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Where to start removing weight

A

alexstoll

Registered User
Hey folks, it's looking like I'll be the newest member of the super cub club here in a few days! Plane is a late 50's PA-18A model in decent shape with a lot of useful things having been done to it already, it's just a little bit of a beefcake for an O-320 at 1240 lbs. The owner before the last one added a lot to the panel - full six pack with vacuum system, think it was even IFR certified at one time. It also has the belly pod fuel pump still installed, though no pod. So, how do I go about getting the weight down? Especially important as I'll be adding back onto the weight with most likely a borer prop (maybe composite but open to opinions), big o' tires, etc. Seems that the ag version was a little heavier from the start with the hopper door and reinforcements, but it shouldn't have been this heavy. I'd like to keep the starter and electrical for sure.

So, here are my ideas for where to pull weight out, I'd appreciate opinions on which are most worth doing.

* Remove vacuum pump, attitude indicator, DG => Around 15 lbs
* Remove the belly pod fuel pump system => 5lbs maybe
* Lightweight starter, lightweight under-seat battery, rear baffle oil cooler => 20 - 30 lbs
* Seats are really nice but seems heavy, maybe there's 5 lbs there

That's optimistically around 50 pounds for not a ton of money, which gets me towards 1190 or so.
Any ideas out there for further weight savings? It already has Univair sealed struts, so no dice on the airframes aluminum ones.
 
That's what I always say when I see weekender type cyclists spending 1000's to remove a few ounces from their bikes, while happily ignoring the pounds that would be free to loose if they just rode the thing more!
 
Sounds like you've got it pretty much nailed. The only things you could consider doing in addition is taking the springs out of the front seat back and using a fabric covering to save weight there. Front seat bottom you'll want to pull the springs and use a sheet metal seat pan for easier access to the underseat battery.

Seat cushions can be heavy depending on how old they are and the materials used. Might look into Sport Aero seats as they are pretty light. Rear seat is another place to save some weight by going to something like the Atlee Safari seat.

Honestly if you're under 1200lbs it's gonna be fine. Most 150/160hp cubs clock in around 1150ish and up to 1200. Just get your tires and prop on and get some brake boosters so you have the stopping power to bring that weight to a stop.
 
How much cub time do you have? Might be best to spend all that upgrade money on gas. I know very few pilots that can actually tell you the difference between a 1/4 tank or full tank of fuel (75 lbs) without looking at the gauge. Nothing wrong with doing upgrades when needed, but for everyday flying a cub really don't care about a little extra weight. I would NOT move the oil cooler to the back of the engine, Makes working on mags, oil screen, muffler a pain in the butt. I do like going to a newer battery when the time comes, replace all the cables when you do it. You can put all you survival gear back where the battery was (duckbill anchors, ropes, tools, ect) if you want more weight in the tail. What part of the country are you flying in and what is the mission that will determine the tires and prop. DENNY
 
This gets deeper into it but what kind of floor is in it? Metal? Wood? What thickness? I can get into details on flooring that will open eyes about weight differences that a lot of people might not realize.

Extended baggage? Upper? Lower? Secondary exterior baggage access doors? This stuff adds up and if you don’t need them for your mission it’s something to consider.
The devil is always in the details and if you’re a complete weight nerd there’s things that can be looked at with a critical eye and an open wallet to achieve a goal. Swapping out certain items within legality parameters with aluminum for steel, carbon fiber for either one etc.
Panel stuffed full of “might need that” items, depending on your flying needs, there’s some pounds to be saved there.

Not only your starter but what size alternator are you running? Need to get weigh off the nose? Consider a direct drive alternator and lose the alternator brackets, the drive belt, and even the belt drive sheave. Could even go to a replacement lightweight ring gear support if you wanted to spend the dough.
I could go on into smaller details like various hardware options if you want to really split hairs but that stuff is mostly choices during the build phase. There’s a fair number of ounces to be had in that category if youre paying that much attention to the tiny details.


Sent from my iPhone using SuperCub.Org
 
Seats are likely more than 5 pounds. Remember the 90% rule. You don’t need a 5 hour seat if 90% of your flights are less than an hour.
floor boards are often much heavier than necessary
light weight starter, alternator and battery will go a long way.

It’s a start. Tom Ford is the expert on getting the weight out

Hope this helps

Bill
 
If you can live with the idea of hand propping, here’s a weight reduction in the right spot.
11D5535F-2CE5-45A3-9733-3FD4E504007A.jpg
 

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Aluminum struts, no upholstery, leave it in silver for the fabric, no color...move the battery closer to the starter.
 
