I was actually right in the middle of some W&B paperwork for a customer when I read the other post going about big Cont starters. RockHopper made this post that got me thinking since I was right in front of the math. Not sure if my math is all right as I quickly typed this, but the idea should come thru-

He is talking about heavy v/s light starters

RockHopper wrote:The weight is on the right side of the teeter totter. Move some stuff to the back of the baggage compartment to off set the small increase in weight. This non-sense of chasing every little pound out of these airframes is an exercise in wasting alot of cash.

Perhaps, but then again, ounces add up to pounds, and performance is about pounds. I have never been insane about the pursuit, but a good common sense approach and awareness about weight pays off.

With respect to being on the "right side of the teeter totter," in my experience with the birds I have been building, this is the exact opposite. With all the modding aft of the datum, we are constantly fighting forward CG. You may not think a starter could do anything at around -4" or so, but it can matter. If we gut aft, we need to try to keep her light forward as well.. which means lightweight starter, prop, etc... This can be hard though. Get a shine for a 401, install a SPW engine mount, go with Shower of Sparks etc... and you start to add in the wrong direction.

With respect to the thought of just adding more "stuff" in the baggage, all you have to do is do the math problem out and see just how hard it is to move the CG backwards.

Some food for thought: I just delivered a modified "utility style" A185F. Granted its a heavy late model bird, but the CG was 36.82 empty.

Now lets max out the extended baggage at Sta. 123 as suggested using 50lbs. This moves only moves us 2" to 38.86.

Now lets max the rear baggage with 120 lbs at Sta. 99 slides to 42.10.

This is the right direction, but we just incurred a 170lb penalty to do so. Why is this important? The CG envelope of this 185 (WingX) is 34.8 - 46.5 at 2150 (or less) and it gets narrower as your weight increase to 41.9 - 46.5 at max gross of 3525. In the exercise I just laid out above, at the 2226 lbs, with the C.G. at 42.10, we fall somewhere near 65-70% aft in the box. Considering we have now legally maxed out the extended and rear baggage, there is nothing more we can do to try to get her into the last 30% of potential C.G. Now if I jump in the bird and gas it up with 500lbs of fuel, the CG shifts 0.5" forward, which can cause adverse effects. E.G., the plane wont be as fast, the trim will be maxed out on landing, and she will stall at a faster airspeed etc etc etc...

Now lets look at going back to empty and swapping out the heavy 401 3 blade black mac and energizer starter for say a 2 blade MT and Skytec. Figure 35 some odd lbs for the prop and 9 for the starter. My numbers for the prop etc may be off, but it doesn't matter for the exercise... If I do the math out, this weight savings up front moves the C.G. from 36.82 back to 37.34.

I may have lost everyone, but here is my take-away.

Adding 170lbs aft moves the CG 5.3" aft. Removing 44 lbs up front moves the CG aft 0.5". Clearly the cheaper way to move the CG is to just load her up with crap... But that comes with its own penalties. The good thing about lightening her up front, is you always have the option of moving the CG those 5" with crap.

The real question is just how much all of this is worth to you? Perhaps Cessna had things right to begin with??? Putting that stock battery back in the back moves the CG just over 1" aft...

Just food for thought.

Along the same thought lines.....

Just say you were starting with a relatively heavy late model 180. Factory float plane, three blade prop, O-520 engine, Selkirk fiberglass interior, older King radio stack, extended baggage, etc......

Just how much weight could one expect to lose by putting the airplane on a diet? Short of changing the engine and prop, that is.

New panel with glass, eliminate the vacuum system, light weight interior... what else?

Could we reasonably expect to lighten it up by a couple of hundred pounds? one hundred? And how much weight reduction would it take to be regularly noticeable in daily ops?

I know in my C-170 I can tell a difference in a couple of hundred pounds. Ten or twenty pounds and I'm not sensitive enough to notice....

Just curious.

Instead of adding 170 pounds to baggage, how much would be needed way back in the tail for the same effect?

5 pounds of lead properly secured in the tail sounds a lot better than 170 pounds of baggage to me.

