Antenna Dishes

Thrusterhead Jones · Post by **Thrusterhead Jones** » Wed May 06, 2009 1:37 pm

Ever find yourself wishing for a perfectly formed parabolic antenna dish?

I think I've found the answer: the bottom of a spray can.

Find a can (paint, deodarant, shaving cream, or my favorite- whipped cream (I get to whiff the last of the notrous oxide from it, and it's not messy like spray paint!)) Notice that not all cans have the same diameter or have that perfect paraballic profile you want.

Next. cut with a hacksaw all away around the bottom of the can about 1/4"- don't cut too deeply or you'll have some puttying to do to the resulting gouges! Once you've seperated the top from the bottom, clean out the bottom part with the approprate solvent (another reason I like whipped cream- it's water soulible). Then file away the seam around the outside of the bottom. Be careful and not cut yourself, and be patient- you'll want the bottom as flat as possible.

After a couple of hours (three CDs if you're listening to your IPod) of filing all around the bottom of the can you'll notice that a consentric line has appeared half way between the inside and outise surfaces of the bottom seam. Keep filing untill this line goes all around the bottom seam. when this happens the leftover can and the inside "ring" of the seam should split for easy removal. If it should prove to be recalitrant an impact device like a small brass hammer gently but firmly applied to the outside circumfrance of the seam should loosen it up.

Deburr, putty, and paint as required. And again, be careful! You're dealing with what could be razor sharp metal coated with chemicals (or whipped cream). Use only enough force to get the job done- no one likes to see all their hard work ending up like a potato chip!

Happy modeling!

tyler · Post by **tyler** » Thu May 21, 2009 12:36 am

I scratchbuilt a little ship about a year ago and built a dish using a bubble like one of these

it didn't come out perfect

but I'm sure someone with a little more experience than me could do better.

Thrusterhead Jones · Post by **Thrusterhead Jones** » Thu May 21, 2009 10:50 am

Nice job Tyler- I especially like the antenna mount.

The hogging out of the bottom of the can is the most labor-intensive part of the job, but finding the center of the parabolic dish is the real pain. It would be a cinch if I knew someone with a lathe, but alas!

The best way I have found so far is to work it out on paper with a compass, or if you have the software, on some sort of CAD program and transfer it onto the dish. Or you might be able to rig a jig for the job. I’m still refining the process, and I don’t go through cans of whipped cream fast enough. I hop to get it right soon complete with pictures.

Don’t give up!

Mark Yungblut · Post by **Mark Yungblut** » Wed May 27, 2009 12:08 pm

If you roll out Aves or one of the other epoxy putties in a sheet and use some cornstarch as your release agent you can make the same thig by draping it in the concave part of the spray can. It'll cure in just a couple of hours.

Cheers,

Mark

seam-filler · Post by **seam-filler** » Thu May 28, 2009 1:19 am

Thrusterhead Jones wrote:Nice job Tyler- I especially like the antenna mount.

The hogging out of the bottom of the can is the most labor-intensive part of the job, but finding the center of the parabolic dish is the real pain. It would be a cinch if I knew someone with a lathe, but alas!

The best way I have found so far is to work it out on paper with a compass, or if you have the software, on some sort of CAD program and transfer it onto the dish. Or you might be able to rig a jig for the job. I’m still refining the process, and I don’t go through cans of whipped cream fast enough. I hop to get it right soon complete with pictures.

Don’t give up!

Sounds like you need a Centre Square like this (but there are cheaper ones if you look). That'll find the centre.

Kylwell · Post by **Kylwell** » Thu May 28, 2009 10:27 am

I keep thinking about getting some dapping blocks & punches for forming thin metal and PE into dome shapes.

Antenociti · Post by **Antenociti** » Thu May 28, 2009 11:02 am

Thrusterhead Jones wrote:Ever find yourself wishing for a perfectly formed parabolic antenna dish?

I think I've found the answer: the bottom of a spray can.

Find a can (paint, deodarant, shaving cream, or my favorite- whipped cream (I get to whiff the last of the notrous oxide from it, and it's not messy like spray paint!)) Notice that not all cans have the same diameter or have that perfect paraballic profile you want.

Next. cut with a hacksaw all away around the bottom of the can about 1/4"- don't cut too deeply or you'll have some puttying to do to the resulting gouges! Once you've seperated the top from the bottom, clean out the bottom part with the approprate solvent (another reason I like whipped cream- it's water soulible). Then file away the seam around the outside of the bottom. Be careful and not cut yourself, and be patient- you'll want the bottom as flat as possible.

