Hello Steve,
Would like to thanks you and all the people had answered to my question.
You are right, every builder has it's own best technique, but all together
will form a more complex answer.
I now all the negative and positive sides of polyU and styrofoam.
Also I agree with you in that styrofoam is much easier to work with
without loosing strength properties. The only thing I wasn't sure just of it's
very tight cell and as a result the bonding properties. But now I feel
I could use this foam without problem, on a large area bonding properties
should be OK. As about your link to whisperaircraft, it is amazing for me,
they are using styrofoam which is formed from a small heated and pressed
spheres. I always was thinking that it is not a suitable material, but it seems
I was wrong.
In fact in bonding characteristics it is much better than extruded one, but
there should be used a lot of micro to fill in all the gaps. Should say very
nice plane and clean workmanship.
BR,
Alex Birca,
Moldova
-----Original Message-----
From: krnet-boun...@mylist.net [mailto:krnet-boun...@mylist.net] On Behalf Of
Stephen Jacobs
Sent: Wednesday, June 16, 2004 10:04 AM
To: 'KRnet'
Subject: KR> Foam type
Here in my country (Europe) the only available foam for me is Dow blue extruded
Styrofoam.
I am afraid about delaminating
+++++++++++++++++++++++++++
Hello Alex
You are getting a good response to your question. Some of the information will
conflict as each person gives you what they believe is best. I suspect that
you may be more confused after this then you were before.
I have been using these products for 20 years (30 years for Styroam
/polystyrene)
My contribution
The negative side of blue foam is:
a) Fuel will dissolve stryrofoam.
b) Blue foam releases harmful gases when it burns.
There are solutions to both of the above.
Other than the above I firmly believe that blue styrofom is as good as polyU in
every respect (or better) provided that you understand it and use it to its
best advantage.
Most KR's are built with a "single sided sandwich" using relatively thick
chunks of polyU foam. Full attention is given to the outer surface and little
attention is given to the inner surface.
Have a look at: http://home.hiwaay.net/%7Elangford/swings.html
The builder makes every effort to remove unwanted (surplus) foam from the inner
surface and then provides a glass skin on the inside - thus a true sandwich
construction. This builder uses PolyU (no problem in the
USA) but you can do the same with your blue foam and achieve the same results
with a THINNER core material if necessary.
I suspect that Mark L is using material of about 1kg per cubic foot, but you
can use blue foam of double that weight (4lb /cub ft) but cut it to half as
thick - and still be smiling. You can also cut your foam with a hot wire (I
regularly do) provided that you take every precaution NOT TO BREATH THE SMOKE.
There is a particularly good KR web site where the builder used hotwired blue
foam wing sections (with weight reducing cut-outs) for the wings. I tried to
find this reference for your benefit, but I cannot remember where I saw it -
maybe one of the netters will know and tell us.
In the meantime - have a look at http://www.whisperaircraft.com/ website. I
think I am correct in saying that all of the work was done with Styrofoam.
Dene Collet (Port Elizabeth SA) is familiar with this project and may have
better information.
Take care and good luck
Steve J
Zambia
Askies"at"microlink.zm
