Friday, January 7, 2011

Engine Giver

OK, "slight" change of plans. ;)

Here we are in the new year again.. not much has changed.. but on the other hand, a lot has.
I've been rethinking the Mosi power plant, and doing some wing & tail feather work as well.

Bottom line: the 4A032 engine seems a little too small to provide a comfortable climb rate margin at the density altitudes at which I want to fly the Mosi... it'll be operating out of a 5,000 ft. elevation home airfield, hopefully to go up to 15,000 ft. on occasion, in the summer months.. this scarcity of atmospheric oxygen leaves the "world's smallest flat-4" in the "inadequate power" category file... yeah, it would get airborne, but the climb rate would be underwhelming.

So, I've decided to switch to the 2A042 military surplus engine. It's a flat-2 (AKA Opposed twin, AKA Boxer twin) with 42 cubic inch total displacement, 21 cubic inches per cylinder.. 3.00 inch stroke, 3.00 inch bore. See 2A042 Yahoo Group for more details: http://groups.yahoo.com/group/2A042/

Empty weight should come in at around 80#.. the final number depends on many details.. (ignition, starter, battery, carburetor, engine mount, oil pan mods, etc.) . So, with the somewhat heavier engine hanging on the nose, reducing tail weight is not as big of an issue.. getting the CG right looks easier (on the other hand, nothing is as easy as it seems). The stock Moni cowling will have to be modified, as the 2A042 is too wide to fit in as is, but a couple of side bulges might look kinda cool anyway, so no worries !! ;) The engine I'll be using will be here in a week or so, and I'll post pictures ASAP. The right-size propeller looks to be around 40-42 inches in diameter, with 32-36 inches of pitch.

I'm still planning to go with tricycle gear, Y-tail, and wing span extension panels. .. more to come!