Craig Catto Props - Page 2

LifeofReiley · #11 03-22-2007, 10:44 AM

Hi David,

Your question can be answers with a few variables cleared. My engine will sit
2 1/2"'s further forward than most RV7 / RV7A's built. This also means the cowling, prop, spinner, 12 holer etc... will also be forward. The weight difference in the props (Sensenich vs Catto 3 blade) is around 19 lbs. Depending on the type/brand starter & alternator you install you can actually be heavier on the nose with the Catto if you wish. The 12 holer will also add 5 oz's over the standard spacer. Hope this helps...

McFly · #12 03-22-2007, 12:02 PM

Quote:

I would really like to go the way of Catto. But in talking/listening with/around other builders, there were discussion(s) that a metal prop was favored up front on -7's for better W&B.

I am using a three blade catto on a RV-7 with the small rudder. I did use a 10lb crush plate from Sabre to help bring the weight forward, which one could argue negates the weight advantage. Anyway, you still have the option of swinging a CS prop down the road if you go this route. I am really happy how my W&B turned out (My info is on Dan?s web site if you are interested) but it did take some planning.

This is a little off topic but you may find it interesting. I did my spin testing with an acro instructor. My instructor said ?This recovers almost as fast as my Pitts? (S2-B I believe) after 2 turn spins

This was a very nice surprise since I have the small rudder and a fairly average CG.

Good luck with your descision.

Scott Will · #13 03-22-2007, 12:11 PM

Quick note on the CG issue. I purchased a 22 lb prop spacer from Sabre Mfg and that helped a lot. They also have a heavier crush plate if you're interested.

java · #14 03-22-2007, 12:19 PM

I am a long way from FWF, but am wondering if the rearward CG tendencies of the 7 with a lighter engine / Catto combo up front could be countered, at least somewhat, by more "value added" weight instead of a steel crush plate or other ballast. For example, could you go with a dual alternator setup, which not only adds forward weight, but also can be important redundency if you have an all electric panel? What other options (other than engine/prop) could be worked in forward of the firewall to add useable weight? Room for a second battery?

Of course, the $'s associated with "useable" weight may be much more significant than ballast weight.

LifeofReiley · #15 03-22-2007, 12:39 PM

Quote:

Originally Posted by java

I am a long way from FWF, but am wondering if the rearward CG tendencies of the 7 with a lighter engine / Catto combo up front could be countered, at least somewhat, by more "value added" weight instead of a steel crush plate or other ballast. For example, could you go with a dual alternator setup, which not only adds forward weight, but also can be important redundency if you have an all electric panel? What other options (other than engine/prop) could be worked in forward of the firewall to add useable weight? Room for a second battery?

Of course, the $'s associated with "useable" weight may be much more significant than ballast weight.

Now you're thinking! I'm sure a backup alternator. battery, balancer, cold air induction, plenums etc... could be classified as valued added weight. The list could go on for sure.

Scott Will · #16 03-22-2007, 02:31 PM

Believe me guys... I did the math on extra battery, alternator, etc. The prop spacer or crush plate gives you the most bang for the buck in terms of W&B because it's basically as forward as you could put the weight. If I recall, adding a 2nd battery only moved my CG forward about 0.5" (something in that range). From that day on I physically marked on the plane the CG range so when I was building I could see what I was working with.

David Johnson · #17 03-26-2007, 02:32 AM

Or air conditioning! ;-)

Summer's a-comin'

Dave

David_Nelson · #18 03-26-2007, 12:58 PM

This is all great info guys! Thanks!

Darrell - Is this a custom mount? Sounds like you're having some fun....

Dave B. - Ahh..that makes sense given that the -7's were also designed for the heavier 360's w/ CS. I'm planning on an IO-360-M1B w/ a FP so I know I'm gonna need some extra weight up front.

Hugh - It took me a little while to figure out what a crush plate was - I take it it's the metal plate on the front of the prop. Does the Catto require periodical re-torqueing since its core is still maple? Or does all the glass keep moisture out of the core? One thing I have not been able to figure out is why would having a crush plate give me the option of turning a CS prop down the road should I decide to?

Scott - Your reference to a 22 lb prob spacer - is this still 2-1/4" or different?

Thanks Guys!
/\/elson
RV-7A - Fuselage
Austin, TX

McFly · #19 03-26-2007, 02:23 PM

Quote:

Hugh - It took me a little while to figure out what a crush plate was - I take it it's the metal plate on the front of the prop.

You got it.

Quote:

Does the Catto require periodical re-torqueing since its core is still maple?

Yes it does. I am told that is less susceptible to the torque going out of spec. This is my first non metal prop so I am just repeating what I have heard.

Quote:

One thing I have not been able to figure out is why would having a crush plate give me the option of turning a CS prop down the road should I decide to?

One poster suggested a longer engine mount to offset the reduced prop weight, which is actually a very cool idea. The downside is that it makes your FP choice more permanent in that the added weight of a CS prop, should you ever decide to change, may make your ship too nose heavy.

The heavy crush plate brings the CG forward without any airframe modification, like you said it just bolts on to the front of the prop. The downside of this method (as others have pointed out) is that it is just dead weight. Good luck.

LifeofReiley · #20 03-26-2007, 02:54 PM

Quote:

Originally Posted by David_Nelson

This is all great info guys! Thanks!

Darrell - Is this a custom mount? Sounds like you're having some fun....

Dave B. - Ahh..that makes sense given that the -7's were also designed for the heavier 360's w/ CS. I'm planning on an IO-360-M1B w/ a FP so I know I'm gonna need some extra weight up front.

Hugh - It took me a little while to figure out what a crush plate was - I take it it's the metal plate on the front of the prop. Does the Catto require periodical re-torqueing since its core is still maple? Or does all the glass keep moisture out of the core? One thing I have not been able to figure out is why would having a crush plate give me the option of turning a CS prop down the road should I decide to?

Scott - Your reference to a 22 lb prob spacer - is this still 2-1/4" or different?

Thanks Guys!
/\/elson
RV-7A - Fuselage
Austin, TX

Hi Dave,

Long time no see!

This is not a custom mount, it's Van's design for my configuration. Way cool! The engine sitting out a little more forward is exactly what I want. I just ordered my 12 holer from Sabre along with an 1 3/8" crush plate. CG issues are resolved. With the extra 2 1/2" forward and the crush plate I'll even be better off than bolting one of those Sensenich props up front.