Building a wind deflector

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Frank B

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Apr 23, 2005
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Calgary, Alberta
I wonder how much an average person would pay (in $$) extra to have a better design of the trailer that would cut gas consumption, say by 20% or more....
Have a look at Airstream trailers. A lot of dollars for the aerodynamic benefits.
 

KeinNWO

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Apr 9, 2021
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3
Location
Kenora, ON
Hi. The perfect shape is a teardrop, big in the front and a tail in back to reduce back pressure or vacuum. The airstream trailer comes close. I have installed air tabs on the back edge of my apex 194 which claim to be vortex breakers, similar to dimples in golf ball. They claim 5%. I Saw maybe a reduction from 22 lp100 km to 21.5, which is maybe 2%. As said in the postings, the square rears cause the majority of drag. Many of commercial wings have builtin flow disrupters builtin.

1.5 l p 100 km improvement is actually fantastic.

I am looking for improvements to extend my range. I have a 26 gallon tank- 20 usuable gallons. I have taken off my KO2 LT tires and switched to Michelin LTX series tires.



Keith
Retired Mech. Engineer
2015 Tundra, Forest River Apex 194
22 litres per 100km or aprox. 10.7 mpg at 60 mpg.
 

steveblonde

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Jan 8, 2015
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calgary alberta
Hi. The perfect shape is a teardrop, big in the front and a tail in back to reduce back pressure or vacuum. The airstream trailer comes close. I have installed air tabs on the back edge of my apex 194 which claim to be vortex breakers, similar to dimples in golf ball. They claim 5%. I Saw maybe a reduction from 22 lp100 km to 21.5, which is maybe 2%. As said in the postings, the square rears cause the majority of drag. Many of commercial wings have builtin flow disrupters builtin.

1.5 l p 100 km improvement is actually fantastic.

I am looking for improvements to extend my range. I have a 26 gallon tank- 20 usuable gallons. I have taken off my KO2 LT tires and switched to Michelin LTX series tires.



Keith
Retired Mech. Engineer
2015 Tundra, Forest River Apex 194
22 litres per 100km or aprox. 10.7 mpg at 60 mpg.
Lmao im at 26 l per 100 pulling my rig as per previous post i would say your tabs need some attitude adjustments lol
4l per 100 is less than $5 difference
 

KeinNWO

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Apr 9, 2021
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Kenora, ON
Air Tabs are a brand name that stick on the side of the trailer. Gas mileage is nice, but want range, 4 hrs driving. At 60 mph..In northern Ontario I paid $1.50 per litre and gas stations can be more than 3 hrs apart.
 

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Gary RV_Wizard

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At our Silver Springs FL home
The problem with a deflector is that you need wind tunnel time to tune the design - the optimal design is rarely what is intuitive. You actually did extremely well to get 10% on your first try - less than 5% is more typical.

While frontal area resistance is a big factor, it's not the only aerodynamic consideration. For example, you have air flow under and alongside the rig, vortexes at the rear as air backfills, and a lot of turbulence along the roof where numerous things jut up. And then there are the non-aero factors like tire rolling resistance and dragging the extra weight up grades or accelerating it from a stop.
 

MoInEd

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May 27, 2020
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Location
Edmonton, AB
All good comments. My friend is actually thinking 10% is very good and thinks with improvement to the design it can get higher. As I said, there are commercial products for this purpose but from what I read their efficacy is lower. If there was a way to reduce the gap between the deflector and trailer significantly I think it would help a lot.

I agree there are a lot other factors. I thought about improvement to the front shape of the trailer but that's more difficult. As I said, when loaded up (both trailer and car) the consumption is around 21-22L/100km, so a 10% reduction there would be interesting.
 

steveblonde

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calgary alberta
Air Tabs are a brand name that stick on the side of the trailer. Gas mileage is nice, but want range, 4 hrs driving. At 60 mph..In northern Ontario I paid $1.50 per litre and gas stations can be more than 3 hrs apart.
Last May we pulled through from Calgary to London we were warned about the lack of stations and them being closed because of Covid we took 2 large jerry cans to be safe. Ended up using them east of Medicine Hat bucking a fierce head wind lol
 

MoInEd

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May 27, 2020
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Edmonton, AB
So this past few days I tested the wind deflector in the first real camping trip: 700+km (350 each way) to Rockies. Typically I average about 22L per 100km going (fully loaded and the elevation increasing) and around 18-19L per 100km coming back home.
This time I got 17.8L per 100km going and 16.3L per 100km coming back home.
That's a much better fuel efficiency than my simple 40km test run (with unloaded trailer). It's around 15-20% drop in consumption and is in line with what I had hoped for.
 

steveblonde

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calgary alberta
The key is going to be consistency. I pulled my trailer to drumheller 2 weeks ago used 1/2 tank of fuel pulled it home used a 1/4 tank
Then i pulled my trailer to lethbridge and back the following weekend and home i used 1 tank of fuel in total, difference is lethbridge is twice as far away as drumheller .
So why such a difference? One is flat driving one is very hilly, one day was windy driving one day was not.
And driving to Lethbridge the speeds are higher but i used less fuel.
 
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steveblonde

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calgary alberta
Its too subjective
Front wind
Side wind
Tail wind
Flats of saskatchewan
Hills of northern ontario
Temperatures air and humidity
Ac on? Off?
Tire pressure
Barometric pressure

Cost? Materials a few hundred bucks
Time? $100 hr x 15 hrs at least
Fuel $1.16 -$1.40 liter

Study window? Several weeks/trips
 

MoInEd

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Edmonton, AB
Steve I understand what you say but this trip from Edmonton to Rockies I do at least 4-5 times each summer and the numbers have always been in the same range. The drop with the deflector was way more than a noise. Looking at it from an engineering viewpoint, the weight of my trialed is 2/3 of my tow vehicle yet when hooked up the gas consumption was more than 3 times normal. Most of it I suspect is due to the drag, I.e. head pressure of air (extremely bad shape of the trailer). So even a slight measure to reduce the drag should have noticeable improvement in gas consumption.
 

steveblonde

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calgary alberta
Steve I understand what you say but this trip from Edmonton to Rockies I do at least 4-5 times each summer and the numbers have always been in the same range. The drop with the deflector was way more than a noise. Looking at it from an engineering viewpoint, the weight of my trialed is 2/3 of my tow vehicle yet when hooked up the gas consumption was more than 3 times normal. Most of it I suspect is due to the drag, I.e. head pressure of air (extremely bad shape of the trailer). So even a slight measure to reduce the drag should have noticeable improvement in gas consumption.
No offense my dad is an engineer charted recorded graphed everything and i mean everything - he still has mileage logs from our trip to San Diego in 1976 ( i love rummaging through them all and i have inherited the same phyco tendencies lol i love to compare) but until you are comparing environmental conditions which is why a wind tunnel comes into play your findings are inherently inaccurate. Please dont take me wrong i love the idea - but in order to work properly your defector needs to be much closer to the trailer ie mounted to the trailer to work but then you have the 3ft void between your audi and the trailer which causes drag.
Keep trying though and i will keep busting your chops till you get it right lol.
Like i said i loved those things as a kid they were supper cool 😎
 
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