Save fuel on every trip made with a horse trailer or caravan and Splash out more on holiday

Feb 22, 2021
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The money you are saving for caravaning should not burn with fuel but it should be well spent on yourself. Even though you have the most aerodynamic towing car does not mean it will give you the best fuel efficiency while towing a caravan. The aerodynamic of vehicles-trailer combination is complicated and strongly dependent on the turbulence in the region of the rear of a car, the front and rear face of a caravan. The flow separation at the front and rear face of the trailer leads to an unfavourable pressure gradient which causes high drag force (opposing force to the vehicle motion). At higher travelling speeds (e.g. 60mph), more than 50% of the power generated by the engine is consumed to overcome the drag force.
Being a researcher in the field of Computational Fluid Dynamics, we have researched several flow-modifying devices named AERO TREK. The performance of these devices has been tested in the wind-tunnel and Computational Fluid Dynamic software. The Aero Trek devices have the potential to reduce the fuel consumption of towing car by 10 to 15%. One of the concepts of these devices is shown in the figure below. The device guides the flow on top of the trailer and reduces the turbulence region in the gap between the car and caravan.

I would like to discuss with the caravan community, which value proposition would you like to add to the Aero Trek devices.
  • An inexperienced person can easily attach and detach
  • Very little effort is required
  • Less than 10 minutes required to attach and detach
  • Foldable and ease of storage
  • Reduce chip damage
  • Quick return on investment


This post is not a marketing pitch but a part of a PhD research carried at the University of Huddersfield to survey the interest of caravan and horse trailer owners and users. The purpose of the post is to understand the pains and gains of caravan and horse trailer users and use your feedback in value addition and further research and development process. I am pleased to have your opinion on such devices which can reduce fuel consumption and contribute to the global Green Environment campaign. I am happy to share further information and discuss the performance of the Aero Trek devices in the comment area.
 

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Jun 16, 2020
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Welcome to the forum.

Not new! Plenty of roof deflectors around 20 years ago. I had one. Logic dictates they are sensible and should work. But my experience, and I believe that of other, was that fuel saving benefits were marginal.

Unless there is somthing different in what is suggested by the OP

John
 
Feb 22, 2021
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Thanks John,
I completely agree with you. Having a deflector on the car is not new. But we are researching mainly 3 things in this research. First is closing the gap between car and caravan partially and completely. This will resolve the turbulent region behind the car which will significantly improve fuel efficiency.
Secondly, we have developed a device called rolling pin/moving boundary which accelerates the incoming flow on the caravan and keeps the flow attached to the caravan body and also reduce the low-pressure region behind the caravan.

The third device is an improvement in the conventional deflector. The flow characteristic does not stay constant at different speeds. It is important to find out what is the optimum position of the deflector at different speeds. Very detailed research has been carried on finding out the relation between speed and position (angle) of the deflector. A control system is designed which can not only sense the speed of the vehicle but also capable to adjust the best position to keep the fuel consumption low.

Atif
 
Jun 16, 2020
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Thanks John,
I completely agree with you. Having a deflector on the car is not new. But we are researching mainly 3 things in this research. First is closing the gap between car and caravan partially and completely. This will resolve the turbulent region behind the car which will significantly improve fuel efficiency.
Secondly, we have developed a device called rolling pin/moving boundary which accelerates the incoming flow on the caravan and keeps the flow attached to the caravan body and also reduce the low-pressure region behind the caravan.

The third device is an improvement in the conventional deflector. The flow characteristic does not stay constant at different speeds. It is important to find out what is the optimum position of the deflector at different speeds. Very detailed research has been carried on finding out the relation between speed and position (angle) of the deflector. A control system is designed which can not only sense the speed of the vehicle but also capable to adjust the best position to keep the fuel consumption low.

Atif
I will follow in anticipation Of learning more.

