# Renovation and aerodynamic improvement of a BPW closed trailer

Present your DIY projects, your new technical ideas, your innovations to test or your self-construction work. Because doing it yourself is often more economical and can be more efficient.
Christophe
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## Re: Renovation and aerodynamic improvement of a BPW closed trailer

I finished the comparative study, I give you the results of the drag force at 130 km/h, the overpower consumed, the Cx... but you don't deserve them because you were naughty... so I keep this topic locked.

Cubic Trailer:

Cx = 0,978
Drag force at 130 km/h = 1624 N
Power boost required at 130 km/h = 79,2 hp

Front area: 1,96 m²

Resumé_cubique.png (134.06 KiB) Viewed 1334 times

Semi-optimized trailer (without the Beluga):

Cx = 0,462
Drag force at 130 km/h = 767 N
Power boost required at 130 km/h = 37,5 hp

Front area: 1,96 m²

Resumé_semi.png (118.48 KiB) Viewed 1334 times

Actual trailer as I built it:

Cx = 0,438
Drag force at 130 km/h = 720 N
Power boost required at 130 km/h = 35 hp

Front area: 2,2 m²

Resumé_réelle.png (122.32 KiB) Viewed 1334 times

Fictitious real trailer (first idea but unrealizable for regulatory reasons) with rear fishtail:

Cx = 0,387
Drag force at 130 km/h = 632 N
Power boost required at 130 km/h = 30,9 hp

Front area: 2,2 m²

résumé_queue_de_poisson.png (216.74 KiB) Viewed 1334 times

These results do not take into account the towing vehicle (without comment), the underbody or the wheels, assuming that this is the same for all models.

The reality will therefore be a little worse, but the comparative orders of magnitude are there.

Conclusion: by manufacturing and using trailers designed by aerodynamic nags, we consume more than twice as much at 2 km/h and we often cannot even reach 130 km/h!!
3 x
Christophe
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## Re: Renovation and aerodynamic improvement of a BPW closed trailer

Here is the almost final shape of the trailer:

trailer_forme_finale.jpg (458.78 KiB) Viewed 1254 times

I remember where I come from:

3 x
Obamot
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## Re: Renovation and aerodynamic improvement of a BPW closed trailer

First of all, it's a very nice result on very good technical “intuitions”. Simulations do it

Although the original trailer was still “Shimano”?...

I prefer the transformed where there's no more need to shit in the hands
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“Evil” carries within itself its own condemnation”
Christophe
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posts: 79707
Registration: 10/02/03, 14:06
Location: Greenhouse planet
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## Re: Renovation and aerodynamic improvement of a BPW closed trailer

I also simulated the profile of Eiffel (1/2 drop of water) with a max projected frontal surface of 2 m²... (not estimated the interior volume but it's close to the others)

I get at 130 km/h:
27,5 kg of drag
13,4 hp...
and a Cd of 0,162...

On the visualization, no eddies, no depression, no boundary layer separation...

No trailer will do better than that...however, it's very hard to achieve as a shape, apart from a large mould, I don't see...
3 x
Obamot
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## Re: Renovation and aerodynamic improvement of a BPW closed trailer

If yes, why? Make it fiberglass? Still needed a mold (and now it exists)
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“Evil” carries within itself its own condemnation”
Macro
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Registration: 04/12/08, 14:34
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## Re: Renovation and aerodynamic improvement of a BPW closed trailer

I would have to check if my Czéro which has almost the profile of Eiffel but reversed with respect to the direction of travel ... consumes less in reverse than in forward ....
citroen-c-zero-2017-ausen-seite-dynamisch.jpg (85.19 KiB) Viewed 1134 times

But good with my cervical hernia it will be complicated
1 x
Christophe
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## Re: Renovation and aerodynamic improvement of a BPW closed trailer

Macro the answer is most likely yes...remember to remove the wipers all the same

Reverse gear is limited in km/h on EVs, by the way?

ps: don't ask me why these (cons of) engineers from Citroën have reversed the direction of advancement! No doubt for their career advancements...
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Macro
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## Re: Renovation and aerodynamic improvement of a BPW closed trailer

Yes the speed is limited in reverse ... The engineers who designed it ... Are not those of lemon but those of mitsubishi. Japanese product designed to pay a minimum of taxes in Japanese cities minimum surface area for 4 passengers... Originally in Japan, it's a thermal...
1 x
Christophe
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posts: 79707
Registration: 10/02/03, 14:06
Location: Greenhouse planet
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## Re: Renovation and aerodynamic improvement of a BPW closed trailer

It doesn't matter, it's the same!

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Macro
Econologue expert
posts: 6776
Registration: 04/12/08, 14:34
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## Re: Renovation and aerodynamic improvement of a BPW closed trailer

They are capable of worse... 1t7 90cv v max 145kmh
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