Top Flite '.60 size' P-51D Mustang ARF: Building & Modifications
#3126
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Join Date: Dec 2001
Location: Litchfield Park,
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I thought I'd better test out the engine some more before attempting flight and it became immediately apparent that under load the engine would fail instantly. This was because (despite what the HH reps advised me) this engine (Evolution 15cc) does need muffler pressure. The vent line to the atmosphere is not sufficient. So I took the presure nipple off my stock muffler and tapped a new hole in the Pitts style wrap around muffler, reworked the vent line to that and bingo! All Good. Previously as soon as I held the plane striaght up at near full throttle the engine died. Now it was good.
#3127
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Having had a similar dilemma regarding placing a 4 blade prop and cowl onto this kit i decided to seek advice from OS as I am installing a 91 4 stroke engine into this model. I wrote a email to the support department at OS and had this reply
Hello Tony,
We have no experience using a four-bladed prop on this discontinued OS engine
and cannot offer any recommendations. In truth we do not test or recommend any
props beyond the standard two bladed prop. When someone asks about a
three-bladed prop we tell them to drop down one inch in diameter or one inch in
pitch from what is recommended in the engine's manual. We would not hazard a
guess on a four-bladed unit.
Art
Product Support
not much help so am stuck on getting a decent 4 blade prop set up at present any ideas on this. The Biela 4 blader is the one to go for just wonder what size
Hello Tony,
We have no experience using a four-bladed prop on this discontinued OS engine
and cannot offer any recommendations. In truth we do not test or recommend any
props beyond the standard two bladed prop. When someone asks about a
three-bladed prop we tell them to drop down one inch in diameter or one inch in
pitch from what is recommended in the engine's manual. We would not hazard a
guess on a four-bladed unit.
Art
Product Support
not much help so am stuck on getting a decent 4 blade prop set up at present any ideas on this. The Biela 4 blader is the one to go for just wonder what size
#3128
My Feedback: (3)
As you add more blades to the prop the load increases while the efficiency decreases. The purpose of adding blades to an engine is to help keep the diameter to the minimum while applying the power to the air. For warbirds in the 30's and 40's the ground clearance was a big issue. The Corsair is a prime example of form following function. The bent wing is compensation for the enormous prop diameter of 14 feet and 2000hp. Otherwise the landing gear would have to be double its length and fragile for carrier duty.
In RC the engines dont put out the kind of power to make use of a scale diameter prop. In order to use a 4 blade at about 3200rpm like full scale Mustangs do you would have to use gear reduction, or change to electric power and use a larger than necessary brushless out runner motor. You need more torque not RPM. Even the Merlin engine has a gear reduction drive on the front of the engine to take 6000rpm and turn it into torque at half the RPM.
RC engines make more power per pound than any other but they do it at very high RPM. APC designed 4 blade props many years ago for nitro engines but if you look closely at the design the blades are very thin. That's because at higher RPM the blades lose efficiency.
So for you to acheive the scale result your looking for you will have to invest in making a reduction drive for the OS 91FS or another much more powerfull engine like an OS 160 or a DLE 20RA gas engine. Or, change to brushless power because outrunner motors create immense torque throughout their RPM range. You can use an oversized motor just to drive a scale prop with high pitch.
Also take a look at Vario Prop because they make adjustable pitch props for electric applications, nitro and gas engines. It takes a little bit to read the site and understand their system and application but its pretty simple. You can adjust the pitch to the best load for the electric system or engine. Its a fixed pitch set on the ground not in flight. They make 2,3,4,5 blade props and I own a few, 3,4,5 blade props.
FYI, there is a guy who has already made 2:1 reduction drives for 1/5 warbirds and has a video of a YA P-40 using a scale 3 blade running a typical engine.
In RC the engines dont put out the kind of power to make use of a scale diameter prop. In order to use a 4 blade at about 3200rpm like full scale Mustangs do you would have to use gear reduction, or change to electric power and use a larger than necessary brushless out runner motor. You need more torque not RPM. Even the Merlin engine has a gear reduction drive on the front of the engine to take 6000rpm and turn it into torque at half the RPM.
RC engines make more power per pound than any other but they do it at very high RPM. APC designed 4 blade props many years ago for nitro engines but if you look closely at the design the blades are very thin. That's because at higher RPM the blades lose efficiency.
