Wednesday, August 24, 2011

New build: "Zoomie" P-51D

Recently, TRF user Daddyisabar posted a thread on his Estes SpaceShipOne to P-40E kit bash.  I am a big fan of the SpaceShipOne as a subject for kit bashing (ref. Goonball XL5, SpaceShipSqrt(-1)).  I loved the P-40E and had another SpaceShipOne.  So, I decided to try a P-51D.  Daddyisabar coined the term 'zoomie' for a 'goonie' version of a scale aircraft.  I call mine the Zoomie P-51D. (So original, eh?).

Here's my progress to date:

The first photos show the wings and other fin-like objects.  I patterned the general concept after the P-40E and even the Semroc Gee'hod.  I first roughed them out based on drawing of the P-51D that I found on the Web.  I laid these out on a rough profile of the SpaceShipOne's body.  All the components, except the lower 'air intake' are cut from dense 1/8"  balsa and the intake is 1/4" balsa.  I thought about using the thicker balsa for the cockpit too...but didn't.  The wings are 2-part because I only had 4" wide stock and the whole wing wouldn't fit with the proper grain orientation.  All wing/fin parts were laminated with full page label stock. The edges were treated with thin CA and minor imperfections were filled with Fill'n'Finish. Oh, yeah, there will also be landing gear (large half circles) on the wings.  I may use a centering ring cut in half.

Based on my prior experience, stubby winged rockets require a good bit of nose weight.  My XL5 is 18mm but requires a D13, D21 or D24.  The SpaceShipSqrt(-1) has a 24mm mount, and can fly on a C11 or D12.  For this latest model, I thought a 24mm mount was the way to go.  I didn't need that nozzle anyway.  The photo to the right shows the motor mount.  I expanded the center holes in the stock centering 'rings' and positioned them per the instructions.  On the front, you can see an I Build Rockets plywood shock cord mount.  This serves as a motor block and an attachment point for a steel leader.  However, having built this 'on the fly', there is a problem.  Mounting this mount so close to the motor could result in an over pressurization. That is, the mount might be ejected.  I'm still mulling this issue over.

The final photo is the in-progress tail cone.  I just roughed out the rear opening.  Once the mount is installed, I'll seal the rear gaps with SuperFil epoxy clay.  One thing I learned from the Sqrt(-1) is that 24mm ejection charges are tough on plastic cones.  The upper ring on the SpaceShipOne leaves almost half of the cone exposed - not good.  I think I'll make a card stock cone to fit between the inside if the shoulder to the upper ring.  That should keep the hot gasses away from the wimpy plastic.