Aluminum lift struts will take a bunch of weight off right away. Ditch the vac system, does it have old radios? Get some trig, and use the built in intercom. Metal headliner is heavy. Ditch the tank covers for carbon fiber. Narrow carbon back seat and bottom. Carbon fiber nose bowl and top cowl. Light weight starter, alternator and oil cooler. You can use the stock location. Carbon fiber pulley covers on the wing and inside the fuselage. Sport aircraft seats are light and comfortable.


Sent from my iPhone using Tapatalk
 
what ever you end up doing I'd like to see some b4 and after panel pics especially. I went through the same process 6 years ago and regret not yanking the vacuum system. Mine is an A model as well and at 1147 lbs empty now
 
Whew that's a lot of help, thanks folks! I hadn't considered the floorboards, new ones would add a lot to to the plane aesthetically. Also really like the look of that sutton exhaust. The 100 hour engine swinging muffler AD seems like a real pain especially as I fly a lot. I think the panel will look a little empty for a while, maybe there's a full panel redo down the line to get the electrical there as well, but it's lower on the priority list.

Just looked at the Atlee Safari Seat - wow it saves a ton of weight, not cheap for a folding chair though!

Aluminum struts would be great but I've already got the Univair sealed struts, and can't justify that big cost.

I like that lightweight radio idea, currently has a big old brick of a radio in there.
 
don d said:
The pilot!!
Click to expand...

Don is quite possibly the smartest guy here.
Why do we leave no stone unturned to minimize every extra ounce of weight?
Now we add Bushwheels, heavy prop, heavy shocks, big tailwheel, belly pod, tool kit, survival gear,
bigger fuel tanks, etc. Throw a buddy in the back seat, add all our camping/trip gear, fill with fuel
and look for a 300' strip to land on.
I'm a novice at cub knowledge compared to most of you......but I've been flying them since the
early 70's. They always get me where I'm going........light or heavy......and always fun!
 
So I'm kind of getting to the understanding that they fly fine regardless. Part of the motivation for removing the vacuum and instruments is that I don't want to have to fix them when they break. I'm thinking I'll start wit the few minor changes and then just fly it for a while.
 
I'm always working on the pilot weight reduction!

It was mentioned in your first post; the battery. EarthX certified battery is 5.4 lbs. That's usually a great weight reduction.
 
3 or 4 years ago the top 5 out of 15 in the bush class at Valdez all came in within a combined distance (takeoff and landing) within 9 ft of each other. The weight difference between heaviest and lightest of the 5 planes was around 300 lbs. The top 5 had a fly off at the end and the winner was at least 200 lbs heavier than the light 1,000 cub. Just go have fun, you need a lot of hours in a cub before weight will matter. If you are going to fly in winter I would stick to a stock or hotrod muffler.
DENNY
 
cubdrvr said:
Don is quite possibly the smartest guy here.
Why do we leave no stone unturned to minimize every extra ounce of weight?
Now we add Bushwheels, heavy prop, heavy shocks, big tailwheel, belly pod, tool kit, survival gear,
bigger fuel tanks, etc. Throw a buddy in the back seat, add all our camping/trip gear, fill with fuel
and look for a 300' strip to land on.
I'm a novice at cub knowledge compared to most of you......but I've been flying them since the
early 70's. They always get me where I'm going........light or heavy......and always fun!
Click to expand...

Duh, it's easier to make the cub lighter
 
If you have never flown any Cub type that is really light you can't understand what a delight a lite Cub is to fly. Not talking take off performance but just a sweet flying Cub. I have flown over 20+ different cubs and the best flying one of them all is a 37 hp E2 Cub at 554 lbs. A really ratty 65 hp J3 with pealing paint and 50 year old fabric comes in second. The 4 90hp pa11s come in third. If you haven't flown a Cub under 700 lbs you wouldn't understand that less weight is the biggest performance mod



Glenn
 
Raised by wolves has a very light nice 160 hp 18. Ask him how hard his 3 member gets flying a C90 Pa11

Glenn
 
Start at the dinner table. Unless your a 120lb guy already, you best dollar to weight reduction is quit eating bread and drinking beer.


Sent from my iPad using Tapatalk
 
We don't all have the disposable cash Mr. Ford invested into his cub to make it light...

So some ideas and methods that work well. My budget dictates a method of financial need-

Remove stuff that Is not used: your fuel pump for the belly tank is a good example. Put it in a sealed bag and store it for the time you decide to head up here to Alaska, and want the fuel.

Instruments? Maybe wait until the vacuum pump fails, then pull them. But that is a personal choice.

Next, upgrade when things fail- instruments, either remove or replace with lighter options. Battery switch to light weight (currently have Earthx); radio to smaller/lighter, starter and alternator...

