Engine for Nobler ARF

[Colin McRae]

I recently came across an old Top Flite Nobler ARF, however, it needs a bit of tender loving care to get it in the air. My question is if an OS Max 30 (excellent condition engine) will pull it around the circle.

[Ken Culbertson]

I recently came across an old Top Flite Nobler ARF, however, it needs a bit of tender loving care to get it in the air. My question is if an OS Max 30 (excellent condition engine) will pull it around the circle.

With gusto unless it is heavy which most of them are not.

Ken

[Dan McEntee]

I recently came across an old Top Flite Nobler ARF, however, it needs a bit of tender loving care to get it in the air. My question is if an OS Max 30 (excellent condition engine) will pull it around the circle.

    No harm in trying it. If it doesn't have quite enough poop for you, and OS .35S will drop right in it's place.
  Type at you later,
  Dan McEntee

[Colin McRae]

Thanks

The other engines I have available are an OS 40 LA and also an FP. I had the 40 FP on a SIG Banshee, and it was too much engine for that model, so I switched to an OS Max 30s which seems to be a good size for the Banshee. The Nobler ARF seems quite light so the 30s should be fine.

[Air Ministry .]

I had a 30 in a 43 Oz Gieske Nobler centuries ago . Used the larger of three OS 20 intakes , If I recall right .
10 x 6 Top Flite Nylon . I think the timings lower than a 35 , so is good in the 4 stroke - keeps on keeping on .

HOWEVER , the BALANCE is the THING . I needed 1/4 Oz/ lead aft with the silencer ( 703 ) . So likely your good
where youd need five ton aft with the FP's . Which are 1/3rd heavier .

MOST people'd put the LA 46 in , maybe with a little toungue muffler , weight wise .

As theyre all about the same bolt fit , the shorter 30 nose is the only thing there . Maybe set the FP / LA right back .

Mark C G & rubber  band fit & check , before drilling . Two sets of holes with long 1/8 steel mounting pads ?? . maybe .

[Brett Buck]

Thanks

The other engines I have available are an OS 40 LA and also an FP. I had the 40 FP on a SIG Banshee, and it was too much engine for that model, so I switched to an OS Max 30s which seems to be a good size for the Banshee. The Nobler ARF seems quite light so the 30s should be fine.

     It will be enough for now, at sea level, in cool conditions. I think you will find it a bit lacking as you progress to more complex maneuvers, some of which really suck out the power. One thing you might learn is what "energy management" means in a stunt context.

    Good thing about the ARF, it's pretty easy to change engines to something more capable when/if it becomes necessary. Much easier than the Green Box, because you can get to both sides of the motor mounts.

       Brett

[John Skukalek]

Brett, what are your thoughts on a 25 LA in a Nobler?

[EricV]

I had OS 30 s in a profile Smoothie that was not light as most profiles aren't, and it flew it great. The 30 S was darn near interchangeable with the OS 35 S power wise, maybe a hair less torque, but it swung the same props with ease. Castor and nitro are your friends on hot days, but they will make a friendlier and more consistent power delivery than a stock fox 35. No comparison in my opinion.
EricV

[Colin McRae]

I was able to get my hands on the Top Flite build instructions for the Nobler ARF. It actually says (recommends) to start out with an OS 40 LA engine with 11-4 prop. Since I have a 40 LA available, I will just start with it. I also have the OS stock 7mm (0.275") venturi, and also a 6mm (0.236") one in case some power/fuel management is needed.

[gene poremba]

 Colin, I use an OS 40 La in mine and it works just fine. Im flying it on .015x60' lines...Gene

[Dan McEntee]

I was able to get my hands on the Top Flite build instructions for the Nobler ARF. It actually says (recommends) to start out with an OS 40 LA engine with 11-4 prop. Since I have a 40 LA available, I will just start with it. I also have the OS stock 7mm (0.275") venturi, and also a 6mm (0.236") one in case some power/fuel management is needed.

