Ari's 6" PVC sewer pipe tube-fin L3 rocket

[iter]

Spoilers: I successfully flew and recovered this rocket on M650 this past Thursday at XPRS.

This rocket is the culmination of my sewer-pipe construction program that includes 2 3/8" ABS and 3" PVC rockets. My goal with this program is to certify L3 with a cheap and non-labor-intensive airframe, and especially without fiberglass. My intention for all these rockets is to stay subsonic (tube fins do poorly at Mach); large diameter and irregular transitions increase drag, limiting peak airspeed. At roughly $1 per foot, 6" thin-wall PVC is about the most affordable large-diameter airframe material. By comparison, LOC 5.5" tube costs $10/foot.

Here are some pictures of the L3 flight, and of my other plastic tube fins (they may get their own build threads eventually). Construction photos and such follow.

Ari.

 

[iter]

Overall dimensions:


I like tube fins for mechanical strength and ease of construction. Fin-can is a 4-step operation. I start with gluing two pairs of fins together and gluing the third pair to fuselage flat on the bench. Once adhesive is dry, I add one of the free pairs, wait for adhesive to dry, then turn assembly over and add the remaining pair.


I have access to a laser cutter. Nonstandard tube diameter requires custom CRs. 1/4" indoor plywood.


I use LOC 3" cardboard MMT. Yellow glue works very well attaching plywood to plywood and plywood to cardboard. Even still, I build my rocket so that no flight loads transfer through glue lines. Aeropack retainer (the most expensive part in the whole build) pushes on the bottom bulkhead, bulkhead pushes on fuselage tube. I glue a CR on top of the bulkhead to center MMT in fuselage, but it carries no thrust loads. Indeed none of the three CRs carry any loads except centering the MMT and containing ejection pressure.


I add middle CR while MMT is still out of fuselage. I use Gorilla glue to bond plywood RCs and PVC. I glue in the top CR after MMT is in place and that adhesive is dry. I use 80-grit paper to rough up PVC. Plumbing pipe generally has smoother finish on inside than outside and needs more sanding there.


I doubt regular hardware store PVC cement can hold up in this application. It might, but I have not tried it. I use a pure solvent PVC cement from TAP Plastics. It's water-thin and you apply it with a hypodermic needle. The process most resembles bonding acrylic with solvent cement. The smallest can this comes in it a pint. I now have a life-time supply. If you want to try this technique, I'm happy to give you a couple of CCs--enough to build several rockets. There's an equivalent adhesive for ABS. Application is identical, but formulation is different. Let me know which one you want.

https://www.tapplastics.com/product/repair_products/plastic_adhesives/ips_weld_on_2007/133

 

[iter]

I use 5/16" hardware on the A/V bay. I use coupling nuts to connect hex bolts to U-bolts, and drill nozzles out of Estes C motors to make spacers between bulkheads. It's easy to make the same plywood parts with a drill press and band saw if you're less lazy than I am.


I use a PVC coupler from the plumbing catalog for my A/V bay. Plumbers generally care much more about keeping consistent inside diameter of their pipes, so their couplers go on outside of tubes. Their couplers also come with a lip in the middle. I glue the lower bulkhead between this lip and an 8" section of pipe. The pipe keeps lower bulkhead securely in place, and bolts hold upper bulkhead to lower. These photos are post-test-firing and show some BP residue.


I install redundant altimeters (MAWD and DDC22) on top bulkhead and batteries on lower.


I use 1/4" phono jacks as arming switches. This allows me, besides using cool remove-before-flight streamers, to use this little doodad to measure battery voltage without going inside the A/V bay. I can verify battery at home, in the prep area or on the pad, all without taking the rocket apart.

 

[iter]

First flight: TCC 4/20/2013 L850. The goal of extending fins below bottom of fuselage is to let the rocket stand on its own on the ground. The amount of turbulent airflow around the nozzle surprises me.


This geometry creates a low-pressure area around the nozzle which wants to expand exhaust plume towards fins. Soot on inside surfaces of fins is the result. 84" chute drags the rocket through the dirt some. Skid marks are visible in last photo, along with fins that are full of dirt.

 

[iter]

Second test flight: TCC 5/18/2013 (Dairy Aire). L1390. This is a much faster motor than previous flight (and faster than target M650). My idea is to verify that my fins can hold up at higher speeds than I expect on cert flight. Dusk flight and green motor combine to produce surreal colors. I use no filters and no photoshop--this is how the lens captures these colors.

 

[iter]

First L3 attempt: Aeronaut 8/2/2013. M650. My 6" fin just clears the AeroPac 1515 launch rail. Special thanks to Kevin McGrath for help at the pad and for ground photos.


