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-   -   Gas Powered World Models P51 GS (http://www.rcuniverse.com/forum/scale-racing-183/11061188-gas-powered-world-models-p51-gs.html)

rcpilot32 04-29-2012 07:52 AM

Gas Powered World Models P51 GS
1 Attachment(s)
I have been asked by Don Stegall to do a build thread on the World Models P51 GS. The aircraft I have is the one that is in the Showcase. I picked it up the first Saturday in Feburary from Don. I won't do any photos of the ARF kit laid out since Don has already done that.

I may not assemble it the way other people do it. There are a lot of things I changed from the suggested instructions. I'm not saying the instructions are wrong. There are just ways I like doing things.

For my project, I bought the PTE 36 rear exhaust gas engine. It was a good choice and I would not have to cut out any of the engine cowling except for the bottom.

(note: my spinner is the wrong color and Don told me there would be a dark blue one coming)

First of all, here are a couple of photos of the finished product.
15 pounds 8 ounces without fuel.


BarryReade 04-29-2012 07:59 AM

RE: Gas Powered World Models P51 GS
Wow, Looks great and I am definitely interested in your build thread as all of us have our way of doing things and I know I will pick up more than one better way to do things.

And how does it fly for being a big toad???http://www.rcuniverse.com/forum/js/f...sn/biggrin.gif

rcpilot32 04-29-2012 11:02 AM

RE: Gas Powered World Models P51 GS
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The first thing I did was to study the instructions from front to rear. Since I was going to be converting to a gas engine, I had to decide on what if any changes I was going to make. What servos to us. Where to put the gas tank. I carefully took all of the parts out of the plastic and looked everything over. Don had taken all of the major components out of the plastic to do the photo shots. I had seen the parts uncovered at his place while we were comparing the Miss America to the Yellow version.

After some long thought, I decided I would start on the wing.

The landing gear blocks are already glued in place. I had to purchase 2 Hitec retract servos. The landing gear is held in place by 4 wood screws. Drilling guide holes helped with the screws. The push/pull linkage for the retracts just screw in place. The servos go in from the top of the wing. Servo blocks are already in place. I highly recommend using extra glue in the wood area because one of the blocks came loose while I was adjusting the servo travel. Drilled guide holes for the servos. A string is glued in the wing from the factory. It is used to tie to the servo lead and pull it thru the wing. Those were the easy parts. The hard part was getting the linkage correct for the retracts. With a lot of trial and error, I managed to get the retracts working properly. Using a "Y" harness and connected to the retract channel.

The flap and aileron servos mount to a removable hatch with 4 screws. Supplied are balsa blocks that glue to the plywood plate to mount the servos. I did not like putting the servos screwed into just balsa. I took the time and cut 8 pieces of plyood and glued them to the mounting serface of the balsa. Then I glued the blocks to the plywood. I felt that more strength was needed.

Once again, I used the strings to pull the servo leads to the center of the wing. Just for safety, I used servo lead keepers to make sure the servo extension did not come apart. No extensions were needed for the flap servos.

I did not like the servo pushrods that came with the kit. By using a gas engine, I felt that there was a need for something larger. I used ball linkage and 4-40 pushrods. After some adjusting, the servos were working.

The wing comes in 2 pieces with 2 aluminum center tubes. There is a bracket that is used to hold the wing halves together. I am using the factory supplied pieces so far, but may do something different in the future. Possibly glueing the wing halves together. It would make the wing more difficult to carry if you don't have a lot of room. I'm still deciding.

That's the wing for now. Comments appreciated.

rcpilot32 04-30-2012 05:08 AM

RE: Gas Powered World Models P51 GS
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Sitting the wing aside, I now decided to install the eleverator servos. Using a very sharp knife, I cut out the servo holes. This is an option. The kit comes with a pull/pull assembly that mounts in the tail to provide twin eleverator controls. Because I was using the gas engine, I chose to use dual eleverator servos. I also used the heavy ball links and 4-40 pushrods.

