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O-360 and Catto FP prop

sahrens

Well Known Member
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
 
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.
 
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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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.
 
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? :confused:
 
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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.
 
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.
 
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.
 
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.
 
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?
 
Batteries

For you guys flying with FP (lightweight) props and seeing W&B limits, what do you have for batteries? I'm going with a PC680 and a UPG backup battery, both on the firewall, is this similar to what you have? If so, I'm guessing I'll need the crush plate or engine mount spacers? Does vans have any problems with the spacers?

Good thread!

David
 
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.


That is a good idea to move the mount, do you have pics of how you did that?
 
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?
I do not have a 7. I do have a 9A however that I built with the ECi IO340, 3-blade Catto and Saber extension. I made reference to this information in this thread concerning the Anti-Splat brace here:
http://www.vansairforce.com/community/showthread.php?t=100738

I made this comment in that post:
One other point concerning building. I new I would be flying off of grass when I started building. A prime goal of my build was to keep the weight as light as possible on the nose gear. This was the motivation for many decisions I made concerning the firewall forward components. I have a Catto Prop (12 lbs total weight), ECi IO-340 that gave me 360 engine like HP at 320 engine like weights, light weight SkyTech starter, Plane Power alternator, etc. Basically every decision on what to put on the nose of the airplane had a high priority of keeping weight to a minimum. Here are my weights calculated for my Weight & Balance (fully painted, empty fuel, 6 quarts of oil):
Right Wheel 425
Left Wheel 430
Nose Wheel 252
Total 1107
C.G. 78.82
The forward CG limit is 77.95 and the aft CG limit is 84.84 for the 9A.

As you can see with my post, my empty C.G. = 78.82. I have a lot of room to spare before reaching either fore or aft limits. I have multiple CG scenarios in my POH that show where the CG moves at different aircraft loadings. Basically I looked at Empty Weight CG, Most Forward CG and Most Aft CG. In my analysis what I found was there was no real world situation that would bust the forward CG. I didn't even come close with full fuel, zero weight in pilot, passenger and baggage area. Even that criteria had the CG @ 78.48.

I was able to bust the Aft CG with 4 gallons fuel, 255 lb pilot, 240 lb passenger, 80 lbs baggage. There were a lot of other weight scenarios that allowed for busting the aft CG but they were mostly seeing absurd weights for baggage, pilot or passenger that did not represent reality. This one was a realistic real world loading that did not bust the gross weight of the airplane and that I could actually foresee happening. That is, a long cross country with a buddy and our baggage, say on a flight to Oshkosh, and at the end of a leg where we are running low on fuel.

There are some differences with CG between the 'A' models and the tail wheel models that need to be considered. I am sure a tail wheel model builder can chime in with their info. This is a data point that I hope will be useful to you and others though. Hope it helps.

P.S. David, saw your query about what battery is being used after I posted. I am using the Odyssey PC680 mounted on the firewall.
 
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I have been mulling over the FP vs. CS issue for a while -- sadly, I won't have to make that choice for a couple of years. However, the idea of a heavy crush plate or harmonic balancer with something like a Catto prop seems reasonable. I mean, the CS prop would add even more weight to the nose, so it isn't like you're adding weight that a lot of planes don't already carry. Then you can keep the normal mount and cowl and have the option (for yourself or a subsequent owner) of going to a CS prop later on.
 
Aft CG limit for RV-7

Second time...(see post #5) ...what is the aft C.G. Limit for the RV-7 per Van's design?
 
Catto 3B/0-360 on a 7a

The 0-320 engine mount gives you an extra 2" forward. When ordering my finish kit Vans talked me out of the 0-320 mount so I ordered the 0-360 mount for the 0-360 core I'm building.Bob at Aircraft specialties talked me out of removing the inside plug when they yellow tagged the Crankshaft as it would hinder a CS conversion latter, I had the urethane coating applied and the outer plug installed,looks like they used a bead of clear silicone around the bore before installing the outer plug. I'm not there yet but want to acquire a 0-320 mount and will trade new for new or buy outright( whats another G at this point?). Point is 2" won't solve all the problem but is a far better alternative to adding weight. It's tough to argue with Vans or ACS and yes I need to consider any future owner as this project is an asset/liability and may need to go to a new home some day :( . Has anybody done a 0-360 on a 7a with a 0-320 mount? If so I would like to talk about the numbers,what did it buy you in real world terms.
Bob
 