So for you to acheive the scale result your looking for you will have to invest in making a reduction drive for the OS 91FS or another much more powerfull engine like an OS 160 or a DLE 20RA gas engine. Or, change to brushless power because outrunner motors create immense torque throughout their RPM range. You can use an oversized motor just to drive a scale prop with high pitch.
Also take a look at Vario Prop because they make adjustable pitch props for electric applications, nitro and gas engines. It takes a little bit to read the site and understand their system and application but its pretty simple. You can adjust the pitch to the best load for the electric system or engine. Its a fixed pitch set on the ground not in flight. They make 2,3,4,5 blade props and I own a few, 3,4,5 blade props.
FYI, there is a guy who has already made 2:1 reduction drives for 1/5 warbirds and has a video of a YA P-40 using a scale 3 blade running a typical engine.
#3129
I have a DLE 20 in mine and its more than enough power. Turning a 16-8 Master Airscrew prop at about 8,200 rpm or so. I got a Biela 16-8 four blade prop at a garage sale for next to nothing. I got a new plastic spinner and cut it for a 4 blade. Looks really great for static display. I ran the engine with it thinking I had so much power I could loose some and it would still be ok. Didn't work. Only turned about 4,400 rpm. Max power out put for this engine I think is at about 8,000-8,500 fpm. Didn't dare try to fly it. Now that I think about it, it had twice the blades of the 16-8 two blade and half the rpm. A DLE 20 will turn a Master Airscrew 16-8 three blade about 7,200 rpm and is plenty of power for a 65" to 71" wingspan warbird 11 to 12.5 lbs. A 14-7 four blade might work with a DLE 20, don't know, but it would look too small. Also the DLE 20 puts out more power than an OS 120 FS so its just not going to work for you 91FS. Now if you went to a 26 RCGF, or something like that it might? work, maybe a 15-7 which I think Biela makes. But I had to put both batteries back just in front of the tail wheel to balance with the DLE 20 and a 26 would be heavier. My RCGF turns the same 16-8 three blade 8,250 rpm. About 1,000 rpm more than the 20. Maybe I'll put the 16-8 4 blade on the 26 just to see what it will do. Also a gas engine over proped and loaded down will run hotter and require a much richer mixture. Ask me how I know.
#3130
Simple answer, when running all you see is a spinning disk, so fly it on the best 2 blade for the engine, and for display put the 4 blade on. Probably not the answer you are looking for, but unless you know how to make gears, and build a reduction drive, 3:1, the 4 blade will never get the plane off the ground.
#3132
Senior Member
My Feedback: (26)
4
Your getting misleading information on using a 4 bladed propeller. Go over to RCGroups if you disbelieve me. Of course you need the right engine and a YS 170 or 180 is the power plant of choice. I tried a Brelia 4 bladed prop on an OS 1.08 and it was too much for the engine.
Your getting misleading information on using a 4 bladed propeller. Go over to RCGroups if you disbelieve me. Of course you need the right engine and a YS 170 or 180 is the power plant of choice. I tried a Brelia 4 bladed prop on an OS 1.08 and it was too much for the engine.
Last edited by flycatch; 05-31-2015 at 02:12 PM.
#3133
In RC the engines dont put out the kind of power to make use of a scale diameter prop. In order to use a 4 blade at about 3200rpm like full scale Mustangs do you would have to use gear reduction, or change to electric power and use a larger than necessary brushless out runner motor. You need more torque not RPM. Even the Merlin engine has a gear reduction drive on the front of the engine to take 6000rpm and turn it into torque at half the RPM.
General characteristics
- Type: 12-cylinder, supercharged, liquid-cooled, 60° "Vee", piston aircraft engine.
- Bore: 5.4 in (137 mm)
- Stroke: 6.0 in (152 mm)
- Displacement: 1,647 cu in (27 L)
- Length: 88.7 in (225 cm)
- Width: 30.8 in (78 cm)
- Height: 40 in (102 cm)
- Dry weight: 1,640 lb (744 kg)[SUP][nb 15][/SUP]
- Valvetrain: Overhead camshaft, two intake and two exhaust valves per cylinder, sodium-cooled exhaust valve stems.
- Supercharger: Two-speed, two-stage. Boost pressure automatically linked to the throttle, coolant-air aftercooler between the second stage and the engine.
- Fuel system: Twin-choke updraught Rolls-Royce/S.U. carburettor with automatic mixture control. Twin independent fuel pumps.
- Fuel type: 100/130 Octane petrol.
