[NSRCA-discussion] Back to pattern stuff

[Rcmaster199 at aol.com]

David, it's regular polystyrene foam of approximately 2# density and comes  
in a folded bundle. Each pleat is around 1/4" thick. Steve Maxwell told me 
about  this stuff and that it is called Fan-Fold. The negative is that the  
material comes with a polyester backing film which tends to make the material  take 
a set from bundling, etc. Its a bit wavy off the bundle. But a little  time 
with a sanding block and the backing comes off easily enough and material  
straightens out pretty much. The positives are that it is similar in feel to  soft 
balsa but sands a bit easier to a decent finish. It has a very  close cell 
structure that should take water based paint fine. It is surprisingly  stiff 
material yet resilient. 
 
The material should hot wire easily if more complex shapes are needed. Dean  
Pappas told me he has done that with this material type with good results. 
Lowes  sells the same composition in 2" thick 4x8 sheets in the insulation 
department.  So if you want really straight and flat stock, you can hot wire the 2" 
material  to the deisred thickness, and there would be no backing to worry 
about
 
I am using it in a conventional build with minimal balsa structure  
underneath. I believe that with a bit more structure, this material could build  a full 
sized pattern model for electric or gas. I intend to use silkspan over it  to 
form a stressed skin. The wing panels were very simple. I cut the correct  
planform and prepped by beveling the LE and TE to appropriate angles, and glued  
the LEs together first, forming a V. The next evening, with very light balsa  
structure inside, I brought the TEs together and voila. A few pins to hold 
the  skins against the balsa and its a very light and stiff panel. Perfect for a 
30  (eq) sized electric. I used a full depth 1/8" spar, which may be 
overkill, but  what the hell. There's also a bit of carbon in it in judicious places.
 
The landing gear will be simple carbon tubing with axles glued in. Planning  
to use DS281's in the beastie on DaveL's recommendation with the 770 rx
 
The final weight is projected at around 2 1/2 pounds where it should be a  
fine match for the A30 M16 Hacker motor. A real pocket pattern model
 
MattK
 
 
 
In a message dated 2/8/2006 10:02:20 PM Eastern Standard Time,  
dflynt at verizon.net writes:

So Matt, is this a polyurethane hard foam  that you can cut and sand for 
creating plugs?  What is the thickness of  it, and what is the density?
 
David

-----Original Message-----
From:  nsrca-discussion-bounces at lists.nsrca.org  
[mailto:nsrca-discussion-bounces at lists.nsrca.org]On Behalf Of  Rcmaster199 at aol.com
Sent: Wednesday, February 08, 2006 2:58  PM
To: nsrca-discussion at lists.nsrca.org
Subject:  [NSRCA-discussion] Back to pattern stuff



Using bluecor  foam from Lowes seems to work well. Shapes easily, is 
reasonably strong  material and serves to hold the reinforcing sticks well. Accepts 
foam  friendly ca and probond very well. I sanded the polyester film backing off 
 since I am finishing in silkspan and water based polyu paint.
 
Have the main  components of the small pattern job about done. Wing spans 46" 
with an area  of 470 sqin. Fuse length is 50". I'll post pics when I get 
around to  it
MattK





 
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