After a couple of hours (three CDs if you're listening to your IPod) of filing all around the bottom of the can you'll notice that a consentric line has appeared half way between the inside and outise surfaces of the bottom seam. Keep filing untill this line goes all around the bottom seam. when this happens the leftover can and the inside "ring" of the seam should split for easy removal. If it should prove to be recalitrant an impact device like a small brass hammer gently but firmly applied to the outside circumfrance of the seam should loosen it up.

Deburr, putty, and paint as required. And again, be careful! You're dealing with what could be razor sharp metal coated with chemicals (or whipped cream). Use only enough force to get the job done- no one likes to see all their hard work ending up like a potato chip!

Happy modeling!

Genius!

Thank you!

Thrusterhead Jones · Post by **Thrusterhead Jones** » Thu May 28, 2009 11:45 am

Mark, with the Alves putty method how do you keep a good surface on the inner (concave) face and a uniform thickness of the putty?

And what exactly is Alves? My local hobbyshop dosen't seem to carry it.

Kylwell · Post by **Kylwell** » Thu May 28, 2009 11:59 am

Thrusterhead Jones wrote:Mark, with the Alves putty method how do you keep a good surface on the inner (concave) face and a uniform thickness of the putty?

And what exactly is Alves? My local hobbyshop dosen't seem to carry it.

Aves is a non-toxic 2 part putty. Dries in 4 hours (no matter how thick) to the general hardness of styrene. You can roll it out in very thin sheets, drape it over an object and 4 hours later, you have a very nice shell.

Thrusterhead Jones · Post by **Thrusterhead Jones** » Thu May 28, 2009 7:17 pm

I looked up Alves on the ‘net- their site was the only one I found. Interesting stuff- I’ll have to get some and experiment with it. Are there other suppliers I can buy from without going through Alves?

Is it possible to use this stuff to make molds for recreating greebles or greeble assemblies? This would be most useful. Have a limited supply of greebles that I consider “irreplaceable” (not intended for modeling), but would love to use on a spacecraft.

This just in: I have found that by using a deburring tool and a file I can remove the concave bottom of an aerosol can in less than 15 minutes without distorting it. It could be done even faster by the judicial use of a bench grinder, but you’d have to make damn sure any flammable contents or propellants have been vented off! (flammable vapors and sparks do mix- with potentially spectacular results)! And don’t bother to cut the bottom inch or so from the can- leave it on, you’ll have more to hang on to while you’re working.

Joseph C. Brown · Post by **Joseph C. Brown** » Fri May 29, 2009 10:21 am

Thrusterhead Jones wrote:I looked up Alves on the ‘net- their site was the only one I found. Interesting stuff- I’ll have to get some and experiment with it. Are there other suppliers I can buy from without going through Alves?

These folks have a good business rep and fast shipping:

http://www.starshipmodeler.biz/index.cf ... gory_id=75

Thrusterhead Jones wrote: Is it possible to use this stuff to make molds for recreating greebles or greeble assemblies? This would be most useful. Have a limited supply of greebles that I consider “irreplaceable” (not intended for modeling), but would love to use on a spacecraft.

The Aves putty will take an impression of an item that can be virtually the equivalent of a mirror image. Just lightly dust the item that you are wanting to duplicate with cornstarch (as a release agent) before pressing it into some putty. Let the putty cure - it gets rock hard within 6-8 hours.

Mark Y. did some great classes with Aves putties at Wonderfest - the class notes can be downloaded below.

NOTE: These links are to PDF files!

http://www.starshipmodeler.info/wfest2k ... tty101.pdf

http://www.starshipmodeler.info/wfest2k ... tPutty.pdf

Mark's promised to provide some updates in a few weeks to this data.

Thrusterhead Jones · Post by **Thrusterhead Jones** » Fri May 29, 2009 1:22 pm

Most excellent! I shall be ordering some Alves Apoxy forthwith, or maybe sooner (Thirdwith? Fifthewith ?)

Squadron’s “Merde Vert” just dosen’t cut it. The stuff dries out in its tube, takes forever to get hard, and once it does, it’s crumbly and clogs up my files and sandpaper. But it's the only game in town at my local hobby shop.

At this point anything would be better. As the crying baby said, "It's time for a change!"

