[Moon] [Moon-Net] [az_ws_microwave] Help Requested for Refinishing my Solid 4.9m Dish
ok1dfc at seznam.cz
Wed Oct 14 11:56:18 CEST 2020
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
Zdenek - OK1DFC
QRV EME 144 MHz - 24 GHz
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
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.
On Tue, Oct 13, 2020 at 11:31 AM Bob Kocisko <k6pf at sbcglobal.net
(mailto:k6pf at sbcglobal.net)> wrote:
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
Tnx for any help & vy 73,
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