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Old 05-05-2008, 12:55 PM   #1
abufletcher
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Default Designing stepped-layers for the propeller blank

Well, I'm back after a considerable absence from the forum. I'm finishing up a 1/6 scale model of a Sopwith Snipe and want to make a really nice static prop for it.

Actually I've already made one dummy prop that most people would probably think is nice enough. But in doing some research on the Bentley BRII engine I got my hands on a copy of L.K. Blackmore's book detailing the building of a working 1/4 scale model of the Bentley -- which, BTW, is absolutely mind-blowing. And there in the back of the book is a drawing of the propeller along with a description of how the author made his prop.

Anyway, it seems like the perfect excuse to do another static prop -- and do it to a higher standard. For one thing, the first prop was cut then carved from a single piece of pine. On the new one, I want to build the prop up out of layers of mahogany (no light and dark alterations).

The propeller drawings show a front view of one half of the blade plus the full hub, the side section showing the layers of wood (6) and the slope of the leading edge, and also airfoils at seven stations. This is far more information than I had for the first version.

But here's my problem. Rather than just glueing together 6 (somewhat expensive and hard to come by) sheets of mahogany and then cutting out the outline like I did last time, I'd prefer to build up the prop as they did "back then" with shaped layers forming the propeller blank. The edges were then carved down. This was done partially for economy but also to ensure that the grain of each layer was straight relative to the hub for maximum strength.

So my questions is this: Is there some drafting trick that will allow me to take the information from the front, side, and airfoil views and "project" the rough shape of each shaped layer in the blank?

Here a a couple of shots of the model so far:





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Old 05-05-2008, 01:05 PM   #2
abufletcher
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Here are a couple of shots of the first prop.



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Old 05-05-2008, 03:58 PM   #3
MWP_Lamar
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Unfortunately I cannot be of any assistance to you on your propeller. I DO wish to give you kudos on a fine looking model though.

Lamar
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Old 05-06-2008, 09:11 AM   #4
abufletcher
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Thank, Lamar. It was my experience producing a 1/6 scale version of an Imperial prop for an upcoming Albatroc CI project that really got me interested in wooden propellers and got me thinking about redoing the Snipe propeller.



But on this prop, I just slabbed all the layers together and cut out the prop outline with a band saw. This is very wasteful of wood that is both expensive an unavailable in Japan, where I live. It also doesn't let me experience building a prop in the "old-timey" way.

It just seems like there ought to be some easy way to figure out how to create each layer -- but that it's somehow eluding me.
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