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Sep 21, 2019, 08:34 AM
Registered User
Quote:
Originally Posted by MNWarbirder
Couple more...
Great stuff Chris!
Sep 21, 2019, 09:14 AM
Bomber Bob
borntoolate's Avatar
Great pics!

Bob
Latest blog entry: The XB-38 s/n 41-2401
Sep 21, 2019, 07:23 PM
So many planes, so little time
USMA82's Avatar
Went to see the Collings Foundation planes in Worcester today. Along with the B-17, B-24, and B-25 I've seen in the past, there was a P-40, Spitfire, Hellcat, Skyraider, P-51 and.... a P-38! First one I've seen up close. And guess what the livery was!
Sep 21, 2019, 11:42 PM
Registered User
Pavel Pankratov's Avatar
Intrigue!
Sep 22, 2019, 02:22 PM
MNWarbirder
MNWarbirder's Avatar
Nice! I think I'm going to try adjusting the angle of the nose gear - it's supposed to be more canted forward.
Sep 22, 2019, 08:25 PM
Registered User
May I please ask for help balancing the plane?

I went - for a start -with 2x Zippy 3300 (350g each), gear down. Now, studying this thread I have noticed 2 ways of measuring the CG: Option 1 - on the bottom facing side of the wing, where 70mm is on the leading edge of the wire covering and Option 2 - like in the manual - on the top facing part of the wing, where it puts it on the front part of the round panel (fuel tank cap?)

So when I measure Option 1, plane top side up, it is way tail heavy, I cannot move my batteries forward enough to balance (need heavier batteries?). When I measure Option 2 (plane upside down) it is way nose heavy, I cannot move my batteries back enough to balance (need lighter batteries)?

Thanks
Sep 24, 2019, 05:28 PM
MNWarbirder
MNWarbirder's Avatar
Have had plenty of joyous flights with mine running 2 Admiral 300mAh 4S batteries (306g / 10.79oz each) about as far forward as possible and yet still able to close the hatch - this equates to a positioning of the leading edge of the batteries about 1 1/2 "holes" back from the very front of the bay. I've also run a single 5000mAh 4S battery (sorry not sure of the weight) and had no issues - a click or two of elevator is all that was needed once in flight.

It was a few years ago, so I'm somewhat foggy on the details now, but I did set the elevator "up" in accordance with the manual and don't recall having any problems with balance on the first flight, or for that matter, anytime thereafter.

The key issues for me with this plane were to hook up in parallel (whether single or double batteries) to ensure equal power to the engines, and to use a voltage alarm to ensure no unpleasant surprises in midair regardless. Distant second point was to replace the stock LG with the strut upgrade kit, as this is pretty heavy for a foamie and its benefits from having some shock absorption. Good luck!
Sep 24, 2019, 05:38 PM
Registered User
Quote:
Originally Posted by MNWarbirder
Have had plenty of joyous flights with mine running 2 Admiral 300mAh 4S batteries (306g / 10.79oz each) about as far forward as possible and yet still able to close the hatch - this equates to a positioning of the leading edge of the batteries about 1 1/2 "holes" back from the very front of the bay. I've also run a single 5000mAh 4S battery (sorry not sure of the weight) and had no issues - a click or two of elevator is all that was needed once in flight.

It was a few years ago, so I'm somewhat foggy on the details now, but I did set the elevator "up" in accordance with the manual and don't recall having any problems with balance on the first flight, or for that matter, anytime thereafter.

The key issues for me with this plane were to hook up in parallel (whether single or double batteries) to ensure equal power to the engines, and to use a voltage alarm to ensure no unpleasant surprises in midair regardless. Distant second point was to replace the stock LG with the strut upgrade kit, as this is pretty heavy for a foamie and its benefits from having some shock absorption. Good luck!
Thanks a lot. After checking this thread again I understand that the leading enge of the wire cover may be too nose heavy (as it is way forward comparing to the 70mm mark on the top of the wing) , so it is more towards the trailing edge of the wire cover if I want to balance the right side up. I have 2 3000mAh 4S that weight similar to yours so will use your position as a reference.

I have upgraded the struts and set the elevator to be 4mm up as per the manual.

Thank you.
Sep 24, 2019, 06:43 PM
Registered User
Just to add a note to this CG discussion: CG point does not vary whether the plane is inverted or not. In some cases it is easier to "balance" the plane in one position or the other depending on whether the majority of the weight of the plane is above or below the center line. More sensitive if the weight is above the center line, less if it is below. This doesn't effect the CG just makes the balancing sensitive or less sensitive. In the case of this aircraft there is little difference in weight distribution, being mid wing, so the choice is not significant.

So, that brings us to the actual CG being sited at 40 mm on one side of the wing and 70 mm on the other. That is impossible! CG projects through the wing and is the same whether balanced on the top or bottom.

All things being equal, we are closer to 70 mm than 40 mm on the P-38. I've flown mine 249 times balanced like this.
Sep 24, 2019, 06:45 PM
retired ATC
ron1950's Avatar
is the 4mm up on the elevator as in the directions correct? iam about to maiden mine but haven't yet...so if its correct and 4mm up is correct the flaps at 1.5mm down and 3mm down at would still make the elevator be in the up position...
Sep 24, 2019, 07:07 PM
Registered User
Quote:
Originally Posted by ron1950
is the 4mm up on the elevator as in the directions correct? iam about to maiden mine but haven't yet...so if its correct and 4mm up is correct the flaps at 1.5mm down and 3mm down at would still make the elevator be in the up position...
4 mm, up, is a good starting point. Most pilots find that gives level flight at 75% throttle with a slight climb @ WOT. The down 1.5 mm and 3 mm elevator positions, per flap 15 and 30 degrees, deflection are also good. Remember, the plane thinks the 4 mm up elevator is neutral, even though it is trimmed up, and the additional down mixing is just compensating for the flaps.

Good luck with the maiden!
Sep 24, 2019, 07:57 PM
retired ATC
ron1950's Avatar
Thanks 19000. And thanks to alex for mentioning the 4 mm up. I missed that in the instructions completly
Sep 25, 2019, 08:19 AM
Registered User
ncflyer79's Avatar
Just ordered this bird yesterday and decided to go with 1 4s 5000mAh pack. Using the battery from the link below, do you guys think the CG will be ok?

https://www.amazon.com/HRB-Battery-C...gateway&sr=8-1
Sep 25, 2019, 08:54 AM
Registered User
Quote:
Originally Posted by ncflyer79
Just ordered this bird yesterday and decided to go with 1 4s 5000mAh pack. Using the battery from the link below, do you guys think the CG will be ok?

https://www.amazon.com/HRB-Battery-C...gateway&sr=8-1
One of the batteries I use in the P-38 is the one in your link. Nice battery for the money. No problem with CG.


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