     I would start with the 6mm venturi. I found the biggest problem with the Nobler ARF was fitting a tank. The fuselage is much narrower than usual. I couldn't get plastic tanks to fit correctly and still give me even runs upright and inverted. I know guys have done it but I don't know what  they used. Another issue is that there is practically no wood in the nose!! It is incredibly weak. The two engine bearers need gussets to support them, and install those after you fit your engine. The engine bearers taper towards the back and so there is no tank floor. I fitted some 3/8" thick balsa blocks with the grain running cross ways to stiffen the nose up and give the tank area a proper floor. I ran those all the way back to the rear former and then coated everything with thinned epoxy. Standard 2" wide tanks won't fit so I wound up making my own. The biggest tank I could make and still get in the compartment was 4 1/4 ounces I think. I put the engine up on 1/16" or 3/32" aluminum pads also. If you use the 6mm venturi a tank this large should be adequate for an LA .40. It will still have plenty of power. I did two this was, one with an OS .35-s and one with a Brodak .40 in it. Both models came out about 43 to 45 ounces. One needed about 1/4 ounce tail weight and I use wood props on them both to help with balance. Both airplanes were started by other builders and never finished and had some issues but for foo foo fun flyer airplanes they do pretty well. The cowlings could be better. If yours is still clean, I would apply another layer of fiberglass and epoxy to the inside for some more meat to take the abuse of cutting things out and drilling holes. If I build up another one I'll do that also. It's a terrible fit to the fuselage also. Lots of guys build new balsa cowls like the kits had but this glass cowl does have some other advantages when it comes to installing fuel line runs sand servicing things.
  Type at you later,
  Dan McEntee

[Colin McRae]

Colin, I use an OS 40 La in mine and it works just fine. Im flying it on .015x60' lines...Gene

Thanks Gene, that's my plan.

The model was given to me and is a bit beat up. Tail broken, some Monocoat recover needed in areas, strengthen the motor mounts, etc. Relatively minor (headache) stuff. One thing that I am a bit worried about is that I can't tell if the controls (bell crank and lead outs) were ever upgraded as is recommended for these old ARF's. But the model was free, and I'm just going to risk it and fly it for the experience. I am also still learning new pattern stunts and if a crash does come, this is the one for it.

I do have another NIB Top Flite Nobler ARF in my stash of future models and will definitely upgrade that one when the time comes. The experience I gain from this repaired model will surely come in handy with the future ARF build.

[Colin McRae]

     I would start with the 6mm venturi. I found the biggest problem with the Nobler ARF was fitting a tank. The fuselage is much narrower than usual. I couldn't get plastic tanks to fit correctly and still give me even runs upright and inverted. I know guys have done it but I don't know what  they used. Another issue is that there is practically no wood in the nose!! It is incredibly weak. The two engine bearers need gussets to support them, and install those after you fit your engine. The engine bearers taper towards the back and so there is no tank floor. I fitted some 3/8" thick balsa blocks with the grain running cross ways to stiffen the nose up and give the tank area a proper floor. I ran those all the way back to the rear former and then coated everything with thinned epoxy. Standard 2" wide tanks won't fit so I wound up making my own. The biggest tank I could make and still get in the compartment was 4 1/4 ounces I think. I put the engine up on 1/16" or 3/32" aluminum pads also. If you use the 6mm venturi a tank this large should be adequate for an LA .40. It will still have plenty of power. I did two this was, one with an OS .35-s and one with a Brodak .40 in it. Both models came out about 43 to 45 ounces. One needed about 1/4 ounce tail weight and I use wood props on them both to help with balance. Both airplanes were started by other builders and never finished and had some issues but for foo foo fun flyer airplanes they do pretty well. The cowlings could be better. If yours is still clean, I would apply another layer of fiberglass and epoxy to the inside for some more meat to take the abuse of cutting things out and drilling holes. If I build up another one I'll do that also. It's a terrible fit to the fuselage also. Lots of guys build new balsa cowls like the kits had but this glass cowl does have some other advantages when it comes to installing fuel line runs sand servicing things.
  Type at you later,
  Dan McEntee

Thanks, Dan, for the good retrofit recommendations. I have read a lot on what modelers do to make the Nobler ARF model better. I'm just going to do the minimum on this particular model (since it is already a bit beat up) and fly it for the experience. I will certainly build my future Nobler ARF with all the best upgrade recommendations.

