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firemanup

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It's my opinion when looking at my own builds and those of others that we often overbuild our rockets.

In my own case I know it's because I don't have the knowledge base yet to know what it really takes for the different parts of a build to hold together under higher stresses, so I play it safe and overbuild.

We've seen plenty of info on beefing up rockets and the things we can do to accomplish this.

So in an attempt to learn more about the minimums necessary lets post some info, those of you with more experience and flights, what are the stats on some of your birds that you didn't think would handle a motor yet they did, or what are the stats on your lighter birds that you feel that you pushed the limits on.

I'd like to see what the lightest build is on a rocket that's pushed mach, maybe .9 mach or higher and/or whithstood some serious G's.. let's say 25 G's or higher.

So in other words who got the most performance with the least amount of re-inforcements, really pushing the limits of components.

Some things that would be of interest to me on the builds would be, construction techniques of the fin can. Built outside or inside of the body tube. Tip to tip glassing? if so what weight, glass only on fillets, epoxy used, 15min 30min etc.. epoxy additives micro balloons, milled glass...

Body tubes, glassed or no....? How many centering rings, allthread re-inforced?

Diameter of rocket and number of fins and fin material.. etc..

The information that would help some of us to understand what the minimum is, that's really needed to handle a high speed high thrust flight.

I'm curious what's really needed to push the envelope..
 

lalligood

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Great thread, firemanup, because I agree with you! I learned after building & flying my USR Banshee (see this thread), that while I don't go as crazy as others, I have certainly guilty of overbuilding in the past. I'm working to correct that now.

I think one of the biggest misnomers about building MPRs & HPRs is that you *MUST* use epoxy. Aliphatic resin (yellow wood glue) in wood-wood & wood-paper joints is plenty strong enough--it's proven to be stronger than the materials that are being bonded! What more could you ask for?!? On top of that, it's cheaper ;)

Probably the second biggest "offense" is using thicker plywood than necessary. While I am not aware of a chart or reference of what thickness wood should be used with what levels of thrust and/or rocket diameter, I bet most of us (again, I've been guilty in the past) of using thicker than necessary plywood for CRs & fins. Hopefully someone else can expand on this further...

I have no personal experience with fiberglassing but it kills me everytime someone, particularly in the LPR forum, inquires about 'glassing balsa! If you need to 'glass balsa, maybe you need to use an alternate wood...not to mention save yourself a lot of work & hassle! On a related side note, check out the composites page on PML's website. They tell the story IIRC, of how they built a 6 foot tall rocket of carbon fiber tubing & flew the rocket on a G64! *THAT* is a good, not to mention impressive use of CF & 'glassing technique.

Just my $0.02...
 

daveyfire

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Recently I flew my Laser/LOC (unglassed paper tubing) on a J570W to Mach 1.3 and 12,000 feet, with a 1200 ft/sec/sec acceleration spike at power-up. The fins were surface mounted 0.093 G10, glassed with one layer of tight-weave 6 oz. cloth. The rest of the rocket was unglassed, untouched LOC paper tubing -- just painted over. It is a 54mm model designed for long burns. I've flown it also on a J460T to about 11,500 feet. On rockets this size, you really don't need to glass the tubing. It's only when you get up into around 4-5.5" that I'd start to worry about glassed tubing -- and even then, only for crush strength. I've stood on the end of an unreinforced piece of Quik Tube, which we all think is fairly weak -- and I've seen it flown unreinforced on a HT M1000 and an M1419W!
 

firemanup

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Davey excellent information thanks..

Surface mounted so they were glassed tip to tip over the body tube...

What kind of centering rings and how many, and what epoxy? Any fillers..??

One of the things i find myself doing that i think is shear overkill is coating both sides of centering rings... it adds weight, i think i'm moving towards normal fillets on centering rings with Glass fiber added to 30 min epoxy...
 

