Hangar Flying

Local Canard Groups => San Diego EZ Squadron => Topic started by: jrscuba1969 on December 03, 2010, 11:13:21 AM

Title: blue foam or pink for the body of the plane
Post by: jrscuba1969 on December 03, 2010, 11:13:21 AM

having a hard time finding blue foam around me in tx but have found pink
can this be used to build the long ez body?
we plan on buying the precut foam wings so it will just be the bodys made out of pink foam

Title: Re: blue foam or pink for the body of the plane
Post by: admin on December 03, 2010, 05:31:18 PM

Are you talking about Divinycell foam for the fuselage sides and bottom? Composite engineering is not a place for guesses and
I would not substitute any foam in the wings or fuselage based just on color. If you can find the technical details of the foam
 you are buying and feel qualified to make the call that it's properties are the same as the plans call for you might be able to
get away with a substitution. The total cost of foam from Spruce or Wicks is a relativity small percentage of the total you
are going to spend so why not get the GOOD STUFF? I've seen old Varieze's where the foam that Rutan called for was not
Divinnycell and the older Vari's suffer from a lot of de-lamination because of the lesser quality foam. I seem to  remember
the sheer strength of the Diviny is the reason Burt upgraded to that foam for the LongEZ.

You can use blue flotation foam for the nose and canopy where the plans call for urethane foam. You will pay a slight
weight penalty over urethane  but you will have better luck carving it. I've done four noses and three canopy's and
I much prefer shaping the blue flotation foam.

Title: Re: blue foam or pink for the body of the plane
Post by: LongEZDaveA on December 03, 2010, 05:35:06 PM

What is the source, and specifications of the pink foam?  I'd stick with similar properties of the specified foam.  I know the proper foams have changed colors at times over the years without significant changes to the physical properties of the foam.  When I built my Long, the fuselage foam was neither pink nor blue.  I wouldn't recommend deviating on the foam from what's recommended.

Title: Re: blue foam or pink for the body of the plane
Post by: Rick Hall on December 04, 2010, 01:03:50 AM

Whoa Trigger whoa I say!

The sky blue (or pink) is generally extruded polystyrene, and is not the same as expanded... the white bally stuff used in inexpensive foam coolers... but I digress.

Use the plans Divinicel where it's called for; like the sides, bulkheads, strakes, ...

It appears to be generally acceptable to substitute extruded polystyrene (blue or pink) wherever urethane foam is called for. Like the NACA scoop area, the nose, and the little PITA blocks when making the canopy.

The blue (or pink) insulation foam sheets you can get at the big orange store is kinda workable, but it's not the same as you'd get from Wicks or ACS. It has a microscopic bubble structure which is not the best to ensure good peel strength.

Spend the bux, it's not that much more in the big picture. Have wicks/ACS cut the sheets to 2' x 4' to save on oversize shipping, and include the 'drops'. I know Wicks is quite accommodating for this.

Rick

Title: Re: blue foam or pink for the body of the plane
Post by: go ez on December 05, 2010, 10:47:23 AM

Ref substituting urethane foam with styrofoam - this needs a BIG qualification.

This may be okay providing there is no chance (ie not just unlikely due to (say) total reliance on a pinhole free  glass layer separating fuel / fumes from styro foam)  of any fuel contamination. Fuel will instantly dissolve the styrofoam leaving no structural/anti-buckling support for the glass.

Areas to be especially wary of poor /unsuitable substitutions for called out urethane are in the spar, fuselage undercarriage reinforcements  and tank area.

Styro foam for the fuselage sides / base will carve great but the minutest fuel leak will land you in big trouble.

PVC/divynicel are impervious to fuel so that foam is ok from a fuel compatibility perspective but harder to carve & shape .

Title: Re: blue foam or pink for the body of the plane
Post by: Bill James on December 05, 2010, 09:03:14 PM

This has been said several ways, but to nail it down   - the best foam for a new Long EZ or VariEze fuselage is the LongEZ foam as specified in the LongEZ plans, per the plans. Order it from an approved source like AC Spruce.
Be aware that the fumes from hotwiring this fuselage foam can be fatal. 

Title: Re: blue foam or pink for the body of the plane
Post by: GlennBob on December 25, 2010, 08:03:19 PM

Bill,  not like the epoxy fumes that you mainline on ! !   ;D

Glennbob

Title: Re: blue foam or pink for the body of the plane
Post by: Bill James on December 27, 2010, 12:38:57 PM

All this time i thought it was epoxy fumes but it turns out to be ginger snaps and milk that do the trick   :)