John
 
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Parksy

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Nov 12, 2009
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The efficiency of wind deflectors on towing vehicles is not only governed by wind speed, direction of travel and the variance of angles between the towing vehicle and the trailer or caravan will also be factors which have to be taken into account when attempting to reduce drag and fuel consumption.
There has to be a gap between car and caravan for maneuverability when cornering and on sites, and caravan stability can sometimes depend to some extent on the length of the A frame.
Any deflector control system would have to have automatic directional adjustment that was capable of computing the infinitely variable wind direction in relation to both the towing vehicle and the trailer which can also be variable.
The deflector would need to be marketed at a price point that would make investment in one worthwhile.
It's a big ask.
 
Mar 14, 2005
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Hello Atif

What appears to be new here is the notion of aerodynamically filling the gap between the tow vehicle and the trailer.

I am sure such a device could make a difference, especially with the prospect of eeking out the range for EV's over the next few years.

I'm sure you are aware of the former wind deflectors, and it does seem that your proposal addresses several of their disadvantages.

If this is to become a viable product at the end of your Phd, please take the following comments as aspects you would need to consider during the development of the product.

As for the potential savings, You're suggesting that a user might see a 10 to 15% improvement in towing MPG. If that is actually achieved that would be significant, But do be careful about overstating such things, as the wind defector manufacturers fell foul of building up expectations that could not be achieved in practice.

I suspect a product of this type will have to be sold on its ability to offset its cost against the cost of fuel used when towing a caravan. Based on 2015-2019 data from MOT tests the pre covid19 average car mileage is about 7000miles. Unfortunately there is no hardened data that tells what the average caravan mileage is , and I know it will vary significantly, but I'd guess its on average no more than 10% or 700 miles, as most UK caravans stay within the UK. Would the savings on such a relatively low number of towed miles be enough to fund the purchase of one of your units? Without a guide price that's difficult to answer, but I'd guess it would take several years to recoup the cost.

Most caravanners don't see the extra cost of towing fuel as a major concern or inconvenience, so convincing them its going to save them money is a bit of an uphill struggle.

The only other compelling reasons to spend on an item like this is if it provides a safety benefit or becomes a fashion statement. You certainly haven't suggested a safety benefit and I don't think I see one unless it makes the outfit much less sensitive to bow waves from other vehicles.

From your description I glean the unit will have to be made of flexible materials to accommodate the articulation of the outfit, and multiple variations of size and body types of vehicles and trailers. that makes me wonder if fabric is the intended material. That has other issues primarily if its flexible enough to allow articulation then there is every likely hood the material will flap at speed. This might be both visually and audibly distracting.

Flapping material wears out (like flags do) also if it rubs on painted or plastic surfaces it can cause damage.

As a driver I would not be happy asking an inexperienced person to fit such a device. The driver should always check an attachments before setting off.

For many there could be quite an effort to reach the leading edge of the caravan to attach it.

I also wonder if you have carried out any research into the frontal areas of real caravans? Most of the current designs are already highly raked and smoothed to offer less frontal drag. This would mean your hood would have to be even longer to cover the tow hitch gap for less of benefit.

As a research project into aerodynamics I'm sure it will be interesting but I strongly suspect as a commercial project there are a lot of real challenge's to overcome.

I hope my concerns are wrong, so I wish you luck.

Please do keep us informed of progress and outcomes.

Pr.JL
 
Nov 16, 2015
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Atif, how is this addition supposedly to be attached between the car and the Caravan / horse box. Does it cover the sides as well or just the top,
How does it effect the exhaust gasses from the towing vechile.
These are hopefully constructive comments and not meant to be destructive to your groups investigations.
I am looking at it as a caravanner and an Aircraft engineer.
 
Nov 11, 2009
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I obtain around 2-3 mpg improvement in fuel economy when my Hapro Traxer roof box is fitted. In such circumstances the car will also be well loaded. I drive a Subaru Forester XT which isn’t top of the league for fuel economy. So I could just fit the roof box every time I tow the caravan on a trip. The reason I don’t is that it often prevents entry to some car parks due to the increased height.
 
Jul 18, 2017
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Interesting, but old hat. What would the saving be towing 200 miles? Also why do all this research revolving around fossil fuels when we are supposed to changing to EVs?
 
