mjepps72

Hello all, I am returning to building airplane kits after nearly a decade of not doing so. In that time I dabbled with helicopters and cars, but the lack of building in those areas ceased to hold my attention. I chose this kit because A. it was cheap, and B. I've always liked the P-51. I have build several P-51 kits before so I am familiar with its quirks. I'm starting this thread mainly to keep track with text and photo entries of my progress and also because I am going to make this an electric build out as opposed to the plans recommended .049 - .10 gas power plant. Any feedback or previous build experience on this kit would be greatly appreciated. I will be posting pictures soon.

MJD

My Feedback: (1)

Well, they fly great with anything from a TD .049 to a .15 in the nose. Sound pretty cool too. But.. sigh.. I guess it would be okay with a lekkie in the nose, long as it's overpowered enough I guess. You could stick a little piece of playing card behind the prop to make engine noises too.



MJD

mjepps72

Oh I hear ya MJD. I have mostly flown gas planes since I was about 10 years old. I'm only going electric because the closest club field to me, which is about 2 miles away, is electric only. It's in a big park/water retention area. Judging by its size and weight it looks like a 400 motor would be perfect but I like your idea better of putting something with a little more zip in it.

nekked_man_2000

I'd be interested in what you power it with. I built one of these about 15 years ago and never covered it. Can't figure what I want to do about the plastic top. Anyway, I built it for a td 049, then butchered the nose for a Norvel when I got one of those, but the throttle arm was going to be outside of the cowl. So the project floundered. Now, with the current brushless stuff I've thought about bringing it to life. I put a lot of work in it and didn't really want to fuel soak it. Problem is, most of the info I find is for Outrunner type motors. For the narrow nose on this I think it will need an inrunner...tough to find good information. For me anyway. Also might be a little tight with the battery pack, may have to get creative with the servos, but I think it would look cool without a motor sticking out. I have the original magazine article from rcm scanned in my computer, I've thought about just starting over with the electric idea in mind. Then I wouldn's have to deal with covering the plastic turtle deck. I'll follow your post with interest. I love my gas planes, but I have to admit for my 1/2a size stuff electric is starting to look real appealing.

Austin

mjepps72

Thanks for the info nekked. I was going to scrap the plastic top portion, but think I should just work with it since it seems to be the lightest solution. As far as the battery pack goes, I'm experimenting with a heli battery that is lighter and smaller with the same power ratings as the recommended airplane one.

Attached is what I have done so far. Not much, but between career and family, I get done what I can when I can.

combatpigg

My Feedback: (3)

I like the idea of electric power for this model, just as long as someone else is doing it
I built one many years ago and it barely flew with a TD .049. It ripped around pretty good with a .15 and was still light enough to belly land on grass. Figure that this power system weighed 9 ozs with a full tank, 7 ozs empty and produced 300 watts. I can't believe that I used to fly it with the standard tail feathers provided with the kit. A lot of glue went into keeping the rear end of that plane ready for the next flight.

KidEpoxy

Maybe a long can ~22mm outrunner?
like a 200w class, 22x17 or so with a 8x4 or 8x5 prop

mjepps72

I noticed that combatpigg on the plans and now that I'm on the tail section part. It seems a bit flimsy, especially since I plan on belly landing this thing. I don't wanna glass it since from what I'm reading indicates a pattern of tail heavy problems on this particular kit. Maybe put a few glass strips on the insides of the two fuse sides near the back. How did you get around it?

combatpigg

My Feedback: (3)

Actually....I tossed the plane last year but IIRC the tail feathers were only 3/32" thick. I would rather see 8 pound wood, 1/8" thick. I wouldn't change too much, the plane is pretty well built for anything that a .15 can dish out. I think it weighed in the mid to high 20 oz range with 2 HS81s and 1 HS55...270 ma nicad pack. I painted the fuselage over bare wood and after several years the grain of the wood split and the plane looked like a mosaic.
If you monitor your "load plan" during the build, I don't think you'll have any CG issues.

mjepps72

Thanks for the info combatpigg. I think I will switch out for 1/8" balsa now while it's still detached from the fuse. My current plan is using only two mini servos (elevator, aileron) with a great planes T600 brush motor system (only because that's what I currently own) and I plan on covering with coverlite microlite film. I'm still doing some research on the brushless outrunner motors as well.

