Lateral Balance of 4* 40  
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Lateral Balance of 4* 40 - 6/19/2008 6:08:19 AM   
Andrewmc


 

Posts: 119
Joined: 7/17/2004
From: Cape Town, , SOUTH AFRICA
Status: offline 		I have finished framing up a 4* 40 and have completed a 220 grit sanding.

I notice however that the right wing panel is heavier than the left hand panel. I initially thought that the panels had been made two different lengths (due to to surgery required on the plans for the left hand panel) but they are exactly the same.

I have modified the wing from the plans in that I have sheeted the leading edge back to the main spar and have placed one servo in each wing panel. I have also added solid balsa wingtips but the profiles of these are as identical as I can tell (traced each one on paper then folded over and looked at them against a window). Is this difference caused by the differences in wood densities and the amount of glue used per panel?

The wing tip blocks were from the same piece of wood so I would expect them to add the same amount of weight to each side.

When doing the lateral balance of the plane should I balance the wing independantly first and then balance with the fuse and engine? As luck would have it the heavy wing panel is the same as the side mounted engine cylinder .
       Post #: 1

RE: Lateral Balance of 4* 40 - 6/19/2008 7:54:32 AM   
mikenlapaz



Posts: 1951
Joined: 12/6/2002
From: La Paz BCS, MEXICO
Status: offline
quote:

When doing the lateral balance of the plane should I balance the wing independantly first and then balance with the fuse and engine?

Unless you will be flying the wing without the fuselage, I would just balance the finished product with a small piece of lead out in one of those solid wingtips.

_____________________________

''A government big enough to give you everything you want, is big enough to take away everything you have.'' Thomas Jefferso

(in reply to Andrewmc)
       Post #: 2

RE: Lateral Balance of 4* 40 - 6/19/2008 2:34:14 PM   
Clay Walters


 

Posts: 119
Joined: 1/5/2008
From: Simpsonville, SC, USA
Status: offline 		I agree with Mike, balance after finished and covered. However, because you anticipate the combination of the exhaust and heavy wing panel on same side; can you remove material from the heavy wing tip? (The further out on the wing the less you have to remove.)

Regards,

Clay

(in reply to mikenlapaz)
       Post #: 3

RE: Lateral Balance of 4* 40 - 6/19/2008 2:51:08 PM   
Andrewmc


 

Posts: 119
Joined: 7/17/2004
From: Cape Town, , SOUTH AFRICA
Status: offline 		It would be possible to remove material from the centre of the wingtip, but this would have to be done through the end wing rib also as everything is bonded together.

I do not think that this would be a problem though!

Would it?


(in reply to Clay Walters)
       Post #: 4

RE: Lateral Balance of 4* 40 - 6/19/2008 10:09:28 PM   
hrrcflyer


 

Posts: 494
Joined: 4/11/2006
From: Carrollton, VA, USA
Status: offline 		Andrewmc,

If you find it too difficult to remove wood from the heavy side, you can add a little weight to the light side. I've seen it done multiple ways. The easiest is to epoxy an appropriate piece of lead (the kind with the stick-on back) to the inside of the last rib. I've learded not to depend on the adhesive in the sticky part of the backing to hold the lead (don't ask me how.. ). If the wing tip is solid, you can also run a screw through the weight and into the wing tip block.

Good luck with finishing up and flying your plane!!!!

_____________________________

Fly safe and have fun!!
David

(in reply to Andrewmc)
       Post #: 5

RE: Lateral Balance of 4* 40 - 6/19/2008 10:57:39 PM   
dbacque


 

Posts: 383
Joined: 6/3/2005
From: Houston, TX, USA
Status: online 		Static balancing of the wing is a good start. But it's also important to fine tune the lateral balance through flight testing.

Trim the plane for solid hands off, wings level flight. Tweak it until you can make long straight passes without touching the ailerons. Then make a long straight pass but roll inverted at the start of the pass. Resist the urge to correct roll, just use some down elevator to keep it level and watch the wings. Does the wing stay level? If so, your plane is laterally balanced. Most likely it will tend to roll one way or the other when inverted due to a small lateral imbalance. If the plane rolls left when inverted, then the right wing is heavy. So if it rolls left inverted, add a little weight to the left wing tip. I use stick on lead on the bottom of the wing tip. Then retest. Continue until aileron trim is accurate for both upright and inverted flight.

But do balance it before you cover the wing so you can hide most of the weights inside the wing. Then you'll only have a few chips of lead exposed for the final tweaks.

Dave

(in reply to hrrcflyer)
       Post #: 6

RE: Lateral Balance of 4* 40 - 6/20/2008 12:43:28 AM   
mikenlapaz



Posts: 1951
Joined: 12/6/2002
From: La Paz BCS, MEXICO
Status: offline 		How about drilling, with some tubing, a couple of holes in the wingtip of the light wing. Say 1/4" or larger, cover the wing as normal and when, if , the time comes to add weight just open the covering over the hole(s) and slip in some fishing pencil lead. and put a small circle patch to cover. The solid tips give you all types of hidden mount locations.

I put some split shot on a fishing line and ran it in the 'flutes' of some SPAD coroplast wings for static balancing.

_____________________________

''A government big enough to give you everything you want, is big enough to take away everything you have.'' Thomas Jefferso

(in reply to dbacque)
       Post #: 7

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