Champ Empty Weight help needed

Post-War Aeronca Champ airplanes
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dlrude
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Champ Empty Weight help needed

Post by dlrude » Fri Jun 22, 2018 14:53

I looked at a 337 from 1956 for the Champ I am working on. 1956 was the last time that it was actually weighed, until now.

In 1956 gravity must have been different from now because every scale number ends in zero, example 440, 70, 430, 50....

At that time the EW also ended in zero, 940 lbs.

In 1956 the airplane had starter, generator, T&B. ROC, Selsyn Compass, radio, inst & nav lights, oil filter, 26 gal. wing tanks, C90, Hanlon-Wilson mufflers, metal prop, full aluminum sheet metal cover over cabin from wing TE to windshield and metal covers over the wing tanks.

I took out most of that stuff but kept 26 gal. wing tanks, C90, metal prop, changed to B&C starter and 11 lb. Odyssey battery, kept ROC, T&B and added a forward cabin skylight and shoulder harnesses and a few pounds of metal repairs.

After removing that stuff and making my additions the EW is 969 lbs! Does not make sense to me.

Does 969 lbs. sound like a nearly correct EW for a Champ outfitted in the way I described?

Could the 1956 weighing be bogus? Did the 1956 EW sound nearly correct for a Champ outfitted in that way?

Thanks, Dave R.

bob turner
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Re: Champ Empty Weight help needed

Post by bob turner » Fri Jun 22, 2018 20:54

The only help I can give you is - stay away from scales. If your new weight somehow made it to a 337, you are pretty much doomed to a single place airplane. Cubs are the same way - wheel them on to a set of scales, and become either a single place airplane or an outlaw.
For insurers and the FAA paperwork is extremely important. If you get weighed, then ignore your new weight, your insurance might be void.
For Cubs and early Champs, always compute. Never weigh. Does that help?

Paul Agaliotis
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Re: Champ Empty Weight help needed

Post by Paul Agaliotis » Fri Jun 22, 2018 22:44

Dave,
That sounds about right. These little planes get pretty heavy with all of the stuff we think we need now days.
Paul
Mailing Adress : Paul Agaliotis 2060 E. San Martin, San Martin,Calif. 95046

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rkittine
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Re: Champ Empty Weight help needed

Post by rkittine » Sat Jun 23, 2018 08:15

Even if you take out all the add ons that you think are there, you may find that the weight (on an accurate set of scales) is still well above the factory listed weight. I have seen replacement floor boards that are thicker that what came from the factory, the addition of carpeting, more noise reducing insulation in side panels, heavier sheets of ply under the nose tank etc. You may have an aftermarket tailwheel that you have not considered, etc.

In any case, I have yet to see a Champ in recent years that comes close to the listed factory weight and again I you should also be suspect of the weight you saw from the past as I have seen some pretty unprofessional weighing schemes.

Bob
Robert P. Kittine, Jr.WA2YDV
West Nyack Aviation, L.L.C.
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dlrude
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Re: Champ Empty Weight help needed

Post by dlrude » Sat Jun 23, 2018 13:12

Thanks for the comments.

I guess I believed that old EW of 940 too much and was thinking how I was reducing it by taking out the generator, radio, electric compass and so on.

Was disappointing to see that it gained 30 pounds after all that removal and conversion to lightweight starter and battery.

Of course I made some additions too - shoulder harness and I got leather seat cushions.

Will have to see what I can remove or alter but at best I could pull of 40 lbs if I also removed the battery & starter.

Regarding the accurate scales comments can you elaborate? How much diff did you see? Can you talk about the what the accurate scales were and what had been used before that?

I did my initial weighing with new bathroom scales- I want to get an estimate before I would even consider flying it to a site where I can get it weighed on real scales.

I found out two days ago that I can rent certified scales and bring to my hangar and may do that next week so I may not need to fly to the scales after all, we will see.

Dave R

bob turner
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Re: Champ Empty Weight help needed

Post by bob turner » Sat Jun 23, 2018 20:57

These aircraft gain weight, probably because the factory scales were wrong. There is no proof that the factories fudged, so compute!

If your 1956 weight looks legitimate, compute from that.

If you want to know what your aircraft really weighs, weigh it, but do not do it with the help of a mechanic, because if you do, he/she must enter it in aircraft records.

Or, go ahead and weigh it on the certified scales, and enjoy a single place aircraft - or worse, fly it overweight.
We have a Supercub on the airport with a useful load of 400 lbs. Its previous owner put a note on each and every 337 that it would be weighed at assembly. Do you know how far you can go legally with two 190 lb pilots in that bird? Even my J-3 can legally lift 480 lbs, with starter and battery.