Since I was using the twin servos, I chose to use an extension with a servo reverser. Now I had the lead going to the receiver. When the formers were cut out, they made holes in the top of the fuselage. It worked out great. I could barely get my arm inside to thread the wire in the holes. I didn't like the wires just lying against the wood. Vibration would eventually cut thru the wires. So I used the coiled wire loom over the wires. Then used small zip ties to secure the loom to the formers. This keeps the servo wire away from the pull/pull elevator cables.

The stab halves fit together by a tube and wooden dowel. The tube and dowel go thru a plywood plate that is glued to secure the stab to the fuse by 2 screws. Just for safety, I used CA to glue the plywood in place. Then mounted the stab halves. After looking at this assembly, I removed the stab and used epoxy and glued the stab halves together. I could see no reason to ever have to remove them.

The elevators are pre-hinged. Added the control horns and made up the elevator linkage. I used the 2 mount screws using blue loctite.

The verticle fin/rudder come as one piece and glue in place. It would be hard to get this out of alignment. Used 5 minute epoxy.

Now for the elevator and rudder servo trays. Simple and easy to mount. Used thick CA for this. Extra braces come with the trays. I wasn't going to use the elevator servo tray, but decided it might be a good place to mount the battery or receiver.

Mounted my rudder servo. Put the double horn on the rudder. Cut my rudder cables to equal length. Made up and crimped the cables to the rudder. Threaded the cables to the rudder servo. The cables were too short. I could not use them. I used too much at the rudder horns and come up short. It would have been nice if they had gave me an inch longer per cable. So beware. Make the cables as short as you can. You cannot use the elevator cables because they are shorter than the rudder. I happen to have a set of cables that were the same size.

Instead of using the supplied z bend cable ends, I chose to again use ball links. Finally, I had working elevators and rudder. Cable adjustments are critical. You don't want them too loose or too tight.

Tail wheel was very easy to install. No problems.

Till next time.

rcpilot32 05-01-2012 04:02 PM

RE: Gas Powered World Models P51 GS
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This step will be the mounting of the engine. Before I glued the verticle fin and rudder in place, I stood the fuse on the tail so I could sit the engine in place. I centered it on the stands and marked the spots with a red pen. It was difficult to hold the fuse and engine while seeing if the top engine cowling would fit properly and have clearance for the spinner back plate. To my surprise, it was just right. There are pieces of wood that stop the top cowling. I was possibly lucky. I made sure the engine was in the center of the firewall. Lucky again. I had marked the engine stand offs in the center of the firewall.

Using a sharp thin punch, I marked the drill spots. Then drilled 4 1/16th guide hole in the firewall. Then drilled the larger holes for the engine stand screws. Only had to use a round file slightly for the engine mounts. Was very proud of myself. Put 2 screws in and rechecked the top engine cowl. Good fit. Next, I marked the spot to drill for the throttle pushrod. Removed the engine, drilled the hole and installed the plastic tube for the throttle.

I used a ball link and Nyrod pushrod. It gave me a smooth operation of the throttle. I didn't like the way that was recommend to mount the throttle servo. I used a block of balsa, with light plywood to make a servo mount. I dug thru my old items and found a plastic servo tray. It worked just right for the throttle. Linkage is almost straight and it left me with access to the engine screws on the inside.

Here are more photos.

rcpilot32 05-03-2012 09:15 AM

RE: Gas Powered World Models P51 GS
1 Attachment(s)
Here is a photo of my throttle servo installation.

Fuel tank. Now I had to decide what to do with the fuel tank. I didn't want to put it in the nose and the fuse did not have any place to sit the tank. If I glued in plywood, then I would have difficulty getting to the engine mount screws. So I decided to put the fuel tank close to the CG. I used 1/8 light ply 3 inches by 12 inches. Used epoxy to glue it in place. I had some 1/8 sticky back foam that I put under the tank. Then I used 2 pieces of 1/2 inch foam on top of the 1/8 foam. Two long zip ties holds it in place. The foam keeps it from slipping. Connected my filler tube and the inlet fuel tube to the carb.