Nov 11, 2009
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Interesting, but old hat. What would the saving be towing 200 miles? Also why do all this research revolving around fossil fuels when we are supposed to changing to EVs?
Battery range could be improved as the device wouldn’t know what propulsive unit the tow car had installed.
 
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Jul 18, 2017
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Battery range could be improved as the device wouldn’t know what propulsive unit the tow car had installed.
How many EVs on the market are type approved to tow and if they could the range is severely limited so need to charge up probably twice on a 200 mile trip so doesn't really make sense to look at "fuel" saving as it probably would be negligible in the grand scheme of things.
 
Nov 11, 2009
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How many EVs on the market are type approved to tow and if they could the range is severely limited so need to charge up probably twice on a 200 mile trip so doesn't really make sense to look at "fuel" saving as it probably would be negligible in the grand scheme of things.
I was looking more to the future rather than at today’s EVs. Any principles developed during such research would carry forward into tomorrow’s vehicles. Which are being busily developed now.

But having studied aerodynamic effects in wind tunnels on the interaction between ships and helicopters I’m not sure that there is enough academic “ meat” in the OPs chosen subject. The last thing you want to do in a Phd is come across a blind alley after 6-12 months.
 
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Jul 18, 2017
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I was looking more to the future rather than at today’s EVs. Any principles developed during such research would carry forward into tomorrow’s vehicles. Which are being busily developed now.

But having studied aerodynamic effects in wind tunnels on the interaction between ships and helicopters I’m not sure that there is enough academic “ meat” in the OPs chosen subject. The last thing you want to do in a Phd is come across a blind alley after 6-12 months.
I think the only way is some sort of concertina device between the rear of the car and the front of the caravan and of course that is probably impractical!
The OP should really be looking at the practicality of towing a caravan with an EV and recharging with a caravan in tow. Would the EV also be charging the caravan battery while in transit?
 
Feb 22, 2021
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The efficiency of wind deflectors on towing vehicles is not only governed by wind speed, direction of travel and the variance of angles between the towing vehicle and the trailer or caravan will also be factors which have to be taken into account when attempting to reduce drag and fuel consumption.
There has to be a gap between car and caravan for maneuverability when cornering and on sites, and caravan stability can sometimes depend to some extent on the length of the A frame.
Any deflector control system would have to have automatic directional adjustment that was capable of computing the infinitely variable wind direction in relation to both the towing vehicle and the trailer which can also be variable.
The deflector would need to be marketed at a price point that would make investment in one worthwhile.
It's a big ask.
I understand your concerns and completely agree with you. Recently we have researched and developed a variable deflector that adjusts the height with changing velocity and shape of the tractor-trailer. we are looking to design something similar for caravans too. The challenge is to develop a generic design of a deflector that can cover almost all types of the caravan. It requires a huge amount of simulations to get the optimum position in different scenarios. This Gap seal was a different idea that can be adopted for any shape. The only challenge I have seen so far is to meet the legislation which says there should be a gap between car and caravan for manoeuvre action. Although manoeuvering can be adjusted by keeping the front end (car side end) of deflector free on the roof without any fixed attachment or some sliding mechanism which will probably affect the cost.
 
Feb 22, 2021
5
7
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Hello Atif

What appears to be new here is the notion of aerodynamically filling the gap between the tow vehicle and the trailer.

I am sure such a device could make a difference, especially with the prospect of eeking out the range for EV's over the next few years.

I'm sure you are aware of the former wind deflectors, and it does seem that your proposal addresses several of their disadvantages.

If this is to become a viable product at the end of your Phd, please take the following comments as aspects you would need to consider during the development of the product.

As for the potential savings, You're suggesting that a user might see a 10 to 15% improvement in towing MPG. If that is actually achieved that would be significant, But do be careful about overstating such things, as the wind defector manufacturers fell foul of building up expectations that could not be achieved in practice.

I suspect a product of this type will have to be sold on its ability to offset its cost against the cost of fuel used when towing a caravan. Based on 2015-2019 data from MOT tests the pre covid19 average car mileage is about 7000miles. Unfortunately there is no hardened data that tells what the average caravan mileage is , and I know it will vary significantly, but I'd guess its on average no more than 10% or 700 miles, as most UK caravans stay within the UK. Would the savings on such a relatively low number of towed miles be enough to fund the purchase of one of your units? Without a guide price that's difficult to answer, but I'd guess it would take several years to recoup the cost.