- Oil system: Dry sump with one pressure pump and two scavenge pumps.
- Cooling system: 70% water and 30% ethylene glycol coolant mixture, pressurised. Supercharger intercooler system entirely separate from main cooling system.[SUP][85][/SUP]
- Reduction gear: 0.42:1
- Power output: * 1,290 hp (962 kW) at 3,000 rpm at take-off.
- 1,565 hp (1,167 kW) at 3,000 rpm at 12,250 ft (3,740 m, MS gear)[SUP][nb 16][/SUP]
- 1,580 hp (1,178 kW) at 3,000 rpm at 23,500 ft (7,200 m, FS gear)
Last edited by Hydro Junkie; 05-31-2015 at 03:27 PM.
#3134
My Feedback: (3)
Right, I got the numbers crossed up but as stated in my post, the Merlin has gear reduction to produce torque. Its true about the prop tips going super sonic but they design to a balance between that point and diameter for clearance and number of blades to absorb the power to turn it into thrust.
Also, gear reduction ratios vary by Merlin/Griffon model type and application.
What a couple guys have done for RC has been about 0.5:1 ratio or greater to really reduce the prop RPM and increase torque. Their final RPM at the prop is roughly 3000-4000 and they can handle the full scale model diameter with only a 55cc DLE or similar small engine.
Thats the final point to this; standard model engines cannot produce sufficient torque to spin true scale props. If they could the prop RPM has to be slower and the pitch higher than normal to achieve the same flight speed.
Also, gear reduction ratios vary by Merlin/Griffon model type and application.
What a couple guys have done for RC has been about 0.5:1 ratio or greater to really reduce the prop RPM and increase torque. Their final RPM at the prop is roughly 3000-4000 and they can handle the full scale model diameter with only a 55cc DLE or similar small engine.
Thats the final point to this; standard model engines cannot produce sufficient torque to spin true scale props. If they could the prop RPM has to be slower and the pitch higher than normal to achieve the same flight speed.
#3135
My Feedback: (3)
http://youtu.be/pBA8bxQQhgQ
Link to JGM Designs PSRU test flight video.
Here he shows an MVVS 45 / Evolution engine turning a much larger 24in three blade prop at a ratio of 1.6:1. So again, high rpm motor with a reduction drive to turn a scale prop with authority. Normally this engine could not fly this plane nearly as well and would use a much smaller two blade prop.
Check out his other videos, pretty nice machined parts.
Link to JGM Designs PSRU test flight video.
Here he shows an MVVS 45 / Evolution engine turning a much larger 24in three blade prop at a ratio of 1.6:1. So again, high rpm motor with a reduction drive to turn a scale prop with authority. Normally this engine could not fly this plane nearly as well and would use a much smaller two blade prop.
Check out his other videos, pretty nice machined parts.
#3136
Well I finally got to maiden this little beauty, but it wasn't all plain sailing!
Once again my 15cc gas engine was not behaving itself, but I finally managed to tune it so that it kept going at full throttle when I pointed it straight up. Subsequently discovered that my pressurised vent to the muffler had split and came off.
But my greatest concern was the COG, I was WAAAAY too nose heavy at 143mm back from the LE at the fuse, my CG was like a good inch in front of this. I had moved both my ignition & receiver batts back as far as possible, and I stuck 30gms of lead near the tail wheel, still an inch out and really nose heavy.
Anyway, taxing and take-off was all good, but once in the air the plane did a pretty good impersonation of a rocket and just headed for the heavens, it took a lot, I mean a real lot, of down elevator to get it flying level, and then lots of rudder and aileron trim to get it flying straight.
Now, in all this tuning and trimming I forgot how long the engine had been running and sure enough, splutter splutter DEAD STICK!! I hadn't even had time to check out stall tendencies. Oh well here goes..... now there was a solid westerly breeze going straight down the runway, and our runway slopes west to east, unfortunately I was up the westerly side when it conked out and was headed for a down hill landing with a strong breeze behind me. The plane passed me going over 100kph and I was in the middle of our 300yard strip, I finally got it down with 25 yards left for the hottest landing ever.
Not a scratch to the airframe but one retract bent and snapped at the base, but stayed in place and the other just spun around, with the grub screws giving out. And thanks to the advice I received here the reinforced wing bay where the retracts bolt in were perfectly intact :-)
So a replacement retract and some work on the vent line, but guys what's with the CG, is anyone getting their plane to balance at 143mm back?
