dan.pat.b(at)gmail.com
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 Posted: Fri Jan 29, 2010 7:26 pm Post subject: Input Needed on Engine Selection: 0-320 vs. 0-360?, which |
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BRETT: I HAVE AN RV-7A W/ A MATTITUCK, IO 360 (THE 180 H.P. VERSION) & A F/P SENSENICH CRUISE PROP. MY WIFE AND I BUILT IT OURSELVES IN 6.5 YEARS. IT FIRST FLEW ON 8/4/09 AND WE'VE PUT 90 HOURS ON IT SINCE. SO FAR - IT'S BEEN GREAT.
A FEW THINGS TO THINK ABOUT:
1. I HAVE NO EXPERIENCE W/ THE 320 BUT KNOW SEVERAL RV-6 BUILDERS WHO FLY BEHIND A 320, AND THEY'RE FINE W/ IT. THE "7: WILL ALSO FLY OK W/ A 320, AND SOME 7 BUILDERS HAVE USED THEM, BUT I'D GO W/ THE 360. I KNOW THE 320 WILL BURN MOGAS (AUTO FUEL) - BUT ONLY THE NON ETHANOL VARIETY - AND YOU CAN'T HARDLY FIND ANY IN THIS AREA OF NEW ENGLAND. THE HANDWRITING IS ON THE WALL RE NON-ETHANOL MOGAS AND 100LL AVGAS: IN NOT TOO MANY YEARS WE'LL ALL BE BURNING 94 OCTANE UNLEADED AVGAS BECAUSE NON-ETHANOL MOGAS AND 100LL AVGAS WILL BE EXTINCT. (GASOLINE BURNING GA AIRPLANES ARE THE ONLY TRANSPORTATION MACHINES IN THE COUNTRY STILL PUMPING LEAD INTO THE ATMOSPHERE - POLITICALLY (AMONG OTHER REASONS) THIS IS BECOMING INCREASINGLY UNSUSTAINABLE.)
2. ON A RECENT (ADMITTEDLY COLD) MORNING (+10F) I WENT FROM 383' MSL TO 4500' MSL IN TWO MINUTES AND A BIT, AND THAT WAS NOT EVEN CLOSE TO A MAX PERFORMANCE CLIMB. IN CRUISE FLIGHT AT 2300 RPM AND LEANED TO 50 DEGREES L.O.P. I'M SEEING 141 KTS TAS AND BURNING 7.4 GPH. DROP THE RPM TO 2200 AND 50 DEGREES LOP AND YOU'LL STILL BE DOING 130 KTS AND A BIT AND BURNING AROUND 6.5 GPH. THESE SPEEDS ARE WITH ALL GEAR LEG AND INTERSECTION FAIRINGS AND WHEEL PANTS INSTALLED. REMEMBER - YOU ALWAYS HAVE THE OPTION OF THROTTLING BACK A BIT TO SAVE FUEL - THE 180 HORSES ARE THERE IF YOU NEED THEM, VERY USEFUL IN A CLIMB AND IF YOU NEED TO KEEP UP W/ SOMEONE.
3. I'D GO WITH A F/P PROP, UNLESS YOU'RE GONG TO OPERATE ROUTINELY OUT OF HIGH ELEVATION AIRPORTS. THE C/P PROP ADDS WEIGHT, COMPLEXITY AND EXPENSE. SOME FOLKS CLAIM THE F/P SENSENICH CRUISE PROP IS A TAD MORE EFFICIENT IN CRUISE THAN THE C/P PROP. (I WOULDN'T KNOW - HAVING HAD NO EXPERIENCE W/ C/P PROPS IN RVS.) YOU ALSO WANT TO REMEMBER THAT WOODEN PROPS DON'T DO WELL FLYING IN THE RAIN. THEY ERODE.
4. RESALE VALUE OF AN RV-7 IS USUALLY GOING TO BE BETTER W/ A 360 THAN A 320.
5. RE 6 VS 7: THE 6 IS A FINE AIRPLANE, AND I HAVE NOTHING BUT ADMIRATION FOR FOLKS WHO'VE BUILT THEM, BUT THE 7 IS JUST A LOT EASIER TO BUILD - IT'S ALL MATCHED HOLE CONSTRUCTION - YOU DON'T NEED A JIG AND YOU DON'T HAVE TO SPEND HOURS AND HOURS LINING UP AND SPACING RIVET HOLES. BRING THE PIECES TOGETHER, PUT IN SOME CLECOS, AND MOVE ON - NOT ONCE DID WE HAVE HOLES THAT FAILED TO LINE UP. THE 7 IS ALSO A TINY BIT WIDER THAN THE 6, IT HAS A BIGGER RUDDER, IT STANDS TALLER ON THE GEAR, CARRIES MORE, AND OF COURSE IT'LL EASILY TAKE THE BIGGER ENGINE.
6. IT'S ALL UP TO YOU - YOU HAVE TO DECIDE WHAT KIND OF FLYING YOU WANT TO DO, AND OPTIMIZE YOUR AIRPLANE ACCORDINGLY. IN OUR CASE WE TRICKED IT OUT FOR LONG X/C FLIGHTS, VFR OR IFR, DAY OR NIGHT (COM & NAV SYSTEMS, SLAVED TWO-AXIS A/P, FUEL CAPACITY) AND HAVE FOUND IT TO BE A GREAT TRAVELLING MACHINE. IT'S VERSATILE, FAST, HANDLES WELL IN THE PATTERN, IS RESPONSIVE, STABLE, CLIMBS WELL, CLIMBS HIGH, HAS GREAT RANGE CAPABILITY AND TAKES THE BUMPS WELL.
THE ONE THING I'D TELL YOU FOR CERTAIN - IF YOU INTEND TO DO A LOT OF X/C FLYING - PUT IN AN A/P. I'VE FLOWN IT X/C W/ AND W/O THE A/P AND IT'S JUST ORDERS OF MAGNITUDE EASIER, MORE RELAXING, MORE ENJOYABLE, AND SAFER W/ THE A/P.
HOPE THIS HELPS,
DAN BERGERON
RV-7A, N307TB, SPERO II
90 HOURS SINCE FIRST FLIGHT 8/4/09
On Fri, Jan 29, 2010 at 7:29 PM, ray atkinson <raybot(at)comcast.net (raybot(at)comcast.net)> wrote:
[quote] I have some input on this I owned a 6-a with a 320 and a wood prop and it worked great.This was the plane that Van designed.Light and fast.The 7 is van,s response to the overweight too fast for their own good planes that everyone thought they needed.If your friend is pulling away from you because his plane is slightly faster maybe he could throttle back a few revs.These are really fine planes as designed but excess weight and speed put you in the red zone when you blast through some rough air and your heads banging on the canopy. I always took that as a message from the plane to slow down 30 or 40 knots
[quote] ---
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