guide coat technique
Thread Starter
Safety Car
Joined: May 2005
Posts: 4,176
Likes: 7
From: Jennings LA
guide coat technique
I am block sandindg my 71 to get it straight, someone in the past used a DA sander and it has a few ripples in it. I sprayed a guide coat after I sanded the primer for a while, blocked it with a 7 inch block and some 220 and it all came off. you would assume it to be straight but I can still feel a few ripples or low spots when I run my hand over it. is there any special technique to using a guide coat?
Burning Brakes
Joined: Feb 2005
Posts: 1,235
Likes: 0
From: Mesa AZ
i use 400 grit wetsanding on the guide coat and use circular motions . if the ripples are too big then they won't come out with just filling them in with primer. and remember that these cars had ripples in the fiberglass from the factory
Le Mans Master
Joined: Jul 2005
Posts: 5,752
Likes: 4
From: Austin Texas
There are different size and firmness blocks available to the industry. Choose the firm, longer blocks for the flatter surfaces like decks, doors and hoods. Smaller and softer blocks are to be used elsewhere. It's all about trial and error. Never use the sides or edges of the block, that defeats the purpose. 
Melting Slicks
Joined: Jan 2005
Posts: 3,347
Likes: 9
From: Salinas Ca.
It's my understading (and what I do) is right after shooting the primer I then apply the guide coat. Seems to me, sanding then applying the guide coat and then sanding again may let you sand right through some low points without even knowing it... Just my 02...
Instructor
Joined: Apr 2005
Posts: 226
Likes: 0
From: lakewood (tacoma/seattle) washington
someone once told me "if you can feel it you will see it" I have started using dry guide coat when dry sanding . At first I didnt like it but now I like it. good luck and keep at it.
Pro
Joined: Feb 2004
Posts: 564
Likes: 0
From: Pittsburgh PA
something to remember, too... it will seem that you'll reach a point, where "after THIS time with sanding the guide-coat, it'll be DONE...." and then you discover something else that needs attention....
But DON'T give up. Patience and insistence on perfection WILL pay off.... with BIG rewards.
God knows, I've blocked my car 5 times... and it's STILL not where I want it...
But DON'T give up. Patience and insistence on perfection WILL pay off.... with BIG rewards.
God knows, I've blocked my car 5 times... and it's STILL not where I want it...
Drifting
Joined: Jan 2006
Posts: 1,944
Likes: 22
From: Yooperville MI
Different painters use different techniques and big_g is right on with the blocks, there are lots of curves on C3s and it's very important to use the right block and avoid using your hand as a block. After stripping and major body repairs are completed, I clean and spray the body with PPG DPLF primer, apply filler where needed, prime it, and start the block sanding. I use gray and red oxide PPG Kondar primer alternatively, 2 coats, block sanding each color just until the previous color shows through, then recoat and repeat sanding. Depending on the condition of the panel, it can take several coats of each primer to get the panel straight. But it's time well spent, especially on dark top coats. Good luck! 
Last edited by crazywelder; Mar 10, 2006 at 06:52 AM.
Pro
Joined: Jun 2005
Posts: 540
Likes: 4
St. Jude Donor '09, '24
There are many different ways of getting the panels flat. Before I primer the car I use the Dynaglass to take the low spots out of the car. I mark the spots that I feel with your hand and see with a straight edge. Mark all the spots on the car then fill them in with the Dynaglass and let dry. Come back and sand and feather in and your ready to primer and block the car. The Dynaglass makes it easier to get the panels flat IMHO because you are adding more material to only the spots that need it. When using primers to fill in low spots you are adding primer to the low spots along with the high spots on the car. Then you are sanding the high spot primer back down close to the original height it was before you added last coat of primer along with the low spots you have built up. When using Dynaglass the thickness should be kept to under 1/8". If you need more then that you need to repair the panel with matt, houstonvett
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Thread Starter
Safety Car
Joined: May 2005
Posts: 4,176
Likes: 7
From: Jennings LA
dynaglass?
checked the price on urethane high build primer today, definitly do not want to use more than I have to. that stuff is more expensive than the top coat. what type of filler is dynaglass? is it body filler?
Burning Brakes
Joined: Mar 2006
Posts: 1,036
Likes: 2
From: Huntingburg Indiana
dynaglass is a fiberglass reinforced filler. I was always told when blocking, use the longest block that you can on the panel. If you use a small block on a large panel, you will sand waves into it. Hope this helps.
Thread Starter
Safety Car
Joined: May 2005
Posts: 4,176
Likes: 7
From: Jennings LA
what size block do you use on the rear quarter panels? I was using a 5 inch and a 7 inch. the only straight part on the quarter is the lower section. it is basicly one big curve
Pro
Joined: Jun 2005
Posts: 540
Likes: 4
St. Jude Donor '09, '24
Originally Posted by gator79
checked the price on urethane high build primer today, definitly do not want to use more than I have to. that stuff is more expensive than the top coat. what type of filler is dynaglass? is it body filler?
It can be used as a top coat filler. Comes in long or short strand versions. I use the shorter strand for filling in the low spots. It will be very close to the same consistency of Plastic Bondo. The radiused panels on the vettes are hard to get them to look flat or smooth when painted. I go with the hand method and mark the low spots and fill them in. Patiance is required and the more dillegence you put forth in the prep the better the paint job will be when finished, houstonvett
Le Mans Master
Joined: Jul 2005
Posts: 5,752
Likes: 4
From: Austin Texas
Thread Starter
Safety Car
Joined: May 2005
Posts: 4,176
Likes: 7
From: Jennings LA
I know on metal you usually grind the surface so the filler can get a good grip. is this necessary with fiberglass. I mainly need to smooth out the seams from the bonding strips.
Thread Starter
Safety Car
Joined: May 2005
Posts: 4,176
Likes: 7
From: Jennings LA
Originally Posted by big_G
Don't need to get too aggressive here...180 grit is fine.
is the 180 to rough it up for the filler? also my sanding blocks are like the yellow one. thanks for the input
Burning Brakes
Joined: Oct 2003
Posts: 836
Likes: 26
From: Harrisburg Pa
If your vette was striped to the bare glass do you guys reinstall the gelcoat or just use a primer filler and bondo to fill in the pin holes.
My vette had all the gelcoat removed and now am stuck and cant find gelcoat.
My vette had all the gelcoat removed and now am stuck and cant find gelcoat.
Thread Starter
Safety Car
Joined: May 2005
Posts: 4,176
Likes: 7
From: Jennings LA
Originally Posted by TOM B1
If your vette was striped to the bare glass do you guys reinstall the gelcoat or just use a primer filler and bondo to fill in the pin holes.
My vette had all the gelcoat removed and now am stuck and cant find gelcoat.
My vette had all the gelcoat removed and now am stuck and cant find gelcoat.
