You're right, I'm not building this one to play flying circus. I have no intentions of trying full deflection elevator tricks or the like at speed, with the possible exception of fast rolls by accident or intent. So my biggest concern was integrity around the engine mount (that is an awful big chunk of howling, thrashing metal up there) and a means to distribute the engine loads/vibes about the framework somewhat fairly.
Since I have an abundance of arrow shafts I made a cradle you can see in the prev pics, and wrapped the intersections with carbon tow and epoxy. One shaft runs outside the center ribs and aligned with the engine mounting plate, rearwards between the two short spars behind the engine, and ties in to the front half-spar. This is epoxied and glassed to the ribs though that does not show up in the pic too well. These short lengths of CF tube are very light and the stiffness is tremendous, plus the tensile strength is off the scale. The engine plate is a 3/8" thick laminate, and well trapped within the rib structure. If it comes apart I think the piece that hits the ground will be the engine and the center rib assembly as an intact unit, with Dacron bags of shattered parts flapping in the breeze on each side.
I plan to cover this with Stits fabric, so the whole airframe will be cocooned in a drum tight skin, and in addition I will epoxy-laminate the fabric to the exposed sheeting for skin toughness and abrasion resistance. It will be one tough little bird when together, I think. The torsional strength and stiffness should be impressive, it barely flexes as it is and also based on my #2 bird results. The fins will be carbon/glassed sandwich of 1/16" balsa - 1/64" ply - 1/16" balsa. The airframe in the last pics is up to 325 grams, and I weighed it a bit eariler with the engine and pipe together for a reading of 1050 grams IIRC. So even if I added a kilogram with tips, covering and radio, tank etc., which I think is pretty unlikely, it would end up at about 4.5 pounds. I know it will fly at that weight, launches notwithstanding, and land at reasonable speed. So I'm encouraged so far, and I hope to come in closer to my original 4 pound or so fantasy. Curses, just had an hour break to clean the kitchen and get started on dinner, and all I wanted to do was get back at it. I do enjoy those fleeting times when a project is interesting enough to me to be that absorbing. Two 2:30am nights are taking their toll though, I really should shut it down earlier..
And dinner seem lately to be chosen exclusively from our list of fast-fixeruppers for some reason.
Criminy, this thing might be done within a week at this rate. I better order my RNV now!! Dummy!
Oh yeah btw, dumb question, I've never owned an RC RNV and I know you have one CP - does/can the RC RNV completely replace the existing needle, as in act as the primary needle valve, or are they meant to modulate an existing needled assembly? And are they free enough for a strong micro or a mini servo? I probably can find this out on their website but hey, I'm here and I bet you read your instructions already.
MJD