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11-16-2015, 02:30 PM
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Join Date: Jul 2014
Location: Madison, WI
Posts: 683
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Magnesium or Alum Sump on RV-9a?
Getting ready to order engine and was offered an option of a Magnesium or Aluminum sump. The Magnesium is 7lb lighter and $350 more expensive.
Would this be worth it for an RV-9A with recent glass avionics? Note that I am also going to be running a WW-GA200L prop, which I understand is already rather light.
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RV-9A - started 01/2015, completed 07/19/2018, 500hrs 03/14/2020
RV-10 - started 04/2020
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11-16-2015, 02:44 PM
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Join Date: Oct 2006
Location: Garden City, Tx
Posts: 5,120
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That's a question only you can answer - it comes down to trading dollars for pounds. Each of us will have their own point of happiness on that scale.
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Greg Niehues - SEL, IFR, Repairman Cert.
Garden City, TX VAF 2020 dues paid 
N16GN flying 700 hrs and counting; IO360, SDS, WWRV200, Dynon HDX, 430W
Built an off-plan RV9A with too much fuel and too much HP. Should drop dead any minute now. 
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11-16-2015, 02:47 PM
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Join Date: Jul 2014
Location: Madison, WI
Posts: 683
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I'm more concerned along the lines of CG. Am I getting too light up front? Is there a way to calculate this without knowing all the numbers?
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RV-9A - started 01/2015, completed 07/19/2018, 500hrs 03/14/2020
RV-10 - started 04/2020
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11-16-2015, 02:52 PM
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Join Date: Dec 2009
Location: Boulder, CO
Posts: 4,428
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$50 a pound for weight saved is a bargain. And seven pounds saved is huge.
Sounds like a great deal to me!
Dave
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11-16-2015, 04:38 PM
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Join Date: Jun 2005
Location: Prescott Valley/Chandler AZ
Posts: 351
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What engine?
My 9A with a 320 and WW C/S prop required 2 lbs in the tail until it was painted. I would recommend the lighter option.
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John Morgensen
RV-9A N946PM 600+ hours since 2013
Nevada/Arizona
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11-16-2015, 05:47 PM
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Join Date: Jan 2005
Location: SC
Posts: 12,887
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Quote:
Originally Posted by gfb
I'm more concerned along the lines of CG. Am I getting too light up front? Is there a way to calculate this without knowing all the numbers?
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It is best to build as light as you can. Then you can add weight where you need it, if you need it.
I have thought about buying the sump and installing it on my O-360, just to drop a few pounds, maybe some day. Now if I could get a magnesium belly replacement for me!
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Bill R.
RV-9 (Yes, it's a dragon tail)
O-360 w/ dual P-mags
Build the plane you want, not the plane others want you to build!
SC86 - Easley, SC
www.repucci.com/bill/baf.html
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11-16-2015, 06:09 PM
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Join Date: Aug 2007
Location: Wichita Falls, TX
Posts: 2,182
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If the engine is a 360, then I'd say go for the lighter sump. If a 320 engine, then you might need the extra weight up front.
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Neal Howard
Airplaneless once again...
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11-17-2015, 06:11 AM
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Join Date: Dec 2005
Location: Sydney, Australia
Posts: 427
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Who supplies the Magnesium sump?
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Doug Gray
RV-6 completed, flying since July 2010
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11-18-2015, 01:41 PM
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Join Date: Mar 2014
Location: Laguna Hills, CA
Posts: 1,805
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It seems to me that a lot of 9A's with 320s & FP props (especially composite ones) end up needing more nose weight for optimal cg. Nearing the weighing stage on mine, I'm really curious to see where the cg lands...a little tail-biased for me is not a big issue as I don't anticipate having to carry much baggage. I'd save the $350 and lose bragging rights for having the exotic sump.
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Doug
RV-9A "slider"
Flew to Osh in 2017, 2018 & 2019! 
Tail number N427DK
Donation made for 2020
You haven't seen a tree until you've seen its shadow from the sky -- Amelia Earhart
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11-18-2015, 01:43 PM
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Join Date: Jul 2014
Location: Madison, WI
Posts: 683
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Don't know who the supplier is but Titan is the manufacturer/assembler I am working with that has it.
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RV-9A - started 01/2015, completed 07/19/2018, 500hrs 03/14/2020
RV-10 - started 04/2020
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