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Old Apr 14, 2001, 09:57 AM
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jbrundt's Avatar
O'Fallon, MO, USA
Joined Jan 2001
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P-38 construction update.....

I added a page to my web site on the progress so far on my JR Models P38 from Hobby Lobby. You can check it out here:
http://www.geocities.com/jbrundt/p38.html

Any suggestions are welcome......
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Old Apr 16, 2001, 01:21 PM
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GregG's Avatar
Antioch,CA,USA
Joined Dec 1999
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Great plane, I like your webpage! The only thing I would change is go with a set of zapped 2000 Nimh cells. They are the same size and weight as your 1250's. At ~18 oz/sq ft wing loading it should be a pussycat to handlaunch. This will be a real attention getter at the field, it seems everyone likes the P-38. If you feel the need for more speed, add another cell or two!
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Old Apr 16, 2001, 07:15 PM
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Doc Watson's Avatar
UK
Joined Mar 2000
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Nice plane and great site!

Do you think that converting the Combat models F16 to EDF would be hard? It sure looks a nice model, get an 'inline' EDF in there and more than a few 2400mAh's and it would burn......

How difficult would it be to hot wire the internals?

Doc
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Old Apr 17, 2001, 08:24 AM
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O'Fallon, MO, USA
Joined Jan 2001
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Quote:
Originally posted by Doc Watson:
Nice plane and great site!

Do you think that converting the Combat models F16 to EDF would be hard? It sure looks a nice model, get an 'inline' EDF in there and more than a few 2400mAh's and it would burn......

How difficult would it be to hot wire the internals?

Doc

Thanks for the nice comments on my site.

Doc.....

The F16 would be a great conversion to e-power. The ducting runs the full length so you could put a fan unit in there. Finding room for batteries would be a challenge though. There is space where the (2) 6oz sullivan fuel tanks go for the IC motor that you could use. You could fit 24 cells in that area. The foam is regular white beaded styro so hot wiring it is not a problem.

The AUW for my IC F-16 was right around 7.5 lbs. She certainly looks good on a low level strafing run
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Old Apr 17, 2001, 09:59 AM
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Portland, Oregon
Joined Jan 2001
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I really like my JR P-38! I simply covered the wood with white Econocote and trimed it to look like Lefty Gardner's "White Lightning".
Be a little careful on the hand launch though. My first 2 launches were wimpy because of a shoulder problem. The P-38 mushed into the ground with no damage. Later, a friend (KeithWatson) launched it. A few steps and a pretty good throw got it going.
It is so cool making strafing runs, victory rolls, big loops and I could go on forever about my P-38!
You're gonna love it! But you already knew that, didn't you.
Best Regards,
Charley
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Old Apr 17, 2001, 10:09 AM
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O'Fallon, MO, USA
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Quote:
Originally posted by CharleyRexom:
I really like my JR P-38! I simply covered the wood with white Econocote and trimed it to look like Lefty Gardner's "White Lightning".
Be a little careful on the hand launch though. My first 2 launches were wimpy because of a shoulder problem. The P-38 mushed into the ground with no damage. Later, a friend (KeithWatson) launched it. A few steps and a pretty good throw got it going.
It is so cool making strafing runs, victory rolls, big loops and I could go on forever about my P-38!
You're gonna love it! But you already knew that, didn't you.
Best Regards,
Charley
Charley,

I already just love looking at the almost completed model. It really is a beautiful airplane. I made provisions for a hook just foward of the CG for bungee launching. I think this will be the preferred method, at least for the initial flights.

What battery did you use in your P-38 and what was the flying weight?

Thanks again for the words of encouragement. I have not heard from many people that have flown this particular model.

Jeff

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Old Apr 19, 2001, 10:12 AM
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Cincinnati, OH USA
Joined Oct 2000
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Jeff, one piece of advice on the JR Modell P-38: I regularly hand launch my friend Paul Siegel's version (2 X AFI BL020 with planetary gearboxes and scale 3-blade props!). It's a little hard to grip because of the big scale fillets on the bottom of the pod. I suggest gluing a pair of small oval shaped 240 wet-dry sandpaper patches there for a grip.

Jim
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Old Apr 19, 2001, 10:37 AM
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O'Fallon, MO, USA
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Quote:
Originally posted by Jim Ryan:
Jeff, one piece of advice on the JR Modell P-38: I regularly hand launch my friend Paul Siegel's version (2 X AFI BL020 with planetary gearboxes and scale 3-blade props!). It's a little hard to grip because of the big scale fillets on the bottom of the pod. I suggest gluing a pair of small oval shaped 240 wet-dry sandpaper patches there for a grip.

