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Make a Scale Static Propeller

Make a Scale Static Propeller

scale-prop

When it comes to scale RC planes, the biggest thing that ruins the scale look of the plane is a “smaller than scale” flying propeller. Many warbird pilots will paint their props the correct color and add the yellow safety propeller tips, but if you really want to get maximum attention at the flying field, nothing beats a static (non-flying), scale propeller. The classic Hamilton Standard 3- and 4-blade propellers were used on many fighter aircraft, and the kit from Nick Ziroli Plans is ideal for many round-nose warbirds like the F4U Corsair and Grumman Hellcat. You’ll need to do a little research to get the diameter correct, but for my Top Flite 86.5-inch F4U Corsair, a diameter of 26 inches was just about right.

The kit comes with three resin-cast propeller blades, several laser-cut plywood hub parts, a pitch gauge, and vacuum-formed front and back hub covers. The whole kit can be assembled with a few hand tools using the included parts, but I wanted to make a stronger and more detailed hub assembly. To do this, I used a couple lengths of PVC pipe from the hardware store as well as a few bits and pieces from the workshop spare parts drawer. Let’s put this thing together.

1 The stock kit comes with several parts, including the blades, center hub triangular wooden parts, and vacuum-formed prop hub pieces. To add detail and strength, I used some hardware store PVC pipe to make my own hub assembly. For this propeller, I used 1 ½-inch and ¾-inch diameter PVC pipe cut to the approximate lengths to form the main hub housing and the three prop blade sockets. The nominal dimensions of the pipes are 1 ⅞ inch and 1 ⅛ inch respectively. PVC pipe is very cheap! For a 5-foot length of 1 ½-inch pipe, it cost less than $3 and even less for the ¾-inch pipe.

2 To mark the three equally spaced lines for the blade placement, I made a simple CAD drawing for a guide. Using an old model rocketry trick, I placed the length of pipe onto the top edge of a desk drawer, closed the drawer, and drew the lines perfectly parallel to the pipe’s centerline.

3 After cutting the hub section to the proper length, I placed it in a drill press vise and used a 1-inch Forstner bit to cut the openings in the side of the hub. Use slow and steady pressure to cut through the PVC pipe.

4 After the holes have been cut, I used the belt sander to square off and smooth the ends of the hub. The proper hub width is determined by the kit’s triangular plywood pieces that are glued together. Here the hub triangle has been slipped into place within the PVC pipe. As a note, the distance from the flat sides of the triangle to the outer surface of the PVC hub housing is a half inch.

5 Next, using my TAIG micro lathe, I turned down the smaller PVC pipe pieces to fit snugly into the openings in the side of the hub. The lathe is a great shop accessory and is available from TAIG Tools (taigtools.com).

6 After trial fitting the outer diameter of the pipe to the hub housing, I set the depth of cut and turned down the other two blade sockets to match. Since I wanted the sockets to stick out from the hub a half inch, I made the overall length 1 inch. I set the length and cut all three sockets to size. After cutting and facing the socket pieces to size, I switched tool bits and counterbored the sockets (about a half inch deep) to fit snuggly over the base ends of the prop blades.

7 Here are the hub assembly parts together during the test fit. You can also see the counterbored inner surface of the blade socket.

8 I next turned some pieces of ⅛-inch plexiglass sheeting to make the front and back plates for the hub. Turning the parts requires a ¼-inch hole drilled into them so that a bolt and nut can be tightened on and then chucked in the lathe. Turning makes very true, circular parts that are much better looking than cutting with a bandsaw and sanding them round.

9 The Ziroli kit also comes with a resin-cast nose cap. I turned the nose cap down with the lathe to match my documentation drawings. The cast resin part machines and cuts easily and I reduced it about ⅛-inch in diameter, leaving a raised lip at its base. Cast resin can be sanded and smoothed to a polished finish before painting. While I was at it, I also cut a flat spot on the front of the nose piece and drilled a small hole in the hub for a scale attachment bolt head.

10 To flesh out the hub, I cut some ⅛-inch sheet basswood to make the webs between the blade sockets. Then, I glued them in place with thin CA glue and centered them between each of the blade sockets.

11 To form the fillets on the hub that make the assembly look like a cast aluminum part, I used Squadron White putty used for scale plastic models. I sanded it smooth and then applied a second layer of red glazing putty. The second layer builds up the thickness and helps round out the shape. When applied with a fingertip, it adheres nicely to the plastic and underlying white putty. It also shrinks less and almost never cracks while drying.

12 Here’s what the hub assembly looks like after a few minutes with some 320 sandpaper. Another putty treatment can be applied if you find any other flaws.

Propeller blades

13 Though the blades come with a rather smooth finish, lots of sanding is needed to prep their surfaces. All the little white dots left after sanding are small dimples in the resin that have to be filled in and re-sanded. I used red spot putty again to fill the imperfections and just lather it on. Let it set for a while and then use the popsicle sticks to scrape most of it off, leaving the dimples and pinholes filled.

14 The first sanding will take everything off except the putty filling the scratches and dimples. Keep doing this again and again until you have all the blemishes filled in and the blades have a smooth surface. Once everything is smooth, use a tack cloth to remove any dust, paint on a coat or two of white primer, and let dry.