More information

In my -7 I started with the 0-360 and the Sensenich metal prop which with the hub weighed approx 42 Lbs. I was not particularly happy with the take off performance as at the time I was at a high altitude airport (Salt Lake #2). I also could not use the full 100 Lbs of baggage on a long cross country due to the CG moving aft of the aft CG point with minimum fuel. To solve the problem I added the landoll ring to the flywheel which put approx 12 Lbs right up front and problem was solved.
I then saw Mel's -6 with the Catto 3 blade and thought it looked very cool plus he told me how it performed so I switched to the Catto which weighs about 18 Lbs and added a sabre 14Lb spacer to compensate for the weight difference with the sensenich. With this setup I can carry 75Lbs of baggage in the baggage compartment and stay in CG until I get down to 10 gals of fuel remaining. Sabre has a heavier spacer that is around 20 Lbs and this would allow me to carry the same 75Lbs until I get down to 5 gals remaining.
I should also note that I carry tools and tiedowns etc in two bags that fit between the seatback and the flap tube which weigh 32.4 Lbs in addition to the baggage 75 Lb limit (114.78 Arm).
The Catto outperforms the Sensenich by quite a bit, has a narrower hub which helps CHT's on climbout, winds down quicker which helps slow down and is very smooth so you will not be disappointed with the choice.
I have a W&B excel spreadsheet with both Solo and Full up configurations which I would be happy to send to you if you want to play with the numbers.

P.S Odessy PC680 battery on the firewall
 
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7a data

The 0-320 engine mount gives you an extra 2" forward. When ordering my finish kit Vans talked me out of the 0-320 mount so I ordered the 0-360 mount for the 0-360 core I'm building.Bob at Aircraft specialties talked me out of removing the inside plug when they yellow tagged the Crankshaft as it would hinder a CS conversion latter, I had the urethane coating applied and the outer plug installed,looks like they used a bead of clear silicone around the bore before installing the outer plug. I'm not there yet but want to acquire a 0-320 mount and will trade new for new or buy outright( whats another G at this point?). Point is 2" won't solve all the problem but is a far better alternative to adding weight. It's tough to argue with Vans or ACS and yes I need to consider any future owner as this project is an asset/liability and may need to go to a new home some day :( . Has anybody done a 0-360 on a 7a with a 0-320 mount? If so I would like to talk about the numbers,what did it buy you in real world terms.
Bob

+1
I would also like to see data on the 7a with io360 and FP and CS prop.
So far I plan CS because she will live at 5+K feet.
 
Thanks

Thank you to everyone who has responded to my questions. Several ideas were shared here, on other forums and through email. For those reading with the same questions I thought I would summarize some of the ideas and thoughts sent to me. In no particular order:

1. Using a Cato prop is lighter, but to avoid an aft CG in some configurations I will need a counter weight at the spinner. This does negate some of the weight savings of the lighter prop. Some have suggested moving baggage during low fuel conditions.

2. Using a 320 mount with a 360. Well the 320 cowling would probably work, but the scoop won't fit the 360 requiring removal and replacement of the scoop. I have not heard from anyone that has the 320 mount installed with a 360.

3. There is an option of extending the mount with spacers. This does move the landing gear forward slightly (RV-7.) I am not sure if that is an issue.

4. Of course there is always the CS option.

Thanks for you input.

Scott
 
The 0-320 engine mount gives you an extra 2" forward. When ordering my finish kit Vans talked me out of the 0-320 mount so I ordered the 0-360 mount for the 0-360 core I'm building.Bob at Aircraft specialties talked me out of removing the inside plug when they yellow tagged the Crankshaft as it would hinder a CS conversion latter, I had the urethane coating applied and the outer plug installed,looks like they used a bead of clear silicone around the bore before installing the outer plug. I'm not there yet but want to acquire a 0-320 mount and will trade new for new or buy outright( whats another G at this point?). Point is 2" won't solve all the problem but is a far better alternative to adding weight. It's tough to argue with Vans or ACS and yes I need to consider any future owner as this project is an asset/liability and may need to go to a new home some day :( . Has anybody done a 0-360 on a 7a with a 0-320 mount? If so I would like to talk about the numbers,what did it buy you in real world terms.
Bob

The plan for my -7 is o-360 (solid crank with original heavy accessories) Sensenich Alu FP. I want to be able to use all my baggage so was planning on using the 0320 mount even with the heavier Sensenich.

