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Old Apr 10, 2012, 02:20 AM
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United States, AZ, Phoenix
Joined Feb 2010
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Build Log
Top Flite P51 kit going electric

I have always wanted to build one of the Top Flite kits and have now collected 3 so far. The latest one off Ebay was a pretty good deal and a perfect opportunity to try my hand at gluing sticks together. The tail feathers had already been completed from the previous owner but I won't be picky. This is my first kit build and I am not shooting for a scale look; I just want to build and fly a kit. I am trying to keep this as economical as possible and buy everything second hand or use what I have in stock. Here are a few pictures for everyone to take a look at. This is a great place to document some of the research I have been collecting to build the TF kits as an electric conversion. Chime in if you have something to say. I like the good and bad. I also like a lot of glue as you can see in the pictures!!

Planned equipment but subject to change:
Motor- Hacker A50-16L(Purchased V2 - V3 looks like it is out but was not in stock)
ESC- CC Ice 100(Already in stock, I have had this NIP for about a year)
Retracts- The kit I bought came with Robart 606 but I am opting for a set of Eflite 60-120 90 degrees that I just bought used for $80. I prefer the simplicity of electric vs. the air
Batteries and Prop- TBD but was thinking along the lines of 2x4s in series Mah still ??
Servos- Hitec HS 645MG
Spinner- Dave Brown 4" Parabolic
Propeller- APCe 17 x 12
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Last edited by haines74; Mar 19, 2013 at 08:21 PM. Reason: updated
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Old Apr 10, 2012, 02:45 AM
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United States, AZ, Phoenix
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When I was looking at all the different threads and trying to figure out how best to start the project; I realized I was always looking at the builders environment. I wanted to know how the builder set up his workbench and how everything was laid out. It is not usually mentioned in the build threads so I had to search in different sections of the forums. My workbench is in the garage and I utilized an old kitchen table measuring 3x5 feet. Many people used Homasote fiberboard , or drop down ceiling tiles for the bluprint plans to be laid out on. Homasote is not that readily available around me so I chose a sheet of Sound Board from Home Depot. It has worked very well for me, but I wish I would have had them cut it at the store to fit on the table because it makes a huge mess when cutting. I stapled the corners of the plans to the sound board and laid some visqueen over top of it all. It was nice to be able to walk around the back to maximize the surface area of the table. when I was at the hobby store I forgot to buy 30 minute Epoxy to join the wings together and I am still waiting on the Eflite retracts to arrive; so the wings were moved to the side to start the fuselage.
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Old Apr 10, 2012, 02:58 AM
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United States, AZ, Phoenix
Joined Feb 2010
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More pictures of the continued progress. The kit off ebay was missing most of the small hardware pieces and I am really at a point that I need some of those parts to continue. I have contacted the seller and he is trying to find what is missing but my forward progress will be slowed until I have more parts. I will try to clean up what I have in the meantime and get the wings epoxied together after I go to the store.


Question: Has anyone ever added up the weight of all the Robart air retracts, cylinder, and hoses. I would love to know what weight penalty is sacrificed. I will post the weight of my retracts when they arrive but the website shows them to weigh 4.2oz.
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Old Apr 10, 2012, 03:09 AM
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United States, AZ, Phoenix
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Last of my pictures so far. Dual aileron servos were added to the wings instead of the single servo method described in the manual. Many people mention that this is a must when building this kit from scratch. Some just say it is unnecessary and is added weight. I chose to build them mainly because I didn't have the control horns to work on and when I researched the Top Flite ARF P51; it is sold with dual aileron servos. I used 1/4 inch balsa stock that I had laying around but I did read one thread that said I should of used plywood(EDIT: I found the balsa was too soft and I cut them out and replaced with ply rails). My framed opening was measured to be identical to the flap opening and set about 1/2 inch down from the spar.
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Last edited by haines74; Apr 14, 2012 at 02:36 AM. Reason: Ply rails added
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Old Apr 14, 2012, 02:33 AM
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United States, AZ, Phoenix
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I was able to get some more accomplished tonight. I found the Eflite retracts in the mailbox and got to work trying to fit them in. Numerous builders have posted putting some extra wood in the wing to support the retracts. If anyone needs a little help from the occasional hard landing I am sure the candidate. So I helped myself to a few extra plywood doublers and a larger one piece ply gear rail. It looks like a hatchet was used to get them to fit correctly but I think they are going to work OK. After I was happy with the gear I moved on and finally prepped to join the wing halves. So now I have the wings clamped and waiting to finish drying.
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Old Apr 16, 2012, 11:45 PM
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United States, AZ, Phoenix
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Posting pictures from work completed yesterday. Didn't have time to document last night. The joining of wings halves is complete and just about ready to start the skinning of the wings. I have read many different methods in sheeting wings. Everyone seems to have a great method and I am going to try to take a little advice from everyone and use it the best I can. I really like the idea of using small amounts of CA to keep everything in position and then finishing everything off with Titebond with weights till it dries. Using CA alone would create a huge cloud of fumes that I don't think I could handle, not to mention the little room for error with dry times. I used a template made from heavy paper to give me a good start to the wing skin shape. This might have been an extra step but it helped me get a basic shape of the wing without too much cutting.
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Old Apr 17, 2012, 01:03 PM
Visitor from Reality
United States, VA, Arlington
Joined Dec 1996
12,788 Posts
Now here's an electrocution! Okay, will admit to having done nothing of this size - am assuming this is the larger 'scale' Mustang, not the small 46 glow sized sports semiscale one. But I have electrocuted a fair number of glow kits in the past.

