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Old 11th February 2012, 04:36 AM   #251
kctess5 is offline kctess5  United States
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Your grandson is a lucky guy I can't wait to see your progress on these

I feel your pain on stopping projects near completion, I have a few of those hanging around
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Old 11th February 2012, 05:19 AM   #252
John L is offline John L  United States
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Quote:
Originally Posted by kctess5 View Post
Your grandson is a lucky guy I can't wait to see your progress on these

I feel your pain on stopping projects near completion, I have a few of those hanging around
In all honesty, I'm really worried that I won't be able to finish it. The problem is that the two pieces for the lenses are unfired green ware. And in order to make a mold I'm going to have to pour plaster around each piece.

I never showed what they look like, but here they are together.

Click the image to open in full size.

I'm only going to get one shot at this, because the plaster, when it sets up, will expand, rather than shrink like everything else. And the force is going to crack each clay piece and ruin them. If it doesn't work out right, I'm screwed.

But lets say I get the two molds to work, what am I going to do then? I already have pictures of the two completed mold frames but haven' had time to post them here. So if they do work, what am I going to use to pour inside the mold? And how much is this going to cost?

And here is where I will need some help. If I use an epoxy resin, its going to cost a good bit. Each mold will be just a one piece mold, with the inside open. I will use something to help fill up the space, but it will still require a whole lot of resin. And resin is really expensive. It will most likely require 2 gallons too, one for each diffusion lens.

Of course there is another approach. I could use a fiberglass application. It would be less expensive, but come with all the bad fumes and headaches.

So I will need to see if there is anyone who has worked with epoxy resins, fiberglass, or both. If so, perhaps that someone can give me some expert advice, because I have never worked with either of the products.

Last edited by John L; 11th February 2012 at 05:25 AM.
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Old 11th February 2012, 02:04 PM   #253
Carlp is offline Carlp  United States
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John,
I have SOME experience with epoxy and fiberglass having built a cedar-strip canoe and a few other smaller projects. Ask away (here or PM) and I'll see if I can help. If it's fumes you're worried about, check out MAS epoxies (MAS Epoxies - Easy Epoxy Resin & Adhesives. Marine Epoxy for Boat Repair & Boat Building; Automotive Epoxy; Epoxy for Woodworking, Signs, Surfboards, Other. New: Eco-Friendly Acetone Replacement, Non-Skid Repair).

Also, I don't really understand your process here. You have green moulds to use for casting the diffraction lenses? So there's a cavity inside these moulds into which you want to pour plaster? Or are you forming around the outside of these and somehow using that? Are you concerned that if you fire the greenware it'll change dimensions? Sorry for being dense, but I just don't get it. A little more explanation would help.

Thanks
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Old 11th February 2012, 02:10 PM   #254
John L is offline John L  United States
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I've been studying this eposy resin product more closely since my last post on it, and I think I understand a little bit more on the cost factor. And I also lay awake last night, wasting sleep.....again, but came up with a way to cut down on my need for a lot of epoxy resin.

Here's how I can do this. If I am successful with the plaster cast, I will turn the cast upside down and the base will become the top. Instead of trying to anticipate how to create an insert which would be attached to the underside of the top lid, there is a better way.

I could take some thin plastic kitchen cellophane, and work it around the inside of the cast. Then get a bunch of clay and fill every nick and cranny of the inside with all the clay until I have it totally filled up.

Then just remove the clay by turning the cast upside down and let gravity cause it to come out. Once I have the contoured clay out I can place it on the cover and sculpt/remove the amount of clay I want gone. I can make the walls of the diffraction lens just thick enough to make it rigid and durable, yet light weight and easy to work with.

I also won't have to use so much of that expensive resin. Then I can set up the lid, drill holes for pouring the resin into the mold, and do it that way. When it sets up, just remove the lid, and pull the resin shell out of the mold.

Once it is removed, I can glue the two halves together. And if I need to, I can make a small hole and fill the cavity with styrofoam, in order to give it more strength. Then just fill up the holes and finish.
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Old 11th February 2012, 02:14 PM   #255
John L is offline John L  United States
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Quote:
Originally Posted by Carlp View Post
John,
I have SOME experience with epoxy and fiberglass having built a cedar-strip canoe and a few other smaller projects. Ask away (here or PM) and I'll see if I can help. If it's fumes you're worried about, check out MAS epoxies (MAS Epoxies - Easy Epoxy Resin & Adhesives. Marine Epoxy for Boat Repair & Boat Building; Automotive Epoxy; Epoxy for Woodworking, Signs, Surfboards, Other. New: Eco-Friendly Acetone Replacement, Non-Skid Repair).

Also, I don't really understand your process here. You have green moulds to use for casting the diffraction lenses? So there's a cavity inside these moulds into which you want to pour plaster? Or are you forming around the outside of these and somehow using that? Are you concerned that if you fire the greenware it'll change dimensions? Sorry for being dense, but I just don't get it. A little more explanation would help.

Thanks
Thanks for the link. I'll check it out in a few minutes.

As for the mold, I am going to use the plaster only to make the mold. I have constructed a plywood frame for both halves already. Let me go get some pictures. But first I will have to upload them into my Webshots account.
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Old 11th February 2012, 02:43 PM   #256
John L is offline John L  United States
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Here are some pictures.

Bottom section base

Click the image to open in full size.

Click the image to open in full size.

I just keep building up the inner portion, so as not to waste so much plaster.

Click the image to open in full size.

Click the image to open in full size.

Click the image to open in full size.

And I just do the same thing for the upper section.

Click the image to open in full size.

Click the image to open in full size.

