Champ 7gc
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Bob Turner
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Share some photos?
flightfarm
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I have a 7GC converted to 7GCA. It has an O-320 in it. Very fun plane. I love mine. Not many were built. Only 171 were built according to Wikipedia. The W/B kinda sucks in mine. It's very nose heavy. With it's current W/B, I have to keep about 50lbs of ballast in the cargo area to stay inside the envelope. I may have it reweighed when it warms up here. Compared to other champs and citabrias, my W/B seems off.
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Is your battery in the back or still on the firewall?
I just pulled the heavy Concorde battery out of my 8KCAB and replaced it with a lithium to the tune of -20 pounds which actually moved the empty CG forward an inch!
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The early Citabria ECA's are usually a good deal when they come up. 115 hp with the higher gross weight of 1650 (check me on that but I'm pretty sure) and they don't get the premium prices that go with the later spring gear models.
flightfarm
Member
My battery is in the back. My empty weight is 1176lbs with cg at 9.3inches
yours was originally built with the O-320 being a GC? Or does the -320 make it a GCA?
flightfarm
Member
Originally had the O-290. Converted to GCA in the 1960s. Had the O-320 A2A installed. Then later on the O-320-E2A was put on.
cool, thanks for the info
That’s pretty far forward. My 1969 7GCBC is 1194lbs at 12.6” with the battery on the firewall.
flightfarm
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Reasons why I think I’m going to have it weighed again. Seems off to me
Bob Turner
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I think I agree - my 180 Dec is 12"; a factory weigh-in for a 2003 GCAA is 12". We had for a while a 7ECA with firewall battery at 10", but that was a mechanic weigh-in, and I trust those like not at all - I have seen way too many errors.
In fact, for the Super Cub (complicated by two data in the same AFM) I have never seen an absolutely correct weight and balance document. I have seen the wrong formula, the wrong main gear location, putting a single item into the mix with the most forward datum while everything else was wing leading edge . . . The good thing is that errors like that allow me to go back to factory weight and CG and compute, which often results in a two place airplane!
Edit: Before you go to that expense, double check the math and the formula. Mechanics do not often have extensive experience in mathematics and geometry. And there are formulae out there that are just plain incorrect. Find the Aeronca document, and use that.
In fact, for the Super Cub (complicated by two data in the same AFM) I have never seen an absolutely correct weight and balance document. I have seen the wrong formula, the wrong main gear location, putting a single item into the mix with the most forward datum while everything else was wing leading edge . . . The good thing is that errors like that allow me to go back to factory weight and CG and compute, which often results in a two place airplane!
Edit: Before you go to that expense, double check the math and the formula. Mechanics do not often have extensive experience in mathematics and geometry. And there are formulae out there that are just plain incorrect. Find the Aeronca document, and use that.
A while back I did some digging on pp weights and ratios, turns out the o290d2 was a very nice middle ground motor for planes like these, that is to say between the o200 and the o320.
I'd be doing everything I could to get your nose lightened up... sensenich ground adjustable carbon prop, putting the battery as far back, light starter, and alt.... etc. Is your oil cooler on the back of the motor?
O-290-D2 135 hp weighs 233 lbs = 1.73 lb per hp.
O-320-A1 150 hp weight 244 lbs = 1.63 lb per hp.
O-320-B1 160 hp weight 250 lbs = 1.52 lb per hp.
I did some fabric work on a gcbc a while back... that tail was super heavy, lifting it was a bear!
flightfarm
Member
I finally got around to getting my 7GC reweighed. The original W/B was empty 1175lb @ 9.3" CG. Today it came out at 1138 lb @ 10.4"CG. We're thinking the past W/B had an error somewhere after it was rebuilt. Still nose heavy but better than were it was.
Bob Turner
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Sometimes they forget to drain the fuel?
Beware of weighing the 7AC - you will gain 100 lbs. Not true with the 7ECA, although that one with a 150 or 160 can be nose heavy. Factory weights on those were honest.
Beware of weighing the 7AC - you will gain 100 lbs. Not true with the 7ECA, although that one with a 150 or 160 can be nose heavy. Factory weights on those were honest.