rips and recovery system failures. Extremely heavier cords & elastic might be but that I think would depend on degree

 

[foose4string]

I see fiberglassed rockets all the time at our launches on the eastern shore, beefed up fins and recovery systems, etc. Granted, these are high powered behemoths or mach busters, which more often than not, benefit from the extra strength during flight and recovery. The cost of basic building materials goes up too on the larger stuff, and it's nice if something can be salvaged in the event of a crash. I see the benefits. And if I were into high powered rocketry, would probably employ some of these techniques myself.

...BUT, I cringed when I saw the Guardian article this month.
I don't see the point. There is nothing to be gained from this other than several ounces of dead weight. And, why "bullet proof" a rocket that can be rebuilt for a couple dollars worth of cardboard and balsa. The effort and cost of fiberglassing a rocket this small will always exceed the benefits. What a waste of valuable print.

 

[The EGE]

While the article was interesting, and a good reference for me (I'm into small Machbusters), I don't think the Guardian was a good choice. Something like the Big Daddy of executioner that's MPR and able to be up-powered, fine. But the Guardian is small and LPR and doesn't need that.

Heck, my 29mm Sudden Mach will be going to ~500 mps, and it's not getting that much bulletproofing!

 

[Daddyisabar]

I was the only guy launching low power last Sunday when my Leduc met its Waterloo on its third flight when the shotgun ejection charge on the D12-2.01 blew out the internal paper tube and thus failed to pressurize and pop out the nose cone. Of course there ensued a diving aerodynamic whine followed by the obligatory thud as it impacted the soft prairie mud. Upon seeing it stuck in straight up to the French roundel I fell to my knees and cried out in my best Nancy Kerrigan impression “Why, Why, Why?” See pictures below. There in the mud I realized I had a bad case of LOw Power Inferiority Complex Syndrome (LOPICS.) I had a fever and the only cure was more epoxy. As I returned the broken paper corpse to the car I lamented to the others that I could no longer take such damage, and having read the bullet proofing article in Sport Rocketry all my problems would be solved. Boy, did that set off a heated discussion!

I said I was giving up on all the thin balsa, Elmer’s glue, paper and dope. I was finished with the old school techniques and from now on when I walk up to the RSO I can say “dem fins look like glass cause dey is.” Utilizing 21st Century building techniques there will be no more LOPICS, no more shame, and no more damage. I will launch bullet proof rockets in total confidence with more powerful AP motors, higher, faster, and stronger. I can rebuild my low power fleet, I have the technology! Finally I will be cool and hip to the groove of the younger generations, there will be no country for old men. Suddenly the over 50 mid and high power crowd gained a real wave of nostalgia for the old school ways. Both my bullet proofing overtures and the Sport Rocketry article were brutally rejected. While I found the article enlightening and entertaining, they dismissed it as silly and a waste of column space. One even went as far as pulling out an old minimum diameter 24 mm two stager and with one of my D12-0 s in the booster, he sent it out of sight. Well, I still have LOPICS and my Leduc is a file of unrepairable goop. I’m so confused.:confused2:

 

[luke strawwalker]

I was just looking at the new issue of sport rocketry, and I found an article about building an extremely strong Estes Guardian. The modifications included:
Quest style shock cord, but with much thicker Kevlar
Wrapping all body tubes with three wraps of 2oz fiberglass
Modifying nose section for altimeter
Fiberglassing the fins on
screwing the nose on to the top section
tip to tip fiberglass on the lower fins
epoxy for all construction
modifying motor mount for Aerotech reloads

This is just crazy. Also because of the excess weight, if it comes in ballistic, it could have the potential to survive and do some damage.

Agree... and why they print stuff like that I'll never know...

I've seen plenty of overbuilt stuff without having to encourage it... in fact I've seen WAY more overbuilt stuff compared to underbuilt... WAY WAY more...

Later! OL JR

 

[luke strawwalker]

"Build it to fly, not to crash" as Bernard said, is a great principle to follow at any level of the hobby. I really like that statement.

I haven't even received the issue yet, but I think that if you are constructing your rocket so that it can penetrate steel without breaking, then you are building something other than a sport rocket. And I don't think that I want you coming to my launches. Now get the hell off my field. :hot:

Mark K.

I LIKE THAT!!!

As a field owner, I most assuredly agree!

Safety is a big issue with me... ya don't want to be a mother hen about it and drive everybody nuts, but there are certain things that raise red flags... Thank goodness our farm is located too close to adjacent houses and stuff for HPR, because I've seen WAY more HPR FUBAR's than LPR... and your right, the more massive the more kinetic energy on impact-- material strength is a little less important, but still-- I'd rather be hit by balsa than hard plastic or fiberglass!

