Drag ?

[Impulse24]

I thought of putting this in the DIY section but thought it belonged here as it is a 5th wheel question.

There has been many topics of does a wing benefit towing, and when everything is take into account there is still those who reject the idea and those who accept it with glee. Yet tires and driving style can either destroy or increase MPG plus every picture of a wing shows it is too far forward in relation ship to the front cap of the 5th wheel to give any benefit.
There are also discussions on tail gates down or tailgates up, should it be left off or use a louvered tailgate? I guess security of what you carry in the bed also comes into the scenario.

But overall drag is rarely questioned, So here is a problem I can't seem to get answered and would appreciate a little help with.

Question,

I have a sliding bed cover, If I slide it over the front half of the truck bed (in front of hitch)when towing a 5th wheel with the tailgate up ! And rear of the truck bed behind the pin is left open, is more drag created? Is it the same amount of Drag as a full open bed? Or is there less drag?

Thanks.

[Old-Biscuit]

Know of a place where you can do some uninterrupted, non-public testing.....like an abandoned air field, long lonely stretch of unused roadway etc.

Hook up 5th wheel..open bed, OEM tailgate
Get up to 70 mph then place truck in neutral and let it coast to a stop....time/measure distance

Repeat with open tailgate
Repeat with louvered tailgate
Repeat with tonneau cover partial closed
Repeat with windows open


Oh never mind. Go camping and don't make RVng so complicated.

[Impulse24]

Prior to buying a MH I asked a round about many things, including fuel consumption, the favorite response was from people like you who always replied "If you have to ask, you can't afford it " Yet those same people complain about a 15 cent nut and bolt. If you don't know what your average MPG is you have no idea if you have a problem developing, which can add up to a few thousand dollars in repairs.
Besides A good Driver works out MPG with pen and paper, as they do other costs, only and idiots drives around unaware of expenses. I'm sure you could learn a few economic solutions if you were to go grocery shopping with your other half !!!
And if you have money to throw away then I suggest you pick a worthwhile charity and make a monthly contribution.

[IBcarguy]

How would you ever know? Wind tunnel test? I'm no authority on this topic but I think it would be negligible and maybe not even measurable. I guess you could try checking mpg with it open compared to closed. There are a lot of other things that would impact MPG rather than your sliding bed cover.
The wing, however might help especially if your 5th wheel cap is rather flat. Mine is very rounded and curved and I doubt if a wing would reduce wind resistance very much.
I think slowing down to 55mph would have the greatest impact on fuel consumption.

[rjstractor]

Only way to find out for sure would be wind tunnel testing.

[Bipeflier]

You either need a wind tunnel or a very accurate way of determining the horse power you are using.

Neither one is very practical. So really, who cares? If you are worried about 25 cents worth of fuel one way or the other, just stay home.

Camping (RVing) is for fun. Cost (within reason) is secondary.

YMMV

[fj12ryder]

That's an easy one. Nobody knows. Period. Full stop.