VQ Models P-51B - A Used Airframe Rebuild

Amaadur Rahman, a fellow RC Pilot from SNHFE in Merrimack called me a few weeks ago and told me he had been given a VQ Models P-51B Mustang airframe that was in good condition (the wings actually measure 61 inches). It was too big for him to transport, and he thought I would enjoy repairing and setting her up, so he gave it to me! Thanks, Amaadur!

It is in pretty good condition. I am going over it carefully and am trying to keep my costs down. I have on hand a Hobbywing 100A ESC, and a HeadsUpRC 5065-04 1400 watt motor (at VQ Models estimated 7 lbs AUW, thats 200W per pound. My other choice was a 700W motor, and ain't nobody got time for 100W per lb. But that max watts is likely on a 8S battery, and I am flying it 5S, so it will be interesting to see how many watts it ends up drawing). I also have an Orange RX 3 axis stabilized receiver, brand new.

I want all metal gear, digital servos, so today I ordered 4 Corona DS329HV Digital Metal Gear Servos, and a Turnigy 5A 6V SBEC. I have 4 5S 4500 mAh batteries that may need replacing, and one 6S that likely does need replacing, and they fit. Someday I will, but once I know what she likes. I am also replacing those ugly fixed gear for retractables. I have the same servoless retracts I used on the Spitfire, and today ordered a set of struts that are for the Spitfire as this about the same size, from Tower Hobbies. They are updated from the ones that came on my Spitfire and are rather cool looking.

Today I started on the fixin' up.

The model is in pretty good shape. I can't match the stock cote, so I decided that I will put D-Day stripes on that right wing.

Its a sign that the pilot came loose, and I had to re-install him. The canopy came off easily and he's now sitting proud.

I wanted a bigger tail wheel, so I swapped it out.

The cover was on wrong and wasn't flush, so I fixed that. The tail wheel was loose on the turn thingy, so I changed out the set screw for a screw-screw and snugged it up as best I could. Leaving the weights on for now.

I rebuilt the cover and the doors and coted it. Snazzy.

Curiously there is no vent. Electric aircraft, especially one with a huge motor and ESC need a lot of airflow and most have an aft vent to allow flow-thru of cooling air. So I decided I would cut a vent hole and use a vent cover from an Eflite Pulse 25XT that I painted. Marked out the opening.

Opening made. There is nice continuous airflow, but I will make an opening in the cowl under the prop.

Epoxied for strong hold.

Vented.

The wing-fuselage cover is broken and I wasn't sure how to fix it...

I decided to use foam and wood filler.

Trimmed a piece of painters tape to mark the curve.

This is the dense wood filler I am using. I don't want to fill the entire space with it, so trimmed some foam...

And stuck it in the hole.

Then filled it with wood filler. A few hours later I light sanded it, and this weekend I will finish it. I am hoping the silver paint I have is a fair match. Its a warbird, it doesn't have to match. Not sure if it won't fall off as it won't flex well.

I installed the motor. Pretty much fit the stock holes.

I epoxied the battery tray (behind the clamps) as it was loose, and made a small cross piece to mount the receiver, here being epoxied under the clamps.

That's pretty much it for today. This weekend I will finish off that wing cover and make the vent opening in the cowl then install it. I will start repairs on the wing cote and put those invasion stripes on the top, and install the retracts, and when the struts come in those too. Same with the servos, the SBEC, and the receiver. They should all be here in the next couple of weeks! I think she is going to be a great flier.

FOR THE SCORE!

Perfect maiden weather.

I took the VQ Models P-51 Mustang that I finished rebuilding months ago out for a first flight. OMG, what a flier! Power! Grace! Control! Balance! Speed! Acrobatic! Stable! Flying 6S she was an absolute pleasure from takeoff, to the lack of any trim needed, into advanced spins, rolls, inverted flight! Everything works! Landing gear go up, go down, do up and down again!

Brought her down in a Bahgdad Spiral and lined her up for a landing. She comes in with a lot of speed, we'll bleed some off in level flight a foot off the ground.

BAM! Right into the fucking soccer goal. Are you f%*#ing kidding me?

She needs a new wing, replace two prop blades, replace the landing gear, that's it. Fuse is without a blemish.  Two warbird maidens, two amazing first flights, two bad crashes.

I've emailed VQ Models to see if they can help me find a replacemrnt wing. This model has been discontinued...

MotionRC Delivers, Sweet Results!

I have recently started buying parts from MotionRC, and one of the things I appreciate most about a vendor is quick processing and shipping. These folks rock: part arrive 3-4 days after I order them.

I had ordered the 4-blade prop from the FMS 1700mm P-51, and it really was too big for the VQ Models P-51, coming in at 17'. I ordered the prop for the FMS 1400mm P-51, and its a very nice fit at 14". A quick test last night and she ran fine on 6S drawing about 55A and making about 1200W, but I didn't run her up completely to full throttle. This prop, like its bigger brother, has a hex shaped box on the bottom of the spinner to drive the spinner from a similarly shaped hex on the shaft of the motor. My smaller shaft (okay, I hear that...) doesn't have the hex, but it seems to work fine. It was challenging to get the prop nut secure without stripping the shaft trying to hold it while tightening it. It also took me about an hour to get the engine aligned with the cowl... for some reason it was just not staying where I put it, but once I found the sweet spot she spaced perfectly.

