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Old 10-22-2018, 11:27 AM
Veetail88's Avatar
Veetail88 Veetail88 is offline
Join Date: Oct 2008
Location: Hales Corners, WI
Posts: 1,040
Default Petit Jean Balloon Busting

Without question, the most fun at Petty Jean this past weekend, in my humble opinion, was the balloon busting competition!

Having spent pretty much 100% of the 530 hours I have on my 8 doing everything I can to avoid hitting anything, suddenly that is exactly what the goal is and it was a blast!

Having busted 2 of the 3 balloons that were sent aloft for my killer pursuit like so many pheasants on a game farm, I?m quite certain that the one I missed was as solid a hit as the others.

So I posited that it may be possible for the target to pass through the propeller arc unscathed; and that I was actually perfect as far as the required skill goes. Oh Lord it?s hard to be humble!

While I was waiting on the end of the runway for my heat to begin, I had a great perspective of the target zone, and cranked the exposure rate on my $150 E-Bay special Lumix camera up to a dozen frames per second and burned a lot of images.

Here we have a sequence of our own Professor Horton as he launches his assault on an unwitting target balloon; and given the three images, It certainly appears this one went right through!

So here?s the math. Flying at the targeted airspeed of 120 miles per hour, the forward speed equates to traveling at a rate of 2.112 inches for each 1/1000 of a second, or about 4.2 thousandths of a second for a 9? balloon to pass through the propeller disk.

In that same amount of time, a propeller turning at 2700 RPM will turn 69 degrees. (yes, please someone, check my math)

A 2 bladed prop, would cover 138 degrees, or only about 38% of the prop disc space, leaving the remaining 62% wide open.

I know this is imperfect as the balloon, being round, occupies different amounts of space at different times during the .0042 seconds it takes to pass through the disc, plus the prop has thickness, and the balloon might have been 11? in diameter, yada, yada, yada. But you get the picture.

So I?m concluding that even if you skillfully maneuver your vehicle of destruction with the precision of a brain surgeon (who may or may not still have his brain surgery kit), that this is in the end, partially a game of chance.

None the less, the game is a BLAST! And kudos to the Petit Jean Indians for making it happen!

All ya?all should try your hand at it. You won?t be disappointed!
Jesse Bentley (Queasy)
N229Z - RV-8 - Flying - Livin' the dream!
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Old 10-22-2018, 11:31 AM
Paul 5r4 Paul 5r4 is offline
Join Date: Oct 2006
Location: Foley, Al
Posts: 694
Default Interesting

Love those shots. Very interesting math/physics. In the second shot, comparing the size of the balloon to the wheel pant, it does appear to be right against the fuselage. For it to be that close to the fuse and still just a couple feet aft of the prop arc, it would seem that it MUST have passed through the arc unscathed!

Professor D. Horton! :-)
Paul Gray
Foley, Alabama
N729PG..... 500+ hrs
RV 7A, Lycoming 0 320 D1A, Sensenich FP propeller
VAF supporter $$$

Last edited by Paul 5r4 : 10-22-2018 at 11:39 AM.
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Old 10-22-2018, 12:01 PM
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scard scard is offline
Join Date: Jun 2005
Location: Cedar Park, TX
Posts: 3,411

It was indeed a hoot to watch from the ground! Super fun.
Scott Card
CQ Headset by Card Machine Works
CMW E-Lift
RV8 Building - fuselage / showplanes canopy. Last 90% reboot
RV-9A N4822C built flew 15yrs 2200+hrs.
VAF Advertiser
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Old 10-22-2018, 12:16 PM
rv7charlie rv7charlie is offline
Join Date: May 2006
Location: Pocahontas MS
Posts: 3,869

I could have given you empirical validation without the math. A former airpark neighbor had a duck put a 8" deep dent in the leading edge of his Debonair wing, inside the prop arc. No blood or damage on the prop.
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Old 10-22-2018, 12:54 PM
dweyant dweyant is offline
Join Date: Sep 2012
Location: 07TS
Posts: 526

I think the Petit Jean crew found a winner with this one.

Was a blast to watch, and next year I will participate!

Dan Weyant
Done and Flying 4/30/2015
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Old 10-22-2018, 12:54 PM
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M McGraw M McGraw is offline
Join Date: Dec 2012
Location: Greenback, TN
Posts: 606
Default Placing bets.

To DanH,
Please tell Patti I no longer want the five dollars I bet on you back
Marvin McGraw, 5TN4
RV-14. #140039 Complete
Flight hours: 875+
2022 Dues Paid
The Dues Paid note is a reminder for me

Last edited by M McGraw : 10-22-2018 at 01:00 PM.
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Old 10-22-2018, 01:31 PM
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DanH DanH is offline
Join Date: Oct 2005
Location: 08A
Posts: 11,076

Balloon is 9", speed is 2112 inches per second.

2700 RPM is 16200 degrees per second.

Thus (9 * 16200) / 2112 = 69 degrees during balloon passage.

Only 61 degrees if done at 2400.

Thank you Jesse. I feel soooo much better now.
Dan Horton
Barrett IO-390
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Old 10-22-2018, 01:53 PM
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scrollF4 scrollF4 is offline
Moderator, Asst. Line Boy
Join Date: Jan 2010
Location: Flower Mound, TX
Posts: 1,735

Ah! I should have had my prop in full RPM. That way I wouldn?t have missed the 2nd and 3rd balloons.

Sid "Scroll" Mayeux, Col, USAF (ret)
52F NW Regional/Aero Valley Airport, Roanoke TX (home of DR's Van Cave)
"KELLI GIRL" N260KM RV-7A tipper

Exemption waived.
Proud and grateful 2022 -=VAF=- Contributor

PS: I am not an influencer. I have no influence. Just ask my kids.
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Old 10-22-2018, 01:59 PM
dtw_rv6 dtw_rv6 is offline
Join Date: May 2008
Location: Martinsville, IN
Posts: 463

I was the lucky dog that managed to score all three of the balloons. The third one was a surprise to me- I don?t recall hearing the pop like the first two, and it was the only one that I failed to smack head on with the spinner. Sounds like having a 3 blades prop does increase your odds of a kill after all. Since the balloon had to roll off of my spinner after contact, I?m sure the time spent in the kill zone had to go up as well.

Too bad I didn?t have my hat cam on for this. It was really neat to see the ballon shards get flung around the canopy!

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Old 10-22-2018, 02:00 PM
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Veetail88 Veetail88 is offline
Join Date: Oct 2008
Location: Hales Corners, WI
Posts: 1,040

Originally Posted by DanH View Post
I feel soooo much better now.
Figured you would!
Jesse Bentley (Queasy)
N229Z - RV-8 - Flying - Livin' the dream!
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