Of course VELOCITY is the biggest determinant of impact force, since energy squares as velocity doubles...

Anyway, overbuilding, to me, is just sloppy work-- ANYBODY can make stuff "battleship tough" but that's not the point, especially in rocketry (or aught not to be, IMHO!)

Later! OL JR

 

[spacecadet]

Speaking as someone who thinks twice about going from typing paper to cardstock, I have to agree. Most of my rockets won't survive a downpour, let alone an impact. Though the heavier designs might get a dusting of Scotchguard spray to protect the ink (paint being too heavy).

 

[GregGleason]

The one day I attended NARAM 49, I was walking around the approved spectator area, minding my own business, and felt something hit me. I looked around trying to spot the "wise guy" but didn't see anyone. I finally looked around on the ground and discovered a piece of a rocket that had shredded not very long before I got hit. I can't imagine (and don't want to imagine) what it would be like to be hit full on with an intact rocket.

Greg

 

[ScrapDaddy]

While the article was interesting, and a good reference for me (I'm into small Machbusters), I don't think the Guardian was a good choice. Something like the Big Daddy of executioner that's MPR and able to be up-powered, fine. But the Guardian is small and LPR and doesn't need that.

Heck, my 29mm Sudden Mach will be going to ~500 mps, and it's not getting that much bulletproofing!

I too am also Into small machbuster(s)(one is on the way) (even smaller then the ones THE EGE is into I like 18mm ones they are light on your wallet)(they have all had their madien flights on 1/2A6 motors but their mach attempt flight is still pending) however before I saw TRF I was suffer from the oppiste problem jk when I built my 1st machbuster I did nothing out of the usual except add epoxy clay fillets and paper skins, my second one was planed to used G10 Fiberglasg fins in a double delta with a root reducer and I was going to use a fiberglass nose cone :y: then..... I saw this thread (looks like I'm sticking with balsa after all)
well anyway back on topic
using fiberglass in estes kit is absurd! And epoxy throughout the entire build? I always build my estes kits with wood glue (even white glue works) and I had never had a structural failure in flight except during the one flight in my estes star Stryker where the fin shreaded off because I used a D21 and the glue was still wet.... And to use any of these construstion methods on the estes Guardian Which is SUPPOSED to recover on a 12inch parachute makes it even more obserd he would have to try to Use a 18" parachute.....


Pre-PS isn't it better to overbuild then under build?

PS are you sure it wasn't just an April fools prank?

 

[MattieShoes]

The only time I've had a fin come off, it was on an estes kit using epoxy! As far as I can tell, it came off in flight too. Something must have been up with the epoxy. Luckily, it was a Viking, so it had four more fins left to keep it stable

 

[DAllen]

This article is a clear indication that instead of "bullet-proofing" our rockets we need to work on recovery. Before doing doing all of this "bullet-proofing" you need to consider why you would need to do this extra work during for a normal flight. I don't think it is wise to try to build a rocket for every possible contingency.

When I hear someone say, "My _____ survived a free fall from a buh-zillion feet up 'cause it was CF wrapped in 10 layers of 6 oz. glass blah blah blah."

My first thought is, "You need to work on your recovery issues."

I could see doing all that extra work on that Guardian IF you are recovering on hard ground and are using a streamer instead of a chute.

-Dave

 

[Micromeister]

Couldn't agree with you more Dave!
If folks paid more attention to their recovery systems..and motor/model selection. they'd never have to over-build anything. Shockcord anchor systems and recovery system attachments really are not all that difficult if we really design properly

ScrapDaddy: Machbusters have been around and designed using STANDARD mod-roc materials since the mid 70's. G10 isn't necessary nor is CF reinforcement. Proper fin design, alignment and motor selection is all that's necessary. Never understood the fasination with machbusting??? you can't see them or hear it so what's the point? seems more a waste of time,effort and perfectly good money that could but used on something you can actually see and reuse LOL!!!!

Again as dave so well put it in his post. If folks paid more attention to their recovey methods and issues they'd have no need for over-building.

 

[Neutronium95]

Just a quick addition to the fin attachment: three layers of 2oz cloth, that are tip to tip.

 

[WiK]

I don't get SR any more, so haven't seen the article, but what size motor mount was used for the modified Guardian? I'm having trouble thinking of any motors that'll fit in the rocket which would require so much glass...

