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RV-8 cg consideration

D

David-aviator

Well Known Member
Greetings,

I've been thinking about an engine and prop for the 8 and would appreciate some feed back on a basic 180 HP Lycoming with the Catto prop - if there is someone with that set up.

Specifically, where is the cg with 200 pounds in the aft seat?

Thanks.
 
David,

I have a 180 HP engine with a 3 blade Catto. Here are my empty wt numbers:

E.Wt. 1132 lbs
Arm 79.40 in.
Moment 89876.38 in-lbs

E.Wt. includes 8 qts of oil, and 1 gallon of unuseable fuel per tank, mounted fire extinguisher, 2 PC680 batteries, plus a 2nd alternator.

Hope this helps.

Regards,
 
Last edited:
DAGO said:
David,

I have a 180 HP engine with a 3 blade Catto. Here are my empty wt numbers:

E.Wt. 1132 lbs
Arm 79.40 in.
Moment 89876.38 in-lbs

E.Wt. includes 8 qts of oil, and 1 gallon of unuseable fuel per tank.

Hope this helps.

Regards,
Click to expand...

It does. Thanks.

dd
 
Good timing David, as I'm doing quite a bit of fuselage system planning and messing about with w&b numbers (and a shout out to Greg Hale for his great w&b tool).

A question for Tom if I may, since the 180hp + Catto is my planned FWF, and your numbers look to be very close to my targets. Is your battery up front or in back?
 
CG

I have a Superior IO360 and Catto 3 blade prop. Empty weight is 1066. With 30lbs of fuel, 205 in the front, 200 in the back, my CG is at 86.48. Max aft CG is 86.82, so very near aft CG. I used 30 lbs of fuel because the CG moves aft as fuel is used. Odyssey battery on the firewall.
 
brad walton said:
I have a Superior IO360 and Catto 3 blade prop. Empty weight is 1066. With 30lbs of fuel, 205 in the front, 200 in the back, my CG is at 86.48. Max aft CG is 86.82, so very near aft CG. I used 30 lbs of fuel because the CG moves aft as fuel is used. Odyssey battery on the firewall.
Click to expand...

Thanks, Brad.
 
Me too

For Tom and Brad, what is the almost 70 lbs difference? I am still planning but this seems to be what I have been thinking, a 180/200 HP with Catto 3 blade.

My concern has been the aft CG with low fuel and a pax. How do you guys deal with that? My planned mission includes a 150 Lb pax and full use of the tanks to maximize range. I guess you could place battery fwd, but I am thinking of a LiPb battery saving a lot of weight...meaning less weight up front. I guess you could place a smoke oil tank up front and keep it full with a pax.

Anybody have a W&B spreadsheet with the above config so I could play around with the numbers?
 
Nick,

Send me your email address and I'll send you an RV-8 W&B spreadsheet that will allow you to explore various "what if" scenarios.

Mike
 
Luke has a Catto Three blades, O-360-A1A standard, PC680 hang on the firewall. Send me an e-mail info at rv8.it so I'll send you my spread sheet for W&B configurations.
 
Weigh and Balance Sheet

Not sure what the W+B sheet you have looks like but this is what I have built and can send it out as well.

WeightandBalancepic.jpg
 
Cool

Mike, I like it too!

If you're sharing, please send a copy to jesseb at firecontrolinc dot net

Thanks
 
I like the way you have included the graph. Could I possibly have a copy. Thanks . rwtownson at shaw.ca
 
Strike69 said:
Not sure what the W+B sheet you have looks like but this is what I have built and can send it out as well.

WeightandBalancepic.jpg
Click to expand...

Mike,

That is definitely a well designed W&B sheet, if possible, please add me to the email list, [email protected]. One comment, you may have made a data entry error in your example above. For the aft baggage compartment shelf you entered a weight of 75 lbs, the aft shelf is rated for only 5 lbs. The aft baggage compartment floor is rated for 75 lbs.

Regards,
 
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W+B Spreadsheet

Mike,

Would you put me on the list for your W+B Spreadsheet! Very well done!!
When able, send to lonlynn at bellsouth dot net.
Thanks
Lonnie
 
Carl J. Niedermeyer said:
My Preview Plans state (in Section 14) that the RV-8 Rear Baggage Compartment limit is 75 lbs. It then shows some examples with the Rear Floor at 50 lbs and the Rear Shelf at 25 lbs, within the same example.

Here is a shot of my W&B sheet. My RV-8 has the original wing, hence the aerobatic gross is 1550 lbs. RV-8s with the later "dash One" wing have an aerobatic gross weight of 1600 lbs.

RV-8 W&B Plot.jpg
Click to expand...

Carl,

Thanks for the correction. I was speaking from my faulty memory, my aircraft & records are sitting 2500 miles away. I could have sworn that the aft shelf had a weight limit because unlike the aft cargo floor, it is totally non-structural. BTW, nice spreadsheet!

Regards,
 
W+B Sheet limits

Tom -

Excellent point about the load limits for various stations and the potential to think you are good to go. For version two I'll add conditional formating to color a cell red when exceeding the load limit (similar to the overall aerobatic and fuel usage conditions) as well as a warning note.

Thanks
Strike
 
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