The up is good. Rocket hold up fine on the M. I'm trying a 60-year-old Maksutov 500mm reflex lens with my Cannon 60D. It works, but only on a tripod and tracking is impossible.


Both ejection events are nominal, but the main never comes out of its Nomex. In light of a long string of successful flights with this and my other sewer pipe rockets, I had become complacent with my packing. I normally pack shock cord inside the Nomex burrito and as it extends, it pulls the burrito apart. In this case, I packed shock cord on top of the burrito. It extends but fails to tease apart my burrito. I find the main on the ground still in a tight wrap. I lose all 6 fins and a piece off the top of the fuselage. tfish is helping with the post-mortem.

 

[iter]

One advantage of this material is how cheap and easy repairs are. Within two days of the crash, rocket is airworthy again. I use a bell-end of the pipe to repair top of fuselage. Bell ends are like built-in couplers on plumbing pipes. They save having to use--or make--real couplers. Again, the extra drag of the additional transition is OK for this rocket's purpose.

 

[iter]

Successful L3: XPRS 9/12/2013. M650. Same photos as in the first post. You're probably sick of seeing them now, but I never get tired of the image of that full main.

Ari.

 

[iter]

Tony Slajs has video of the second (L1390) flight:

[video=youtube;0WRmKxJcKso]https://www.youtube.com/watch?feature=player_embedded&v=0WRmKxJcKso[/video]
https://www.youtube.com/watch?feature=player_embedded&v=0WRmKxJcKso

 

[Eric1]

Cheap, effective media. Great Job iter!

 

[troj]

I assume you used standard PVC cement to glue the tube fins on?

-Kevin

 

[Area66]

Congrats for the L3 , thanks for the info, it will help as I want to build one too.

 

[qquake2k]

Outstanding, Ari, simply outstanding! Congratulations on your successful Level 3 flight! You must feel a measure of deserved vindication. I sure wish I could have been there to see the flight in person. Did Leah go with you? Did you take the ambulance to Black Rock? I hope I get to see this one fly at the Ranch!

I loved all the photos, and I wouldn't get tired of seeing that fat main open either! What a great job on the rocket, the process, and the flights!

 

[CarVac]

Now THAT is a cool idea. Where'd you get that 'doodad'?

 

[iter]

Cheap, effective media. Great Job iter!

Thank you Eric! Of all people, I'm sure you appreciate this material! Your rockets are an inspiration in my search for financially-effective airframe material.

I assume you used standard PVC cement to glue the tube fins on?

Thank you for pointing out this omission. I have my doubts about plumbing PVC cement, and I haven't tried it. I use pure solvent cement from TAP Plastics. Post #2 now has a description and links to the supplier. Plumbing PVC cement might make good fillets if you need them.

Outstanding, Ari, simply outstanding! Congratulations on your successful Level 3 flight! You must feel a measure of deserved vindication. I sure wish I could have been there to see the flight in person. Did Leah go with you? Did you take the ambulance to Black Rock? I hope I get to see this one fly at the Ranch!

I loved all the photos, and I wouldn't get tired of seeing that fat main open either! What a great job on the rocket, the process, and the flights!

Thank you Jim! My only "vindication" is observing that I'm successful when I follow my heart. Trying to please people who don't want to be pleased by building rockets I don't want to build is a recipe for unhappiness all around.

I drove the ambulance to Aeronut (scared the hell out of tfish, a former firefighter, who thought there as a medical emergency on the flight line). This time I flew into Reno and rented a car there. I'm planning to drive the van again for BALLS. You want a ride?



I'm sure Leah will enjoy the desert in a few years. I doubt she'd like it right now. She's a trooper for going to 2-hours-away launches with me, and she enjoyed camping for one night at Dairy Aire, but 9 hours in the van and three days in the desert is more than I expect she wants to do.

Now THAT is a cool idea. Where'd you get that 'doodad'?

That's a little like asking where I got the rocket :=) I built it :=) I use a digital voltmeter from a no-name Amazon seller (https://www.amazon.com/gp/product/B008KY5ULW/?tag=skimlinks_replacement-20), wire it to a phono plug and put the whole thing in a former wallwart housing. The engineering is trivial, but I like the result.

Ari.

 

[daveyfire]

That's incredibly innovative, Ari. Nice work! And congrats on your L3!

 

[rstaff3]

Great job Ari! I'm always interested in a rocket that's a little out of the proverbial box.