If they (the Super Cub guys) had taken the factory weight and added the mods, it would have been 100 lbs less. You cannot add 100 lbs of paint to a fabric job without having it crack, or worse.

All this does not seem to be true for Citabrias or Decathlons - rebuild and reweigh an early 7ECA and the numbers will look like the factory numbers.

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hangerash
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Re: Champ Empty Weight help needed

Post by hangerash » Sun Jun 24, 2018 22:44

Someone please correct me if I'm wrong, but I understood the factory weighed the production model they certified with the FAA and every airplane after that had the same basic weight and appliances were calculated and added on.

That is why the empty weight from the factory is so hard to duplicate as I understood it.
Richard

Paul Agaliotis
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Re: Champ Empty Weight help needed

Post by Paul Agaliotis » Sun Jun 24, 2018 23:14

Most manufacturers weigh one example. Until something in the PC, that would cause a new weight is modified, no new aircraft are weighed. That's why all of the items in the TCDS have weights, so you can do a calculation W/B of installed equipment.

Most of the synthetic coverings used are 30 to 70% heavier than the cotton used. We tend to make sheet metal from .032 rather than from the .016 originally used, a 100% increase. Interiors that are more suited for brothels than aircraft, disc brakes, starters, radios, batteries, added fuel tanks, the list is endless. Keep them light and you have a wonderful flying airplane, get them heavy and you have an underpowered Citabria.
The best compromise would be a non-electrical Champ with 1 wing tank and a C85.

Paul
Mailing Adress : Paul Agaliotis 2060 E. San Martin, San Martin,Calif. 95046

dlrude
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Re: Champ Empty Weight help needed

Post by dlrude » Fri Jun 29, 2018 11:15

Here is what I found after listening to the many good comments;

------------------------ method-------------------------------------------------------EW-------RH main------LH main----tail---------EWCG
2 bath room scales moving location, leveling plane in 2 axis June 21---------970.8-------464----------444---------74-----------15.1
2 bath room scales moving location, leveling plane in 2 axis June 22---------969.8-------464----------441---------76-----------15.5
calculated from last weighing-------------------------------------------------------881.2------------------------------------------------14.6
certified scales June 28------------------------------------------------------------ 948.8-------463----------427---------70------------14.6


Dave R
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bob turner
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Re: Champ Empty Weight help needed

Post by bob turner » Sat Jun 30, 2018 22:02

So you have given up 70 lbs? Not too bad. Why is one side so much heavier than the other?

I am not sure, but I think the Champ grosses at 1220#, so you have 270 lbs of useful load?

dlrude
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Re: Champ Empty Weight help needed

Post by dlrude » Sat Jun 30, 2018 22:24

One side heavier due to not being level from side to side.

I reweighed and leveled from side to side, only 20 lbs. diff then.

My GW is 1320 lbs. based on STC I purchased, UL is 371.

I am confused about that 70 lbs. (actually 67.6) because in the calc. I included every little thing/item like seat cushion differences, insulation, shoulder harnesses but did not include weight from later fabric process (Stewarts) or repairs. 80 lbs seems a lot to me for that stuff.

I think I want to make a fabric covered tube frame Cub style door as a fun and weigh loss mechanism. The aluminum door is 14 lbs. with window.

Thanks for your help Bob.

Dave R

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rkittine
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Re: Champ Empty Weight help needed

Post by rkittine » Sun Jul 01, 2018 07:50

There have been a lot of Aluminum Frame / Plexiglass Covered doors made and installed. If you do and you have a friendly FSBO near by you might be able to get a 337 for it. That is how I got my Seaplane Door conversion got installed and legal. Still used the same door, but could be swing up and opened before or during flight and closed during a flight. Added some weight though with the piston and long piano hinge. Makes propping from behind really easy also.

Bob
Robert P. Kittine, Jr.WA2YDV
West Nyack Aviation, L.L.C.
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bob turner
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Re: Champ Empty Weight help needed

Post by bob turner » Sun Jul 01, 2018 21:30

Having both a pair of J-3s and a Decathlon, I can understand where you are coming from. I am sure a Cub type door could happen, but a structural analysis is probably required on the frame mod. There is this knowledgable guy named Dave on the J-3 forum who may be able to do the field approval for you. The other part of it - flying with it open - should be easy, since flying with the door off has an STC.

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rkittine
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Re: Champ Empty Weight help needed

Post by rkittine » Sun Jul 01, 2018 21:49

My Seaplane Door mod, which allows the door to stay on, but swing up under the wing, had to be tested based on the added drag on the one side.

Bob
Robert P. Kittine, Jr.WA2YDV
West Nyack Aviation, L.L.C.
New York, New York 631-374-9652
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