not sure if this is what jasons rear seat shows..

but if you make it so it pins/locks top of cross bar as it also locks into floor, seat back can be weaker because it picks up the strength of cross tube, and cannot bow far....

kinda like how the bottom pins overcenter/lock in my -12 seat bottom....

Is this what you guys are talking about for leading edge skins, This is the leading edge tank bay weighs 15 oz., Have the mold for the trailing edge tank bay done and tip bow transition done. Transition parts weigh 4 oz each. False spar for flap bay and 5' leading edge skin molds in process, now if i can just get the FAA to buy off on it. Combined with the carbon fiber tank covers looks like a total of 18# lighter for a set of wings.

D.A.
My concern would be at the point where the cap strips contact the top of the nose ribs. The grain direction there would not have any side load strength. Rather than lightening in an area where grain strength might be in question. An engineer and builder friend pointed out that the rectangular gussets used through out the rib construction have corners that do not add to the strength; they just add weight. The picture below shows the gussets trimmed of the unnecessary corners. How much weight is saved? There are hundreds of gussets in the wing and the weight adds up. My guess, including glue, is a savings of about a pound. Not much but it does add up and there is no loss or compromise in strength at all.

Marty57

Easy to set the gross at 1320. Not so easy to get the empty weight at 800 or less to make it work.

I built some wings with 14" rib spacing, ditched he intermediate leading edge rib and used .020 2024T3 leading edge. Stamped ribs are heavier than the ones with aluminum cap strip. Carlson ribs look to be pretty light. You can buy the T cap strip from them and build your own and save $$$. I used aluminum drag

This is how I am trying for a lightweight wing.

There are two calculations being talked about here. Referring to the Piper PA-12 weight and balance form(s) for information here is what you need to know. The red is where you might introduce your non standard weighing at the tailWHEEL (measure from main wheel axle centerline to tailwheel axle centerline in the level position.

One is the aircraft Empty Weight Center of Gravity, which you can think of as the MECHANICS weight and balance for adding and removing equipment from the airframe; this uses the wing leading edge as the datum. Your mechanic is supposed to be smart enough to work with negative numbers (don't hold your breath). No offense to the Cub savy mechanics on here! All the distances in the TCDS are referenced from the wing leading edge.

The other is the Actual Weight and Balance which you can think of as the PILOTS weight and balance for everyday calculations; Piper tried to help by moving the datum 65" forward of the wing leading edge so us stupid pilots didn't have to work with negative numbers. The pilot, baggage, fuel, etc. arms in the "Flight Manual" use this datum.

When you weigh your airplane as Piper did there will be a scale under each main wheel and one under the tailpost / tailwheel .

The formula to give you the Empty Weight Center of Gravity (MECHANICS number) is:

1.5 + ((weight at tailpost X 188.7 / your measurement) / total weight))= EWCG in inches aft of datum (wing leading edge). This is your MECHANICS number.

Add 65 to it and you now have the PILOTS number for the Actual Weight and Balance aircraft CG.

Hope this helps,

John Scott

Know thy systems. The P leads on the mags ground out when the switch is in the off position. If a P lead has an open (break or bad connection) the mag will be hot. That is why one always does a quick mag check by turning switch to off for a quick instant before shutdown - to catch it before the condition can go on for long.

Mark J

Folks

First let me say "Thank You" for all your inputs.

Lets talk weight and drilling brake rotors out.

A Supercub friend told me he drilled his rotors and saved 1.5 pounds (24 oz). I don't think he is quite as fastidious about all this weight stuff as I am, or perhaps his rotors are much different than mine, but at any rate I had my rotors drilled to save weight. They now look like this.......




The Bottom line.......

The rotors before drilling weighed 45.300 and 45.050.
After drilling they weighed 41.145 and 41.375

Net saving 7.83 Oz.

Not much for 200 dollars. So, I am now of the opinion that this is not a very cost effective weight savings area. Which brings up another point. How much is too much? I think the "cost per pound saved" value will vary from person to person but once you get over 100 dollars per pound you are getting pretty fanatical. With things like light weight starters and alternators you are in the 50.00 dollars per pound zone, i.e. a 500 dollar starter saves you 10 pounds. This effort saved me 1/2 pound and thus the relative cost was at 400 per pound. That is way too much for me and I will chalk this one up as a mistake. But now you know the hard facts and can make your own personal choice.

Hope this helps

Bill

Thanks for the nice comments folks. Docstory - geez I sure hope not.

FLYWHEELS

Went down to the engine shop and weighed a bunch of 149 tooth flywheels. They pretty much all weighed the same.

Average normal 149 tooth flywheel = 106.920oz/6.682pds
Mine after cutting off the pulley = 86.915oz/5.432pds
Skydynamics flywheel = 47oz/2.937pds as reported on their website (http://www.skydynamics.com/frame.htm)


So cutting the pulley saves just 1p 4oz. Really not all that much. But going from a full normal flywheel to the flyweight one from Sky Dynamics will save 3.75 pounds. Thats pretty significant, especially since that weight is way out front.

This is my flywheel before trimming the pulley off



This is my flywheel after trimming the pulley off. My good friend Tom popped it on his lathe and had it done in a flash. Some like DW and Doug K have also drilled out theirs



This is a picture of the Sky Dynamics magnesium Featherweight flywheel.



Hope this helps. You will have to decide what works for you.

Bill