Stymye

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great post! and I'm sure will be full of opinions(including mine as usuall)so I'll get mine over with... lol

you're forgetting something major so far...,,,landing stresses... I don't have any data ,,so I'm guessing 50% of rockets sustaining damage were from the impact of landing?... you will notice that people who fly from playa...are not afraid to use epoxy/fiberglass even on small builds..lol

on the other hand,I built my L1 (stock ezi-65) with titebond II exclusivly..have over a dozen flights with the stock chute..the last flight landed on a rock hard dirt road and no stress damage so far, just some fin chips around the edges...

I have read her that alot of people use epoxy to attach balsa fins
all I can think is why?(why add the weight... if anything)

I preferr epoxy on any joints that invole plastic
or weldbond on "F" power or less builds

I stay away from epoxy with less than 35 min cure time
the longer the cure the better the penetration

I'm sure 5 min epoxy works fine in many cases..
but If I have a choice when I buy some, I will go with the strongest I can find

I purchased the West system for some fiberglassing jobs so I just transferred some of the the components into plastic squirt bottles and use that for all my epoxying and it has turned out to be cheaper than buying the hobby type in the long run

If I need a stronger fin I go to basswood or cover with paper

Basswood is not used enough In my opinion..It's pretty darn light for it's strength..but does not make a good centering ring unless layered

One of the things that draws me to rocketry is the challenge of building something strong yet lightweight to get the best performance
 

rstaff3

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Misc. ramblings on an otherwise good thread. :)

First of all, I'll have to admit that I often overbuild. I glassed the fins on my 29mm FatBoy partially because it was so easy to use the pre-cut balsa and I had the fiberglass out for other purposes. I have heard of successful G flights on stock balsa fins, but was worried about the landing since I knew the model would be heavy and I wanted to use a tiny chute.

My main (only? :rolleyes: ) accomplishment in 'building light' is my almost 6', 8" diameter Great Googly Moogly which used pster board skins with foamboard rings and fins. This flies on G80s and could handle small Hs. This concept has since been refined by Mark Hamilton (see SpRocketry May/June 2004) to include built-up fins.

The only problem I see is organizing the information as the answer to this question will vary parametrically with the size/weight/motor combinations.

I've seen several large rockets that flew on M's and N's that used no fiberglass (basic rocket materials, nothing too fancy).
 

firemanup

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I'm guilty of starting to use epoxy on low power birds.. i dont' do it for the strength though..

The sole reason being that i can make much nicer looking fillets with it than i can with CA and i don't, never have used any of the elmer type glues.. just CA or epoxy..

I understand what you're saying about landing stresses and you're right, takes another examination then to see if the heavier build weighs more than a bigger chute...

I'm wanting to figure out how to build something as lightly as safely possible to be able to survive the flight stresses..

Or as much as anything learn what i'm doing that's overkill that i can stop doing ...
 

rstaff3

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Originally posted by stymye
you're forgetting something major so far...,,,landing stresses... I don't have any data ,,so I'm guessing 50% of rockets sustaining damage were from the impact of landing?... you will notice that people who fly from playa...are not afraid to use epoxy/fiberglass even on small builds..lol

on the other hand,I built my L1 (stock ezi-65) with titebond II exclusivly..have over a dozen flights with the stock chute..the last flight landed on a rock hard dirt road and no stress damage so far, just some fin chips around the edges...
My experience, and that of others I have talked to, is you are right that more damage occurs on landing than on boost. The heavier the build the more likely...back to the original topic.

On wood paper, wood glue joints can be stronger than the materials (ie the paper tubing). However, epoxy fillets tend to help this as the spread force over a wider area.
 

firemanup

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Rstaff,

Agreed a "paper" rocket can be flown on M's i've seen video of it being done..

But, can a light paper rocket be flown on an M, that is overall small enough that it's going to be sustaining 25 or 30 G's and go through Mach...?? without any fiberglass reinforcing..??

I've had it suggested to me not to push a paper rocket through mach without glassing minimum fins tip to tip and preferably the whole airframe..?

Part of my own reason for this thread is my consideration of my next two rockets going to be paper tubes and both with the ability to scream through Mach without any problems..
 

