SeamusG

dredhea - Only downside of your approach is that it takes a full cup of coffee to wait for the plumb bob and plane to stabilize. At this rate I'll definitely over-caffinate ,,,

I put a piece of 3M tape on the top of the wing (and missed center by 1/4") between the 3 1/2" and 4 1/4" CG range specified by SIG. The marks are at 1/8" intervals. I strung up the plane with SS wire around the spinner/hub and under the rudder's top CA hinge (padded & isolated using hi-strength fishing line). It took several minutes for both the plumb bob and the plane to stop swaying. Turned off the furnace to make sure that it didn't fire up at the wrong time.

Results: My initial CG is 1/4" in front of the CG range. The CG was moved back by 1/4" (plus a bit) with 3 1/4" of lead placed on the horizontal stab over the rearmost point on the fuse where I can attach the weight. A note, these lead bits do not have the adhesive backing. I'm thinking that dreahea's rule of thumb that 1/4 oz. is equivalent to 1/8" of CG is spot on!

pic 1 - just to visually confirm lateral balance
pic 2 - initial CG (Ithought it was at the front of the range by finger feel but I was off)
pic 3 - location with 3 1/4 oz bits on the stab
pic 4 - the bits

Time to move the battery pack back a bit.

Oh yea - it would have been nice to have the 1/8" markings centered - they were 1/4" to the left of center.

Hey, maybe I can replace that Higley Heavy Hub (2 1/2 oz) - lite is good.

dredhea

My Feedback: (13)

SeamusG - You got the procedure spot on and yes, there's plenty of time for consumption of beverages. Depending on the choice, that's not always a really good thing, LOL. Glad you have the balance issue worked out toyour liking. Now when you fly that masterpiece, if you feel that the CG needs to move further back, you'll know exactly how much weight to add to get it to move a certain distance. Happy Flying!

SeamusG

Now I have to balance a 4Star60, Hog Bipe, Kadet Senior and ShowTime 50 ... all are in need of a maiden flight. Guess I build more than I fly.

But - I know how to do it ...

Thanks for the help all

tailskid

My Feedback: (34)

Low winged planes are checked for balance UPSIDE down; High winged planes right side up! Pick them up (one at a time) and see where it balances, then compare where it SHOULD balance and add/move weight around to end up at the recommended spot. I like the GP balancer, but you can use your fingers

SeamusG

For those that doubt balancing a low wing with it's fin pointing up ....

pic 1 - updated my craddle - stout enough to hold a flying elephant
pic 2 - the dot marks the CG - I can't tell you whether the plane is balanced per SIGbecause I haven't added that detail. I will after Ipull it down.

dredhea

My Feedback: (13)

Actually, the CG will be the same whether the plane is upside down or rightside up. It's just easier to check a low wing by turning it over if you are supporting the weight by points on the wings. when using SeamusG's "cradle", it's immaterial. He could turn the plane over, but it isn't required. I like the balancer also. It's quicker and gives the same result, but the cradle is a lot more visual and tests lateral balance at the same time. It's really a preference thing. I found the cradle method because my balancer wasn't large enough to balance my GP Christen Eagle. That's one more advantage of this method; It works for any size of plane.

SeamusG

The only downside with the cradle and low wing planes is the problematic transfer of the CG range from (typically) the main spar to the top of the fuse. I did try to hang the low wing upside down in the cradle - not pretty - there is more wing mass above the axis between the crank and the tail attachment point (tailwheel assembly) - it wants to rotate around the axis to the upright position.

SeamusG

Well, I went to the 4Star60 plans and extended the CG range to the fuse top and the rest is history. My finger method resulted in placing the CG about 1/2" behind the "starting point" CG range. Now it's centered within the range. It takes 1/4 oz on the tail to move it back 1/8" and 1 oz on the firewall to move it forward 1/8". Time to go play.

This has been a very useful thread for me as it clearly helped me understand and how to establish the CG as a starting point for trimming my planes. Much better technique than using my fat fingers simply because I cannot "see" level when I'm holding the plane up. As dredhea explained it's an excellent visual display of the CG and, of course, essential for lateral balancing.

TTFN,

SeamusG

And here's a biplane (Hog Bipe)and mid-wing (ShowTime 50). The ShowTime balances in the middle of the canopy.

Everyone that have commented strongly suggest that the initial flights of the Hog Bipe be NOSEHEAVY. Well, I thought that I was good to go but this plane is balanced smack dab in the middle. Time to load up some lead at the firewall before I maiden her.