Phil

 

[dedleytedley]

I suppose I could be accused of over-building as I often reinforce my surface mount fins. I use an OPEN weave fiberglas wall repair tape from tip to tip with glue brushed on top for my BT-80 based MPRs. In a free fall they'll take some damage but the fins won't completely detach. I'm sure my flying skills could use some improvement but despite my best efforts occasionally there are recovery problems. After spending many hours building and finishing a rocket I'd like it to stay pretty for a few flights at least. Ted

 

[Micromeister]

I suppose I could be accused of over-building as I often reinforce my surface mount fins. I use an OPEN weave fiberglas wall repair tape from tip to tip with glue brushed on top for my BT-80 based MPRs. In a free fall they'll take some damage but the fins won't completely detach. I'm sure my flying skills could use some improvement but despite my best efforts occasionally there are recovery problems. After spending many hours building and finishing a rocket I'd like it to stay pretty for a few flights at least. Ted

The Trick then Ted:
Is to spend as much time on the Shock Cord Anchor or System and other parts you don't see as the parts you DO see. Then you'll no longer have to worry about things staying together or need to spend as much time adding stuff to the outside other then making it pretty

 

[Neutronium95]

WiK- there was no motor mount upgrade, it was just flown on c and aerotech d motors.

 

[MarkII]

I suppose I could be accused of over-building as I often reinforce my surface mount fins. I use an OPEN weave fiberglas wall repair tape from tip to tip with glue brushed on top for my BT-80 based MPRs. In a free fall they'll take some damage but the fins won't completely detach. I'm sure my flying skills could use some improvement but despite my best efforts occasionally there are recovery problems. After spending many hours building and finishing a rocket I'd like it to stay pretty for a few flights at least. Ted

Yes but the issue isn't about adding some fin reinforcement to a 2.6" diameter mid-power rocket, but rather about beefing up a BT-50 sized low power rocket so that it can penetrate steel.

Mark K.

 

[ScrapDaddy]

ScrapDaddy: Machbusters have been around and designed using STANDARD mod-roc materials since the mid 70's. G10 isn't necessary nor is CF reinforcement. Proper fin design, alignment and motor selection is all that's necessary. Never understood the fasination with machbusting??? you can't see them or hear it so what's the point? seems more a waste of time,effort and perfectly good money that could but used on something you can actually see and reuse LOL!!!!

Well its on my bucket list, might as well get it out of my way, an I know not to use G10 on a machbuster,as weight means everything, I was going to use it on my E,F,G powered heli recovery model (development stage)

 

[cjl]

Honestly, there's almost zero reason for G10 until H motors at least (I say almost because there are certain limited cases in smaller stuff where ultrathin G10 is preferable). Balsa, basswood, and thin plywood are more than adequate for G motors, even in machbusters.

 

[ScrapDaddy]

You do relize I said I am NOT using G10 in my machbuster

 

[cjl]

Yep

I suppose you could use extremely thin CF/G10 if you wanted - I've done that before with a G80 powered machbuster, but it wasn't because balsa would be insufficient. It was because a CF fin could be thinner, and therefore the drag was slightly lower.

 

[Pat_B]

I think that making rockets for competiton can teach folks a lot of things about how light weight you can go and still have a rocket that will survive a flight. I spend the majority of my rocket building time building rockets that weigh around 5-7 grams. That helps with the realization that many of our material choices have more strength than what's needed to begin with.

I cringe when I see articles like the one in SR because it's totally unecessary. How far off do you need to be on your motor choice so as to worry so much about a zipper that you have to glass a tube on a small model rocket? There's more to flying rockets than just what happens at the field. More time needs to be spent simming a flight and determining the proper motor choice so as to make these bulletproof construction techniques unecessary.

NAR is also placing an emphasis on HP rocketry at the expense of LP and these sort of articles are going to be more common in the future.

As an aside, I'm building a kit for my L1 cert and find it astonishing how many times epoxy is recommended all over the place when yellow glue is still stronger than the materials it bonds. Heck, if yellow glue can be used to build furniture that people sit on then it sure in the heck can easily handle 40-50 lbs of thrust from a rocket.

 

[cjl]

As an aside, I'm building a kit for my L1 cert and find it astonishing how many times epoxy is recommended all over the place when yellow glue is still stronger than the materials it bonds. Heck, if yellow glue can be used to build furniture that people sit on then it sure in the heck can easily handle 40-50 lbs of thrust from a rocket.

Absolutely. When bonding paper to paper or paper to wood (or wood to wood), standard yellow wood glue is more than enough. Epoxy should only be used when the materials are such that wood glue would not stick properly (such as phenolic or fiberglass).