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Posted by: Series9 Mar 9 2016, 04:26 PM

Comments are now welcome. If you find any errors, let me know.




To start, I want to say that I'm a huge fan of Mark and 914Rubber. He has done a huge amount for our community and ANY criticism you see is strictly constructive. (There are only a few).

Next, this is a complicated task, but one that can be completed by a novice who is willing to pay attention to the details. However, any mistakes will be punished with a phone call to Oregon to order replacement vinyl.

As a Porsche professional, I've become something of a "jack of all trades". Upholstery is no exception, but it's still not something I do here every day. I am a licensed parachute rigger, so my knowledge of fabrics and sewing may have contributed to my build.

The reality: Having not done this before, it took me 17 hours. I built this for a customer who has paid me for a ground-up restore on a rust bucket (that is now beautiful), and it had to be right the first time.

I created this thread because there was an absence of instructions for something that differed significantly from the factory version. The primary problem: you can't use a staple gun. Think about that for a moment. Go to any upholstery shop and take all the staple guns. What do you think those professionals will say to you?

So, with those caveats in place, I present you with a very detailed guide to MY assembly of this back pad.

The overwhelming theme here will concentrated around the fact that, since we are dealing with fiberglass and staples can't be used, we have to find alternative methods of attachment in areas that have: High stress or any "pull force". Imagine "pull force" as a 90* pull against tape placed on a table. We all know that tape is strong if it's wrapped around a corner (becomes shear force), but it's very easy to remove if you pull it back perpendicular to the mated surface.

You can't use contact cement in a 90* "pull" arrangement. At least, you shouldn't if you want it to last.


Okay. Congratulations, you completed the introduction.

Posted by: Series9 Mar 9 2016, 04:37 PM

In the beginning, you will be presented with three pieces of fiberglass and three pieces of sewn vinyl.

We all know the nightmares of fiberglass, but I will say that these fit very well. I only made two small mods to the center.

You MUST have the foam from a donor back pad. Everything else can be fabricated, but without the foam, you are dead in the water.


(Note the hole in the foam for the engine decklid pull and the notch in the fiberglass for the parking brake for right-hand-drive)


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Posted by: Series9 Mar 9 2016, 04:47 PM

Next: You will need these Z tabs. If you have a full donor pad, no problem, but I didn't.

I made some out of stacked aluminum. You will find it very difficult to bend such a small double without a die.

Then, you will have to scribe the correct location on the fiberglass. I had a back pad here, so I overlaid the panel and drew the location with a Sharpie.



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Posted by: Series9 Mar 9 2016, 04:49 PM

More of the tabs:




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Posted by: Series9 Mar 9 2016, 04:54 PM

At this point, you should immediately realize that your fasteners for the tabs are going to create problems for the smooth application of vinyl on the interior side. So, grind down that side and do some body work. Epoxy to hold the nuts and Bondo to level the surface.







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Posted by: Series9 Mar 9 2016, 04:55 PM

Bondo:




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Posted by: Series9 Mar 9 2016, 04:59 PM

Test fit.

I put some shiny new screws in the correct location to help me find the correct location to drill the holes for the bottom screws. If they contrast, you can see them through the fiberglass.




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Posted by: Series9 Mar 9 2016, 05:06 PM

Do the same on both sides and mount them to the car individually.

Once each side is mounted to your satisfaction, put the center in place and see if you need any mods.

For this one, I decided to take 3/8" off the bottom in order to get it to sit down correctly on the passenger side. I used self-tapping screws with my drill and a 1/4" socket to drive them in.

Once you do this correctly, you should have a back pad base that is custom fit to your 914.


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Posted by: Series9 Mar 9 2016, 05:12 PM

Next, test fit the foam and draw an outline on the fiberglass for the two outers:




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Posted by: Series9 Mar 9 2016, 05:19 PM

LISTEN CAREFULLY!

There are certain points that MUST MATCH between the vinyl and the fiberglass. To ignore these points will cause the failure of your project.

Understand?

Okay.

Get your contact cement and glue down the contour of THIS SEAM first. You must start here and do this correctly. If you don't...




