Shaved gutters: What exactly is the water concern?

[philipguziec]

I'm having my 89 930 daily driver stripped repainted after a bout with an amateur with a buffing wheel and a wheel arch scuff in a parking garage.

I'm considering having the rain gutters shaved. I've looked through the previous posts on the subject. I was a chassis engineer in a previous life and have no concerns about the structure, so I'd like to head off those posts.

However, what *exactly* is the concern with the water flow off the roof?

I understand that water from the roof will run down the sides instead of down the gutter. That is exactly how all of my previous non-porsche convertables worked, and I never had an issue.

Is the water runoff problem unusually bad on a 911? Does it run down into the window mechanism or something? I'd love to hear from anyone who actually owned a car with shaved gutters and drove it in the rain, rather than a second hand story.

Thanks,

[RickM]

Sorry to hear about your bad repair experience.

The only thing that would hold me back from shaving gutters on your car would be permanently altering a very desirable and relatively rare '89 930.

That said, I do like the clean look of the modification.

Good luck and please post pics.

[NoLift911]

Water run-off is of no consequence. Structural integrity is, if done improperly.

Guess it all depends on why? If for looks, great, I personally like it, if for speed there are other routes to take that are just as effective and tons cheaper.

On the flip side for the aero argument - one could argue it takes away from "the rail effect" through the wind, less stability, although I am guessing minute. For those that shave the gutters for aero and keep the flag mirrors not sure what the logic is there ??- best to go with some 935 style or none at all to keep the theme.

You can add winglets in the front (where it really matters) to deal with the rails for a fraction of the cost and easily reversible. Any of this would only apply at high speeds though - say 100+ before then I would guess the results are negligable.

[philipguziec]

First off, back to rain. Anyone actually owned a car with shaved gutters that has driven it in the rain? I'd love to hear a description of firsthand experience.

It's partly aesthetic, partly for noise reduction, and partly because as an engineer, I find the aerodynamics of the a pillar so offensive. Added rear downforce biasing the high speed balance to push would be a bonus. I might weekend warrior the car, but I also drive it.

As for the rare and desirable 89 930, it is my daily driver, and I plan to drive it until the wheels fall off, so collector value is no issue. This year marks the last of the winter wheels and tires though, I'm breaking down and getting a winter car after the paint job. Even the "rare and desirable" 930s, low mileage or no, cost less than a loaded 3 series. It's just a car. If I wreck it, I'll find another.

Cost isn't an issue. The car is being painted by a guy with one man shop and a reputation for pristine 911 work. I got a ballpark of $1000 for the rails. The A pillar fills are $200, plus a couple of hours labor. So, shaving the rails is well less than an additional $1000 - chump change compared to the cost of the paint job and plastic/rubber replacement, and if I don't do it now because of cost, I'll regret it.

[dd74]

Fellow Pelican RDane did this to his car. He also eliminated the wipers and put one large wiper on his car like what is on the newer Mercedes Benz cars.

I think there was some top-end increase in speed, but I don't recall anything about rain.

Do a search on his name (RDane), and see what you can find.

[Facey]

i have seen a few with it, talked with one of the owners.

aside from looking (!) better, he said it also reduced wind noice by a huge amount.

remember that they are actually part of the shell though, and to remove you must cut, tach, cut-tach, cut-tach all the way down in very small intervals to aovid the car mis-shaping...

i wish i did it to my own car at the time of my resotration. not worth it unless the paint and everything is out anyways.


-do it

Nick

[philipguziec]

RDane has good posts out there. Looks like the water thing is a non-issue, from those who have done it. Also looks like it is a real pain, and a lot of work.

I hope it reduces the wind noise, I'll need to compesate for the wind noise from the moveable front and rear corner windows I'm retrofitting.

Thanks, all.

[RickM]

Phil, Has your body guy done them before? His price seems low relative to the work involved.