Most caravanners don't see the extra cost of towing fuel as a major concern or inconvenience, so convincing them its going to save them money is a bit of an uphill struggle.

The only other compelling reasons to spend on an item like this is if it provides a safety benefit or becomes a fashion statement. You certainly haven't suggested a safety benefit and I don't think I see one unless it makes the outfit much less sensitive to bow waves from other vehicles.

From your description I glean the unit will have to be made of flexible materials to accommodate the articulation of the outfit, and multiple variations of size and body types of vehicles and trailers. that makes me wonder if fabric is the intended material. That has other issues primarily if its flexible enough to allow articulation then there is every likely hood the material will flap at speed. This might be both visually and audibly distracting.

Flapping material wears out (like flags do) also if it rubs on painted or plastic surfaces it can cause damage.

As a driver I would not be happy asking an inexperienced person to fit such a device. The driver should always check an attachments before setting off.

For many there could be quite an effort to reach the leading edge of the caravan to attach it.

I also wonder if you have carried out any research into the frontal areas of real caravans? Most of the current designs are already highly raked and smoothed to offer less frontal drag. This would mean your hood would have to be even longer to cover the tow hitch gap for less of benefit.

As a research project into aerodynamics I'm sure it will be interesting but I strongly suspect as a commercial project there are a lot of real challenge's to overcome.

I hope my concerns are wrong, so I wish you luck.

Please do keep us informed of progress and outcomes.

Pr.JL
Thanks Pr.Jl.
I was not expecting such a detailed and critically reviewed comments. I am happy to see your interest. In respond to your concerns, this idea is still in development phase and this is the main reason why I thought it would be a good idea to have other people's opinion. This has really broadened my way of thinking.
I have simulated few shapes which has shown more than 10% percent fuel saving. The next challenge is the safety and design cost of this product now. Whether people want to buy it. I will keep updated once I have answers of your questions.
Thanks
 
Jan 19, 2002
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The original wind deflector was never popular, but as I recall fixed to the gutters on the edges of the roof and maybe had some effect when aerodynamics for caravan fronts had not been considered. However as a universal device the user had no idea where it should be fitted along the roof of specific vehicles for optimum performance. Presumably now that many towcars are SUVs and therefore taller the drag coeefficients are quite different to a saloon or hatchback, and also much higher to reach to affix anything temporarily while towing. Also as noted above caravans are no longer shaped like bricks! As I recall once the caravan was pitched owners would drive about during their stay with the thing still affixed, thus most likely negating benefits that might have been accrued while actually towing. I would have thought there should be research from lorry cabs that frequently have an extension heoght 'fin' to prevent drag from the front of the box shaped trailer of fixed body.
 
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May 7, 2012
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This looks to be a potentially useful idea. The fuel for our set up when towing is normally just under 30 mpg but a similar journey without the caravan would normally give me bout 45 mpg. In our case we are sing a saloon rather than an SUV or hatchback and my feeling is that the salon is the worst set up. With an SUV or hatchback there is less room between the end of the roof and the front of the caravan so probably less air is dropping down before hitting the front of the caravan.
We did originally have a roof mounted spoiler which worked to some extent with a hatch back and an old and more slab fronted caravan than you get now. When the car changed to a saloon and the caravan was updated to a more efficient front end the advantage seemed to be lost.
Looking at the diagram though the idea seems to be a device running from the back of the car roof up to the top of the caravan so should be far more efficient but I am not clear how this is mounted and could deal with sharp bends, could one end project from the side in these circumstances. Weight is also critical in caravan towing so it would have to be very light.
In theory it would certainly reduce the wind resistance and should produce a useful saving on fuel, but the cost would be critical. Given that there are probably hundreds of different cars and caravans, the difference between the height and the distance from the car roof to the front of the caravan will vary enormously. This would suggest that to produce this you would need several sizes and I do wonder if the production costs could be justified unless marketed on a global basis.
We tow on average about 3,000 miles a year which is possibly about average. The towing mileage would suggest I use about 100 gallons a year extra which amounts to about £600 so the cost is quite high and it is considerably more for many but even a 15% saving is only £90 - £100. Basically to make this idea attractive you would have to show the cost of the system could be recovered in probably three years and possibly it could be transferred if the outfit is changed. If the system is not easily transferred it may have limited attraction.
I am not trying to be negative, the item looks good on paper, but there are practical, weight and cost implications.
 
