Flat Bonneville-type spoiler

[brucepick]

Originally Posted by California98Civic

The raised lid (partly built) is almost three inches above the current trunklid and has a flat spoiler that extends to almost the end of the bumper. Accomplishing a really snug fit to the window and sides is difficult if I am to retain use of the trunk. A functioning trunk and visibility out the back window are essential. I'm wondering about fitting those rubber insulators used to seal household doorjambs into these gaps for the "snugness" that produces dead air under the raised lid.

I've been thinking about these too.

For rear visibility - I think one could angle the spoiler downward, so that from the center mirror's viewpoint, it sees just the edge of the spoiler. I think the resulting downslope will be OK if it starts at the rear glass or comes close to it. If building a spoiler that's just a few inches front to rear, located over the rear trunk edge, that slope might cause lift.

Ideally, I'd like to first find the ideal height for the spoiler's rear edge, even with the bumper. Then adjust the forward edge up as needed for good visibility via the mirror.

[brucepick]

Aero-wizards,

I'm pretty sure the idea here is for the rear edge of spoiler to meet the template curve. Right?

How about the slope of the spoiler, and it's front-to-rear dimension? Is any part of the spoiler that is forward of the template mostly inert, with little or no effect? Or is it helpful to extend it forward to or near the rear glass - that way very little air will flow into the cavity below the spoiler.

Going past the template line would be bad, right? Tuft testing should show turbulence there??

And, how about sloping it downwards? I think on a "normal" spoiler, that would cause unwanted lift . BUT if the forward edge is at or near the glass, wouldn't a downward rear slope help the flow reattach more smoothly?

Thanks!!

[California98Civic]

Originally Posted by brucepick

Aero-wizards,

I'm pretty sure the idea here is for the rear edge of spoiler to meet the template curve. Right?

How about the slope of the spoiler, and it's front-to-rear dimension? Is any part of the spoiler that is forward of the template mostly inert, with little or no effect? Or is it helpful to extend it forward to or near the rear glass - that way very little air will flow into the cavity below the spoiler.

Going past the template line would be bad, right? Tuft testing should show turbulence there??

And, how about sloping it downwards? I think on a "normal" spoiler, that would cause unwanted lift . BUT if the forward edge is at or near the glass, wouldn't a downward rear slope help the flow reattach more smoothly?

Thanks!!

I'm not an "aero wizard" but I'll respond briefly. My tests confirm what some were suggesting: that the slope matters and that an upward angle risks counterproductive downforce. My designs were very close to (or on) the template line. I think turbulence can occur anywhere "under" the template. I think it is mainly a matter of how air is separating (poorly) from the passenger cabin at and around the rear window and the trunk area. That is my imperfect knowledge from this site and reading, so far.

[cfg83]

brucepick -

(not an aero-expert either, but I'll give it a shot)

Originally Posted by brucepick

Aero-wizards,

I'm pretty sure the idea here is for the rear edge of spoiler to meet the template curve. Right?

Yes.

How about the slope of the spoiler, and it's front-to-rear dimension? Is any part of the spoiler that is forward of the template mostly inert, with little or no effect? Or is it helpful to extend it forward to or near the rear glass - that way very little air will flow into the cavity below the spoiler.

My sense is that you have to tape the spoiler from front to back. See how the EV1 tapers from front to back in the top view? You *want* your car and spoiler to do the same. I think you want to get as close to the glass as possible. In my case, because I have a rear window wiper that would mean I would want to be as close as possible while still allowing for the wiper to be able to clean the rear window.

Going past the template line would be bad, right? Tuft testing should show turbulence there??

Yes. I think you want to do the prototype with the ability to adjust it forward and backward. The template gets you close and testing dials it in,

And, how about sloping it downwards? I think on a "normal" spoiler, that would cause unwanted lift . BUT if the forward edge is at or near the glass, wouldn't a downward rear slope help the flow reattach more smoothly?

Thanks!!

I am paranoid that the wind from the top and side of the car would get under the horizontal part of the spoiler, turn it into a parachute, and rip it off. I would make it so that it has a slight downward(*) angle. I would also protect the sides of the spoiler from wind getting in from the side. The sides of the Bonneville spoilers seem to accomplish this, whether by design or by chance.

[EDIT: (*) My brain is thinking that it has a downward slope from the point it meets the template.]

That thought process has led me to imagine this design for my wagon :



The green line is the flat spoiler.

It features side protection to protect against a parachute effect, a *slight* downward angle, clearance for the rear window wiper, extension only to the rear bumper line, and maintains about 80% rear visibility.

CarloSW2

[some_other_dave]

The green line looks to have an upward slope, not downward.

The red part looks an awful lot like a mini-Kamm-back.

-soD

[cfg83]

some_other_dave -

Originally Posted by some_other_dave

The green line looks to have an upward slope, not downward.

The red part looks an awful lot like a mini-Kamm-back.

-soD

Ok, I am describing it wrong. My brain is thinking that it has a downward slope from the point it meets the template. Sorry about that. It does have an upward slope from the front of the car to the back of the car.

Yes, it's a mini-Kamm-back with a horizontal spoiler in place of the enclosing roof extension. A compromise to maintain visibility.

Stupid brain always thinks wardsback.

CarloSW2

[Pendragon]

Originally Posted by California98Civic

<snip>All I want is cleaner separation. If I can get that, I think I am done.

I can not think of where I saw a reference to the small spoilers such as the one on the Honda Civic Hybrid which indicated that they were simply there to achieve a clean separation of airflow on rounded trunk surfaces. I will have to see if I can find it.

That was some informative testing you did. Thanks for posting back about it.

[brucepick]

Actually Aerohead already posted on this general concept, back in post 126 in this thread.

Originally Posted by aerohead

... On current production cars you'll notice that the trunklids are a lot higher. The air likes this.

You could construct a 'hollow' projection which runs above the trunklid,from the backlight,out to as far as the bumper,which has sides which wrap down to meet the sides of the car. It would be like the 1982 Pontiac Trans Am Firebird,only full-length.

You'd be able to look right through it. The air would re-attach onto the back of it,capturing a vortex above it like Lamborghini, Porsche, Lotus, and Ferrari have used with their backward facing step backlights.
Just thinking out loud.

So, continue the sides rearward and make them be the side panels of the "new' raised trunk lid aka spoiler. Have the spoiler side edges meet those panels. However I do believe that for the rear view mirror to see only the spoiler's edge and allow maximum vision out the rear, the forward edge will have to be raised an inch or two. I don't think that would be a bad thing.

[California98Civic]

Originally Posted by Pendragon

That was some informative testing you did. Thanks for posting back about it.

Thanks man. It was interesting, if time consuming.

[California98Civic]

Originally Posted by brucepick

Actually Aerohead already posted on this general concept, back in post 126 in this thread.

So, continue the sides rearward and make them be the side panels of the "new' raised trunk lid aka spoiler. Have the spoiler side edges meet those panels. However I do believe that for the rear view mirror to see only the spoiler's edge and allow maximum vision out the rear, the forward edge will have to be raised an inch or two. I don't think that would be a bad thing.

High Brucepick. I agree. I started a new thread on it because I felt odd talking over a trunk lid project under the heading "Bonneville flat spoiler" anymore. Maybe it was a mistake, but there you go. Here's the thread: http://ecomodder.com/forum/showthrea...ect-17708.html I can see under the lid, through the interior mirrors.

I'm working on tuft testing and fine tuning the prototype after a frustratingly poorly designed test.