Roof spoiler?

[onixbonilla]

Hi everyone.
Will like to know the best way to attach the carbon fiber roof spoiler?
Thanks
Onix

[zen]

i used RTV (black silicon) based on the recommendation of Carbon Joe. worked like a charm and filled the gaps on mine since mine is a chop top and the roof is slightly off from stock.

[onixbonilla]

Great!
Thanks for the response Zen!!!
Onix

[volkdent]

Hey Guys,

I've been giving this roof spoiler thing a lot of thought. It is in the exact right location, but involves gluing or screwing a spoiler right smack dab in the middle of your lovely painted roofs.

I have another idea. I havn't yet seen one of these, but I will be building one eventually, and hopefully you guys will get your brains going too. It involves a wing/spoiler that either polyurethanes or even HD 3M double side tapes to *****drumroll******* the rear window. YES, you heard it here first, think of the location the NB turbo rear wing is. It is still high up on the car in the airflow and would be very good at preventing lift, and could be much smaller unlike the big alu wings you see farther down the rear end. By that far down, a lot of the lift has already started. Anyway, this wing could be made of fiberglass or CF, and would just be glued to the rear window.

Initial complaints will be "window, OMG, that's too weak!", but really, A: how fast are you going to go in a bug, B: how big a wing is it going to be C: if it really pushed down on the car that much the roof spoiler would dent the roof right? Those rear windows are a total bich to get out, and with the load of the wings force spread out over the entire top edge of the window, I can't immagine we would ever see a window "blow-in".

I asked Carbon Joe about this, and he could probably duplicate it in CF if we make a plug that we like.

Thoughts?

Jason

[oasis]

I liked the drumroll.

Okay, seriously, for what car are we thinking here? The Beetle/Super Beetle has at least four rear window configurations. Then, there are Karmann Ghias, Type 3 Fastbacks, ...

I'm also wondering from the standpoint of function. Using the New Beetle as an example, there are two main spoilers used. One is the electric one above (or if you prefer "in front of") the rear glass; the other is a static, crescent-looking contraption below the rear window. I have to wonder how effective the latter is despite its larger size.

I bring this up because the rear window on any of the Beetles is lower than the roofline to begin with. I'd be more concerned the accessory did nothing at all than it pushing in the window.

[volkdent]

Originally Posted by oasis

I liked the drumroll.

Thanks, I'm cheese all the way OK!

Okay, seriously, for what car are we thinking here? The Beetle/Super Beetle has at least four rear window configurations. Then, there are Karmann Ghias, Type 3 Fastbacks, ...

Initially and specifically, I'm thinking about the type 1, but the concept could be used on many.

I'm also wondering from the standpoint of function. Using the New Beetle as an example, there are two main spoilers used. One is the electric one above (or if you prefer "in front of") the rear glass; the other is a static, crescent-looking contraption below the rear window. I have to wonder how effective the latter is despite its larger size.

Precisely, the wings lower down I suspect aren't nearly as efficient in creating downforce as the wings higher up. I was in fact referring to the electric one. VW put it there for a specific reason, perhaps one being looks, but they could have put it at the bottom of the window, instead they chose the top.

I bring this up because the rear window on any of the Beetles is lower than the roofline to begin with. I'd be more concerned the accessory did nothing at all than it pushing in the window.

Yep, I think some lift will aready be acting on the roof before it gets to the rear window, but at least thats a good place to nip it in the bud, because I supect the vacuum only increases the farther down the rear end you go.

Jason

[volkdent]

There has to be some engineers who are into GL, I'm sure someone with a little bit of education in that direction could help us out. What about computer modelling simulation of airflow!!!

Jason

[Uber Affe]

1. Q. What do ALL bugs have in common regardless of year in the exact same place?

Answer...

Drumrolll....(and symbols)

Rain gutters!

You heard it hear first folks!

Think someone could configure a small and simple spoiler that just fastens on like the roof rack or rear deck lid rack?

I know...it's soooooo far off the sides...just a thought.

lemme know why this is a good idea or why it sucks big rotten eggs.

