Puzzled by Props?

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.

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