Pvc Scratch build. Almost done. Need opinions!

Our concern is possibly caused by the news last November of the Boy Scout leader who was killed when his buddy's rocket struck him from altitude during a Boy Scout launch. There were rumors that the rocket involved was made from PVC. I do believe that later reports came out stating that it was cardboard. Still, it was a tragedy for all involved.

There are indications that the rocket involved had other modifications that didn't meet NAR standards (such as not being equipped with a parachute).

Still, we want to protect our hobby, our friends and families, and property.

RocketNerd said:

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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Please don't misunderstand, all of us here on TRF love our rockets, however safety is first, just about 2-3 months ago an individual was killed while flying rockets at a Boy Scout event in California, I was a mid-power rocket about the size of an Estes Leviathan. He lost sight of the rocket and it struck him in the face, he died shortly there after from the wound, with medical attention. The gentleman's name was Michael Bentley. The press cannot get the story right however several statements by people who were there were released, there is even a thread here on the forum devoted to it. Since that time there has been one injury related to a rocket that "landsharked" (to a member of the forum) and in the last two years an individual in WA was also injured by a rocket.

Well thats unfortunate , but lets be honest. That could happen with any mid to high powered rocket coming in ballistic.. Doesn't have to be pvc to kill.. If i didn't care about safety i wouldn't be on this forum asking you all these questions or running my design through openrocket. I Would just slap this thing together and throw the biggest Kno3/sugar motor possible in the thing and let er' rip.
But i do appreciate your guys safety concerns, people like you are the reason we are still allowed to peruse this hobby!


Anyways to prevent such a thing happening can you guys inform me if my rocket is safe to fly according to my openrocket file?

RocketNerd said:

Anyways to prevent such a thing happening can you guys inform me if my rocket is safe to fly according to my openrocket file?

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From what I saw, you didn't post the file... Just a screen shot of it.

But that said, I'm not in a position to sign off on it.

Isnt a screenshot all you need? It contains all the info in it?

RocketNerd said:

Isnt a screenshot all you need? It contains all the info in it?

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From the information given in the screen shot as long as the conditions are right (low wind) and the launch rod/rail exit speed is high enough the rocket should be stable. The high margin of stability will make the rocket want to turn into the wind due the margin of stability, velocities off the rail will affect how much turning goes on to some extent, the margin of stability for your rocket is in the neighborhood of the MoS for the Estes Mean Machine (the MM is actually a bit higher, iirc). I would not attempt launching off a standard length Estes launch rod, if you choose to fly it use either a 1010 rail of 6' or a 1/4" rod of 6' in length. As for whether its safe to fly, none of us know that for sure until after the first flight, but we try and have a good idea beforehand, and a accurate sim will help. OpenRocket is capable of displaying stability vs. time and other graphs once you understand it, also make sure your sim is correct for flying conditions in your area (the coordinates for your launch site can even be entered iirc).

Thank you!

Well almost complete. Got the motor mount epoxied in including the fins.. All thats really left is a shock cord mount and a paint job.. and a final bead of epoxy on the fins



and just for fun

Something I noticed in your OR picture, there is not "Chute' Shelf". That is, some sort of structure to keep the recovery gear from shifting rearwards under acceleration.
It would be a shame to have all of those calibers of stability compromised the second the fun button gets pushed.

Is there a retention method for the motor?

Forgive me if this was noted earlier in the thread, but I didn't see it:

You talk about epoxy, and the airframe is PVC. In my experience it is VERY difficult to find an epoxy that actually adheres well to PVC, even some of the stuff that states it is specifically made for it. What epoxy are you using? Have you really tested if it will hold up? My guess is that if those fins are held on with "normal" epoxy, even with "the final bead" you mention, they are likely to pop right off with any sort of force applied (including flight forces).

I've used PVC in some rocket components, and I tested a LOT of different epoxies, including JB Weld, standard DEVCON & BobSmith stuff, Proline, and a couple different ones that specifically stated that they were for use in PVC/CPVC. I also experimented with some other methods (like roughened surfaces, holes in the surface, and PVC softeners). I was able to easily break/snap the bond with all but one of them.

s6

I am using loctite epoxy. I sloted the tube just through the surface and roughed up the surface plus drilled holes around the fins in hopes for more sturdyness. I have applied quite a bit if force to the fins and they seem rather sturdy.

