Van's Air Force
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CG Weight Prop Selection
- Thread starter sglynn
- Start date
robertahegy
Moderator/Tech Counselor
I used a Hartzell BA C/S prop on my 7A and found that the plane balanced very well under all loading conditions.
Roberta
Roberta
Walt
Well Known Member
Yep.. the weight of a constant speed prop is needed to get best CG location.
Without it you will definately limit your baggage, especially with low fuel.
I'm not so convinced! Sure a c/s prop is desirable, but is significantly more expensive. If you can afford it, no question go for c/s, but if your budget is limited I don't think you will find a significant loading limitation. Care will be required to keep the tail light, and you may have to think about what is in the baggage bay (a little). But I don't think it will be an issue most of the time.
Pete
Pete
Bud K
Well Known Member
Go with a C/S prop
I wish my -7 had a C/S prop. I bought my with a fixed pitch prop and I am tail heavy with two people, luggage, and low fuel. A fixed pitch prop worked fine when I was flying off of paved runways all the time. Now that I am flying off a 2,200' grass runway with trees on both ends, a C/S prop would add performance margin.
I wish my -7 had a C/S prop. I bought my with a fixed pitch prop and I am tail heavy with two people, luggage, and low fuel. A fixed pitch prop worked fine when I was flying off of paved runways all the time. Now that I am flying off a 2,200' grass runway with trees on both ends, a C/S prop would add performance margin.
sglynn
Well Known Member
Fixed or constant speed on a 7A
Interesting diverse messages.
I am within 6 months of buying engine and until now have been planning fixed pitch on a IO360, w/ nose gear. Because my Cherokee has a constant speed on an O540 and I find it expenses every year to annual, real expensive to overhaul when needed and I don't really see the performance benefits. I would think a cruise fixed pitch on a 2 seater 1000 pound airplane with 180 horsepower would climb great with any pitch prop so why bother with the much higher price tag and maintenance.
Best reason for why is this CG issue. If I wont be able to carry full load of camping stuff, golf clubs and woman, then I'd better spend the dough on CS, even though I'd rather not.
So, any more experience out there specifically for a 7A?
Interesting diverse messages.
I am within 6 months of buying engine and until now have been planning fixed pitch on a IO360, w/ nose gear. Because my Cherokee has a constant speed on an O540 and I find it expenses every year to annual, real expensive to overhaul when needed and I don't really see the performance benefits. I would think a cruise fixed pitch on a 2 seater 1000 pound airplane with 180 horsepower would climb great with any pitch prop so why bother with the much higher price tag and maintenance.
Best reason for why is this CG issue. If I wont be able to carry full load of camping stuff, golf clubs and woman, then I'd better spend the dough on CS, even though I'd rather not.
So, any more experience out there specifically for a 7A?
swisseagle
Well Known Member
Changed prop and getting tail heavy
Hello
My buddy will change from a Sensenich metal FP to a Catto propeller. This brings him on a standard RV-7A/IO-360 to a tail heavy plane!
The limitation is if you fly off al the fuel and have full baggage.
We now ordered the prop with a 15 lbs heavy crush plate to correct this to acceptable values.
I do not understand this, Vans normally go light, less instruments, less equipment, wood prop and you will get an tail heavy airplane! Why not make the engine mount by 2" longer (as it is if you have a O-320 engine mount).
Not everybody can afford a C/S propeller.
Hello
My buddy will change from a Sensenich metal FP to a Catto propeller. This brings him on a standard RV-7A/IO-360 to a tail heavy plane!
The limitation is if you fly off al the fuel and have full baggage.
We now ordered the prop with a 15 lbs heavy crush plate to correct this to acceptable values.
I do not understand this, Vans normally go light, less instruments, less equipment, wood prop and you will get an tail heavy airplane! Why not make the engine mount by 2" longer (as it is if you have a O-320 engine mount).
Not everybody can afford a C/S propeller.
2" longer mount
I fought with Vans over this issue. I have a beautiful Catto 3blade ready to go on my 0-360 parallel with a stock Vans 0-360 cowl and wanted to order the 0-320 mount.The argument is this modification is not supported by them and I should just go with the program.I like the idea of the nose gear mounting points as close to the firewall as possible.The limitation is the length of the cowl at the firewall end,you may need to add fiberglass to fill the gap.Another option is to machine shims(aluminum or Brass) to extend the mount to the edge of your cowl as it comes from Vans,the down side of this is the gear mount extends away from the wall,or call Sam James and tell them what you want to do.I'm still in the market for a 0-320 "A" engine mount if anyone has one to sell.My understanding is this is not a cure but every little bit helps.
RHill
I fought with Vans over this issue. I have a beautiful Catto 3blade ready to go on my 0-360 parallel with a stock Vans 0-360 cowl and wanted to order the 0-320 mount.The argument is this modification is not supported by them and I should just go with the program.I like the idea of the nose gear mounting points as close to the firewall as possible.The limitation is the length of the cowl at the firewall end,you may need to add fiberglass to fill the gap.Another option is to machine shims(aluminum or Brass) to extend the mount to the edge of your cowl as it comes from Vans,the down side of this is the gear mount extends away from the wall,or call Sam James and tell them what you want to do.I'm still in the market for a 0-320 "A" engine mount if anyone has one to sell.My understanding is this is not a cure but every little bit helps.
RHill
Joness0154
Well Known Member
I wonder if this CG issue rules out running the ULPower engines in the aircraft with the fixed pitch propeller? From what they're advertising, the ULPower 200hp motor is 40lbs lighter than a traditional IO-360.
CG
There are lots of ways to attack this. I have an O-320 with a Catto 3-blade. I put a 3/8" shim between the firewall and the O-320 engine mount and have a Sabre 4" extension on the engine so weight of the prop is a couple inches further forward. Nice long cowl actually makes the plane look cool. CG is perfect. Didn't really plan it that way from the start as I converted from an O-235 to an O-320 and didn't want to modify the Cowl. Turns out it worked perfectly.
There are lots of ways to attack this. I have an O-320 with a Catto 3-blade. I put a 3/8" shim between the firewall and the O-320 engine mount and have a Sabre 4" extension on the engine so weight of the prop is a couple inches further forward. Nice long cowl actually makes the plane look cool. CG is perfect. Didn't really plan it that way from the start as I converted from an O-235 to an O-320 and didn't want to modify the Cowl. Turns out it worked perfectly.
