Quick Build 1/4 Patriot

Please note: LOC Precision purchased PML in 2023 and no longer supply an identical 1/4 Patriot to the one below.  To get close to this model now you need to upgrade the LOC Precision airframe with the PML Quantum Airframe which includes G10 fibreglass fins.  Ignore the Phenolic and fibreglass option as this significantly increases weight and will require more expensive motor to fly safely.  You don't need the 48 inch chute upgrade. Cost as at Jan 2024 US $ 143.92 excluding shipping.   The rocket is available locally from Aerospace Education. We also recommend purchasing the phenolic piston upgrade. which protects the airframe and parachute from the hot ejection gasses and allows the rocket to eject reliably on a .5 gram charge.  

The techniques here apply to many level 1 and 2 rockets.  

Public Missiles 1/4 Patriot 

The quick build Patriot is designed to help you get started in high power rocketry with a fun, easy to build high power rocket. The quick build techniques employed here remove the need for hours of sanding, painting and filleting that are typically required. This page will step you through the process of building this impressive high power rocket that will allow you to achieve level one and two NZRA high power certifications. Altimeter ejection is recommended because 'failure is not an option'. 

The PML quarter patriot was chosen for many reasons. It's excellent value (US$120 in 2020) when it was supplied with fibreglass fins, parachute, shock cords, piston and the basic hardware.  It's quantum tube is light and easy to cover with car vinyl removing the need for painting and sanding. 3d printed quick build fin blocks create a strong rocket that can handle 'J' motors without the need for 24 fillets and tip to tip fibreglass. The piston provides the best possible protection for your parachute and shock cord and will reliably separate your rocket at apogee with only .5gsm of black powder. The 1/4 group has never had a rocket fail to eject or suffer a piston jam.

Over the last few years 12 patriots have been built privately and 15 as part of UCLA Canterbury's  Rocket Science courses.  Many have contributed to the development of the 'quick build' project.  See the Public Missiles 1/4 Patriot Group Facebook page here. 

The Kit

In 2013 the LOC 1/4 Patriot kit with PML upgrade is available in New Zealand from www.aerospaceducation.co.nz  for $ 320. High shipping costs from USA means that purchasing in New Zealand is cheaper than buying direct. The LOC kit does not come with a piston, is slightly longer and has a kevlar motor strap. The rail buttons are linear not the brass rods in the photo to the left. You can fly without a piston but your parachute and the kit will last longer if you do. 

The absolute minimum you need in addition to the kit if you use 'motor ejection' is a method for retaining the motor which can be as simple as a couple of T nuts and brass clips made from picture hangars or preferably a screw on aluminium motor retainer which costs about $ 60. That will get you up and running with a rocket that in low wind conditions can be set to eject the parachute at apogee using the delay on the motor. Sadly in high wind conditions rockets or with motors that 'chuff' on the pad rockets can be damaged on their first flight due to the number of seconds to apogee being different from what was estimated. As a result in high wind conditions, the rocket can arch over and be flying at high speed when the motor ejects or with 'chuffing' on the pad eject early when the rocket is flying at full speed. Both situations can result in the shock cord ripping the airframe in what is called a 'zipper'. The solution and the step we recommend from day one is upgrading to an altimeter to reliably deploy your parachute at apogee.  For the cost of an I motor the altimeter will  reliably deploy your parachute at apogee, record your rockets flight allowing you to view high resolution graphs of it's performance.  Altimeter ejection requires the addition of an altimeter, battery, altimeter board, cables and terminal block all of which are covered in the instructions below. 

See Stuart Lloyd's video Quarter Scale PML Patriot Build and Launch Part 1- The Kit


The combination of shot glasses and sticks allows you to make up small individual batches of glue. 30 minute epoxy will work but is significantly more expensive and ultimately laminating epoxy will always be stronger as it penetrates better and it gives you more time to work your parts. 5min epoxy is not suitable for the quick build blocks is more expensive again.  The rapid selling epoxies use chemicals to heat the epoxy to set it faster. You can purchase Laminating epoxy is also a lot cheaper per litre than the 30 minute and 5 minute epoxies.  You can heat your parts to reduce the setting time. NZ fibreglass sells 500ml laminating epoxy for $ 42. or 250mm for $ 27.


Booster Airframe

Payload Airframe


Payload & Piston Bulkhead. 

Seal all phenolic and plywood parts

Sand plywood and Phenolic parts 

Paint phenolic and plywood parts to protect with two pot epoxy wood preserver. This stops the phenolic becoming furry and pealing. It also strengthens and protects the surfaces from water when cleaning up after a flight and black powder ejection flame and soot

Bunker Workshop Video Part 2 - Wood Sealer

Prepare Air-frames for Vinyl Covering

Car vinyl is an ideal finishing material for PML quantum tube rockets as it removes the need to sand, fill, undercoat and paint tubes. It adds strength and is scratch resistant. Apply car vinyl to a shiny clean tube. 

