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Old 08-15-2011, 01:37 PM   #171 (permalink)
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Can I do the underside same way. Make correct size and Flip the template over and put it on the same place as roof side template. Or do I have to use the lower half of the template to underside of the boattail also?

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Old 08-15-2011, 02:36 PM   #172 (permalink)
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https://www.facebook.com/media/set/?set=a.260828010597758.84063.163711023642791&saved #!/photo.php?fbid=270254349655124&set=a.2608280105977 58.84063.163711023642791&type=1&theater

Can I do the underside same way. Make correct size and Flip the template over and put it on the same place as roof side template. Or do I have to use the lower half of the template to underside of the boattail also?
Diffusers (what is done on the bottom side of the car) are another topic. Typically, you will see people say 3-4 degrees which is optimal for drag reduction, however, even up to at least 11 degrees, you continue to be better off than not having a diffuser, at least according to Hucho. I am guessing that what you show is fine. If you want to see a car that looks a lot like the template, look into the Dolphine (sp?), if you want to see one that looks more like your drawing, look into the AeroCivic. Both work, both have reasons for their design.
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Old 08-15-2011, 03:20 PM   #173 (permalink)
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Originally Posted by Bicycle Bob View Post
A little knowledge is a dangerous thing, and this template is the least amount of information that can make people feel wise about airflow when they are not. I suspect that this thread does more harm than good.
You’re absolutely right, and let me give you an example. With no formal training in aerodynamics I just embarked on a very ambitious project, inspired to a large degree by the other ‘unwise’ people on this web site who have done amazing things with little or no formal training in this area. I took a rather large class C motor home which used to average 12 to 13 miles to the gallon on a good day, and by adding a boat tail, showed an improvement of about 25% so far. No telling how much the new belly pans and the reduced air inlets in the front will help.

What was I thinking? I might have done more harm than good!
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Old 08-15-2011, 03:51 PM   #174 (permalink)
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Originally Posted by orbywan View Post
You’re absolutely right, and let me give you an example. With no formal training in aerodynamics I just embarked on a very ambitious project, inspired to a large degree by the other ‘unwise’ people on this web site who have done amazing things with little or no formal training in this area. I took a rather large class C motor home which used to average 12 to 13 miles to the gallon on a good day, and by adding a boat tail, showed an improvement of about 25% so far. No telling how much the new belly pans and the reduced air inlets in the front will help.

What was I thinking? I might have done more harm than good!
Keep doing what you're doing. It's working.

Future suggested projects to consider:

1. Aero motorcycle mirrors to replace Dumbo the Elephant ear mirrors on Econoline van. Or, since you already have electronic cameras, eliminate outside mirrors entirely.

2. Garage door/lawn edging plastic air dam/spoiler

3. Pizza pan aluminum wheel covers

4. Wheel fairings per Prius or, better, per Aerohead's trailer

5. NACA duct inlets and outlets for belly pan cooling air

5. Aero-ized or covered windshield wipers. Maybe use of RainEx would make possible the complete elimination of windshield wipers.

6. Using redeployed existing cameras to fine tune all the above, esp. belly pan and wheel fairings, with real time tuft testing at highway cruise speed. After all, that's what you're trying to improve, so test at highway speed in case the airflow differs from lower speeds.

Last edited by Otto; 08-15-2011 at 04:06 PM..
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Old 08-15-2011, 03:54 PM   #175 (permalink)
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Old 08-15-2011, 04:59 PM   #176 (permalink)
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Originally Posted by wyatt View Post
Here is a van that has had some significant work done in terms of aero-improvements.
......... almost everything past the truncation is detached flow anyway.
Not to argue, but they look pretty flat to me, at least most of them. Does it have to be all of of the Tuffs laying flat?



EDIT: I do see that none of the Tuffs in the last 18" to the rear point are flat. Is this what you were pointing out?
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Old 08-15-2011, 06:49 PM   #177 (permalink)
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Originally Posted by Otto View Post
Keep doing what you're doing. It's working.

Future suggested projects to consider:

1. Aero motorcycle mirrors to replace Dumbo the Elephant ear mirrors on Econoline van. Or, since you already have electronic cameras, eliminate outside mirrors entirely.

