Register Now
 Remember

 05-14-2017, 08:32 PM #1 (permalink) Master EcoModder     Join Date: Feb 2011 Location: Phillips, WI Posts: 939 Nameless - '06 GMC Canyon 90 day: 31.82 mpg (US) Thanks: 179 Thanked 362 Times in 233 Posts Radio Antenna Drag I have not removed my radio antenna, which was commented on in at least one thread. Now I know why because I finally did the calculation for drag from my radio antenna. Here's the calculation: INPUTS Antenna diameter 5/32" Antenna length 29" Air density 0.075 lb/ft3 Viscosity of air 3.8E-7 lb-sec/ft2 Speed 80 ft/sec (just under 55 MPH) CALCULATIONS Reynolds number = 0.156" / 12 in/ft X 0.075 lbs/ft3 / 32.2 ft/sec2 / X 80 ft/sec / 3.8E-7 lb-sec/ft2 = 6400 Cd for a cylinder at Re 6400 = 1.0 Drag = 0.5 X Cd X A X rho X V2 = = 0.5 X 1.0 X 0.156" / 12 in/ft X 29" / 12 in/ft X 0.075 lb/ft3 / 32.2 ft/sec2 X 80^2 ft2/sec2 = 0.234 lbs drag from the radio antenna At 80 ft/sec, this is 0.234 lbs X 80 ft/sec = 19 ft-lbs/sec = 0.034 hp (1 hp = 550 ft-lbs/second). The radio antenna air drag requires 0.034 hp (0.025 kw) I averaged 35 MPG last year. If we simplify by assuming all driving was at that speed, then fuel flow was 55 MPH / 35 MPG = 1.57 gallons/hour = 9.4 lbs/hour. Power is estimated by assuming 0.5 lbs/hp-hr, so 9.4 lbs/hour / 0.5 lbs/hp-hr = 18.857 hp. Removing the radio antenna would reduce this to 18.857 - 0.034 = 18.823 hp. The resulting estimated gas mileage would be 35 MPG X 18.857 / 18.823 = 35.06 MPG. I would gain an estimated 0.06 MPG. I drove 10,588.6 miles last year. That would be 302.53 gallons at 35 MPG, and 302.01 gallons at 35.06 MPG. The radio antenna cost me 0.52 gallons of fuel last year. The actual savings would be less because part of my driving is at slower speeds. I will pay that cost in order to listen to the radio once in a while. __________________ The vacuum gauge plus wheel covers helped increase summer 2015 mileage to 38.5 MPG, while summer 2016 mileage was 38.6 MPG without the wheel covers. Drove 10,708.4 miles in 2017 at 35.5 MPG.
 The Following 8 Users Say Thank You to JRMichler For This Useful Post: ajohn7211 (06-18-2017), BabyDiesel (05-15-2017), BamZipPow (05-16-2017), ChopStix (05-15-2017), Ecky (05-16-2017), mcrews (05-16-2017), MorphDaCivic (05-15-2017), oldtamiyaphile (05-14-2017)
 Today Popular topics Other popular topics in this forum...
 05-14-2017, 10:20 PM #2 (permalink) Master EcoModder   Join Date: May 2012 Location: Indiana Posts: 1,248 Traverse 2LT FWD - '12 Chevrolet Traverse 2LT Volt, gas only - '12 Chevrolet Volt Premium 90 day: 38.85 mpg (US) Volt, electric only - '12 Chevrolet Volt Premium 90 day: 117.86 mpg (US) Thanks: 99 Thanked 265 Times in 174 Posts Im actually surprised it was that much. __________________
 The Following User Says Thank You to ksa8907 For This Useful Post: mcrews (05-16-2017)
 05-15-2017, 12:07 AM #3 (permalink) Primer is still paint!     Join Date: Aug 2015 Location: box by the river Posts: 403 Thanks: 66 Thanked 83 Times in 66 Posts I think some older cars would be worse as they had brick shaped antenna bases. But I would not remove it either, gotta have my tunes!
 05-15-2017, 01:30 AM #4 (permalink) Polymorphic Modder     Join Date: Aug 2010 Location: Utah Posts: 304 2006 DaCivic Hybrid - '06 Honda Civic Hybrid 90 day: 45.16 mpg (US) Thanks: 186 Thanked 38 Times in 23 Posts Wonder what the flags and Mascots add to the drag. Also here in Utah when the FANatics go to athletic events they have two flags fluttering on both sides of the car.
Primer is still paint!

