I'm using Internet Explorer and I think that's why the template never works for me? I use my pc at work and at home use a company laptop so IE is it for me, for now.
I think I understand the interactive
template tool but want to be sure.
I also reference this picture
The numbers across the top start at 0 and count up in increments of 10, this is percent of 1.78d (kammback length) after the point of max camber, right? (these numbers appear at the bottom of the interactive tool) That's why they stop at about 90% which would be 1.78 d, right?
D is 2H, which is overall height, right? and 2.5d represents the affected zone?
The number across the top (of the interactive tool) start at 0 and go up 3.5, then 7.5, 12, 15, 18.5, etc. These are degrees of taper, right? (meaning the flat roof is zero and 3.5 is 3.5 degrees down from zero, etc)
Overall length of van is 18' 9-15/16" and height is 7' 1". Treating the rear upper edge of roof as point of maximum camber (because the roof is essentially flat front to rear and is over 15' long) and assuming I run a kammback length (total stickout, not surface length of panels) of 20% of overall height (1' 5") should its shape be the same as one 30% of overall height (2', 5-1/2")? I know its degree of taper should change, anything else? Given that length is waaay longer than height (more than 60% difference) but height and width differ by only about 5%, should I extend the kammback length to some other proportion? Would its effectiveness be significantly greater at 40% than 15% of h?
I've read KB bottomside angle should be 2.5°, is this correct regardless of its length?
Obviously I can't extend my van 1.78 times double its height (which equals over 12.5 feet!) past its true point of maximum camber (the upper most corner of its very bluff rear end) so where should I end the Kammback? Obviously longer is better and there is a point of negligible gain (too short to matter) but where should I expect to find the point of maximum drag reduction per length?
I think my absolute max will be something around 30" total stickout. Remember, I'm starting with a vehicle that's barely under 19' long. Standard parallel parking spaces are 20'. Think about that and the fact that I parallel park basically daily at the busiest hospital and 2nd largest college campus in my state and that I live in my state's largest city. I'd like to get something effective that only hangs back 20-24". State law here prohibits anything extending more than 3' beyond the
front bumper. (just noting that here since I found it and may want to find it again)
For my own reference I've worked up the little chart below for rise/run:
0.5° = 1" / 114.6"
1.0° = 1" / 57.29"
1.5° = 1" / 42.96"
2.0° = 1" / 28.64"
2.5° = 1" / 23.86"
3.0° = 1" / 19.08"
3.5° = 1" / 16.69"
4.0° = 1" / 14.30"
5.0° = 1" / 11.43"
10.° = 1" / 5.671"
15.° = 1" / 3.732"
In other words, to get a 15° line from the van's corner you affix a straight line (aluminum concrete screed probably) to it's roof and measure back 3.732" and attach a block 1" thick, measure back 7.464" and attach a 2" block, 11.196" gets a 3" block, and so on. The line connecting the blocks' lower front-facing corners is a 15° line. I'll go about it a little differently than that but you get the idea.
I think I may actually try fiberglassing something up on a hitch mounted stinger. I know it'd be a ton of work and not especially light (by comparison to chloroplast) but it'd be a fun challenge and could be used for future molding or even a swing-away storage pod?!