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Posted by: Series9 Mar 9 2016, 05:21 PM

The bigger picture on that:




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Posted by: Series9 Mar 9 2016, 05:27 PM

Now, remember when I said we can't use contact cement in a 90* pull?

The seam you just secured was only secured temporarily. It has to be strengthened, so we can pull (hard) on it later. Since we can't use staples, we have to figure out another way.

The first picture is a remnant of the factory staple-based reinforcement. The next is an aluminum strip that I'm going to use to perform the same task, but much more strongly.

I just put that 1/16"x1/2" strip in the drill press and punched a bunch of holes.


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Posted by: Series9 Mar 9 2016, 05:33 PM

THIS REINFORCEMENT OF THE SEAM MUST BE ACCOMPLISHED, OR YOUR BUILD WILL EVENTUALLY FAIL.


Cut the aluminum and screw until you have that seam secured. Use a soldering iron, or similar, to make the holes in the vinyl before you put screws in. This will save you from having the fabric attempt to roll up around the screw.


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Posted by: Series9 Mar 9 2016, 05:34 PM

And:




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Posted by: Series9 Mar 9 2016, 05:42 PM

Okay. Now we shove the foam in there and have a test fit.

Note the location of the seam. That will come up in the next posts.


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Posted by: Series9 Mar 9 2016, 05:53 PM

It gets a little complicated here.

The factory pulled back the median seam on the exterior bolsters and attached those pulls to the back pad on the back.

I debated whether this was necessary, but decided to try.

The first picture is a factory back pad.

The next few are my attempt to do the same with stainless safety wire:




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Posted by: Series9 Mar 9 2016, 05:54 PM

And:




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Posted by: Series9 Mar 9 2016, 05:58 PM

As you can clearly see, I had to cut a new slit in the foam. Don't put that on Mark or me. The foam relaxed and that's where the seam ended.

Turns out, once I pulled everything tight, it all had to move one space over, so now there are three:


(again, note the engine pull hole on the passenger side foam)


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Posted by: Series9 Mar 9 2016, 06:04 PM

Here's the back and the front after a test tensioning:


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Posted by: Series9 Mar 9 2016, 06:10 PM

Then, tension the vinyl around the pad.

I chose to do it with safety wire poked through the vinyl and then wrapped around the (later to be cut off) screws from the tension seam.

This way, I could adjust tension and leave it to sit for a couple of days.


On the second picture, please note that I have folded the vinyl under the end of the "tension strip". That will come in to play later.


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Posted by: Series9 Mar 9 2016, 06:20 PM

And then (said in an Asian voice from "Dude, where's my car"):

We move on to gluing down the field.

Note the texture of the fiberglass that translates to the vinyl back pad behind the seats.

This was an unknown when I started the project. The smooth side of the fiberglass support pieces is on the back, not the front.

While this probably provides more adhesion for the vinyl, some may not like the aesthetic of the blown in fiberglass.

Of course, next time I could spend another few hours with a DA sander smoothing everything out....




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Posted by: Series9 Mar 9 2016, 06:31 PM

Remember (again) when we talked about contact cement and adhesion?

Here are pictures of the field on the passenger backer.

The vinyl has to be pushed into the backer and that causes tension. Well, it didn't want to stay, so, leave for 24hrs...


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Posted by: Series9 Mar 9 2016, 06:38 PM

The next four finish up the passenger side.

Note the cut-out for the parking brake on the passenger side does not apply and the screws for the tension strip have been cut off.

Be very carful when cutting the screw remnants. They are very hot and will go right through vinyl, if you let one get away to the front side.


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Posted by: Series9 Mar 9 2016, 06:43 PM

Remember the pulls on the median seam on the outside bolsters?

I finished it like this. Those pulls only require a VERY SMALL AMOUNT OF TENSION.

Pull lightly and bend the safety wire over. It'll hold there. Then, I found some screws to put in the holes that will hold the wire (again, under very light tension).



Then, get out the soldering iron (or similar) again and punch the holes where this part will screw to the mid section. Be very careful! A slip up at this point will cause a phone call to Oregon!


