William Robison
Posts: 20269
Joined: 11/10/2002
From: Mary Esther, Florida, FL, USA
Status: offline
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Gentlemen,
I too have a Duellist under construction.
One of the questions I can answer easily, as this is my third twin. VMC considerations can be eased considerably by making the vertical fin and rudder larger. On my first twin, a scratch built semi-scale Tigercat, I looked at the 3-views, and seeing the engines almost halfway out the wings was struck with "Engine Out Terror." I made the fin and rudder 150% scale. Result: this plane has its VMC just barely above stall speed, even with the engines so far out on the wings. More weight in the tail helps the Duellist balance, too.
But I cheated a little on the engines, also. I brought the nacelles a little closer than they should be. The thrust lines, both engines have 2 degrees down thrust with the wing at two degrees positive. The left engine has no side thrust, the right has 2 degrees right.
Unless you have a calibrated eyeball and the 3-views in hand, these changes are not obvious.
What is the Duellist MkII? This is the one I can answer easily. Dave Platt was the designer of the Duellist, The MkII is his upgrade of the original design. I know, the plans from Pica don't mention Dave Platt, it irritates me. I think Pica should give him at least a little credit.
Yes, preferably dual aileron servos, AND MUST have dual throttle servos. Separate throttle control is required to use the EMS "Twin engine sync system." Costs $80 from EMS/Jomar, but cosidering the total we spend on a twin that's a small part, since I put one on my second twin I don't want to be without it on a twin. My first has a single throttle servo, I have much fun getting sync, and usually don't get it anyway. With the EMS box, so long as the needles are reasonably close the engines always sing a perfectly tuned song. Fantastic.
Fuel system. Twin #1 has isolated fuel systems, separate tank in each nacelle. Twin #2 has only one tank, in the fuselage at CG. It has two clunks in it, each clunk feeding one engine. The clunk hose for the right (critical) engine is just a hair shorter than the one for the left, This way if I overstay my aerial welcome the right engine quits first. I did not have confidence that the engines would draw reliably at that distance, and I didn't want to use header tanks. The engines are pumped. Used one Perry pump inside each nacelle, up tight against the firewall, the hose to the crankcase is only an inch long.
The incidences and thrust lines on this bird are all zero-zero, I wanted the inverted flight characteristics to be the same as upright. It worked. Almost. I built it with mid-wings, the wings are not tapered, so I put in seven degrees of dihedral to add upright stability. It is ALMOST undetectable when inverted, upright it's rock steady.
Hope some of this rambling helps somebody.
A Twin is never a SIN!
WLR
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