ETLB Squawk Forums — Archive

Many moons ago (like January 2017), I posted about building metal wing tanks for my Eros. At that time, I promised to post the finished weights of my metal tanks for comparison purposes with plastic wing tanks.

Now is the time! The metal tanks weigh 4.75 lbs each with the filler neck gauge in place, including fittings and the straps used to hold the tanks in place.

As a reminder, the tanks each hold 29 litres (excuse my curious mix of metric and imperial measures).

The build is now complete, except for future trim and some more paint to pretty it up, and is registered as a basic ultralight here in Canada (C-IVCO). My empty weight came out to be 359 lbs. and with me as pilot (171 lbs.) and 40 litres of fuel (20 litres per tank) the weight is 562 lbs. My calculated C of G is at 14.3 inches (26 % of chord).

During the build, I used every weight saving trick I could think of, including thin latex fabric paint and a composite tail spring (thanks George). I do however have steel gear. The engine is a 503 Rotax, single carb, "A" type gear box, with a wood adjustable prop. I still had to add a battery and steel ballast (totaling about 15 lbs) under the nose right behind the prop to get the C of G into a favorable spot. Maybe I should eat more fattening foods? I was amazed and pleased at the thrust available from the 503 when I was breaking in the engine with the Eros tied down.

The gross allowable weight (according to my Eros manual) is 700 lbs, so I can take some sandwiches with me on trips.

Flight testing is planned for this summer, which unfortunately is reluctant to arrive in my part of Canada this year.

Those of you who have read my post and have worked out the numbers will have noticed that they don't add up! After posting, I checked my notes (the numbers seemed off even to me), and my weights with fuel were for 20 litres total (not 40).

Good job Dave!  I just installed my custom alum tanks yesterday and I never weighed them, not taking them out now just to satisfy my curiosity. Used .050 aluminum. What did you use?
Maybe my memory is poor....OK it is poor, but I thought everyone adds weight to the tail for CG? But you had to add it to the nose?

Here is the link to the original post...details are discussed there.

http://www.lonesomebuzzards.com/cgi-bin/forum/Blah.pl?m-1484581785/s-11/highlight-metal+tank/#num11

I don't know how others keep the weight off the tail, if that is common. My 503 Rotax is a pull start and has only 1 carb, which is perhaps lighter than what some would use. I didn't mind having to install the battery up front since it had to go somewhere, but the steel ballast was a bit of a disappointment, and delayed the project a week or so.

Quoted from Dave Walker Many moons ago . . . .

I still had to add a battery and steel ballast (totaling about 15 lbs) under the nose right behind the prop to get the C of G into a favorable spot. Maybe I should eat more fattening foods?

. . .

Great news,
Another project completed !

May be I got this wrong, but if you need to add weight to the nose section, you need to shed a few lbs by dieting, right ?

I believe you are correct. My center of mass is behind the C of G.....maybe I'll just lean forward as needed. I don't want to have lose weight!

most of the time, CG is supposed to be at or near the center of the pilot, however that can change a bit.
Losing weight may help Weight, but it might not help balance, other than minimally.

Have you done your Weight and Balance calculations?
If so, you should know the CG, and can figure out how far it is from your belly button.