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Old 11-30-2018, 06:42 PM   #1
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Have you ever heard of Vortex Generators?

Some place on one of the RV forums I read a post about vortex generators. These things are used on most airplanes to give them better lift, less drag and better slow speed control. You may be wondering why anyone would need them on a RV? Me too.
Without posting all of my searching I did find this video that has noting to do with the topic but is too good to pass up not posting: https://www.bing.com/videos/search?q...8&&FORM=VDRVRV
My next RV??

Back on topic. There are many great videos posted showing the positive effect of vortex generators on vehicles. With this understanding I started looking for a product for my coach. Because of price and design I chose there folks: https://airflowdeflector.com/home/vspoiler/
I bought the $199 set and applied the tabs to the rear of the coach as instructed. Didn't take much time or effort. Because of the 4 tab design it was very easy to place each set to line up in a neat look.

What did I notice when I drove the coach?
We just drove about 530 miles from Sonora, CA to Jamul, CA. We started our trip in the foot hills of the Sierra Mountains, went over the Grape Vine on I-5, around LA on I-405, back onto I-5, to 94 and into Jamul. We had a variety of terrain to travel and many different road conditions. One of the first things I noticed is that I was not steering as hard as usual. I had not realized that the coach had a slight tail waggle before I installed the v-spoilers. I also realized that the Blue Ox TruCenter seemed to be giving me better control and correction response. Next was to actively observe what happened when a truck passed or I passed a truck. The handling was much more stable and I didn't get that shoved feeling during the event. Also, only once during the total trip was I aware of wind. It seemed to be head-on and I could feel the coach pushing a bit harder.
Fuel economy is supposed to be another improvement with these things. I can't say. We got 8.2 mpg on the overall trip.

Another claim made was that of keeping the rear of the coach and tow cleaner. I do think this is true. We did not seem to pick up as much grime on the car or rear of the coach as usual.
Overall, I think these things were worth the money. Don't expect to save much fuel. There are just too many variables when on the random roads we travel. Was this a "scientific" study? Not hardly. Just my experiences and attempt to keep my rig a bit more stable on the road.

I have driven two trips since putting the v-spoilers on. Both gave me the same results. We are at this location for 6 months so I'll be doing a new study when we hit the road again. Next trip will be to the East Coast. That will be a real test.
I hope the pictures help to answer some of your installation questions, if any. You can click a picture to get a more detailed view. I didn't do the greatest job "enhancing" them, but they work.
Happy trails to all.

Rick Y.

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Old 11-30-2018, 10:28 PM   #2
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"These things are used on most airplanes to give them better lift, less drag and better slow speed control."


Most? No. I've been flying for 40 years, Cessna 150s to F-4s to C-130 and a bunch more, operationally and in test, and very few of them had vortex generators. If you look at the horizontal stab on a C-135, it has VGs. VGs are used in aviation to break the bow wave and hold the wind to a control surface, increasing parasitic drag and drastically increasing induced drag when the control surface is moved, making the control surface more effective. Bottom line, in aviation, VGs increase drag.
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Old 11-30-2018, 10:33 PM   #3
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Yep, Brett Wolfe (wolfe10 here) tested them some years ago on his motorhome
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Old 12-02-2018, 06:53 AM   #4
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Quote:
Originally Posted by Mr_D View Post
Yep, Brett Wolfe (wolfe10 here) tested them some years ago on his motorhome
I found wolfe10 on rv.net talking about this topic:
https://www.rv.net/forum/index.cfm/f...print/true.cfm
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Old 12-02-2018, 07:09 AM   #5
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Quote:
Originally Posted by TonyMac View Post
"These things are used on most airplanes to give them better lift, less drag and better slow speed control."


Most? No. I've been flying for 40 years, Cessna 150s to F-4s to C-130 and a bunch more, operationally and in test, and very few of them had vortex generators. If you look at the horizontal stab on a C-135, it has VGs. VGs are used in aviation to break the bow wave and hold the wind to a control surface, increasing parasitic drag and drastically increasing induced drag when the control surface is moved, making the control surface more effective. Bottom line, in aviation, VGs increase drag.
TonyMac, thank you for sharing about your years of experience flying and for your service to our great nation.
This topic is about RVs and RV performance issues. Please, lets stay on topic. If any RV I ever own takes to the sky I doubt I will live to tell about it.
As we all know, from our life experiences, drafting is a racing technique used by race car drivers in order to save fuel. Even truckers will do this. They will tuck there rig up close behind the rig in front of them and take advantage of the low pressure created by the back of the truck.

