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Old Jun 15, 2013, 12:12 AM
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poormansairforce's Avatar
United States, OH, London
Joined Mar 2013
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Build Log
PMAF P-51 Mustang with Maiden video and plans

I've always wanted to do this plane and after watching a bunch of videos on Youtube, I thought it was time. Its designed around a 2836 1500KV (see below)motor because its what I have on hand and will use 4 14g servos, 1 on each aileron, 1 for elevator, and 1 for rudder. Since all hardware is inside fuse the power system should be over sized accordingly! Plans are attached at the bottom of post.

WS=45" (1143 mm)
L=38.5" (978 mm)
Motor= 2836 1500KV from RCTimer pulling 30 amps at full throttle and 10+ amps at 1/2 throttle static on a APC 8X6 cut down to 7.5". This makes for nice flight times.
EDIT: The shaft on the 2836 was really short so next time I'll use this motor. A longer 4 mm shaft and should swing a APC 8X6 prop. Bigger props will get in the way when landing!
KF4
2 1/2" spinner
40 amp ESC but should be 50 amp!?
Weight=28 oz
CG is 1/4"-1/2" in front of spars.
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All the parts cutout:
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The weird five fingered part on the right is the canopy.

After thinking about the dihedral for a couple of days I came up with an incredibly easy way to do this. It solves some issues on some of my other projects as well. I set up a dihedral jig and I did a score and fold on the bottom of the wing layer and hit it with hot glue and layed back over onto the jig and made sure it was flat on the jig. After both sides are done it will somewhat hold its shape.
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Then I scored the bottom of the KF4 at the fuse and glued it on keeping the wing flat until the glue cooled.
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NOTE: On the prototype shown here the CF tubes were shorter than 22".
After scoring the bottom of the KF2 and gluing them on I measured 22" off of 2 3mmx1000mm CF tubes and cut them at that point leaving one piece shorter that the other. I slid the 22" CF into a channel in the KF2 and positioned it against the back edge of the KF2 and glued it onto the wing. The shorter one is the bottom spar. The inside ends of all 4 CF spars stick into a cavity I cut into the wing center and then after making sure the wing was flat on the respective dihedral boards and the center section was level I poured warm 30 minute epoxy into the cavity to create a "pour in place" molded wing joiner. Pour in at one end of joiner cavity to allow air to escape. Make sure all joints are sealed so epoxy doesn't leak out. The cavity will be much smaller when I change the plans to save epoxy. This creates a true spar cap system and is very strong. Once the changes are made I think the build time to get the wing built would be a couple of hours....because making airplane noises interlaced with sporadic cannon fire does not constitute build time....does it?
DISCLAIMER: I initially used 5 min. epoxy of a brand I had never used and it kicked off so fast it melted some foam which explains the crappy look! Lesson learned.
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You can't see the 2 bottom spars but they are there. You can see the tape on the bottom to contain the epoxy.
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Overview of everything done so far
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NOTE: I did a rebuild here to make the nose much stronger.
Firewall glued in with epoxy and flox. The 2 3mm CF tubes are glued to the top surface of the battery tray and epoxied into the chamfered holes flush with the face of the plywood mount. The 3rd CF tube glues into the channel in the vertical nose brace and epoxies to the mount in the same manner. This makes the mount very strong. It looks messy due to the rebuild!
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The 1" of dihedral at each wingtip is not enough, should 1 1/4" or more. Scale would be closer to 1 1/2" as noted in the plans.
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The CG is correct here at 1/4"-1/2" in front of spars.
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The prop adapter is too short for this spinner/prop setup so will need to look around for a longer one. I had to countersink the front of the prop to get it on. An aluminum spinner may be the answer!

The tail feathers are beveled and ready for tape. I initially used a skewer to do this and it wasn't stiff enough so I added the wire piece. The plans show a 3mm CF torque tube that is epoxied into the elevators to create the stiffness needed. I also added a CF tube in the horizontal stabilizer.The rudder horn is low so the elevator will miss the rudder push rod. The sloped brace for the rear fuse is to provide torsional stiffness.
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The canopy and upper cowl remove for access. The canopy is built separate and the bottom edges are formed by knife or sandpaper to conform to the fuse top before attaching. You can see the holes I cut into the back of canopy and fuse top to allow airflow through the fuse. The sloped battery tray provides torsional stiffness for the front end, and along with the CF tubes is very strong!
I started to heat mold a curve into some of the joints which discolors the foam a little.
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I cut a pocket into the wing and KF2 layers and sunk the aileron servos into them. The servo arm was hotglued to the aileron making sure the servo and aileron were centered.
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Building notes:
I didn't use tabs much since they tend to ruin the look and make mods harder so pay attention to double lines and the circles or semi-circles as these note where a foam part gets fastened. Mark all points on the edge of part or thru the paper before pulling paper templates off and only remove them as you go to prevent confusion. If you do the dihedral then check for clearance between the KF2s, you may need to bevel them back to allow room for the battery tray to fit in between the fuse sides. The plans have all the parts so no need to reuse templates. Print at 100% and measure the 50mm scale boxes on both sheets when printing them off at printers. You'll need 2 sheets of Depron or equivalent.

