Scratch-built 1/96 Virginia Class - Pete's second boat

[pirate]

Mermaid,

That's precisely why I used

Mermaid,

That's precisely why I used the urethane rubber...cost.

I got 2 gallon kits of Por-a-mold hard (1 gal. catalyst, 1 gal polymer) from Blick Art Supply out of Chicago for around $68 U.S. Haven't checked the price lately. Use the hard if you have long walls because the soft and medium will fall in on themselves if you don't have the mold keyed well to the strongback properly. But if you have a lot of undercuts, the medium works well. I've not used the Thixotropic. That brushes on instead of poors and doesn't run. Made for actually copying architextural details on a building so it can be applied upside down and not run off.

www.dickblick.com

http://www.dickblick.com/zz335/08/

You need the Synlube 531 release agent too.

Pete

[Guest]

looks very nice

looks very nice

[mermaid]

Thanks Pirate. The price sure

Thanks Pirate. The price sure beats that of RTV!! If possible, I would like to use Kevin McLeod's (!/96 Oscar) technique in making my moulds. However, due to the larger ize of my hull, I will be obliged to make the strong back from GRP instead of plaster. If I understand you correctly, you are saying that it is possible to use the Poramould urethane rubber in pretty much the same way as one might use RTV. Would it be possible to place a thin medium urethane skin coat over the plug and then build up the glove thickness with the thixotropic material just as Kevin did??
Does urethane rubber adhere to itself? Is a release agent required over the plug? Just as an aside, I was very impressed with the plans that I saw on the pix of the Virginia build. Did you draw them and if so, which program did you use?

[stark]

First off, THANK YOU PETE,

First off, THANK YOU PETE, for sharing your technic & materials !

This should provide the info needed for all to go about making their own models. I plan to give your material a shot, and have a question.

Does your Por-a-mold handel heat for spin casting White metal? Do you know it's the tear strenght?

Have you had any shrinkage, and how many pulls have done with it?

What are is the other material in the mold , are you placing it in there for fill, " the yellow/ blue block" so you use less material?

What will be your next boat?

When will you due a Non Nuke Boat?

And I guess you don't play pool anymore, to risk setting up work on the table!

Brian

[anonymous]

Pete,

80 bucks for two gallons

Pete,

80 bucks for two gallons is amazing. This is real good for making case molds of big hulls.

Thanks for sharing!

Wow! 80 bucks for 2 gallons!

Steve

[pirate]

Guys..a few words of caution

Guys..a few words of caution with the urethane Por-a-mold product.

Mermaid, any of them other than the thixotropic will flow like water until set up, so pooring on a thin coat first will be very thin. You may need to do this a couople of times before building it up with the thixotropic. I haven't worked with the thixotropic, but I assume you could start with that, and use it alone in multiple coats to get the thickness you want.

This stuff sticks to almost anything, including itself. So use the Synlube 351(?) they recomend for it as a release agent. But it still doesn't stick to clean melamine board. I use that a lot as my base. Whatever you use needs to be sealed and release coated.

Drew the plans with the Macromedia Freehand drawing program. I'm a graphic artist as well and that's what I use for vector art in the computer.

Brian, Por-a-mold will melt back into a liquid under heat and goo up everything. Do not try to cast metal with it. It holds up fine to the exothermic reaction of polymer resins like polyester and epoxy, but not metal.

Shrinkage has been minimal,and it's much more durable for production that RTV. I've pulled more than 20 times easy with this stuff and still kept going. Tear strength and shrinkage specs are available on the website I believe.

DO NOT TRY TO USE ALREADY CURED PIECES OF OLD MOLDS FOR FILLER! I tried this on the first mold of my Virginia, and on the 3rd pull where the pieces were started showing up in the casting—bad. There must be different densities when made at different temperatures, or over time, because all the little pieces seemed to migrate to the surface and made impressions in the casting. I was really bumbed because that cost me another $130 dollars to make a new mold, and coountless hours to get the master back in shape to make it. I almost cried—almost.