[John Carrodus]

Hiya Colin

I messed about with an OS 30 in my Nobler, she flew but I soon got frustrated trying to do some basic tricks. Put an OS 35
in the slot- not sure which model now - has a radio carb wired full throttle. She had flames leaping from the exhaust and left vapor trails in comparison to the 30 That LA 40 on 60 ft 15 thou s/steel will suit well - just fly it like you stole it and enjoy yourself.

[Mike Griffin]

Years ago I put an OS .40LA in a Nobler ARF and it flew very well.

Mike

[Mike Scholtes]

Here's another vote for an LA40 in the ARF Nobler. I did this years ago and it was a good combo. Used APC 11-4 prop. I recall the model came with a custom narrow metal tank, since it is too narrow for the typical modern metal tank. A square-section plastic clunk would also be good, since the height of the tubes leading out of the tank is immaterial. I also gusseted the motor mounts as suggested above, with 1/8 ply triangles from firewall to motor bearers.

[FLOYD CARTER]

I don;t like Fox 35 motors, but that's what everyone uses.  So why not?

[Colin McRae]

I don;t like Fox 35 motors, but that's what everyone uses.  So why not?

I do like the Fox 35 and run it on a couple of models I have for sport flying. It's just the 'death burp' thing I don't personally like for stunt. Maybe it's just me but I like to know consistent power is there when needed.

[Colin McRae]

     It will be enough for now, at sea level, in cool conditions. I think you will find it a bit lacking as you progress to more complex maneuvers, some of which really suck out the power. One thing you might learn is what "energy management" means in a stunt context.

    Good thing about the ARF, it's pretty easy to change engines to something more capable when/if it becomes necessary. Much easier than the Green Box, because you can get to both sides of the motor mounts.

       Brett

Brett, is there a good reference where I could read and benefit from the energy management topic/discussion you reference? Would love (and need to) to learn!

Thanks

[Brett Buck]

Brett, is there a good reference where I could read and benefit from the energy management topic/discussion you reference? Would love (and need to) to learn!

Thanks

    Not really, its a flying skill that you just need to learn. It's about how gentle you need to be on the handle in certain parts of the pattern. For example - with a ARF Nobler and a OS-30s, if you start out the maneuver trying to do "max" corners, the first inside might be great, but you have lost so much speed by that point that the rest of the maneuver sort of falls apart, going slower and slower. and more and more ragged. And expert pilot will be able to predict or feel it and will more-or-less automatically back off, usually by limiting the control pressure to feather in and feather out the control force to minimize the speed loss, to keep that from happening. The really good pilots are feeling it on a second-to-second basis and continually adjusting, making the best of what they happen to have at that instant.

    It's also a critical element in flying in the wind, and if you know what to look for, you can anticipate people getting blown out of their hourglass 5 seconds before it happens

    With a "classic" setup like a 30S with, presumably, a 9-6, once you let it get slowed down, it will not recover. You can see the problem even on takeoff. You release the airplane, and then listen to the engine and feel the controls. That combination will take about a lap and a half to two full laps to reach the final speed and the engine to settle into its level flight "setting". Compare that to say, an competent tuned pipe or electric with a simple governor - it will blast out of there like you fired a JATO bottle on the back of it. You can also feel it as a launcher, it will take one finger to hold on to your proposed system, and you are holding on for dear life with, say, a PA51.

