Weight and Balance question

[Bob Wood]

I flew my XL Monday night for the first time. Felt great by the way!!

Per Leonard and Tom H and some others I was going for 25% chord CG as a start. (with 28-30% in mind as maybe a better place to be)
My actual is 25.4% ( full fuel & pilot ready to fly)
I was playing around with the numbers and moved my 6# battery t the tail and got 28.6%
I would probably beef up my light aluminum tail spring & caster before running wires and battey to the rear, but question is the same:.

When making a move like 6# from front to rear, is the result a better trim situation, like maybe to get to a hands off stick situation?  In other words after I get some stick time and figure out if it wants to climb or desend hands off. do you play with CG before trim tabs etc?

Just wondered what your guys have found when tweaking the CG.....

Thanks,
Bob Wood

[Sam Buchanan]

If it "felt great" at 25% why would you want to make changes?

And...congratulations on your first flight!

[Tom H]

Bob, from my experience with our LEU and DE, 25% is NOT a good flying CG.  It will take off and fly, but, when landing, with the relatively forward CG, and the power going to idle, at lower speed, the airplane will not flare well.  If you have the flying CG in the 25% range, you may need to maintain a higher landing speed and/or keep some power on for the airplane to flare well.

I suggest the flying CG to be around 28 - 30% back of the wing leading edge.  With me flying, our DE is at about 29% and lands well, good flare, good control.  An leisurely attempt at power-off stall almost gives a break, but mostly mushes.  A more aggressive and quick pull back on the stick will sometimes produce a break, but still mushes.  I believe a bit more aft CG would provide a more definite break.  But, at the current CG, it flies well, no real complaints.

Some suggest going a bit more than 30%, but I have not tried it, yet.

Another adjustment that comes into play is the horiz. stabilizer angle of incidence.  We have moved the leading edge of the DE horiz stab as low as possible against the fuselage, which may be an indicator that more aft CG could help.  The DE has elevator trim adjust, and, right now, it flies almost hands off at neutral trim, which, I think, is about right.  So, we are close to the best CG for our DE.

You are doing the right tests, and you will get a feel for what is right for your airplane.  Test it at 28.6% and note if the landing flare is better for you.

Good luck, have fun.

Congrats on your first flight.

[MrG]

Tom b4 you dropped the nose of the Horizontal  did it take a fair bit of back pressure to keep it level flight- i have same issue with it set as drawings 
so i am guessing you dropped the nose about an inch at least ? other than that no issues

[Tom H]

Mr G, on the DE, as best as I can remember, it may not have flown hands off, even with trim added in, with the stab LE in original position.  But, with stab LE fully down, it can be trimmed to fly hands off.  Last fall, I flew to our fly-in, and had a perfect calm day, and took a video with hands off.  It flew for maybe a minute hands off, which I think is quite a feat.
I don't know how much I moved the stab LE down, but it is as far as it will go.  We were thinking of moving the horiz spar up a bit, but that entails changing the brace wires, and have not done it, yet.  On final approach, idle power, we can not trim it to descend at proper airspeed without add'l back pressure on the stick.  We think a bit more horiz stab adjustment may help.  Or, as I have previously discussed, a bit more aft CG.  But, we don't have any easy way to do that without adding more weight.  Thought of adding a heavier tailwheel, but don't want the weight.

[MrG]

Thats pretty much what im aiming for, Thanks

[rfeenstra]

I built my DE with -2 degrees built into the stab.  My CG is now right around 30%. Seems to be about right.  At 25%, it was nose heavy and needed engine to flare.

[MrG]

Awesome info - i just spoke to Bubba as well 
im heading in correct direction

[ParQld]

Hey @rfeenstra, is your DE hand propped or do you have a starter ?

chers Pul

[rfeenstra]

Hand propped. Continental A-65.