Thats a huge open ended question brother... Really depends on how much $$$ you want to cough up and bleed out.

I took around 120lbs out of my bird, but then added about half of that back in with modern mods and bush nonsense. Some general numbers for removal (not replaced weight) I have seen... 10-12lbs for heavy carpet, 10lbs for headliner, 3 for hat shelf, 22lbs for aft battery/cables, 4-5lbs per each side panel, 30lbs for old avionics, 8 lbs of orphan wiring etc etc... As far as cost... to do it "right" and pretty, a rough figure is $1k/lb with the first 25 lbs being exponentially cheaper than the last 5.

NET NET is folks can never get as much out as the "internet" says you can. First place to start is with an honest weight and balance, then work hard to get the weight back to what it said before you put it on scales. My push for weight savings is mainly to counter the additional weight that is put back in for things like the Sportsman, WingX, Bushwheels etc..

Best thing you can do is start with a light bird to begin with. I was parked next to a A185F the other day. Both birds were equally set up with engine and mods, but my 66 was 300lbs lighter than the late model. Could I feel the difference when flying the two birds... Yes.

Bagarre wrote:Instead of adding 170 pounds to baggage, how much would be needed way back in the tail for the same effect?

5 pounds of lead properly secured in the tail sounds a lot better than 170 pounds of baggage to me.

Yes, in theory... but there is no legal basis for this and many frown on it. You also must take into consideration the law of unintended consequences by adding stress from weight where it was never engineered to be.

But if you do the experiment by say adding an additional 5lbs as far aft as you could to the baby bush wheel at Sta. 264.5, in my example above, the C.G. moves from 36.82 to 37.37. This is only 0.55". The exercise still shows just how hard it is to move the C.G.

I would like to have my 182 as light as possible, specially the nose.
2 blade MT prop, MT governor, small alternator.
Wanted to get a lightweight starter , but I am afraid it might not work to well with my Pponk.
Does anyone has a lightweight starter working reliably with a Pponk?

Bigrenna wrote:
I took around 120lbs out of my bird, but then added about half of that back in with modern mods and bush nonsense.

Thanks Greg.

So to get it like you want it you lost about 60 lbs. I would like mine to lose 60 lbs... 100 would be better but I can't make the math work to do that. And without some bush nonsense it wouldn't be as much fun.

At 1K per pound lost I think I'll just fly it as is (or maybe go on that useful load challenge that was posted here a couple of years ago).

Since I haven't been paying attention, what is the current consensus on lightweight lithium batteries in a certificated airplane? There were robust discussions a couple of years ago.

kg wrote:Since I haven't been paying attention, what is the current consensus on lightweight lithium batteries in a certificated airplane? There were robust discussions a couple of years ago.

Talking to EarthX in Anchorage last month, they hope to have a PMA'd battery later this year.
No mention of an STC or method to approve specific installs. Just a PMA.

Jose - my own investigation suggests that composite props and light starters on a 182 are only a good idea if you can mate an electronic ignition, or at least an electric starting device like Shower of Sparks to the engine to ensure no kickbacks. This is just an area of the engine that was designed for certain flywheel weight (e.g. metal prop) and is intolerant of deviation.

With respect to aircraft weight, you can go nuts trying to drop it. My philosophy so far has been that I won't do something just for that purpose alone, but if I need to replace something anyway I may as well explore lighter alternatives. I needed a prop, so I bought MT. I needed to fix some instrumentation, so I am ditching vacuum and going G5's. A couple areas I am not losing weight are on the seats and wiring. I saw some sage advice on here about seats and how those are one area you want done right; the leather will weigh more than torn thin fabric, but after hours in the saddle I won't care about the extra weight when I'm still comfortable. In the re-wiring I am running dedicated grounds and proper gauge sizes, so that's going to add weight but give a more reliable electric system with cleaner signals. Tradeoffs.