As I understand it, the vortex generators I installed help to reduce this effect. The air pressure at the immediate rear of the coach is increased thus reducing the negative pressure it that area and smooths the air flow passing over the rear of my coach. That is why I don't feel the abrupt shifting by passing trucks as I did before I installed them.
Many of us install many products in order to get better handling; sway bars, shocks, bell cranks, etc. This product is just another product for that purpose. In post #1 I have described what I have observed. I am not a dreamer. If I did not notice a change in the handling, improved or not, I would be aware of it.
For example, when this coach was first new to me I did not like the way it handled. It swayed a bit too much for my liking, rode rougher than I though it should and had a significant right pull. Over time I have addressed all of these issues with new shocks, tires, anti-sway devices in the air lines, a steering stabilizer, front end alignment and chassis tuneup. The V-generators is just the last of these many add-ons.

It is my experience, by driving my coach over 1000 miles, that these little tabs have helped to improve the performance of many of the other devices I have installed in order to get a more comfortable, stable and safer handling experience.

It will be about 6 months before I hit the road again. When I do I will be heading East, through some very different terrain, road and weather conditions than I have experienced while I have been here on the West coast. I look forward to seeing how the coach handles out on the great plains with the heavy cross winds.
Happy trails.
Rick Y
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Old 12-02-2018, 07:31 AM   #6
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The topic is aerodynamics. Aerodynamics affects anything moving thru the air; it affects ships, it's what makes a sail work. Aerodynamics is to a greater extreme at .98M, but the same factors affect motorhomes. Vortex generators create drag. Period. What you do with that drag depends on where the VGs are placed. The question then is this: Is the VG doing anything beneficial to overcome the cost of its drag?
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Old 12-02-2018, 07:34 AM   #7
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Quote:
Originally Posted by marjoa View Post
I found wolfe10 on rv.net talking about this topic:
https://www.rv.net/forum/index.cfm/f...print/true.cfm
"Wow-- OK I am Brett Wolfe aka Wolfe10.

And yes, I put Air Tabs on the top of the new coach. Have not put them on the sides-- have not found paint to match and have been told by the "boss" not to mess up the paint job."



Bad choice of reference for this discussion. He did not do a full installation. His observations are not valid.
If I told you that I built a new screen frame for my RV door but I never put screen in it, then complained that bugs were getting into my RV through it, would you consider my observations about the product quality worth while? I don't think so. Same with Wolfe10.
Other observers did post similar results as mine in that thread.
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Old 12-02-2018, 09:05 AM   #8
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Friends put air tabs on their 36' Tiffin. They claim 1 mpg improvement, less problems in wind and less sway with trucks passing them. They had them painted to match.
I would but I have a rear cap seam on the sides in the way, get almost 9 mpg now, and I'm not good at painting.
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Old 12-02-2018, 08:23 PM   #9
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So, why wouldn't the OEM of the RV install these if it increases MPG and reduce sway?
If retail price is $190, then the RV OEM will buy them for $20. For 1 MPG improvement? (10%)? They would be all over it.

So, just call me skeptical.
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Old 12-02-2018, 10:24 PM   #10
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Quote:
Originally Posted by TonyMac View Post
"These things are used on most airplanes to give them better lift, less drag and better slow speed control."


Most? No. I've been flying for 40 years, Cessna 150s to F-4s to C-130 and a bunch more, operationally and in test, and very few of them had vortex generators. If you look at the horizontal stab on a C-135, it has VGs. VGs are used in aviation to break the bow wave and hold the wind to a control surface, increasing parasitic drag and drastically increasing induced drag when the control surface is moved, making the control surface more effective. Bottom line, in aviation, VGs increase drag.
Yep. VGs are installed to fix an aerodynamic design flaw. Look at the wing of an older Lear Jet.
If these things were the cats meow, everyone would have them.
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Old 12-03-2018, 06:10 AM   #11
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It looks to me like a Motor Coach is an Aerodynamic Design Flaw from bumper to bumper!
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Old 12-03-2018, 06:45 AM   #12
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Quote:
Originally Posted by TonyMac View Post
The topic is aerodynamics. Aerodynamics affects anything moving thru the air; it affects ships, it's what makes a sail work. Aerodynamics is to a greater extreme at .98M, but the same factors affect motorhomes. Vortex generators create drag. Period. What you do with that drag depends on where the VGs are placed. The question then is this: Is the VG doing anything beneficial to overcome the cost of its drag?
In all due respect, sir, the forum is a RV forum. The topics discussed are about RVs. Limiting my observations to the aerodynamics of RVs is appropriate and the only valid first had observations I can make. The purpose of the VGs is not what you are focusing on and your comments are off the topic of this discussion. Please try to think in terms of this limited application and environment. Apply your great experiences to this model and consider just what the VGs are designed to do as positioned on an RV or semi style cargo or people carrying body. Think out side the limits of your box of flying experiences. Join me in my arena. I am not in yours and have no intention of going there.

