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  #1  
Old 06-13-2013, 08:29 PM
sahrens's Avatar
sahrens sahrens is offline
 
Join Date: Jan 2007
Location: Battle Ground
Posts: 487
Default O-360 and Catto FP prop

Hi folks,

I am seeking information from those who have installed an O-360 with a Catto three bladed prop on their RV-7. I am getting ready to order my finishing kit and have one final decision to make before the order. My concern lies in a potential aft CG issue when installing an O-360 and a Catto FP prop. As I understand it my options are one of two installations.

Option 1 is to install a weight of X lbs behind the prop to shift the CG forward. Of course, this reduces useful payload by X lbs may be the least expensive.

Option 2 is to use a engine mount for a O-320 shifting the engine forward with the ensuing CG shift. This option requires an extended cowling (the Vans version might work, I believe I can order an extended Sam James cowl. Not sure about the Sam James cowl working.) This is the more expensive solution.

If you have an RV-7 configured with an O-360 and a FB prop; would you mind sharing your CG issues if any? I appreciate any information you can give.

As a final note, I have considered CS and have read extensively on the performance issues. I have decided on FP.

Thanks for your time.

Scott
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  #2  
Old 06-13-2013, 08:40 PM
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Flyguytki Flyguytki is offline
 
Join Date: Jun 2007
Location: Fairbanks AK
Posts: 758
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I have an IO-360 with the 360 engine mount, I am waiting for a 20lb crush plate to be delivered from saver to correct exactly what you are talking about. Currently with a 3 blade catto my empty cg is at 82 inches, this only allows for 2 people full fuel and 35 lbs of baggage, with the 20lb plate I will be able to get 75 lb of baggage and be at the aft limit before I even reach gross weight.
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  #3  
Old 06-13-2013, 08:41 PM
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Brantel Brantel is offline
 
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Location: Newport, TN
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My RV7 has a FP Sensenich, O-360 and it sits @ 80.77" empty and I have to limit baggage with minimum fuel.

I was going to add weight to the nose with a weight ring but I decided to go with a Hartzell CS instead.

I imagine the Catto will be much lighter than the Sensenich so I would take action now.

I like the 320 mount idea. I had to cut off a good bit on the aft side of my cowl when fitting. That may be enough meat to allow for the longer mount and even if not, it would not be too difficult to extend it.

Keep in mind that more fuel moves the CG fwd and less fuel moves it aft. Always also check your CG based on what your minimum fuel will be....
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Last edited by Brantel : 06-13-2013 at 08:47 PM.
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  #4  
Old 06-13-2013, 09:04 PM
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roadrunner20 roadrunner20 is offline
 
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My empty CG RV7 with 3-blade catto prop is 81.11"
I do limit baggage to 75lbs and attempt to move some forward for landing. My wife always has a backpack she moves forward for landing.
On XC trips with baggage, I toss a couple scuba bean bag weights to my forward cabin. Every little bit helps.
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  #5  
Old 06-13-2013, 09:27 PM
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rv7boy rv7boy is offline
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Default C.G. Aft limit of RV-7?

For those of us who are still building and are interested in this thread, what is the RV-7 aft c.g. limit per Van's design?
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Last edited by rv7boy : 06-13-2013 at 09:39 PM.
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  #6  
Old 06-13-2013, 10:20 PM
crabandy crabandy is offline
 
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Location: Ottawa, Ks
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I'm just mounting my catto 3 blade on my O-360 RV7 and was thinking the same thing. I probably won't safety the prop bolts on till I get the rest of it together and weigh it.
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  #7  
Old 06-13-2013, 10:34 PM
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newtech newtech is offline
 
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I put 5/8" spacers between my engine mount and firewall, added a 20 lb. Saber crush plate and a 12 pound harmonic damper and finally have my RV-7A CG in the "sweet spot." If you have a solid crank I would go with the O-320 engine mount; but, if you have a hollow crank the longer engine mount would mean you couldn't switch to a constant speed prop in the future.
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  #8  
Old 06-13-2013, 10:47 PM
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sahrens sahrens is offline
 
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Default CS conversion

That is an interesting point. I had not considered the conversion to CS at a later date and the impact of the longer engine mount. Adding a spacer is something to seriously consider.
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  #9  
Old 06-13-2013, 11:57 PM
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Flyguytki Flyguytki is offline
 
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Location: Fairbanks AK
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regarding the spacer, I ordered mine about a week ago, the Cost is $299 for the spacer as well as the extra long bolts. What people fail to realize is just how LIGHT weight the catto propellers really are. Mine is a bit larger than most at 70X72 and it only weights 14 pounds, compare it to the standard Hartzell CS which weighs in at 60 and you have a HUGE difference.
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  #10  
Old 06-14-2013, 12:22 AM
rockwoodrv9 rockwoodrv9 is offline
 
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I haven't done all the weight and balance, but can you be too light in front? I want a Catto FP prop and I have the small battery. Will I be able to carry any baggage at all? The W&B I have done with sample data, I will be pretty limited unless I add a weight plate to the front. Maybe that is just for the 9, but still something to think about. Spending so much effort to keep the weight down, then adding a plate doesn't sit right! I am sure once I can get the plane on the scales, I will be able to figure things out, but what have others experienced?
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