Pvc Scratch build. Almost done. Need opinions!

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RocketNerd

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Okay so before i ask for opinions let me update you with where i am at now.

The rocket total height is 5 and a half foot including nose cone. All made from 1 and 3/4 inch thin walled but sturdy pvc.

I made the nose cone out of pvc, cutting wedges into it and epoxying the gaps and forming a tip.

Sorry some of the images are a little blurry..


20160125_172055.jpg20160125_172126.jpg20160125_172135.jpg

The fins are light weigh ply wood, seem rather strong and should hold up

20160125_172322.jpg


The parachute is made from satin. Cut and stitched myself. Measures 32 inches across..

20160125_172358.jpg20160125_172330.jpg

My hang up.. I am so indecisive i cant for the life of me decide how tall i want this thing.. Im tempted to leave it as is but part of me wants it shorter. It weighs around 22 ounces right now. I know its all a matter of personal opinion but what do you guys think? Also I feel the fins are a little on the big side?


Also what is the lowest motor i could fly this on? I have a f50-6t handy, would that thing get this going? im not looking to set altitude records lol, a couple hundred feet and successful recovery i would be happy :) Would an E9 get her up?
I originally had designed this rocket to be flown on Rcandy motors because i really wanted to truly scratch build from the ground up including motor and all. I have built a few 1" diameter motors that functioned great, although my ejection method being built in isnt exactly reliable..I know that they produced enough thrust to get her going. But i want her back in one piece and am not willing to risk all my hard work due to a faulty delay grain/ejection charge nor am i willing to risk injuring someone, because a 1 pound pvc rocket coming in ballistic is going to do some major damage! So that being said, Kno3/sugar is on the back burner until i get some nice proven flights out of it on a Pro series F class or any class for that matter.

So what do you guys think, Rocket height, fin size, Motor size? Any other opinions to make this thing look nice and function as intended!?
 
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So.. What do you guys think about the height? Keep it, or hack 12" or so off..
 
Well I draw up a quick approximation in OR based solely on the pics and description. Looks like you have a whopping 12 calibers of stability, you could stand to lose a lot of tubing if you so desire. You could probably lop off 40 inches of tube and still be OK stability-wise.

At 22oz, looks like the F50-6 will get it up to ~1000 ft
An E30-4 might get it to ~300 ft
An E9(if it didn't CATO) would hardly get it 75ft.


Oh, and :pop:
 
In all seriousness, forget about using an E9 in such a heavy rocket, but that is all I have to offer in the way of advice.
An E9 sounds/feels like it might just pop it up high enough to clear the rod or rail and then become dangerous.

Have a look at some thrust curves and get some free software like Openrocket so you can do simulations and figure out what you need to get that thing stable off the rail for starters.
 
No i have not looked at any software, yet that is. But will be doing that before any final decisions are made! And thank you very much for your input on motor size!
Being that this thing is PVC, a little heavy and has a rather sharp hard nose cone, I really want to keep this thing safe, pointing in the right direction and under a safe amount of thrust!

Thank you Cabernut and TopRamen. (speaking of Top Ramen, im gonna make a cup of noodles right now. Thanks for the reminder that i have cup of noodles!)
 
Also thats the second time today iv read negative comments about the E9. Whats going on? Are these prone to blowing up or something? I have three of them...
 
E9 with their propensity for CATO's, would turn a pvc rocket into a fragmentation device. PVC's nature is such that most rocket builders on this forum don't use it for reasons such as its fragmentation, difficulty to spot on hospital Xrays, and it would probably be against NAR and TRA safety codes. But a sim program like OR would allow you to determine best flight motors, flying though would be at unsanctioned/personal launches/sites.
 
I live on a farm here in washington on 12 acres. A decent chunk of land but still not big enough for higher altitudes..
 
Also, it's extremely important that you choose a motor that gets the rocket up to a speed sufficient enough to be stable by the time it leaves the launch rod/rail. This is one of the things that sim software (such as OpenRocket which is free, or RockSim) can help you with. An underpowered motor may in theory get you up to "x" altitude, but if the rocket is too slow coming off the rod/rail, it can turn into a very dangerous missile, going in all kinds of unexpected directions other than straight up.

