自制飞机乱弹二：关于泡沫材料

About foams... there are many engineering considerations and you
as the ultimately responsible builder/designer must make some
choices between price and proven qualities for aviation use.
Many different foams have been used at different
pricepoints in experimental aircraft and different levels of
"certifiability" as to their performance in various strengths and
longevity and resistance to solvents etc.
Ironically some users of the so called certified expensive foams
complain about consistent quality control so decisions are
hard to make. I personally like to review what sailplane manufacturers
are using. That group really pushes the technological limit toward
efficiency in a way that powered airplane makers forget or get
sloppy about because more HP can always mask poor engineering.

If you go to the FILES area at this yahoo site there are some
technical charts and graphs for the various foams used in industry
and certified aircraft.

http://groups.yahoo.com/group/Skypup-club/

Sometimes YOU have to make a decision as to what to use instead of copying
what someone else has used that did not do an evaluation but merely
copied someone else.

There are no structural engineering properties
numbers that are supported by the manufacturers of insulation foams.
These numbers in order to be accurate must be arrived at by your own
testing or someone other than the manufacturers that you trust.
Even still, the manufacturers insist that they have little obligation
to maintain a consistent quality control beyond their minimum
unpublished specs for internal manufacturing use. The other question
regarding insulation foams is will the structural properties
values... whatever they are be retained over a long life with
the possibility of various forms of degradation. Some foams
like vinyls have a solvent outgassing, suffer from fatigue
weakening due to vibration, or the synthetic materials/ plastics
simply age in the same way that some motorcycle helmets do and have
to be thrown away after a few years. The science of aging
in composites is the least understood and talked about aspect
and thusly the most avoided.

The other group of people who use and I think know as much or more
about foams are boat builders. There are many websites and manufacturers
who talk about composite boat manufacturering. Many of the foam
manufacturers will not discuss aviation use ...

Scott

> howard wrote:
> ----- Original Message -----
> From: howard
> To: Canard Group ; Cozy Builders
> Sent: Wednesday, November 09, 2005 12:35 PM
> Subject: about blue foam, which kind of foam you used in your plane?
>
> Hi Guys!
> http://www.dow.com/styrofoam/ap/china/index.htm is this the blue foam
> which being used in EZ canard building?
>
> I am very interested in some foam rib material, for now I design my
> plane; I have check some info about structure usage foam and fond two:
>
> 1 http://www.diabgroup.com/aao/a_products/a_prods_3.html
>
> One of flyfea which useing ladders as spar and fuselage seems used
> Klegecell as rib material. you can see it from here:
>
> http://www.fly5k.org/MEM/GaryPouchel/GaryGower1.htm
>
> (2
> http://www.rohacell.com/en/performanceplastics/rohacell/uebersicht.html?CFC_cK=1131428907000
>
> ROHACELL?? is a polymethacrylimide- (PMI-) hard foam, that is used as a core material for
> sandwich constructions. It shows outstanding mechanical and thermal properties. In comparison
> to all other foams it offers the best ratio of weight and mechanical properties as well as
> highest heat resistance.)
>
> I have asked the price for rohacell, it is realy expensive
>
> 12mm?—2500mm?—1250mm 117usd 0?€?031density
>
> 20mm ?—2500mm?—1250mm 141usd
>
> and
> 12mm?—2500mm?—1250mm 180usd
> 20mm ?—2500mm?—1250mm 216usd 0?€?51density
>
> But with the same strength , ROHACELL is just 2/3 weight (density) of the styrofoam
>
> But I do not know what kind of form( and the density) which been
> used by Invader and the > thickness of the rib;
>
> Is there anyone kindly cast a light on it?
>
> following is a reply from Steve @invader gourp
>
> Howard,

> Although the foams you mentioned would work in a 2 lb
> cu/ft density... they are too expensive and create a
> deadly poisonous gas when hotwired!!!
>
> The original 1980's Invader design used a white
> expanded styrofoam. Now the foam called for is the
> extruded polystyrene foam used typically as a
> insulation in house construction. There are primarily
> two different brands available ... Dow Blue Styrofoam
> and Owens Corning Pink Foamular.
>
> http://www.dow.com/styrofoam/ap/china/index.htm
> Something like Floormate 200 would be perfect.
>
> http://www.owenscorning.com/around/insulation/products/foamular.asp
>
> The Foamular 150 is your first choice... the Foamular
> 250 would also work. It's just a bit heavier.
>
> Good luck with your design...
>
> Steve
> Crooked River Ranch, OR
>
> Have fun!
> Howard
> http://www.wingchina.com