|
opjose -> RE: Spitfire 60 engine offset? (1/27/2007 10:56:13 PM)
|
Nice job.
A 5mm difference is not going to be noticible in a Warbird IMHO.
I normally move the C.G. back anyway on many of my planes to get a bit better response and less of a nose down tendancy when flaring... of course you do not want to go TOO far...
The offset to the left is used to compensate for right thrust.
2-3mm is a pretty low offset. I don't have this model... (but after seeing yours... I just might)... but that sounds like you have LESS than 2 degrees of right thrust, so everything sounds about right.
Raising the engine normally adversely affects 3D planes to a small degree.
When the engine is higher than the centerline, there is a more (but slight) tendancy for the fuselage to move out of the flight line during a roll.... e.g. rolls are not quite as axial.
A high dihedral warbird has this non-axial roll tendancy anyway, so you would not see any effect, especially since the 3/8 difference is SO small.
Many people also overstate the tank to carb values... remember this is most applicable when the engine is idling on the flight line to prevent siphoning... if it were a huge problem in flight, we'll you could forget downlines and uplines and 3D would be a mess without a pump, etc... ...tank ABOVE engine in downline... tank UNDER engine in uplines...
Another thing that is often overlooked with these warnings is that with warbirds and other tail draggers, the nose of the plane is pointed UP further ofsetting the tank to carb position until the plane is just about to lift off.
Yeah there ARE reasons not to get the carb that far from the tank height, but don't sweat it so much, it's not as dire as the "sky is falling advocates"... usually the tank/height problem is brought up whenever someone is having problems with an inverted engine...
In this case, it's the engine tuning that needs to be properly adjusted, and it's almost NEVER the tank/height issue which is to blame.... I've been through this many times myself... so much so that I'm now pretty used to tuning the engines inverted and I tend to mount them that way for cleaner looks on almost all of my planes...
When the engine is inverted there seems to be a smaller tuning "window" IMHO which you must hit... once done and the engine broken in, though the planes fly fine.
|
|
|
|