I have since painted it but have not flown it much due to weather and my Concept 6 build.
This is a walk around video:
PMAF P-51 Walk around (5 min 9 sec)


Here is the maiden flight and you can tell I'm nervous because when I launched it I actually poked a hole into the scoop with my thumb from squeezing too hard which caused it to pitch up and bank left. My wife talks a lot when she films me flying and the first part is boring:
PMAF P-51 Mustang maiden flight (9 min 4 sec)
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Last edited by poormansairforce; Jun 23, 2013 at 01:18 AM.
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Old Jun 15, 2013, 03:19 PM
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United States, SC, Charleston
Joined Mar 2007
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Excellent work on your P-51 Dan! & Congrads on your maiden flight!

BTW this is the most condensed build thread I have EVER seen Lol
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Old Jun 15, 2013, 09:48 PM
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United States, OH, London
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Originally Posted by demondriver View Post
Excellent work on your P-51 Dan! & Congrads on your maiden flight!

BTW this is the most condensed build thread I have EVER seen Lol
Thanks! If you thought that was brief then you obviously haven't seen my other one!
http://www.rcgroups.com/forums/showthread.php?t=1909539
I like my all information in one place so thats how I do it I guess.
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Old Jun 16, 2013, 10:44 PM
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Joined Mar 2002
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Dan,

Congratulations - the 2nd part of the maiden video is beautiful. It sure flies great. Stop by our field if you're ever up in Cleveland.
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Old Jun 16, 2013, 11:25 PM
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United States, OH, London
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Originally Posted by kdahlhaus View Post
Dan,

Congratulations - the 2nd part of the maiden video is beautiful. It sure flies great. Stop by our field if you're ever up in Cleveland.
Thanks, I'm rarely up there but may need to go to the Cleveland Clinic with my girls at some point. Do you have a link for the field/club?
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Old Jun 17, 2013, 04:51 AM
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Sure - http://www.clevelandradiocontrolclub.info/ The electric-only field is not too far from the clinic. You can fly as a guest if you have an AMA card.
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Old Jun 17, 2013, 12:16 PM
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Originally Posted by kdahlhaus View Post
Sure - http://www.clevelandradiocontrolclub.info/ The electric-only field is not too far from the clinic. You can fly as a guest if you have an AMA card.
LOL, I was on that site last night and wondered if that was it! Looks like a great club. It completely escaped me last night that we will be going to the Twinsburg festival in August and I saw that your not far away. Are there people there flying Friday afternoon/evenings?
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Old Jun 17, 2013, 12:21 PM
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I'm not sure - but probably as there are many retired guys flying. I fly Sunday mornings. But if you're up there on a Friday that's a good excuse to head out to the field.
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Old Jun 17, 2013, 09:28 PM
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Thanks! I'll definitely keep it in mind and will give you a heads up if I can do it.
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Old Jun 17, 2013, 11:49 PM
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Great job, Flying of the maiden video is awsome! Thansk for your plan sharing.

Robin. Z
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Old Jun 18, 2013, 12:30 AM
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Originally Posted by robinzeng View Post
Great job, Flying of the maiden video is awsome! Thansk for your plan sharing.

Robin. Z
Thanks and your more than welcome. If you build this then some pics and video are required!
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Old Jun 19, 2013, 09:14 AM
rcflyer729
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very nice build
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Old Jun 19, 2013, 09:38 AM
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Originally Posted by rcflyer729 View Post
very nice build
Thanks!
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Old Jun 22, 2013, 11:12 PM
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Very nice build. I am thinking about attempting building this plane. I didn't see posted what carbon fiber tubing size you used in this build. I apologize if you posted it I may have missed it
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Old Jun 23, 2013, 12:03 AM
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Originally Posted by autowarrior View Post
Very nice build. I am thinking about attempting building this plane. I didn't see posted what carbon fiber tubing size you used in this build. I apologize if you posted it I may have missed it
Sorry about that! I get so used to how I do things I forget you can't read my mind! The CF is all 1/8" or .125x32" tube from Grayson Hobby but you will need more pieces since its only 32". FYI, I had bought some from rcfoam and it was 2.93mm and the CF I've been buying from Grayson Hobby is sold as 1/8" and measures 3.14mm and is noticeably stronger! Because we are building a true spar cap system the strength is really good and even 4mm would work but if it gets too big then it becomes a little harder to lace the CF into the joiner box. I know you know this but to possibly save you any hassle have it printed 100% and check the 50mm x 50mm box for size before leaving the print shop.
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Last edited by poormansairforce; Jun 23, 2013 at 12:22 AM.
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