Behind the fuel tank, I used epoxy on the wood so my sticky back velcro would stick good. This is where I mounted my receiver. RX battery went to the rear under the rudder cables. Ignition battery went forward in front of the fuel tank.

The CG on the instructions call for 6.9 inches back. I used this for my first flight and to me, it was a little tail heavy. Elevator was too sensitive. So I swapped places with the batteries. Put the heavy battery in front of the fuel tank and the light ignition battery under the rudder cables. It put the CG at 5.5 inches from the leading edge. This was where I am more comfortable. Not that other people would like this distance.

I test fit the wing to the fuse and it fit with no problems. Now to finish the engine cowl.

rcpilot32 05-04-2012 06:24 AM

RE: Gas Powered World Models P51 GS
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The upper engine cowl was now ready to put into place. All 3 pieces of the cowl are pre drilled and pieces of plywood are inside the fuselage. The upper cowl comes with a clear plastic cover. It is good to use to fit over the engine for fit. The screws come with silicone washers. I didn't like the way the washers crushed on the cowl so I drilled the holes a little larger for a better fit. The silicone washers have a step on them. When I drilled the small guide hole for the top screws, the drill did not hit the plywood inside the fuselage. Seems the plywood inside was in the wrong location. All I did was cut 2 small pieces of plywood and used thick CA to glue them in place. Then the top cowl screws were secured.

The lower rear cowl goes in place next. 8 screws with silicone washers. There is a problem with the 2 most rear screws. While holding the wing up to connect the servos, the edge of the wing will hit the screws. The silicone washers make the screw heads stick out just enough for the wing to catch them. This causes the screws to break out. The wood blocks are balsa at this point and are easily repaired. I removed the silicone washer and used a flat washer instead. The lower rear cowl doesn't hold any of the load, so it should be OK.

The lower engine cowl will have to be cut for your engine. Since I used the gas engine with rear carb and exhaust, it wasn't very much trouble. Just took my time using my dremel tool with a 1/8 drill bit in it. Very good for cutting fiberglass. Then used a small round sander to smooth the edges. Once in place, I drilled a small guide hole for the remainder of the screws. The fit was very good.

I forgot to mention my ignition module. It fit under the top engine cowl. Making a small hole for the battery lead was just a matter of using aht dremel tool with 1/8 drill pit. Routed out the hole just large enough for go inside the fuse.

rcpilot32 05-08-2012 05:03 PM

RE: Gas Powered World Models P51 GS

I have been asked to list by mfg. the items that I used for the installation.

My flying r/c goes back 44 years. During that time, I have learned to save everything that could possibly be used again. I am retired and have a limited budget for my hobby. So on this Mustang, I used a lot of things. Some that had never been used and some that have been used a lot.

My aileron,elevator, servos are the JR 4721. Flap servos are Hitec HS 625MG. Throttos servo is JRDS 811. Rudder servo is Hitec HS 625 MG.
I had to buy the retract servos. Hitec HS 75BB. This is the first airplane that I have had with retracts in 20 years . All are used except for the retract servos.

I did not like the fuel tank. I'm a little more picky about fuel tanks, so I bought a new Du-Bro 24OZ. Also had to purchase a gas stopper and tygon fuel tube.

My ball links are all Du-Bro heavy. 4-40. Not sure about my clevis. They came with my Great Planes Extra 300. I used ball links and had the clesises left over.

My transmitter is the JR 11 channel. Using a JR 9 chanel RX.

No photos for this post. Next post will be the making of retract servo hatches.


rcpilot32 05-13-2012 05:54 AM

RE: Gas Powered World Models P51 GS
Since this is my first build thread, I knew there were some things that I would possibly miss. A photo of the ignition box and choke control. Also what I did with the wires.