That E9 will NOT get you up to 75' even - your rocket will come off the rod/rail unstable, and head in some random direction (which could likely be you, a bystander, your car window, someone else's car window, etc.).

Do some research study on stability and how its achieved. It is not simply a matter of "these fins look about right". It's rocket science you know!
Don't let that scare you too much, it's really not all that complicated, but it IS absolutely something you should have an understanding of before you stick a motor in a rocket-shaped piece of PVC and ignite it. Bad things can happen. Don't do bad things.

peace and rockets,
s6
 
And that is exactly why i am here. As iv stated i am concerned about my safety and of those around me, including peoples property. Iv just downloaded openrocket and wow what a nifty little program! Thank you! This will help me out so much! I was curious about what my rockets center of grav was going to be and thought i was going to have to resort to the string method. Second thought, im still going to do the string method, cant always trust computers ya know.

A missile is exactly what im trying NOT to build! Missiles tend to blow up and disappear. I didnt spend an hour cutting and sewing my parachute to watch it and my rocket disintegrate and disappear lol!

Also this is isnt my first rodeo, iv been building rockets for years. Although this is my first PVC scratch build. I used to always get those estes builders kits with all the different tubes and nose cones and just have a hay day. Oh the good ol days!
 
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nah. West coast my friend :)

Check out some of the clubs local to the westside, BEMRC (Boeing Employees Model Rocket Club) being one of them, while a pvc rocket might not be flyable there, the knowledgable and friendly fliers are awesome people. We have regular fliers from our club here in Tri-Cities area that come from Western WA to fly with us all the time, all of them are great people to spend a day or three flying with.
 
Thank you! Iv been searching for club to potentially join. I have a high powered rocked kit that i built years ago with my dad. Even have the reload casings and everything. I desperately want to get my level 1 cert in the near future so i can finally fly this thing... It pretty much just been sitting in the corner with that casings in my tool box just asking to be flown..
 
Thank you! Iv been searching for club to potentially join. I have a high powered rocked kit that i built years ago with my dad. Even have the reload casings and everything. I desperately want to get my level 1 cert in the near future so i can finally fly this thing... It pretty much just been sitting in the corner with that casings in my tool box just asking to be flown..

IIRC, TRF members BEC and FlyFalcons are both members of BEMRC and could probably answer your questions or point you in the right directions, there is also WAC aka Washinton Aerospace Club on the westside.
 
I was curious about what my rockets center of grav was going to be and thought i was going to have to resort to the string method. Second thought, im still going to do the string method, cant always trust computers ya know.!
Simulator programs can estimate CG, but at least for small to medium rockets you can carry in your hand, nothing beats balancing the fully loaded (engine, wadding, recovery, payload..... The whole enchilada) on your finger
 
And don't let Micromiester see this thread.

If he sees your rocket, blood will shoot out of his eyes and ears!
You'll be in for a fierce flaming, the likes of which will only rival those when I fiberglass 13mm rockets!:wink:

:lol::lol::lol:
 
the max liftoff weight of a e9-4 is 15 ounces. the e9-6 drops to 12. How much does your rocket weigh, with the motor installed??
 
Yea the E9 is out of the picture. Hoping this F50 will do the trick. Not sure what it weighs with motor. Will have to weigh it later. Maybe might have to upgrade to a G motor. I want this thing to fly safely but not to high. Atleast not yet. Its a shame that i could be flamed about my rocket especially from another rocket nerd. And after i put all my hard work into it. Just because its pvc...

Anyways im in the process of rolling my motor mount tube as we speak..
View attachment 280809
 
DOH! and what do you know, got carried away with my rolling and over rolled it. Too large to fit inside the body tube!

Which brings me to my question.

Should i just roll it large enough where i can just stuff the body tube and not need motor mounts and just use the motor mount tube? Or should i use motor mounts?
 
DOH! and what do you know, got carried away with my rolling and over rolled it. Too large to fit inside the body tube!

Which brings me to my question.