Bunker Workshop Video Vinyl Wrap Part 4 

Maximum Strength Joints

A key to a long life for your Patriot is is sanding all parts that will be glued with 80 grit paper and cleaning with alcohol before gluing to 'key in' the epoxy to the tube.  

Do not sand the inside of the main tube above the fin slots as you want a shiny smooth surface for the piston to slide in. 

Lightly sand with 80 grit until the surfaces are scored as per photo. This will help the epoxy to adhere to the quantum tube. Your are scoring the surface only. 

Choose your Motor Retainer Method

Bunker Workshop

Aluminium retainer for extended motor tube

Aeropac Retainer for shorter motor tube extension

Harm-38 retainer, shortest motor tube extension 

T-Nut and brass, aluminium or steel straps (Modified brass picture hooks pictured here)

Motor Tube Forward Centering Ring

Glue the motor tube centering ring (has slott for motor strap) to the top of the motor tube using a specifically designed spacer developed by Bunker Workshop called a Top Hat to ensure that the centering ring is at right angles to the tube and the correct distance from the end of the tube for your motor retainer.   There are three Top Hat options 

-Bunker Workshop motor retainer (To Hat available)

-Aero Pack motor retainer (Future Design)

-HARM motor retainer (Future Design 8mm)

Sanding centering rings so that the edges remain flat. Rings should be a firm but not tight fit so that they do not distort the airframe. If you take too much off paint the edges with epoxy and re-sand.

Bunker Workshop Top Hat fits on top of the motor tube to position the forward centering ring correctly for your specific motor retainer and to hold the ring square to the tube

Test fit the forward centering ring when glue is firm but not dry. Do not fit the rear centering ring until after you have built the finset.

Motor Strap

Fincan Construction using Motor Blocks

Fin blocks for model rockets are design by Alex Heffer and licensed under the Creative Commons - Attribution - Non-Commercial license.


Mix epoxy, coat inside airframe.

Mix up 40 (8g hardner/32g resin) of two pot laminating epoxy. Using a gloved hand apply a thin layer of laminating epoxy to the inside of the air-frame up to the forward end end of the fin slots. (Any further could leave glue inside the airframe to interfere with the piston)


Apply a thin layer of epoxy to the rectangular area at the root of the fins and lay on a plastic sheet ready to load. (this area should have been 80 grit sanded at the start of the project)

Epoxy fin blocks

Apply a thin layer of epoxy to the fin blocks and lay on plastic ready for the build. Insert the motor tube and rotate until the motor strap is half way between two fin slots. 

Fitting blocks and fins

Lightly re-coat the first block and fit over the motor strap on the motor tube and then insert into the airframe between two fin slots. Then add second block, a fin, third block, a fin and then for the last block insert the block 1/4 way in and the fin front end in and work the two in bit by bit for a tight fit. 

Thrust Ring

Push the fin blocks until they are flush with the fins and no further. Install the rear centering ring and push down onto the fins.  Remove one glove, put your hand inside the air-frame and push the motor tube down so that it is flush with the top of the fins. Now cover the inside of the rear centering ring (thrust ring) with epoxy and push down on top of the fins. This should leave you with the required motor tube extension to suit your motor retainer.

Tension fins

Clean off any epoxy on the inside of the airframe above the forward centering ring and on the surface of the fins. Cover fin edges with rag or plastic Lightly strap the fins to hold them in place ensuring that they are providing even pressure to each fin. Don't apply too much tension. You only want enough vertical pressure to ensure that the the bottom of the fins maintain contact with the motor tube. If the straps are too tight they might pull the fins out of alignment.  

Set aside to dry for 12 hours

Check that the fins are still in alignment and there is no epoxy inside the airframe and then stand the rocket on it's tail on a jar lid that will push on the rear centering ring and not the motor tube and leave to dry for at least 10 hours in hot weather and 18 hours in cold.  You don't want any epoxy above the forward centering ring so check the tube before setting it to dry and clean any epoxy off now and then ensure the fincan is down when left to dry so that epoxy does not run along the tube. Once the epoxy is hard it is very difficult to remove from inside the tube and can cause piston jams even if just above the centering ring. 


Payload Bulkplate and Coupler

Vinyl Cover Fins

If you have the skills to spray paint you have the choice to paint or vinyl cover the fins. To cover with vinyl

Fin Fillets

Rail Guides

Fit Your Motor Retainer 


Piston and Coupler Fitting and Testing

Just Right

The payload coupler fit into the booster airframe should be tight enough that there is no 'slack' when you support the rocket from both ends but smooth enough that it ejects at apogee. Yes it's a compromise and as long as it passes the testing will be fine if not perfect. Sand the piston and coupler evenly using a rectangle cut from an icecream container and 220 sand paper to ensure that you don't sand 'flats' into the coupler. 

