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  #1  
Old 02-10-2021, 03:14 PM
avatty avatty is offline
 
Join Date: Sep 2015
Location: Walnut Creek, CA
Posts: 44
Default Fiberglass parts finishing question

I am beginning work on the empennage and wing fiberglass, and have read several threads, including Dan Hs, and builder websites. Question: Is it necessary to apply a two part filler/sealer primer (such as PPG K36 Acrylic Urethane Primer Surface) upon finishing with the smooth primer and sanding, or can this wait until a time closer to painting?

I have been priming the aluminum with SEM rattle cans, and painting the interior the same way. I have not equipped for spraying 2-part epoxy mixtures, and hope to use a builder-friendly paint shop when that time comes.

Also, I am still looking for other good discussion threads, EAA webinars, youtubes or what-have-yous to preview the fiberglass work, and would appreciate any recommendations. Thanks!
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  #2  
Old 02-10-2021, 04:58 PM
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DanH DanH is offline
 
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Location: 08A
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Quote:
Originally Posted by avatty View Post
I am beginning work on the empennage and wing fiberglass, and have read several threads, including Dan Hs, and builder websites. Question: Is it necessary to apply a two part filler/sealer primer (such as PPG K36 Acrylic Urethane Primer Surface) upon finishing with the smooth primer and sanding, or can this wait until a time closer to painting?
If the surface is smooth, pinhole free, and not wavy, a fellow can have a presentable surface with just primer and finish paint. However, the perfect mirror finishes (no "fun house mirror" distortion) are the result of patient block sanding.

Think of K36 as a filler, sprayed on. This kind of product is also known as a "high build primer". Where an epoxy primer might be 0.75 mils thick, something like K36 might go on 3 mils thick, after which most of it is block sanded away, filling all the low spots. Block sanding is the key. The goal is to optically flatten the final surface.

In the PPG system, spray DPLF epoxy primer, then two cross coats (four passes) of K36. Use a primer with a contrasting color, like dark gray, so that when you block it, the high spots show up clearly as the K36 is sanded away. When the primer starts to show, stop and spray more K36 if there are still low spots.

Yes your painter can do all of it, but you will pay the labor, and done right it burns a lot of time.

Quote:
Also, I am still looking for other good discussion threads, EAA webinars, youtubes or what-have-yous to preview the fiberglass work, and would appreciate any recommendations.
Fiberglass fabrication and fiberglass finishing are very different subjects.
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  #3  
Old 02-10-2021, 06:46 PM
John Tierney John Tierney is offline
 
Join Date: Jan 2006
Location: Vonore, TN
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I used a PPG Omni brand 2K Urethane rollable high build filler primer (Omni MP 282), sanded that smooth and then sprayed an epoxy primer (Omni MP 170) over that since I was going to fly for about a year before painting.
Depending on how much work you want your painters to do, you might be able to get away with just rolling it on and having the painters sand it down.
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  #4  
Old 02-10-2021, 07:53 PM
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wirejock wirejock is offline
 
Join Date: Oct 2005
Location: Estes Park, CO
Posts: 4,209
Default Paint shop

If you plan to use a paint shop, don't put anything on the outside. Most likely they will charge you to strip it off. They can't warranty a paint job if they didn't prep the surface.
That said, you might ask around and see what products they will allow. Some shops may share their preferred product line and actually cut you a but of a discount for prepping parts.
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http://wirejockrv7a.blogspot.com
wirejock at yahoo dot com
Donated 01/01/2021, plus a little extra.
RV-7A #73391, N511RV reserved (2,000+ hours)
HS SB, empennage, tanks, wings, fuse, working finishing kit
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I cannot be, nor will I be, held responsible if you try to do the same things I do and it does not work and/or causes you loss, injury, or even death in the process.
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  #5  
Old 02-10-2021, 10:46 PM
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DanH DanH is offline
 
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Best example of perfect blocking I have ever seen, Monty Barrett's 40 Ford retro rod. He handed it over to some pros who kept it for many months and did really fabulous work.

Look at the reflection in the left rear fender. Every panel is like that, and it's all compound curves.

BTW, Monty has been gone a while now, and Ms. Betty would probably sell Ford if asked. Call Rhonda at Barrett Precision Engines.

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  #6  
Old 02-11-2021, 09:54 AM
Bavafa Bavafa is offline
 
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Location: Sacramento, CA
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Quote:
Originally Posted by DanH View Post
Best example of perfect blocking I have ever seen, Monty Barrett's 40 Ford retro rod. He handed it over to some pros who kept it for many months and did really fabulous work.

Look at the reflection in the left rear fender. Every panel is like that, and it's all compound curves.

BTW, Monty has been gone a while now, and Ms. Betty would probably sell Ford if asked. Call Rhonda at Barrett Precision Engines.

I have wet sanded paint and had my plane wet sanded completely after a thicker than normal clear and I don't believe I have ever seen as smooth/shinier paint job as this one.
It must have cost an arm and a leg plus some.
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  #7  
Old 02-11-2021, 10:36 AM
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DanH DanH is offline
 
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Quote:
Originally Posted by Bavafa View Post
I have wet sanded paint and had my plane wet sanded completely after a thicker than normal clear and I don't believe I have ever seen as smooth/shinier paint job as this one.
It must have cost an arm and a leg plus some.
This kind of optically flat surface is all about blocking prior to application of paint.
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