Not interested in CS, if future owner wants CS he's gonna have to do a engine transplant, while the engine is off not really a big deal to also change the mount.

That type of guy is also going to want injected so will be needing to do cowl mods as well.

I'm more likely to change from Sensenich to Cato etc rather than to CS.

My understanding is that you need to also get 0320 FF because you need the longer hoses with the longer 320 mount not the shorter o360ff.

I would be very interested in anyone's experiences with 320 mount 360 engine regardless model. How much longer is the 320 mount?
 
The plan for my -7 is o-360 (solid crank with original heavy accessories) Sensenich Alu FP. I want to be able to use all my baggage so was planning on using the 0320 mount even with the heavier Sensenich.

Not interested in CS, if future owner wants CS he's gonna have to do a engine transplant, while the engine is off not really a big deal to also change the mount.

That type of guy is also going to want injected so will be needing to do cowl mods as well.

I'm more likely to change from Sensenich to Cato etc rather than to CS.

My understanding is that you need to also get 0320 FF because you need the longer hoses with the longer 320 mount not the shorter o360ff.

I would be very interested in anyone's experiences with 320 mount 360 engine regardless model. How much longer is the 320 mount?

Once you step off the Plans,your in custom turf. Chad Jensen Rv-7 did a 0-360 on a 0-320 mount with a Sam James cowl,Catto 3B and yes you will need custom(longer) hoses/cables,however everything else would be 0-360 like the baffle kit,if you use the 0-320 cowl you would need to move the scoop and I'm told this cowl is very tight on a 0-360 also there is a difference between upper & lower cowl's respectively.My understanding the 0-320 mount is 2" longer than the 0-360 mount.
My other point is Vans doesn't support what they call untested configurations so a call to Vans about this will frustrate you no end.Same with the fixed/CS argument CS is "more better" so everyone will push you in that direction.I'm set Catto 3B,0-360 carb,EI both,Tip up,7a & full anti-splat.I'm not going to argue with Vans or the guy who decides my Yellow tag issues but in the end I'll build what I want and can afford.
Bob
 
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That is a good idea to move the mount, do you have pics of how you did that?
Aluminum spacers that Mike Zeller, of RV-8 Canopy Latch fame and local EAA Chapter 21 member, made for me.
EngineMountSpacer.jpg


And this is a picture of the Sabre 20 lb. crush plate and Landoll harmonic damper

CrushPlate.jpg


The combination of the two has really tamed my RV-7A. She no longer wants to go down on her tail with full baggage, low fuel and two people on-board.
 
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Aluminum spacers that Mike Zeller, of RV-8 Canopy Latch fame and local EAA Chapter 21 member, made for me.
EngineMountSpacer.jpg


And this is a picture of the Sabre 20 lb. crush plate and Landoll harmonic damper

CrushPlate.jpg


The combination of the two has really tamed my RV-7A. She no longer wants to go down on her tail with full baggage, low fuel and two people on-board.

Thanks for the pics, that looks like a simple fix.
 
The forward CG limit is 77.95 and the aft CG limit is 84.84 for the 9A.

There are some differences with CG between the 'A' models and the tail wheel models that need to be considered. I am sure a tail wheel model builder can chime in with their info. This is a data point that I hope will be useful to you and others though. Hope it helps.

P.S. David, saw your query about what battery is being used after I posted. I am using the Odyssey PC680 mounted on the firewall.

Here's my numbers as I've converted from an A to TW.
I also have the PC680 FW mounted battery.

Empty weight/CG Limit

A model
1096/80.71

TW model
1065/81.11

Please note that I did remove the cabin gear weldments. Some have opted to not do so.
 
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The first question to ask is, are you building a -7 or a -7A?

I ask because the A's tend to be tail heavy due to the location of the mains.