First off - put down the glue, sit back and do some hard thinking. It looks like you can handle the basis of building and flying this model, but how are you on converting glow models to electrics? If I'm teaching granny to suck eggs, early apologies.

First off - fitting the new drivetrain. Your motor is going to need a much different mounting than the oily lump this kit was designed for. Before you get too far into the build, figure out how you are going to adapt the nose area to take your electric motor. Can you use or convert existing formers, or will you need new ones?

Next - refueling. There's a long way between having access to a pipe to squirt a new tankful of glow fuel into the model and replacing a big, hefty LiPo battery. Your battery demands a battery tray to sit on. That has to take the weight of the pack, plus have Velcro to hold the pack in place with Velcro straps to hold it in place even more when inverted, etc.

More packs = more fun getting them into the model.

You'll also need a hatch that allows you to get at the battery, unstrap and unplug it, then remove it. An inadequate hatch will cause you to say many naughty words instead of swapping a discharged pack for a fresh one and going back flying. Thinking about using the wing as a battery hatch? Forget it. Inverting a big, hefty model into a stand, unbolting the wing, unhooking the servos and retracts to get the wing out the way, then changing the pack and putting the wing back on is not fun.

Yep, been there, done all that. Won't do it again.

Good luck

Dereck
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Old Apr 17, 2012, 05:25 PM
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United States, AZ, Phoenix
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I am taking much of my information from previous builders and their experiences. I agree that taking a wing off every time you want to change a battery sounds horrible. Take a look at this thread http://www.rcgroups.com/forums/showthread.php?t=1206976
Post #9 shows how the ARF version of the TF P47 already has a built in magnetic cut out. My build is no ARF, but I am going to try and use this information to create my own battery hatch up in the nose of the P51.

It looks like numerous manufacturers sell motor mounts that I should be able to use. I like the Hacker model since it looks like the length is very adjustable. http://www.aero-model.com/Hacker-Bru...tor-Mount.aspx

Many builders mention that the nose will need more weight for a proper CG and I took that into consideration during the build. I know I should have used some of the techniques described by other electric converters to lighten the tail, but the tail components were already completed by the previous owner. I got the kit second hand. Getting the overall weight down and keeping the CG in check I feel will be my biggest struggle.

I have a good attitude towards it. If it works great, if not, well then live and learn and hope somebody gets it on video!!
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Old Apr 18, 2012, 09:34 AM
Visitor from Reality
United States, VA, Arlington
Joined Dec 1996
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Getting the weight down! Now there's a trick. Best way to do it with a kit is to re-design the structure, use the kit parts as templates to make new, lighter ones and then re-EBay the kit

Bin there, done most of that too! The GP CAP 232 I electrocuted ended up as the kit's cowling and rudder with an entirely new airframe between them. It's only resemblance to the kit was the shape - which was fine, it was a great flier by the time I'd gotten done. One 'number' I recall was reducing the weight of the wing mainspars from four ounces to two ounces.

Balance - shifting the battery up front can help solve all the issues that follow losing the lump of metal as drawn on the plan. Also, on the principle of 'every little helps', move all the RC gear forwards of the CG too. If there's a snag with moving batteries, it's if you have batteries of different sizes and weights. A lighter pack could cause an aft CG shift, but this you'll have sorted out in your workshop, not shortly after take-off

Another path, though a lot more work, would be A123 cell packs. With a little forethought, these could be built in and charged while in the model. Many of the larger NiCad/NiMh impelled scale models I saw in my earlier e-power days had no CG issues thanks to these packs and all that was needed to recharge was to plug the charger in and start it up

There's a lot goes into a model of this size and nature. If you reckon you can lose some weight on those pre-built tailfeathers, toss 'em and make a better set. The previous 'builder' was likely not the highly skilled craftsman you want to trust your drivetrain and RC gear to.

