Full Sized Boat Tail? Picture inside

[cashcow]

I used the aero template from ecomodder and tried to figure out just how long a full sized boat tail would be for our rav4 ev. I came up with that template up there and also another where the template slopes faster than the tampering on our rav4 ev's roof @ the end.

I don't know which is more accurate.

I tried to match the highest point of the windshield with the highest point on the aero template, but maybe it is because of the background... but it was really hard. So the difference between both of these is just 1 size bigger from the sizes available in the eccomoder aero tool.

One thing I noticed, at least when using this template, is that the boat tail must be over %50 the length of our ra4 ev?! That uh... feels to be pretty long. Rav4 EV is 180" long so half of that is 90" and if we turn that into feet that is 7.5 Feet!

And at least from what I can tell ... a full size boat tail looks to be more like 75% the length of our RAV4 EV. That is me taking a guess since I haven't actually measured the images (Full sized Rav4 ev in that pic is 180") and compared that to the left over space the temple needs to be 'full aero'.

What do you guys think? Is this even right? Here is the tool @ eco modder if you guys want to play:

http://ecomodder.com/forum/tool-aero-template.php

 

[michael]

Do you have an estimate of the benefit? Like at 65 MPH range would increase by a factor of so much?

 

[cashcow]

Someone placed a boat tail on a Geo Metro and gained a %15.1 improvement on their MPG:

http://ecomodder.com/forum/showthread.php/project-geo-metro-boat-tail-prototype-15-mpg-10691.html

The Geometro has a 0.32 Drag coefficient and our Rav4 EV has a 0.31 Drag Coefficient, so they are pretty close in that sense. I'd think a range improvement of %15.1 could be expected. It could be more or it could be less. I looked through Eco Moder and there really isn't any evs with boat tails, so no one really knows if you can expect the same type of benefits as a gasser.

One thing is certain here our Rav4 Ev is much bigger than the Geo Metro so it is making a bigger hole as it rams through the air on the FWY. The bigger the hole is the more effect it has on millage.

https://www.dropbox.com/s/3bcv212xxsfd2vr/Rav4rangeChartV90.2.pdf?dl=0

Looking at the range chart with 10% degradation 90% capacity going at 55 mph you should get 147 miles from the RAV4 EV. A 15.1% improvement would add about 23 extra miles for a total of 170 mile range.

It is all speculation, but like how Tony has said if we are talking about Aero Improvements then a full size boat tail is where the most benefit will be. The boat tail is the more complex project. There are other things you can do like Front and rear wheel skirts, suspension lowering, mirror deletes, Partial grill block, and also full wheel tire fairings.

I also bet you can get some aero improvement by working with the undersides of the rav4 ev. Not sure how the bolted on battery at the bottom affects aero down there though I know the rav4 ev has a belly pan of sorts! Also the sloping angle of the front of the hood to the windshield is another option.

Anyway, the cost for a boat tail should not be very high. You can make it with things you might have laying around the house already and you can get free card board from a lot of places. I'd guess it could cost about $30 usd? Or free if you have everything already in the house.

Actually here is a Geo Metro with a full size boat tail and other mods converted to electricity and a 200 mile range on lead acid batteries.

http://www.evalbum.com/3242