We use a layer of glass and epoxy straight onto the foam ++++++++++++++++++
There you go now Phil, thank you. In the spirit of the purpose of this group, it would be great to better understand the differences /pro's and con's (and potential) of these two core materials as may benefit KR builders. I need to stop talking and start building, so it would be fantastic for me to establish that I can safely use polystyrene as a competent core material in a 6 to 10mm sandwich. My intention is to follow the original Dr. Dean Collette (sp) route (more recently used by Eduardo Barros). A KR fuselage built in a sort of Vision style. In short, a KR2S fuselage (stretched and widened with rounded corners at the bottom) made up of a framework of 3/8" sq spruce and filled in with the core material. The core material is sanded (hot-wired) flush to the wood frame - then glassed inside and out. The spruce frame work provides the shape and the foundation for a straight (true) fuselage. The glass skin is structural (like in a Vision) and the imbedded spruce framework is not expected to contribute to the strength, but will surely enhance the integrity of the core material in shear - it is now effectively also a latticework of stronger core material with a high shear capability. It will cost a small fortune importing (airfreight) Last-a-Foam or Divinicel and I have very little confidence in the regular 32kg/m3 poly-u that is available (for reason mentioned in the previous posting). If polystyrene will do the trick, I can "slice" it to any sheet thickness I prefer with a hot wire and a 10mm sheet will take a reasonable radius and (with great respect to all) step around the classic KR box shape) I am not alluding to a mouldless construction where the foam is used purely as a non-structural form - I hope to achieve a competent sandwich structure. Even the wing skins (similar to 56ML) can be a true sandwich composite. Take care Steve
