Wright Stuff C

newflight
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Re: regarding to propeller selection

Postby newflight » February 3rd, 2019, 6:51 pm

I have several propellers which are the same size with same pitch, however, the mass are very different, the heaviest is 2.3g and the lightest is 1.7. I would like to get some inputs on which propeller should be the best to use. I think the 1.7g should be the best, this will give the best weight balance. If I use 2.3g, it might make nose too heavy.
Are they ikara props? Just curious.
yes

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CrayolaCrayon
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Re: regarding to propeller selection

Postby CrayolaCrayon » February 3rd, 2019, 7:19 pm

I have several propellers which are the same size with same pitch, however, the mass are very different, the heaviest is 2.3g and the lightest is 1.7. I would like to get some inputs on which propeller should be the best to use. I think the 1.7g should be the best, this will give the best weight balance. If I use 2.3g, it might make nose too heavy.
Are they ikara props? Just curious.
yes
What are the bead colors?
Wright Stuff National Runner-up 2019
USA F1D Team 2020

newflight
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Re: regarding to propeller selection

Postby newflight » February 3rd, 2019, 7:24 pm


Are they ikara props? Just curious.
yes
What are the bead colors?
red

jinhusong
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Re: Wright Stuff C

Postby jinhusong » February 3rd, 2019, 8:59 pm

After saw the message, I checked what we have, 2.20, 2.17 and 1.72g. All red bead.

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CrayolaCrayon
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Re: Wright Stuff C

Postby CrayolaCrayon » February 4th, 2019, 4:10 am

Are red props discontinued from FF? I have a whole box of them, but am not sure how they differ from the yellow beads? Are they just vintage?
Wright Stuff National Runner-up 2019
USA F1D Team 2020

bjt4888
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Re: Wright Stuff C

Postby bjt4888 » February 4th, 2019, 6:43 am

Jinhusong,

Try testing the thickness of the plastic blades. This year, for the first time, we have discovered variations in the thickness ranging between .007” and .010”. It appears that the plastic stock is not being kept consistent as each different thickness material is that thickness over the entire blade.

The best way to determine best is to fly them.

Brian T

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Re: Wright Stuff C

Postby jinhusong » February 4th, 2019, 9:10 am

Jinhusong,

Try testing the thickness of the plastic blades. This year, for the first time, we have discovered variations in the thickness ranging between .007” and .010”. It appears that the plastic stock is not being kept consistent as each different thickness material is that thickness over the entire blade.

The best way to determine best is to fly them.

Brian T
Hi Brian,

You are right. I can even feel the difference by hand. The measured thickness matches your range.

More questions, what's the tolerance between two blades in pitch? We found 5 degree difference at the widest chord but 1 degree difference at 75%. Any method for us to test dynamic balance of the prop? I tried rotate with rubber band and winder, while hand holding the prop hanger, cannot tell.

Thanks for your help,

Jinhu




Best,

Jinhu

bjt4888
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Re: Wright Stuff C

Postby bjt4888 » February 4th, 2019, 10:37 am

Jinhusong,

Good job measuring and testing. The out of the box pitch variation you mention is typical. My teams will twist the center spar (as shown in the Freedom Flight kit instructions) both to get pitch to match within 1-2 degrees at a predetermined radius and to change pitch overall for testing. Also, twisting the blade in localized areas to make the pitch equal all along the blade will give you a helical pitch distribution. Helical pitch distribution is fairly efficient and equal pitch along each blade (or, at least, known pitch along each blade) improves analysis of testing results.

Good question.

Brian T

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Re: Wright Stuff C

Postby bjt4888 » February 4th, 2019, 1:41 pm

Jinhusong,

Sorry, missed the dynamic balance question. Very even pitch between the two blades, combined with perfect static balance and perfectly straight shaft will improve the let down duration. This is a very fine adjustment, of course and not nearly as important as matching propeller to rubber, having a very good propeller and winding correctly. I would gues that having a perfectly balanced propeller (dynamically and static) might be worth 5 seconds.

Brian T

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Re: Wright Stuff C

Postby jinhusong » February 4th, 2019, 1:48 pm

Jinhusong,

Sorry, missed the dynamic balance question. Very even pitch between the two blades, combined with perfect static balance and perfectly straight shaft will improve the let down duration. This is a very fine adjustment, of course and not nearly as important as matching propeller to rubber, having a very good propeller and winding correctly. I would gues that having a perfectly balanced propeller (dynamically and static) might be worth 5 seconds.

Brian T
Hi Brian,

Got it.

Thanks,


Jinhu


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