I was wondering if you had to work the tube or coupler to make the fit looser? The larger PVC components that I've gotten from Home Depot took a lot of force to get together and certainly wouldn't work as a shoulder for a payload or NC. Maybe your components are better quality than the standard Home depot stuff?

Thanks for sharing your build!

 

[Phil125]

Great job Ari! I'm always interested in a rocket that's a little out of the proverbial box.

I was wondering if you had to work the tube or coupler to make the fit looser? The larger PVC components that I've gotten from Home Depot took a lot of force to get together and certainly wouldn't work as a shoulder for a payload or NC. Maybe your components are better quality than the standard Home depot stuff?

Thanks for sharing your build!

Second that.... Did you get the thin wall from a local plumbing supply or online? Also did the coupler require alot of sanding then rivets or is it friction?

Also what are the parts you used on that nosecone.

 

[iter]

This is thin-wall PVC from Cresline (https://www.cresline.com/pdf/cresline-west/pvcds&sewerpipe/CWPVC11.pdf); it's available in 3", 4" and 6" sizes. I buy it from a local plumbing supply house: https://www.barronparksupply.com/ where they sell it by the foot. I'm sure it's available online, but shipping on a single, 10' length may be prohibitive. I use sandpaper only where I bond parts. Couplers slide on and off with some friction, but without any sending. I expect that is anything, sanding would make more friction by roughing up the surface. I know Eric turns some of his tubes down in a lathe--that makes a smooth finish. I do use 2, 4-40 shear pins on the main just in case.

The amount of positive force 1.5g FFFFG can produce in a small space surprised me. As experiment, you may want to put a little BP charge into the Home Depot PVC fitting and see if that blows them apart.

Nose cone parts are simply reducer fittings, with short lengths of pipe where necessary: white PCV 6" to 4" reducer, this plugs into an ABS 4" to 2" reducer, a length of 2" ABS pipe and a pipe cap. There's a threaded fitting on the 2" pipe that lets me take it apart. My original intention is to put a tracker there, but with the low altitudes this rocket achieves this proves unnecessary. It's now a storage compartment, sort of like the little nook on the M16.

Ari.

 

[troj]

Nose cone parts are simply reducer fittings, with short lengths of pipe where necessary: white PCV 6" to 4" reducer, this plugs into an ABS 4" to 2" reducer, a length of 2" ABS pipe and a pipe cap. There's a threaded fitting on the 2" pipe that lets me take it apart. My original intention is to put a tracker there, but with the low altitudes this rocket achieves this proves unnecessary. It's now a storage compartment, sort of like the little nook on the M16.

Yeah, it would be about like me putting a tracker on the buckets.

You've built another form of a drag queen! What would almost be funny would be a drag race between this and the buckets.

What was the total weight, without motor, and what did you get for an altitude?

Building stuff like this is fun -- it takes some thinking outside the box to get it all to work correctly. Conventional construction techniques definitely do not work!

-Kevin

 

[patelldp]

Very cool! Congrats on your cert flight!


Now that this pictorial is out there, have you considered selling ring kits? Seeing as you have access to a laser cutter, this may be a business opportunity! Make up a bill of materials and some of us out here may undertake cloning it for EX motor flights!

 

[iter]

No one can beat your drag. Without motor, mine weighs 13 lbs. I got 6,683' at XPRS and 7,188' at Aeronaut on a warmer day. Density altitude matters!

Drag racing against your buckets sound like fun. I wonder if you fly them much. I expect my drag to become a hangar queen. These are expensive flights, and once you know it works, less exciting to watch. Maybe a sparky L is I can borrow a 4-grain case :=) Are you coming to BALLS?

Ari.

 

[iter]

Very cool! Congrats on your cert flight!


Now that this pictorial is out there, have you considered selling ring kits? Seeing as you have access to a laser cutter, this may be a business opportunity! Make up a bill of materials and some of us out here may undertake cloning it for EX motor flights!

If you want to build one, I'm happy to make you rings.

The smaller, 38mm rocket may make more sense as a kit. It can be a cheap parkflier and L1/L2 cert ship.

Ari.

 

[patelldp]

If you want to build one, I'm happy to make you rings.

The smaller, 38mm rocket may make more sense as a kit. It can be a cheap parkflier and L1/L2 cert ship.

Ari.

Cool! I will search for a local supplier of the pipe. I fly locally at some waiver-challenged fields (6,000' and 4,500') and would love to fly an L or M motor and keep it under the waiver. I'll let you know if I can find the tubing, and then I may take you up on the offer!

 

[prophecy]

Congrats on your accomplishment, Ari. Perseverance pays off.

