Need tips for vinyl-covered fiberglass interior trim parts

[Moderator]

I'm halfway into making a lightweight two-piece transmission tunnel cover. I've already made the fiberglass parts (shown below) and I've also purchased some good quality stretchable vinyl to cover them. My idea is to use spray-can "headliner adhesive" to secure the vinyl, and to supplement that bond with saddle-stitching through pre-drilled holes.  If this project continues going well, I might make more trim parts. (Featherweight door panels with molded-in armrests, perhaps?)  

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Goals for this project:  (1) total weight under two pounds, (2) material cost under $100, (3) parts should be easily removable / re-installable without tools. Reducing cockpit noise and heat are perceived as goals of this project, but I haven't quantified any expectations.

Here's where I've hit a snag. I'm not sure what sort of padding, if any, to use between fiberglass and vinyl. Landau pad? Polyfoam? Batting? Is it better without padding? Also, there are many bumps and depressions in my fiberglass parts - most of them transferred over from my tunnel's irregular shape - and I'm not sure how best to fill and level them. Bondo? Just padding?

Got any ideas? Tips? Product recommendations?

[rficalora]

If you the way custom interiors are done, they just use bondo to smooth the parts.

I'll be interested to hear what folks say about attaching the vinyl.  I've not had much luck with either 3M 90 or contact cement holding a bond.  Once the car sits in the heat for a while the vinyl pulls loose on inside corners especially.

It does seem to stick better to the bondo than the fiberglass for what that's worth.

[HealeyRick]

I'd probably use jute padding under the carpeting just to smooth out the bumps and add a bit of substance.  I really like Moss Motors upholstery adhesive:  part # 221-560  Stuff comes in a non-aerosol can and can either be brushed or sprayed and seems to stick better than the products you get in the big box stores.  Plus it has a real strong odor, which is to me the hallmark of any worthwhile chemical product from carburetor cleaner to paint stripper.  If it smells like it could kill you, it will probably work.  Even better is if it's been taken off the market by some safety regulation.  That's the really good stuff!  Moss has some tips for using their adhesive here:  https://www.mossmotors.com/forum/forums/thread/9861.aspx

[Moderator]

Cool!

From reading-up here and elsewhere, I've been talked out of messing with aerosol cans or anything from the big box stores. I'll try to purchase Weldwood HHR (high heat rated) contact cement locally today to save shipping cost. It's specifically made for use on automotive vinyl... roofs, headliners, and such.

Landau pad (closed-cell foam that comes in sheet form, in various thicknesses) is described as "sculptable" and "sandable" - but I'm not exactly sure what that means. It's inexpensive. I guess I'll get some and play with it.

[mgb260]

I've seen the multicolored foam used under house carpet used in upholstery also.

[Moderator]

I stopped by my friendly local upholstery shop - "S&S" in Longmont - late this afternoon and they very kindly agreed to sell me one quart of high temp contact cement for $10. That's a great deal for me because DAP only offers one and five gallon cans. One gallon cans sell online for ~$29 plus ~$19 shipping. S&S also sold me a leftover piece of 1/8" thick landau padding!

[Preform Resources]

Well I think you made the right move  Curtis ,at least you know that is what the pros use, are you gonna post some pics ?
Dave

[rficalora]

Curtis - do you have to spray it or can you brush/roll it on?

[Moderator]

S&S says all three methods work fine. They spray, but sometimes use a chip brush when they just need to hit a small area.

[Jim Stabe]

I like your idea for covering the tunnel. How did you make the fiberglass piece? Did you mold directly over the tunnel with some sort of mold release or form it over a tool of some sort?

[Moderator]

I put cheap, thin (~1/16") craft foam over the tunnel and then covered the foam with aluminum-foil duct tape. That combination eliminated the biggest bumps and hollows. I sprayed mold release over the aluminum surface. Laid-up the front part one day and the back part the next. The parts popped off the "mold" very easily. Since the foam and aluminum foil are intact, I've left them for the time being. I might replace them with better insulation.

My brother was visiting from out-of-state and I wanted to take him for a test ride so I put the seats back in right away. In fact, I've been driving the car a lot, and I think I can still smell plastic fumes when it's hot. Maybe I should let those finish off-gassing before I spread contact cement...

[Moderator]

I decided to test the proposed technique on an old scrap of fiberglass (~4" by ~2.5").

This first pic shows the scrap, with 1/8" foam padding glued to it. On the lefthand side of the pic you may be able to tell where I sanded on the foam to produce a gradual taper. You can also see one row of holes I pre-drilled through the fiberglass. (There's another row hidden under the foam.) That unpadded 1" wide area replicates the section of the front transmission tunnel which will be overlapped by the rear transmission cover.
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This second pic shows the stitching. The near row of stitches are on 1/4" inch centers and the farther row are on 5/16" centers. (I think I prefer the smaller stitches.) You can see that the stitches recess into the padding.
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Incidentally, this kind of stitching is called "saddle stitiching" but I think a more descriptive term is "two needle" stitching. If you were to flip the part over, the stitches on the back would look pretty much the same as the front. I like the results, but I can see this is going to get very tedious. It will help next time to drill slightly larger holes; my needles were binding in the 1/16" holes.  Also, more thread was required than I expected.

[MGBV8]

Yep, 1/4" looks best.

[rficalora]

I never would have thought of stitching through the fiberglass... may steal that idea on my radio/ac control console... especially if I can figure out how to do baseball type stiching that looks right on the piece.

Where's the stitchng going to go on your trans tunnel?

[Moderator]

I love the look of baseball stitching on upholstery.

This sketch shows what I have in mind, at least for the front half:
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I'm hoping the 4-way-stretch vinyl will let me do this job without sewn seams, but I'm not certain it will stretch that far.