2. Garage door/lawn edging plastic air dam/spoiler

3. Pizza pan aluminum wheel covers

4. Wheel fairings per Prius or, better, per Aerohead's trailer

5. NACA duct inlets and outlets for belly pan cooling air

5. Aero-ized or covered windshield wipers. Maybe use of RainEx would make possible the complete elimination of windshield wipers.

6. Using redeployed existing cameras to fine tune all the above, esp. belly pan and wheel fairings, with real time tuft testing at highway cruise speed. After all, that's what you're trying to improve, so test at highway speed in case the airflow differs from lower speeds.
Thanks for the suggestions Otto. For #1, Since I have to see to either side in case the mirrors cut out I may reduce the size of the big mirrors and eliminate the fisheyes. I'm going to make some panels for either side to streamline the front considerably, which intersect with the mirror mounts so I'll address the side mirrors when I fab those panels.

#2, I'm going to try some testing with the new belly pans without the air dam for now, see how it does and leave the whole thing alone for a while so I don't beat it to death with a hammer. Then add an air dam later after I find some on-demand smoke. I think the air dam and the wheel mods are going to have to be smoke/flow tested to have the air flow around the wheels optimal, otherwise I'm just going to be stabbing in the dark with no idea of what's actually going on down there.

#3, Not possible in the front, and don't want to do that with the duallies. I'm concerned about overheating the brakes in the mountains when I tow various toys. I'll be restricting the air flow enough with the belly pans and the wheel fairings.

#4, Yes, I'm looking forward to that, I think there's a lot to be gained there if I can get some good video with the smoke/flow testing and can observe what the air is actually doing in those areas.

#5, I'm looking for some of those.

#6, Roger that. I'm going to hook up a DVR to the system so I can record some of the tests, it might be interesting to see. I'll have to figure out how to do a video link to here. Maybe UTube?

Well it should be up to a 100 or so out there, time for more fun with the differential. I'm taking the easy way out for now and doing it simple. When I get the equipment to do the smoke/flow testing I'll see how the air behaves back there and do the articulated cover if it needs it. For now I just have to finish this and get to the nearest trout stream so I have a reason to sit on my butt and drink beer.

Anybody know where I can get the best on demand smoke generator for on the road testing?
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Old 08-15-2011, 06:52 PM   #178 (permalink)
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Originally Posted by kach22i View Post
Not to argue, but they look pretty flat to me, at least most of them. Does it have to be all of of the Tuffs laying flat?



EDIT: I do see that none of the Tuffs in the last 18" to the rear point are flat. Is this what you were pointing out?
That damn van is what got me in all this trouble in the first place. Ha!
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Old 08-15-2011, 07:58 PM   #179 (permalink)
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Quote:
Originally Posted by orbywan View Post
Quote:
Originally Posted by Otto View Post
3. Pizza pan aluminum wheel covers
#3, Not possible in the front, and don't want to do that with the duallies. I'm concerned about overheating the brakes in the mountains when I tow various toys. I'll be restricting the air flow enough with the belly pans and the wheel fairings.
Quote:
Originally Posted by Otto View Post
4. Wheel fairings per Prius or, better, per Aerohead's trailer
#4, Yes, I'm looking forward to that, I think there's a lot to be gained there if I can get some good video with the smoke/flow testing and can observe what the air is actually doing in those areas.
Quote:
Originally Posted by Otto View Post
5. NACA duct inlets and outlets for belly pan cooling air
#5, I'm looking for some of those.
Fair and cover to your heart's content. If you're already planning on ducting cooling air through the belly pan, run another duct to each side for the brakes.
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Old 08-16-2011, 05:19 PM   #180 (permalink)
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underside

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Can I do the underside same way. Make correct size and Flip the template over and put it on the same place as roof side template. Or do I have to use the lower half of the template to underside of the boattail also?
Vekke,the underside is covered in Hucho's section on diffusers.
The upsweep angle of the diffuser will depend on where the upsweep originates.
I believe that if before the rear axle,the angle can be as steep as 4-degrees.
If it starts after the rear axle,then 2.5-degrees is the limit.Please check Hucho's work to verify.

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