I'm to the point in the build of my lt-40 that its time to balance the plane. I've got the forward/aft balance to where its level when balanced on my fingertips at the back edge of the forward spar as called or on the plans (by adjusting radio/rx placement). My question is what is the best technique for lateral balance. I took a length of fishing line and tied it to the engine's crankshaft (without prop) and tied a large loop that went around the rear of the plane just forward of the tail feathers. when I lifted it up it it remained level. I wasn't this lucky to have it nicely balanced without doing anyting was I? I'm thinking that friction of the loop on the sides of the square fuse at the rear limited the planes ability to tilt to the heavy side. Do you think I have it balanced or is there another method I should use to check my lateral balance. Thanks.

For lateral balance I just check the main wing. I put the main wing on a length of 3/4" dowel and balance it.

I realize it is not as accurate as balancing the complete plane, however, I feel that the other parts of the plane are close enough to the C/L that they are going to make little (if any) NOTICEABLE difference in the flying of the plane.

Neddy,
Check out this post in my LT-40 build thread. [link]http://www.rcuniverse.com/forum/fb.asp?m=3822654[/link] . It's entirely possible that the plane is balanced laterally on the first try. In my experience planes will normally balanced laterally more often than not.

Ken

> For lateral balance I just check the main wing. <

I find that it is the weight of the muffler that must be counter-balanced on many models.

I agree with Dsegal, the only way to truly test the balance is with the wing attached to the plane. [8D]

I pick the plane up by the spinner, with the engine away fro the compression stroke, so it will rotate freely, then pick it up by tail, as near to the centerline of the fuse as I can. If I can't get the plane to hang in equilibrium from this point, I go a little higher with the aft pick-up point. Maybe up the rudder. When I get to a place were the plane will hang in equilibrium, then if one wing is down, I add weight to the opposite wing tip. If it looks like it will be a minor amount of weight, I use small nails or brads temporarily taped to the wing tip. I keep adding until I achieve a balance. When I know the amount of nails it will take, I drill holes in the tip and install the nails there with some CA. If it is a substantial amount, I may cut open a wing bay so I can glue in some lead sinkers or other lead weight.

You can also check some nearby garages or tire repair places. They change he balnce weights which are made of lead and just throw the old ones in a bucket. They come in different weights and I just cut off the longer pieces if I need less weight. I usually just put the plane so that it sits on the tail wheel on a table if it has one or the bottom of he fuse closest to the tail and then hold the plane by the spinner to see if it tilts to one side. I will also give the plane a slight push to the left and right if it doesn't tilt just to be sure that it self levels.

An easy way to check the plane is to take a real small screw eyelet and screw it into the center of the wing in the CG area and lift up the whole plane (minus any fuel). If it tips to the side you can add some self sticking wheel weights (like noted in the previous post) to the wing tip or where ever needed. You can get the small eyelets at craft stores. I used this technique on my U Stick and even left the eyelet in the wing. Works great.

LT 40.... Dont worry about it,,, just get the CG right and go fly.

Well,,,, thats really true but its a good habit to start now to get everything just right. You can
1. just check the wing which is the most practical for the afforementioned reasons
2. That will get you really close.

Mike,
Actually, on the LT-40 I built for the PIF thread it did turn out to be off enough on the lateral balance that I needed to deal with it. Something like 2/3 oz off if I remember correctly.

Ken

Wow,,, havent heard of one that far off... What drove the balance off so much? Variations in the wood in the wing?

It must have been that. I did notice that one of the aileron stocks were pretty soft when I put the kit together. I normally would have replaced the wood, but since I was doing the build thread on it I didn't want to start replacing wood as I built.

If you look at the link I posted above you can see how far out of balance it was

Ken

neddy sounds like it is balanced good enough,i have been lucky on several builds to have them balance like that.as long as your string is in the middle of the tale feathers you will get it as close as it can be and it will fly very true