[rficalora]

No doubt it'll stretch that far.  Question will be whether the glue is strong enough to keep it in place in summer heat.  What happened to me was in the heat the vinyl shrunk back some and pulled away from concave areas (inside corners in my case).  Watching to see how well the glue you got holds.

[Grant70B]

Curtis

Nice idea for the transmission tunnel cover.  Where I work we will make a plug out of medium density hardboard (MDO) of varying thickness.  Then layup a quick thin mold, to layup your part in.  Use should have a nice smooth part or one that could be easily sanded smooth.  I think I will use your upholstery ideas to create something.  One of the main thinks I like about these forums is the great ideas that you fine.

[Moderator]

Making slow, prodding progress...

I did end up smearing some Evercoat "Lite Weight" body filler on the fiberglass parts. I tried to go very minimal with that though, certainly less than an eighth of an inch thick anywhere and also just working the area from the front edge of the seats forward to the plane of the dashboard. In the main, I'm counting on landau padding to blend out irregularities.  Then I laid out a hole pattern and started drilling for stitches. Over a thousand stitches in total! I'm sure that's absurd overkill, but I really don't want the vinyl to come loose.

Then I applied the landau pad foam. I did the rearward "driveshaft" tunnel cover first, and I was very pleased with my work until I remembered that I'd intended to leave padding off of the area around the parking brake lever. Clearance there is so very tight, so I went back and sanded away padding to ensure there's clearance for vinyl. The forward "transmission" tunnel gave me more of a problem. My plan was to glue one side, then the top, and then the third side all from one piece of foam. Unfortunately, the foam didn't stretch quite right, so I ended up having to cut it into three pieces. You can see where the splices ended up in the second photo, below.

I've really enjoyed this project to this point. Industrial grade contact cement is a joy to work with. However, I'm very apprehensive about stretching the vinyl. It will certainly require extra hands, and I'm not sure exactly how many. And extra hands come with extra elbows... it seems to me that an upholstery shop needs to have three or four workers minimum and they need to be used to working as a team together.

Driveshaft tunnel cover:
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Transmission tunnel cover:
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[MGBV8]

Vinyl? That is looking so nice, I would be thinking Connolly Leather!  

[Jim Stabe]

That's really nice. I have pretty much the same shape to deal with as you so I'm paying close attention to your project.

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[63BlueMGB]

I finally made it around to thumbing through all the sub-topics and was suprised to see somebody else using this stitch, I used that stitching to awhile ago to solve a problem with some of my interior pieces that I have been making when I havent been able to get out side and work on my car. My problem was the spray adhesive wasnt holding my vinyl to my covers and the design I layed agaist it and everytime it sat for awhile it would pull away flat plus the vinyl I bought was to thick for my application so I came up with a solution to my problem instead of starting over and making new pieces. This stitch can be used to solve multiple problems.

The Baseball stitch can be used as well but it is a little more time consuming, and IMO it is better used when sewing to pieces of material together so you get a better seem and looks alot cleaner
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[Moderator]

Thanks guys!  I'm at my mother-in-law's for the weekend but I stretched vinyl over the driveshaft tunnel before I left home, and then I brought the part along so I could do the stitching here. Here's how it turned out:

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I'm generally pleased with the results, but they're far from perfect. I need to improve my techniques. Here are some notes:

Vinyl soaks up a lot more contact cement than the (closed cell foam) padding. If you're applying the adhesive with a brush, it's hard to work quickly and hard to get an even coating. Then, with some of the applied adhesive a little too dry and some of it a little to wet, when you try to apply the vinyl to your part, getting a smooth application is even trickier than it ought to be. A heat gun helps with rushing an area to the dry-enough stage. If adhesive gets too dry, you have to carefully apply just a little more. I ended up using up my quart of cement, so I'll have to buy more. I'm also thinking of investing in a spray gun for the transmission tunnel (and any future parts.)  So, I didn't end up with as even a stretch as I wanted and there are one or two small wrinkles in the vinyl, but not too bad.

In the small but deeply concave areas on both sides of the parking brake lever, I added stitches right away because I was concerned the contact cement might pull loose. Generally though, I think the vinyl looked "tighter" an hour after application than it did right away. The padding feels pretty luxurious.

I cut some of my darts too deeply. I need to be more careful next time. Maybe I should punch round holes somehow and just snip up to them.

You can see in the photos that I have a LOT of stitches on this part. My theory was that the stitches should hold the vinyl tight over the whole part even if the contact cement were to totally fail sometime in the future. Two needles passed through each of the 500 holes I pre-drilled in the fiberglass, so by my count that's 1000 stitches. That said, the stitching went remarkably quickly. You can't put a stitch out of line or in the wrong place if the wholes are drilled in straight rows. Incidentally, I drilled 5/64" holes on 5/16" centers over the hole part. On my test piece I had drilled 1/16" holes, but they were too tight for comfortable hand stitching with the needles I had selected. In retrospect, I'm really glad I decided to stick to one hole spacing everywhere because it helped me find the holes and establish a rhythm. Oh, BTW, I really really like the pre-waxed nylon thread I got from Tandy for this project.    

Nick, I'm not certain if we're on the same page about stitching or not. I'm using thicker thread anyhow, so that gives a somewhat different appearance. As for the stitch... I used to one shown on the bottom of this sketch:   http://4.bp.blogspot.com/-Wz89R7uhajY/TrFjs8irYtI/AAAAAAAAAxQ/JCU03TJ_Egk/s1600/Saddle+stitch.jpg

[MGBV8]

Wow. Your spartan interior just got a whole lot fancier.

[Grant70B]

Curtis

That really looks good, should be a nice addition to your cars interior.

[Preform Resources]

Curtis, looking very good , I think everyone will be learning something from your experience.
Dave