This thread and that one you linked to the P47 thread has me fair to drooling. Good job I don't have the room to build anything like this now. A Hawker Typhoon or Tempest never goes far from my imagination...

D
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Old Apr 19, 2012, 06:54 PM
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United States, AZ, Phoenix
Joined Feb 2010
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Dereck honestly I have not given the A123 batteries much consideration, I will have to check them out and see if they are right for me. Being able to just plug it into the charger is a great idea and needs to be visited. You also have a good point on just rebuilding the vert. and horiz. stabs; I am being lazy when you get right down to the point of it. Thanks for the ideas!

I have not been able to get much work done the past few days but here is a few pictures of what I have had time to complete. I decided that I wanted a separate servo for the tail wheel and added another control rod for the rudder. The ability to trim the tail wheel separate from the rudder seemed like a needed mod. For a novice builder it seemed very unreasonable to accurately trim out the tail wheel without the ability for future adjustments. Some skins added to the wings. I really liked the Titebond glue for this part of the project. A little squirt of Windex on the exposed side of the skin helped curl the balsa into a nice airfoil shape. With the help of a couple dozen magazines while it dryed; all the sticks and glue started to look like an aircraft wing.
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Old Apr 21, 2012, 10:07 PM
Visitor from Reality
United States, VA, Arlington
Joined Dec 1996
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Please tell us your wing servos are going to be on the inside. No model, let alone a WW2 fighter, looks good with servos hanging out in the breeze. It might do for BARFs and those huge aerobatic things - probably because it shows off their expensive servos - but not for a scale model of this size.

D
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Old Apr 22, 2012, 11:51 PM
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Joined Feb 2010
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Are you referring to the aileron control linkage coming out of the trailing edge of the wing through a small hole and attaching to a small clevis? I have seen that a few times and I wanted to replicate that idea; but now that I am looking, I have not been able to locate another build with that type of set up. I would certainly not set up this airplane like the pictures below.

I got some more done with the wing today. Finished off skinning the bottom and put one side of the top on. I haven't taken any pictures since it is buried underneath a pile of magazines drying. I should be able to update the gallery tomorrow.

The fuselage had a few more chunks of wood glued on and shaped as well. The pins holding the fuselage down were pulled out and I was able to examine the top side of the fuselage for the first time. It is not a very clean job and a little disappointing now that I am able to take a closer look. I have a 1/8" gap on one side and it is going to create numerous problems in the future. Not sure how I did this other than just in a hurry and not checking my work. It appears that I bowed the "Forward Crutch" while gluing it down somehow since this gap does not appear in the nose or tail of the fuselage side. Not too happy about this one.
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Old Apr 23, 2012, 07:05 PM
Rangers Lead the Way
Joined Mar 2010
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Good work. Nice plane to build. I have the ARF. I'm not following all the concerns cited above with repect to building this one electric. It is actually one of the best kits to electrify because it is one of the few warbirds that does not build ridiculously tail heavy, and the battery hatch is in the perfect place for easy Lipo access.

My only comment in seeing your pics is that I'd want to see beefier retract rails and area...3 ribs minimum and even more would be better, with ply sheeting reinforcement. It is impossoble to build that area too strong.
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Old Apr 23, 2012, 09:16 PM
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That's going to be nice!
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Old Apr 24, 2012, 11:39 PM
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Thanks for the feedback guys; I have a couple pictures from yesterday that I did not have a chance to post up. TTRotary if I'm not mistaken, I have seen your username in a few other Top Flite builds and have noted some of your previous experience. Three extra pieces of plywood were added to the ribs that the gear rails sit on and another piece on the inboard rib that will be cut for the wheel well. I tried to strengthen the rail itself by making it a one piece U-shaped mount. Now that you mention it, stretching the rails across three ribs makes a whole lot of sense! Well I need to ponder on this tonight. My first instinct is to just keep on with the build so it doesn't turn into the kit that never gets finished and posted in the classifieds.

I rushed skinning the top yesterday and put a couple cracks where they don't belong. So today turned into a good day to step back and take a break. I should be able to get back at it tomorrow and finish the topside. Once I have that finished I will post up the results.
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