Stymye

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I think a paper tube will go mach with no problem unless it's so long that it bows from the g's(and therefore disassembles itself)

the fin's and possible flutter..your doing the right thing by re-enforcing I'm sure
 

rstaff3

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Originally posted by firemanup
Rstaff,

Agreed a "paper" rocket can be flown on M's i've seen video of it being done..

But, can a light paper rocket be flown on an M, that is overall small enough that it's going to be sustaining 25 or 30 G's and go through Mach...?? without any fiberglass reinforcing..??

I've had it suggested to me not to push a paper rocket through mach without glassing minimum fins tip to tip and preferably the whole airframe..?

Part of my own reason for this thread is my consideration of my next two rockets going to be paper tubes and both with the ability to scream through Mach without any problems..
This is a good question and the ones I mentioned most likely did not break mach. I would assume that the answer is dependent on the size of the tube involved (length, width, thickness).
 

DynaSoar

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Originally posted by firemanup
It's my opinion when looking at my own builds and those of others that we often overbuild our rockets.
...
I'm curious what's really needed to push the envelope..
Excellent thread.

I think a lot of people overbuild because either they collect as many tips and tricks as they can and use them all "just to make sure" or they just get into the making of things so much that they make even when not strictly necessary. But hey, that's why it's a hobby.

I've been trying to pare things down from HPR building while simultaneously using LPR techniques and building them up, and seeing what works and what fails. Frinstance, plain old paper centering rings work fine if you cover them completely with wood glue on both sides, and then glue on some reinforcing struts.

I'm about to build a 38mm minimum diameter bird using a fin can, and I'm already convinced that while fin cans are excellent ideas, this one is twice as thick and heavy as it "needs" to be.

Next week I'll be launching some cluster-body birds to test the design (see: http://rocketryforum.com/showthread.php?s=&threadid=8457&highlight=squadron). 3 E9's at a time will definitely test whether wood fins tucked into the joint of two paper body tubes and glued with wood glue can handle a good swift 85.5 N-sec kick. I can't fly them 2 stage at the local launch due to propellant weight limits. When I do, they'll be riding the equivalent of H power. Although a few parts are custom cut and/or had carved, all parts and adhesives are LPR stock (except epoxy body fillets on the third, to compare with the second).

If something fails, I'll figure out why and then try the next "lowest" technique to fix it. It's always an empirical question.
 

rstaff3

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One thing about my overbuilding is at I often build for the biggest motor I envision flying, but historically I don't ever fly them on those motors. Examples:

1. My L1 3" Ultra Fatboy built for a J350. The biggest motor it got was an H242.
2. Build 24mm clusters for F24s, and fly them on E9s.
3. There's more....
 

scm86

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Yep, it works, it was however reinforced with epoxy, just like a glassed tube, but without the glass...

Scott McNeely


Originally posted by firemanup
Rstaff,

Agreed a "paper" rocket can be flown on M's i've seen video of it being done..

But, can a light paper rocket be flown on an M, that is overall small enough that it's going to be sustaining 25 or 30 G's and go through Mach...?? without any fiberglass reinforcing..??

I've had it suggested to me not to push a paper rocket through mach without glassing minimum fins tip to tip and preferably the whole airframe..?

Part of my own reason for this thread is my consideration of my next two rockets going to be paper tubes and both with the ability to scream through Mach without any problems..
 

bobkrech

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I think the primary reason that rockets are overbuild is because most folks think it's too hard to analyze the stresses in a rocket during flight. It really isn't, and in fact, it's pretty easy to do the zero order mechanical stuff. Here's some rules and tests.

First rule. During ascent, the mechanical load on the rocket equals the thrust of the motor. Why? Ask Newton. He simply stated "For every action, there is an equal and opposite reaction", or it's the motor's thrust that causes the problem. For example, if a motor develops 1000 pounds peak thrust, the load distributed in the rocket during ascent can not exceed 1000 pounds.

Second rule. This load must be carried by all cross-sections of the rocket. If any cross-section can't carry the load, then the rocket undergoes a structural failure. If you know the cross-sectional area and the yield strength of the materials, you can do a simple calculation to identify weak points in a design.

