ORIGINAL: Rcpilet
ORIGINAL: branded
ORIGINAL: Rcpilet
I can't cover well enough to keep the helium trapped inside for any length of time.
Well, please revert to your H.S. Physics....When you add "anything" to a container, this time a wing cavity pf a given volume, you displace the air inside with that "anything".....
Given the geometry of the wing is fixed, you can either displace the air with spars/wing ribs/shear webs, or spars and foam....either way your filling the space with "something"...and yes, air does have a weight....
Cheers...
I concede your point. Air has weight.
But, your not acknowledging my point.
Air is lighter than foam.
I still like built up wings better. I think they are lighter. A foam wing is easier to repair though.
Yes, air is lighter than foam, but the point is that foam is
air plus solids and when given a particular wing planform, and finite volume, the foam is no heavier than built up structure by volume given the absense of traditional structure, eg, ribs, shear webbing, etc......
The fact is, with a given planform, when using a foam core you can actually reduce the sheeting thickness because foam has more structural strength than traditional "eggshell" construction.
If the plan calls for 3/32" sheeting for a builtup wing, you can use a 1/16" on a foam core wing....
The downside of a foam core wing is as I said, it's not for novices. There are assumed, or aquired skills, that not all have, not to mention some tooling such as vacuum pump and bagging equipment.
The fact is, if an experienced builder is given the task to build both, they will be nearly equal in weight; however, the foam wing will be completed in far less construction steps.