Hardpoints are rigid foam structures supporting motors, tail foils, electronics, and batteries. Stress relieving tapered stringers radiate from the hard points and attach to "crow foot" reinforced anchor points on the envelope.
Components are mounted on hard points of balsa and aviation plywood with sculpted foam fairings. A radiating structure of thin bamboo stringers spreads hardpoint loads across a large area .These stringers are arranged to follow stream lines and help to maintain operation with a limp gasbag. The blimp becomes semi rigid like a large rib cage is able to "breathe", that is adapt to varying gas pressure due to altitude change or leakage. Bamboo remains a unique structural resource that is usefully tapered, tough, stiff, light, and cheap. A more advanced substitute for the X-2 might be light carbon fiber fishing rod stock. (7/14/96)
While slight deflections of small control surface areas suffice for cruising speed maneuvers, large areas and aggressive deflections are needed for good slow speed agility. The large area/deflection approach requires special care in designing large, strong, and feather-light articulated mountings. An oversized monolithic elevon/stabilizer mounted on a tapered strake is the elected layout to make these trade-offs.
Initially foil sections will be straight edged from hot wire cutting and to allow for easy wrinkle free mylar and fiberglass tape reinforcement. Later versions will evolve more organic profiles with fancier construction.
The envelope is of the fluiddynamicly optimal streamlined "cigar" class first perfected by the Zeppelin company.(what is the technical name for this form?).
A big issue is using the Mylar gas bag as the primary envelope vs. as a liner for a fabric outer skin. At this point a naked Mylar bag with taped aft reinforcement and stiffened bow covering will be used and later upgraded if it proves inadequate. This approach will save weight, cost, and complexity in trade off with durability.
Operation in wet weather adds weight and threatens electronics.
Electronics bays are to be modestly weather proofed similarly to autos using gravity gutters and gaskets while maintaining ease of access. Loops and rolls in rain are proscribed. Drop ballast should offset modest rain/snow/ice loads. Outer envelope material should be hydrophobic (like Scotch Guard), if not waterproof, without adding much weight from fabric treatment.
Electronics and other sensitive components are to be housed in insulated enclosures. Electronic waste heat may suffice to inhibit condensation. Silica packs could help. Ram air venting might be useful if the electronic bays are too well insulated for hot weather operation.
Frost proofing- Low temperatures could affect electronics and embrittle materials. Insulated enclosures and anti freeze ballast are called for. Materials shall be documented or tested at low temps.
Want to build a micro-blimp? Instructions on fabricating envelopes are available.
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