Stressed Area (sq in)* Yield strength PSI / Thrust (pounds) = Material Strength/load = design factor

This design factor should be >= 1.5 for a rocket.

Third rule. You can test the design by using dead weights to generate these load simply by evenly distributing a dead weight load to the structural parts of the rocket. Yes. It's that simple. For example, is my body tube strong enough? For a 1000 pound motor, take a section of BT and load it to 1500 pounds in a hydraulic press or with dead weights (design factor of 1.5). If it doesn't buckle or collapse, your ok. (If you use weights, be careful. You don't want 3/4 falling on you.) Is the motor tube/bulkhead strong enough for your 1000 pound motor? Again, invert the rocket on a flat, hard surface and load the motor tube with 1500 pounds (again a design factor of 1.5). If it doesn't break it's strong enough.

Fourth Rule. More people strip chutes than shred their rockets, so recovery forces can be tougher than ascent loads. How much? It depends on how quickly your recovery devices deploy and the rocket's velocity at deployment. It not that hard to design for that non-optimal 50G or even 100 G deployments.

Digression: 1 G is a velocity change of 32 ft per second per second, so 50 g is a velocity change of 1600 ft per second per second. That sound like a lot, but that roughly what you get if you miss apogee by 5 seconds and your chute deploys in 0.1 second.

Delta velocity / delta time ~ 5 s x 32 ft/s/s/0.1s=1600 ft/s/s = 50 G.

Compare that to a 50 pound rocket with a 1000 pound thrust motor that accelerates at only thrust/weight = 1000 lb/ 50 lb = 20 G.

How can you test your recovery system for this eventuality? It's simple. Weigh your rocket and hang 50 times it's weight from the shock cord. (that tests the bulkheads, eyebolts, quicklinks, shock cord, etc.) Do the same to the parachute to test the shoud lines. If nothing breaks, it's ok. If it does break, consider a device that opens the chute more slowly, or bulk it up.

There's more sophisticated tests that can be done but these simple tests and checks will do for for most normal high power rockets. These tests don't consider aerodynamic heating effects, but unless you have sustained flights over Mach 2, you shouldn't have to worry about that either.

As for an example of the strength of cardboard, go to the sonatube website and see how many feet of concrete you can put inside a cardboard tube when you build bridge columns. It's much higher than you think when you uniformly load it in certain directions. You don't need to need to fiber glass most rockets to handle the flight load, but as previously stated, transportaion load (side impacts) and hard landing (point loads) may make fiberglassing a desirable option.

I hope you find this useful.

Bob Krech
 

Smokin' Rockets

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Originally posted by firemanup
It's my opinion when looking at my own builds and those of others that we often overbuild our rockets.

**Very true

In my own case I know it's because I don't have the knowledge base yet to know what it really takes for the different parts of a build to hold together under higher stresses, so I play it safe and overbuild.

**Most do

We've seen plenty of info on beefing up rockets and the things we can do to accomplish this.

**Beefing up is one thing. Overbuilding is another

So in an attempt to learn more about the minimums necessary lets post some info, those of you with more experience and flights, what are the stats on some of your birds that you didn't think would handle a motor yet they did, or what are the stats on your lighter birds that you feel that you pushed the limits on.

I'd like to see what the lightest build is on a rocket that's pushed mach, maybe .9 mach or higher and/or whithstood some serious G's.. let's say 25 G's or higher.

So in other words who got the most performance with the least amount of re-inforcements, really pushing the limits of components.

**Wobble and harmonics (fin flutter) are the biggest cause of shreds.

Some things that would be of interest to me on the builds would be, construction techniques of the fin can. Built outside or inside of the body tube. Tip to tip glassing? if so what weight, glass only on fillets, epoxy used, 15min 30min etc.. epoxy additives micro balloons, milled glass...

Body tubes, glassed or no....?

**Glassing is always a good idea. For durability and strength. Really helps prevent zippering and recovery stress. Most sub mach rockets dont require glassing for boost

How many centering rings,

**Center rings are not as critical as people think. Once the properly constructed fincan is built, the middle center ring are not doing a whole lot

allthread re-inforced?