Behind the ignition box at the bulkhead, I routed a hole just large enough to get the battery lead inside the fuselage. I am going to go back and make it a little larger and install an insulator. I feel that the wire just laying there would eventually rub enough and possibly cause the ignition to fail.

I had a hard time deciding how to do the choke control. After a lot of thought, I made a bracket and put it inside the canopy. I use needle nose plyers to push the choke on/off. Works good and you don't have to cut holes in the cowling.

Here are some new photos. My camera is not the best, but this is the best I could do with it.

(It will not let me download the photos. Will try later)

rcpilot32 05-13-2012 02:44 PM

RE: Gas Powered World Models P51 GS
1 Attachment(s)
Here are the photos if they will download.

A6TEXAN 05-18-2012 08:20 PM

RE: Gas Powered World Models P51 GS
very nice job so far James. keep us updated. please post the flight report, as i am very intrested in the PTE 36 engine.
especially in this airframe. ive seen a few with the DLE 30 and always wondered about performance with the 36 after it made its debut.

rcpilot32 05-19-2012 02:17 AM

RE: Gas Powered World Models P51 GS
I am currently working on the retract linkage. With the Z-bend that is supplied with the aircraft, it has a tendency to "turn". When it turns, it hits the wing rib and binds. I will post photos today.

The PTE 36 fits in the cowl very well. I have been at the Joe Nall fly-in in Woodruff, SC 3 days this week. There was a guy from Michigan that had this very same model but had a DLE 55 mounted on it. The lower cowling had to be cut a lot since it was a side exhaust. It wasn't very streamlined. Maybe with a pitts muffler it would have looked nicer.

I got to see him fly it once without any success. The engine would not get to full power. Everytime he would try to throttle up, it would almost quit. Short flight. The next day, he had the cowling off and it still wouldn't get full throttle. After talking with him, he assured me it was very fast.

Once I get the retract linkage solved, and the plane flying again, I will do speed runs just to see how fast it is going. I will also include a full flight report.


rcpilot32 05-19-2012 10:33 AM

RE: Gas Powered World Models P51 GS
1 Attachment(s)
Finally got the retracts working to suit me. It has taken me a long time and many attempts to get it right. I chose to use Hitec HS 75BB retract servos. They travel 180 degrees and cannot be changed. If they can, I could not figure them out. I don't recommend using this servo. Get a retract servo that can adjust the end point. It will make it much easier. I might also suggest that you get a low profile servo. The 75s are bottomed out and can go no lower.

I was going to build plywood hatches to cover the servos but the linkage it too high and would be rubbing the wood. That explains why they send 2 small pieces of covering material to go over the holes. I went to the hobby shop and bought a trim sheet with sticky back. It isn't exactly the same color as the covering. Couldn't find anything exactly the same color. Anyway, the sticky covering can be removed without any problems. Just use a razor blace and get under the edge and you can peel it off. If you iron on the covering, it will be more difficult to get to the servos.

The photos are of the Z bend rod and keeper that comes with the kit. The other photos are what I used. Works well without binding.

It's ready for flying. Will report on that soon.

rcpilot32 05-20-2012 04:39 PM

RE: Gas Powered World Models P51 GS

Flew the P51 this morning. 2 flights of 10 minutes each. Had no problems. Stalls, low passes, loops, 4 and 8 point rolls.
The Mustang does not have blistering speeds with the PTE 36 engine. It is no slow poke. The engine is not fully broken in yet and I am still using the 30 to 1 Penzoil. Soon I will go to the synthetic oil and the engine should have more power.

It flies good, but you have to be careful on landing. A little power is needed to fly it back to the runway expecially with the flaps down. It slows down quickly.

I have the new correct spinner color on it and will post a new photo tomorrow. Soon there will be a video posted on YouTube.

Now I plan on having a lot of fun. Thanks for reading my posts.

rcpilot32 05-25-2012 10:51 AM

RE: Gas Powered World Models P51 GS
1 Attachment(s)
If it will download, here is a new photo of my Mustang with the correct spinner color.

