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Old Apr 28, 2011, 08:28 AM
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Build Log
Top Flite P-39 build

I'm about the same place as Chrisdev01 was at the end of page 6 of his build so I'll start there. If you want to see the beginning stages go here

http://www.rcgroups.com/forums/showthread.php?t=1357938

Rather than the Robart retracts I'm using the E-Flite electric retracts.

Getting the electric retracts in the wing was a breeze, the nose gear however was a little more difficult. I thought I would use the E-Flite 60-120 electric retracts for ease of installation but the it turned out to be more work than the pneumatic ones would have been.
First, the nose gear mounts differently from the Robarts gear so for the strut to be long enough for the plane to sit slightly nose high like the full scale plane, I had to cut out the former where the dowels plug in and in to the leading edge of the wing. That meant I had to add a couple more wing bolts and some structure to support them. I also had to put bolt plates in the wing like the rear bolts have and fill the space between the plate and the wing saddle with balsa for support.
Getting the fuel tank out with the pull pull steering in the way would suck so I installed a Hitec 225MG mini seer solely for steering and routed the cables out of the area. Now I can get the 14oz tank in and out without taking stuff apart. I used a rubber band to tension the cables when the gear is retracted and hope to figure out how to turn off that servo when the gear switch is in the up position on my DX8.

More later

bigbird
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Old Apr 28, 2011, 09:13 AM
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Looks great!
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Old Apr 28, 2011, 01:12 PM
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Coming along nicely. What size engine do you have powering your Airacobra??
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Old Apr 28, 2011, 01:18 PM
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Coming along nicely. What size engine do you have powering your Airacobra??
I was going with a .91 4 stroke but I just didn't like the way it fit. From all i've read a .61 two stroke will fly it just fine. I'm using an OS 61 fx.
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Old Apr 28, 2011, 02:59 PM
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I was going with a .91 4 stroke but I just didn't like the way it fit. From all i've read a .61 two stroke will fly it just fine. I'm using an OS 61 fx.
I bought a TF GE Airacobra from an auction in January. It has a Super Tigre 90 in it. I don't care for Super Tigres at all....too much tinkering. I have 2 and I could never get either to run right. Although, the last time I flew the Aircobra, a friend helped tinker with it, and it worked great. No deadstick on last 2 flights. I need to change the prop, but 2 things I found with it:

1. It took alot of runway to get off the ground (We have a 400' grass runway)
2. It sucks 16oz of fuel in 4 minutes. That's my maxx flight time with it. I pulled the 12oz that the guy had in there and sqqqqquuuuueeeeezzzzed at 16 oz in there. I had to get a running start in order to get it in there.

I have a TF Yellowbox Airacobra that I'm putting in the same engine (OS61). It's a friend of mine's engine. Runs great. I altered the design to fit a 24oz tank in there. Waiting to be painted, so I haven't balanced yet. I will be flying her in a few weeks.

I'm hoping that the OS61 doesn't go through fuel like my 91 ST does.
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Old Apr 28, 2011, 06:53 PM
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I have a Super Tiger .91 in my Hanger 9 P-51 and you are right, until you get them broken in, Super tigers are a pain. I suppose if you are one of those who like to break them in on a stand it would be OK but I'm not one of those. I've finally had a couple of non-dead stick landings my self ; ) I can get just over 5 minutes in the P-51, I've never used a .61 before but I'm pretty sure it's not the gas hog the .91 is.
Are you doing retracts? I could barely get the 14oz tank in.
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Old Apr 28, 2011, 08:41 PM
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Are you doing retracts? I could barely get the 14oz tank in.
The auction TF GE I have came with retracts....Robart spring air. For my TF Yellowbox, I have Robart nose gear and Yellow Aircraft 60 size air retracts for the mains. Mine should have the slight nose up attitude like the real ones. The Auction plane just has the 90 degree retract. No nose up attitude though. But what she lacks in scale, she makes up for in flying.