**I never understood who started this building technique. It serves no purpose except adding weight to the wrong end of the rocket.

Diameter of rocket and number of fins and fin material.. etc..

**Fin material is critical. G10 is great but can flutter terribly in larger spans or certail style of fin (swept back). Plywood is stiff and accepts glass very well. Once again stiffness is everything in a high performance rocket. When fin flutter occurs, a harmonic vibration begins. This will transfer through the entire rocket and litteraly self destruct.

The information that would help some of us to understand what the minimum is, that's really needed to handle a high speed high thrust flight.

I'm curious what's really needed to push the envelope..
**If mach is your goal, weight is very important. Yes you want to build it strong to withstand the forces, but a heavy rocket will not go mach unless you REALLY overpower it. Carbon fiber is your friend here. Diameter is critical as drag really increases with added width.

**Build your rocket to withstand the forces of flight and recovery. Not a crash. Usually no matter how strong you build it, a crash will damage it anyway.

.....Bill
 

Todd Knight

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Here's my .02 cents,

Most of the materials we use are plenty strong for our applications. As was said earlier, the boost phase is usually not the problem, it's recovery. Fiberglassing can make a rocket much more durable so that it will survive things that paper or phenolic alone would not. I have had late delays that deployed the chute when the rocket was on it's way down and tangled chutes that caused the rocket to come in much faster than planned. Reinforcment did or would have given the rocket a much better chance of survival to fly another day.

But, anything can be overdone. I saw one guy build a 4" rocket with 2 layers of 9 oz carbon and a layer of 6 oz FG, .125 G-10 fins and 4 pieces of allthread between all the centering rings. All this for a rocket that would never be flown on anything bigger than a J-350. I don't think it ever broke a 1000', although it did have dual deploment(LOL). My assumption is that this rocket was like those nuclear containment vessels that survive 500 mph impacts to concrete walls. This person has now learned that you don't have to go that overboard and has used his skills to build some great rockets that are not quite so silly.

In conclusion, if your building a rocket that you want to make sure will survive a lot of flights with little rebuilding, go ahead and do some reinforcment. But, you don't have to get silly.
 

Todd Knight

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I forgot this little ditty from a conversation a few months ago. We were talking about prepping rockets the night before a launch and somebody (I won't mention names) said they had a deployment charge go off and lodge a nosecone in their ceiling. Maybe we should be reinforcing our nosecones:D I would definitly be in major dutch with the wife.
 

BHP

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This is a terrific thread and an issue I've thought a lot about lately myself. I, too, feel that I overbuild my rockets - mostly out of ignorance of what is really needed.

I recently built a V2 and installed a larger MMT in a Bull Pup. Both have boat tails as you're probably aware. In building that 4" V2 with a 54mm MMT it struck me that the Slimline retainer I used should really transfer the energy from the motor to the airframe through the tail cone. It seems like a very strong method to me. When I then converted the Bull Pup from a 38 to 54mm MMT I was less concerned with making the interior CRs as strong as possible and thought more of just holding everything mid-line thinking the energy would be transfered through the boat.

I have also just used G10 for fins for the first time. I've never tried it before because I'd heard it is difficult to work. While it was only .0625 material it cut and sanded very easily. I'll use it again for sure. Lighter than 'glassed plywood, I'd guess. Anybody know a rule of thumb for using the various thicknesses of G10 as compared to A/C plywood (which I have a better 'feel' for using)?

I've used some of that composite honeycomb board for fins, CRs and bulkheads too. It is very lightweight, strong and easy to work.

Paper is strong and I've seen a 5.5" Horizon go Mach + on a AMW 1850GG. Very cool and it survived.

A couple of wraps of 6 oz. cloth just a couple of inches wide at the end will stop a BT zipper and is hardly noticeable.

There are materials and techniques for building light and strong. I just gotta learn 'em and hopefully this thread will help....