    Same thing happens in the maneuvers, the recovery time for a "classic" setup is VASTLY longer than for a more modern system. So, flying one of those type airplane will teach, or demand, that you learn to be able to sense the thing slowing down and be able to adjust your aggressiveness in the middle of a maneuver, or have enough experience to anticipate it and don't cause a problem in the first place.

   Typically, telling someone, particularly a low-time pilot, what to do or to "back off" is pointless because they can only do the maneuvers one way at best, the way their reflexes have taught them to do it.  They have no real control over it. This is more-or-less true into the expert ranks, to a decreasing degree.

  Note that this is why "classic" systems are no longer competitive, and also why so many people can't see why that is true. Modern systems take far less "fudging" to manage the energy, and you can make a pretty big mistake and it will recover fairly quickly. A Skyray 35 with a Fox, it takes extreme skill to get through a full pattern in any sort of wind, the very same Skyray 35 with a 20FP, you can be much less skilled,  hammer it everywhere,  and it will keep going. Many people do not really understand why you would need to put a pipe PA75 in a 630 square inch airplane, it would "fly fine" with an ST46.

     This is all part of the craft of learning to fly. So get out, fly airplanes, get advice from the better pilots - like your experienced expert flying buddy or his even more experienced world and national champion buddies - and get stick time.   I think the ideas above, while they may make sense to you, may be nearly impossible to actually implement at your current skill level. There's absolutely nothing wrong with that, learning anything is a progression from simple ideas and for stunt, just doing the maneuvers without crashing, to learning to trim, to learning to deal with the wind.

      Brett

[Ken Culbertson]

Collin:

Brett mentioned electric in passing.  It takes years and thousands of flights for the energy management  skills you need to become automatic.  With electric you can focus on flying skills.  A properly setup timer will do the energy management for you as it relates to the motor.  You still have to learn positioning and keeping momentum up in maneuvers.  You can hit corners much harder and still maintain airspeed.  I am saying this because I remember all of the enjoyment I had running IC motors, the smell, the sound, all of it but a I also remember the frustration of not winning a contest because of an overrun and taking attempts when the motor didn't respond to my masterful needle valve settings.  Most all of that goes away with electric.  Gone, you don't have to learn it.   My only point in this rambling is that if I were starting out on the competition PA trail today, I would start with electric.

PS I had an OS35s followed by a OS40LA in my ARF Nobler before replacing it with a Cobra 2820/12.  All three flew the plane great.

Ken

[Colin McRae]

    Not really, its a flying skill that you just need to learn. It's about how gentle you need to be on the handle in certain parts of the pattern. For example - with a ARF Nobler and a OS-30s, if you start out the maneuver trying to do "max" corners, the first inside might be great, but you have lost so much speed by that point that the rest of the maneuver sort of falls apart, going slower and slower. and more and more ragged. And expert pilot will be able to predict or feel it and will more-or-less automatically back off, usually by limiting the control pressure to feather in and feather out the control force to minimize the speed loss, to keep that from happening. The really good pilots are feeling it on a second-to-second basis and continually adjusting, making the best of what they happen to have at that instant.

    It's also a critical element in flying in the wind, and if you know what to look for, you can anticipate people getting blown out of their hourglass 5 seconds before it happens

    With a "classic" setup like a 30S with, presumably, a 9-6, once you let it get slowed down, it will not recover. You can see the problem even on takeoff. You release the airplane, and then listen to the engine and feel the controls. That combination will take about a lap and a half to two full laps to reach the final speed and the engine to settle into its level flight "setting". Compare that to say, an competent tuned pipe or electric with a simple governor - it will blast out of there like you fired a JATO bottle on the back of it. You can also feel it as a launcher, it will take one finger to hold on to your proposed system, and you are holding on for dear life with, say, a PA51.

    Same thing happens in the maneuvers, the recovery time for a "classic" setup is VASTLY longer than for a more modern system. So, flying one of those type airplane will teach, or demand, that you learn to be able to sense the thing slowing down and be able to adjust your aggressiveness in the middle of a maneuver, or have enough experience to anticipate it and don't cause a problem in the first place.