Ultimately I will lose weight on the plane in most areas, more than enough to compensate for what I'm adding back in. We'll see where it ends up after all of the bush stuff goes on, but I'm optimistic that the W&B will still be less than I started with. I am banking that on the documentation being correct, but we didn't get a scale weight before we started taking things apart so I'm trusting the paperwork was close to right.

I have shower of sparks and also the classic style starter adater which already tested can take a kickback with no problem.
So might start to re think about a lighter starter.

Which one do you guys recommend?

I am working a W&B problem for my SkyWagon and wondering how others look at this.

I have done a few mods; firewall battery, airglas extended baggage, removed dead avionics and wiring, and I sit at 1749#. This should be pretty accurate as it was scale weighed shortly before I purchased it.

I put the two fatties, my flying buddy and I, up front, ~220# each, then my daughter, ~120#, in the back seat, and 100# of ballast in the baggage areas, leaves me only room for 35 gallons. Any more than that and my COG is out the front. Looking at it my 172 works out better, except for time, to fly than the SkyWagon.

If I add Wing-X STOL it looks to help a lot, the 300# upgross allows more ballast with fuel.

How are others overcoming this problem?

Rod

Bigrenna,

I actually just ran into this yesterday. I built a super extended baggage (schubag) for my bearhawk, and always kinda figured it wouldn't be very useful in the air due to how far back it is (estimating around 90" behind the leading edge), but after taking a friends W+B, adding some weight to the tail to account for the extra interior, tubing, etc.... it still comes out that I can toss 50lbs back there in nearly any weight configuration without running too far aft CG.

This news was quite welcome because I had been counting every OZ I put back there worried that the finished airplane will be too tail heavy. Now I figure just built lite and it will all work out. And if it doesn't, I'll just move the battery to one end or the other.

Anyway, sounds to me like moving the battery up front is a bad idea if it hoses the CG that much. What's the point of that anyway, lighter weight? Here is an idea. I'm using this wire in my bearhawk, it's super light:

http://www.periheliondesign.com/fatwires.htm

It's around 1.2oz a foot lighter. So it might work well to keep the real heavy part in the back, while loosing a few lbs.

schu

I had to make a lead weight for ballast to get my C.G. where it needed to be. Here is the Publication we used to do so. https://www.faa.gov/regulations_policie ... 8083-1.pdf
Go to page 7-8 under permanent ballast. It will give you a formula to help figure things out as well.

I would think think the question for the pilot is do you have the skills to know the difference in a few inches of CG change?? Loss of top end airspeed, well, I usually have a nose or tail wind so my speed is what it is. Aft CG does make my landings better but it takes 200 lbs in the back seat to help with my skills. In general mother nature will decide how your plane preforms. With out wind involvement weight does come more into play but I think CG has to move a lot for you average pilot to notice it. So why do we chase the weight so much? For most of the flying it will not really matter, but when the wife want to bring friends, nice camping gear, or maybe good bottle and not box wine. NOW THAT IS WORTH THE MONEY!! and then of course if you want to be legal. I am just about to finish the rip out interior, clean, paint, put in black foam mod in the 180!! Not worth the 25 lbs saved!!!! We had several other issues that made it worth while in the long run. But for 25 lbs I as a pilot could not tell the difference.

Is the stock battery weight considered in the 50 lb extended baggage mod?? If not, can we add the weight to the baggage if the battery was moved??

If I was going exp and needed to fix CG I would make tool bag and emergency gear part of required equipment and put it in the tail, or as far back as possible to solve CG.
DENNY

Wa180 wrote: I am working a W&B problem for my SkyWagon and wondering how others look at this. I have done a few mods; firewall battery, airglas extended baggage, removed dead avionics and wiring, and I sit at 1749#. This should be pretty accurate as it was scale weighed shortly before I purchased it. I put the two fatties, my flying buddy and I, up front, ~220# each, then my daughter, ~120#, in the back seat, and 100# of ballast in the baggage areas, leaves me only room for 35 gallons....

Besides just the empty weight, it'd be helpful if you posted your empty CG also.
FWIW my 53 model C180 comes in at 1652# and 34.63" CG.
Forward (loaded) limit is 35", but everything I put in is aft of the CG:
fuel @ 48", bags @ 95", more bags @124", front seaters @36", backseaters @ 70".

