- Oct 18, 2003
- Saline Michigan
What I am saying is that I doubt the dense egg crate of honeycomb sandwich will be lighter for a COMPLETE horizontal stabilizer than a more conventional COMPLETE horizontal stabilizer of the same strength.Hmmm, so you think the wing construction could be even lighter than the BV246?
The issues are several:
- The skin must to be built to some min skin sturdiness and thus thickness, which sets a min weight for that portion of the structure without regard for internals;
- The aft most web of the stabilizer must be sturdy enough to pick up elevator loads and distribute them over the stabilizer, which sets min weight for that portion of the structure without regard for the rest of the internals. This comment applies regardless of whether the hinge is several fixed hinges attached to the spar or is lengths of piano hinge fixed to one skin;
- The bonding of internals to the skin must be reliably achieved in production, which usually means a significant overfill of adhesive. In a conventional construction, this mass is moderate, but with a large faying area for the multitude of honeycomb panels, this weight could be substantial indeed;
- The bond joints must be resistant to crack growth under repeated load cycles. Bonding the edges of graphite composite to other thin sheets of graphite composites may induce cracking in the adhesive unless the adhesive volume is substantial.
Once you have a min gage skin and a min drag spar, the internals being proposed by Darkaero become largely superfluous.
Now, I do not contend that for their demonstrator, it was not the lightest scheme - it may well have been lighter than any other scheme for supporting the well distributed one ton load. Let's remember that their demonstrator did not have to contend with point loads from a deflected elevator at its limit loads, nor did it have to carry a reliable-in-production amount of adhesive bonding that large number of honeycomb panels to the skins, nor did it have to be reliably resistant to fatigue.