BHP
 

ELBRAZ

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Paper tubes, thin ones, can break mach successfully. I saw a Quest lightning fly on an H70. No glass at all. Tracked it all the way to ejection and followed the reflective streamer most of the way down. Disappeared in the wheat field west of Sayre Airport, of course. Fastest thing off the pad I have ever seen.
-Braz
 
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Evil Prince

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Overbuilding is easy to do but the biggest disappointment becomes motor selection. Overbuilding often involves gobs of epoxy, too many wraps of poorly-applied laminates and overdone hardware such as thread rod and similar metal hardware.

Epoxy in and of itself really adds little weight BUT it adds NO additional strength. It requires meticulous application (i.e. mixing, metering out, surface prep, etc.) to achieve maximum adhesion:volume ratio. I know this sounds obvious but at small volumes of epoxy, this becomes much more critical.

With regard to laminates (fiberglass, carbon fiber, kevlar, ibid), a proper resin:laminate ratio is often exceeded by vast multiples because laminates typically are applied by wetting the laminate/substrate and hand-applying the cloth. Even the most ardent and experienced laminator can exceed the proper ratio of resin:laminate to the tune of 2 or 3 times. The best way to apply laminates - based on achieveing the proper resin:laminate density - is vacuum-bagging. The downsides to vaccum-bagging are many: expenses incurred for such hardware, the justification of those expenses (one rocket a year? two? twenty?), the staunch order of the process, the jigging needed to maintain airframe integrity during the whole process. Nevertheless, the vaccum-bagged laminate can add only a few-thousandths of an inch to an airframe diameter and maintain FULL resin:laminate strength.

An in-between method is a "mechanical" wrapping of a laminate whereupon the laminate is wetted and applied to a prepped airframe, a release and breather are overlaid and the rather than atmospheric pressure, a tight-spiral wrap of duct tape becomes a pressure source.

Tom Binford, an rmr regular and very experienced builder and flyer, has flown unlaminated airframes to Mach 2.5. The caveat: the flight has to be zero AOA.

I'm totally against thread rod (with one minor exception). It is unnecessary. The proper use of epoxies with typical rocket components will provide all the strength necessary to withstand VERY hard accelerations. My L3 rocket uses 2- 12" pieces of thread rod (as can be seen here: http://www.urbanplight.com/detail_of_rail_button_mounts.htm). One flight I've made with this rocket toed the M1 line. If I were to have added thread rod to the motor mount and all the other places people dream up to employ it, it would have added add'l weight. Frankly, it's already overbuilt (it comes in at 35.5# ready-to-fly but motorless) but Joel Roger's Mega-Nuke has this beat by almost 6 pounds. Same rocket but I guess there was more "Peter Priniciple" in mine. That 6 pounds would have afforded me a few more motor choices.

Last year I built a 4" rocket which would have accomodated a 75mm, 6000N-s motor (http://www.metrarocketclub.org/RIP/Forsaken/forsaken.htm). It was built purely for fast, hard flights and altitude. Despite being somewhat meticulous about its construction, it still came in at 15 pounds with a 2550N-s L2000. Subtract the motor weight (about 5.5 pounds IIRC) and you wind up with a 9.5#, 4" rocket. You can get a LOC-IV to weigh about 3 pounds if built stock; it's a 4" rocket, too. I would have love Forsaken on an H but it just wasn't going to happen at that weight. (The L2000 flight WAS quite cool, though; that back-simmed out at about M1.3 and went 10975').

Just my experiences. Now I'm building a replacement for my dead-and-buried Forsaken and it seems that I'm coming in about 1.5 pounds lighter. At 8 pounds, an H242 could be used for kicks. But it does take a lot of forethought and the ability to re-engineer on the fly.
 

cls

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great discussion guys! this is my hot button with HPR, how really overbuilt most birds are.

however I think cardboard does have its limits. I will probably retire my LOC Caliber ISP (4 fin x 3" x 60" x 54mm MMT) because after a dozen I161/J210/J350 flights and the final J280 flight, the airframe is slightly crumpled and showing a spiral, just ahead of the top MMT ring. also I broke a fin, along the root, near the top of the fillet.

maybe I could just build another bottom section for it, but since I've already built another payload bay and replaced the nose cone - is it still the original rocket!?!??


some time ago I wanted to put a K550 in it, several people advised against it. I think they were right. so instead I am going to glass a phenolic 3" PML Tomahawk and use that for Ks.

it seems to me, for below Ks, cardboard and yellow glue are just fine, lighter and cheaper too.
 

