Conference vmszoo::rc

    I believe the blue foam used by modellers is that manufactured by
    DOW chemicals.
    
    As for whether insulation foam is OK, I would say it depends on
    the density. The blue foam is quite dense and a sheet of it is rigid.
    
    One important point if intending to hot wire cut unknown foams - the fumes
    can be noxious/lethal.

    	Regards, Andrew.

    Andrew,
    
    Thanks for the warning! I was unaware of the dangers from fumes
    - lots of fume-type dangers aren't there?
    
    By dense, I guess you mean the "little balls" (!) from which the
    foam is made are small?
    
    Any ideas on the coverings?
    
    thanks,
    
    Keith.

    Keith,
    
    Can't speak specifically to the various foams available in the UK
    but, here in the US, most/many colored foams are polyurethane foams.
    These are a chemical foam [as opposed to expanded bead types] and
    are used, primarily, for building molds/plugs for making fiberglass
    parts as they are impervious to polyester resins, most [if not all]
    glues, even to gasoline (petrol).  Polyurethane foam is light but
    almost "crumbly" when sanded and, over here at least, is usually
    green or brown in color, though I "have" seen it in blue.  I wouldn't 
    expect it to be very good for wings.
    
    The proven wing core material is the expanded bead type styrofoam
    of some [unknown to me] specific minimum density.  My advice would
    be to contact a fellow modeler with experience [and success] in
    cutting his own cores and follow his directions to the letter as
    *many* foams are unsuitable to our use and will fail, structurally,
    in flight...a revoltin' development if there ever was one.
    
    Adios cuzzin',	Al

    The Dow Blue Foam IS the insulation that housebuilders use.
    ( At least on this side of the pond.) There is also a pink
    foam, but I'm unsure of whether this is a Dow product or a
    different company. Anyway, if one looks at the blue stuff,
    you'll notice that you really can't see the "little balls"
    that the styrofoam is made off.
    
    The fumes that burning styrofoam emits are pretty much odorless
    and quite nasty as I recall, so be sure to use plenty of 
    ventilation. Another way to shape the foam is to cut to a 
    rough shape with a sharp knife and use a Stanley Sur-Form
    to round the edges. ( A sur-form is a small hand held tool
    which is a cross between a plane and a cheese grater. Looks
    like a plane from the top, but the whole bottom surface is
    like a grater. Bizarre, but definitly handy) Since the foam
    is so dense, you can sand it down fairly smooth after the
    you've done your best w/ the sur-form....
    
    The main drawback to the cut-shape-sand method is it's extremely
    messy, with static charged bits of blue foam appearing all
    over the place. 
    
    Doug

     ON THE SUBJECT OF FOAM WINGS:
     Practically any  type of covering will give you sufficient strength
     if the right type of foam is used.  I agree in that the easiest way
     to find the right  source/type  of  foam is to search out the local
     GURU and find what he  uses with success.  Adhesives that have been
     used in the past with success  have  been 3M spray contact cements,
     SIG  special  foam  wing  cements,  thinned EPOXY  (heavy  weight),
     SOUTHERN RC PRODUCTS SORGHUM, etc.  (EVEN WHITE  GLUE, WEIGH, WEIGH
     back when???)
     Coverings have been thin plywood, obechi wood, 1/16 balsa,  with or
     without  further  external  covering,  fiberglass,  some  low  temp
     iron-ons, etc etc.    Back  in  '62,  we even used "HUSKY COVER" or
     "CHROME COAT" heavy paper,  shiny  on  one side, dull on the other,
     stuff that might be used  for  display drawings, etc.  They came in
     "points" of thickness, like 14 point  or 9 point.  We got some real
     thin  stuff that did the trick.   Splicing  was  with  a  layer  of
     fiberglass  and  resin across the wing centerline splice,  or  even
     cotton aircraft rib-stitching tape.  I have used one  inch wide put
     on  with  titebond  and  none  of them ever failed.   The  greatest
     testimonial was at Denver when my radio failed at full bore and the
     ship went in a about a 60 degree angle, right into asphalt  taxiway
     at  Lowry  Field.    The ship was totaled, the engine had a useable
     glow plug  left  over (that's all).  The wing (covered with 9 point
     paper HUSKY COVER  and  attached with 3M Spray, spliced with 2 inch
     wide cotton tape held  with  Titebond,  and  with  one short 6 inch
     balsa full depth dihedral brace [no spars]) impacted the runway and
     left a full wingspan slight depression  in  the  asphalt  where the
     leading edge hit.  The impact line was easily seen, marked in white
     paint.   The leading edge was wrinkled a  bit,  but  the  wing  was
     INTACT- that is completely FLYABLE.  The engine, fuse,  tail;   ALL
     were  completely  destroyed,  but  the  wing  could have been flown
     again, immediately, if someone needed a wing.  DON'T ASKE ME  ABOUT
     THE RADIO!