Funny, I bet if this hadn't worked, the pundits would have been back in full force with the "I told you so"s. Success has many fathers, failure dies an orphan. Bummer you went to XPRS and as a result probably won't be at Balls, I'll be at Balls and would have loved to meet you.

Congrats again, now put those fins I sent you to good use.

 

[rstaff3]

Ah, thanks. I think I missed the thinwall thing. My very very minor experience is with the thick wall stuff (not for a rocket or plumbing).

This is thin-wall PVC from Cresline (https://www.cresline.com/pdf/cresline-west/pvcds&sewerpipe/CWPVC11.pdf); it's available in 3", 4" and 6" sizes. I buy it from a local plumbing supply house: https://www.barronparksupply.com/ where they sell it by the foot. I'm sure it's available online, but shipping on a single, 10' length may be prohibitive. I use sandpaper only where I bond parts. Couplers slide on and off with some friction, but without any sending. I expect that is anything, sanding would make more friction by roughing up the surface. I know Eric turns some of his tubes down in a lathe--that makes a smooth finish. I do use 2, 4-40 shear pins on the main just in case.

The amount of positive force 1.5g FFFFG can produce in a small space surprised me. As experiment, you may want to put a little BP charge into the Home Depot PVC fitting and see if that blows them apart.

Nose cone parts are simply reducer fittings, with short lengths of pipe where necessary: white PCV 6" to 4" reducer, this plugs into an ABS 4" to 2" reducer, a length of 2" ABS pipe and a pipe cap. There's a threaded fitting on the 2" pipe that lets me take it apart. My original intention is to put a tracker there, but with the low altitudes this rocket achieves this proves unnecessary. It's now a storage compartment, sort of like the little nook on the M16.

Ari.

 

[TopRamen]

Wow! That's quite the impressive Build. Nice Job!

 

[troj]

No one can beat your drag. Without motor, mine weighs 13 lbs. I got 6,683' at XPRS and 7,188' at Aeronaut on a warmer day. Density altitude matters!

Similar weights, but you got more altitude with a little less propellant. Having a long burn motor helped in that regard, though -- I flew an M1400 to about 3K. A friend describes it as "That motor was trying to push those buckets out of the way the entire time"

Drag racing against your buckets sound like fun. I wonder if you fly them much. I expect my drag to become a hangar queen. These are expensive flights, and once you know it works, less exciting to watch. Maybe a sparky L is I can borrow a 4-grain case :=) Are you coming to BALLS?

I've only flown it once. I may fly it again, I haven't decided. The original version flew twice; the second one, altimeter batteries had died, so no recovery.

I won't be at BALLS this year, but should be there next.

-Kevin

 

[chris m]

Very cool . In the morning there will be a call to the local plumber supply. To find the glue ans the tubes . Make a cool 3-4 inch

 

[iter]

Cool! I will search for a local supplier of the pipe. I fly locally at some waiver-challenged fields (6,000' and 4,500') and would love to fly an L or M motor and keep it under the waiver. I'll let you know if I can find the tubing, and then I may take you up on the offer!

I gather these things are quite local. You may find similar pipe from a different manufacturer locally. When you buy and cut it, measure the ID so I can make sure to cut rings that fit your material.

Congrats on your accomplishment, Ari. Perseverance pays off.

Funny, I bet if this hadn't worked, the pundits would have been back in full force with the "I told you so"s. Success has many fathers, failure dies an orphan. Bummer you went to XPRS and as a result probably won't be at Balls, I'll be at Balls and would have loved to meet you.

Congrats again, now put those fins I sent you to good use.

Thank you. I'm planning to go back for BALLS--driving out Thursday morning if I can replace the van's leaking injectors by then.

Wow! That's quite the impressive Build. Nice Job!

Thank you!

Similar weights, but you got more altitude with a little less propellant. Having a long burn motor helped in that regard, though -- I flew an M1400 to about 3K. A friend describes it as "That motor was trying to push those buckets out of the way the entire time"



I've only flown it once. I may fly it again, I haven't decided. The original version flew twice; the second one, altimeter batteries had died, so no recovery.

I won't be at BALLS this year, but should be there next.

-Kevin

Yeah, it's a specialty kind of rocket :=) I can keep it around for next year--a drag race with your L3 ship is about the best excuse I can think of to burn that much motor through it :=)

Very cool . In the morning there will be a call to the local plumber supply. To find the glue ans the tubes . Make a cool 3-4 inch

The glue I use comes from a plastic supply house rather than a plumbing distributor. YMMV. Post #2 has details on adhesive I use.

Ari.