Camper trailer aerodynamics and engine cooling

[dandfx]

Hey F1 Technical,
I have an order in on a camper trailer in which we'll tow fairly log distances, we have a 3000km month planned. I picked this model because it's somewhat low profile for the size which will improve the towing characteristics (compared to a full size caravan).

Being a frequent reader of the hardware dev section it had me thinking about aerodynamics of my setup and if a canopy fitted to the ute (pickup) tray would help or hinder the aerodynamic drag effects. I've edited some images of a similar vehicle with the same trailer. One with a standard ute / pickup tray (assume flat top, not open) and a full canopy setup flush with the vehicle roof.

My question is, which will be more efficient for towing and how much impact would it have? With a canopy installed I assume will be less disturbance of airflow but I have heard in drag racing the low pressure area in the tray actually improves efficiency. I'm no aero analysis expert so I'm leaving it open to discussion here.

Also, separate similar question. Aftermarket bull bars significantly reduce air intake for the intercooler, radiator and transmission cooler. I'm looking to maximise airflow with some horizontal and vertical ducting to ensure the air flows through the radiator etc and prevent it bleeding around inside the bumper bar. Would having a grill between the headlights increase the speed of the air? Would a lower interference or no grill allow more flow or slow the air and reduce speed? See lower and second pictures - factory left, aftermarket right (I don't have spotlights).

Thanks!

[Greg Locock]

I suspect the full canopy is a better option. No opinion on cooling. Incidentally I tow a Cub camper, which is probably half the frontal area, behind an Everest, and the difference in fuel consumption is not significant. It does only weigh 850 kg.

[dandfx]

Thanks for the reply, I'm expecting canopy will be better, I'm interested to hear how much difference it would make.

I had a forward fold until recently, it sat level with my tray so really no issue towing. The Cub campers look well made, checked them out at a show on the weekend.

[jjn9128]

It depends how well the trailer fills the wake of the truck. I wouldn't take it as a given the canopy will be a benefit. I guess it also depends how full the deck is. The canopy with a spoiler or upper lip extension might be a benefit to cut the lift and downwash onto the trailer. But that's something I'd want to study to before saying anything definitive I couldn't tell you how much of a difference either option would make to fuel cost over a 3000km trip.

If this is the truck without the bull bars they significantly blocked the cooling. You don't want high speed into the rad but you want mass flow - that's why they're placed adjacent to the stagnation point. I'd imagine the bull bar manufacturers would suggest something?!

[Big Tea]

I used to tow a large-ish trailer with a car and found a wind deflector fitted to the car roof helped a great deal.
Cant find a pic of the one I preferred, probably no longer made, but this forum may interest you

https://forums.practicalcaravan.com/thr ... ors.55048/

Not the same as you were asking, but may be worth a scan

[SiLo]

I could totally get behind some CFD for this. I just need to learn CAD first...

[dandfx]

...If this is the truck without the bull bars they significantly blocked the cooling. You don't want high speed into the rad but you want mass flow - that's why they're placed adjacent to the stagnation point. I'd imagine the bull bar manufacturers would suggest something?!

Thanks, stagnation point is a term I wasn't familiar with, it's going to be hard to assess that so I'll probably go trial and error. I have a OBD2 reader which gives accurate temperature readouts that will assist with anecdotal experiments.

I used to tow a large-ish trailer with a car and found a wind deflector fitted to the car roof helped a great deal.
Cant find a pic of the one I preferred, probably no longer made, but this forum may interest you

https://forums.practicalcaravan.com/thr ... ors.55048/

Not the same as you were asking, but may be worth a scan

Looks like it's easier to add drag than it is reduce it with those deflectors. I think canopy fitted or tray back with flat cover will be as far as I'll go.

I could totally get behind some CFD for this. I just need to learn CAD first...

My thought too, it would be really interesting to see what CFD would show but it's a lot of effort that theory can probably give a reasonable concept.