Hi there,

I bought this plane and installed a 64mm EDF unit and all the electronics. Unfortunately the manual doesn't give a center of gravity. I read on another forum that the composite version of the same plane has it listed at about 5.5 inches from the front of the intank. If place the battery in the bay, my COG is about inch behind that, making her tail heavy. If place the battery in the front of the plane's nose section it evens it out almost right on. My question is does anyone know the true COG for the foam version? I don't have very good luck guessing and really don't want to take a chance on this.

Thanks!
Dan

Originally Posted by dtil817

Hi there,

I bought this plane and installed a 64mm EDF unit and all the electronics. Unfortunately the manual doesn't give a center of gravity. I read on another forum that the composite version of the same plane has it listed at about 5.5 inches from the front of the intank. If place the battery in the bay, my COG is about inch behind that, making her tail heavy. If place the battery in the front of the plane's nose section it evens it out almost right on. My question is does anyone know the true COG for the foam version? I don't have very good luck guessing and really don't want to take a chance on this.

Thanks!
Dan

I set the CG on my foamy the same as the composite and it was perfect. Mine is at 145mm from the intake. Both the composite and the foam T-45 are the same dimensions so use the same CG range. The composite instructions state 140 to 145mm is good. Some of us with the composites even went to 150mm.

Hi -- Are you sure about the 140 145 mm location? I read another post where it was recommended behind the dorsal airscoops, which is about 170mm from the intake. Thanks.

-David

Hi guys,
If you flew competition sailplanes you might understand the title.

Lets start with some common sense. The only reason to have weight in the nose of a model, is to make it fall forward. If they fell backwards, we'd have trouble since we don't practice flying airplanes that way, for the most part they all go forward.

Now if you have one more dot of weight than is needed to make the model fall forward, it will then fall forward and nose down. To keep the model in level flight it will then be necessary to either build the model crooked (some up incidence in the stab) or fly with some up elevator all the time.

Either one makes a pretty crappy flying model....well that is if you know the difference. A guy who's first and only auto always pulled hard to the left. When he tried to drive all our cars, he couldn't...saying that they didn't 'feel' right to him.

At this point your head is rushing to thoughts about snap rolling, tip stalls and twitchy or touchy. You'll be coming up with the old yarns about tucking and instability blah blah blah, etc. If those thoughts have passed, read on.

Oops you likely now slipped in to thinking about phrases like reward CGs, or the term CG in general....okay if that has passed read on. Because it has little or nothing to do with having a model balanced for flight. You see CG is something you measure, airplanes are dynamic, they fly, they need airspeed in order for their surfaces to react. Last I checked, a model teetering on some pegs on a bench has neither airspeed or ground speed...but it does give you a chance to exercise the spring in your tape measure and a good feeling that you have obediently followed directions.

Oh heck I forgot the other thing you're likely thinking about at this point "the designer/builder/manufacturer must know best when it comes to CG!!!...yawn.

Builders are not necessarily flyers, and many flyers don't understand the difference between balancing a model to fly and measuring CG.

Gliders don't have motors to tug them around the sky. Would anyone of you reading this think that it would be good to have a glider flying around with up trim all the time and more lead in the nose than was absolutely needed? Crazy I know but its done all the time.,

Okay, here's something you all need to chant each morning while shaving, until you understand it....then you won't need anyone to tell you how to balance your models. "Airspeed empowers tail feathers" Do it three times each morning...till you get what it means.

If you give your model up elevator while it is teetering on that latest gizmo for setting CG with in micro nano meters, will the nose pitch up? To avoid anyone embarrassing themselves by answering yes, the answer is no. Without air moving across and against the up elevator, nothing happens. The lack of air is not deflected upwards and the tail is not pushed downwards.

Airspeed empowers tail feathers and its the tail feathers that direct the nose of any kind of airplane.

If you have that extra dot of weight in the nose of your model, in order for it to fly level it will need to have MORE airspeed than if the weight was correct and the elevator was neutral. We have a saying in sailplanes, "don't try to catch a nose heavy sailplane, because it will knock you on your a__". (yes we do catch our 147" sailplanes, all the time, easier than walking for them).

So again, if you have a dot more weight in the nose of your airplane than is needed to make it fall forward, it will fall forward and nose down, unless you have some up trim to stop the nose from falling, and enough airspeed for that up trim to keep the elevator powered to do that work.

Its way the T45 noses up with throttle and drops its nose like a speedy rock when it slows. Simply pull the model up into a stall and see if the nose doesn't drop like a stone!

And that's what the T45 does if the battery is in its place. Wayyy nose heavy.

So in order for the elevator to move the nose up it needs a lot of throw upwards, partially because its made of foam and the foam bends under the load of all that extra nose weight...especially pulling out of a dive.

I just glued mine together but I flew one at Jets Over Kentucky and one on our field...both very nose heavy. Not balanced for proper flight.

I'll get mine balanced then measure the teeter totter point for you guys, but likely the 170mm is going to be correct.

Without extra weight to force around, you can then get to use that function you paid for....dual rates and travel adjust, you see you won't need as much control movements in order to make the nose go where you want.

Gordy Stahl
Louisville Kentucky

Originally Posted by dtil817

Hi there,

I bought this plane and installed a 64mm EDF unit and all the electronics. Unfortunately the manual doesn't give a center of gravity. I read on another forum that the composite version of the same plane has it listed at about 5.5 inches from the front of the intank. If place the battery in the bay, my COG is about inch behind that, making her tail heavy. If place the battery in the front of the plane's nose section it evens it out almost right on. My question is does anyone know the true COG for the foam version? I don't have very good luck guessing and really don't want to take a chance on this.

Thanks!
Dan

Hi Dan;
It appears the CG is about 150MM from the air intake. What about control surface throws?

Sal

Hi Dan;
It appears the CG is about 150MM from the air intake. What about control surface throws?

Sal

I have a T45 and need information on the control surface settings and confirmation of the CG location. I read on one of the blog threads that it is about 150mm or 15 cm. I am anxious to fly my new T45 but I do need this information.

Someone please help me,
Sal