Early propellers were made from wood and they still are on some vintage/classic aircraft and reproductions. What types of wood are typically used to make wooden propellers?
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4 Answers
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Historically, the following woods were used:
- Mahogany
- Walnut
- Oak
Almost all wooden propellers are reinforced to add strength. Fabric or metal coverings can be added too.
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2$\begingroup$ What do you mean by "reinforced"? Do you mean by materials other than wood? $\endgroup$– SanderCommented Dec 10, 2014 at 8:37
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1$\begingroup$ @Sander The URL I referenced mentioned that, the entire section at the bottom. I didn't include that here because it was verbose and not directly relevant to the question. $\endgroup$– FarhanCommented Dec 10, 2014 at 17:13
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3$\begingroup$ Metal pieces like the one shown have a dual purpose. In addition to reinforcement, it protects the leading edge of the blade from damage when hitting birds, sand or gravel on runway, etc. $\endgroup$– brichinsCommented Dec 10, 2014 at 20:37
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$\begingroup$ Before reading the comments, I would have guessed ash. As strong as oak but lighter and harder. $\endgroup$ Commented Jun 30, 2023 at 18:46
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Propellers should be made from the same type of wood as wing spars: In both cases the requirements are the same, and the wood should have the highest strength to mass ratio. Both need to be light and strong, especially in tension in the case of propellers. However, using a hardwood will help with their resistance against nicks and scratches, so for the highest loadings, hickory, maple and oak are good candidates. Spars use softwood like pine or nordic spruce (wood from higher latitudes grows more slowly and has better strength) which are less often used for propellers. Historically a wide variety of materials has been used.
Culver Props selects maple for the highest strength and otherwise birch. Mahogany and cherry are selected for the looks.
Equally important is the glueing from laminated planks and shaping. The craftsmen at the worlds first propeller company, Chauvière, were first in the business of making toilet seats. Switching to propellers came naturally. Laminating helps to control the density of the wood planks and makes it easier to cut out imperfections, so laminated propellers are better balanced and will be 25% lighter because less allowance has to be made to account for imperfections.
answered Dec 9, 2014 at 21:32
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19$\begingroup$ Best of Aviation.se: "first in the business of making toilet seats. Switching to propellers came naturally" $\endgroup$– rbpCommented Dec 9, 2014 at 23:07
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5$\begingroup$ Is it really that important for toilet seats to be that strong??? My goodness, what are you people doing to them? $\endgroup$ Commented Dec 10, 2014 at 4:23
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2$\begingroup$ Key reason for laminating: wood will bend as it dries / absorbs moisture. By cutting it and re-assembling with directions reversed, you can effectively prevent this. So not only does it make the wood stronger (by criss crossing the main direction of the wood you make the strength isotropic; and you prevent crack propagation because there are no "preferred directions" any more), but you also preserve the shape which is very important for efficiency of the propeller. Edge "reinforcement" is there just for erosion control (dust, gravel, etc). $\endgroup$– FlorisCommented Dec 11, 2014 at 12:18
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1$\begingroup$ @Floris all agreed except for the isotropic part, which is not relevant for propellers. You want anisotropic strength and stiffness, i.e. all fibres more or less radial to counter the predominant loading. Which is just why wood with its strong anisotropy is (still) such a good material. $\endgroup$ Commented Dec 11, 2014 at 14:45
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$\begingroup$ @yankeekilo - the point is that you have control over the degree of anisotropy by changing the orientation (and layering). You may want more strength in one direction than another - and bias the lamination accordingly. At any rate, even a small fraction of cross fibers will reduce the chance of the wood splitting. $\endgroup$– FlorisCommented Dec 11, 2014 at 14:48
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Wooden propellers can be made of virtually any wood, I know Sensenich makes theirs of birch, and the company featured on this episode of "How It's Made" apparently uses maple.
I would assume that hardwoods (birch, maple, oak, etc.) are favored over something like pine or spruce that would be easily dented in operation if the propeller kicks up rocks on the ground, though I can't find a good reference on that.
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1$\begingroup$ I doubt lignum vitae would be a good choice though, makes the nose even heavier than it is already. $\endgroup$ Commented Dec 9, 2014 at 21:20
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$\begingroup$ @ratchetfreak Pusher prop? :-) It'd be pretty durable that's for sure! $\endgroup$– voretaq7Commented Dec 9, 2014 at 22:31
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$\begingroup$ The prop should have brass plating in impact areas, so spruce is no disadvantage. Birch is good for lowly-loaded props, and maple a good choice for props with higher loading. $\endgroup$ Commented Dec 10, 2014 at 20:57
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$\begingroup$ @PeterKämpf Sensenich apparently uses urethane in place of traditional brass bindings for the same purpose on at least some of their props - the inexorable march of progress I suppose :) $\endgroup$– voretaq7Commented Dec 10, 2014 at 22:04
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Birch, maple, oak, mahogany or walnut are good choices.
Wing spar material is usually sitka spruce which is too soft for propellers.
I would not sit on a sitka toilet seat either as the slivers from it are toxic.