As for the retention the F motor has a neck or so to say that keeps it from blowing straight through. As for the ejection I plan on using small screws and wire to hold it in place

On the PVC safety issue, I thought the primary safety problem was using a motor casing made of PVC rather than aluminum. In that setup, the casing can explode, spreading shrapnel that can't be seen on X-rays. In other words, an experimental propellant issue. As noted above, a PVC rocket coming in ballistic is going to mess up your day, but no more so than fiberglass or cardboard or anything else.

If you are free Memorial Day weekend, you should go to Fire In The Sky, WAC's annual launch festival in Mansfield (just east of Chelan). Everything from 1/2A to M/N will fly, with a waiver to 14,000 feet.

Most rocket damages with nominal flights occurs in one of three different events. Transport, ejection (airframe/nose collision), and landing (fin first, spinning airframe). There are many things you can do to increase chances of a safe flight. You already know it is over stable, so, launch in little to no wind, and, use a long launch guide. Keep in mind, it will weathercock, and, tend to turn INTO the wind. Make sure the nose is tight, but, not too tight. It looks like the nose is pretty heavy, so, that increases the chance of a drag seperation if it's too loose. Use a good quality swivel to attach your chute, and, make sure the shroud lines are all equal length (the less it spins, better for the fins). Give yourself plenty of distance from the pad, and make sure anyone around when you launch, is paying attention throughout the complete flight, all the way to touch down.

boatgeek said:

On the PVC safety issue, I thought the primary safety problem was using a motor casing made of PVC rather than aluminum. In that setup, the casing can explode, spreading shrapnel that can't be seen on X-rays. In other words, an experimental propellant issue. As noted above, a PVC rocket coming in ballistic is going to mess up your day, but no more so than fiberglass or cardboard or anything else.

If you are free Memorial Day weekend, you should go to Fire In The Sky, WAC's annual launch festival in Mansfield (just east of Chelan). Everything from 1/2A to M/N will fly, with a waiver to 14,000 feet.

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Hoping to be ready to fly my L3 at FITS, woohoo!

RocketNerd;
Don't let the nay-sayers deter you. You will learn valuable things getting this to fly right. And your next project will benefit from them.

Couple of things:
Do not wrap the parachute lines around the chute unless you want to core sample your acreage. For man-rated round chutes we z-fold the whole thing for extension to full length before the opening begins.
In OR, move the chute aft until it butts up against your shock cord, dog barf and motor. You can add cord and dog barf (ejection wadding) in OR. That will shift the CG aft towards the CP.
Do not shorten the rocket until you do the above and know how it fits. Would be a shame to shorten it beyond a good fit for the recovery gear.

For your next project, there is this beautiful PVC stuff designed for low-pressure drains. It is thinner walled and makes a pretty good rocket. I have built 3" HP rockets with it, and it is cheap. It is dang hard to get epoxy to stick to it, so test some pieces first to learn good methods.

Oh, and join WAC and come to one of our launches at 60 Acres park (membership not required). Just, you know, have the kinks worked out on that pvc rocket ahead of time.

I'm seeing 0 fillet on those fins. Bond strength with PVC is all about surface area. Mix up some JB Weld and smear it along those fin-to-body joints. Put on some rubber gloves, dip both index fingers in rubbing alcohol, and smooth the JB Weld fillets on both sides of a fin at the same time by "feel". Clean up the excess with rags. There are prettier ways to do this, but "pvc".

"Small screws and wire". I've done the same with a K motor. It works. Lost a stainless-steel retainer at a long weekend launch and had another motor to burn. The screws were still there, but the retainer was entirely gone. Where the heck did the retainer go? Blasted stainless-munching rocket lice pestilence.

Thank you Igotnothing! I really appreciate your positive help.. for the jb weld I already went ahead and did it with epoxy... doh! I roughed the crap out of the pvc and even cut gashes into it around the final mounting area.. I've applied a lot of pressure to the fins and there is no cracking or flexing, it really seems to hold well..

Ok...I have an idea. Bore some large lightening holes in the pvc tube wall with a hole saw in a drill press. Then paper over them with cardstock and some kind of contact cement. This will accomplish 2-things...weight reduction, and pressure relief in case of a cato (youll blow out a paper patch rather than shattering the tube). Whaddaya think ?