Chacal · Post by **Chacal** » Fri May 29, 2009 4:39 pm

Word of advice: stop calling it 'Alves'. The abbots and abbesses will hit'ya over the noggin with a rolling pin.

Scotaidh · Post by **Scotaidh** » Fri May 29, 2009 4:45 pm

Thrusterhead Jones wrote:Nice job Tyler- I especially like the antenna mount.

The hogging out of the bottom of the can is the most labor-intensive part of the job, but finding the center of the parabolic dish is the real pain. It would be a cinch if I knew someone with a lathe, but alas!

The best way I have found so far is to work it out on paper with a compass, or if you have the software, on some sort of CAD program and transfer it onto the dish. Or you might be able to rig a jig for the job. I’m still refining the process, and I don’t go through cans of whipped cream fast enough. I hop to get it right soon complete with pictures.

Don’t give up!

Get yourself to a hardware store and find a combination square - you want something like this. The bit you really need is the Vee. hey're not too expensive, and a good one will last the rest of your children's lives.

Thrusterhead Jones · Post by **Thrusterhead Jones** » Sun May 31, 2009 11:26 pm

I really don’t think a small combo square would do the job.

Because I want to find the center of the inside face of a concave part a combo square would only indicate a point on an imaginary plane on the rim of the dish. This point would then have to be projected down onto the concave inner face, with the probability of error resulting in an out-of-round condition.

Here’s how I’ve been doing it: Smear a small blob of Handi Tac, Playdough, Silly Putty, or similar on the center of the dish’s concave face. Grab your handy dandy drawing compass and set it for a bit farther than half of the diameter of the dish. Using one point of the compass on the rim of the dish, make a indentation with the other point as close as possible to the center of the disk. Apply the point several times around the circumference of the dish and observe the point at the center of the disk. If you’re lucky the point on the face will show you where the center actually is. If you slip up with the compass point on the dish’s rim, just smooth out the putty and try again.

I’ve tried this method on three dishes with good results. (Your mileage may vary.)

Post by **TER-OR** » Mon Jun 01, 2009 10:09 pm

Here's another way: Coat the interior of the dome on the bottom of the can with silicone spray. Push Aves into the dome, allow to cure. Remove and you get a buck over which you can thermoform with styrene or use the Aves draping method.

Thanks for reminding me of the can bottoms, I've wanted to do some dishes like this for a while.

Thrusterhead Jones · Post by **Thrusterhead Jones** » Tue Jun 02, 2009 12:31 am

Thanks for the tip, Terry. My first shipment of Alves should be hitting my doorstep either Wednesday or Thursday, so I’ll have to try your method. I like the can bottoms though, because they’re thin, uniform in shape and size, and now that I know how do them, not that hard to do. Now every few days I go through the cabinets looking for my next victims!

I’ve gone another step and CA gluing 0.1” styrene strips for the webbing on the back side (convex side) of the dish. Until I perfect that operation, it’s going to remain a total PITA!. To do it in Alves I’d have to do a double impression- the first would have the impression of the webbing on the outside of the dish, then use that as a buck, then do the draping on the inside of the buck where the draped part would pick up the detail of the webbing.

(Hoo ha! Easier to do than to write about it.)
[size=18][/size]

Joseph C. Brown · Post by **Joseph C. Brown** » Tue Jun 02, 2009 6:43 am

It sounds like you are on your way with the technique - let everyone know how it turns out!

---
That being said (and I'm sure that I'll catch a lot flak over this part) ... the product is Aves, not Alves. It's alot like looking at a Ford truck and saying that it is a Flord truck.

I know, I know - it's a minor point, but, Aves is an epoxy putty, while Alves is either a Brazilian football player or a UFC Fighter.

Modeling product:
http://www.avesstudio.com/

Soccer:
http://en.wikipedia.org/wiki/Daniel_Alves

UFC Fighter:
http://www.sherdog.com/fighter/Thiago-Alves-5998

Chacal · Post by **Chacal** » Tue Jun 02, 2009 7:58 am

See, Mr. Jones? Here they come with the rolling pins

Thrusterhead Jones · Post by **Thrusterhead Jones** » Tue Jun 02, 2009 10:53 am

My apologies.

Its one of those “You look but do not see.” situations combined with “fat fingers” syndrome. I’ll try to do better…

Blappy · Post by **Blappy** » Tue Jun 02, 2009 12:36 pm

Kylwell wrote:I keep thinking about getting some dapping blocks & punches for forming thin metal and PE into dome shapes.

