Aerodynamics

[campigloo]

Ok, before you start this seems a bit off the wall to me too. I have been reading about mods to trucks involving sealing off the bottom side to improve air flow. Seems like a lot of work to me. But I have somewhat seriously considered mounting a wind deflector(got a better name?) behind the wheel wells and in front of the tailgate. I have an Outback and the front is somewhat rounded, but I have a bug line about half way up. Think it's worth it?
Also was looking at some wind tunnel tests and see a vacuum behind the trailer. Would an air scoop under the trailer pointed up from the bumper help?
Try not to laugh too hard. Don't want any split ribs out there!

[profdant139]

OK, free radical -- dimples are no problem. One good hailstorm, and your mpg jumps 11% 😉

[free_radical]

Interesting topic,
easiest way to improve mileage would be to get streamlined trailer in the first place,such as Airstream or Casita,Scamp,, 😉
now if someone made camper with a surface dimpled like a golf ball you might get even better improvement in mpg,IF we are to believe it,Mythbusters claim 11% better
:h
http://youtu.be/eR5SlwNf4K0

[Gdetrailer]

campigloo wrote:
Thanks Francesca, that is the one I was looking at. Another had a scoop on the bottom of the trailer pushing air into the vacuum. Some 1/4" plywood and fiberglass resin? The bugs are not the problem, just an indication of where the air hits the trailer.

Altern, can I send you an ace bandage? LOL

It will take something more substantial in strength than 1/4 plywood and fiberglass resin to survive the wind and air pressure your devices are going to be exposed to (screws at high speeds would simply pull right through the plywood and then you will have some expensive repairs). Especially if you are driving 70 MPH and have wind gusts of 20 MPH or more.

You basically need to construct it as if it was going to be exposed to HURRICANE wind speeds. There IS reasons as to why those commercial built truck deflectors cost so much..

One sheet of 1/4" plywood will add nearly 38 lbs to your weight to boot and adding fiberglass and resin will add a few more lbs per sheet...

You almost would need to built a lightweight aluminum tubing frame then skin it with FRP (Fiberglass Reinforced Panels). This will cost you much more than $100 and the net savings in fuel mileage most likely will be far less than if you slowed down (which is FREE). Aluminum and FRP are very lightweight materials but do cost more than say plywood...

[hone_eagle]

Don't forget the roofs of our rev's are very cluttered they also need to smoothed out. My opinion ? useless unless you travel commercial miles and not worth it,but a interesting discussion .
I have found that thinking of mileage as a 'cost per mile' rather then MPG is more accurate ,a big tank(s) allows you to fill at lower cost places/states.
Or subtract what you would spend anyway if you were driving to work everyday of vacation instead , and hopefully it will be a wash.

[Gjac]

Working for an aircraft company for 30 years I have built and witnessed a few wind tunnel trials and in later years computer simulations. It is not hard to visualize the turbulence coming off the back of a MH. When I went to Alaska I built a shield that went from underneath the MH to the tow car out of old trampoline material to keep the stones from damaging the tow car. Similar to a protect-a- tow. I always wondered what the difference in mpg would be if the material went from the top and sides of the MH to the back bumper of the car creating a trailing edge to lessen the turbulence and protect the whole car at the same time. It would be interesting if anyone had any information and could relate what a 25% reduction in wind turbulence would have on mpgs.

[Francesca_Knowl]

profdant139 wrote:
I guess what they say about economists might also be true of aerodynamicists -- if you took all of their opinions and laid them end to end, you'd never reach a conclusion!

Bet the aerodynamicists would get close faster unless you tied 'em down real good, though.

Thanks for the new-to-me word, by the way...I like it! 😉

[profdant139]

Ichabod, I have seen those discussions, and I guess what they say about economists might also be true of aerodynamicists -- if you took all of their opinions and laid them end to end, you'd never reach a conclusion!

If anyone knows for sure whether those airtabs really make financial sense (or don't), I would love to see some hard data. It could be like those underbelly skirts on freight trailers -- they make sense if you drive a quarter million miles a year.

[IAMICHABOD]

Here is all there is to know about Air Tabs Just click around.

Air Tabs

Also a few threads on the subject.

HERE

And HERE

[profdant139]

They sell those airtab things -- little triangles on the back edge of the RV -- and some truckers use them. But I do not know if there is a controlled study to show that the mpg justifies the expense. Some folks who use them swear that they get a more stable ride and less dirt on the back.

[campigloo]

Neat little history lesson!

[Tin_Pusher]

And well received it was, too 🙂

[Lynnmor]

Tin Pusher wrote:
Keeping in mind that 78 yrs ago, aerodymanics was a lot more styling than science 🙂

Here is a little history lesson from the same time period:

Science?

:R

[Tin_Pusher]

Keeping in mind that 78 yrs ago, aerodymanics was a lot more styling than science 🙂

[Lynnmor]

PawPaw_n_Gram wrote:
My prediction is that in 20 years - trailers and MH will look quite different because of trucker developed aerodynamic lessons.

I predict that in 20 years we will be even dummer. Here is where we were 78 years ago: