long caravan sail area

[terry_374356161]

Surely with caravans getting ever longer and heavier the effect of the sail area of such a large caravan should be accounted for in some way. Is there some scientific way, like the 85% rule that could aid caravanners to get a safe setup? You know, above a certain length then, perhaps 80% then for a vey long caravan 70% taking into account the tiny engine and low towing margins of smaller cars? It needs an experienced person to get the ball rolling on this front.

Where extra long caravans being towed by tiny cars would have to take into account the huge sail area and the deadly effect of side winds.

just a thought.

terry

 

[Lutz]

To some extent, the 85% recommendation already takes the sail area into account. For trailers with a small sail area, like horse boxes for example, the 85% don't apply and it is quite common to make full use of the towing vehicle's limit, as specified by the car manufacturer. Once you get to the size of the average caravan, however, there are so many other additional factors which affect stability that sail area really doesn't really make more difference in proportion to any of the other factors. If you were going to make a recommendation based on sail size, you would also have to make a recommendation for load distribution, drawbar length, wheel load difference from side to side, just to name a few. Besides, it is not only pure size which affects crosswind behaviour but also the location of the aerodynamic centre of the caravan in relation to the axle position.

 

[Angus1]

A sensible suggestion, although remember there isn`t an 85% `rule`.

There are potentially too many variables which can alter the towing stability, for the car you would have length, wheelbase, overhang, aerodynamics, track, centre of gravity etc, before you even started on the van.

I don`t regard 85% as a `safe` figure, but I suppose you have to start somewhere with some form of guidance however abstract it may seem.

Obviously, a short caravan being towed by a car with a short overhang, long wheelbase, stiff suspension and wide track should be more stable than a long caravan behind a short-wheelbase, narrow tracked softly sprung car. Unfortunately, I don`t think a usable formula which had any basis in fact could be cobbled together, but your idea certainly has a lot of merit.

 

[terry_374356161]

blimey. thats a lot to think about.

it's possible that there are too many variables when each case would be unique.

thanks guys

terry

 

[Lutz]

Exactly, that was my point, too.