Pin holes (again)

After removing all the gelcoat, a friend recommended applying a very thin cloth known as Vail to fill most pinholes. We brushed on epoxy and rolled on the Vail, followed with thin peal-ply, then squeegee'd it out with excess resin toward the trailing edges of the wing. Not sure it worked all that well and took two of us 4 hours + $400 bucks for Vail, resin and peal-ply. In some areas (near spoilers), we trapped some resin between the Vail and peal-ply which was full of pin holes!
I think the concept is good, but next time I believe I'll skip the Vail and just brush on epoxy and cover it with peal-ply. The resin has got to fill most pin holes and the peal-ply will leave the surface ready to prime.
Would like to know what others are doing?
JJ

On Tuesday, April 4, 2017 at 10:18:43 AM UTC-4, wrote:
After removing all the gelcoat, a friend recommended applying a very thin cloth known as Vail to fill most pinholes. We brushed on epoxy and rolled on the Vail, followed with thin peal-ply, then squeegee'd it out with excess resin toward the trailing edges of the wing. Not sure it worked all that well and took two of us 4 hours + $400 bucks for Vail, resin and peal-ply. In some areas (near spoilers), we trapped some resin between the Vail and peal-ply which was full of pin holes!
I think the concept is good, but next time I believe I'll skip the Vail and just brush on epoxy and cover it with peal-ply. The resin has got to fill most pin holes and the peal-ply will leave the surface ready to prime.
Would like to know what others are doing?
JJ

If surface does not need any replacement of cloth for structural reasons, I have found the following to work best for me.
1)Blow as much dust off the surface and out of defects as possible.
2) Apply PCL Polyprimer using a 4 inch foam roller using a good bit of pressure on the roller. The first coat is not all that thick and the objective is to work the filler into the pinholes. I use 907 white for these coats.When it has tacked off I roll a second coat which covers and lets me see the defects that are not filled.
3) Spot in all the defects I can see, then spray one coat of 901 gray.
4) Sand and continue.
This usually gets 90-95% of the pinholes for me.
Good Luck
UH

Go with Hanks advice. He guided me in the refinish of CF and it turned out great. I was constantly advised by spectators as to how I "should do it". One guy grabbed a gear foot and promptly sanded through to the foam core. From then on I didn't mind being rude to the next neighbor with the "better idea". In short, don't make it complicated.

Simtec also has a filler if you are using their products.

Lane

On Tuesday, April 4, 2017 at 10:53:46 AM UTC-4, wrote:
Go with Hanks advice. He guided me in the refinish of CF and it turned out great. I was constantly advised by spectators as to how I "should do it". One guy grabbed a gear foot and promptly sanded through to the foam core. From then on I didn't mind being rude to the next neighbor with the "better idea". In short, don't make it complicated.

Simtec also has a filler if you are using their products.

Lane

Simtec 2081 does not sand anywhere as well as Polyprimer. JJ put me on to Polyprimer.
UH

I'll second (actually third) Hank's recommendation. I'm now a disciple of UH and Church of the Holy Pinhole.

Our club tends to wait until the existing gelcoat approximates the look of a dessicated mud flat before we start a refinish. So, almost all the old gelcoat ends up coming off, which results in PINHOLE HELL. After following Hanks advice on last year's LS4 project, I could count the number of pinholes with hands and toes, as opposed to prior jobs where we spent several cycles trying to spray our way out. This year's Grob Fuselage had a couple of pinhole fields only because I was sloppy on the prep work.

In terms of prep, I supplement the air blowing with a wipe down using a lint-free rag and either Prep All or Acetone.

I'll add that a really soft rubber scraper used to squeegee the Polyprimer into really bad pinhole fields seems to work even better than the roller if you are careful. We sometime roll then go over with the scraper working back and forth a few times.

P3

On Tuesday, April 4, 2017 at 11:56:12 AM UTC-4, wrote:
On Tuesday, April 4, 2017 at 10:53:46 AM UTC-4, wrote:
Go with Hanks advice. He guided me in the refinish of CF and it turned out great. I was constantly advised by spectators as to how I "should do it". One guy grabbed a gear foot and promptly sanded through to the foam core.. From then on I didn't mind being rude to the next neighbor with the "better idea". In short, don't make it complicated.

Simtec also has a filler if you are using their products.

Lane

Simtec 2081 does not sand anywhere as well as Polyprimer. JJ put me on to Polyprimer.
UH

On Tuesday, April 4, 2017 at 11:56:12 AM UTC-4, wrote:
On Tuesday, April 4, 2017 at 10:53:46 AM UTC-4, wrote:
Go with Hanks advice. He guided me in the refinish of CF and it turned out great. I was constantly advised by spectators as to how I "should do it". One guy grabbed a gear foot and promptly sanded through to the foam core.. From then on I didn't mind being rude to the next neighbor with the "better idea". In short, don't make it complicated.

Simtec also has a filler if you are using their products.

Lane

Simtec 2081 does not sand anywhere as well as Polyprimer. JJ put me on to Polyprimer.
UH

2081 sands fine if you add a little gelcoat. i'd be interested to try polyprimer sometime.

We nuke about an ounce of epoxy in the shop microwave until it is almost too hot to hold, then quickly squeegee it across the pinholed surface so it forms a meniscus that fills in the square corners of each pinhole. An ounce covers like 10-20 square feet. We generally do that twice, and then sand the remaining epoxy off and fill the remaining weak depressions with Duratec.

I use the soft squeegee and polyprimer to good effect. Something else that helps is to get the wing hot and then prime it. Allow to cool. The cooling seems to suck the primer down into the microvoids as the air in them cools and thus decreases its volume, creating a slight vacuum.

Fidel, actually pulled a slight (2-3"hg) on my wings. Then spread thinned out epoxy on the surface over the multitude of pinholes. Cured it and then tested it with 3-4 ft of head pressure with water worked great and the completed the refinish😀 No leaks so far that was about 8 years ago?

On Wednesday, April 5, 2017 at 7:19:17 AM UTC-7, wrote:
Fidel, actually pulled a slight (2-3"hg) on my wings...

I'm going to remember that trick; it sounds like a great way to address the leaky bondlines that I've heard of on early LAK-17. But I imagine that if your vacuum regulator slipped you could make a mess of a wing in a real hurry.

--Bob K.