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Thread: PA18 180hp weight and cg

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    skysigns's Avatar
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    PA18 180hp weight and cg

    what dose your 180 hp cub weigh and what is its cg arm

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    I guess you will go without answers. I have flown two 180 hp Cubs, and all I can tell you is they are extremely heavy and do not have the same feel as the lighter Cub variants. They will go straight up, but I cannot get a 200' ground roll out of them. The CG of the Wip-equipped Cub needs aft ballast to operate legally. It needed that when it had a 150.

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    skysigns's Avatar
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    Quote Originally Posted by bob turner View Post
    I guess you will go without answers. I have flown two 180 hp Cubs, and all I can tell you is they are extremely heavy and do not have the same feel as the lighter Cub variants. They will go straight up, but I cannot get a 200' ground roll out of them. The CG of the Wip-equipped Cub needs aft ballast to operate legally. It needed that when it had a 150.
    thank you bob my cub is 1123 with a cg of 12.87 with 30 gal tanks ext wings stock gear on 850 for now

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    soyAnarchisto's Avatar
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    even with extended 3x3 gear? Cubcrafters claim you can get within 1lb of an O320 depending on choice of prop. With the borer prop it's 5 lbs heavier than the O320, 1lb less with sensenich

    Maybe you ust need 35" bushwheels! haha

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    I spend most of my time in stock J3s. 19 landings yesterday.
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    I flew a 180 Supercub once that weighed 970, according to the "official" W&B It seemed a little heavier than that to me.

    Thanks. cubscout

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    Ok, Iíll bite, but first, certificated or experimental, or do you care?

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    skywagon8a's Avatar
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    Mine (Ex AB) is a bit heavy when compared with other's numbers. It has long wings and is on floats with tail ballast. Empty 1462# @ 14.4" CG. Performance is very satisfactory with good short pond (1000 feet with lots of room to spare) and climb with a high cruise speed. I could reduce the weight a bit with a lighter prop and reducing some of the ballast, maybe as much as 25 - 30#.

    Why are you asking? Is yours not doing something you think it should?
    N1PA
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    Steve Pierce's Avatar
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    Quote Originally Posted by soyAnarchisto View Post
    even with extended 3x3 gear? Cubcrafters claim you can get within 1lb of an O320 depending on choice of prop. With the borer prop it's 5 lbs heavier than the O320, 1lb less with sensenich

    Maybe you ust need 35" bushwheels! haha
    The McCauley 1A200 prop is 7-8 lbs heavier than the 1A175 on the weights I have documented. The 180 hp Super Cubs I have been involved with over the years have all bee nose heavy and several required weight in the back to be legal for flight when low on gas and flown solo. The Sensenich ground adjustable solves that issue and has a lot better performance.
    Steve Pierce

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    The two PA-18-180 that I flew towing gliders were both "restricted" and both had lead ballast on the tail. I assumed that all PA-18-180 would be the same but it seems not. Why would some be "restricted" and need tail ballast but not others?

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    Just did the weight and balance on my PA-18 Clone, Titan XIO-370, Whirlwind Ground adjustable GA-200, Oratex fabric, three inch extended gear, performance flaps and 600 tires. Engine has magnesium sump and light weight fly wheel. All in empty was 1,111 LBS, Empty CG is 13.69. Tail weight at tail wheel was 62 lbs. Not flown yet, so we will see how it performs

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    ex top cub, 0-360, long wing, big tips, pawnee prop, 31's, 3" gear, baby bush wheel, droop aileron flap system

    1274lb
    15.57"

    I know I could shave quite a bit of weight out of it. But.... it works really well as is.
    I did notice a helpful difference when I added the elevator gap seals.

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    Quote Originally Posted by planenuts View Post
    Just did the weight and balance on my PA-18 Clone, Titan XIO-370, Whirlwind Ground adjustable GA-200, Oratex fabric, three inch extended gear, performance flaps and 600 tires. Engine has magnesium sump and light weight fly wheel. All in empty was 1,111 LBS, Empty CG is 13.69. Tail weight at tail wheel was 62 lbs. Not flown yet, so we will see how it performs
    Not wanting to hijack this thread, sending you a PM with a question or two.
    Thanks, Oz

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    Quote Originally Posted by skywagon8a View Post
    Mine (Ex AB) is a bit heavy when compared with other's numbers. It has long wings and is on floats with tail ballast. Empty 1462# @ 14.4" CG. Performance is very satisfactory with good short pond (1000 feet with lots of room to spare) and climb with a high cruise speed. I could reduce the weight a bit with a lighter prop and reducing some of the ballast, maybe as much as 25 - 30#.

    Why are you asking? Is yours not doing something you think it should?

    Skywagon, your 1462# on floats puts you at about what, 1250-1260 on wheels? Not horrible by any stretch I’d say though I may be way off on that guesstimate.
    Are you using the Pawnee prop or something light?

    Oz

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    skywagon8a's Avatar
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    Quote Originally Posted by OzAK View Post
    Skywagon, your 1462# on floats puts you at about what, 1250-1260 on wheels? Not horrible by any stretch I’d say though I may be way off on that guesstimate.
    Are you using the Pawnee prop or something light?