Third are dollar for pound ratio options: floorboards, side panels (what do you have as these are sometimes very heavy), Starter, Alternator, Carbon all over where possible....

A guy can double the price of the plane with upgrades. Often times practice and acceptance helps a bunch. Funny thing is, they fly better adding some weight: Thurst line, Keller Flaps and VG's make them nicer, but are weight.

One other big ticket item might be the fabric. If it has Razorback, that is a lot of pounds on the bird.
 
It's all about compromises. Weight, balance point, performance, safety, convenience, comfort, range and even appearance are interacting factors. Change one and it affects all of the others. Go to extremes on one of these things and you get a plane that loses out on the others.

So everyone has an ideal in their mind of what their plane should be like. I personally think that the overall capabilities of generalist plane is more suited for me than a specialist plane. I have a wife with a medical issue that makes her dependent on me, so I personally value safety pretty highly over everything else. That means I'm not going to be landing on 400 foot sandbars anyway. I want to have a really good medical kit in the cargo area at all times, so it is a fixed part of the weight and balance. I also want the weight and balance shifted more toward the front because that means less chance of a ground loop, so one of these days when i can get good advice on how to do it I want to get an under the seat battery. My plane came with a lot of older panel instruments so I downsized by getting rid of all of the vacuum pump driven stuff and got a lightweight Aspen Evolution PFD and added a JPI engine monitor. I want to use the Cub for maintaining my IFR proficiency and I also want to be IMC capable in case I get caught in a VMC into IMC situation (safety again), so I still have a little more weight on the panel than somebody else would prefer. Not trying to offend anyone, but I would rather not travel at the speed of a constipated turtle and 8.5 tires are probably good for any maintained grass strip in the lower 48, so 8.5's it is. Big tires would sure look cool though. I'm OK with not being one of the cool kids...

No, not really, but that's what I keep telling myself.
 
Last edited:
cubdriver2 said:
Raised by wolves has a very light nice 160 hp 18. Ask him how hard his 3 member gets flying a C90 Pa11

Glenn
Click to expand...

Shhhhh don’t tell them that. A 90hp supercub fly’s nice. But a light weight 160 is a dream. pa-11’s,they aren’t that nice to fly. Just kidding. If I was flying by my self all the time a -11 would be the most fun. Like someone said CG, it’s sucks adding 10 lbs to a light cub but when you add it in the right place it makes a difference


Sent from my iPhone using Tapatalk
 
DENNY said:
3 or 4 years ago the top 5 out of 15 in the bush class at Valdez all came in within a combined distance (takeoff and landing) within 9 ft of each other. The weight difference between heaviest and lightest of the 5 planes was around 300 lbs. The top 5 had a fly off at the end and the winner was at least 200 lbs heavier than the light 1,000 cub. Just go have fun, you need a lot of hours in a cub before weight will matter. If you are going to fly in winter I would stick to a stock or hotrod muffler.
DENNY
Click to expand...
It would also be interesting to know the cgs of the 5 cubs and if there was a correlation with aft cgs. I suspect, like always, it’s more about the monkey sitting in the seat and who had a good day.
 
cubdrvr said:
Don is quite possibly the smartest guy here.
Why do we leave no stone unturned to minimize every extra ounce of weight?
Now we add Bushwheels, heavy prop, heavy shocks, big tailwheel, belly pod, tool kit, survival gear,
bigger fuel tanks, etc. Throw a buddy in the back seat, add all our camping/trip gear, fill with fuel
and look for a 300' strip to land on.
I'm a novice at cub knowledge compared to most of you......but I've been flying them since the
early 70's. They always get me where I'm going........light or heavy......and always fun!
Click to expand...

You have motivated me to go on a diet. :lol:

Weight savings is a never ending deal, it is like crack, you just want more or in this case less. ;)
 
Years ago, we went through a “lightening” program on our heavy Cubs. Lightweight alternators replaced heavy generators (and work better), lightweight starters, aluminum oil coolers on rear baffle, and under seat Odyssey battery. A few other simple things, but generally, that took an average of a bit over 40 pounds off each plane.

Vacuum system: They’re heavy, and prone to failure. In a Cub, you likely won’t need it much, and when you do, it may not be functional. I’d vote to remove it, and the gyro instruments associated. But that said, I’m also a believer in a “get out of jail” attitude instrument. Look at uAvionix new AV-30C attitude gyro. Super light, multi functional, etc. add its temperature sensor, and it calculates and displays Density Altitude. It switches back and forth between Attitude instrument and DG.

Put one of those in place of one of the gyro instruments you removed. Multi functionality, and the things weigh hardly anything.

MTV
 
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