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Old 03-15-2014, 01:12 AM   #71 (permalink)
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So I came across another factory trailer that looked promising until I looked at some owners forums. Seems like this teardrop design is actually worse then just pulling a box! Many v6 owners can hardly break 10 mpg at what would seem a reasonable 55mph. About the best anyone seems to get regardless of the tow vehicle is 14 mpg.

It seems after a few years of making this the company added a small spoiler above the back window that does seem to help 1-2 mpg. I'm sure that rooftop ac doesn't help either, they should use a wall mount.
I actually feel sorry for the owners who bought this thinking it would do fairly well, I know before I found this forum I would have thought the same.
So is it actually worse then a square back? Could it be fixed with a bigger spoiler?

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Old 03-15-2014, 02:40 AM   #72 (permalink)
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The problem with this design is that a serious downdraft and consequent very low pressure area is created above the rear window and high presure air is moving along the side. So you have air moving in 2 directions and 2 differing pressures.

Can you say VORTEX? The drag created by spinning the the air dragging along 2 tornadoes is immense.




There is a slightly more efficient shape for creating drag, but not by much.

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Old 03-15-2014, 03:08 AM   #73 (permalink)
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The above is not a true teardrop trailer, it is called a "standy" since you are able to stand up.

Here is the classic shape....

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Old 03-15-2014, 10:29 AM   #74 (permalink)
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I realize it's not a classic teardrop but then I wonder if the classic teardrop is also doing the same thing just on a smaller scale.
I mean the 18' rpod with a slide is only 2500#, people with a 18' 2500# classic box travel trailer get better then 10 with a modern v6 tow vehicle.
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Old 03-15-2014, 11:36 AM   #75 (permalink)
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Quote:
Originally Posted by Hersbird View Post
I realize it's not a classic teardrop but then I wonder if the classic teardrop is also doing the same thing just on a smaller scale.
I mean the 18' rpod with a slide is only 2500#, people with a 18' 2500# classic box travel trailer get better then 10 with a modern v6 tow vehicle.
Until you see a true study with the same vehicle pulling each trailer over the same course, I would not put much weight in those numbers.
It is very easy to do, hopefully someone will step up and do it.
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Old 03-15-2014, 03:45 PM   #76 (permalink)
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Originally Posted by freebeard View Post
http://ecomodder.com/forum/showthrea...tml#post294074

Do you use the Insert Link button? How does it fail? The biggest pitfall is when it appends rather than overwriting the h**p:// as in:

Just trying to help.
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Old 03-15-2014, 04:13 PM   #77 (permalink)
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same thing

Quote:
Originally Posted by Hersbird View Post
I realize it's not a classic teardrop but then I wonder if the classic teardrop is also doing the same thing just on a smaller scale.
I mean the 18' rpod with a slide is only 2500#, people with a 18' 2500# classic box travel trailer get better then 10 with a modern v6 tow vehicle.
The FKFS (Koenig-Fachsenfeld/Kamm) tested something similar to the r-pod,except that it had inboard wheels.It was reported at Cd 0.45.
The r-pod,with exposed wheels and fenders would be higher.
The 'classic' teardrops would suffer the same attached longitudinal vortices as r-pod just as ChazInMT has illustrated above.
The rooflines are all too fast,the pressure builds over the aft roofline in advance of the side flow,we get separation up there,and the pressure differential causes higher pressure air from below and on the sides to race up there attempting to reach equilibrium.As the flow fields collide at different velocity and pressure,they coil up just like a mesocyclone,spinning into horizontal tornadoes.
The sharp edges rob about 16% of Cd potential.The gap sucks energy.If they don't have belly pans,there's some more loss.
A 'gutted' VW microbus 'trailer' would pull as well as a shrunken Airstream,at Cd 0.43 (free-air),lower in train behind a tow vehicle.It would have more usable interior volume than a 'teardrop.'
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Old 03-15-2014, 04:42 PM   #78 (permalink)
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The gutted microbus is a neat idea but how about this; microbusses are expensive how about a gutted minivan? Maybe even turn it backwards. I think they would need to be put on a diet although removing all the drivetrain, dash, stearing, and using a simple straight axle would help.
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Old 03-15-2014, 05:06 PM   #79 (permalink)
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minivan

Quote:
Originally Posted by Hersbird View Post
The gutted microbus is a neat idea but how about this; microbusses are expensive how about a gutted minivan? Maybe even turn it backwards. I think they would need to be put on a diet although removing all the drivetrain, dash, stearing, and using a simple straight axle would help.
You'd want to size it's frontal area to match as close as you could to the tow vehicle.
The Pontiac Trans Sport is of the lowest Cd sold,0.30.I still see a few driving,and many out of service.It's drag,backwards,would be an unknown quantity.
'Steering' backwards would have to be addressed,as it would not behave as with a traditional tow-bar setup.
A diet would be good.
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Old 03-15-2014, 06:22 PM   #80 (permalink)
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The transport is what came to mind, the axle would have to be moved to about the front door area, the current front and rear wheel areas just filled. You could even hide the new wheels behind the doors but leave them functional so if you had a flat you could still access it just by opening the door.

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