    ERRATA::ERRATA......
    NOTE 382.5......
    The old brain cells are a-saggin'..... For what it's worth, this
    paper wing episode was 1966-67, NOT 1962!

    
    	I have a flying buddy who has built a Quadra powered spitfire
    of 1" blue foam.  The wings are covered with 1/16" balsa and the
    fuse and tail feathers are covered with iron on film.  The wing
    area and firewall have lots of plywood. He completely built it from
    scratch and it is one of the best flying planes at the local field.
     Don't be afraid of the blue foam.  However I don't think I would
    try it with a small plane because of it's weight.
    
    					TOM from PA
    

        Blue (also found in white sometimes) foam is Styrofoam. It
        can be safely hot wired with adequate ventilation. Density
        is usually 2 lb/ft^3.
        
        Urethane foam (tan or green) fumes are DEADLY! It is easilly
        sanded, and just rubbing it with your hand will crumble it to
        dust. It is shaped in this manner. It too is about 2 lb/ft^3.
        
        PVC foam (tan) also should not be hot wired. It comes in higher
        densities. 
        
        In the US, both Styrofoam and Urethane sheets are used for
        insulation. The styrofoam is often used between studs, and in
        other hollow areas. The Urethane stuff is usually foal laminated,
        and nailed to the outside. 
        

Also Tom, isn't the denser foam Urethane (sp) rather than
Styrene?  If it is, please be careful of the fumes when
cutting.  I think you know this, but in case someone else
doesn't...

I cut my first wing a few weeks ago and am now flying it.  I
really like the stuff.  Thanks to this note for some good info,
and I hope to contribute some info of my own when this war's over
(the start of the new FY). 

What's this "Blue" foam I keep reading about. I don't know if it is the same in 
the US but it is to be banned in Oz because of the CFC used in it's 
manufacturer.

John

You know John, I keep asking the same question myself.  The
locals tell me of great finds of this wonderful stuff at building
sites, but I've never seen it.  I've also searched the local
building supply stores...and building is big business in
Coleraddy...and found none of this famous blue foam.

One authority (Francis Reynolds in Model Builder) says its the
only foam to use, even for wings.  Others say to never use it
because its urethane.

For me, I don't believe it exists.  But, if I lived in the old
days, I would probably have been one of the fools up there in
Cripple Creek (Colorado) scratching for gold, so I keep my eyes
open...just in case!  

    Many years ago, one of the biggies in this RC business, name of ED
    IZZO, came up with the idea of FOAM WINGS, and stabs and anything else
    you can think of and he used BLUE FOAM. The stuff was HEAVY and STIFF,
    much more so than what is used today. Everything but the thinnest of
    stabs was CORED, and I mean MULTI-CORED. Otherwise your airplane became
    a boat anchor. I will try to find the original article in, I believe,
    MODEL AIRPLANE NEWS, and include it in this note series.

    Perhaps there is more than one kind of "BLUE FOAM".  I have a few
    sheets marked DOW - STYROFOAM BRAND - Extruded Polystyrene Foam.
    
