Tail Ballast for PA-18
- Thread starter Cardiff Kook
- Start date
skywagon8a
MEMBER
SE Mass MA6
That questionable internet advise comes from the experiences of an experimental test pilot who did the flight testing on an airplane with 96 pounds of ballast located at the tail (behind the tailwheel). That ballast was movable gasoline. The decision and design to place that ballast in that location was done by a pair of highly respected engineers, with the final result being the issuing of a full type certificate A6EA by the FAA. Those engineers also did all the design and stress work on the Helio Courier wings. That same test pilot has also accomplished flight testing on PA-18, DHC-2 and Pilatus PC-6 (with approval of the engineering department of Pilatus), all with considerable ballast at the tail, all with positive results.
Basic engineering principles may suggest what you say is wrong, experience says otherwise. Removing 4 pounds of aerodynamic download on the tail by adding ballast. removes 4 pounds of necessary lift from the wing allowing that lift to be used more productively while reducing the trim drag.
If you believe that weight way out there is good ask any beaver drivers how much they love tip tanks.
You do not make any sense with your statements. So he is a test pilot big whoop.
Forgive my Ignorance but I know of two test pilots that ground-looped perfectly good airplanes. Just ask Steve he knows at least one too.
And everything in aviation has been engineered including all the known failure points with ADs on them now.
Any extra weight outside of the centre slows down control response -- if you do not believe it just try it Tip fuel or tail
ballast does not matter the plane is less save to maneuver, particular in tight or adverse conditions
So please do not sucker someone into doing something that is less than desirable.
Lots of strange things have been done over the years and decades to fulfill a specific purpose like long range ferry flights.
That does not make the mods desirable for other flights.
Thats my 2 cents worth over and out.
You do not make any sense with your statements. So he is a test pilot big whoop.
Forgive my Ignorance but I know of two test pilots that ground-looped perfectly good airplanes. Just ask Steve he knows at least one too.
And everything in aviation has been engineered including all the known failure points with ADs on them now.
Any extra weight outside of the centre slows down control response -- if you do not believe it just try it Tip fuel or tail
ballast does not matter the plane is less save to maneuver, particular in tight or adverse conditions
So please do not sucker someone into doing something that is less than desirable.
Lots of strange things have been done over the years and decades to fulfill a specific purpose like long range ferry flights.
That does not make the mods desirable for other flights.
Thats my 2 cents worth over and out.
SOOOOOO when you say neutral what does that mean? To me it would mean if I had 24 turns on my trim it would be 12 turns. Which in a cub is not neutral in level flight. The indicator may be in the middle but that is as useful as tits on a boar hog. Are you changing trim for landing/approach airspeed? Like I said so many factors, verbiage means a lot. If we could all stand next to the plane in a few flights the answers would be easy. Well maybe not that easy because your plane/gauges/weights could be all jacked up! But in general it could would be easier.
Denny
skywagon8a
MEMBER
SE Mass MA6
supercub83a
SPONSOR
North Pole AK
Has anyone seen or installed a baggage area in the tail section or aft of the aft extended baggage? I would like to locate my tool kit there in my very nose heavy cub when flying lightly loaded. Useful weight. Ive thought about making a mini carbon fiber pod that would clamp to the longerons at the tail clean out panel or maybe in place of a tail clean out panel. Experimental of course.
Cardiff Kook
PATRON
Sisters, OR
Neutral to me means the rear of the stabilator is in line with the front of the elevator. Not sure how many turns that is…
BC12D-4-85
SPONSOR
Fairbanks, AK.
I guess what I asked in #4 was....fly and trim neutral stick pressure while level in cruise with normal single pilot load, then land without adjusting the trim. It's ok to do that. Note the front of the stabilizer (or attached jackscrew yoke) relative to the potential range of vertical travel. Is it all the way down in the slot or against the longeron below, or about midway, or higher up? Full nose up trim (to offset a forward CG) would be leading edge of the stab all the way down for example, full nose down the opposite. Just curious what yours is after that.
Gary
Gary
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I have a Carbon Cub that is very light in the tail. I put on a Baby Bush Wheel and about 13 lbs of supplies on the back wall of the extended baggage. I used a Molle rack with Velcro ties.
BC12D-4-85
SPONSOR
Fairbanks, AK.