The fuel tank setup is about the only thing on the TF GE design I don't like. The plane is bigger than the Yellow/Red box kits, has aerodynamic/builtup tail, is nice to have engine mounted sideways. BUT, the tank placement could be better. It is the only way they can get away with not having a nose cover though. Makes the lines look alot smoother. I had to dremel a little bit of wood to fit it in there. Then once in (no coming out), I had a fun time jamming the foam around the sides so I didn't get air bubbles in the fuel line. When I redo the plane in the winter, I'll need to take the tank out, and maybe find a better way of fitting it in there. Thats the nice thing about putting a 24oz in my Yellowbox. Just hope it doesn't hurt me on weight when I go to balance her. I can always put a smaller tank.
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Old Apr 28, 2011, 10:44 PM
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But what she lacks in scale, she makes up for in flying.
Looks good, glad to hear she flies well. I'm going to do the Brooklyn Bum 2nd like Chris is.

I started putting in the rear stringers and decided to put in a rear hatch. I hate lead on the outside, well I hate using it at all but... I thought it also might come in handy for elevator maintenance also. Here is what I came up with.

First I copied formers F9 and f10, put a small space between the two F9s and the 2 F10s. Put in the stringers and cut them between the 2 F9s. Viola, a hatch. To keep it on the plane I used four rare earth magnets, two on the hatch and tow on the fuse. The canopy magnets from my Hanger 9 RV-8 which came unglued in midair. The sheeting was soaked in ammonia water and wrapped around the hatch to dry. Should be able to glue it on tomorrow.

bigbird
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Old Apr 29, 2011, 05:42 PM
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Hatch done

Turned out pretty good, kinda hard to get off so the magnets should hold it fine.

bigbird
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Old May 06, 2011, 01:32 PM
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Got some sheeting done

I finally found some time to get some work done. The rear is sheeted now.

I found ace bandages and some ammonia water curve balsa pretty well

On to the rest of the sheeting, my CB 3 1/2" spinner is supposed to be here today, only took 6 days to get out the door at the other end.
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Old May 06, 2011, 02:17 PM
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I found ace bandages and some ammonia water curve balsa pretty well
A trick I was taught and still use is watered down windex mixture. You can still 'Zap' glue your wood while it's still wet if need be.
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Old May 06, 2011, 02:46 PM
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The sheeting looks great! What kind of glue do you use? I have found that I need to move quickly when using Zap; I normally use masking tape to hold the wood in place. Your method looks like a winner, but I would assume that it takes longer...hence my question about the glue!
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Old May 06, 2011, 04:30 PM
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The sheeting looks great! What kind of glue do you use? I have found that I need to move quickly when using Zap; I normally use masking tape to hold the wood in place. Your method looks like a winner, but I would assume that it takes longer...hence my question about the glue!
I use a combination. Thick CA to position the piece so I get a good butt joint, but first I spread Tite bond glue where I can't CA, then let it dry.

After it is good and dry (both the sheeting and the stringer) CA the piece on and glue it to the stringer with CA at the other end. Once it is in place run a HOT iron over the places with the Tite bond and the glue bonds.

I do wing sheeting that way. It lets you position the piece and glue it down without a bunch of weights or tape or any thing. Run the iron over it and you are done.
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Old May 06, 2011, 09:58 PM
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Spinner

I got my spinner today from MECOA, they sent the wrong adapter

1/4 instead of 5/16

Such is life

bigbird
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Old May 09, 2011, 11:30 AM
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A little more progress with the sheeting, next I have to sheet the other side and still keep the nose ring in place. I didn't read the instructions all the way through so I sheeted to the nose ring on the top. I'm not sure why they would put the addendum at the end of the section instead of the beginning...

I made an L bracket to put on the prop shaft to hold the nose ring and will wet the stringers, hopefully that will hold it in place (and it will stay there!)

bigbird
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