And thanks for the idea Igotnothing, just ran out and picked up some of that drain pvc. 2 24 inch 1.5 diameter pieces that im going to couple. Actually i picked up three tubes but the other is to be cut and formed into a nose cone as you see i have started in the pick below! This stuff is really really light and strong! Already got another project started and im not even finished with this one lol!

Sorry fellas... Doesnt look like im going to be straying away from pvc anytime soon.

For this rocket i plan on building it around an E12. After entering some rough dimensions into open rocket, it looks like an E12 will get this thing to 1171.26! and on a D9 862ft.
Wanted to build a rocket i can actually fly on my property and have a relatively good chance of retrieving it!




And RICH as far as your lightning holes... If the motor catos i doubt any amount of relief holes is gonna stop this thing from shredding. To be honest im really not worried about a cato at all. Like i said before im not going to be standing right next to this thing, hell even the low power estes kits i stand back from. If this thing catos im not going to be anywhere near in range therefor i am not worried about it. But thank you for the idea!


And just for the hell it, below is a Public Missiles Phobos i built years ago. Never has flown, i have the casings and everything. a 39/240 39/360 and a 39/480. Soon hopefully i can attempt my Cert 1 with the Phobos!





Will post pictures soon of the Pvc rocket after its finished being painted, its in the process as we speak.

RocketNerd said:

Actually i picked up three tubes but the other is to be cut and formed into a nose cone as you see i have started in the pick below! This stuff is really really light and strong!

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I'll admit, I'm a little sketchy on the PVC body tube thing too, however I am curious if you would elaborate on your nosecone technique. I've seen similar, but how are you doing yours?

i measure the diameter of the tube. Divide it into 6 equal parts on the top of the tube and 12 equal parts on the bottom part of the tube. Then i just connect the lines diagonally creating wedges. I then cut them out to form 6 points. I then make a small paper nose cone that fits over the top to hold all the points together. i then fill the tip from the inside with about a half inch or so depending on the size of the nose cone with epoxy and let it set. Peel back the paper and there you have it a rough shape of a nose cone. Then i tape the whole inside to seal up all the gaps and line the gaps with more eopxy. After it sets and some sanding you have a nicely shaped nosecone.

Below is a video that demonstrates this technique.

[video]https://youtu.be/z6VvQmoE0cg[/video]

And it baffles me you guys are worried about using pvc for my rocket but its perfectly okay to strap 4 M motors to a porta-potty and let er rip...Or bowling balls not to mention. Imagine what a bowling ball coming in ballistic would do..

PML's Quantum tubing is made from a type of PVC.

McKailas Dad said:

I'll admit, I'm a little sketchy on the PVC body tube thing too, however I am curious if you would elaborate on your nosecone technique. I've seen similar, but how are you doing yours?

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There was/is, a member here (Badazz Rocketry), that actually sells kits that used PVC for the body tube, but as they were mostly marketed to the HPR crowd, it was never considered taboo. They could be built to meet MPR standards though.

I've had some problem with epoxy on my Badazz PVC rocket. Gave it a good sanding with 60 grit then hit it with the cheap 5 minute epoxy. Problem solved!

The most striking thing is that PVC is heavy! Making connections that are strong are hard! Badazz rockets overcame this by using mechanical fasteners.

RocketNerd said:

And it baffles me you guys are worried about using pvc for my rocket but its perfectly okay to strap 4 M motors to a porta-potty and let er rip...Or bowling balls not to mention. Imagine what a bowling ball coming in ballistic would do..

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That's because the people who designed those rockets have launched tens or even hundreds of thousands of newton seconds of motors. They know what they're doing.

blackbrandt said:

That's because the people who designed those rockets have launched tens or even hundreds of thousands of newton seconds of motors. They know what they're doing.

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That's why the porta-potty crashed head first into the ground immediately after take off?
Anyways enough of all that non-sense.

Here she is 100% complete. By far my favorite rocket that I have built so far. Cant wait to see her fly!

Looks amazing!
Looking forward to the flight pictures/ video!

She did turn out quite pretty!:clap:

Best of luck for your first flight, and let us know how it goes!