^^^^If that's your replacement alternator belt, they can be temporarily installed over the crankshaft out of the way behind the starter ring gear. Generally pulled back against the case with the top towards the upper engine lifting ring. When needed, release and hook up to alternator pulley. That's for those that don't want to remove the prop in the field.
Gary
Gary
Bill Rusk
BENEFACTOR
Sandpoint, Idaho
"Any extra weight outside of the centre slows down control response -- if you do not believe it just try it Tip fuel or tail"
This statement is absolutely false.
In a perfect world your empty CG should be close to the forward limit. This allows you to load the aircraft for camping, moose hauling, etc without exceeding the aft CG limit. But the aircraft will not be as much fun to fly as it would be with the CG closer to mid range or perhaps a little aft of mid range. If your empty weight CG is close to mid range, you may be sacrificing useful load, because as soon as you start loading you may go out of the aft CG limit.
10 pounds of lead in the tail will move your CG about 1" in a super cub. 20 pounds in the cargo compartment will move it about 1/4 ". Run some numbers for your own aircraft and figure out exactly where your CG is. If you do not know how to do this, LEARN HOW.
The aircraft will be more maneuverable, require less trim, and feel lighter on the controls with the CG towards the aft limit, and generally just be more fun to fly. My range is 71 to 79 (using the prop face as the datum) and "my" sweet spot is about 76. (Your sweet spot may be different as it is based on your own preference) That is where I like it for just fooling around on gravel bars and having fun, with no load. When fully loaded with 200 pounds of gear, floats, 68 gallons of gas and two 180 pound adults, right at 2300 gross, my CG is right at the aft limit and flys and performs perfect for me. Doc Randy has flown at this loading, as have a LOT of others. So far no complaints.
CG makes a HUGE difference in how the airplane flys and handles.
In Alaska for a couple of months, loaded heavy and having a ball.
Hope this helps
Bill
This statement is absolutely false.
In a perfect world your empty CG should be close to the forward limit. This allows you to load the aircraft for camping, moose hauling, etc without exceeding the aft CG limit. But the aircraft will not be as much fun to fly as it would be with the CG closer to mid range or perhaps a little aft of mid range. If your empty weight CG is close to mid range, you may be sacrificing useful load, because as soon as you start loading you may go out of the aft CG limit.
10 pounds of lead in the tail will move your CG about 1" in a super cub. 20 pounds in the cargo compartment will move it about 1/4 ". Run some numbers for your own aircraft and figure out exactly where your CG is. If you do not know how to do this, LEARN HOW.
The aircraft will be more maneuverable, require less trim, and feel lighter on the controls with the CG towards the aft limit, and generally just be more fun to fly. My range is 71 to 79 (using the prop face as the datum) and "my" sweet spot is about 76. (Your sweet spot may be different as it is based on your own preference) That is where I like it for just fooling around on gravel bars and having fun, with no load. When fully loaded with 200 pounds of gear, floats, 68 gallons of gas and two 180 pound adults, right at 2300 gross, my CG is right at the aft limit and flys and performs perfect for me. Doc Randy has flown at this loading, as have a LOT of others. So far no complaints.
CG makes a HUGE difference in how the airplane flys and handles.
In Alaska for a couple of months, loaded heavy and having a ball.
Hope this helps
Bill
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stoldriver
Registered User
Arizona
The further aft your empty cg is, the less payload you will have, at least with the high MGW experimentals being built. You will run out of the cg range before you hit MGW. I'm building a javron and I'm hoping to have the empty cg right at the forward limit with just me in the airplane. Of course, extreme forward cg's are generally less efficient and often don't have the best flight characteristics. You can fix that by adding ballast aft. You can add a lot of weight in the baggage compartment or a little back at the tail. Using Bill's airplane as an example, I chose to have Jay weld two short cross channels way aft so I can bolt weight in. Won't take much and will only be there when I'm running empty mostly. For a ten or twenty pound penalty when running empty, I get more efficiency and a better feeling airplane. I think that's a good compromise.
Wayne
Wayne
Pete Schoeninger
MEMBER
If you suspect your empty weight/C G info is in error (lots are!) you CAN weigh your airplane yourself, without an A and P license. It is not a legal weight, but if it comes out lots different from your W and B paperwork then you can have an A and P do a "legal" job.