I drive and live in a RV. 32,000+# of land bound box on wheels. This is my world and I love it. Making it a bit safer and easier to drive on long hauls is a good thing at my age. The VGs helped me achieve this.

For those interested in fuel mileage improvements, you may be disappointed. Those who drive a fixed route may be able to accurately measure changes (improvements) in fuel mileage. But, for the majority of us, we drive in ever changing conditions. There is no practical way to accurately tell if we are getting better mileage or not.


Consider driving in heavy traffic at about 63 mph on a multi-lane (I-5) highway with narrow lanes. With a cross wind, this can be a bit of a challenge in a RV like mine when traffic is heavy. Toss in passing or being passed by large semis or tour buses, things can get a little dicey. Anything that improves handling in situations like this, within my budget, is a good improvement to consider and apply. The VGs are a valued addition to the improvements I have made in this regard. Money well spent.
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Old 12-03-2018, 07:18 AM   #13
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Technically, how do VGs have effect to neutralize a cross wind?

The way I am looking at this, is a cross wind is hitting the side of the RV, which, because the RV is a moving wall, the wall gets pushed in the direction of the wind. How does the VG minimize this effect?

For large passing vehicles - the vehicle to the side is deflecting wind off it's front which makes some of that a sidewards motion. Same question.

Those passing vehicles also create a tail vacuum which tends to suck In vehicles to their side.

And, large vehicles in the front (semis) also disturb the air and create buffeting behind them. Possibly the VGs help to straighten some of this disturbance? Not sure if it helps the VG equipped vehicle, but possibly the one behind it (who cares)?

Would be interesting to see a wind tunnel smoke test to see the air patterns with and without.

"Those who drive a fixed route may be able to accurately measure changes (improvements) in fuel mileage. But, for the majority of us, we drive in ever changing conditions. There is no practical way to accurately tell if we are getting better mileage or not."
Over time, if there is a benefit, the numbers should show it. If you can't see a difference, then there is none.
My expectation is zip nadda nuthin of a difference. But who knows...

I would expect that there is more research on the topic for airplanes on how VGs work and for what reasons. So, with extrapolation, that is interesting input if we can't find any legitimate info from RV application. I suspect there will be little real research found.
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Old 12-03-2018, 09:00 AM   #14
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Quote:
In all due respect, sir, the forum is a RV forum. The topics discussed are about RVs. Limiting my observations to the aerodynamics of RVs is appropriate and the only valid first had observations I can make. The purpose of the VGs is not what you are focusing on and your comments are off the topic of this discussion. Please try to think in terms of this limited application and environment. Apply your great experiences to this model and consider just what the VGs are designed to do as positioned on an RV or semi style cargo or people carrying body.


In all due respect sir,

Tony Mac is correct. If this is a discussion about VGs it is a discussion about aerodynamics. And you should note that aircraft are people carrying bodies.

The definition of aerodynamics:
aer∑o∑dy∑nam∑ics
[ˌerōˌdīˈnamiks]
NOUN
1. the study of the properties of moving air and the interaction between the air and solid bodies moving through it.
ē the properties of a solid object regarding the manner in which air flows around it.

Note it references "solid bodies" (as in an RV) not just aircraft.


As you, and anyone else researching this topic, has found, there are no, well done, engineering studies of VGs on RVs.

A few studies have been done on motor vehicles most of which were by the makers of the VGs. As such, most, put little credence in their claims.


99.9% of well conducted engineering/scientific studies have been performed on VG effects on aircraft.

Much of this data can be applied to the effects of VGs on any body moving through the air including RVs


Since there appear to be no RV specific studies of VGs you are limiting this conversation to limited anecdotal evidence of the very few who have put them on an RV.

The impact of VGs on anything is so minimal as to require sophisticated analysis with expensive equipment Otherwise the only comments you can make will be:

I put VGs on my RV and

it seems to increase mileage.
I think it handles better.

Discussing VGs without discussing aerodynamics and the source of almost all of the related data usually devolves into wishful thinking, or at best the never ending discussions like, the cheap handling fix, and CDLs required to drive an RV.
From these type discussions one can always find an answer that they are looking for.



Like Tony Mac I have considerable experience with VGs effects on experimental aircraft. But given the original posters request I can say nothing about VGs and RVs as I have no experience in this "arena" and my engineering brain will not let me think outside the box.
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