Rounded corners vs. Straight edges on kammback

[ChazInMT]

When you say you're aiming for 15', I'm 99.9% sure you don't mean 15 feet!! Do you mean 15 inches? or 15°? (Press and hold "Alt" while typing 0176 when you let alt go, you get a ° symbol) Cause 15° would not be optimal. You need about 7 inches from the back of your trunk lid to the top of the back of your Kamm to really get the best out of this. When I figured the angles before, 8° would be the optimum angle based on level ground. Anyway, I gave you all that stuff on post 27 so I suppose it would be silly to restate it all.

Mind you, if you take it down to an inch or so above the lid, it will still get you a decent net gain, but it won't be as good as keeping it high. You really want to stick with the template.

I thought of a way to run the traps on mine if I build it, I'll put in rollers and run them out the back, that way I can have long straps, pull them through, and just tie them in a knot in the back to keep them out of the way. That way I don't have to put any weirdy holes on the top of the Kamm. : P



Keep up the good work! Looking forward to seeing how you do it. I just might scrap my wood idea. I know the way MotorNeck is building his Aerocap has me rethinking a way to build a prototype of my own design for my GMC Sierra. his build thread is here.

Ford Ranger Aero Canopy

[freebeard]

ChazInMT -- I've been sitting on this waiting for my forthcoming 'Project, the Third' thread, but that's probably a week away; so here, now:

I'm thinking for a boat tail, construction of redwood benderboard (1/4"x4"x16') I have stockpiled. Over a plywood bulkhead and stringer form, steamed redwood bent into ribs and tapered or gored strips maybe 2" wide longitudinal.

Voila, compound curved redwood plywood about 1/2" thick.

Then sand to contour and one layer of glass cloth, and resin squeegeed out under Mylar plastic to get a gloss finish in one go.

Whadaya think, sirs?

[Varn]

Chas in mt
Time to put your theoretical knowledge to use and build something and start saving some of those gallons. Attach your cover any way you want to. For a prototype make your rear cover using simple 2D panels. A 1" panel of pink board will bend nicely in a shape.

I wanted to keep my trunk functional on my VW so I did the rear area in two sections. I get straight tails off of the back of the rear of the rear foil. I have preserved rear vision under the rear foil. My trunk opens.

You might provide valuable information to all others on this list by building something even if your first construction is not ideal it may provide insight.

[2000neon]

Ha ha oh yeah, I had meant 15 degrees, not feet, but I am typing on a blackberry so some symbols are tough. Wow is the angle that shallow? I am aiming to build it as close as possible as the picture you posted.

[Varn]

You might make yourself a tree from some heavy wire. Hang ribbons on it and you will see where the wind goes. Mount your tree on the trunk lid close to the rear window to see where the wind is going. Find the lowest height that the wind is blowing straight back. Make your fairing go to the point that you have identified and then run the experiment again only further back another foot or so.

[christofoo]

Originally Posted by ChazInMT

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That's what I've been thinking too. Similar to the way my bike rack mounts on the trunk.

Trunk access still bothers me though. My lady doesn't want something she has to take off. If there's a practical way to make it two pieces with a hinge, I haven't worked it out yet.

As far as paint protection goes, I picture attaching weather stripping to the Kamm where it faces the car, hopefully that won't leave a mark.

I also am gravitating toward a louvered Kamm; a) doesn't require tranparent material, therefore can't fog up, b) I expect a louvered window to never get frosted overnight, less scaping for me, c) reduced solar heat gain, lower parking temperature and more comfortable back seat.

[ChazInMT]

Originally Posted by christofoo

That's what I've been thinking too. Similar to the way my bike rack mounts on the trunk.

Trunk access still bothers me though. My lady doesn't want something she has to take off. If there's a practical way to make it two pieces with a hinge, I haven't worked it out yet.

As far as paint protection goes, I picture attaching weather stripping to the Kamm where it faces the car, hopefully that won't leave a mark.

I also am gravitating toward a louvered Kamm; a) doesn't require tranparent material, therefore can't fog up, b) I expect a louvered window to never get frosted overnight, less scaping for me, c) reduced solar heat gain, lower parking temperature and more comfortable back seat.

Hey, don't mean to be a pill, but, I figure it doesn't matter how "Soft" the thing on the paint is, bits of sand and dust will get between the gasket and finish on the car and mess it up. I thought to use a clear tape mounted to the paint itself too, but that has its own built in problems.

I have a theory, and it's only really held by me, that the air moving back into place as it rolls down the back of your car, has energy to return to the car. People freak out when I say that, had a thread on the theory here:

Up & Down Theory on Aero Optimization

Anyway, when looking at louvers through the lens of this idea, it is less then optimum. As always, I have to say that filling the wake will always yield a better result than nothing. But at the end of the day, we want the air to return it's potential energy to the car and in my mind, the air cascading down the louvers does not have the angled surface to push against.

So the louvered Kamm will help by eliminating the potential for large vortices to form at the back of the car, but it does not allow the air to push on the car.

[Sven7]

As to the hinge, I haven't gone through all seven pages but what about this? Break it into two sections, hinge the top.

[KamperBob]

Originally Posted by Sven7

As to the hinge, I haven't gone through all seven pages but what about this? Break it into two sections, hinge the top.

Thinking along the lines of the partial tonneau for truck beds (front open, rear closed) I wonder. Suppose the rear fit the template and was attached to the trunk lid. Chop the front the least amount to allow the trunk to open. A gap would remain of course but minimize it. I'm thinking simple to build with good bang for the buck. Perfect is the enemy of good enough.

[Varn]

What I did was to put a layer of duct tape on the painted surface and build my part right onto the duct tape. Once the part was built just pry it off the duct tape (which is an excellent mold release) and then fasten the part right back on the car with pop rivets. Your car is almost as old as mine. A dozen pop rivet holes is no big deal if you don't like the part. I was and perhaps will still build a louver but right now I just use a single wing.

Think of the Camaros of the 80's