Shaving weight from the... door panels

[Jack Olsen]

It's been a long time since my car had stock door panels, so I don't really know how the originals hold up to the weather, or even how much they weigh. But I previously installed a set of RS America duplicates on my fiberglass doors, and while there were a lot of nice features about them, including sound deadening and nice, precise die cuts -- mine had gotten some pucker and warp over time. So I recently decided to re-do them. I wanted the same functionality, but with better water resistance. And I was also curious if I could save some weight.



My factory door caps weighed a little over 2 pounds each, and the aftermarket lightweight RSA door panels added 2 lb 12 ounces to each door.

For weather resistance, I decided to not use wood or cardboard for the panels. Instead I got some corrugated plastic, which is a material made of polypropylene in the manner of corrugated cardboard. The stuff I used was 4mm thick. It's used for things like front-lawn signs and those Post Office sorting boxes (although those are thinner). Covered with leather, my door panels came in at 1 lb 8 oz each.



For the cap, at least on the early cars, Porsche used a piece of formed steel bonded to a pretty dense piece of foam. I tried bending a piece of aluminum sheet over a 2x4 and matched the basic shape. Even covered with leather, my cap pieces were only 12 ounces each.

In this picture, you can see the back-side of the C-shape I bent the aluminum into.



I was a little worried about finding something that would adhere leather to polypropylene, but I did a test with three different adhesives, and a Loctite spray I had on-hand passed with flying colors. (I think some polypropylene is pre-treated with a corona wire to allow inks and adhesives to bond to the stuff.)





I sprayed the adhesive on both the leather and the corrugated plastic. I did the same with the aluminum. To hold the panels to my fiberglass doors, I used M4 aluminum rivnuts. You might notice that the cap pieces have a cutaway portion, my window crank is shortened, and my handles are at odd angles. This is all because I have a cage up against the doors.

But I was able to get most of it done during two stretches this weekend where my wife took the kids out to do something. The leather smell in the garage made finishing it up a pretty perfect Fathers Day morning project.

Here it is with the door closed, where you can see the special circumstances that come with having a cage in the cockpit.



And here it is with the door open.



All told, I shaved a little over 5 pounds off the car's total weight, which doesn't mean much -- except maybe that I can enjoy my Fathers Day dinner just a little bit more.

[impactbumper]

5lbs is 5lbs. Every single bit matters. I recently installed rs door panels and while doing it was thinking about an alternative material. This is an interesting but good budget solution. Kudos


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[911tracker85]

thanks for this idea. will keep the steel doors, but planning the RS door panels for my 930 build.

still debating on glass or lexan for the windows. removing PW and will fab a pull strap to raise/lower. I have seen this done a couple times.

still tearing it down, long way to go....

will be for DE/street. want to get as much weight off as reasonable, but again it will be mostly street driven. if I ever get it done, I won't want to do much DE time, but will just have to a couple times to really enjoy all the mods and performance in a reasonably safe environment.

I have always loved posts of you car.

[Taxi!]

Jack,

Two things. First, I recently replaced my power flag mirrors with aero mirrors and decided to forego the modifications necessary to make them power, too, since I'm the only person who drives the car. So I've left myself with an adjustment knob on the top of my driver's side door panel, and you've just shown me (possibly) how I can fab a new top piece to eliminate the knob and existing hole, so thanks. (I say "possibly" because I'm sure if it was something that took you a portion of two weeks to complete that means it'll take me the better part of two months.)

Secondly, in your ongoing search for more speed at the track, have you considered a more aerodynamic set of side mirrors? Or maybe totally eliminating the passenger side mirror? Unsure how many tenths that'd be worth, but couldn't hurt. I know the streetable aspect is important to you so you could remove the passenger side mirror when you get to Willow Springs and then re-install at the end of the day.

[Trackrash]

Jack, again you prove you are the DIY master. Really nice work. Makes my plywood and vinyl table cloth door panels look positively Mickey Mouse in comparison.

Are you running glass or plastic windows in the doors?

That shortened window crank is over the top.

[Jack Olsen]

Thanks, guys.

I have glass roll-ups, and I think Lexan is too big a sacrifice for a mixed-use car. I have Lexan front and rear quarters, and if I still had the glass, I'd switch back. The stuff doesn't age very well.

Taxi!, on those winter mornings when I'm going for a personal best, the flag mirrors get folded back for reduced drag. I suppose I could pull them -- but since I drive to the track, I'd have to both pull and reinstall them trackside. I also remove my wipers, partially roll up the side windows, and tape off the A-pillar portion of the drip rail on those days.

And the new door cap pieces were probably the quickest part of the job. I used snips to cut a length of aluminum, and then just made two by-hand bends over the side of a 2x4. The milled corner of the lumber meant the 'fold' wouldn't kink, but would keep enough of a radius to look like the originals. Then I used snips to trim off the ends and fold over where the things cap off. Those old caps seem crazy heavy now that I've done the same thing with aluminum.

[gduke2010]

Good job, especially, fabricating the door tops. They're tough to find. It took me months to find a quality door top and I paid big $$ for the drivers side. Once I ordered the top from a salvage dealer, I had took wait about a month for delivery. And wile waiting, I repaired and had the old one recovered. I reinstalled the old one. the one from the salvage supplier was mint. So, I'm saving it for when I restore the interior.

It would be a great product to manufacture and sell, since you've done such a great job fabricating the door tops especially, with weight saving aluminum. They go for as much as $500 each.

[Puma]

Great tip on the plastic and how to form the aluminum door tops. My car didn't come with several interior pieces and making them out of lightweight materials seems the best route.

Thanks!

P.S. As a Writer are you secretly correcting my grammar? Wait, don't answer that.

[Trackrash]

I have had plexi-glass for my rear three windows for over 30 years with no problems.

For auto crossing I switch my entire doors for stripped carbon fiber shells. I found it is much faster to switch the entire door than to remove or replace the glass and frames.

[em78911]

Nice! love what guys come up with for weight reduction.. well done Jack!

[froggert]

Any difference in noise?

[Jack Olsen]

Originally Posted by Trackrash

I have had plexi-glass for my rear three windows for over 30 years with no problems.

It could be that I've got crappy Lexan. My pieces have about 12 years on them. They're ready for replacement.

[Jack Olsen]

Originally Posted by froggert

Any difference in noise?

Not that I can detect.

[Kevin911sc]

Originally Posted by 911tracker85

thanks for this idea. will keep the steel doors, but planning the RS door panels for my 930 build.

still debating on glass or lexan for the windows. removing PW and will fab a pull strap to raise/lower. I have seen this done a couple times.

still tearing it down, long way to go....

will be for DE/street. want to get as much weight off as reasonable, but again it will be mostly street driven. if I ever get it done, I won't want to do much DE time, but will just have to a couple times to really enjoy all the mods and performance in a reasonably safe environment.

I have always loved posts of you car.

I have leather straps in my car....look cool but are a huge PITA, as they stretch when the humidity is high and leave you unable to fully close the windows. However much I love the look eventually ill be installing manual windows or making a new harness for the electric windows the prior owner hacked up.