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This scratch-built cluster is for my daughter,
Jordan. It has a 24mm central mount and four outboard 13mm mounts.
The white stripes were added to the nosecone section to give it
a roll pattern (and a little character).
The upper airframe and payload sections are BT-50. The aft airframe is BT-60 slotted to accomodate four BT-5 outboards.
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Here's a closer look at the business
end. The intent is to either use plugged outboards or have them
eject. Only the center motor ejects the parachute; the four outboard tubes are plugged.
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Here's Jordan with her rocket July 4, 2008.
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In its original incarnation, circa 2000,
the payload section was clear plastic and used an Alpha nosecone.
There was no bulkhead in the bottom of the section. The ejection
charge heat on its first flight was too much for the plastic tube and caused
it to warp. That lesson taught me that Estes' clear plastic tubes
are not the same as the old mylar tubes used in kits such as the
Astron Streak. Those could handle the heat.
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This shot from the aft end shows the recessed ring bits between the outboard tubed used to hold everything together.
Lacking forethought, no burn string attach points were provided in the
construction of the rocket. So they must instead be integrated
into the center motor. Here, solid copper wire was used to form
two loops for attaching the burn string. Another option is to
glue the string to the motor case.
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The fairings for the outboard tubes were
made by laminating thin pieces of balsa. Making them thin allows
them to be contoured to the BT-60. Once all the layers were built
up, the fairings were rough sanded to shape. Then Fill 'n Finish
was applied followed by more sanding. Multiple passes of FnF and sanding were required.
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Here's a close but blurry shot of
ignition. The end of the burn stick is visible just above the
midpoint between the two yellow clips. Ignitor lead extensions
made with telephone wire are used in lieu of a clip whip, for improved
reliability. The wires are all resting above the burn
stick. This lets the wires move with the rocket at liftoff to
give any slow lighting motors the best chance of igniting.
From the pic, it appears the four outboards are all up to pressure, but the central is still coming up.
The fins are Redstone inspired.
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Here's yours truly trying to catch it under chute.
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1-10-2009 |