|01-05-2011 10:04 PM|
|JPPadula||i've completed most of the repairs to the SMC using the recommended materials. Next step will be prime and paint. I've had to repair several areas of the underhood bracing. The top surface has been repaired and completely stripped with 80 grit and smoothed to 220, so I'm assuming epoxy or urethane primer surfacer should be fine right over the raw SMC. The underside still has most of the OEM paint. Sanding all of the nooks and crannies of the bracing would be really time consuming. Any shortcut to prep this area for primer?|
|11-28-2010 10:53 AM|
I could not find a link to the material we have at the shop but did find a link to even better material for your use. This cloth you can lay-out dry onto your hood, then wet in place, easier layout and no air bubbles. Can use with polyester, SMC or epoxy resin.
8 oz. x 8 strand fiberglass
They sell it by the yard AND it's 60" wide for a 1 piece fit-up.
Your resin should have a 'green window', after it sets up but before it's hardened, where you can recoat it with more resin to cover any fabric pattern from showing, by-passing the gelcoating, saves time & materials.
Have fun with it.
|11-27-2010 08:22 PM|
|JPPadula||I would definitely fix the obvious and most serious damage first. But the concern and the reason I was thinking of covering the whole surface of the hood with one continuous layer of material is that there were numerous stress cracks in the painted surface well outside of the obviously damaged areas. A few of these areas can be spotted in the stripped SMC, but others show absolutely no sign of damage to the substrate. I believe that if I dont cover the entire surface of the part in cloth/matt, that these invisible areas of damage will work there way back through the paint. I'm interested in this "Veiling" material. Did I understand you correctly when you said to put the matt side down towards the repair? I would have assumed that the random surface of the matt would go towards the paint with the stronger cloth on the substrate.|
|11-26-2010 02:29 AM|
The primer is not going straight on the "glass" and the repair is kept small as possible..
I thought you were just going to spot repair the minor damage on the corner top&bottom and would have left the good paint alone except a sand with 180/320 for a primer surfacer. To put cloth on the entire hood without addressing the "local" damage first is asking to much in this reporters opinion
|11-25-2010 10:41 PM|
"This leads to another question. I've always heard that you shouldnt use fiberglass cloth under finish coats due to the texture of the cloth printing through after time. Is there a special primer that will hold the texture down? I'm under the impression that polyester primers (what I was planning on using to hold down the repairs)"
If you go to a boat repair supply house, ask them for a fiberglass cloth/matting called 'veiling', a super fine cloth on one side, a fine matting on the reverse, works perfectly for what you are doing to your hood. It's NOT cheap but the labor savings and finished product more than make-up for the cost.
Get a piece large enough to cover the hood + overhang on 4 sides.
Wet out the hood and place the piece (matting down) starting in the center and work out from there. The dry matting will release any air bubbles thru itself, it's also MUCH cleaner and easier this way
Re-wet the matting from the center out.
Real marine gel-coat works much better than any polyester filler/primer can hope for. Ask for and follow the instructions from the supplier.
Have fun with it.
|11-25-2010 09:11 PM|
Your pictures of your hood are what prompted me to post the link of a project like yours I did in the past with the same smc typ..
If you do the repair in stages you'll have a easier time being in control, yes shallow the repair area add in some cloth and top/finish with a 2 part putty then your primer will behave
|11-25-2010 05:17 PM|
|JPPadula||I would be all for Epoxy resin as long as I knew it would adhere to the SMC. I noticed in the last picture posted that fiberglass cloth was being used. Cloth is necessary when using epoxy because the binder in matt doesnt disolve properly with polyester resin. This leads to another question. I've always heard that you shouldnt use fiberglass cloth under finish coats due to the texture of the cloth printing through after time. Is there a special primer that will hold the texture down? I'm under the impression that polyester primers (what I was planning on using to hold down the repairs) cant be used over epoxy surfaces.|
|11-24-2010 04:07 PM|
|11-24-2010 03:47 PM|
|Chris Kemp||Fiber glass is great and if used like Brian has stated you will not have a problem. But just like he said, you have to thin down the damaged areas and that means the hairline cracks also. If there was cracks in the paint then the hood is cracked there too. The only way to repair it so it will not come back is to thin down the cracked areas and then fill in those thinned down areas with a repair material. I have had great success using a product called MarineTex. It is a marine epoxy that has been around along time. I have used it from start to finish on the same type of repair that you are doing. It will not shrink or show ghost lines down the road after the sun has baked on it for a while. Not to put down Brian's method because it will work great but IMO MarineTex works on smc better then regular fiber glass.|
|11-24-2010 03:31 PM|
Use a one to one type Epoxy resin for "adding" or repairs to broken fiber glass or smc, not regular fiberglass building resin.
Heres a common fiber repair project where existing material is left in place and the epoxy resin is allowed to "drool" into the fractures..
|11-23-2010 07:53 PM|
Unless someone else comes up with some other ideas if it's cracked it needs to be thinned down (sanded down) and mat and resin put over it to reinforce it.
|11-23-2010 06:39 PM|
Ok so I stripped this hood this weekend. 80grit on the DA down to the SMC. As I feared, there are stress cracks in multiple areas. The worst of them I plan on repairing by thinning the SMC in an area around the damage and laying 2 layers of 1.5oz matt using the SMC resin over the surface as a patch, then filling with the recommended fibertech filler.
What is concerning me however is that there were many more stress cracks in the painted surface than show in the SMC now that its stripped. Is it possible that the paint cracked but the SMC surface didnt? Or, might there be invisible microcracks in the SMC that will telegraph back through the paint as it cures? A possible solution that came to me is possibly repairing the broken areas and then laying one continuous layer of 1.5oz matt over the entire hood to hold down any tiny cracks. I've been told that the SMC resin does not wet out the matt well, so I'm concerned that laying a large piece of matt might be impossible with that material (not to metion the 45$ a quart price) Would it be feasable to use standard polyester resin if I'm laminating the whole hood? Input?
|10-24-2010 11:51 PM|
|JPPadula||Thanks! I'll post when I'm done messing it up...errr repairing it.|
|10-24-2010 11:44 PM|
Yes, JUST to level it off and cover up your mat.
|10-24-2010 11:40 PM|
|JPPadula||I went to Evercoats site to check out the fibertech you mentioned and they are showing it as a repair compound that stands alone without matt, Are you suggesting to use it over the SMC resin/matt repair as a filler?|
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