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Jan 31, 2020, 04:55 PM
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Tim Cullip's Avatar
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Here is what it now looks like after tissue covering. What's left is still the port boom radiators, spinners, painting, canopy and a few more bits of details (things like the turbochargers, etc.). Not sure how much of that list will happen before or after maiden (depends on how impatient I get).
The current AUW including battery is now 25.4gms.


Tim
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Jan 31, 2020, 05:50 PM
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MKellyvich's Avatar
That looks great Tim, and while 25g sounds heavy (from a free flight perspective) it's not bad at all with motors, battery and all the sheet work. I have a peanut Goodyear racer that flies well as a FF at 25g, but it's got a bit more wing area. Your P-38 will be a real head-turner once you've got spinners, canopy and markings on it. Good luck with the maiden!

Mike
Jan 31, 2020, 07:08 PM
Balsa Flies Better!
Hi Tim

OK- I do think your nuts as I have a 60" P-38 and it's not the easiest airplane to fly...but boy, your version looks very sweet!

One suggestion- make sure that you have lots of washout! Those skinny tips stall easily and it's going to be worse given that it's a peanut.

My last peanut was a PP P-51- still trimming it out. Came in at 11 grams- but that's rubber powered. I'm assuming your P-38 will have less area though- so yeah- it's not going to be a floater...

Sam
Feb 18, 2020, 06:40 PM
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Tim Cullip's Avatar
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Conclusion: Bad, Bad, Okay(?), Learning Experience


So it has been awhile since I posted, and here is my (most likely) final summary of this over-ambitious project.

1) Bad. I made a huge mistake that has no excuse. I ignored the importance of lateral CG. I ended up with one boom only having the motor and ESC, the other boom had the Rx, voltage booster, elevator servo, motor and ESC. If that wasn't bad enough I put the battery in the wing between the center pod and the already heavy boom. End result - the lateral CG was way off to the right of center. You'd think after building dozens of planes I wouldn't make such a rookie mistake, but apparently I'm quite capable of such a foolish move. When I realized my mistake I figured (hoped) that I could make up for it with a little left aileron trim (unfortunately, hoping doesn't make up for stupidity!).

2) Bad. One of my main goals was to have a great looking plane, so what do I do? Instead of checking how close Hunter Green is to Olive Green I just go ahead and use my rattle can Hunter Green on the top and hope (that stupid word again) it will be "close enough". Result - it was so far from close that I lost my motivation to finish the project before the maiden (see attached picture, maybe you won't be as disappointed as I was?).

3) Okay (well kind of, eventually, probably just putting an optimistic outlook on it)? Time for the maiden. I power it up and both motors are humming along just fine.
a) Give it a toss and it immediately rolls to the right (see 1) above) and spirals into the ground less than 10 feet in front of me.
b)Okay, time to give that hoped trim attempt - put in a huge amount of left aileron trim and try again. Give it a toss and it immediately rolls to the right and spirals into the ground less than 10 feet in front of me. So much for my hoped for "solution" to my stupidity.
c) Okay go back to the car and find a penny to tape to the left wing and try again. Hmm, no pennies in my car but here is a nickel, how bad can that be?
Tape it to the wing, give it a toss and it immediately rolls to the left and spirals into the ground less than 10 feet in front of me. You would have thought I'd be smart enough to put the nickel just far enough out to get a good lateral CG, but apparently I'm not that smart.
d) Okay, move the nickel so it is about half way out to the wing tip and try again. This time it launches straight and true and I get a mostly successful flight out of it.
e) Go home, remove the nickel, find a penny, measure CG and find the penny at the wingtip is too much so cut it down to 2/3rds of a penny (don't tell the feds I'm defacing US currency) and go back out and get a "decent" flight (I'm being a little generous here when I say decent).

Day two: Remove the penny, cut an access hole in the left wing for the battery, hack up the existing wiring so I can put the battery in its new location, cover the right wing access location and try again. And the plane flies reasonably well. It isn't the easiest thing to fly and I have to give it my full attention but it does fly. But after several aborted maiden attempts, and a couple of bad landings , and the surgery I've done it isn't looking good enough to finish beyond what you see in the picture.

4) Learning experience: So I chalk this project up to (at best) a learning experience, Unfortunately a couple of those "learned" lessons are ones I should have learned decades ago (be aware of lateral CG, don't guess that a paint color will be good enough without testing it first).

Now I'm contemplating doing it over again but at a slightly larger size (around 16" wingspan), but maybe I'll come to my senses before I go down that route?


Tim
Feb 18, 2020, 06:54 PM
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While the ugly green P-38 was sitting on my workbench taunting me I decided I needed to redeem myself so I decided to build a Peanut P-51C (Tuskegee red-tail version). In the several decades of building model airplanes I've never built a P-51 so I figured I do it now.

This isn't a build log (it only took me a week and after the P-38 I figured you folks have seen enough of my build logs for awhile) but I did want to at least report a success after the P-38 adventure.

