Phoenix Model 1.4M P-51 Nitro ARF Build

[tudordewolf]

Been working on this one for a while, it's reaching a point where there's enough to share.

The first thing that stuck me is how much the bare fuselage looked like a ship from star wars, (specifically a naboo fighter) especially if I held up the spinner to it:

The colors, the way the tail points & especially the contours under the cockpit, which on the P-51 are to smoothly blend with the wing, are just "left on" the ship.

This one has been a lot of work. The other 2 ARF's I put together before this one were less work across both of them.

As shipped, the kit leaves gaps and lines that I've closed up with extra monokote, I feel like a small piece of extra pieces of the colors used would be a smart addition to the kits, but oh well, they're only ~$20 for a lifetime supply of patch-pieces in the form of a whole roll.

I went through several choices for the landing gear retract servo before my first choice even arrived, I settled on an SPT 4420LV and it is perfect in that role. Optimized for standard voltages so it offers 20kg*cm of torque at 6.0V, & low profile, as a normal height servo wouldn't fit:

At 125% endpoints on the remote, it has 120 degrees of travel. Using the right sized servo arms though, this is still plenty to lock the landing gear at both ends of its travel- video to follow soon.

For the rest of the plane, I'm using DS-Power "S011M" servos which advertise ~4.3kg*cm at 6V, perfect for replacing old standard servos with something a bit smaller and lighter, at 15x35mm footprint instead of 20x40, and they fit a standard 25T horn. These have been my go-to for my nitro planes, and they're a steal at under $10 a pop even for the metal geared version.

Of course, all the plane's servo trays are cut to 33x16mm, a size very few brands even cater to. I thought I'd finally found them in the 3.5kg-rated "M0200" servos, which had the right footprint, but a miniature servo spline, so I'm only using 1 of those for the throttle, to at least use up some of 5 I bought thinking I'd use them throughout. The Sonic from Phoenix model also assumes this unusual servo size, so I've used 2 of them so far, they work well enough. It's just a little woodworking to adapt them, but that's extra steps that turn into extra days.

 

[Hobbydude2]

Id look into a exhaust tip extension to keep that nasty oil off your birds skin. Once soaked its almost toast. I got a cheap little one that keeps things clean.

 

[tudordewolf]

Id look into a exhaust tip extension to keep that nasty oil off your birds skin. Once soaked its almost toast. I got a cheap little one that keeps things clean.

View attachment 206947

I went all-out and made a full-length tailpipe for my sonic, it even flew pretty well.

I've used the same deflector as you have on my Avistar when it had a 2-stroke and it worked well, the 4-stroke hasn't had much of an oil buildup issue, I think because it ejects it at a pretty good angle down and away from the body.

I'm going through a lot of effort to seal this one up, strips of trim along all the glued edges. I'm giving it a carbon fiber wing tube, the kit included an aluminum one with 1mm thick walls, I went with 1.5mm carbon fiber which this calculator estimates will be still be ~14% lighter and 38% stronger than the aluminum one.

I also cut away the film that goes over the edge onto the joining face of rib, which gets glued to the opposite rib, so that it doesn't create a gap between the wood faces, and also for more than double the bonding surface area.

 

[Hobbydude2]

Ah, I got ya. Nothing bums ya out than a model soaked in nitro oils. You going to do a video of her flying, that would be cool to watch.

 

[tudordewolf]

Finished the wing, the belly scoop took some extra sanding to fit flush. The instructions were to glue it directly to the monokote, but that didn't appeal to me quality-wise so I made a template of its "footprint", traced it onto the wing, and cut away the film only where it would touch:

I've probably mixed over a dozen little batches of epoxy, I do a gram at a time, and used a syringe to fill in the gaps you can see on either side of the nozzle tip, as well as throughout the front of the plane.

 

[Hobbydude2]

Finished the wing, the belly scoop took some extra sanding to fit flush. The instructions were to glue it directly to the monokote, but that didn't appeal to me quality-wise so I made a template of its "footprint", traced it onto the wing, and cut away the film only where it would touch:
View attachment 208291
View attachment 208292View attachment 208293

I've probably mixed over a dozen little batches of epoxy, I do a gram at a time, and used a syringe to fill in the gaps you can see on either side of the nozzle tip, as well as throughout the front of the plane.

View attachment 208319View attachment 208320

Looking good, interesting way of despensing glue.