Smooth As

Don't over sand.  Sand evenly back and forth whilst rotating the tube a little at a time. Keep checking the fit after each rotation. If you over sand you will need to brush epoxy sealer or laminating epoxy and start again. Repeat the same with the piston. 


Pack your parachute and shock cord and then blow hard down the motor tube to check if the parts are smooth enough fit to reliably deploy at apogee.  Always clean out your booster air-frame and wipe down your piston and coupler before fitting as sand or dirt will effect the deployment.   

Altimeter Bay

3d Printed Alt Bay Supports

Fibreglass board

Cut fibreglass board to a height of XX and width of XX to fit the alt bay supports. The board and the alt bay support slide into the payload airframe and sit on top of the payload coupler. 

Power Switch

Cut holes for the stereo headphone switch legs and glue to the board . Solder 2 X contacts on each side to the altimeter power switch and 1 X contact to switch on your camera or tracker. These spring switches have a much larger contact area than switches and are under significant pressure. Keep the switch dry and check the contacts are clean before flying.

Static Port/ Switch Access

With the board fitted measure down to the top of the board inside the airframe. Mark this out on a piece of paper that wraps around the air-frame and align. Then cut a 1mm hole and check if it's centered. Adjust and then drill a 6mm hole. This is more than large enough to act as the static port during flight. 

Alternatively if you have a small high power magnet you can insert this into the power switch and detect the exact position using a small screw driver outside the airframe

Altimeter Recommendations

Many different altimeters are available. Members of the 1/4 Patriot group use these models and can help show you how to set them up and run.  

Quick Links

Two quick links are included in the add on hardware set

Shock Cord

Fold 5cm of the long shock cord over by 5cm and clamp leaving a 1cm loop then soak 4cm of the cor in expoxy and heat shrink in place. *** photo here

Retaining Nosecone

Drill 3mm hole through airframe into nosecone and use a single screw to retain the nosecone without weights and 2 screws with weight. Or use plastic rivets (not included)

Drill Hole for nosecone weights

Drill a hole in the nosecone base. Use a bolt to attach large nuts or lead weights to bring the center of gravity forward to at least 1 body diameter ahead of the center of pressure when the motor is loaded.

Finding Your Patriot

Once you are flying I motors and larger or if there are crop fields near by then it helps to use one of these methods to track your rocket.  Using these methods no one in our 1/4 Patriot group has lost a rocket. 

Video the landing or mark the direction by aligning your position with a distant point. Have another person guide you with a cellphone. Walk down the flight line with software on your phone or tablet that can draw your track on Google maps in real time (eg MotionX). Focus on that line and go a few extra paddocks than you expect if you don't see it first time then double back on a parallel track to your first line on the map 

Use an altimeter with a built in GPS or a beacon tracker. 

Beeline beacon trackers are the most reliable but it takes a skilled operator, yaghi antenna and radio to track the signal. Prices start at US$ 80 excluding freight.

Altus Metrum Telemini altimater and beacon tracking. NZ$ 270 including freight. 

Altus Metrum GPS Altimeter + Beacon tracking. Prices start at NZ $ 509 including freight. 

Beeline GPS and Satellite trackers provide high altitude and long range tracking. Prices start at US$ excluding freight

Build your own GPS tracker and groundstation.

If you are experienced at surface mount soldering then you can build a GPS transmitter and receiver dongle to plug into your laptop for around US$ 100 excluding shipping. You are on your own here but I hear that if built and operated correctly they work well. Transmitter weight, length required including antenna ****. 

Cellphone network GPS Tracker

I have owned a similar tracker purchased in New Zealand 4 years ago and it's still going strong. The battery lasts for days. You call the tracker and after a minute it will reply with the position if it's within cellphone range. If it falls in a ditch or lands in the corn where it can't receive or transmit you will be out of luck. Weight is **** 

Add on Hardware Kit

3mm screws and locknuts for terminal block through piston to aluminium strap 

2 pin JST Connector Male/female, cut the clip off for quick release.  Terminal block with aluminium strap stainless steel nuts and bolts. T-Nuts optional if you are making your own motor retainer. 

2 x quick links and heat shrink for shock cord.

Yellow fibreglass board only cut to 97mm to work with pine alt bay supports. Will need trimming to work with 3d printed boards.

Add on 3D Printed Parts Kit

Bunker Workshop alt bay wings and fibreglass board 

3d Printed Bunker Workshop Motor Blocks $ 40 for a set of four.

Chris's lightweight motor blocks $ 40 for a set of 4.

Michael's Alt Bay Supports

Rocket Stands

Bunker Workshop Single Bay

Bunker Workshop Double Bay

Parachute Packing

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