bfd04

Hello All,

I picked up a World Models P-40 Warhawk this weekend, and I am having an issue with the balance. The instructions say the CG is at 93mm from the wing LE. With the cowl on and flight ready(all electronics, empty tank, and retracts up) I need to add almost 6oz tail weight to get it to balance. Is this normal? If I remove the canopy and leave everything else the same, It only takes .25oz in the nose to get her balanced. I have moved the reciever and batt but it does not make a huge difference. Has anyone had a similar problem?

Fuse length 52" from tip of spinner to tail
W/S 59" tip to tip
OS .46LA

Could it be possible the CG in the instructions could be a misprint? Lateral balance is fine only took a few grams to make it perfect.

As always any help is appreciated.

John

da Rock

Hello
After rereading your description a couple of times something still doesn't sound right.

You say that with the canopy on, the plane needs tail weight, and with it off the plane needs nose weight. Right?

The canopy is behind the cg. It's removal ought to cause the plane to be nose heavy. Do you mean that you removed the cowl instead of the canopy?

da Rock

If removal of the cowling "balances" against 6 ounces of tail weight, then that would suggest that the cowl is about 2-3 ounces. I usually use 800mAh RX batteries in my 46 size models. They usually weigh 4 ounces. My 1100mAh batteries weigh about 5 ounces.

My cowling's CG is about 8" ahead of the airplane's cg. (It's actually right at the firewall.) If I were to place an extra 3 ounces in the fuselage about 8" behind the cg, I'd still be inside the equipment area. Have you weighed your cowl? If it's only 2-3 ounces (which sounds a bit light) it ought to be easy to match that by moving the battery.

With my 46 size P40 the battery can be about 4 inches ahead of the CG and that's where it looks easiest to place. I can also place it easily all the way back to 6 inches behind the cg and not need to do any real bulkhead building. I can easily build a box into the opening in the fuselage to solidly hold either battery about 8 inches back.

You might look just a bit harder at moving your battery back. Changing the location of 4 ounces front to back the same measurement actually ought to give more than just adding 6 ounces of tail weight. If it's already back some, moving it into the tail just under where the wing bolts hold the TE down, really ought to significantly reduce any more tail weight that might be needed.

And building a battery hold down structure in the back of the fuselage is going to put some weight back there as well.
And using a larger battery will also give you some extra, yet useful, balancing weight.

da Rock

My KYOSHO 46 size P40 is just about the same size as your WM P40.

The P40 wing has very little sweep in the LE. That's one reason the suggested CG sounds "too far forward". It actually will be.

And my KYOSHO instructions give a 95-105mm range for it's CG. So WM's suggestion sounds about right.

da Rock

That airplane is like all low wing models, it's very tricky to try and balance upright. Turn it upside down and it's easy to get a very accurate balance.

LDM

My Feedback: (15)

ON the P40 , make sure your gear is retracted and balance upside down .

ronsky1

So how does a World Models P-40 fly?? A friend wants to sell me his with a YS91 engine, pneu gear and servos for $400. Is this a fir deal?? Has 11 flights with no problems.

Ron