Smokin' Rockets

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Originally posted by cls
great discussion guys! this is my hot button with HPR, how really overbuilt most birds are.

***Build for how you are gonna fly it. If a 3 or 4" rocket, and H or I's are gonna be max, not much extra reinforcement is needed. J's and K's would need glass as a minimum. ETC....

however I think cardboard does have its limits. I will probably retire my LOC Caliber ISP (4 fin x 3" x 60" x 54mm MMT) because after a dozen I161/J210/J350 flights and the final J280 flight, the airframe is slightly crumpled and showing a spiral, just ahead of the top MMT ring. also I broke a fin, along the root, near the top of the fillet.

***You can slide a coupler down the tube, or an external wrap of glass.

maybe I could just build another bottom section for it, but since I've already built another payload bay and replaced the nose cone - is it still the original rocket!?!??

*** Once again, sand it down and practice your glassing.


some time ago I wanted to put a K550 in it, several people advised against it. I think they were right. so instead I am going to glass a phenolic 3" PML Tomahawk and use that for Ks.

***That Tomahawk has a bad fin design for K flights. They tend to flutter and self distruct. I would call PML and have them make it with a 54mm mount and .093 G10 fins. Or choose a more suited design

it seems to me, for below Ks, cardboard and yellow glue are just fine, lighter and cheaper too.
.......Bill

PS. Dont listen to Gene, he dont know what he's talkin about :D
J/K
 
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Evil Prince

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Yeah, that's from the guy who taught me 90% of what I know...:D
 
E

Evil Prince

Guest
You can't beat laminated airframes for LONGEVITY. Front and back of it. Even for basic damage (zippers, cracks, etc.) they're even WAY easier to repair. Cinch a LOC tube or crack a PML and you'll see what I mean.
 

GL-P

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I agree. My 38 minimum diameter bird is overbuilt. I did this because I was going to have plenty of elecronics I didn't want to lose. It has a layer of 6oz and a layer of 2oz glass cloth on the tubes and on the tip-to-tip fins. The difference is my rocket has apogee backup because I wouldn't want this thing coming in ballistic.

I've seen a video of a cardboard rocket on a propulsion polymers M in it. Quit impressive.

I had fun one day when one of my tech projects in school was to build a rocket. All we had to use was paper, foam, and our choice of fins. I built a very light rocket with thin balsa, a foam nosecone and a minimum diameter hand rolled tube. I lost it on a C6.

I think phenolic is useless. It's too brittle. It certainly stiff but I've seen rocket crashes where the rocket would've survived much better with a cardboard tube.

Best idea for fibreglassing: mailing tubes: light cheap and takes epoxy real well.

Almost all my other HPR rockets are light like a 6 ft 2lb Level 1 rocket.
 

cls

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some time ago I wanted to put a K550 in it, several people advised against it. I think they were right. so instead I am going to glass a phenolic 3" PML Tomahawk and use that for Ks.

***That Tomahawk has a bad fin design for K flights. They tend to flutter and self distruct. I would call PML and have them make it with a 54mm mount and .093 G10 fins. Or choose a more suited design
good advice, thanks!
 

DynaSoar

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Originally posted by GL-P
I agree. My 38 minimum diameter bird is overbuilt. I did this because I was going to have plenty of elecronics I didn't want to lose. It has a layer of 6oz and a layer of 2oz glass cloth on the tubes and on the tip-to-tip fins. The difference is my rocket has apogee backup because I wouldn't want this thing coming in ballistic.

That's not overbuilt. That's built just about the right hardness for its maximum intended mission.

Glassing a Fat Boy and putting on G10 fins through the body to the MMT, that'd be overbuilding.
 
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