Quick Build 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. 

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

• Tape measure with imperial and metric measurements

• 1kg (10th gram accuracy) electronic scale . 

• Plastic shot glasses, $ 7 for 100 at supermarkets.

• Lollipop sticks, 100 stick packs at the craft section of The Warehouse. 

• 1 sheet of 80,120, 400,600, 2000 grit wet and dry sand paper 

• Marine laminating epoxy such as West or NZ Fibreglass ($ 37 for 1/2 litre)  

• Isopropyl Alcohol, 1ltr $ 16 

• Epoxy wood sealer, $ 37 for 1ltr which would do 20+ rockets so best to share with another member of the 1/4 Patriot group. Or you can mix 40% mixed epoxy with 60% Isopropyl Alcohol and make your own wood sealer.

• Vinyl gloves to protect your hands from epoxy and surfaces to be glued from finger grease.

• Masking tape

• Altimeter bay parts depending on your altimeter design

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.

Sand plywood and Phenolic parts 

• Sand the outside of the piston coupler tube until it is a loose fit into the airframe with 120 then 220 grit. You are are sanding the piston tube so that after adding the wood preserver the piston will not be too tight. (If you sand off too much now you can paint on a thin layer of laminating epoxy later on.  

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. 

• Apply wood preserver to all phenolic and plywood parts except the outside of the motor tube.

• lightly coat the inside of the motor tube using a rag on a stick. 

Bunker Workshop Video Part 2 - Wood Sealer

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. 

• Prepare the airframes and fibreglass fins for vinyl covering by cleaning them with a hot strong detergent mix then rinse, dry and clean with Isopropyl Alcohol. From now on until the covering is on wear gloves handling the airframe.

• Cut the vinyl with razor or scalpel using a long metal ruler so there is a 1cm overlap when rolled onto the tube lengthwise and sideways. 

• Some vinyl has a thin outer clear plastic cover, remove that now.  

• Draw a horizontal line down the tube with a long ruler and pencil

• Fold down 1cm of the backing and apply to the line, try to minimise any pulling or stretching of the vinyl. 

• Slowly peal off the backing smoothing down the vinyl back and forth 1cm at a time. Ideally have one person support the end of the vinyl roll whilst you smooth back and forth. The key is to minimise stretching the vinyl so take your time and pull evenly.

• White or light coloured vinyl will need two layers to block out the grey colour of the airframe tube.

• Heavy duty vinyl is the easier to work with than thinner vinyl's. Heating and stretching is not recommended for vinyl on airframes but may be necessary for nosecones. 

• Bunker workshop method removes splits the airframe vinyl in two and removes the need to align the vinyl with a pencil line and covering fins now. 

Bunker Workshop Video Vinyl Wrap Part 4 

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. 

• Inside the fincan up to 1cm past the fin slots

• The outside of the motor tube

• The top 1cm on the inside of the piston tube. 

• The bottom 1cm of the coupler tube where the payload bulkhead will be glued

• The bottom 9cm inside of the payload airframe where the coupler will be glued in

• The rectangle root area of the fibreglass fins that will be below the surface 

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)

• Sand the inside of the centering rings for a snug fit to the motor tube. Dry fit the two centering rings. If the outside of the centering rings need sanding for a snug fit (not tight) to the airframe then roll them on a sheet of sandpaper to ensure you do not round the edges. *** alex need photo here

• Glue the forward centering ring to the motor tube

• Pass the motor strap (the shorter black strap) through the notch in the forward centering ring 10cm down the motor tube. 

• Mark the centre position at the end of the strap with an x to ensure that the strip remains straight. 

• Align the strap and then soak the underside of the motor strap with glue. 

• You can use masking tape at the end to keep it straight whilst drying. You only want enough epoxy to glue the strap down as you don't want extra epoxy squeezing out of the sides of the strap interfering with the fins.

• Check whilst drying and scrape off any excess glue.  

