Pelican Parts
Parts Catalog Accessories Catalog How To Articles Tech Forums
Call Pelican Parts at 888-280-7799
Shopping Cart Cart | Project List | Order Status | Help



Go Back   Pelican Parts Forums > Miscellaneous and Off Topic Forums > Paint, Bodywork & Detailing Forum


Reply
 
LinkBack Thread Tools Rate Thread
Author
Thread Post New Thread    Reply
Registered User
 
Join Date: Feb 2009
Location: Vasteras, Sweden/Pompano Beach, FL
Posts: 680
Paint cracking?

Hi,

It seems like my painter has a reoccuring problem with paint cracking 6-12 months after the pint job is completed. He had to partly re-paint my old -72 T, and now I found a crack on my other car as well.

I will try and find a pic of it, but basically it just crack from the metal and up. Like it is peeling in chunks of maybe a square inch or so, leaving just bare metal under.

Do anyone have an ida of what has gone wrong? I have seen his prep work, and it looks good to me, he just sands it to bare metal and start to build from there.

Anyone that recognize this and can point us in the right direction?


Regards,

Johan
__________________
-14 Cayenne S Diesel, DD
-92 964 C2 convertible, RS -92 look and feel😃
-73 T US MFI Targa, restored
-70 T Coupé Hot Rod, painted waiting for assembly
-72 T Coupé, US numbers matching under restoration
Old 10-13-2012, 12:15 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #1 (permalink)
dkbautosports.com
 
962porsche's Avatar
 
Join Date: Feb 2009
Location: branford ct
Posts: 3,316
it would be my guess he is not using a DTM type primer or he is not using a e type primer over the bare metal .
most primers will not stick to bare metals at all and in about a year they will delaminate .
it also could be he is laying on to much product or to much product at one time with out letting the products flash off .
Old 11-20-2012, 08:47 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #2 (permalink)
Registered User
 
golfbuddah's Avatar
 
Join Date: Apr 2009
Posts: 767
Garage
I too have cracking, but it is in the area where my flairs were put on, on the top. no other place on the car just where flairs connect to original fenders?????????????
Old 12-26-2013, 08:10 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #3 (permalink)
dkbautosports.com
 
962porsche's Avatar
 
Join Date: Feb 2009
Location: branford ct
Posts: 3,316
you will see cracks coming from were flares were add onto a car allot .
it some is because they are fiberglass but you will also see it with the steel ones as well .
there is a host of reasons for why you will see cracks showing up later on after they were installed .
with steel flares allot of the time its because they warped the crap out of the panel from welding then they used way to much body filler to make it straight .
it's not the size of the area that makes a lot of filler on a car it's how thick the filler is .
you will also see with steel flares that they will not have the weld completely along the seam of the two panels were they meet . if you have a little spot or more were the weld was missed . moisture will get up between the missed weld area and under the body filler and start to rust the metal . this will push up the body filler and crack it .
another reason is they did a over lap of the two panels when they installed the flares .
it makes for a easer install of the flares but you should not over lap seams of panels . they should be butt welded . what happens with butt welding on flares is the same thing you are left with a space between the two panel for moisture to leach into and again it gets under the filler and starts to rust and crack the body filler .
that's just a couple of reasons for steel to steel flares starting to show signs of cracking .