    This stuff was bought at the local Channel store, in a pack of four
    sheets 3/4" X 24" X 48".  It is heavier and stiffer than the white
    foam, but I don't have the actual weight per cubic foot.  It cuts 
    very smoothly with a hot wire and is very resistant to dents.  

    

    White foam is a expanded bead foam which is a little harder to control
    the interal consistency of the foam, other than the white foam any foam
    that is EPS (Extruded Poly Styrene) foam is normally used.  EPS is used
    over white foam when it comes to using epoxy to glue on the skins
    because the EPS foam will not soak up the epoxy as will the Expanded
    bead type (If you look at Expanded bead you can see each foam bubble,
    like the foam that your radio came in).
    
    We in the Pikes Peak Soaring Society have used Pink foam (Foamular) and
    are now using Green foam (Amofoam) these are the foam you will see in
    the lumberyard, they are used for insulating cement foundation walls or
    also used in roofing before they put the tar and gravel over the top. 
    the Green foam is more dense that the Pink foam and about the same as
    the blue foam except the green we are getting is 2" thick vs 1.5" for
    the blue,  The blue foam is made by DOW and is usually the most
    expensive.  
    
    Any other questions
    

Bob,

Here a couple of references I've found helpful:

1.  Radio Control Foam Modelling by David Thomas  $15.95

2.  Designing and Building Composite R/R Model Aircraft by Jack Lambie  $16.95

You can get them from Zenith Aviation Books at 1-800-826-6600

I have them both but prefer Thomas' book.


                --|--             Happy (con)Trails!
                 (O)             
          _______/ \_______       Scott Cox

    I have a few questions about foam but first, a few definitions:

    A) When I say "white foam" I'm refering to the expanded bead foam
       that is commonly found in picnic coolers or packing material for
       model R/C radio equipment.  This type is made up of lots of
       little "beads" of foam.

    B) When I say "blue foam" I am refering to the closed cell extruded
       polystyrene.  (I know that it's available in other colors too.)
       This kind of foam is NOT made up of "beads" of foam, but does
       have lots of tiny "bubbles" throughout the foam.

    Both the "white" foam and the "blue" foam that I'm talking about may
    be safely cut with a hot wire assuming you have proper ventilation.  
    (I am NOT talking about urathane or PVC foam - these are DEADLY when
    cut with a hot wire.)

    Aircraft Spruce (and other companies catering to the homebuilt full
    scale market) only carry the "blue" foam [plus urathane and PVC]. 

    Their lightest "blue" foam is 2 lb./cubic ft. and comes in blocks up
    to 7" thick.  They claim the "white" foam is not strong enough for
    full scale use and thus, don't carry it.


    Now, for the questions:

    1) What is the lightest density "blue" foam that can be purchased
        and where can I buy it?

    2) What is the lightest density "white" foam that can be purchased
        and where can I buy it?

    3) Where can I buy "white" foam that is > 2 inches thick?


    A friend of mine has a project where the root of the wing is approx.
    2.5" thick and he wants to use the lightest foam possible.  "White"
    foam was specified in the plans but we can't find it > 2" thick. 
    He is willing to pay the $30. for the proper sized block of "blue"
    foam, but I think the "white" foam would be cheaper if we can find
    it in the right size.

                       _____
                      |     \
                      |      \                          Silent POWER!
      _        ___________    _________   |            Happy Landings!
     | \      |           |  |         |  |
     |--------|-  SANYO  + ]-|  ASTRO  |--|              - Dan Miner
     |_/      |___________|  |_________|  |
                      |       /           |     " The Earth needs more OZONE,
                      |      /                       not Castor Oil!! "    
                      |_____/

    call Sig or find a recent catalog. 15 years ago when I was doing some
    freehand foam cutting, I got my foam from Sig through the mail. They
    carried 3" thick blocks (I think it was 3x12x36) It used to be in the
    front with the bulk spruce and balsa
    
    Been many years since I've seen a Sig catalog. Maybe someone else in
    the file has a current one that they could check?