Entropy

My Feedback: (2)

Good info. I'll be building mine with a Norvel .074. I'll have to keep an eye on this thread. Just gotta clean up my workbench from the "29.75 'Lil Rascal with a Norvel .049 build before I start on the Mustang.

mjepps72

Not much progress since last post. In the process of moving, so I get to it when I can. All I've really done is add a few more pieces of wood to the fuse and I took the advise of combatpigg and made the stabilizers out of 1/8" balsa. Good call, the 3/32 stuff that came with the kit was pretty flimsy. Did a little work on the upper deck by trimming the plastic upper to fit. Attached is a pic of these pieces all stacked together.

Next step is to paint the visibile parts inside of the canopy black, paint the inside of the plastic upper deck (except for the canopy portion) silver. I also need to start shaping the cowl blocks too, but I'm waiting on a Great Planes brushless motor (outrunner) that I ordered to come in so I can mount to firewall and fit the front blocks and nose ring to it.

More to come as I get time.

Mike

mjepps72

Installed, carved and rough sanded front upper cowl to match the upper plastic fuse section. I'm thinking that since I'm using covering on this model I will need to completely cover the fuse and attach the upper fuse section (plastic and balsa) last. I fear if I mount it before the rest of the fuse is finished, then I may melt some of the plastic while trying to cover the fuse.

Should be getting the motor and spinner tomorrow in the mail, so I can start planning the mounting and forming of the nose...

Mike

mjepps72

Got the GP Rimfire brushless outrunner motor in today. A rough fit looks like I will have to make another firewall or some pretty long extensions on the motor mount. It's a tight fit so now the question is: How much air flow do these motors require? I can make it fit as is with very little ( 1/8" ) clearance around the motor near the front and hollow out the bottom cowl so that it channels air through, but I'm not sure this will be enough. I'm going to look through the brushless forums (if there is such a thing) to see if there's any info on this subject already. If anyone reading this has any input, I'm all ears and would like to hear other opinions.

Mike

combatpigg

My Feedback: (3)

Mike, there must be all kinds of experience with cowled in installations at the electric pylon forum.
The original had overheating problems, so if your's does too, at least it will be "scale"

doxilia

My Feedback: (3)

Mike,

any progress on your build? Which Rimfire did you end up choosing? What prop?

I'll be using a 28-26-1600 on a HOB FW-190 spinning a 7x5 or 8x4 APC prop (build on hold at the moment). I ended up modding the front by making the nose ring section solid with a 1/8" ply insert to mount the motor directly to it. I also drilled out the FW to essentially turn it into a much lighter former.

I also installed retracts, dual aileron servos and flaps! Couldn't help but have fun with this one.

David.

skaliwag

My Feedback: (1)

I suggest you don't skimp on the Amp rating on your Controller with all those servos wanting their share of juice.

doxilia

My Feedback: (3)

Thanks for pointing that out Skaliwag. It has been thought of. As there will be 6 servos in the model I will also be using a separate CC 10A BEC along with 1350 or 1500 MAH Lipo's for motor and radio. Hopefully that'll work as a separate radio battery is mostly out of the question on a model this size.

David.

MJD

My Feedback: (1)

I've moved up one balsa thickness in many of my "standard" choices - an excellent example being light 1/8" versus 3/32" on occasion for 1/2A tail surfaces and never again 1/16", and a bit up the density scale for .15's - and esp. if I have a nice piece of light and strong quarter grain to hack up. I'll use a good piece of 3/32" for 1/2A any day, and avoid 1/16" entirely. For .15 I would even go light 3/16" but in that case I would tend to fuss over airfoil shaping.

