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  #61  
Old 04-16-2011, 02:44 AM
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az_gila az_gila is offline
 
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Quote:
Originally Posted by DanH View Post
It's like that E6Ti...it's generally found in old used cars.
Dan.. the Prestec polyester primer is used in sailplane refinishing and followed up with Prestec polyester paint.

It does seem to be the exception about using polyester over epoxy, but has been well proven over several decades on German sailplanes.

The Prestec paint does not yellow like some of the German factory sailplane finishes.

The company nmae is actually Simtec and they are a small outfit in the LA basin area, sort of near Aircraft Spruce. They were very easy to deal with directly.

http://www.simteccoatings.com/Productlist.ivnu
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  #62  
Old 04-16-2011, 08:45 AM
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Quote:
Originally Posted by AFulmer View Post
And Allen also asked:
"What about the few pinholes you did have? How did you fill those few remaining holdouts?" Polyester is out so what to use?
No, polyester is not out. As I've written before, polyester filler has three uses in my own shop.

(1) Fast touch up of minor defects discovered after the first spray coat of epoxy primer. Press some mixed fiiller into a pinhole, then come back in 15 minutes and sand off every trace except what remains down in the hole. It's not a pinhole filling proceedure. It's a quick save when I did a poor job with previous work and later find a renegade pinhole or chip after shooting the first coat of epoxy primer.

(2) Fairing wood wing surfaces under fabric.

(3) Jigs and fixtures.

Polyester primer? Years ago (early 90s) my body shop professional shot a good grade of polyester primer-surfacer on my glass/epoxy project, followed by a two-part single stage white. In about three years it started peeling. Next time you come by the hangar I'll show you.
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  #63  
Old 10-16-2011, 11:18 PM
fehdxl fehdxl is offline
 
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Dan,

What would you use to transition the overhead console to the rest of the cabin top?

Is this Evercoat polyester filler acceptable/appropriate?



Or is a micro/cabasil/flox slurry more appropriate?

Thx,

Jim
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  #64  
Old 10-18-2011, 12:32 PM
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Quote:
Originally Posted by fehdxl View Post
What would you use to transition the overhead console to the rest of the cabin top?
Sorry Jim, missed your post.

This is a right angle joint? The traditional way is a wiped-in filet of flox/epoxy mix followed by glass fabric before the flox cures. Use the round end of a tongue depressor to make the filet radius consistent along the joint length. The fabric will lay in a smaller radius if cut on the bias. Don't use glass tape unless you're willing to sand away the thick selvage edges later. Cut fabric (for thin edges) covered with soaked peel ply is more or less self-fairing and needs little subsequent filler for finishing (see post 41). I use dry micro for all fairing and finishing.
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Last edited by DanH : 10-18-2011 at 12:36 PM.
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  #65  
Old 10-19-2011, 01:35 AM
FlyTurtle FlyTurtle is offline
 
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Dan, thanks for all the info. This will come in very handy. Do you recommend and howto videos? Or ever thought on making any?
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  #66  
Old 10-19-2011, 08:13 AM
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Quote:
Originally Posted by FlyTurtle View Post
Do you recommend and howto videos? Or ever thought on making any?
No and **** no.

Buy this kit:

http://www.aircraftspruce.com/builde...hp?PN=01-15000

Read Moldless Composite Homebuilt Sandwich Aircraft Construction a few times (included in the kit). It's a better instructional piece than any current book or video.

Actually build the three practice exercises.

Then build airplane parts.
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  #67  
Old 08-26-2012, 04:05 PM
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More general fabrication. The task is to duplicate an existing cowling outlet panel, with a 4" extension. Later this panel will be modified to incorporate a variable exit.

The job needs a female mold. This example uses a quick-'n-dirty mold made with materials at hand.

Started by cobbling up an extension, as the need panel needs to extend aft of the firewall. It was simply taped to the existing panel. The existing panel is slick (finish painted base and clear), so all it needs is two coats of PVA to make it non-stick. After the PVA cures, lay up two plies of plain 9oz to make the female mold. Plain weave is fine as there are no significant compound curves.



After cure separate the mold from the part with an air hose. The stuff which looks like plastic wrap is the PVA film blown loose.



In this case the mold panel isn't perfect. The taped seam between the original part and the extension needs some fairing, and there are a few air bubble voids to fill. So, scuff off the high spots with 80 grit.....



....wipe in some micro, and come back tomorrow.

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Last edited by DanH : 07-15-2018 at 10:17 AM.
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  #68  
Old 08-26-2012, 04:12 PM
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Sand the cured micro as necessary for shape, wipe in neat epoxy to seal and fill pinholes. Finish up with a cheap nappy roller to leave an orange peel finish, a good sanding guide.



Allow epoxy cure, sand it slick, shoot it with a black spray can. Whatever you have on the shelf is fine. When the paint cures shoot it with two coats of PVA.



Lay out plastic sheet and stack up precut glass cloth as required. Mix resin, dump it on, add a top plastic sheet, and roll the resin into the cloth. Roll air and excess resin to the edges until you have a nice consolidated layup.



Trim to the correct size to cover the mold plus a little bit. Cut right through the plastic cover sheets. Peel the top sheet, flip the layup, and lay it on the mold.



Peel the other plastic sheet. Use a roller and a brush to smooth the layup into the mold, working out all air. The air is easy to see because you painted the mold a dark color. Add peel ply if you intend to bond to the part later. Peel ply saves sanding time as it leaves a nice fractured finish suitable for bonding with little prep. In this case I also added a strip of scrap cloth over the peel ply, down in the concave belly of the part. Epoxy tends to flow a bit initially, and would make the low spot overly wet. The scrap cloth soaks up any excess resin and tears off with the peel ply.



In the morning it is Happy Feet time.....rip off the peel ply and pop the part out of the mold. Wear gloves to handle the part until trimmed, as the glass needles along the untrimmed edges will really stick you. Trim the edges on the bandsaw and sand them straight with 80 grit on a 18"x3" sanding block.



As removed from the mold the surface finish is much like the wheelpants you get from Vans. No surprise. Subsequent finish steps to prepare for paint will be the same.

More later.
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Last edited by DanH : 07-15-2018 at 10:27 AM.
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  #69  
Old 09-12-2012, 12:32 AM
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Re-creating a belly blister for a certain yellow airplane. I have no idea how a skinny kid named Dick made the first one back in the 1960's, but it was my honor to make the second.

Start with a profile in dense block foam....



....then shape to contour....



....glue to a base, add a filet, and paint the whole thing with some epoxy.



Sand slick, spray some high build primer from a squirt can, sand again...



...shoot with some gloss black, then some PVA.

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Last edited by DanH : 07-15-2018 at 10:34 AM.
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  #70  
Old 09-12-2012, 12:40 AM
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The layup is 8.9oz 8-harness satin, because it drapes so nice over compound curves. A strip of tape thickened the flange where rivets would go later.



Time to cure, a little trimming, and gee, ain't it pretty?







Now if I can just talk them into hanging the airplane from the ceiling, I can see it when I visit the museum.

(Postscript...they did!)
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Last edited by DanH : 07-15-2018 at 10:37 AM.
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