Since the tank is forward of the cg, I assume I should balance empty so I do not creat a tail heavy situation as the tank drains. How big of an issue is this? It has a 12oz. tank which is a fairly significant liquid weight when full.


Will I notice a nose heavy plane for the first 3/4 of the tank and then is will fly more balanced as the tank runs dry? Will I have to compensate much for this?




TIA,
Ryan

Yes, balance it empty. I may sit slightly nose heavy on full, but it will not adversely affect the performance of the plane.

i use a 12oz tank and balance it dry.
it didn't effect it that much.
i also set up accroding to the aileron gauge
i moved the cg back as i got more comfortable with the plane.
the plane still behaved beautiful..

however.. i did notice, i never flew a complete tank with a 12oz
and it seemed like it flew forever
dead sticks was down.

even on dead stick with clipped wings. it was a big gentle glider.lol

Always balance the plane with an empty tank!!! Not to be a snot but read the instruction's page 25 paragraph 68 Followed by Pre-Flight checkout. Every plane I have ever built has specified to balance with the fuel tank empty. Also High wing planes are balanced right side up, low wing planes upside down. Ok Now lets see If I can get my foot in my mouth all the way to my hip.

If you balance the plane with the fuel tank full things well happen that you won't like. I'll try to explain this fairly simply. If the fuel tank is forward of the center of gravity and you fill it with 12 oz. of fuel you have the weight of the tank, and the fuel to compensate for and you will be adding lot's of weight to the tail to balance. As you fly you will be burning some or all of that 12 oz. of fuel leaving only the weight of the fuel tank up there ahead of the center of gravity. Where did all the weight that you put in the tail to balance that fuel go. nowhere, can you say boat anchor, it still in the tail now you have an extremely tail heavy plane looking for a place to crash. It's better to have a nose heavy plane at take off because of the weight of the fuel that you are burning, which becomes less & less Which will make the Nose Lighter & lighter bringing you back to the point of where the plane balanced with an empty tank and will still be flyable.

If the situation were reversed you would of course have the opposite effect ending in the same tragedy.


The deal with balancing a high wing right side up and a low wing upside down is basicly shifting the weight of the fuse below the center of gravity to make balancing eaiser. Ok that's a fuzzy picture lets try this. Look at your high wing trainer. Your trying to balance your plane fore and aft ( front to back, nose to tail ) If you place your finger tips under the wing on the main spar,and lift, the weight of the fuse is hanging between your fingers and below the balance point. If you turn your low wing plane upside down and place your finger tips on the main spar on the topside of the wing you have the same thing. Also You might want to check the balance of your plane from side to side. Very simple to do, and it may not only surprise you, but it will also make a difference. After you have balanced the plane fore, and aft take a piece of string and make a loop in the end of it that will slip over the prop and place it around the thrust washer on the engine that your prop tightens up to. now you need a helper or need to be clever. Have someone lift the tail of the plane with a finger tip as close to center as possible. That's center from side to side, while you lift the front of the plane by the string you placed around the thrust washer, Watch to see if one wing drops down toward the floor, table top, whatever. The low wing is the heavy wing and the farther it drops the heaver it is and the more opposite control input will be required for trim. Sooooooo If it dosen't balance start adding small amounts of weight to the tip of the opposite/ high wing. I use fishing sinkers, coins, washers, anything that I can weight and / or fasten to the wing tip to get it to balance. If It's a very small amount you can many times use clear packing tape and tape it to the wingtip. Larger amounts may require cutting a small slice in the covering where you can get inside the wing and epoxy it to the inside of the wing tip.


Not trying to be a smart @#%**
just trying to help.


If there's part of this you don't understand Throw a rock at me, I'll scratch my head and try and do a better job explaining.

egor

By the way I put a super tiger .75 in my four star. I needed an extra battery pack under the fuel tank to balance right on the center of the spar. I also had to add 1 3/4 oz. of washers to the left wing tip to balance side to side. The wing balance was my fault I should have weighed the wood for the wing and balanced it before gluing it together.

good luck

Thanks for the info Guys. I knida figured to balance empty, as that is how is has been for every other plane I have built also. Maybe I didn't word it correctly, but my main concern was flight characteristics and how much they would change as the tank empties.

Most of my other planes have a smaller tank and/or closer to or on the the cg, thus this situation has not been an issue, also not an issue with electrics.. electrons draining don't cause significant weight changes

Oh, egor, good info about the side to side balance. I usually do the string around the motor shaft, and use a t-pin in the rear again with a loop of string. Hang the front from the rafter and loop the rear over a rafter, pull on the rear string and check for side to side balance. One man operation.


Thanks again guys.

R

I have the CG as far forward as the plans allow. The plane is a gentle bird and very forgiving but as stated so many times, balance with an empty tank.

Ridered

Glad I could help


egor

i added right thrust even tho the instructions or the planes
didn't call for..or i coulnd find it.
i set up good so , it requied little or no trim
flew like it was on rails and required little or no elevators input
when inverted. same with a knife egde.

i bashed it a little tho.
diehedral out
clipped wings (total 3")
extended rudder.

i don't trim the elevators as the fuel gets empty.
so..the 12oz didn't effect it that much.
or i gotten comforatable with the plan that it didn't effect my flying.
eventually the CG was set back as far as the planes allow (empty)

i didn't add wieght to the tail of the plan when i moved
the CG back.
i relocated my battery pack or RX and kept it as close
to the fly able CG as much as possiable.

this way... there wouldn't be a drastic shift in the CG
as the fuel runs out if i was to simply add lead to the tail.

i'm not sure what the ratio is,,between wieght in front or back.
the cg is not at the haft piont of the fuselage..as we all know.