The way to achieve a nice handling aircraft is to have the weight as near to the centre as possible. The whole Idea is to have a save and controllable aircraft through all phases of flight and even when the engine fails.
Not sure what strange mods or incorrect W&B reports lead anyone to believe that one needs to be on the outside of the WB envelope to have a good flying Aircraft, if that were true everyone that bought a cargo pod to keep within W&B limits would be a fool.
They are most definitely not.
I sure hope that people looking here for information are careful with what they read.
Before you set out to build a crazy mod cub or add weight anywhere — do yourself a favour and try a properly rigged stock cub with as few mods as possible.
You may just find it to be the best flying cub you ever had the pleasure to fly.
Not sure what strange mods or incorrect W&B reports lead anyone to believe that one needs to be on the outside of the WB envelope to have a good flying Aircraft, if that were true everyone that bought a cargo pod to keep within W&B limits would be a fool.
They are most definitely not.
I sure hope that people looking here for information are careful with what they read.
Before you set out to build a crazy mod cub or add weight anywhere — do yourself a favour and try a properly rigged stock cub with as few mods as possible.
You may just find it to be the best flying cub you ever had the pleasure to fly.
twoeightfive
MEMBER
Eagle River, AK
I used to think I needed ballast in my tail based off what a previous instructor told me in my early cub days. It was hard to get the airplane to 3 point land. Well when I flew with Denny and he saw me coming in at 60mph that will do it. My cub CG was 10.9 so even more nose heavy and my tail is very light. I trim for airspeed on final and can 3 point full stall land when coming in at 40mph and bleeding excess safely in ground effect. Although I have mostly graduated away from 3 point landings now and almost exclusively do tail low wheel landings.
Mark_Moyle
SPONSOR
Platinum
I do the same. 60#’s against the rear bulkhead real. That sand also comes in handy on an icy apron to improve traction for loading and unloading, getting pointed in the right direction…even used that sand on the icy apron in Soldotna to pull the engine after using the spinner as an unintentional nose wheel.
bda
MEMBER
Kenai AK
Can I ask the question differently?
For those of you that have done ballast testing -
How many different CG locations" did you test? ( how many different weights in the aft location)
And how different were the landing results?
ie - mid CG resulted in 98' landing roll, 3/4 CG = 89'........... interested in the numbers.
I am still trying to figure out where/what CG works best for slow landing in mine - turns out when I do the math -correctly- I am still really close to the forward CG, oops. And I am going to need a LOT of weight on the tail wheel to even get to the mid point.
I am asking so that I can prep enough trial weights.
For those of you that have done ballast testing -
How many different CG locations" did you test? ( how many different weights in the aft location)
And how different were the landing results?
ie - mid CG resulted in 98' landing roll, 3/4 CG = 89'........... interested in the numbers.
I am still trying to figure out where/what CG works best for slow landing in mine - turns out when I do the math -correctly- I am still really close to the forward CG, oops. And I am going to need a LOT of weight on the tail wheel to even get to the mid point.
I am asking so that I can prep enough trial weights.
skywagon8a
MEMBER
SE Mass MA6
BDA, My motivation for the tail ballast was that my airplane refused to spin during the phase 1 testing due to the lack of enough up elevator force to make it stall. It would only do a high speed spiral. Using the spread sheet on my computer, I calculated how much permanent weight was needed where I wanted to place it for all loading conditions. This result was so the plane would always be within the CG limits, no matter what was onboard. I ended up with about a 4" roll of lead flashing 6" forward of the tail post. This gave me an aft CG of 20.5", 0.5" aft of Piper's approved limit. The spin tests were then satisfactory. I can't give you distances except that I can operate out of a 1000 foot pond with trees on each end and cruise at 108 mph.
Set up two weight and balance examples on your computer. One for forward CG loading and one for aft loading. Then choose a ballast location for each example. Try different weight numbers in that location and see what happens to your loaded CG. Choose an amount of ballast which will favor the rear limit of 20" without exceeding any limits. Once you set this up on your computer you can quickly and easily find the best number for your plane.
Set up two weight and balance examples on your computer. One for forward CG loading and one for aft loading. Then choose a ballast location for each example. Try different weight numbers in that location and see what happens to your loaded CG. Choose an amount of ballast which will favor the rear limit of 20" without exceeding any limits. Once you set this up on your computer you can quickly and easily find the best number for your plane.