Granted I have a -9, not a -9A, and the CG is slightly different but I do have an O-360 and a two bladed Catto prop. My engine has the hollow crank (Who knows, I might want to add a CS prop someday.), dual P-mags (each is 1.5 lighter than a mag), a lightweight SkyTec Starter, PC680 mounted in the standard location, Sam James Cowl, Saber prop extension, etc.

The engine mount is 10? from the firewall to the dynafocal ring. (The mount for the old, small engine, was 12?)

This combination worked out great but the moral is to build the plane as light as you can and then add weight as you need it, if you need it.
 
. . .the A's tend to be tail heavy due to the location of the mains.
Actually I think that might be the other way around. The tail wheel airplanes tend to be more tail heavy. Dan's info seems to support this with his C.G. shifting further back slightly after conversion.
Here's my numbers as I've converted from an A to TW.
I also have the PC680 FW mounted battery.

Empty weight/CG Limit

A model
1096/80.71

TW model
1065/81.11
 
W&B link

86.82" normal

84.5" aerobatic

Recommended W&B numbers for all models available here:

http://www.vansaircraft.com/public/downloads.htm

Thanks for the reply, Brian. I'm not far enough along to be too concerned yet about the W&B decisions for my build, but it is nice to know what the CG limits are. Plus, I was not aware of the very useful link on Van's site that you provided. Looks like I need to spend more time cruising the factory web site. :eek:
 
Actually I think that might be the other way around. The tail wheel airplanes tend to be more tail heavy. Dan's info seems to support this with his C.G. shifting further back slightly after conversion.

Nope, one data point doesn't make it so.

I checked the numbers from Dan C's old list of RV W&B's (I sure wish he had kept that one part of his site up.) and the average of the 36 -7's listed (w/o Egg engines) is 79.59" and the average of the 50 (again, w/o Egg engines) -7A's is 79.95", close to a 1/2" further aft.

Remember, with the A's, you have those heavy mains, brakes, wheels and tires behind the CG. With the tail draggers, you only have that little TW back there and it is not enough to offset the balance.
 
Nope, one data point doesn't make it so.

I checked the numbers from Dan C's old list of RV W&B's (I sure wish he had kept that one part of his site mye up.) and the average of the 36 -7's listed (w/o Egg engines) is 79.59" and the average of the 50 (again, w/o Egg engines) -7A's is 79.95", close to a 1/2" further aft.

Remember, with the A's, you have those heavy mains, brakes, wheels and tires behind the CG. With the tail draggers, you only have that little TW back there and it is not enough to offset the balance.

All of the data was provided by builders. Sounds like this would be a great addition here on VAF. I will be calculating a new CG as a part of my Conditional, that is under way right now, and will post the info soon. DR, do you think your new graduate would keep a w&b spread sheet updated? Since my -7A has an extra 38 lbs. on the nose and 5/8" spacers between the firewall and engine mount I am very interrested in seeing where my plane fits into the fleet.
 
You guys are worrying me now, me and a buddy(mostly him) is building a 7A and we have a 0-320 and a catto 2 blade,,, are we gonna have bigtime problems with cg with baggage on board, the whole reason we went iwth the 0-320 and fp is to save weight making a light aiframe, he built a 7 several years ago with same setup and didn't have any cg issues, and adding a crush plate just defeats the purpose in my opinion, its sorta deadweight, but I also see why people do, not judging just thinking outloud.
 
And this is a picture of the Sabre 20 lb. crush plate and Landoll harmonic damper
CrushPlate.jpg

Any idea how much Van's standard crush plate weighs?
Anybody have one on the shelf that can weigh it & report back.

Steve, yours appears to about an inch thick. Is that correct?
I believe Vans is 1/2".
 
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0-360 Catto 3B on a 0-320 mount SJ cowl photo

There is a photo of the Chad Jensen's Ex(RV-7 Long Nose) on the front page VAF today sporting a new paint job. I like the look of the 2" extension. I have no illusions that this will cure any aft CG problem but it helps and looks way cool to boot.My build is a 7a,0-360,Catto 3B,full anti-splat mods. Has anybody completed a "long nose 0-360 and willing to share the numbers?
 
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