 

[tudordewolf]

Currently engaged in a mad quest to cover every surface that might encounter oil mist, including the edges of the fuel tank hatch & opening, and the complicated engine mount shape (compared to the 2 sides & a firewall on my non-cowled planes), which I've also epoxied for good measure. Fully silver-filming the engine bay rather than painting or just epoxying is something I've done for my other builds and I like the crispness it adds to the finish.

 

[tudordewolf]

Looking good, interesting way of despensing glue.

It's helpful for reaching into nooks and crannies to reinforce key areas, and also apply precise amounts to save weight. For example, this piece was originally completely loose, glued only at the bottom where it slots together:

 

[CertifiedMike]

I didn't know there was so much to getting an "ARF" from "A" to "R"!!!
Its a beautiful looking plane! I like the colors.

 

[tudordewolf]

I didn't know there was so much to getting an "ARF" from "A" to "R"!!!
Its a beautiful looking plane! I like the colors.

Thanks, the thought of it being finished is what keeps me going. A lot of the work I'm creating extra for myself, but the finished product is worth it to me.

Some of the ARF's I've built did come together in just a weekend, like the Sonic (...the second time I built it), and the Avistar didn't need any epoxy at all, plus its CA hinges came pre-glued.

The name "Almost-ready-to-fly" does seem like a stretch at first, compared to the BNF/RTF/PNP planes which are more or less "finished' and just need a few unpacking / setup steps, but it makes sense considering the old-school "short kit" which didn't even include all the wood you would need, Having the "framing' and main covering done is a big savings. I also realize that including any of these extra steps I'm including would only drive up the cost of the ARF if they had to be done beforehand, and I'd still wind up refining it myself to put those finishing touches on it.

 

[CertifiedMike]

I believe I'd start flying with a foam plane in my back yard in order to learn how to fly.
If I found the wind too difficult, I could see moving up to a balsa to add stability BUT I'd likely be buying one thats more "done" and expensive.
At least so I can see, feel, know what its SUPPOSED to be.
I think my desire to fly/learn to, is overshadowing the fun in building the plane.
Once I learn, I think I'd enjoy building planes too.
I do a fair amount of tinkering. 1:1, small engine, nitro, surface... planes and drones just seem naturally... next.
Its fun watching your posts and builds.

 

[Hobbydude2]

It's helpful for reaching into nooks and crannies to reinforce key areas, and also apply precise amounts to save weight. For example, this piece was originally completely loose, glued only at the bottom where it slots together:

View attachment 208631

Gotta love balsa wood.

 

[tudordewolf]

I believe I'd start flying with a foam plane in my back yard in order to learn how to fly.
If I found the wind too difficult, I could see moving up to a balsa to add stability BUT I'd likely be buying one thats more "done" and expensive.
At least so I can see, feel, know what its SUPPOSED to be.
I think my desire to fly/learn to, is overshadowing the fun in building the plane.
Once I learn, I think I'd enjoy building planes too.
I do a fair amount of tinkering. 1:1, small engine, nitro, surface... planes and drones just seem naturally... next.
Its fun watching your posts and builds.

That's exactly how I started, an Aeroscout RTF and a few Aliexpress cheapies to practice on. My mission from the start was to play with nitros though, especially the cool 4-strokes.

Finished covering the front, a little overkill, but since it's a cowled engine, I figure it'll pay off since that interior space will probably get pretty oily over time, if only for lack of access once I fit the cowling.

 

[tudordewolf]

Nearing completion, got the engine mounted. Had to cut down and countersink the engine mount by the carb to make it fit, but after that it was able to use the "stock" mounting holes.

It has a split elevator and the manual has you using a block with set screws to marry the 2 rods to 1 servo link, but I didn't like the multiple points of failure counting on 3 set screws in plastic to hold the elevator. I instead went with 2 links directly to the servo arm, and hooked them up to different holes on the control horn, and managed to get it so they move together. I put Z-bends in the ends of the elevator rods to give them some clearance, left pointing straight they would have been right up against the edge of each control surface.

 

[WickedFog]

Nearing completion, got the engine mounted. Had to cut down and countersink the engine mount by the carb to make it fit, but after that it was able to use the "stock" mounting holes.

View attachment 212218

It has a split elevator and the manual has you using a block with set screws to marry the 2 rods to 1 servo link, but I didn't like the multiple points of failure counting on 3 set screws in plastic to hold the elevator. I instead went with 2 links directly to the servo arm, and hooked them up to different holes on the control horn, and managed to get it so they move together. I put Z-bends in the ends of the elevator rods to give them some clearance, left pointing straight they would have been right up against the edge of each control surface.