What might have been my first foray into the exciting and rewarding world of overpowering RC aircraft was an old Sterling Mini-Fledgling on which I had grown tired of the Medallion .09, and swapped it for an OS MAX .15 UC. Not a hot engine in particular, but running open exhaust on, most likely, a 7-4 prop it hauled the aircraft around pretty smartly and landed a bit hot due to the great care I took in setting the CG. On some flight before #10, it fluttered off the elevator with predictable results.. about a 60 degree full power approach and landing.

MJD

mjepps72

Doxilla,

I am using the same motor with a 7x4 prop, well at least that's the plan. I apologize for no updates lately. I just finished moving and am still in the process of unpacking and putting my workbench back together. [:@] I have taken a different approach to the front end. I ended up cutting off everything forward of the firewall, mounting the motor, then I used scrap block balsa to make a form of the nose. My plan is to now glass that form and make a small glass cowl held on by 3 or 4 small screws... I know, kind of overkill, but for me building is at least half the fun and I like trying new things. So on my setup the engine mounts to the firewall. I will post some pics as soon as I get my garage in order... I don't know why the wife thinks that her kitchen and the babies room comes first... go figure.

doxilia

My Feedback: (3)

Mike,

nice solution. Having a cowl certainly makes access to the motor easier. I basically did the same thing on a 44" span HOB T-6 which was originally designed to use a coke bottle bottom as a cowl (back in the '80's). Since they are no longer available, I made the cowl out of wood. Although I finished it, I'm going to use it as a plug to make a glass cowl. The nice thing about a cowl on a T-6 or P-47, for example, is that one can mount it with screws on a backplate so they can't be seen. Maybe this is less scale though.

Frankly, mounting the motor to the FW is a much nicer solution. The main reason I mounted it to the nose ring is because I wanted to place a spinner on the model and I therefore had an even longer reach for the screws to the FW since the can is reversed (backward) and the prop is mounted to the shaft. Later I realized that GP makes a prop adapter that fits on the can when you remove the two prop "soft mount" screws... oh well.

I may build the P-47 on the flip side of the plans and modify it to be more like the layout used on the GP ARF. Maybe up the scale a tad (~10%).

BTW, how many Watts is a 7x4 supposed to pull? I figured we'd want to be in the 200W realm with a 24 oz AUW.

David.

mjepps72

Doxilla,

Not sure on the wattage for that prop. I know that's the smallest recommended size for that motor. That was the main reason behind me doing the glass cowl approach. After trying to mount to the firewall using the can and prop adapter, then putting the spinner on, I had no room whatsoever to get at the mounting screws and it was dam near impossible to get the motor out or in without possibly breaking something. Won't be scale this way, but I was going for more of a fun park flyer style anyway, so ease of access to everything will play an important role for me. I remember that T-6 and reading in the old Tower Hobbies catalogs (before it was online) about the coke bottle front end.

combatpigg

My Feedback: (3)

Mike, nice to see this build back on track. Have you got your question about heat build up answered? It seems that in some of the articles I've read, they use the entire fuselage as a flow through vent.
How about dry ice?
Have fun setting up your new shop.

doxilia

My Feedback: (3)

My approach to cooling is simple. Allow air into the "cowl" either through a contoured opening in the bottom for a balsa cowl or NACA inlets for a glass cowl. Of course, beside motor, ESC and batteries (especially) need to be cooled. This is one of the reasons for hollowing out the FW as it will let air right into the fuse from the cowl bottom which will flow over the electronics and then back out the rear bottom of the plane via an opening.

This sort of stuff is quite common with electrics. Rule of thumb to draw air through the fuse is to have an opening at the front which is 1/3 the size of the opening at the rear. With a P-51, something could be fathomed with the air scoop under the wing.

David.

mjepps72

I've done a little research and see that getting airflow through the cowling and battery/esc area is key. I planned on creating a few inlets on the cowl with and exit at the rear bottom of the cowl for the engine and the same for the battery/esc compartment as well. Just ideas at this point, so have no real setup in mind yet. Thanks for the good info doxilia on the rule of thumb on the air flow with the sizing of the inlet vs. outlet. I will keep that in mind when designing it. Was thinking there might be a way to get air coming in under the spinner area and channel it all the way through the engine compartment and battery/esc compartment... not sure though.

mike