Fiberglass vs. weight
08-16-2021, 09:27 AM
#1
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Fiberglass vs. weight
This is not a "fiberglass vs. metal quality" question.
I'm looking into a widebody conversion on a 76 coupe. 3.0.
Car will be tracked, so looking for some weight loss.
My question - and it might be a stupid one - can anyone comment on weight distribution affected by this change?
The front wings are pretty heavy in metal. The rear will stay metal.
I'm looking into a widebody conversion on a 76 coupe. 3.0.
Car will be tracked, so looking for some weight loss.
My question - and it might be a stupid one - can anyone comment on weight distribution affected by this change?
The front wings are pretty heavy in metal. The rear will stay metal.
08-17-2021, 02:00 AM
#2
Burning Brakes
1) Why a widebody conversion on a track 911? That is a cosmetic change that adds weight to the rear, in a car that is already tail-heavy.
2) Swapping steel front fenders (and hood) for fiberglass (or carbon fiber) will reduce overall weight, but will likewise exaggerate tail-heavy weight distribution in a 911.
For a track car, weight distribution is at least as important as overall weight. For a track car, form follows function, and a bit of goal-directed planning goes a long way.
2) Swapping steel front fenders (and hood) for fiberglass (or carbon fiber) will reduce overall weight, but will likewise exaggerate tail-heavy weight distribution in a 911.
For a track car, weight distribution is at least as important as overall weight. For a track car, form follows function, and a bit of goal-directed planning goes a long way.
Last edited by raspritz; 08-17-2021 at 02:05 AM.
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08-17-2021, 02:20 AM
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1) Why a widebody conversion on a track 911? That is a cosmetic change that adds weight to the rear, in a car that is already tail-heavy.
2) Swapping steel front fenders (and hood) for fiberglass (or carbon fiber) will reduce overall weight, but will likewise exaggerate tail-heavy weight distribution in a 911.
For a track car, weight distribution is at least as important as overall weight. For a track car, form follows function, and a bit of goal-directed planning goes a long way.
2) Swapping steel front fenders (and hood) for fiberglass (or carbon fiber) will reduce overall weight, but will likewise exaggerate tail-heavy weight distribution in a 911.
For a track car, weight distribution is at least as important as overall weight. For a track car, form follows function, and a bit of goal-directed planning goes a long way.
However, not a track car, but a (street) car that will be tracked (on track days).
So a good "weight distribution" between form & function is the goal
08-17-2021, 03:53 PM
#5
08-17-2021, 04:31 PM
#6
True. But he is adding wt. to the rear. I guess the real question is whether to work on the polar moment as much as possible, or to balance the F/R wts. as much as possible...
Then there are the possibilities of relocating the battery and oil tank to the smugglers box...
Then there are the possibilities of relocating the battery and oil tank to the smugglers box...
08-17-2021, 05:02 PM
#7
It's been my experience that for track use, excluding safety and reliability concerns, aero is all important followed by mechanical grip and then polar moment
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08-18-2021, 12:57 AM
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Burning Brakes
I suspect it's a bit far afield from the OP's purpose, but aero would not be allowed in non-PCA vintage racing.
08-18-2021, 02:57 PM
#10
This is a "a (street) car that will be tracked (on track days)" - not clear to me what exactly that means re vintage racing, class, or just DEs on a track.
But since we have unfettered access to ()conceptually mod the OPs car... how about no fat butt, but instead strip it bare and stitch weld the whole thing?
But since we have unfettered access to ()conceptually mod the OPs car... how about no fat butt, but instead strip it bare and stitch weld the whole thing?
08-19-2021, 06:51 AM
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This is a "a (street) car that will be tracked (on track days)" - not clear to me what exactly that means re vintage racing, class, or just DEs on a track.
But since we have unfettered access to ()conceptually mod the OPs car... how about no fat butt, but instead strip it bare and stitch weld the whole thing?
But since we have unfettered access to ()conceptually mod the OPs car... how about no fat butt, but instead strip it bare and stitch weld the whole thing?
08-19-2021, 12:41 PM
#12
Why do you want to go to 930 or larger fenders?
Looks? handling? bigger wheels & tires?
If it were my car I'd think long and hard about what you expect from the car when done and how all the changes you propose affect the car and each other.
for instance, 930 fenders sure do look cool, but the aero cost is also pretty large and w/ a relatively anemic 3.0 that can be a debilitating change, add to that the potential gearing and inertial costs of the usual big wheels and tires and you end up w/ a car that performs more poorly on the track but sure does look cool parked at the local malt shop.
Here's a summery of the aero characteristics on most 911 variants, the '74 3.0RS and the 'G/H series are most pertinent to you
If you want a streetable car that you can take to the track occasionally and performs well in both environments w/ a stockish 3.0 and stockish mid '70s 915,
first address the safety and control issues
are you going to retain the 45yr old stock 3 point belts(crazy as it sounds this is still ok at most DE events) or go to a 5 or 6 point harness
if going to a harness then the seats need to be changed as well, you' likely want to change them any way to stay planted in the seat on track also the harness needs an attachment point behind the driver, a half cage is the best way to go here
brakes can be an issue, particularly for the new driver, to avoid expensive upgrades in this department the car needs to be as light as can safely be done, and the fluid and pads need to be fresh and track oriented, while reducing weight the priority list goes as follows, front end, back end, tires this reduces rotating weight( obviously the tires rotate but the car also rotates in pitch and yaw) and if done right gives a gearing boost at the same time
Looks? handling? bigger wheels & tires?
If it were my car I'd think long and hard about what you expect from the car when done and how all the changes you propose affect the car and each other.
for instance, 930 fenders sure do look cool, but the aero cost is also pretty large and w/ a relatively anemic 3.0 that can be a debilitating change, add to that the potential gearing and inertial costs of the usual big wheels and tires and you end up w/ a car that performs more poorly on the track but sure does look cool parked at the local malt shop.
Here's a summery of the aero characteristics on most 911 variants, the '74 3.0RS and the 'G/H series are most pertinent to you
If you want a streetable car that you can take to the track occasionally and performs well in both environments w/ a stockish 3.0 and stockish mid '70s 915,
first address the safety and control issues
are you going to retain the 45yr old stock 3 point belts(crazy as it sounds this is still ok at most DE events) or go to a 5 or 6 point harness
if going to a harness then the seats need to be changed as well, you' likely want to change them any way to stay planted in the seat on track also the harness needs an attachment point behind the driver, a half cage is the best way to go here
brakes can be an issue, particularly for the new driver, to avoid expensive upgrades in this department the car needs to be as light as can safely be done, and the fluid and pads need to be fresh and track oriented, while reducing weight the priority list goes as follows, front end, back end, tires this reduces rotating weight( obviously the tires rotate but the car also rotates in pitch and yaw) and if done right gives a gearing boost at the same time