F.4.1 (Boom extrusion) Materials

[MattAdministratorAdministrator]

Just to add more information in case it comes up… We may not need to go to this level of detail, but maybe someone in the ODTC should know which spec(s) the spar extrusions comply with. Following is the list of Aerospace Material Specifications (AMS) for AA6061 (taken from U.S. DoD MIL-HDBK-5J) and the structural shape(s) to which each spec applies.
AMS 4025 – Sheet and plate
AMS 4026 – Sheet and plate
AMS 4027 – Sheet and plate
AMS-QQ-A-250/11 – Sheet and plate
AMS 4115 – Bar and rod, rolled or cold-finished
AMS 4116 – Bar and rod, cold-finished
AMS 4117 – Bar and rod, rolled or cold-finished
AMS-QQ-A-225/8 – Rolled bar, rod, and shapes
AMS 4150 – Extruded rod, bar, and shapes
AMS 4160 – Extrusion
AMS 4161 – Extrusion
AMS 4172 – Extrusion
AMS 4173 – Extruded rod, bar, and shapes
AMS-QQ-A-200/8 – Extruded rod, bar, shapes, and tubing
AMS-A-22771 – Forging
AMS 4080 – Tubing, seamless, drawn
AMS 4082 – Tubing, seamless, drawn
AMS-WW-T-700/6 – Seamless drawn tubing
AMS 4127 – Forging
AMS 4248 – Hand forging
AMS-QQ-A-367 – Forging

[MattAdministratorAdministrator]

After a little more searching, the HV-90WP possibly could be a hardness measurement. A hardness measurement can be used (in conjunction with other more complicated tests) to verify that an alloy is what it is supposed to be. So, maybe the HV-90WP is not an alternate alloy, but a qualifier for the specified 6061-T6 alloy. The specified designation (HV-90WP) is not one I have found, but it could be a format used in the 1960’s when the rules were first written, but which has since changed. There is a hardness designation called a Vickers Hardness, which is abbreviated HV, and it has a value of 107 for 6061-T6. Maybe one of the class graybeards has some insight.

[MattAdministratorAdministrator]

For more on the Vickers Hardness Test see link at: Vickers Hardness

If this HV-90WP designation refers to a Vickers Hardness test, the 90 and the WP codes are still a mystery.

But, another way to consider this is since the boom (and mast!) must be obtained from a licensed spar maker, why do we need this requirement at all? These requirements should be in the super secret Etchells Builder’s Specification.

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