Cheers,
Once again my 15cc gas engine was not behaving itself, but I finally managed to tune it so that it kept going at full throttle when I pointed it straight up. Subsequently discovered that my pressurised vent to the muffler had split and came off.
But my greatest concern was the COG, I was WAAAAY too nose heavy at 143mm back from the LE at the fuse, my CG was like a good inch in front of this. I had moved both my ignition & receiver batts back as far as possible, and I stuck 30gms of lead near the tail wheel, still an inch out and really nose heavy.
Anyway, taxing and take-off was all good, but once in the air the plane did a pretty good impersonation of a rocket and just headed for the heavens, it took a lot, I mean a real lot, of down elevator to get it flying level, and then lots of rudder and aileron trim to get it flying straight.
Now, in all this tuning and trimming I forgot how long the engine had been running and sure enough, splutter splutter DEAD STICK!! I hadn't even had time to check out stall tendencies. Oh well here goes..... now there was a solid westerly breeze going straight down the runway, and our runway slopes west to east, unfortunately I was up the westerly side when it conked out and was headed for a down hill landing with a strong breeze behind me. The plane passed me going over 100kph and I was in the middle of our 300yard strip, I finally got it down with 25 yards left for the hottest landing ever.
Not a scratch to the airframe but one retract bent and snapped at the base, but stayed in place and the other just spun around, with the grub screws giving out. And thanks to the advice I received here the reinforced wing bay where the retracts bolt in were perfectly intact :-)
So a replacement retract and some work on the vent line, but guys what's with the CG, is anyone getting their plane to balance at 143mm back?
Cheers,
#3141
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I realize this thread is someone inactive for the last few months, but I have a question about the elevators. I have mine installed (not glued) and the left one at the outside edge is "tipped" up and the right one is "tipped" down, the hinges (furthest out) are not centered and cause this. I can remove that CA hinge and align the elevators with the horizontal stab.
I am thinking and can re-slot these hinges and align the elevators and stab, but wondered if this would be overkill and having the ends tipped up or down 1/16 of an inch is a big deal.
Thanks
Justin
I am thinking and can re-slot these hinges and align the elevators and stab, but wondered if this would be overkill and having the ends tipped up or down 1/16 of an inch is a big deal.
Thanks
Justin
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jeep36 (02-10-2021)
#3144
Hey Justin,
If she's not squared and trued, it takes adjustment to make her fly straight and level... No such thing as overkill on a warbird. If you notice a problem on the ground, it won't fix itself in the air.
Build well!
Ben
If she's not squared and trued, it takes adjustment to make her fly straight and level... No such thing as overkill on a warbird. If you notice a problem on the ground, it won't fix itself in the air.
Build well!
Ben
#3148
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It was/is bad. This is my first "ARF" that is not foam. I am building a Dave Platt Zero, almost finished with that, and a Brian Taylor 80" Mark IX Spitfire with a Vic fuse. I am not all that impressed with TopFlite at this point. I replaced the retracts with Hobby King struts, and modified some of the servo and connections. But for the price, it is what it is.
#3149
Join Date: Jan 2010
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pilot bust for top flite ARF mustang
Great threads and information on here about building this kit excellent stuff indeed. some great builds coming along here
I was wondering if anyone can offer some info on where I can get a fully dressed realistic pilot bust for mine? Are there any good suppliers of WWII pilots that would be suitable to fit into this kit.
Will post some pics of my build very soon.
I am running a OS91 in mine and also need to get hold of a pitts style muffler. has anyone fitted one of these engine muffler combos into one of these?
I am also using the eflite retracts and robart struts and wheels
Stripped mine and have re-covered it in chrome monokote. I am going to slightly alter the livery off the normal WWII style paint schemes which may look different than the livery used on the actual planes but it will look ok for sure
I was wondering if anyone can offer some info on where I can get a fully dressed realistic pilot bust for mine? Are there any good suppliers of WWII pilots that would be suitable to fit into this kit.
Will post some pics of my build very soon.
I am running a OS91 in mine and also need to get hold of a pitts style muffler. has anyone fitted one of these engine muffler combos into one of these?
I am also using the eflite retracts and robart struts and wheels
Stripped mine and have re-covered it in chrome monokote. I am going to slightly alter the livery off the normal WWII style paint schemes which may look different than the livery used on the actual planes but it will look ok for sure