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Old Mar 12, 2013, 10:19 PM
Tye
Chacotoma, NM
Joined Jan 2004
715 Posts
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Balancing a Bomber ?

I just finished a 440 sq in Jim O'Reilly Lanzo Bomber. Powering it with a Hacker A-20 outrunner, and a 1050 mah LiPo, and it came out tail heavy. If I lengthen the nose, and put the battery and motor control directly behind the motor, it's gonna take about 6" to make it balance. Is this very extreme, and are there any alternatives ? ? ?

zak
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Old Mar 12, 2013, 11:08 PM
AMA7224 LSF1832
Leadchucker's Avatar
Joined Sep 2008
3,470 Posts
Where on the wing you trying to balance it? Bombers and many other old timers balance well aft of 'normal' airpllanes. You want to try to start at about 50% of the chord and it might even go to 60-65% to get a nice glide.
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Old Mar 13, 2013, 12:29 AM
Tye
Chacotoma, NM
Joined Jan 2004
715 Posts
Balancing it at 4.31" per the plans, it seems be about 50%, will check closer tomorrow. Isn't 60 - 65 % dangerous ? ? ?
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Old Mar 13, 2013, 02:11 AM
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United States, CA, Santa Ana
Joined Jul 2010
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Start at 50%. I have built 48", 60", 66", 80", and 96", most came in right close to 50%.

Ross
Gas & electric
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Old Mar 13, 2013, 03:48 AM
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brokenenglish's Avatar
France, Centre, Amboise
Joined Nov 2011
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Just a remark...
Electric flyers seem to have invented this principle of nose lengthening but, for decades, we've always just added ballast in the nose to balance.
It's so important to recognise this potential situation before you start building, and take the necessary action (light wood on the unstressed parts, light covering material, single-side elevator, light control linkages and make your own little control horns instead of the standard RC accessories, which are far too heavy at the extreme rear end, just use Z-bends at the rear and keep all the control adjustments at the front end)...
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Old Mar 13, 2013, 04:05 AM
I like real wooden aeroplanes!
Sundancer's Avatar
South-west France
Joined Sep 2007
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Quote:
Originally Posted by brokenenglish View Post
Just a remark...
Electric flyers seem to have invented this principle of nose lengthening but, for decades, we've always just added ballast in the nose to balance.
It's so important to recognise this potential situation before you start building, and take the necessary action (light wood on the unstressed parts, light covering material, single-side elevator, light control linkages and make your own little control horns instead of the standard RC accessories, which are far too heavy at the extreme rear end, just use Z-bends at the rear and keep all the control adjustments at the front end)...
Fair comment Brian, and keeping the back end (and the wing tips) as light as possible is always good practice. However, with some of the early power models especially those designed for ignition engines, it is sometimes just impossible when fitting the design with the appropriate - and MUCH lighter - electric motor to get the CG far enough forward, as there just is no space in the nose to get the battery pack - which usually represents the majority of the power system weight - far enough forward to achieve the correct CG without adding nose weight.

Because any model designed FROM THE OUTSET for electric power should NEVER need nose ballast, due to the ability to position the heavy battery pack to suit, electric fliers HATE adding lead; this probably dates back twenty years to the days of relatively low powered and heavy brushed motors where keeping the overall weight down as much as possible was the only way to get really good performance. It isn't so important now with current power systems, but the memory lingers and I know that I hate having to add ballast to the nose.

Some short nose models can solve the problem by ingenious battery pack placement - e.g. my Spartan below has a deep enough fuselage to mount a heavy (2200 3S) battery pack right forward oriented vertically and thus get the CG right, but on many vintage models with slimmer fuselages it isn't possible. Personally rather than lengthen the nose of a vintage design, I would either build a more suitable model, slightly alter the nose profile to get the battery in under the motor or grit my teeth and add the lead, but it is a matter of personal choice I guess.
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Old Mar 15, 2013, 11:10 AM
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Rhea's Avatar
United States, MN, Eden Prairie
Joined Oct 2008
964 Posts
Here is my 80 Bomber. It balances at around 50%, maybe even a little farther back than that. To get it there I used a big and heavy Power 46 motor, extended the motor mount, added about 6 oz of weight as far forward as possible and a Harry Higley Heavy Hub on the prop shaft. It flies great. It can handle a fair amount of nose weight but the CG can be back a ways because of the lifting tail.
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