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Thursday, January 26, 2012

Foam Improvement

When all roads lead to foam, crash-proofing foam planes before entropy sets in is key.  Although I've never crashed a foam plane, I can only imagine how these tips might help:

 #1.  Don't pay too much

The first key to realizing the value of foam is not to pay too much for a foam plane.  While it is tempting to buy the colorful marketing on the box, remember that the plane won't look like the picture after a month or two of hard use.  If you can picture the plane worn, scuffed and patched up, and you still think it is a good deal, that's the right price for a foamie.


#2.  Get the good foam

Not all foam is created equal.  EPO foam is much stronger than EPP beer cooler or packaging foam, and it can be more effectively painted.  EPO foam is specific to steam molded model airplanes, AFAIK there is no other use for this particular cocktail of chemical reactions but permanently contaminating the Chinese mainland:


There are a variety of other types of RC airplane foam.

#3.  Price required upgrades into the deal up front

Some foam planes are so inexpensive that upgrades make sense right off the bat.  Cartwheeling a plane because the stock retracts are junk might cost more than $20 for a good set of servo-less retracts that are more fun to use.  Good motors are cheap and can make all the difference when flying a model.  A more appropriate battery or prop can make a big difference.

An RTF or ARF that bundles components that won't fly well or break quickly has an phantom price tag.

#4 Crash proof before flying

Non-negotiable lifesavers on foamies heavier than 10 oz:
  • Glossy clear mailing tape along the main wing(s) leading edges 
  • Glossy Scotch tape control surface hinges
  • Glossy Scotch tape leading edges of horizontal/vertical stabilizers
  • Add under-wing tip skids, e.g.:
    • Slice-in small thin sheet CF slats, parallel to tips
    • Slice-in small metal washers
    • Strip of glossy mailing tape
    • CA flat nylon zip tie
    • Add thin aluminum sheet or soda can material, cut to shape and attached using outdoor double-sided mounting tape
  • Add thin carbon fiber spars to fix structural vulnerabilities or  excessive aerodynamic flex
  • Add thin foam weather stripping along wing attach points to take up play 
  • Check/Secure cheapo plastic clevises or replace before flying
  • Check/Secure check all servos
  • Check/Secure any surface-glued control horns
  • Check/Secure the firewall and motor mounting points
Negotiable:
  • Add carbon fiber tail and wing wires to fly more squarely
  • Light acrylic gloss or dull spray coat to help seal painted, or especially unpainted foam
  • Glossy clear mailing tape to preserve common handling points
  • Add wider nylon or metal washers under all screw heads and wing attach bolts
  • "Glass" the inside of the plastic cowling and pants with smeared-thin Gorilla Glue
  • Add air vents to keep motor, ESC, and battery cool (exit area = 2x entry)
  • If motor is tightly insulated, add aluminum prop adapter and aluminum spinner as heatsinks
  • Glue entire plane as a single piece to avoid future play and to minimize flex
I say "glossy" tapes because the dull or magic/invisible clear tapes never seem to adhere well to EPO.


#5 Consider buying the airframe only

This can be a good build strategy to keep costs low and component quality high.

#6 Consider buying critical extra parts

Sometimes more expensive is cheaper.  Aside from discontinuation insurance, this can guard against isolated shipping charges for stuff easily worn out or damaged - battery hatch, canopy, landing gear, etc.    It is always a good practice to check if the store stocks spare parts for any plane.
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