Feb 22, 2021
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Atif, how is this addition supposedly to be attached between the car and the Caravan / horse box. Does it cover the sides as well or just the top,
How does it effect the exhaust gasses from the towing vechile.
These are hopefully constructive comments and not meant to be destructive to your groups investigations.
I am looking at it as a caravanner and an Aircraft engineer.
That is a very valid question. The idea is to develop either with a flexible material that can roll like a window blind or with plastic or fibreglass. In case of rigid construction, the device will be fixed on the caravan and other end will be sliding on a fixture placed on the car roof. This will allow free manoeuvering. Regarding exhaust gases, this will not affect exhaust as the pressure behind the car is still negative.

Thanks
 

Damian

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Mar 14, 2005
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In case of rigid construction, the device will be fixed on the caravan
And how do you intend fixing to a caravan ?
You cannot use screws or bolts which leaves possibly some kind of adhesive, which when it comes time to upgrade the caravan , how do you remove ALL traces of such a fixture?
 
Mar 14, 2005
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We tow on average about 3,000 miles a year which is possibly about average.
Sorry Ray but that is not average, that is quite high. Not everyone who has a caravan is retired. However for you such a device if it did make a 10% fuel saving it might pay for itself over a couple of years.
 
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Mar 14, 2005
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Thanks Pr.Jl.
I was not expecting such a detailed and critically reviewed comments. I am happy to see your interest. In respond to your concerns, this idea is still in development phase and this is the main reason why I thought it would be a good idea to have other people's opinion. This has really broadened my way of thinking.
I have simulated few shapes which has shown more than 10% percent fuel saving. The next challenge is the safety and design cost of this product now. Whether people want to buy it. I will keep updated once I have answers of your questions.
Thanks
I hope I have indicated the market appeal of your system will very much depend on how much it costs, and thus what the pay back period might be for the purchaser. Obviously you want the largest percentage fuel saving you can get, and as I did suggest over exaggeration of savings was one of the downfalls of previous wind deflectors.

I'm intrigued to know the way you establish fuel saving figures. Is it only based on the reduced aero drag?
 
May 7, 2012
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Sorry Ray but that is not average, that is quite high. Not everyone who has a caravan is retired. However for you such a device if it did make a 10% fuel saving it might pay for itself over a couple of years.
Possibly this is higher than some, but you do get those doing more and many drive down to the South of France and further. If I am high then the savings could be less than my figure but many drive cars that guzzle more fuel than mine, so my figure is hopefully somewhere near average. I am not sure where you would find accurate figures though but price would be critical.
Not sure what we will do this year as early trips may not be possible, but if things go to plan our August adventure will exceed 900 towed miles on its own.
 
Mar 17, 2020
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Possibly this is higher than some, but you do get those doing more and many drive down to the South of France and further. If I am high then the savings could be less than my figure but many drive cars that guzzle more fuel than mine, so my figure is hopefully somewhere near average. I am not sure where you would find accurate figures though but price would be critical.
Not sure what we will do this year as early trips may not be possible, but if things go to plan our August adventure will exceed 900 towed miles on its own.
Like everything, and why so many of us add a disclaimer such as "we are all different! " to posts.

Had our usual European jaunt gone ahead in May 2020 towing was going to be approx. 1,500 miles. If we get away this September it will be around 1800 miles.

It would be interesting to read more about what we all do with our camping holidays. Might help to get a clearer idea of how each of us functions. Whether that would help in any way other than create "human interest" is a mute point of course!
 

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