What difference if any does the shape of the front of the trailer make? Primarily on gas mileage and drag on your tow vehicle. How much does it help to have a pointed front and/or a dropped nose? Thanks. . .
Sent from my iPhone using Tapatalk
_+1 0n slowing down if we are going to live in these things and carry our toys they are never going to be anywhere near aerodynamic.You can study physics till your blue in the face but your still going to get 12 mpg if your luckytroubleScottie wrote:It is a bit difficult to determine without a wind tunnel eg practical test.
The drag (a force resisting your motion) is
Fd = Cd * (1/2) * ρ * V**2 * A
where V is the velocity, A is cross sectional area, ρ is the density of the fluid, and Cd is the drag coefficient of the object.
The biggest issue is cross sectional area. The bigger the area, the more drag. To a large extend, the cross sectional area is the combination of the towing vehicle (TV) and the trailer. All things being equal, if the trailer is completely blocked by the TV, it presents no additional drag. If it is bigger, it is adding drag. Think Formula 1 race car versus an SUV/mini van. Bigger cross sectional area is more drag for any particular shape.
The next issue is the drag coefficient (Cd) of objects that your are hauling or ability of fluid to flow around an object. The lower the number, the better. A cube is worst ( Cd = 1). A round nose is better (Cd=0.5) A wing is optimal Cd=0.04; a half wing ( Cd=0.09). How much is saved by rounding the edges of a box can be debated. Again, Formula 1 - almost a wing versus a mini van - almost a cube. To a large extent this is also a combination of the TV and the trailer. Granted we are asking about how much more drag will be added by the trailer.
Another issue is drag due to turbulence. This would have to be the effects of the air flowing over and behind the TV; into/out of the tongue area; flow on to the front of the trailer from the TV; and flow under the vehicles which will create more drag, raise your Cd. Ideally, you want your TV and trailer to be one solid object, so air does not flow between the two vehicles.This is why semis have various panels to redirect/smooth the air flow. I have seen that these panel can reduce the effective Cd by half. I have no idea how one determines these numbers for a TV and trailer without a wind tunnel test or a computer modelling system or trial and error. It is possible that these loses could wipe out all other gains. In the extreme -- image a really long tongue length, your TV and trailer will behave like two separate vehicles, greatly increasing your drag. I have seen some attempts to add screening to smooth the flow from TV to trailer -- could not say that that works or helps.
Finally, there is the drag due to the end of your trailer. A flat boxy back increases your drag the most. A 30 degree slope can reduce this drag significantly. You see this best when following vehicles in the rain, the amount of spray as you pass. You can see a big difference with the semis with those tail panels.
A nice simple example at https://docs.lib.purdue.edu/cgi/viewcon ... xt=polytec
In case no one noticed, velocity increases the drag. Slowing down can greatly reduce your drag.
Hit-n-Miss wrote:So not really a lot of difference?
troubleScottie wrote:It is a bit difficult to determine without a wind tunnel eg practical test.
The drag (a force resisting your motion) is
Fd = Cd * (1/2) * ρ * V**2 * A
where V is the velocity, A is cross sectional area, ρ is the density of the fluid, and Cd is the drag coefficient of the object.
The biggest issue is cross sectional area. The bigger the area, the more drag. To a large extend, the cross sectional area is the combination of the towing vehicle (TV) and the trailer. All things being equal, if the trailer is completely blocked by the TV, it presents no additional drag. If it is bigger, it is adding drag. Think Formula 1 race car versus an SUV/mini van. Bigger cross sectional area is more drag for any particular shape.
The next issue is the drag coefficient (Cd) of objects that your are hauling or ability of fluid to flow around an object. The lower the number, the better. A cube is worst ( Cd = 1). A round nose is better (Cd=0.5) A wing is optimal Cd=0.04; a half wing ( Cd=0.09). How much is saved by rounding the edges of a box can be debated. Again, Formula 1 - almost a wing versus a mini van - almost a cube. To a large extent this is also a combination of the TV and the trailer. Granted we are asking about how much more drag will be added by the trailer.
Another issue is drag due to turbulence. This would have to be the effects of the air flowing over and behind the TV; into/out of the tongue area; flow on to the front of the trailer from the TV; and flow under the vehicles which will create more drag, raise your Cd. Ideally, you want your TV and trailer to be one solid object, so air does not flow between the two vehicles.This is why semis have various panels to redirect/smooth the air flow. I have seen that these panel can reduce the effective Cd by half. I have no idea how one determines these numbers for a TV and trailer without a wind tunnel test or a computer modelling system or trial and error. It is possible that these loses could wipe out all other gains. In the extreme -- image a really long tongue length, your TV and trailer will behave like two separate vehicles, greatly increasing your drag. I have seen some attempts to add screening to smooth the flow from TV to trailer -- could not say that that works or helps.
Finally, there is the drag due to the end of your trailer. A flat boxy back increases your drag the most. A 30 degree slope can reduce this drag significantly. You see this best when following vehicles in the rain, the amount of spray as you pass. You can see a big difference with the semis with those tail panels.
A nice simple example at https://docs.lib.purdue.edu/cgi/viewcon ... techsummit
In case no one noticed, velocity increases the drag. Slowing down can greatly reduce your drag.
Return to Cargo Trailer Conversions
Users browsing this forum: No registered users and 13 guests