    Oz
    Oz,
    It's never been on wheels, but I would guess at about 1300# +/-? The floats are 266# minus the weight of the landing gear. I'm using the Whirlwind 200G ground adjustable prop (41#) which I've kept at a cruise pitch since it does so well. It leaps off and climbs like a scared rabbit when set at a low pitch.
    N1PA

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    skysigns's Avatar
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    Quote Originally Posted by Steve Pierce View Post
    The McCauley 1A200 prop is 7-8 lbs heavier than the 1A175 on the weights I have documented. The 180 hp Super Cubs I have been involved with over the years have all bee nose heavy and several required weight in the back to be legal for flight when low on gas and flown solo. The Sensenich ground adjustable solves that issue and has a lot better performance.
    what do you think is nose heavy

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    Steve Pierce's Avatar
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    The CG is forward of the legal limit with the pilot and light on gas. Will have to look at the old weight and balances. Was several years ago when I was asked to add weight in the tail. I flew it and it didn't feel bad. I weigh 155 lbs soaking wet. I do like the way the fly when the CG is further back, middle or aft limit.
    Steve Pierce

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    BC12D-4-85's Avatar
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    Where the rear header tank sits might be a good place for an inline aux tank. Would serve both functions and move the CG a little more aft if desired. Thinking and then doing are often two things separated by time and money however.

    Gary

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    The 180 HP cub I flew for several years was heavy to begin with and nose heavy also. A nose heavy plane canít slow down as well as a tail cg plane. They also go over on the nose or back more often especially when low on fuel. The biggest problem I had was it consumed 10 gallons per hour as opposed to eight for the 160ís. That made it about a three hour range aircraft rather than a four hour range. I had to keep a belly tank on it all the time except when it was on floats and then I couldnít due to the float rigging even though I needed it. So it was a heavy plane made heavier yet By the additional fuel and tank I had to carry. Iíd not be inclined to have a 180 in a cub. If I wanted a 180 Iíd buy a 180.

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    Quote Originally Posted by reliableflyer View Post
    A nose heavy plane canít slow down as well as a tail cg plane. They also go over on the nose or back more often especially when low on fuel.
    Does the CG of a PA-18 move forward as fuel is burned? (Comments on FX-3 CG movement deleted. They were based on incorrect data)
    Last edited by frequent_flyer; 06-17-2021 at 01:55 PM.

  21. #21
    mvivion's Avatar
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    One of the problems when someone asks something like "Is a 180 hp Cub heavier than a 150 hp Cub" is that there are a few different "flavors" of O-360 Lycoming, and there's a few different "flavors" of O-320.

    On top of that, there are many different kinds and weights of accessories.

    A friend once converted his Super Cub from O-320 power to O-360 power, and the weight change was minimal....like 8 or ten pounds total. But, he also went to light weight accessories at the same time, which probably accounted for the lack of change in empty weight. They weighed it before and after the engine change.

    In our Cubs, we took an average of 40 pounds +/- off the basic weight of those airplanes (all O-320 powered) by changing from the original equipment generator to lightweight alternator, from the brass oil cooler to aluminum, replaced the starter with lightweight starter and changed to the Atlee Dodge under seat battery, which meant going from a big fat battery to an Odyssey battery.

    Forty pounds is huge on one of these airplanes. But, once you've done all that stuff, weight reductions become a bit more challenging. And, expensive.

    MTV
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    skywagon8a's Avatar
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    Quote Originally Posted by reliableflyer View Post
    The 180 HP cub I flew for several years was heavy to begin with and nose heavy also. A nose heavy plane can’t slow down as well as a tail cg plane. They also go over on the nose or back more often especially when low on fuel. The biggest problem I had was it consumed 10 gallons per hour as opposed to eight for the 160’s. That made it about a three hour range aircraft rather than a four hour range. I had to keep a belly tank on it all the time except when it was on floats and then I couldn’t due to the float rigging even though I needed it. So it was a heavy plane made heavier yet By the additional fuel and tank I had to carry. I’d not be inclined to have a 180 in a cub. If I wanted a 180 I’d buy a 180.
    My 180 Cub has balanced fuel injected with dual electronic ignition. It burns 8 gallons per hour at 23" and 2400 rpm giving a 5 hour range with 1 hour reserve (48 gals). Just for the fun of it I pulled the power back to 4.2 gph and it cruised around comfortably at 70 -75 mph. Normal cruise speed is 105 -108 mph. This is on floats.

    Quote Originally Posted by frequent_flyer View Post
    Does the CG of a PA-18 move forward as fuel is burned? That would surprise me since CG moves aft on an FX-3 carbon Cub. Attached graphic shows CG change between full fuel and empty for various loadings.
    (edited to correct starting fuel for loading 2)
    The CG of the PA-18 fuel tank is at 24". So, yes the CG will move forward as the fuel is burned.
    N1PA
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    Quote Originally Posted by skywagon8a View Post

    The CG of the PA-18 fuel tank is at 24". So, yes the CG will move forward as the fuel is burned.
    Thanks for making me think about it more. I found an error in the spreadsheet.
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