Update: Made several flights today and have decided that the fuel tank in the location I have it will not work. Once the plane slows down with the nose up, the fuel in the tank moves to the rear making it tail heavy on landing. I had to bring it in really hot so it would not tip stall. Due to this problem, I am removing the tank from the current location. Switching back to the tank that came with the kit and putting it in the nose. This should solve the problem.

I made some speed runs today. Average speed is 97 mph. My PTE 36 is breaking in and getting stronger. 7900 rpm with XOAR 18 X 8. Has unlimited verticle. I was hoping the speed would be around 110. I will be trying different props soon.


Photo finally downloaded

BarryReade 06-11-2012 08:23 AM

RE: Gas Powered World Models P51 GS
James, I just reread the thread and it is definitely going to be a big help as I build mine.

rcpilot32 06-11-2012 08:38 AM

RE: Gas Powered World Models P51 GS
After talking with Don Stegall, I have decided that the 18 X 8 prop may not have enough pitch for my PTE 36 eigine. I have ordered a Zoar 18 X 10 and will test with it. It hasn't arrived yet.

I have also moved the fuel tank forward so the CG won't be so sensitive. Will post test results soon. It's raining and will rain for a couple more days.


rcpilot32 06-30-2012 09:59 AM

RE: Gas Powered World Models P51 GS

Sorry to have taken so long to post results.

Got the XOAR 18 X 10 prop. Balanced and installed. I had moved the fuel tank and batteries forward to change the CG.

Although it was hot today, (104) there wasn't anyone else at the field. I had it all to myself. I had test run the engine at home and it was turning
7400 with the new prop. A few flips and it came to life. I taxied out, lined her up, and gave throttle. The tail came up and it tracked straight with
hardly any rudder correction. Smooth liftoff and was climbing steady. Gear up. Building speed. Had to give it 4 clicks of up elevator since I had moved the CG.

Loops, rolls, 4 points, and low fly bys. Finally it is flying great. After about 8 minutes, I started slowing down for landing. Half flaps, gear down, turn final,
then full flaps. Keeping a little throttle. 5 feet high, cut all throttle and it settled down on main wheels. Then the tail came down. Tracked straight and rolled to a stop.
I was pleased.

After a cool down, (me and the plane), I gassed it up and flew again. Used half flaps for take off. For landing, I didn't use any flaps just to see how it would do.
Naturally, it came in a little hotter but without any problems. Made 4 flights and all is well.


I hope to get many happy flights out of this airplane.


Nitro2Burn 07-03-2012 07:34 AM

RE: Gas Powered World Models P51 GS
Hey James, what are the plane specs (wingspan etc), Looks like a pretty sweet machine and depending on specs may prove to be a worthy contender for Reno Unlimited large scale racing here in Australia. Have you tried any high G turns at all? Speed is good but not if I can't turn the corner at the end of the straight, does it show signs of high speed stalls in tight turns is the main thing?

DonStegall 07-03-2012 08:01 AM

RE: Gas Powered World Models P51 GS
James will have to address the turning characteristics, but I can give you info on the plane and the specs we have for the proposed racing class.

Go to [link=http://www.abmshowcase.com/the_world_models/warbird/p51gs/default.aspx]P-51 Mustang G.S.[/link] and look at things like the [link=http://www.abmshowcase.com/the_world_models/warbird/p51gs/models/rockwell/photos/default.aspx]P-51 Mustang G.S. - Rockwell Kit Pictures[/link] for some details.

Go to [link=http://www.rcpro.org/content/rcpro/p51gs/rules/default.aspx]RCPRO P-51 Giant Scale Racing - Rules[/link] for the proposed rules. Note that the 660' course has been ruled out and I need to take it off the page.