[LarryP]

It's YOUR car. Do it; you'll love it. Give your body guy a cheap digital camera so maybe he can take lots of photos for us, along the way.

[Zeke]

Any folded seam is gonna be stronger that a butt seam. Do this with caution and excellent craftsmen or don't do it. You could ask the engineers on the board, but I think it puts more stress on the A pillars. Only my .02.

[dean]

I have a couple VW's with no rain gutters. I think lack of rain gutters suck. Water always goes into the interior and down my neck. I would never delete the rain gutters if you drive in the rain.

Go rent a car with no rain gutters and drive in the rain and see it it bothers you.

[randywebb]

I just don't see the fascination with this. It costs $$ or your own labor, likely weakens the structure at least somewhat, and has no functional advantage whatsoever.

[Facey]

why do people have their cars painted?
why do people wash their cars (extensively)?
why do people have their fuch's re-furbished?

looks, looks, and looks.

it makes the 911 roof line THAT much better. especially when combined with ruf/935 mirrors.

the strnegth can be gained back and then some with a half cage or event just a harness bar.

- make sure you keep us updated on your re-paint..

what colour are you going? stock or....

[DUK]

Do it because it looks cool. BTW if done right there is no loss of integrity. I don't care what they say.

[philipguziec]

Hey All,

Thanks for the feedback. I'll be keeping the stock slate grey color.

The 930 is the first car I've owned with rain gutters. I drove exclusively convertibles. Yes, the water runs off the top a bit in the rain. Unless the 930 is much worse than that, it's a complete non-issue for *me*. From anyone who has cut the gutters, I've gotten no feedback that there is anything unusual about the water issues on the 911. So, the water is a non-issue for me.

Now for structure. I personally *was* a chassis engineer at Ford and my Engineering MS advisor consulted to Louis Ruf, and the Porsche factory, which is not more sophisticated in their engineering than Ford. I did structural modelling for a while and I've analyzed just this kind of structure. The seam makes it easy to fold multiple layers of metal together and spot weld them to hold them. So, the top of the 930 is just dropped on and spot welded. That's it. A continuous weld of the three layers will be superior to spot welds offset by some part of material from a stiffness standpoint. There may be some weakening of the toughness of the seam from the impact on the heat treat next to the weld, but engineering judgement would say the structure would be just as tough in an impact. Engineering judgement also says that an impact so severe that the continuous welded seam fractured, wouldn't be survivable in any other car either. Ask another engineer how much structural analysis work they've done.

As for the rest of it, looks and noise reduction are the main reasons for shaving the gutters on a street car. Top speed and aero balance are secondary issues, but can actually be an issue for me. The only downside is a little more rain water when getting into and out of the car - which can't be worse than my convertibles, and cost, which is all a matter of perspective. Why not just drive an VW diesel if you're that cost conscious. I'll be keeping the stock mirrors. The little mirrors are useless according to those that have actually used them. Now *that's* a mod that's a poor choice for a daily driver.


Thanks again for the help. Signing off the thread now.

[ZLP]

The 935 filled in the front and kept the rails for high speed straight line stability. I did the same...

[Scooter]

Originally posted by randywebb
I just don't see the fascination with this. It costs $$ or your own labor, likely weakens the structure at least somewhat, and has no functional advantage whatsoever.

I agree. I must add that I really think the roofline looks incomplete without rain gutters. IMHO.

[Jeff Alton]

Although it has a cool factor, I really don't like the look. just my own opinion mind you. Funny how there is two sides to the stability argument...... didn't Ruf delete the gutters on the yellow bird??

Cheers

[randywebb]

"Engineering judgement also says that an impact so severe that the continuous welded seam fractured, wouldn't be survivable in any other car either."

- That isn't the issue - it is the performance of the suspension in a rigid unit body.

[Jack Olsen]

Where's RDane? I thought he shaved the rain gutters and also got rid of the side mirrors -- didn't he use a parabolic mirror in the center?