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Posted by: Series9 Mar 9 2016, 06:50 PM

Questions about adhesion?

Pull is obvious and even shear has limits:




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Posted by: Series9 Mar 9 2016, 08:11 PM

On to the center section.

It's obvious where the interior light should be located, but it's not that simple.

You have to cut out the obvious hole, and then:

In the original arrangement, the light was secured by two thin tabs. Those tabs do not exist on this assembly. Because this "stack-up" is too thick for the original light to simply snap in, I attempted to bevel the fiberglass.

My attempt worked before the vinyl was overlaid.




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Posted by: Series9 Mar 10 2016, 08:18 AM

Buy/find some Tinnerman nuts and ad them to the center section.





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Posted by: Series9 Mar 10 2016, 08:20 AM

Get out the 3M Super 90 and attach the foam.


Then, go for a test fit on the vinyl:






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Posted by: Series9 Mar 10 2016, 08:25 AM

Two bits of funkiness on the center vinyl.

The vinyl simply terminates at the bottom of the foam.

There is no flap for either attachment to the fiberglass or to cover the bottom.

I just covered the bottom with felt, but the vinyl is not actually attached across the front.


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Posted by: Series9 Mar 10 2016, 08:35 AM

This is a scary cut. Be very careful.




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Posted by: Series9 Mar 10 2016, 08:38 AM

There is no way, that I can see to use anything but contact cement here.

The light is basically friction fit. It won't snap in due to the thickness.




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Posted by: Series9 Mar 10 2016, 08:44 AM

The center section could be mostly attached with contact cement, but I decided 4 points needed more:




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Posted by: Series9 Mar 10 2016, 08:48 AM

Get out the hot knife again and poke the holes for the Tinnerman nuts:




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Posted by: Series9 Mar 10 2016, 08:51 AM

Get some screws that are just long enough. You don't want to flip this over and have a screw poking out of the center vinyl.




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Posted by: Series9 Mar 10 2016, 08:53 AM

That's it!

Repeat the steps for the driver's side and you're done.

Whew!

(Yes, I am aware that I have to do something to obfuscate the white sealant on the back window)



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Posted by: BeatNavy Mar 10 2016, 10:01 AM

Someone's gotta break the ice and comment

Excellent write-up, Joe. Thanks for the great details and pictures. This will be a project for me at some point in the future.

Posted by: Ferg Mar 10 2016, 11:43 AM

Wow, nice job.

Appreciate the time it took to do the write up!

Posted by: 02loftsmoor Mar 10 2016, 11:56 AM

If you don't know how to do it I did, it turned this into a PDF. I'll email it to you if you want it. little easier to use. Series9 great work
contact me at
wesleyallangreen@gmail.com

Posted by: beech4rd Mar 10 2016, 12:06 PM

Thank you very much for this. Very clear instructions. Fantastic!

Posted by: Tom_T Mar 10 2016, 12:36 PM

Kudos Joe & Thanx!

BTW folks - Joe's "how to" here will essentially also work for any of the 914 interior kits, as well as with "roll stock" material if you use the old stuff as a pattern to make up & sew the kit parts (much more work).

Also if you use a local upholstery shop not too familiar with 914s, you can send them the link to this topic for guidance.


Tom
///////

Posted by: Series9 Mar 10 2016, 01:38 PM

QUOTE(02loftsmoor @ Mar 10 2016, 12:56 PM)

Posted by: whitetwinturbo Mar 10 2016, 04:43 PM

Posted by: Kansas 914 Mar 10 2016, 06:58 PM

Well done Joe - thanks for doing this - we all benefit - cheers!

Posted by: bigkensteele Mar 10 2016, 07:29 PM

I had purchased Mark's kit a while back and have been waiting for someone to post a thread like this, so thanks Joe! Great detail and very informative.

Just out of curiosity, what would happen if I tried to shoot a staple into fiberglass? I was planning on using staples. Will they shatter the FG or just not hold well? I have also purchased the FG door panel kit, and I was thinking about staples for that too.