Well you learn something new everyday. I can see a multitude of uses for something like that. There is a great variety on Ebay as well for fair prices.

rommel twee · Post by **rommel twee** » Thu Jun 04, 2009 4:28 pm

Not to blow my own horn

http://ironwindmetals.com/catalog/produ ... ts_id=4411

http://ironwindmetals.com/catalog/images/Radar.jpg

Dr. Yo · Post by **Dr. Yo** » Thu Jun 04, 2009 4:41 pm

One other possibilty- Hobby Lobby carries a simple plastic pallette,
with around 10-12 dishes for paint mixing. They're about an inch to
an inch and a half in diameter, and shallow enough to serve as a
good radar dish. The plastic is thin enough to be cut fairly easily too.
It was 99cents-cheap!

Andrew Gorman · Post by **Andrew Gorman** » Thu Jun 04, 2009 6:34 pm

I've used a cheap Indian dapping block and punch set for making all kinds of shallow domes, and it works pretty well. Very thin plastic can be formed cold, but thicker material works better after being hit with a heat gun.
The lids of fast food to-go cups often have nice little 1cm or so dishes molded into them.
Once you have ONE aerosol dome cut out, why not use it as a master to vacuform a bunch?

Thrusterhead Jones · Post by **Thrusterhead Jones** » Fri Jun 05, 2009 4:26 pm

Wonderful idea- assuming I have a vacuform machine (I'ts on my list of projects).

Earnan · Post by **Earnan** » Sun Jul 05, 2009 9:09 pm

Thrusterhead Jones wrote:Mark, with the Alves putty method how do you keep a good surface on the inner (concave) face and a uniform thickness of the putty?

Uniform thickness? Lay out two pieces of rodstock (square or rectangular cross-section) on either side of your putty work space. Mash your putty to general flatness though slightly thicker than your target. Use a rolling pin for hobby work and roll the putty mass using the rodstock to maintain the desired thickness.

I want 3mm thick walls so I get 3mm rodstock as guide height. I work the putty to 5mm more or less, roll out to precision. After getting the slab done I cut the base line level and corner joins too, if necessary.

Would this be worth a short tutorial vid on YouTube? I've been thinking about a few.

scratchy · Post by **scratchy** » Wed Nov 25, 2009 8:28 pm

Hi All,

I stumbled across this thread and thought that I might offer my two cents. My VERY first experiment in scratchbuilding happened, oh about.... I suppose I was 22 at the time. It was a dish like the one that's being discussed in this thread.

What I did;

-I cut out the bottom of a "pop" can ("wink, wink, nudge, nudge

)
-I drilled various holes using 1/16 drill bit in the bottom.
- Sanded down the burrs
- Placed the aluminum on a vacuum cleaner hose.
- Placed a piece of styrene on the can bottom.
- Turned the vacuum on and held it about 1/4" away from my gas fireplace (a heat gun will work too).
- Pulled it away, let it cool, turned the vacuum off

I did this a couple times and I combined two dishes into one, here's the results. I have yet to find a build for this,.
http://i658.photobucket.com/albums/uu30 ... G_4217.jpg
http://i658.photobucket.com/albums/uu30 ... G_4218.jpg
http://i658.photobucket.com/albums/uu30 ... G_4219.jpg

I used a "Circle Template" to help engrave the lines and I glued a second dish in the center, added some bits of styrene, and there ya have it.

This is the piece that started this madness for me!

raser13 · Post by **raser13** » Mon Nov 30, 2009 12:59 am

easies way to find center of a dome is to set on a flat surface with the widest part up like a u. then put a small drop of drop water into it. where the water settles is center.

Springheel Jack · Post by **Springheel Jack** » Sat Jan 09, 2010 5:46 pm

I make dishes but cutting down and then sanding ping pong balls and plastic Christmas tree baubles.

david bailey · Post by **david bailey** » Sun Jul 25, 2010 1:22 am

For cheap radar dishes another method is rubber suction cups.They can be detailed and you have one on the cheap side.They can be bought in bulk packs for a dozen for $ 3.99 plus tax at the craft store,they come in different sizes as big as 2inchs for the big sizes all the way down to smaller sizes.I have used these alot on various builds .Just thought i pass the tip on for something cheap and easy.Thanks.

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