HPs x Wind drag

[schrederman]

And while we're looking at the frontal area, there is probably as much drag associated with the square backs of most trailers as there is frontal area drag. Have you noticed the big rigs with the air managers on the backs? With all the draggy stuff on our trailers, it would be a real trick to get an accurate number on the whole coefficient of drag... But with what's been calculated, we can get a rough idea.

[pdqparalegal1]

Originally Posted by ebcobra93

I pull a Roo 183 with a 2014 ford explorer sport (rated 365 HP, haven't looked at the torque curve). I'm at around 98-99% of GCWR when fully loaded. I've never felt under powered, but my mpg really suffers when driving over 65mph (<8 mpg). I'm sure alot of that is due to wind resistance.
I've thought about getting a wind deflector for my roof, but nothing I've read has convinced me that they make much of a difference.

Way too complicated!! Pull till it stalls! And then get a bigger truck!!

[harpplayer]

Don't know how much a wind deflector helps with mileage, since no two traveling conditions are the same, but if you travel where there are bugs, a wind deflector sure helps keep the front of the TT clean.

[RACarvalho]

Originally Posted by Iggy

You are way over thinking what you can tow in relation to wind drag.
You have a 2006 BMW X5 which has curb weight of 4,652 lbs and a Gross Vehicle weight of 6,008 lbs.
With a full tank of fuel and cargo you don't have much left.
Wind coefficient/drag has fractional effect on your pulling torque.

Maybe I just don't see your logic on why you would want to calculate just a minimal effect on towing. Enlighten me.

I'm not doing this to find out what I can tow... I already tow my trailer with the X5...

Being an engineer, I love, have fun and find entertainment trying to learn how stuff works and why.
I'm doing this because I got curious about how many horses in fact are needed to tow.
And yes, math is fun for me...

Last time we spent one week camping in Florida we were camping together with another family and the other guy was an engineer just like me....
Two crazy nut jobs calculating the solution for the world problems around the fire pit....

[RACarvalho]

Originally Posted by harpplayer

Don't know how much a wind deflector helps with mileage, since no two traveling conditions are the same, but if you travel where there are bugs, a wind deflector sure helps keep the front of the TT clean.

The wind deflector works on the "C" (Drag coefficient) of the equation trying to reduce it.
If you have a C of 0.85 and the deflector reduces it to 0.80, that's a 6.25% reduction in the power needed to push the rig through the wind.
If you we are talking 100hp as a baseline, you would be saving 6+ HPs to do the same work... In Theory saving that fuel....

[DaGrinch]

Originally Posted by RACarvalho

Tks for sharing.
If I remember CamAm test right, the longer trailer with a less vertical front had a 12% better fuel comsumprion than a small trailer with a flat wall... Looks like consistent with your experience.
I'm considering to do one for myself for I think the ones on the market are too low.
What material did you use for yours? Did you felt the deflector pushing the Jeep down further?

Tks,

It's going to take me a couple days, since I'm heading out this afternoon for a 3 day camp trip, but I'll send you a picture. I used 1' aluminum square stock and Lexan. My oldest son is a mechanical engineer and he helped set the angle. Total cost was about $75-$100 for materials and maybe a couple hours of my time.

[DaGrinch]

Originally Posted by RACarvalho

Tks for sharing.
If I remember CamAm test right, the longer trailer with a less vertical front had a 12% better fuel comsumprion than a small trailer with a flat wall... Looks like consistent with your experience.
I'm considering to do one for myself for I think the ones on the market are too low.
What material did you use for yours? Did you felt the deflector pushing the Jeep down further?

Tks,

It's going to take me a couple days, since I'm heading out this afternoon for a 3 day camp trip, but I'll send you a picture. I used 1" aluminum square stock and Lexan. My oldest son is a mechanical engineer and he helped set the angle. Total cost was about $75-$100 for materials and maybe a couple hours of my time.
As far as pushing the Jeep down.... no. I ran air bags with about 30# of pressure.

[Purdyquibb]

You guys are making my #amn brain hurt..... I must be wrong but I find the sweet spot my truck is happy with for that day, Wind resistance? pfffft. Either I feel it or I dont? Gas it! I just wanna go camping!!! lol. Now wheres that excedrin????

[WolfWhistle]

I would recommend a site called emodders. Real experts there. Maybe
someone there can help.
Many discussions you will find about deflectors, etc (days weeks and months of reading)

WW