[Moon] [Moon-Net] [az_ws_microwave] Help Requested for Refinishing my Solid 4.9m Dish

[Zdenek SAMEK-OK1DFC]

I don't see a big problem in repairing the cracks. The places where the mesh
is missing need to cut equal sizes from the aluminium mesh against the 
insects, depending on the bits that are dying. Then use polymer resin and 
have it hardened. After the surface has been sanded, paint with the colour 
intended for laminate surfaces. You can get one at Home Depot, no problem. 
Good luck and see you via Moon

73!


-- 
Zdenek - OK1DFC
www.ok1dfc.com
QRV EME 144 MHz - 24 GHz
WAC 70-23-13-6-3cm
WAZ #9 - WAS 432 #29
DXCC 432 - 1296 MHz


---------- Původní e-mail ----------
Od: Ron Jones via Moon-net <moon-net at mailman.pe1itr.com>
Komu: Bob Kocisko <k6pf at sbcglobal.net>
Datum: 14. 10. 2020 11:46:48
Předmět: Re: [Moon-Net] [az_ws_microwave] Help Requested for Refinishing my 
Solid 4.9m Dish 
"
Hi Bob, 
Looks like the guy in the blue shirt is me!! HI HI  Glad to see you making 
progress on this huge project.

I think I can help you a little with it, depending on schedules etc.

I have a question, however. The mesh is in good shape. The top coating 
currently on the mesh is indeed cracking, but so what. Why not go over it 
with something that will remove the big flakes that are truly chipping off 
and do whatever minor repairs may need to be done to the exposed mesh, I 
don't think you need to do much sanding or any especially fine work . Since 
you are planning to coat it with some sort of resin before you paint it, I'd
worry only about the pieces that are currently flaking off.

I have some experience with fiberglass resins, but only a little, but, since
the real RF reflector is the mesh, hand applying a thin coat of resin to the
surface using some plastic spreaders should be fairly easy. You are going to
paint over it so if it isn't perfect it really won't matter.




Good luck,Let me know your schedule and I'll see if I can make it up there.

73

Ron




On Tue, Oct 13, 2020 at 11:31 AM Bob Kocisko <k6pf at sbcglobal.net
(mailto:k6pf at sbcglobal.net)> wrote:

" 



Hello Friends:

 
 
I’d like to see if someone in these EME & microwave groups has had any 
experience refinishing a solid fiberglass dish.  In 2015, I acquired the 4.9
m (16 ft diameter) dish shown in PICT0091.  I purchased it fm Tom, K7NII 
(shown in the red jacket), who unfortunately became a SK shortly after he 
sold it to me in 2015.  The dish was originally used for SATCOM & I was told
it was useable to 12 GHz.  Tom built the entire mounting structure including
AZ/EL system.  When I moved it to my QTH, the dish was broken down into it’s
4 sections & has bn in my yard that way for the past 5 yrs.  Unfortunately, 
the WX has deteriorated the painted surface.

 
 
I’m in the process of refinishing the entire system w/ hopes of initially 
getting on 23cm EME & maybe someday on 3cm EME.  So far, I have the footing 
in place & the entire metal mounting structure has been refinished & 
painted.  Hopefully, I’ll get a reach lift in here within the next couple of
weeks to lift all of the metal pieces onto the footing.  Now, I’m ready to 
refinish the surface of the 4 sections of the dish.

 
 
Also attached are 3 photos showing various parts of the surface that have 
deteriorated.  The mesh seems to be intact except for a few very small areas
which I would think won’t affect performance.  Maybe I can fill in those 
areas with small pieces of AL foil.  As you can see, there was a smooth coat
of white paint over the mesh followed by a top coat of crinkly white paint 
(presumably for spectral diffusion to minimize getting the electronics at 
the focus too hot).  I found a company (Triangle Coatings, Inc at www.
tricoat.com(http://www.tricoat.com)) that makes primers & paint for 
microwave dishes including NASA’s DSN.  Their products are RF transparent & 
also the top coat which is smooth has high IR reflectance to protect 
electronics at the feed fm IR & heat accumulation.  I spoke w/ the owner of 
the company (Ned Kisner) & will be ordering their Aquapoxy Primer (283PAJ60)
for my dish surface + their 7 Series Goldstone top coat.  Also, I’ll paint 
the sides & back of the dish with their 44 Series Epoxy Acrylic DTM.  I’m 
mentioning this in case anyone else is looking for similar products.

 
 
Now, I still need help in 2 areas:  First, for preparation of the surface to
clean it of the cracked & peeling paint.  I’ve explored Soda Blasting 
thinking that it might clean up the surface without damaging the mesh.  But 
a couple of people have now said that light sanding may be the best way to 
go.  Anyone have experience with this?  It’s not my objective to remove all 
of the top 2 coats of paint & get down to the bare mesh.  

 
 
Second, after cleaning up the surface say with light sanding, I’m wondering 
if using either Gel Coat or a fiberglass resin would be wise to seal the 
mesh & cracks in paint that were not removed by sanding?  I would then roll 
on Triangle’s Aquapoxy Primer followed by 2 coats of their 7 Series top 
coat.  I know the primer & paint are RF transparent but don’t know if either
Gel Coat or fiberglass resin are also.  Any help with that question?

 
 
I hope to be on 23cm EME sometime next year with a 350 watt BEKO PA.  
Hopefully, I’ll be able to work at least the bigger stations off the moon on
SSB.

 
 
Tnx for any help & vy 73,

 
 
Bob, K6PF

DM34ss



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