View attachment 212219
View attachment 212220

So the servo with the two linkages control the two elevators? Wouldn't that that throw the left one farther than the right one? I've never built an airplane, but wouldn't something like this be better? So both rods had the same throw? Just curious.

 

[tudordewolf]

So the servo with the two linkages control the two elevators? Wouldn't that that throw the left one farther than the right one? I've never built an airplane, but wouldn't something like this be better? So both rods had the same throw? Just curious.
View attachment 212225

You're exactly right - but how to do that? My solution was to offset the difference on the other end:

So that when extended, they move the same amount:

 

[WickedFog]

You're exactly right - but how to do that? My solution was to offset the difference on the other end:

View attachment 212394

So that when extended, they move the same amount:
View attachment 212395

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Oh, that makes sense then lol. Nicely done.

I'm not an airplane guy, but I swear I have seen link ends with double inputs on them. Probably years ago.

 

[tudordewolf]

Finished wiring it up, made a silly amount of work for myself in order to avoid using a NiMh flight battery, mostly to eliminate the chance of brownouts and simplify charging logistics. I use a 3S lipo and 6V BEC, that way there's no voltage fade based on charge level, and I can monitor the lipo with telemetry to get a very linear read on its remaining capacity. I even split the power into 2x BEC's, one for core flight controls, and one for accessories - flaps, gear & onboard glow driver.

To wire that up, I made this cable which takes the signal lines for channels 6, 7, and 8, and powers them from the auxiliary BEC:

And this wire which takes power from the first BEC and feeds it into the receiver through the 6,7,8 power pins:

All wired up, doesn't look too bad in access bay, battery sitting snugly above.

Got the wing on and everything moves like it should, just need to fit the prop and start breaking in the engine once it warms up a little.

All said, I've done about 40 pin crimps and a dozen solder joints instead of just using a 5-cell hump pack NiMh several of which I already own.

I've done this on my other two planes and plan to keep on doing so, but this one was made substantially more complex by the second BEC.

On the plus side, the advantages I mentioned are part of the plane forever now, and the whole arrangement is (surprisingly enough) also lighter than the NiMh pack, ~90g instead of 116g - a whole ounce saved!

 

[CertifiedMike]

Finished wiring it up, made a silly amount of work for myself in order to avoid using a NiMh flight battery, mostly to eliminate the chance of brownouts and simplify charging logistics. I use a 3S lipo and 6V BEC, that way there's no voltage fade based on charge level, and I can monitor the lipo with telemetry to get a very linear read on its remaining capacity. I even split the power into 2x BEC's, one for core flight controls, and one for accessories - flaps, gear & onboard glow driver.

To wire that up, I made this cable which takes the signal lines for channels 6, 7, and 8, and powers them from the auxiliary BEC:

View attachment 212430
View attachment 212427

And this wire which takes power from the first BEC and feeds it into the receiver through the 6,7,8 power pins:
View attachment 212424
View attachment 212425
View attachment 212426

All wired up, doesn't look too bad in access bay, battery sitting snugly above.
View attachment 212428

Got the wing on and everything moves like it should, just need to fit the prop and start breaking in the engine once it warms up a little.
View attachment 212429

All said, I've done about 40 pin crimps and a dozen solder joints instead of just using a 5-cell hump pack NiMh several of which I already own.

I've done this on my other two planes and plan to keep on doing so, but this one was made substantially more complex by the second BEC.

On the plus side, the advantages I mentioned are part of the plane forever now, and the whole arrangement is (surprisingly enough) also lighter than the NiMh pack, ~90g instead of 116g - a whole ounce saved!

I have done stereo and alarm intalls in 1:1 that had less wiring and fewer plugs!
What crimping tool(s) do you use?
I don't know if my hands would ever allow me to work in such a cramped spot!
This is an amazing build!

 

[Hobbydude2]

I have done stereo and alarm intalls in 1:1 that had less wiring and fewer plugs!
What crimping tool(s) do you use?
I don't know if my hands would ever allow me to work in such a cramped spot!
This is an amazing build!

Some rc birds you can remove the reciever and the esc or servos and to plug it in wire set by wire set. Then you can do the install. I may have wired quite a few birds myself, and its second nature, just make sure the aileron dosnt get mixed with the throttle wire.