Jim
Hi Jim,

I think I am going to bungee launch this one. I installed a tow hook mount just forward of the wing LE on the belly of the main pod. I have plans for the bungee launcher that was in S&E Modeler from Aug/Sep '99. I also ordered the 1250SCR pack from New Creations R/C (Kirk was very helpful and nice to talk to). With this pack I save about 4oz of weight and only lose maybe a minute of flight time. It should be done in time for the St Gen E-fly.

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Old Apr 22, 2001, 02:38 PM
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The P-38 is painted and electronics installed. I did a test run of the motors. It looks sweet with Tornado 3-bladed 6x3 props. Unfortunately the JETI 350 ESC cuts out with those installed when at full throttle I guess it is drawing too much current and cutting out (a safety feature of the ESC)

I put on a set of graupner 6x4 two bladed ones and it works fine.

Just held in my hand at full throttle it wanted to leap out and fly. I am very impressed with the power it's putting out. Everything's on track for a first flight at the St Gen. E-fly next weekend. AUW is 44oz so going with thw 1250SCR pack really did help.
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Old May 02, 2001, 04:29 PM
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Lilburn, GA, USA
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So... how'd it fly?
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Old May 02, 2001, 07:15 PM
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O'Fallon, MO, USA
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Quote:
Originally posted by rcflyer11:
So... how'd it fly?
The weather was perfect this past Saturday at St Gen. I bungee launched the P-38 for its first flight. A nice gentleman at the meet did the honors and the P-38 took off like a homesick angel. A little down trim was all that was needed and she was flying beautifully. I did several circuits then got brave and did a roll. it was a little slow but very scale. Loops were next. Big and round with a little speed bled off at the top. This plane flies very nice!

Then tragedy struck. I decided it was time to land so I set up for the downwind turn when the motors quit. I figured the BEC had cut in so initially I wasn't worried but what happened next just stunned me. The plane spun in. I had zero control!!!!

It impacted the ground nose first. I didn't see a lot of parts fly off so I thought it might be OK. Well when I got there it was pretty bad. The wing joiner tubes were bent, the pod was pretty crunched and there were numerous cracks in the fiberglass section. I was at a loss to explain what happened. The motors shutting off should not have caused it to spin like it did.

POST MORTEM:

I beleive I know what the cause was: the JETI 350 ESC!!! When I had run the motors on the bench the same thing happened. The cut-off would engage and all power was lost. If I moved the throttle lever back to idle then slowly advanced it then I would have power to everything. I should have thought more about this at the time but I shrugged it off to running the motors on the bench and not in the air. Prior to this JETI I had only used the Great Planes ESC's and NEVER had this trouble. I had wanted to put the GP 30A ESC in and now I realize I should have. The JETI was not overheating or drawing too much current.In fact it's the ESC Hobby Lobby reccomends. In short it's the last JETI I will ever buy. I do not trust them!

The P-38 can be repaired, though it will be involved. I have to completely replace the CF spar tube. The goal will be to keep the repairs as light as possible. I now know that this is a good flying plane. At least I was able to get a good flight out of it before disaster. Hopefully she'll fly again. However, it was an expensive lesson to learn.

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Old May 02, 2001, 10:06 PM
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United States, MI, Roseville
Joined Dec 2000
8,884 Posts
Sorry to hear she went in like that. I lost my prototype Me 262 that way, overloaded an esc (FMA MINI 20) by using two Max 480 motors from Dymond, and 8 cells with 5/3 cox pusher props.Difference is, mine had never cut out running it on the bench.
Expensive lesson: If theres trouble, don't be too eager to fly, or even chance it, theres too much work involved in building or rebuilding to do it.
I wonder if the ESC got too hot in fuselage.Was it near the cells? What AMPS DOES two motors like you were runnning on those props pull? Invest in a whatt meter,it can really save you money.

Good luck getting her back in the air, I bet it looked really great .


Mark
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Old May 03, 2001, 01:26 AM
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Portland, Oregon
Joined Jan 2001
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Jeff
What an absolute bummer! I actually felt a little sick when I read that it spun in. (been there, done that)
If you need a "repair section" let me know and I'll lift a mould from the area you need. It may be easier and lighter than reassembling a bunch of small pieces.

Charley
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Old May 03, 2001, 05:53 AM
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Antioch,CA,USA
Joined Dec 1999
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That really bites, I feel for ya. This is one of the threads I've been keeping an eye on as I want to do one myself someday. How was the top speed, were you able to back off the throttle any? On the slow aileron responce, did they need a bit more travel? I just love the way the P-38 looks. Good luck on the rebuild and let us know when you fly it again.
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Old May 03, 2001, 05:56 AM
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Lilburn, GA, USA
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Sorry to hear about your misfortune. Plane looks gorgeous on your website. Good luck with the repairs.
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