30 gallons of fuel @ 6#/gallon + 2 front seaters at 180# each,
I come up with 2192# and 35.95" CG-- almost an inch inside the 35" fwd CG limit.
Even with just me and only 10 gallons of gas, I come up with a 35.19" CG.
So maybe it's not impossible to load out of CG fwd, but you would have to work at it.


I think that an aft-CG airplane probably flies a little better-- cruises faster, stalls slower, and is lighter on the controls,
but a fwd CG lets you carry more baggage aft.

FWIW don't be so sure of your "weighed shortly before I bought it" numbers.
I have seen a lot of goofed up W&B jobs--
forget to account for fuel in the airplane, leveled incorrectly, and just plain old arithmetic errors.
I bought my last airplane (C150TD) from the A&P/IA who rebuilt it--
turns out he'd goofed up the W&B by figuring in the t/w arm an inch off.
(I suspect he "burned an inch" with his tape measure and forgot to deduct it)

You might want to weigh it yourself,.
It's actually kind of fun, plus then you know (if you do it correctly!) that it's done right.
You'll need some (certified) scales, a level, a plumb-bob or laser equivalent, tape measure,
and a table and/or cribbing to put the tailwheel up on.
The C180 is leveled at the upper door sill fore-and-aft,
and across the fwd door sills left-and-right.

When I was into mountain bikes as a young fool I used to take a digital scale to the shop to weigh whatever I thought I was going to buy, almost always going for the lightest option. Weight removed from the bike was gone forever was my rationale. Just put down the cheeseburger I was told, it’s cheaper. While that’s true it was fun for me to see what i could get it down to. It cost about 1000 bucks a pound then too. While I spent a bunch of money in the end it was worth it to ME.

Later when I got into motorcycles as a slightly older fool I again went down this road. Ohlins suspension, BST carbon fiber wheels, etc etc. I’ve got 20k in mods in a 4K ZRX. Lipstick on a pig. But it’s way lighter and what a fun pig! Just put down the cheeseburger, it’s cheaper.......

Creeping up on being a 50 year old fool. Just bought a 180. Fat, 76, J model pig. My wallet can’t handle many of those expensive pounds in this thing but as mentioned, if something has to be replaced I will definitely explore the options. It will be satisfying to me during my stewardship of this bird if we can make her better. And lighter.

Somebody hold my cheeseburger....

Weight is not a huge issue for me, but the Skytec I just put on SPINS my O-300. The old starter just dragged the prop through.

Like. And congrats on your new bird.

Flying Dave wrote:When I was into mountain bikes as a young fool I used to take a digital scale to the shop to weigh whatever I thought I was going to buy, almost always going for the lightest option. Weight removed from the bike was gone forever was my rationale. Just put down the cheeseburger I was told, it’s cheaper. While that’s true it was fun for me to see what i could get it down to. It cost about 1000 bucks a pound then too. While I spent a bunch of money in the end it was worth it to ME.

Later when I got into motorcycles as a slightly older fool I again went down this road. Ohlins suspension, BST carbon fiber wheels, etc etc. I’ve got 20k in mods in a 4K ZRX. Lipstick on a pig. But it’s way lighter and what a fun pig! Just put down the cheeseburger, it’s cheaper.......

Creeping up on being a 50 year old fool. Just bought a 180. Fat, 76, J model pig. My wallet can’t handle many of those expensive pounds in this thing but as mentioned, if something has to be replaced I will definitely explore the options. It will be satisfying to me during my stewardship of this bird if we can make her better. And lighter.

Somebody hold my cheeseburger....

FARMAULE wrote:Here is the Publication we used to do so. https://www.faa.gov/regulations_policie ... 8083-1.pdf .

This pub lays out the practice for weight shift, but does not give any guidance on acceptable methods beyond "painting it red." As I mentioned, there are often unintended consequences when weight is added in places where it was not deigned to be.