James did a great job of sticking with the plane through some challenges. He is a great modeler. He perseveres when the going is tough. The PTE36R engine that he got was kind of a challenge and also the CG as shown in the instructions seems to be off significantly.

rcpilot32 07-03-2012 08:38 AM

RE: Gas Powered World Models P51 GS

Nitro2Burn, thanks for your interest.

Once I got a CG that I was comfortable with, the flight characteristics were very good. I made many pylon style turns and it had no snap out tendencies. Before I got the right CG,
It would snap out with just slightly high G turns. It would snap out on loops. Now it does not.

This Mustang was a challenge, but I was determined to find it's potential. I must say that I am disappointed with the power output of the PTE 36. By changing the prop to the
XOAR 18 X 10, I did get more speed. The engine sounds cool on a dive hearing the rpm get to the max. I only have around 2 gallons run thru it. It may just be one of those
engines that takes 4 to 5 gallons to break in completely.

Landings are now easy with or without flaps. The retracts are not stiff enough for the airplane. I check them after each landing to make sure they are not binding in the wheel wells.


Nitro2Burn 07-12-2012 05:29 PM

RE: Gas Powered World Models P51 GS
Hey Don and James,
Thanks for the info guys it definately is a sweet looking machine, biggest downside for me is here in Australia we have a minimum 84" span and a minimum wieght of 10.9kg (24lb) for Reno Unlimited which puts it 3.5" to short on the wingspan [:o]
I could always work on making it heavier, plus by the time you added something like a DLE55 or a DA60 to the nose 24lb would come around pretty quickly. At the moment I have a Top Flite GS P40 that is very competitive however one can't get complacent and should be always looking for something faster right?
The RCPRO P51 class looks like awesome fun, something the new DLE35 rear carb and rear exhaust would go well in I feel.
James thanks for the corner info also, is amazing what a slight COG change can do for performance.


DonStegall 07-28-2012 09:21 AM

RE: Gas Powered World Models P51 GS
Here is video of James' P-51 Miss America. Nice flight.



cjbotox 10-24-2012 04:53 AM

RE: Gas Powered World Models P51 GS
Great flying James! To me the fly-bys look pretty darn fast for a plane this size. I have talked with Don about some questions and he answered most of them and gave me a lot of good advice. I know he's a busy man so I'd like to resubmit some questions to you. BTW, great build threads going on here between you and Don!

<span style="font-size: larger;">As for balancing, what do you use? Can I use fingers? I DON'T want to spend $100.00 on an EZ balancer that I'll only use a couple times. And no, my friends are all flying electric stuff so I don't know anyone I could borrow something for a 15 lb.+ airplane. </span>

You mentioned finding a 'better' C of G point for sharp turns, would you mind sharing... very important to me as I have buried some planes I tried around the pylons.

I've posted the basics I'm using in his thread, but he mentioned using better retract servos which have me wondering. I understand the standard retracts are analogue and have no ability to set end points, so should I just plan on investing in spring airs? I like to keep wieght down and keep the supplied ones.


rcpilot32 10-24-2012 06:27 AM

RE: Gas Powered World Models P51 GS
I first started off with the CG at the recommended point. It has a snap-roll tendency at this point. I moved it to 5.5 inches from the most forward point of the wing. The Mustang is happy at this point. I can do very sharp turns with no problems.

I used the supplied retracts and the HS 75 analog retract servo. It really sucks. Go with the servo that Don suggested. After many different adjustments, I have mine working the way they should. The gear is weak and bends very easily. If you can afford them, go with the spring airs. Each time I land, I inspect the wheels to make sure they are not binding in the wheel wells.

I have not posted on this thread for over 3 months. Having serious engine problems with the PTE 36. I am currently waiting on the factory to send me a PTE 36 II. An updated version of the engine.
In the future, I plan on posting my comments on the engine. (good or bad) I was told a couple of days ago that the engine will be sent to me soon. I was also told to have patience. My patience is running very short. More to come soon.

If you have any more questions, I will be glad to answer as best as I can.


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