fiberglass flares you will hear allot of people saying they will always crack .
this is not true at all !
you can install them and if done right you will never see them crack and delaminate .
they have bonding adhesives that will bone the two (FG to steel ) and they work great .
with FG to metal bonding people will do many things wrong when installing them .
any one of them will lead to a problem with cracking and the flare wanting to delaminate off the steel .
the 1st thing most people do wrong when installing the flares is they leave the lip if FG were it has to bond to the steel way to thick .
you have to knife edge the edge of the FG flare down to paper thin right on the edge of the flare it's self were it lays on the steel . you only want to knife edge the top area of the flare so the bottom of it will sit flat on the steel .
to much over lap and it will delam to little and again it will delam too .
about 2" is best for the over lap of the two panels .
the reason for the knife edging is to cut down on the difference between the the way the two different materials will expand and contract . metal has a much higher expansion and contraction rate than FG does . that's way they tend to crack .
another reason is the way the two parts are prepped .
many people will take a grinder with 36 grit and have at it to the parts were they get bonded thinking more of a cutting grit will hold better .
a 60 grit is the cutting grit you want to use for the prepping of the two parts .
the reason why 36 is not good is the cut of the grit is just to big and the adhesive will not get all the way into the grinding scratch leaving micro air pockets .
other reason why FG will not last for many people is the bonding adhesive they picked to use was just the wrong product for there job . some adhesives will say they work for FG to steel bonding but this is not true . they may and do work for little parts like if you had to glue on a little tab but to bond a hole flare on they will fail . so pick a adhesive that is made more for the job at hand . we have tried a **** load of different bonding adhesives over the years and found the SEM to work best and last with out any problems .
people will also drill holes the put screws or pop rivets in to hold the two parts in place . DON'T do it !
you clamp the two until the adhesive cures .
if you leave the screws or rivets in the panel and try and fill over them your just adding some thing else to go wrong .
if you remove the screws or drill out the rivets once the adhesive is dry your again just adding some thing to go wrong because now you have little holes thru the parts you have to deal with .
over the years I have found the FG flare was installed right but the way they went about filling the seam was all wrong .
I have seen products used like allmetal body filler to FG mat or cloth and many other things used to fill the seams .
if you knife edge the FG flare before you install it you will not have a big lip to fill .
then you will only have to use a regular old plastic body filler and very little of it .
using things like duraglass and other FG based fillers is not the way to go either .
if the FG flare does not want to stick to steel because of the expansion and contraction difference between the two part then adding more FG from a FG based filler is only adding to the problem you may have .
I say all the time less is better with the uses of products .
again there are many reason for FG to crack and delam from steel but these are the main ones .
Old 12-27-2013, 06:09 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #4 (permalink)
Registered User
 
golfbuddah's Avatar
 
Join Date: Apr 2009
Posts: 767
Garage
Thanks mine are steel flares and fenders. The is an overlap i can see on the inside of the front fenders, I cannot tell if flares were completely welded or glued or spot welded. I did not do the initial body work. I quess the question is how do I fix it correctly, and how much will all that cost?
Frank
Old 12-27-2013, 06:29 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #5 (permalink)
dkbautosports.com
 
962porsche's Avatar
 
Join Date: Feb 2009
Location: branford ct
Posts: 3,316
again there are so many reason as to why flares will get cracks in them so with out seeing your in person there is no way to tell just what is going on with them .
so that makes it imposable to say just how much it will cost to repair them .
if they are over lapped then the right way to repair them is to cut the seam and butt weld them together redo the body work and repaint the panels .
not cheap because your doing the hole job over again !
you could go and grind out just the area's that have cracks and you maybe able to just spot repair them ? but the thing is by doing that is if you have one or two bad spots showing up now who's to say the other area's you don't repair right will start to show signs of cracking later . so you could just piss your money away but trying to spot repair them .
the thing many people that install flares over look is the under side of the panel .
they think because you don't see it you don't have to also make it look as finished at the top side .
like you side you can see where they over lapped the two panels .
it's not that you have to spread body filler on the under side of the panels but you have to do finish grinding and seal the welded seam E-prime the bare metal and make sure there is no way for moisture to leach it's self into the welded area .
Old 12-27-2013, 06:53 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #6 (permalink)
 
Registered User
 
golfbuddah's Avatar
 
Join Date: Apr 2009
Posts: 767
Garage
962 thanks for the input, am I better off buying a pair of fiberglass fenders for 900 buck and painting them?
Old 12-27-2013, 07:00 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #7 (permalink)
dkbautosports.com
 
962porsche's Avatar
 
Join Date: Feb 2009
Location: branford ct
Posts: 3,316
I can't see a point to do that ?
if you have steel flares on the car now I would just repair that you have if possible ?
steel flares are by far the best way to go but the cost is more along with weight .
if your needing bigger wheels and tires for a race car and also want as little weight added to the car you should go with FG .
but for that most of the time you just install them with QTR turn fasteners .
because of the fact if you aint rubbin you aint racing .

as it sits now if they did do a over lap on the panels .
you take a very thin cut off wheel and cut so the two pieces meet butted together .
you use the placement of how they are sitting if that is right and cut say 1/3 at a time and weld them together the right way . but doing that you will not change how they are sitting on the car . like if you just cut them off the car and then tried to weld them back on .
Old 12-27-2013, 11:54 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #8 (permalink)
Reply

Thread Tools
Rate This Thread
Rate This Thread:

 


All times are GMT -8. The time now is 08:34 PM.


 
Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2019, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2018 Pelican Parts, LLC - Posts may be archived for display on the Pelican Parts Website -    DMCA Registered Agent Contact Page
 

DTO Garage Plus vBulletin Plugins by Drive Thru Online, Inc.