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  #1  
Old 12-03-2017, 05:09 AM
Future RV 9 Flyer Future RV 9 Flyer is offline
 
Join Date: Sep 2011
Location: Marathon,WI
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Default W&b with earthx battery and 3 blade catto prop

Hi all,just ordered my finish kit and to save shipping ordering the fwf parts also.i am going to go with the earthx battery and catto 3 blade prop,do I need to be concerned about w&b problems?Also any other things to delete or substitute in the fwf Kit? Engine will be a yio-320 thunderbolt lycoming.Thanks for the help
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  #2  
Old 12-03-2017, 11:13 AM
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RVbySDI RVbySDI is offline
 
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Location: Tuttle, Oklahoma
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Quote:
Originally Posted by Future RV 9 Flyer View Post
Hi all,just ordered my finish kit and to save shipping ordering the fwf parts also.i am going to go with the earthx battery and catto 3 blade prop,do I need to be concerned about w&b problems?Also any other things to delete or substitute in the fwf Kit? Engine will be a yio-320 thunderbolt lycoming.Thanks for the help
No. CG with the Catto prop and EarthX battery has my CG right in the center of the CG window for my 9A.
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  #3  
Old 12-03-2017, 02:13 PM
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N941WR N941WR is offline
 
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If you are talking about an RV-9 and not a -9A, then you probably won't have a CG issue. (The -9A sliders tend to be bit tail heavy compared to a comparably equipped 9 tip-up.)

However...

A lot depends on the engine, engine mount, starter, mags vs. EI, instruments installed and their locations, etc.


I suspect your engine is a wide deck, so it will weigh more than a narrow deck 320.

All those things add up and you won't really know until it is all together.

The good news is, if you are a little tail heavy, you can add a heavy crush plate in front of your Catto and bring it in line fairly easily.
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Old 12-03-2017, 03:42 PM
Future RV 9 Flyer Future RV 9 Flyer is offline
 
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Location: Marathon,WI
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Default W&b

Thanks Steve and Bill,I am building an A model and plan on E Mags so it sounds like it’s doable.
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  #5  
Old 12-03-2017, 10:40 PM
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bruceh bruceh is offline
 
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Location: Ramona, CA
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The CG window for the -9 is big and easy to hit. I have the Carbon Fiber Sensenich ground adjustable prop up on the nose and it is pretty lightweight. You want to have a lighter nosewheel. I think Van's wants to see less than 325 pounds on the nose gear. Unpainted, mine was 247 pounds on the nosewheel, and after paint (which moved the CG aft a little bit) it was 243 pounds. Paint added around 35 pounds, but there is a lot of surface area on the aft fuselage and empennage.
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  #6  
Old 12-04-2017, 08:04 PM
whd721 whd721 is offline
 
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Location: Beaverton, OR
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You do have to be concerned about the CG, a lot, if you try to lower the weight a significant amount.

Most weight savings available are forward of the CG. Removing weight aft of the CG is almost impossible unless you change Van's kit.

I wanted to build a very light RV9A tip-up with a 233 engine. I made every effort to calculate the finished CG, but it is nearly impossible. I weighed every piece of a RV9A and put it into a spreadsheet. But the moment arms need to use that data were impossible to come up with. ie what is the moment arm of an e-mag?
Or the exhaust system or the engine baffles?

I finally decided to move my engine ~1.75 inch forward. (New engine mount) because that was all I could and still use the Van's engine cowl.
it wasn't enough. I wound up with a very aft CG, I had to replace light stuff with heavy stuff, to move the CG forward. My final empty weight is 1005 lbs with seats, all fairings ready to fly.

If you stray from Van's stock kit and recommended engines you will add $$ and time to the construction time.

Procede with caution and with your eyes open making changes. The RV9 and RV9A are fairly tolerant with the CG envelope, but only with a few small changes.

Good Luck!!
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Old 12-05-2017, 10:05 AM
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9GT 9GT is offline
 
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I am installing a dual Shorai batteries on my -9A slider with two master switches. Both mounted on the firewall, one left side and the other on the right side. I fabricated my own battery trays and supports. Use the right, use both for starting, or use the left battery. I will always have a fully charged battery for back-up power should I have an alternator issue. I figure that the additional weight of the second battery tray, battery, wire and the additional solenoid will help gobble up the weight savings from the PC680 yet still saving a couple pounds. I have the Anti-Splat Nose-Job 2 installed so that adds some forward CG weight also.
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