Propeller Shape

avzq
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Propeller Shape

Postby avzq » Thu Jun 15, 2017 11:00 am

If I'm trimming a 24 cm Ikara propeller down to 17 cm, is there an ideal shape to trim it down to? I'm using 3/32" FAI TSS rubber and somewhat of a low-winger with 1.5 cm posts (part of a kit), if that helps.

Here's an image of the prop:
http://www.freedomflightmodels.com/imag ... sembly.jpg

Here's one of the plane (with a pre-trimmed propeller):
http://www.lasercutplanes.com/web_image ... over_3.jpg

Additionally if I need to balance a prop with tape, where on the blade might it be most effective?

Thanks,

avzq

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JasperKota
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Re: Propeller Shape

Postby JasperKota » Thu Jun 15, 2017 10:15 pm

Following freedom flight instructions, I trimmed my propeller by just cutting the tips of the prop but keeping the original curved-tip shape. Measure from the hub (middle of the prop) to one blade of the prop 8.5 cm, and draw a line across with sharpie. Do the same with the other blade. Cut down the lines you drew. Now carefully trim the tips of the blade so it's curved like the original shape. Measure again making sure that it's 17cm or less (note that this year's rules allowed a 14cm prop). It's better (but more tedious) to balance propellers by cutting down on weight by sanding down the heavier side.
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avzq
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Re: Propeller Shape

Postby avzq » Thu Jun 15, 2017 11:19 pm

JasperKota wrote:Following freedom flight instructions, I trimmed my propeller by just cutting the tips of the prop but keeping the original curved-tip shape. Measure from the hub (middle of the prop) to one blade of the prop 8.5 cm, and draw a line across with sharpie. Do the same with the other blade. Cut down the lines you drew. Now carefully trim the tips of the blade so it's curved like the original shape. Measure again making sure that it's 17cm or less (note that this year's rules allowed a 14cm prop). It's better (but more tedious) to balance propellers by cutting down on weight by sanding down the heavier side.


Thanks for your reply. I'm currently competing in Technology Student Association in Flight Endurance, which has similar rules, at least on a general level. The kit I've used is from Laser-Cut Planes, which didn't specify propeller shape. Would it be better to keep the prop blade area closer to maximum rather than following the original blade curves? This is while keeping the blades reasonably aerodynamic (similar to in the second photo of the kit).

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JasperKota
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Re: Propeller Shape

Postby JasperKota » Thu Jun 15, 2017 11:44 pm

avzq wrote:Thanks for your reply. I'm currently competing in Technology Student Association in Flight Endurance, which has similar rules, at least on a general level. The kit I've used is from Laser-Cut Planes, which didn't specify propeller shape. Would it be better to keep the prop blade area closer to maximum rather than following the original blade curves? This is while keeping the blades reasonably aerodynamic (similar to in the second photo of the kit).


Sorry, I'm not sure. It probably depends on the plane, rubber length and width, etc. so I suggest testing both out and see what works better. Free flight is a ton of testing, recording results and adjusting. Let us know how it goes!
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Re: Propeller Shape

Postby avzq » Fri Jun 16, 2017 12:03 am

JasperKota wrote:
avzq wrote:Thanks for your reply. I'm currently competing in Technology Student Association in Flight Endurance, which has similar rules, at least on a general level. The kit I've used is from Laser-Cut Planes, which didn't specify propeller shape. Would it be better to keep the prop blade area closer to maximum rather than following the original blade curves? This is while keeping the blades reasonably aerodynamic (similar to in the second photo of the kit).


Sorry, I'm not sure. It probably depends on the plane, rubber length and width, etc. so I suggest testing both out and see what works better. Free flight is a ton of testing, recording results and adjusting. Let us know how it goes!


Okay, thanks again!


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