The yellow blocks are from the first mold with the old urethane pieces as fill—guess it changes color too. The blue are wedges made of clay to leave an easy place to find the seam between the two halves of the urethane mold. Sometimes it sticks to itself even with the mold release and it's very hard to get it started to come apart. This makes sure there's a place where the two halves never touched each other so you can start aerarating them here.

I'm already doing some retooling on my Virginia Class now. People keep asking for an Ohio Class, so maybe that, but as an SSGN. I also want to make that little two-man sub the Army used to retrieve Red Stone Rockets that I showed you—that would be non-nuke. I've also thought of doing the DSRV Mystic for myself some day. FX Models has a fantastic version of that. Unless I got laser etchers and cutters I couldn't even begin to come close to making one as nice as that. As well, I like the challenge of trying to make models of boats that aren't out there yet. Who knows.

And yes Steve, $80 bucks. Can't touch RTV for anywhere near that. Starving artists can't afford that expensive stuff.

One last thing on the urethane. It has a short shelf life of about 6 months. The way it works is that once opened to the air, any moisture will start filling the links on the un-catalyzed polymer chains. Then when you try to catalyze it there aren't enough links for it to connect and you get a runny, gooey mess. I haven't tried filling the bottles with another inert gas. That may help. You just have to keep moist air out of there. There's enough H2O in the air by itself that it will eventually ruin it, but trying to keep it to a minimum will only help it last longer.

Pete

[stark]

My kind of a reply

My kind of a reply Pete, Thank You. The stuff is a little scary, but when the time comes, I will try it. Like Steve said, the Price Elwood! The Price!

Look, the OHIO, she is dream doll for me, I love the boat!

I just today received the "Official Merriman Folder" on her, so this is a Big Help!! Thanks Dave!

I had mention to you before my building an OHIO too. My choice for scale is 1/144th, If this is your plan, or if you think I will be stepping on your toes, I will keep her to myself, as I have started a build.

You are a Vender, and I a want-a-be, so I leave it up to you, This Hobby deserves a good rendering of the OHIO, in any scale I believe. The only R/C model I ever saw was in 1/96th, and for me that is to big, but I am a weakling, and prefer a 30" to 60" boat!
Heck, that is all my wifes three cats can mush around on a sled

Brian

[anonymous]

Pete,

thanks man! This sounds like

Pete,

thanks man! This sounds like the perfect material for a case mold. Since it's so thin and easy to pour this would take care of Mermaid's worries about trapped air.

If you don't know how to make a case mold just holler!

Steve

[magpie]

This is fantastic work Mr.

This is fantastic work Mr. Pirate!!
You really know how to build a boat mate!
Jason

[pirate]

Thanks Jason.

Thanks Jason.

[Guest]

This and Kevin MC's build

This and Kevin MC's build are a real joy to read, very inspiring.

yours too Steve

[mermaid]

Thanks for the info Pirate.

Thanks for the info Pirate. Great stuff! I agree with U812 regarding pouring a case mould. Should work great. You said that the urethane rubber sticks to most everything. Would that include the inside of a carefully cleaned GRP strong back? If it adheres well enough, one could make the rubber layer quite thin and be able to pull layups without the glove popping out. Is that a possibility????

[pirate]

Mermaid,

I meant it stick to

Mermaid,

I meant it stick to stuff when contacted uncured, and then it cures—situations where you'd use a release agent.

Once cured, it won't stick to things except for normal rubber stickiness, so you'll need real good keys between it and your strongback to keep them in contact.

Pete

[pirate]

Albion,

Silent Hunter did a build

Albion,

Silent Hunter did a build thread of my Virginia kit on SubPirates.com. You should check it out.

[mermaid]

Dear Pirate. In the situation

Dear Pirate. In the situation with a case mould, The rubber would obviously be poured in an uncured state. I was just wondering wether the rubber, once cured, would adhere to the strong back's inner surface sufficiently well to eliminate the requirement for keys.
If not, would it be possible to coat the inner surface with some type of adhesive which would bond the rubber to the strong back?
I'm just exploring the options. Of course, if keys are required then I will incorporate them into the strongback.