Click the image to open in full size.


I know things look a little bit rough, but I figured that would made the plaster frame more secure inside the plywood. I'm thinking about adding some screws to the inside of each shelf in order to keep everything in one piece. If this works out right, I can store them when they are finished and possibly make more when/if I want to build another pair.

I really don't particularly like walnut, for some reason, and wish I had gone with a nicer veneer, that had burls.
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Old 11th February 2012, 03:33 PM   #257
John L is offline John L  United States
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Quote:
Originally Posted by Carlp View Post
John,
I have SOME experience with epoxy and fiberglass having built a cedar-strip canoe and a few other smaller projects. Ask away (here or PM) and I'll see if I can help. If it's fumes you're worried about, check out MAS epoxies (MAS Epoxies - Easy Epoxy Resin & Adhesives. Marine Epoxy for Boat Repair & Boat Building; Automotive Epoxy; Epoxy for Woodworking, Signs, Surfboards, Other. New: Eco-Friendly Acetone Replacement, Non-Skid Repair).

Also, I don't really understand your process here. You have green moulds to use for casting the diffraction lenses? So there's a cavity inside these moulds into which you want to pour plaster? Or are you forming around the outside of these and somehow using that? Are you concerned that if you fire the greenware it'll change dimensions? Sorry for being dense, but I just don't get it. A little more explanation would help.

Thanks
Is this the same type of epoxy as that at " masepoxies.com "? They both look close to the same thing.
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Old 11th February 2012, 07:27 PM   #258
mightym is offline mightym  United States
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Glad to see you back at work on this project.

Another source of high quality epoxy, at reasonable prices is Raka (Raka, Inc. 772-489-4070, Epoxy-Fiberglass-Carbon-Kevlar) If you are looking for a local supplier check the phone directory, there should be a supplier locally in an area as large as yours...

You can also stretch epoxy resins by adding material to the mix. the material only needs to be granular in nature, and non-reactive to the epoxy. An example would be the Kenwood Turntables like my KD-500 made back in the early '70's with quartz or granite in an epoxy matrix. I believe some of the modern countertop materials like Corian are a similar matrix.

You may want to consider a vibratory table with the molds you are constructing. You may end up with unwanted voids from air bubbles otherwise...

Is this the project in which you'll use the Pioneer " Coax's " you built?

Another alternative to plaster would be to make a mold negative with Fiberglass, or FRP, and then make a positive mold cast from the mold negative. I've experience with building Race Car bodies by a couple of different methods using glass mesh with both epoxy and styrene monomer resins. It's possible to reproduce quite complex shapes when properly applied. I'd be glad to help if I can.

Keep going while you've got traction! I'm anxious to see this project completed too.

John
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Old 11th February 2012, 08:00 PM   #259
John L is offline John L  United States
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Quote:
Originally Posted by mightym View Post
Glad to see you back at work on this project.

Another source of high quality epoxy, at reasonable prices is Raka (Raka, Inc. 772-489-4070, Epoxy-Fiberglass-Carbon-Kevlar) If you are looking for a local supplier check the phone directory, there should be a supplier locally in an area as large as yours...

You can also stretch epoxy resins by adding material to the mix. the material only needs to be granular in nature, and non-reactive to the epoxy. An example would be the Kenwood Turntables like my KD-500 made back in the early '70's with quartz or granite in an epoxy matrix. I believe some of the modern countertop materials like Corian are a similar matrix.

You may want to consider a vibratory table with the molds you are constructing. You may end up with unwanted voids from air bubbles otherwise...

Is this the project in which you'll use the Pioneer " Coax's " you built?

Another alternative to plaster would be to make a mold negative with Fiberglass, or FRP, and then make a positive mold cast from the mold negative. I've experience with building Race Car bodies by a couple of different methods using glass mesh with both epoxy and styrene monomer resins. It's possible to reproduce quite complex shapes when properly applied. I'd be glad to help if I can.

Keep going while you've got traction! I'm anxious to see this project completed too.

John
Thanks for the encouragement. And yes, its the one with the Pioneer BOFU.

Regarding filler/aggregate I have done considerable reading on related things, and one of the recommended fillers what seems to have special qualities is crushed pecan shells. I love pecans and may want to go buy a bag of pecans in their shell, just to use them. I can see one advantage to them in that if you needed to sand the product, that could be done easier. I'll want to do that anyway, since I will want to paint the finish and rough surfaces will make for a better adherence.
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Old 11th February 2012, 09:08 PM   #260
Carlp is offline Carlp  United States
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Quote:
Is this the same type of epoxy as that at " masepoxies.com "? They both look close to the same thing.
I don't honestly know as neither provides much in the way of chemistry. MAS had developed a very unusual (at the time, early 1990s) epoxy resin which had low off-gassing and didn't form an amine blush (which with other systems had to be cleaned with acetone!). It was a boon to boat-builders who didn't want to use acetone and often developed sensitivity to other resins. I met the chemist who developed the resin and the company as they were doing their initial marketing and he convinced me to try it. I cleaned my boat with acetone after the fiberglass layup (he said it wouldn't hurt but wasn't needed) and my next layer failed to cross-link with the layer beneath, causing peeling. He and I had some discussions which, I think, led to some reformulations which, because I had all I needed of the first formulation and haven't done any projects since, I didn't look into it further.

BTW, my brother in law does some plaster casting, and he often casts with multiple thin coatings where expansion and heating might cause a problem. He applies the plaster, shakes it vigorously while it does it's initial cure to coat evenly, then lets it cure a little more before adding more plaster. I can ask him about how it might be done if that's of interest.
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