• You don't want any extra epoxy on the inside of the forward centering as that will stop the fins sitting tight to the centering ring and motor tube. (no fillet required on this joint)

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

Preparation

• Before starting practice dry fitting the motor blocks and fins. The last fin block will be tight, insert the front of the last fin leaving the rear up and insert the fin block before dropping the rear of the fin.

• Roll up the motor strap and insert into the motor tube to protect it from glue

• Cover the fin area with masking tape and the rest of the air frame with plastic sandwich wrap. 

• Protect your table and floor from dripping epoxy

• Have tissues or paper towels handy to clean up

• Check that the inside of the airframe and root of the fins have been sanded

• Check that the fin blocks are exactly the same length as the fins and if not cut or sand to fit

• Check that the root of the fins have been sanded and cleaned with isopropyl alcohol. 

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. 

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

• Clean fins with isopropyl alcohol and cut vinyl about 4mm wider and taller than the fins. 

• Apply Vinyl to both sides of the fins and then with a razor cut the vinyl back to about 2mm short of the fin creating a temporary groove between the two sheets of vinyl 

• Run a bead of epoxy inside the groove using the sharp end of a bamboo BBQ spear and let it dry. 

• Razor cut the vinyl back to that bead of epoxy. 

• The two layers of vinyl covering help to stiffen the fins compared with painted fins. 

• The epoxied fin block set makes the fin can very rigid making it capable of handling J350 flights. 

• As a result you do not need the traditional fin fillets but it does pay to run a thin bead of epoxy in the join between fins and airframe to stop the vinyl pealing. 

• Profile the supplied linear rail guides by putting 220 grit sandpaper on the airframe and sanding the guide down so that the bottom of the rail guide is the same profile as the airframe.  You might want to spray paint the outside of the rail guides before fitting them but mask off the inside slot where it will fit on the rail.  

• Fit the rear rail guide supplied with the kit to the rear of the rocket equal distance between two fins. Drill holes 1/3 the size if the screw shaft. Use two self tapping counter sunk screws to screw through the air frame and fin blocks. 

• Fit the front rail guide by cutting the vinyl so that you can 80 grit sand and epoxy it onto the airframe inline with the rear guide. A long steel ruler or rod helps to ensure that both guides are in alignment. 

• The New Zealand made Bunker Workshops retainer is available locally and is longer and is easier to fit hard up to the thrust ring (rear centering ring). In my experience it's not essential to use JB weld to fit a motor retainer on this size of rocket as the base of the retainer is never going to be heated enough to melt the epoxy.  

• 120 grit sand the inside of the motor retainer and motor tube. 

• Clean with isopropyl alcohol so there is no sign of grease (use gloves) and then use 24hr epoxy or JB Weld to glue the retainer to the motor tube. Apply weight to hold the parts tight for 12 hours. 

• Painted: You can spray paint the nosecone using plastic primer and then enamel spray paints. Experience has proven that standard undercoat/primer will not stick reliably to plastic. You need the same primer they use on car bumpers.  

• Un-painted white nosecone. Many people including myself fly unpainted nosecones. Wet sand off imperfections with 250 grit then 400 grit paper.

• Vinyl: If you realy want a challenge then there are videos on Youtube to assist with the tricky job of applying vinyl to nosecones. 

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.  

• Stratologger  NZ$120 from local suppliers is simple and easy to use without a computer. Beeps out the altitude. If you want data as well you are better moving up to the Easymini as the USB dongle is expensive and the data low resolution. Will run off a 2 or 3 cell Lipo or 9v alkaline battery. Intermittently available due to limited manufacturing. 

• Easymini NZ$159 has built in USB connection, high resolution data collection and sophisticated flight analysis software. Will run off a small single cell lipo battery. You need to download the high resolution data after 2-3 flights. 

• Telemini NZ$ 270 has high resolution data and beacon tracking. Requires a radio receiver such as the TeleDongle NZ$ 191 or support of other NZRA members running the same equipment.