=)

Gabe Sainz

[volkdent]

I like the idea, it's just that anything on the gutter will affect the look of the bug, those lines are some of the distinguishing lines.

Jason

[zen]

Originally Posted by volkdent

There has to be some engineers who are into GL, I'm sure someone with a little bit of education in that direction could help us out. What about computer modelling simulation of airflow!!!

Jason

i recall at least one thread on this some time back. haven't done the search to find it though. basically comes down to just disturbing the airflow as it comes off the back. Carbon Joe's spoiler is at about the best possible position as i understand it (which means take it with a grain of salt). the top of the rear window would have about the same effect i would suspect. i have that setup on my Passat as a matter of fact using a BMW 3-series trunk lip spoiler, but that is apples and oranges.

just about anything you do to disturbe the airflow some would be a plus. garbage in, garbage out. the shape of the bug just wasn't designed for optimized airflow. you can only make it better. it will never be great.

[BWE]

I like the "*****drumroll*******" !

Though I'm not an engineer, I will hopefully be doing some on road (real time) testing of wind flow/ air pressure differences over, under, and though a '70 std. Beetle this summer. Although the data will not be NASA quality, we are hoping to get a good idea of the air flow dynamics of a beetle as it travels down the road. I originally decided that I wanted to do this to find the best location to intake cooling air for the engine compartment (under car scoop, NACA ducts in the rear quarter windows, etc) as well as see if there is any advantage to cooling by changing the rear apron, engine tin, etc.
I'll be posting the raw data here, as well as any mockups, trials, etc.
Cheers,
Dave

[volkdent]

BWE, sounds great! I'm sure that data exists alreadys somewhere, but like many things in time, it seems to be lost. I have the same questions about airflow. My two concerns are airflow for a front mounted radiator in front of the frame head, and the second is airflow for 2 intercoolers mounted in the fronts of widened rear fenders. If you go to

http://www.airkewld.com/project/index.php

and check out H2Oval, you'll see he's put intercoolers in the side. I'm really not sure if he's going to get the airflow there, and he's done a lot of cutting and welding, I hope it works out.

I'm planning the same type of IC setup, just with the intercoolers in the lower part of the front of the rear fenders.

Thoughts?

Jason

[Uber Affe]

Hey...

want to know more about bug aerodynamics?

goto

http://www.maggiolinoweb.it/technique.html

they have an aerodynamics section.

I also distinctly remember a "tv" article on a disney show for Epcot Center that
featured the VW Beetle as a very aerodynamic vehicle (this was of course in comparison to huge 70's vehicles like the Oldsmobile Toronado and a Buick?!)

anyway...maybe you guys can find more?

G/Sainz

[Chris Percival]

Spoiler hight at the rear of a bug is a compromise between reducing lift and reducing drag. The higher the spoiler the better the it is at reducing lift, but the more drag it creats (caused by large turbulent area behind vehicle). If you lower the spoiler, the air flows further down the back of the bug, creating more lift, but the turbulent area behind the bug is reduced, reducing drag.

So, if you care more about lift reduction, go for a high wing. If you want lift reduction, but drag is also important to you, go for a lower wing.

My spoiler is level with the bottom of the window (it attaches to the rear vents). However it still reduces lift, but doesn't have a detectable effect on top speed.

[Wally]

Originally Posted by Chris Percival

Spoiler hight at the rear of a bug is a compromise between reducing lift and reducing drag.

Though english is not my native language, shouldn't that be increasing drag? Otherwise it wouldn't be such a compromise (?) Somehow I think that spoilers will increase drag almost always, especially if they give you downforce. Or am I getting s/th not here (although I am an engineer, just not in aerodynamics )?
Thanks.

Anyone still remember the duck tail spoiler copied from the '73 Carrera RS 911 model?
They made some copies of it for on a bug engine lid in the seventies/eighties. Looked weird, but I wonder if that worked thesame for the bug as it obviously did for the 911? Porsche surely got some R&D into that design which we can use (again)...

Regards,
Walter