Foamie aerodynamics.

L, aerodynamics is really everything ... The air is essentially a liquid and you can feel the effects just by sticking your hand out the window while driving ... the faster you go , the More drag you feel on the same area... Now multiply that times the frontal profile of your trailer .. :eek: Smoothing out the shape to better help the wind flow smoothly over the surfaces , really helps ... as you can see with modern fuel efficient cars which look like bullets ... Think about what airliners look like ... that’s a pretty optimum shape ... ;) No reason a trailer can’t be similarly streamline (think Airstream) , especially easy with a Foamie ... :thinking:
 
Lots of little ways to reduce Drag ... and little things add up ... But the easiest way to reduce Drag is to just slow down ... :eek: True !!! Drag seems to increase exponentially with Speed ... Drag in water is just ridiculous ... nearly impossible to lessen ... Only way to reduce Drag on a boat is to get as much of it as possible OUT of the water ... :shock:

Actually the teardrop shape everybody loves in really not bad , we just need to find a better way to keep the flow attached off the back of the trailer which falls off a bit too sharply ... I’ve got some ideas from flying and designing planes all these years , but they would alter the basic TD shape considerably ... especially in the rear ...

Just for S&G, the basic TD shape stretched out would be even Better ... With TDs right now the flow detaches just about where the galley hatch starts... forming turbulence (low pressure) behind it ... the idea is to keep the flow of air attached till it just falls off the end of the trailer smoothly ... slipping through the air ... creating as little turbulence as possible ...

We might pay better attention to the undercarriage which as we’ve read, accounts for 40% of the overall trailer drag ... :eek: :shock: Air dams or smoothing the underneath would help , then some wheel pants ... all gets pretty complicated ... :NC
 
Anyone SERIOUSLY interested in the airflow over their trailers , can just tape tufts of yarn all across the top and sides , affix a small camera to the roof and drive down the road videoing the action of the tufts at various speeds ... easy to see where the tufts lay down smoothly and where they flap about wildly in the turbulence , and where it starts ... Great way of testing , no myths ... Here’s a video of a plane airfoil being tested like this , one which keeps the flow attached across the whole wing ...(possibly an idea for a trailer ? 🤔 ) http://www.youtube.com/watch?feature=pl ... RZBjUHoq7A Turn your speaker down , it does get irritatingly noisy , the whine of the motor and prop ... :eek:
 
Here’s a pic depicting what happens when the trailing edge starts to fall off rapidly , like a sphere ... sorta’ ... AND we may NOT want to make them Smooth ... :eek: http://www.aerospaceweb.org/question/ae ... 0215.shtml

image_page.php


Hey Eagle , what’s up with the loading picture
 
image.php


you have to add the img tags manually when loading from the albums. i'll do it for ya.
 
INteresting thanks GPW.
drag-shapes.jpg

Notice the #27 cupped hand shape is the worste for aerodynamics, as one would expect.


Read the full article and links. :thinking:
 
L’ , boxy trailer’s Not much better eh ?? ... Looks like the clear winner is #2 with the squared off back ... :thumbsup:
 
Don't forget - almost none of this general information is terribly relevant to teardrops since:
a) none of those examples are vehicles travelling near the ground, and
b) none of those examples have a tow vehicle in front of them.
 
All is not Lost ! It would appear that streamlining would help Any trailer ... Gotta’ be better than just a box back there huh ??? We’ll never get absolutely Clean surfaces anyway ... so lessening any extra Drag sure would help ... a bit ... all that adds up to extra mileage ... so why not ? Besides it looks Cool !! 8)
 
Aero is relevant no matter if towed or not as if it didn't matter then you shouldn't lose any gas mileage towing your foamy but oh you do lose mileage and as these docs and pics have shown almost all to wind drag. Round up front edges and try and keep it within the tow vehicles profile as much as possible are your biggest gains for aero efficiency.
 
Steve, I’m thinking shorter is much better too for less drag ... something even with the TV ... my Jayco is ~ 10’tall... sticks up waaay above the old pickup /camper top ... tows like a Parachute ... Serious !!! :frightened: I can really tell the difference (@ gas pump) , even worse at higher speeds ... :eek: My 12’ TD towed so easily , for a while I forgot it was there... :eek: Found myself barreling down the Hwy doing 70 , towing the new trailer ... What an Idiot!!! :oops: I’ll have to watch myself with the Foamie trailer which weighs relatively nothing in trailer terms (<500lb.) For my test tow down my bumpy (off Road Challenge) dirt road , the only thing I noticed was the rattling of the HF trailer ... the pinned folding bits.. might need to just Bolt those all solid ... Noisy on the washboards ... :eek: The truck responded like there was nothing there .... confirming the ability to easily carry the recommended 500# Ballast ... :beer:
 
Actually I believe height is the worse culprit as I've built 2 of them now almost identical weight and one 5'6" high and other 6' high and the extra 6" uses more gas to tow as they both have the same width at 6' wide so it has to be the height killing me. I tow behind an 01 supercrew 4dr f150 so I think if one stays within the vehicle width and around their tow vehicle height is the best they can hope for plus keep the weight as low as possible. I'm going to build my next one trying to hit below the 5'6" and see how that works out plus lighter than the previous 2.
 
if the golf ball dimples work so well maybe on the next foamy a few whacks with a ball-peen hammer would be in order. :)

prem has some chicken foot looking things on his cargo trailer that break up the air flow and he says gives him better gas mileage.

"As a result, the boundary layer resists the adverse pressure gradient much longer before it separates from the surface"
makes sense to me.
 
Steve, I believe you may just have established an optimal size ... All makes Good sense really ! :thinking:
Problem is all my trailers sit pretty high to begin with , so inside a 4’ is about as much cabin height as I can go and not be much over the truck (like my toy Foamie ) ... May have to try reversing the springs , with such little weight on them they may not bottom out ... but at a gain of only a few inches .. What’s the minimum height a trailer can be off the ground ??? (safely) See some folks use torsion axles which seem to be a bit lower .... no experience with those ... ?

Pete ... Hammer :frightened: Longer the flow stays attached , less drag it produces in the turbulent layer which is smaller ... http://en.wikipedia.org/wiki/Wingtip_vortices
 
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