Zulu's Build Thread (Honda CR-Z)

[CigaR007]

First is kammtail and rear diffuser integration. Wheel skirts will be done once I determine the final shape of the kammtail.

[freebeard]

I like the idea of skirts that flow all the way to a separation edge. If they're light, then why not big?

[CigaR007]

Originally Posted by freebeard

I like the idea of skirts that flow all the way to a separation edge. If they're light, then why not big?

Yeah that seems to be the ideal approach, especially with an added rear diffuser. I see lots of tuft testing once the rough shape is built.

So I ordered 2-part polyurethane foam this morning. My plan is to try and pour 2 or 3 times to form a somewhat rigid single foam block. I believe this approach will cut down on the time needed to carve out the desired shape/taper. It involves more preparation prior to the pour, but the result will be cleaner.

For the time being, I will build a rigid box, between the tail lights. Once the 2-part foam is received, I will proceed to fill the side tapers and the upper part all the way to the third brake light.

I will include a drawing later this evening.

Cheers.

[CigaR007]

View from above, in order to visualize the taper.



View from above, with the inner box.











At this stage, I would fibreglass the structure to strengthen it, but I am out of epoxy resin...

The 2-part polyurethane foam arrives next Monday, so no can do on that front until then. It might be a good time to start visualizing the tapering and curvature. I need to find a way to visualize/confirm whether or not the rear top corners of the box are inside or outside the optimal taper.

What do you guys think ?

Cheers.

[freebeard]

Looks good. Is it removable until Monday?

[CigaR007]

I can remove it, but I will most likely work on the rear diffuser while I wait for the supplies to arrive. To my surprise, the stock rear diffuser is somewhat elaborate. It would just be a matter of adapting it to the new structure.

[CigaR007]

So I hit somewhat of a snag while looking at the rear diffuser. The entire structure was slanted towards the rear. Newbie mistake, as I was mostly working at an angle, the car being on plastic ramps. I figured a way to shim the whole structure without much hassle though. Still has a slight slant, but it is good enough ..as they say. Lesson learned...

I added a smaller box in order to reduce the amount of 2-part foam needed. I also fixed the tow bar rattle/play with a u-clamp.




Started visualizing the curves and taper.













Cheers.

[aerohead]

Nature hates 'angles.' HONDA probably has already incorporated some plan-view body camber at the CR-Z's rear. Once you've got enough clearance for the rear skirts down low, at that point you can begin a 'lead-in' transition into your boat-tail plan taper.
If you just abruptly introduce an 'angle', you've thrown in what will be the adverse pressure gradient which will trigger flow separation right there, violating what Dr. Hucho tells us IS the real solution for 'aerodynamics.'
If you can locate the 'top-view' photographs of Daimler's, M-B 1978 C-111 III, 2016 M-B IAA, and 2022 M-B EQXX, you'll see how they handle the boat-tailing transitions.

[CigaR007]

Took longer than expected to prepare and pour the 2-part foam due to the weather. Pondering whether or not I should tuft test the kamm tail with the rough shape, as is...

It might be a better idea to build the rear wheel skirts, prior to tuft test the whole structure though.

[jimchitas]

First of its really a nice project and the kammtail will help reduce drag i also suggest you to do put a underbody panel if it doesnt exist it will also reduce drag i saw your trying to do a grill block its good but be aware of temperature but its going to be ok i think and i post more images its a pretty intresting project