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Everyone knows about Plastic Props.  Many people know about carved wood props.  There is another type of prop that you can make that is a) light weight and b) effective.  I call these “Can Props” because they are formed on a can.

I have experimented off and on with these for years – and they still challenge me (probably because I don’t do them enough).  These are often seen on indoor models (Limited Penny Plane), but also some of the top scale modelers make these for their large models (Free Flight, of course).

A couple years ago, I did my Cessna Turbo 195 and asked Don Slusarczyk what to use for a prop and he suggested a 10″ diameter 15″ pitch prop and gave me instructions on how to make it.  It wasn’t too hard to make (wet formed balsa) and it works great.  Later I asked him what kind of similar prop to use for an Embryo and the pattern he recommended (7″ diameter 15″ pitch) worked well again.  Of course, matching the rubber to the prop is essential.

So I started to make this prop for a WWII NoCal where the prop diameter is limited to 7″ by rule.  I finished this prop to be used on my B.A.T. Monoplane Dimer, but was told to check the rules (one piece props only for Dimers!)

Regardless of what I put it on, here is a short segment on how I built it.

This is my first attempt on the prop for the Cessna.  Don provided the design for the fixture to set 15″ pitch.  Note the bracket at the hub to hold the prop spar (1/16″ dowel).  Also, this initial prop used an aluminum hub whereas the second Cessna prop used a one-piece spar.

For this new prop, I laid out the prop design on a plastic cup.  This is 18 degrees off vertical.  This cup is my Template – I take a second cup and slip it over this and trace the pattern on the second cup.  In that way, I do not have to continually lay out the design on a cup.

I use these cups from Walmart.  They are small.  This bag of 80 cups cost about $4.

Here is a single blade set up in a new fixture that was based on the old fixture but was designed for a fatter aluminum tube hub.  The hub was drilled for 1/32″ wire and that wire slips into a vertical tube to positively prevent rotation.  More in the next photo.

This is the back side of the same blade.  I used standard round toothpick as the primary spar.  Rather than cut the blade to fit the spar, I sanded a flat on the spar and glued it to the blade.  This method necessitated a tubing hub as shown.  The blade was very flexible, so I added a 1/32″x1/16″ stiffener to the back side of the blade.  I sanded it thinner.  The toothpick spar is being glued into the aluminum tubing with Canopy Glue.

Gluing to the cup/blade is nearly impossible, but Loctite makes a product that primes the plastic.  There is science behind this, but I won’t attempt to explain it – just know that this works.  The “Activator” is the key – I am pretty sure the glue is just CA.  Without this glue, I couldn’t glue the toothpick or the stiffener to the blade.

The finished prop comes in under 1 gram.  By the way, that is just flat black Design Master sprayed on the blades.  I haven’t yet tried this prop on any plane, but am confident that it will work for indoor models.  I anticipate having to match rubber to the prop and maybe trimming some of the prop away.

The more I play this game, the less I think I know!  Here’s what I do know.  For small planes, like Peanuts, we want to keep the plane light.  And for any plane there is a best-fit prop and rubber combination.

For my Peanut Bellanca Aries T-250, prop selection was (naturally) part of the process.  But since taking over Superior Props in 2013, I have been using wooden props almost exclusively – and it is not just a marketing ploy.  I think they perform better – and they generally weigh less.  Weighing less fits right in with the “keep your Peanuts light” mantra.

I started out with a 5.5″ Stacked prop.  This came out somewhere near 1 gram.  The bare prop weighed 0.8 grams, and I added tubing bushings and a Garami clutch, so the finished weight is about 1 gram.  1 gram is a great (light) weight and I am completely satisfied with that.

But I also mounted it on a Gizmo Geezer nose button.  These weigh about 1.2 grams.  In order to get the model balanced (with rubber) at the proper CG location, I needed to add about 1 gram of tail weight.  The all-up weight of the plane (without rubber) came out to 9 grams.  That is not bad for a Peanut and the g/sq.in. worked out to be 0.28 – which is pretty good wing-loading for a Peanut (or any scale model).

But those extra 2+ grams (1.2g GG Nose and 1g tail weight bothered me.  So I decided to try a different prop (and nose button).  Recently George Nunez showed a “can” prop he made and it looked great (and performed well, too).  I have made these before and decided to try my hand at making a light prop with these materials.

my 5.5″-6″ “can” prop template. I will keep this and just slip a different cup on the outside and trace the blades on the new cup.

I used some cups from Walmart and while I thought the material would be thin, it seems to be just fine.  I made up two blades, cemented on toothpick shafts, made a 1/4″ square prop hub, installed tubing and a Nason Clutch – and it came out about 1 gram (about the same as my stacked prop).  I made up a plug to replace the GG button and used a small Peck button.  The comparison of the assemblies showed that I saved 1 gram and testing showed that I could remove the tail weight – that’s 2 grams saved!  My model before rubber is now ~7 grams.  That’s a 22% weight savings.

the different in weight is the difference between the wood/Peck nose button and the Gizmo Geezer nose button.

That got me thinking about plastic props, so I assembled a handful of 6″ and 5.5″ plastic props and weighed them all.  Here are the results.  The big surprise to me was the (randomly selected) North Pacific prop is just as heavy as the SIG reproduction.  It was no surprise that all of the plastic were at least twice as heavy as wood – I’ve seen that consistently since I converted to wood – pretty much regardless of diameter.

Of course, matching rubber to any prop is another mystery and it is dependent on a myriad of things.

Everyone loves Peanuts (unless you’re allergic). Here is my latest. The Bellanca Aries T-250 – a rare model from the ’70s.  Cloudbuster Chris Boehm built one several years ago from the Walt Mooney plan.  We talked and he wants a bigger one.  I said “that sounds great” but I did this one for the upcoming indoor season.  (I’ll get to larger version later.)

Now I am working on printed tissue.  Two factors here: 1) there were only four built (easy!) and 2) all of the color schemes are complicated.

I built this (and cut laser parts) from light 1/32″ and light 1/20″ balsa – hoping to create something for Indoor that will not have to fly at a million (scale) miles an hour.  The ribs and most of the formers are 1/32″.  All of the stringers and cut pieces are 1/20″.  I did use 1/16″ square for the leading edges and spars.

This Peanut has almost 33 square inches of wing area.  That’s not bad for a “normal” airplane (not a racer or other “strange” configuration).  In fact, it is more than my Nesmith Cougar or my T.E.A.M. HiMax.

The challenge for me now (beyond the tissue) is to make a light and well-functioning prop.  I’m not sure if this will be a stacked prop or a formed prop.  I can’t seem to make formed props lighter than carved ones, so I’ll probably go stacked.  I’m calculating (mentally) a 5″ or 5.5″ at about 6″ Pitch.

Oh, I’ve got to vacu-form a windscreen – shouldn’t be too hard.  With any luck, I can get this flying at around 6 grams without rubber – I hope!