Should i just roll it large enough where i can just stuff the body tube and not need motor mounts and just use the motor mount tube? Or should i use motor mounts?

If the motor is a good fit, you might not need a motor mount (it's called a minimum diameter rocket). Often motors like Gs and higher have a thrust ring on the back end that allows the rocket to accommodate a longer motor. If it doesn't, you can either glue one on the back end of the motor, or use several wraps of tape to prevent the motor from flying up and through the rocket. To keep the motor inside the rocket (for the parachute deployment) you can tape it.

Another thing you might be able to do is see if you can find/make a craft paper body tube that matches your PVC. Hack off much of the PVC to lose the weight, and replace it with the paper tube. Important thing to note though... Your CG (Center of Gravity) must be ahead of the CP (Center of Pressure). 1-2 calibers is stable, more than that, and you're overstable (the rocket will weathercock into the wind). If you CP is ahead of the CG, you've got an unstable rocket that is capable of doing just about everything except what it's supposed to do.
 
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The F-50 is probably fine, you said it was 22 oz right now, I fly a 20 ounce pershing on F-32's but it is a lot larger diameter and more draggy. For the motor you can always wrap tape around the motor to get it to fit the tube and then build up a tape thrust ring on the end and make sure you tape the thrust ring to the body so that the ejection charge doesn't blow the motor out the back. The F-26 might also work at that weight.

Frank
 
okay so after cutting the lenght down and plugging everything in to the exact weight this is what i came up with in open rocket with a F50 plugged in.


22.8 ounces
with a 9.48 cal stability
rocket.jpg

Would this be safe to fly?


And also i cant really make the tube slotted for fin installation. I was thinking of drilling just through the body and maybe putting 3 or 4 dowels to strengthen it. Otherwise the fins are going to just be epoxied on the outside of the body tube.
Any advice on how to get the fins perfectly straight?
 
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And don't let Micromiester see this thread.

If he sees your rocket, blood will shoot out of his eyes and ears!
You'll be in for a fierce flaming, the likes of which will only rival those when I fiberglass 13mm rockets!:wink:

:lol::lol::lol:

I did see it. I just shake my head with sadness..with all the good rocket building products out there why would anyone want to use HEAVY PVC???
Someone has already informed the OP that PVC is NOT a good choice for building Rockets and the reasons.
Further since He states he is flying from his own 12 acres and in Washington State (LEFT Coast) If it CATO's it will only be Him and His stuff that is in jepordy. Nuf said.

Perhaps He'll learn a good lesson, if it doesn't injury him or others.
 
okay so after cutting the lenght down and plugging everything in to the exact weight this is what i came up with in open rocket with a F50 plugged in.


22.8 ounces
with a 9.48 cal stability
View attachment 280878

Would this be safe to fly?


And also i cant really make the tube slotted for fin installation. I was thinking of drilling just through the body and maybe putting 3 or 4 dowels to strengthen it. Otherwise the fins are going to just be epoxied on the outside of the body tube.
Any advice on how to get the fins perfectly straight?

Just a suggestion. Turn it into a wind vane... Made from plastic it would last a long time. I've actually thought of doing just that for a project.

Right now Estes has some terrific prices on their PSII line, go and pick up 1-2 of each, and you won't have to worry about the safety of the kits. Also there will be a lot of people with actual experience making them too, so you'll have a lot of brains to pick. PVC isn't used by many, so your resources are few and far between.
 
Iv built countless estes kits and loved them all. I have built one high powered 4inch (i believe) diameter kit with fiber glass fins and all, although have never flown it yet because i have not attempted my L1 Cert, i have the motor casings and all. I just wanted to try something different and i had this junk pvc laying in my garage and thought, why the hell not. I liked the challenge of trying to get something not so light to fly.. Something unusual and different. Oh..yea.. and it was FREE! lol

I understand everyone's safety concerns but its not like im going to be standing a foot away from this thing when it goes off.. I DO take safety precautions when flying all my rockets, big or small, cardboard or pvc, my land or public launch sites.

And also i myself think that 22 ounces for pvc isnt all that bad..
 
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