Forums Modeling Technical Modeling
  • Topic: Hale & Norcross Dump Trestles

    Back To Topics
    (0 rates)
    • April 16, 2018 6:04 PM EDT
      • Vail, Az
         
      • Posts
        3,535
      • Thanks
        267
      • Thanked
        292
      • Reputation
        Well Respected

      I dislike the foam ... it never goes where I want and worse; a quick finger solves that only to be real sticky .... it won't wash out of those nice pants either ... ask away;  I don't know nuthing no how.

       

       

      ____________________________________

      John

       

      The older I get, the less I know, please don't make me prove it.

       

       

    • April 16, 2018 7:30 PM EDT
      • Shawn carries, A Purse 02B12,
         
      • Posts
        11,964
      • Thanks
        564
      • Thanked
        444
      • Reputation
        Well Respected

      I like Plan B because I feel like I need the pill after last night!....remember there are two types of blow foam.....http://www.finehomebuilding.com/2010/04/29/spray-foam-sealant-latex-vs-polyurethane........I personally would go with the latex for numerous reasons.

      1..It has an easy learning curve to play with and I think it will give you the smoother look you are after.

      2..If you don't like it I'm thinking it would probably adhere less to the acrylic (or whatever material you cut)

      3..When it expands it's not like an ice jam pushing on a bridge (which the Great Stuff poly will do) 

       

      Side notes if it were my build

      1...I would probably throw some waste rock/sand in while adding the foam what ever color you think it might be.

      2...I would spray the acrylic with Pam cooking spray as a release agent .....that way if it sucks you can take a trowel and remove it.

      3...Pertains to 2 ....if you do like it then you have a spray foam module you can glue back into the structure.

       

       

      Just my thought's and thanks for sharing what your having Cliff

       

       

    • April 17, 2018 10:55 AM EDT
      • Strattanville, PA
         
      • Posts
        1,228
      • Thanks
        132
      • Thanked
        65
      • Reputation
        Well Respected

      Cliff,

      Oyne word of caution on the spray foam.  I used it to make a sizable nose cone for a model rocket once. It was roughly 10” x 4” diameter.  I sprayed the chunk then turned it to shape.  A few days later when I came back to it the start applying a hard shell to the outside, I noticed some significant shrinkage.  It was bad enough that the cone could now slip down into the tube.  I threw it out and bought some stiff white foam (it was meant for sticking fake flowers into) from the craft store and started the process over.

      For you maybe the MS will hold it’s shape even if the foam changes beneath?  I guess it depends on quantities and strengths of each. Just wanted to let you know of s possible snafu.

      ____________________________________

      forum sig

    • April 17, 2018 7:19 PM EDT
      • Highland, Maryland
         
      • Posts
        1,019
      • Thanks
        230
      • Thanked
        161
      • Reputation
        Well Respected

      David Maynard said:

      Ah, when you designed the "ribs", didja design them 1/4 inch under, to compensate for the magic sculpt? I like the foam idea better, although it will be a bit messier. Use the great stuff that doesn't expand as much, there are 2 kinds, that way you don't have to trim off as much, and it will be denser, offering more support. I do not know how well the MS will adhere to the foam, so you might want to put score marks into the foam so the MS has something to grab onto. Of course if you are carving the foam, you will already have knife makes in the foam, so disregard my last statement.

      Hi David,

      Yes, the ribs are all set inboard by 1/4" from the intended surface.

      Thanks for the tips, I'll look out for the denser stuff, and do some experimentation.

      Cliff

    • April 17, 2018 7:50 PM EDT
      • Highland, Maryland
         
      • Posts
        1,019
      • Thanks
        230
      • Thanked
        161
      • Reputation
        Well Respected

      You guys have given me a lot to think about, and that's what I wanted. Thanks!

       

      The last time I used spray foam was 20 years ago, so it's not surprising that variations are available. Seems like "Great Stuff" is the usual product. Randy, yeah, I don't want shrinkage, that would defeat some of the purpose. Thanks for telling that story. Maybe there's a product that's higher density, less expansion (as David M said), and no shrinkage.

       

      After reading some (Rooster, thanks for that link), I don't think I want the latex. Rooster, I want this stuff to really stick, otherwise the (rather expensive) Magic Sculp might be compromised. Also, the module is getting pretty heavy, so I'll need to keep any real stone products to a minimum (but sand in the top coat of paint over the MS would be good). 

       

      My hope is to find a cheap spray foam product that sticks well to acrylic, is readily carveable, is reasonably dense, and doesn't shrink.  I'll try to contact Dow for a recommendation, but please feel free to make your own. Here's the GS product line, 

       

      http://greatstuff.dow.com/product/index.htm

       

      You bet,John, yes, it's messy! Definitely needs careful application, and a lot of carving afterwards. 

       

      Thanks all,

      ===>Cliffy

    • April 17, 2018 9:03 PM EDT
      • Shawn carries, A Purse 02B12,
         
      • Posts
        11,964
      • Thanks
        564
      • Thanked
        444
      • Reputation
        Well Respected

      Cliff....you forgot side note 3 and looking forward to what you come up with Dr Cliffeyl and Mr HIDE

    • April 20, 2018 7:27 PM EDT
      • Highland, Maryland
         
      • Posts
        1,019
      • Thanks
        230
      • Thanked
        161
      • Reputation
        Well Respected

      Ahh, yessss... Side Note Number 3. Yes indeed, I'd somehow overlooked that in my evil plan....

      Bwoohahahahaha!

       

       

    • April 20, 2018 7:32 PM EDT
      • Highland, Maryland
         
      • Posts
        1,019
      • Thanks
        230
      • Thanked
        161
      • Reputation
        Well Respected

      David Marconi,FOGCH said:

      Micro Balloons cliff

      https://www.alumilite.com/store/p/957-Microballoons.aspx

      This is only one there are others

       

      Hey 'Wood,

       

      You bet, microballoons are great for making otherwise solid resins have micro-voids, granting them less density and therefore (maybe) buoyancy. But for regular aerated foam (vs. solid resin), which already has the voids, they would be counterproductive I think. But thanks for the idea; and I'm happy to be proven wrong! 

       

      Cliff

      This post was edited by Cliff Jennings at April 20, 2018 7:37 PM EDT
Forums Modeling Technical Modeling

    Icon Legend

  • Topic has replies
    Hot topic
    Topic unread
    Topic doesn't have any replies
    Closed topic
    BBCode  is enabled
    HTML  is enabled

Add Reputation

Do you want to add reputation for this user by this post?

or cancel

Ads by Google