Join Date: Aug 2015
Location: box by the river
Posts: 403
Thanks: 66
Thanked 83 Times in 66 Posts
Quote:
 Originally Posted by MorphDaCivic Wonder what the flags and Mascots add to the drag. Also here in Utah when the FANatics go to athletic events they have two flags fluttering on both sides of the car.
Or the Jack Balls! -lol

 05-15-2017, 12:44 PM #6 (permalink) Master EcoModder     Join Date: Jul 2011 Location: Ann Arbor, Michigan Posts: 2,718 Thanks: 3 Thanked 1,709 Times in 1,204 Posts Just think of all the gas that radio can save you when avoiding traffic jambs and road construction. __________________ George Architect, Artist and Designer of Objects 1977 Porsche 911s Targa 1998 Chevy S-10 Pick-Up truck 1989 Scat II HP Hovercraft Chin Spoiler: http://forums.pelicanparts.com/off-t...effective.html Rear Spoiler Pick Up Truck http://forums.pelicanparts.com/off-t...xperiment.html Roof Wing http://ecomodder.com/forum/showthrea...1-a-19525.html
 05-16-2017, 01:51 AM #7 (permalink) EcoModding Lurker   Join Date: May 2016 Location: Virginia Posts: 9 Thanks: 0 Thanked 3 Times in 3 Posts Thanks for doing the calculations.....now I won't feel too bad about adding my wilson 5000 CR antenna to the roof..... .06 MPG is hardly anything! (graned the wilson 5000 is taller but even double the mpg loss is still not too much). As an aside, with your great mathematical skills, would it be possible to calculate how many MPG's one would gain by removal of side mirrors or conversely how much one would lose if one were to add vent visors (to allow one to keep the side windows open without fear of rain getting in). Thanks in advance for any and all help. Andrew __________________ 2003 Jetta TDI Wagon, 5 sp, 210K miles, Stock.....for now!
 05-16-2017, 12:24 PM #8 (permalink) EcoModding Lurker   Join Date: Apr 2017 Location: da U.P. Posts: 36 Thanks: 2 Thanked 4 Times in 4 Posts You donut always have to remove the antenna. A more efficient design might be possible, otherwise on my saturn I was able to move the antenna inside the a pillar or fender. You just need to get creative
 05-16-2017, 12:53 PM #9 (permalink) Master EcoModder     Join Date: Dec 2011 Location: Vermont Posts: 2,346 Gaptooth - '00 Honda Insight Team HondaGen-1 Insights 90 day: 56.86 mpg (US) Such Fit - '07 Honda Fit Sport 90 day: 41.27 mpg (US) Thanks: 772 Thanked 880 Times in 557 Posts 1600 ways to save an ounce. Plus, not everything I do needs to have a positive ROI. EDIT: Only problem now is, I'm going 3-4 months between tanks of gas. __________________ 2000 Insight TLC & Build Thread HCH1 Ecomodding
Master EcoModder

Join Date: Aug 2012
Location: northwest of normal
Posts: 10,234
Thanks: 2,273
Thanked 3,231 Times in 2,543 Posts
Quote:
 As an aside, with your great mathematical skills, would it be possible to calculate how many MPG's one would gain by removal of side mirrors or conversely how much one would lose if one were to add vent visors (to allow one to keep the side windows open without fear of rain getting in).
Not saying he shouldn't give it a shot, but mirrors and visors ride within the turbulent boundary layer, while the antenna stands out. The situation is much more complex. That's why the Nissan Leaf has little glass fins on the headlight, to set up airflow across the rear-view mirrors a foot or two further back.

One might solder a 1/8" by 1/4" Isosceles triangle on the back side and hand file a Template profile.