She is pretty much done and is ready to maiden! Does that not look awesome? I am glad MotionRC stocks these parts.

Holy shit... that scares the bejeezus out of me!

I made some major steps forward today on the VQ Models P-51B.

I installed the Corona DS329HV mini-servo's I got from Hobby King. I'd like to pretend I did it on purpose, but they were in the standard servo section and I didn't look at the measurements... But I was going on specs for torque at 6V and these met my requirements at the price I was looking to invest. It just meant I would have to modify the servo trays.

It took me a while to fish the line through the wing to pull the servo lead through. This is the original size of the opening.

I cut some plywood and fitted it to the opening and the mini-servo.

And cut a piece to fit at the top to balance the edges. It was easier to do this in two pieces.

Servo fit tested. Snug.

And installed completed. They are fast and will work well with the Orange Rx3 stabilization receiver.

Now the terrifying part...

This is the 17" 4 blade of unknown pitch from the FMS 1700mm P-51 Ferocious Frankie.

Its ginormous...

The spinner is a tad big for the cowl, but not distracting wrong.

She's gorgeous!

And when I put the Watt Meter on with a fresh new 6S, and went to just above idle to check the edges of the blades to make sure they were aligned, she made a powerful roar...

Then I slipped the throttle up to 50% and the roar became a banshee.

I got to about 65% when the Watt Meter read 1800 Watts, and she was pulling like a monster chained, and the sound was the most frightening power sound I have ever heard! This was magnificent! But if I use this prop I am going to have to put a throttle curve in and governor the max throttle down a lot! This was amazing. 

When I received the 17" prop I didn't know quite how big it was. I was trying to find a prop that fit a 60" or so plane and the 1700mm came close at 66", and the 1400mm a little short at 55".   I went with the bigger one. I think its too big, though I was planning on a 17" twin blade, with a 4-blade I need to come down a couple of inches.  I have already ordered the same prop but for the 1400mm P-51. I have no idea how big that one will be, but I expect a couple of inches shorter and better suited. I think that cone will fit well too. MotionRC is wicked fast at sending stuff, so it will be here soon. 

Damn that was scary.  I wonder if this prop, with each blade screwed to the spinner plate, could be flown on a 10cc gasser?

Tomorrow I will put the servos in for the rudder and elevator. and the plane will be essentially ready to program and fly. I am thinking of using the two Hitec HS-485HB Carbonite gear servos on those surfaces. They are analog, but I can mix analog and digital servos with the RX3 Receiver. I am still considering just using the mini-servos, but not if I am going to be drawing that kinda wattage at anytime during the flight. The ailerons can handle it, but the tail feathers will need some oomph. I also want to install the 6V 5A voltage regulator tomorrow.

I was cleaning the underside of the wing when I realized the painted on graphics were smearing. Damn. 

It would be great if the new prop arrived tomorrow, but I think another day before it does.

VQ Models Maiden Flight Ready!

I installed the new prop on the VQM P-51B, and ran a quick test, she stayed together. Today I ran her a bit longer and did some static thrust testing.

She is about 8 lbs AUW, and using the 14" 4-blade prop with a 6S she is producing 1200W at 52A with 12 lbs of static thrust at full throttle.

This is a nice plane, but there are a couple of things that bug me. One is that the coat is rubbery, and low temp, so in the warm air it sags. I suspect this will really suck out in the sun. The second is that to change the battery the wings have to come off. 

Those two holes are where the wing bolts go. The tend to miss the hole inside and flop about the pseudo-air ram. It takes a lot of time to fish them out and try again, a process that takes several tries.

The battery compartment. Fits the 6S 4500 mAh battery fine.

I stuck rubber washers on the ends of the screws so all I need is a screwdriver and they should otherwise stay put between changes. All she needs now is for me to try and fly her.

We flew rockets today, and I caught some video from my Alpha Sport 450 and a keychain camera. An hour of that and I am pretty much done for the day.

Oh, please, you would if you could!

It called to me...

Yeah. 4 blade 14x8x4, baby. She was flying a 13x8x3.

You know you would too, if you could. You know it. Especially you, Gary Hoffman.

I am not sure how it will work, but I will run it tomorrow. Its a prop from an electric FMS P-51 Mustang. I had flown it on the doomed VQ Models P-51. Same spinner, new blades. It was on the shelf. I had to. I had no choice. I honestly don't even know if the blades had enough clearance, especially with the tall grass, but she also had a 14x8 twin blade on her (Master Airscrew Scimitar).

I completed the repair on the side wall. It was still a little weak after the epoxy, so I laid down a thin sheet of balsa. 

I also kept the stabilization system on. I figured out how to set up the remote cut, so the default is OFF. I will take her up and turn it on. I have a feeling it was just too sensitive and was over controlling itself.  I lowered the gains. We'll see, but its an unsolved problem and I need to solve it... Found a couple of tears in the cote on the vertical stab, fixed them too. She is flight ready. I'll try the prop at home, but if weather permits, I'll head out to Joppa in the morning.