how do I fix this? (fiberglass)
 

So I've got this 968 rear spoiler that I've had for years and it's time I do something with it. Problem is, all 4 mounting holes on the thing look like this.

It's factory Porsche so it isn't really fiberglass but it's not really plastic either so I don't know how to proceed or what products to use. Not to mention the holes being awkward and 2 of the 4 are not easily accessible from the back side.

So how does one go about fixing these?

http://forums.pelicanparts.com/uploa...1528752696.jpg

http://forums.pelicanparts.com/uploa...1528752696.jpg

I think fiber glass is your best bet .

I would glass in some nice thick SS washers for each hole.

Since these are such small holes (total damage area of around an inch) do I use mat and resin or would just thickened epoxy work? And if mat and epoxy, would I be able to grind out the holes to a gradual taper and use graduated circles until it's level with the surrounding area? I'm just worried about keeping the area level since it sits against glass and don't want any gaps there.

No expert but go find a fiberglass repair kit. Comes with cloth fiber and a 2 part resin mixture. It don't have to be the same material Porsche used because it will stick to it. You can use bondo on the finished side. That's probably your best bet.

Chopped glass to fill with 3 oz woven mat covering a larger area

surface prep is everything

I would use fiberglass with epoxy not polyester resin.

Epoxy resin is more expensive than than polyester but it's stronger and resists higher temperatures.

Paging Tim Hancock! Look at the outstanding work he did with his soft floor on his boat.

Dave

It's all about contact area with the old fiberglass. So you'll need to grind the gelcoat off and provide more area for the new f/g to "bite" onto the old f/g.

Marine-Tex putty?

Try Marine Tex epoxy putty and milled fibers mixed together.
Get some plastic lined form to get the shape you want as it sets up. Then shape and smooth before it gets totally hard. Keep some of the mix separate to determine the cure rate. Easier to work after it sets up but not totally cured.

Cheers Richard

Hey Eric, great minds think alike. Crossed in the typing.

epoxy is stronger and sticks better then polyester
but common f/g mat has sticky stuff [ sizing] that is not solvent in epoxy only polyester
so you need special sizing free mat for epoxy work to get full strength

Marine-Tex putty should work

Never knew this about mat not working with epoxy. Glad to know that!

Now this Marine-Tex...is it as simple as just pressing it onto the tabs and shaping it from there? After grinding to solid material on the spoiler first of course? That seems much easier (and cleaner) than using glass and resin. What about strength of it? I just don't want it to turn brittle or not work and then have to redo it. That pay once, cry once thing...:D

Marine Tex is not like playdoh, it's gooy, sticky, tends to sag out of where you want it to be. Does not smooth out easily when working it. You need to mask around where you want it to be, to keep it off of surrounding surfaces

Apply generously using a small section of plastic squeegee, then use plastic form over it to creat a fair surface. Multiple applications may be needed to fill voids. Wear gloves as it will stick every where it touches.

For max strength, a couple of layers of epoxy resin wetted out cloth, laid over each side and onto the neighboring surfaces. once the marine Tex built up surface is level with the surrounding surfaces. Then scuff the surrounding surfaces for adhesion. Then mask the edges , and lay on the cloth wetted out with a brush, then smoothed with squeegee.
Trim edges with razor blade after the resin gels but before it cures.

This will add strength to the repair, but will add to thickness of the piece.
If thickness is critical, you may get away with just the marine Tex built up to the existing surface level.

The marine Tex will fill and adhear to that existing broken area with little prep, if it is clean.

Sorry if this is confusing, it's almost easier to do than to discribed.
Feel free to PM me. We can talk it thru on the phone .

Cheers Richard

bondo glass. or something similar.

it is kind of like bondo but it has fiberglass matt in it already.
don't let the name turn you off, it is VERY strong and hard.

don't know if it is still called bondo glass or not.

fill it in completely and then redrill the hole.

I would probably grind away a bigger area about half way through

Without actually being able to examine all of it, my best guess is that I would primarily sand the back side back a bit and smooth out the rough edges somewhat then cut up a bunch of small to progressively larger pieces of fiberglass cloth and lay that all up with epoxy. I might even try wax paper on the car and position the uncured affair in place with clamps/straps/tape etc. to end up with the inside surface perfectly potted/matched to the car. After cure, I would then simply sand the outside to shape, redrill the holes and spray the whole thing with bumper black spray paint.

This is what I was originally thinking. I may try this on one of the holes and see how it goes. If it's too much of a hassle I'll get some Marine-Tex and try that.

The big problem is the thickness of the piece can't be any thicker than what it already is. It gets bolted against the glass and then has a thin trim piece that goes over it to cover the bolt holes so any extra material will cause the trim to not sit flush which then leaves the weatherstripping away from the glass which then lets in water, etc, etc, etc.

Thanks everyone for the replies and ideas. I've got a few options now to choose from and hopefully I can get this thing fixed once and for all.

ps...thank you to the mod that fixed my flububber in the title. :cool:

I kind of had a similar type repair involving the bow eye on my boat. The holes were all wallowed out and the outside gel coat was chipped up. I rough sanded the back side then I did the progressive build up on the back side with a whole bunch of layers of woven fiberglass cloth and then made a stainless steel cover for the front. I tightly taped the stainless steel piece in place to contain the epoxy then flooded the back side with epoxy and started packing/laying in a bunch of the fiberglass. Once it all cured, I then removed the tape and redrilled the holes and it came out very nice and strong.

You might be able to tape the front side to create a temporary dam while you fill in the back. Once cured, you might not have much sanding to do on the front. Any excess on the edges is easy to grind/sand off once cured. Here are some pics to maybe give you some ideas. (do not have a before pic of front side or of the tape job that held the stainless piece in place)

Wallowed out back side
http://forums.pelicanparts.com/uploa...1528809874.jpg

Multiple layers of glass and epoxy
http://forums.pelicanparts.com/uploa...1528809874.jpg

After redrilling holes
http://forums.pelicanparts.com/uploa...1528809874.jpg

Front side after removing tape dam and before redrilling holes
http://forums.pelicanparts.com/uploa...1528809874.jpg

Finished product
http://forums.pelicanparts.com/uploa...1528809874.jpg

thickness control with a bolt and two bits of Formica drilled for the bolt
put a good smooth coat of wax on the Formica
fill the broken hole with marinetex and use the bolt /nut to hold the Formica flat and tight
that will save a bit of sanding and no need to redrill the holes