15 Clean off any grease or fingerprints from the blades with a little alcohol and let dry. Now spray on a few mist coats of the yellow from the tip to about halfway down the length of the blades. Let the paint dry and then sand the yellow lightly to blend it in and eliminate any overspray. I used Master Modeler enamel spray paint and matched the color reference numbers to a 3-view drawing from a scale, plastic model kit. The basic colors are flat black and glossy yellow for the tips.

16 After the yellow has dried overnight, use a tack cloth to clean off the blades, mask off the tips, and form a small tape “handle” so you can hang the blades while the paint dries. I used 3M blue painter’s tape.

17 Mist on two or three light coats of the black, making sure to get both the leading and trailing edges covered. Hang the blade in a dust-free area until dry. After about an hour, remove the masking tape and set the blades aside until dry.

18 To really make the blades look scale, you need the manufacturer logo and the nomenclature markings at the base of each blade showing the pitch information. I used the waterslide decals from cal-grafx.com.

Final details and assembly

Note: This is also a good time to ream out the center hole to properly match the output shaft of your airplane’s engine. I chucked my 10mm prop reamer in my drill press and used a slow speed to enlarge the hole. It should be a slip fit. Because the inside is wood, you do not want a very tight fit. If the humidity goes up, the wood will swell and make it difficult to slip it in place or remove it.

19 The decals come with good instructions and go on easily. Don’t wipe the water away, but rather blot it away while pressing the marking down into place. Cal-Grafx supplies small sponge pads designed for this and they work well. Since we’re doing three identical blades, I put guide marks on a piece of paper to help get all the decals in the same locations. Now, let your decals dry overnight. If you add any clear coat, be sure to make sure it is compatible with the decals.

20 To add just a little more “eye candy,” I added hub assembly bolts and blade adjustment bolts. I think these are what make the hub so interesting to look at. Depending on the number of blades your hub has, you’ll add short bolts and tubes between each blade. For 3-blade hubs, there are two bolts and for a 4-blade hub, there is one bolt used between each socket. I used 2–56 cap-head screws and some brass tubing that was roughly the same diameter as the cap-head bolts. The assembly bolts and tubes are cut about ¼-inch in length and the blade adjustment bolts and tubes are about ⅜-inch in length. I cut the tube section just a little shorter than the bolts, so just one or two threads were exposed on the aft end.

21 Use a Dremel Moto-Tool with a flat cutoff disc and cut two notches into the raised web to fit the hub assembly bolts and tubes. This is a cut-and-fit operation.

22 Place each bolt and tube in the notch and center it with the web. Use thin and thick CA (I use Zap) and glue them in place. Mist a little kicker on and then add another application of thick CA and kicker. This fills in any voids and builds a small fillet around the tubes. Now do this for the other two web sections. Before gluing the tubes to the hub, add a small drop of Zap to the bolt and glue it into the section of tubing.

23 Now, grind small, flat spots on the sides of the sockets at the ends of the webs for the longer blade adjustment bolts/tubes to be glued in place. Apply CA and kicker to make a small fillet/glue joint to hold all the tubes in place. All the tubes should be straight and centered on the raised web.

24 After all the bolts/tubes have been glued in place, go over the entire hub assembly and double check for imperfections. A primer coat will also show any defects requiring further attention. Fill and sand as needed and then degrease the whole thing with alcohol and let dry. Here, the hub has been primed with white enamel primer. If you did your homework and everything is smooth, no sanding will be required. Apply a second and final coat of primer and let dry overnight.

25 Here’s the final result. I shot two coats of “buffing” silver onto the hub assembly and after it all dried, I lightly went over everything with a soft piece of cloth. This gives the silver a nice “cast aluminum” look. I also cleaned, primed, and then shot two coats of bright red onto the resin-cast nose cone after I glued the hex bolt into the front. A short length of dowel is used to connect and center the nose piece to the hub.

26 There are two ways to go here. Make your prop blades removable for easy storage and transport, or glue everything together. I glued everything together because over time the removable blades wear and can get damaged. Gluing everything together also means you won’t lose anything. Now drill into the base ends of the blades to fit the lengths of the ¼-inch dowel.

27 In the center of each blade socket, drill a matching hole in the wood core inside the hub assembly. You can enlarge the holes a little if the dowel does not match up perfectly.

28 Work with one blade at a time, and on the back of each, place a mark on it and the matching socket so you can match them up again later. I used 15-minute Z-Poxy to glue each blade into its socket. The Ziroli kit comes with a pitch gauge so each blade can be set at the same angle. Make sure they all set down firmly into their sockets and that all the blades are in line with the hub when looking at the sideview. They should all set in the same disc plane.

29 That’s it. Once the glue has dried, slip the propeller assembly onto your airplane’s engine shaft and you’re done! With just a little extra effort, you can make your plane stand out on the flightline and draw lots of attention. You can almost hear the sound of that powerful radial engine coming to life! Go ahead and give it a try, static scale props really make a difference.

Updated: July 23, 2015 — 8:49 AM

1 Comment

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  1. Outstanding work. Job well done! Looks really good.
    Gunny

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