It ended up at 18 grams with a 100 mah battery (19 grams with a 150) and uses a rewound Racerstar 0605C for power. It flies nice, has no problems doing loops, but rolls a little slow for my taste.


Tim
Feb 18, 2020, 11:33 PM
Registered User
Hey Tim,
Very nice job on your micro P-38 at that WS it is a challenge for sure.

I did a few scratch foam micro P-38's a 24"WS, 23" WS back in 2008/9 and around 2014 did a 20"WS profile P-38. They fly great still but were a hand full given the e-gear and batteries available at the time. They now look like they went through the war with plenty of crashes and repairs. I think I also did a micro one for my friend Speedy01 (Gene of RC Groups) but can't remember what size or if Gene still has it. So don't feel bad and you're right about balance all round. Do another one!

If you're a P-38 fan and have not already read Doorknob Five Two by Fredric Arnold I highly recommend it. In 2009 I corresponded with Fredric after reading his book I wanted to build a micro RC P-38 tribute to him. It came out real nice when new but was and is super fast with it had folding props, heavy brushless motors, ESC, and batteries. It chewed up a large fields fast and I had to land it with speed. Fredric gave me code and crew member names that were on the boom sides and tail of his P-38 as well as additional nose art he had. His story is amazing (though there are some controversies on it). The other book I got so I could do Jack Ilfrey's P-38 is Happy Jack's Go Buggy a great P-38 book as well. That P-38 build was lighter but I crashed it a few times before I realized that one of the heavy brushed motors was cutting out. I made the profile indoor flyer with newer light weight e-gear and it flies great indoors or out. So don't give up.

Pete
Feb 19, 2020, 03:34 AM
Go small or go home
ruzam's Avatar
Some projects need a practice round (or two) before they come together. What's that they say about kids and pancakes? The first one or two are...
Feb 19, 2020, 07:05 AM
Registered User
As a 3rd child, I agree.

Tim, don't give up on it, yet.
And show us pics of your hack job. We all suffer together.

mtflyr, nice planes. Why the folding props though?
Do they all have elevators?
Feb 19, 2020, 02:57 PM
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speedy01's Avatar
Quote:
Originally Posted by Tim Cullip
I figured you folks have seen enough of my build logs for awhile)
Tim,

You figured wrong -- definitely wrong. I admire your work, and
always look forward to your detailed builds.


Quote:
Originally Posted by Pete mtflyr
I think I also did a micro one for my friend Speedy01 (Gene of RC Groups) but can't remember what size or if Gene still has it.
It was ... er is a beautiful model that flies very well! Unfortunately I bashed the nose showing off, and haven't gotten around to repairing it. It's 21 1/2 wingspan with four channels. The rudders are linked and the elevator push rod is hidden in one of the booms, along with the brick. The battery is in the opposite boom, accessible via a hinged door. Markings are hand done, as are all the panel lines, and the pilot is hand cast by Pete. The turbo-superchargers are scratch-built works of art. Overall a really thoughtfully engineered and beautifully built treasure.


Name: Pete's Lightning (Copy).jpg
Views: 40
Size: 518.6 KB
Description: Mtflyr Pete's 21 1/2 inch scratch-built Lightning awaiting maintenance.

Gene K
Last edited by speedy01; Feb 19, 2020 at 03:04 PM.
Feb 19, 2020, 06:14 PM
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Tim Cullip's Avatar
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Quote:
Originally Posted by speedy01
It was ... er is a beautiful model that flies very well! Unfortunately I bashed the nose showing off, and haven't gotten around to repairing it. It's 21 1/2 wingspan with four channels
Gene K
Gene, did you use the rudders much (and were they linked in any way to the ailerons)? In the past I've built a few "big" P-38s (28", 36") and didn't use rudder, but I noticed this Peanut P-38's turns looked like they could have used some rudder along with the ailerons for better coordinated turns (or maybe a small amount of differential thrust to achieve the same thing).


PS: Thanks for the encouragement to keep posting build logs, I'll keep that in mind.


Tim
Feb 20, 2020, 08:06 AM
Registered User
J.A.H.

The folding props worked great with the big brushless motors t the time and the spinners that were part of the prop/s were perfect for that P-38 type. The folders also helped me land it hot since it is so fast.

Thanks for posting Gene. I forgot about that bird and was thinking of a different one I'd done.

Pete
Feb 20, 2020, 11:19 AM
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speedy01's Avatar
Quote:
Originally Posted by Tim Cullip
... did you use the rudders much (and were they linked in any way to the ailerons)?
Tim,

I didn't use rudders more/less than I normally do with scale models - mainly just to coordinate turns and adjust alignment on final. But playing around, I found them very effective. An excellent flyer all around.

Pete didn't build in any mechanical aileron/rudder linkage, and I don't normally use transmitter Aileron/Rudder Interconnect/Mix.

Here's a pic of the rudder linkage that Pete engineered:

Name: Rudder and Elevator Linkage.jpg
Views: 36
Size: 1.36 MB
Description:

Gene K


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