Minimizing Aerodynamic Effect for Trailer Towing

[bluebunny]

OK, I did not give much support for the not recommended rooftop spoiler, so here is my reasonable speculation:
1. The trailer gap is very high, which significantly reduces (or eliminates) the benefits of a rooftop spoiler.
2. The temptation is to "go for lunch", etc with the truck while not towing, which can very quickly eat any gains.
3. It is a PITA to mount and unmount, and drags even if folded flat. Normal truck use will eat the life out of the gains while trailering.
4. with research, a proper stab at the canard fronts will outperform the rooftop spoiler.
5. With canards, maximize filling the gap, but watch out for maneuverability, so sides should be smaller than top, but need not be simply contoured.

[unheardofinstruments]

I had started a range extender/trailer build for my electric porsche 924 project and planned to make the trailer from a porsche 924 wreck for drag reduction as the back end is nice aero shaped and have a large sheet of lycra and planned on lacing it from the rear hatch window on the EV to the front of the trailer, it would be stretchy enough to allow the change of angle for cornering and be something like an articulated (bendy) bus with the concertina in the middle effect and look kind of limousine 924. I have a small generator I am building from a twin 50cc plane motor (4.6kW @ 4500rpm) and a PMDC wind turbine generator (11.2A @ 4000rpm and 130V) with peltier units on the exhaust for DC charging (using the engine as a source of heat mainly.) I wanted to sleep in the trailer while the car is charging on mains say at a caravan park in the middle of a long trip.

[aerohead]

Originally Posted by bluebunny

OK, I did not give much support for the not recommended rooftop spoiler, so here is my reasonable speculation:
1. The trailer gap is very high, which significantly reduces (or eliminates) the benefits of a rooftop spoiler.
2. The temptation is to "go for lunch", etc with the truck while not towing, which can very quickly eat any gains.
3. It is a PITA to mount and unmount, and drags even if folded flat. Normal truck use will eat the life out of the gains while trailering.
4. with research, a proper stab at the canard fronts will outperform the rooftop spoiler.
5. With canards, maximize filling the gap, but watch out for maneuverability, so sides should be smaller than top, but need not be simply contoured.

Here is an option,which actually made it into production in the UK way back when.
It's an inflatable nose which gives you the great crosswind bulbous advantage,plus killing a major portion of the gap.It's light and isn't in the way until 'under way.'
A 12-VDC blower does the inflation.

[aerohead]

Originally Posted by unheardofinstruments

I had started a range extender/trailer build for my electric porsche 924 project and planned to make the trailer from a porsche 924 wreck for drag reduction as the back end is nice aero shaped and have a large sheet of lycra and planned on lacing it from the rear hatch window on the EV to the front of the trailer, it would be stretchy enough to allow the change of angle for cornering and be something like an articulated (bendy) bus with the concertina in the middle effect and look kind of limousine 924. I have a small generator I am building from a twin 50cc plane motor (4.6kW @ 4500rpm) and a PMDC wind turbine generator (11.2A @ 4000rpm and 130V) with peltier units on the exhaust for DC charging (using the engine as a source of heat mainly.) I wanted to sleep in the trailer while the car is charging on mains say at a caravan park in the middle of a long trip.

I've seen some semi-enclosed recumbent bicycles with Lycra Spandex skins.It's pretty cool,design-wise.
I'm not certain what happens at elevated speed though,and if the fabric would deform aero-elastically.
I think that there's a thread around here about a guy that did the Lycra gap-filler with a VW Golf or Jetta/trailer project.

[bluebunny]

love the pressurized bag! What thinks the pressure would have to be?

( I want to post a "poor man's canard" which mimics a blown-slot airfoil high lift device for maybe some of you folks to test? a cheap and easy and robust design to build for a few dollars around a bluff body...)

[aerohead]

Originally Posted by bluebunny

love the pressurized bag! What thinks the pressure would have to be?

( I want to post a "poor man's canard" which mimics a blown-slot airfoil high lift device for maybe some of you folks to test? a cheap and easy and robust design to build for a few dollars around a bluff body...)

I used a VW Westfalia Campmobile electric heater booster fan for my boattail project.It worked perfectly.
Here's the bean bag chair-derived prototype

Here's the 'monster.'

I used Naughahyde/leatherette,but in the future it will be rip-stop nylon.

[bluebunny]

Originally Posted by bluebunny

Attachment 19296

try tacking these untested canards around the leading edge?

[Dave's Civic Duty]

I'm wanna check these all out, I'm always towing something!
Dave

[bluebunny]

Hi Dave,
These are rather small, so if you have a large trailer that really extends out in the air stream, Larger may be better. In any case, they will be subject to high loads; much higher than say a trunk wing. They must be sturdily constructed and securely mounted.

What are you towing behind what sized vehicle?

[bluebunny]

leading edge slots and slotted flaps are explained in this ancient film from the 30's. the canard slot follows the principle. starts 7:30 into the film...

https://www.youtube.com/watch?v=q_eMQvDoDWk