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Disney Nautilus Hammer-head Propellor Testing

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Disney Nautilus Hammer-head Propellor Testing

Postby Davinci » Thu Jul 16, 2009 1:43 pm

Has anyone done any Testing of the Nautilus Hammer-head Propellor?
(Harper Goff designs)
Such as performance testing of rounded versus sharpened blade edges, flat-oval versus S shaped blades (both are in Disney drawings).
I want to optimize it's performance without altering it's appearance much and was hoping someone else had tried improvments already and had Info on those modifications?
Thanks,

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Postby Sub culture » Thu Jul 16, 2009 2:24 pm

I would leave it alone. Although it isn't the most efficient shape in the world, the sheer size and high pitch of it overcomes most of the inefficiency.

Flat blades are probably better than ellipsoid (about the worst shape for efficiency), filing a shallow radius on the back of the blade tips would probably help increase thrust a little.
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Postby Davinci » Thu Jul 16, 2009 2:40 pm

Sub culture wrote: filing a shallow radius on the back of the blade tips would probably help increase thrust a little.


Yes, that's what I was thinking. And sharpen the edges slightly at the same time, reducing drag. It seems the S shaped blades would be better, for Forward propulsion as well as Reverse braking.

Goff's drawing:
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Postby Sub culture » Fri Jul 17, 2009 5:17 am

It's about the worst shape imaginable. I don't know what they were thinking of drawing that shape.

You should aim for a shallow ogival shape at the tip of the blade.

Sharp edges aren't necessarily more efficient and they will damage very easily, especially as your prop is cast from aluminium.

At the end of the day,if efficiency is your goal, you ought to dispense with the original, or keep it for static. You would be better off making some blades fro sheet material, and giving them a true helical twist from hub to tip with a proper ogival blade shape on the back of the blades.

But, the Nautilus is far from an optimum design, it works well enough, but has huge amounts of parasitic drag, and the rakers resultin undesirable handling quirks at speed. If you want efficiency, build a Skipjack or a Valiant.
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Postby Bigdave » Fri Jul 17, 2009 1:26 pm

I was very supprised at the power the prop had on my Ray Mason Nautilus.
All I did to mine was heat the blades up to give them a bit more pitch otherwise it is stock.
She really hauls tail on a geared 540. 8) BD.
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Postby Davinci » Fri Jul 17, 2009 2:04 pm

Okay You've convinced me to try it the way is First, (flat with round edges)
since a geared 540 is what I'll be using also.
Do you know what pitch angle you ended up with?
Is your's a sheet-brass, cast or what?
The prop I have probably has a different angle than the one you have? Does it look similar to the picture above in first post?
I measured the angle to be 32 deg. on this one and I'll not be changing that angle (cast aluminum prop). I may be able to with the Resin props I intend to make tho.
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Postby Bigdave » Fri Jul 17, 2009 4:35 pm

I am not sure on the angle. She is packed away right now. :oops:
The prop is exact scale and is made of resin.
This is the best photo I had of the prop from a regatta many years ago.
You can kind of see the angle. :roll: BD.
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Postby Davinci » Fri Jul 17, 2009 6:32 pm

Thanks, Dave
Yes, that appears to be around 30.deg. pitch also.
I'm feeling better about this more all the time. :D

BTW- Great looking models!
I like the way you made the base/stand for it also.
(A real Drydock look)
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Postby Davinci » Sun Jul 19, 2009 8:38 pm

I made a mold and poured a hammer-head prop made of polyester resin yesterday. It's still a little too flexable but it seems to be getting more ridged. Guess it takes more time to cure completely than Epoxy does.
It looks good with no bubbles but this was to be just a test of the mold.
I'll pour an Epoxy one next and see how that compares.
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