   Typically, telling someone, particularly a low-time pilot, what to do or to "back off" is pointless because they can only do the maneuvers one way at best, the way their reflexes have taught them to do it.  They have no real control over it. This is more-or-less true into the expert ranks, to a decreasing degree.

  Note that this is why "classic" systems are no longer competitive, and also why so many people can't see why that is true. Modern systems take far less "fudging" to manage the energy, and you can make a pretty big mistake and it will recover fairly quickly. A Skyray 35 with a Fox, it takes extreme skill to get through a full pattern in any sort of wind, the very same Skyray 35 with a 20FP, you can be much less skilled,  hammer it everywhere,  and it will keep going. Many people do not really understand why you would need to put a pipe PA75 in a 630 square inch airplane, it would "fly fine" with an ST46.

     This is all part of the craft of learning to fly. So get out, fly airplanes, get advice from the better pilots - like your experienced expert flying buddy or his even more experienced world and national champion buddies - and get stick time.   I think the ideas above, while they may make sense to you, may be nearly impossible to actually implement at your current skill level. There's absolutely nothing wrong with that, learning anything is a progression from simple ideas and for stunt, just doing the maneuvers without crashing, to learning to trim, to learning to deal with the wind.

      Brett

Thanks Brett and I do basically now understand the concepts you laid out to me above. I think I have even experienced it a bit. On some of my models, the 1st corner seems OK, but the subsequent corners are not so great.

And on the Nobler, I am just going to go right to an OS 40LA which I already have. I was more or less just curious on the OS Max 30s since I have one of those too.

And the Top Flite Nobler ARF build instructions also recommend the 40LA to start. The 40 LA will be stock except for a shtterman Enya type front NVA and smaller 6mm (0.236") venturi. I also have the OS 40LA stock 7mm (0.275") venturi if needed.

[Colin McRae]

Collin:

Brett mentioned electric in passing.  It takes years and thousands of flights for the energy management  skills you need to become automatic.  With electric you can focus on flying skills.  A properly setup timer will do the energy management for you as it relates to the motor.  You still have to learn positioning and keeping momentum up in maneuvers.  You can hit corners much harder and still maintain airspeed.  I am saying this because I remember all of the enjoyment I had running IC motors, the smell, the sound, all of it but a I also remember the frustration of not winning a contest because of an overrun and taking attempts when the motor didn't respond to my masterful needle valve settings.  Most all of that goes away with electric.  Gone, you don't have to learn it.   My only point in this rambling is that if I were starting out on the competition PA trail today, I would start with electric.

PS I had an OS35s followed by a OS40LA in my ARF Nobler before replacing it with a Cobra 2820/12.  All three flew the plane great.

Ken

I appreciate the insight and thanks. At this stage of my life, I'm probably not going to do much serious competition. I just want to enjoy the CL experience and learn all I can. And that will all take time. And I don't have plans to switch to electric. I really enjoy the IC experience and my engines run better and better all the time. Mayne it's the mechanical engineer in me, buy I need pistons and crankshafts to power by models.

[Brett Buck]

Thanks Brett and I do basically now understand the concepts you laid out to me above. I think I have even experienced it a bit. On some of my models, the 1st corner seems OK, but the subsequent corners are not so great.

   I am glad it helped. I do caution a bit that knowing something, and actually being able to do something about it, are two different things.

   On your "great first corner" issue, the power is only one possible cause and not nearly the most likely. Far more likely, there are *trim* issues that cause the airplane to get "upset" and then not recover before the next corner comes along. You can only diagnose something as a power problem when it is the *only* problem, and without having seen you fly too much, but watching lots of others, I can almost guarantee that you have significant to crippling trim issues. Because so does almost everyone else.

    Again, internet diagnosis is great, but I think you have routine access to a legitimate expert pilot and can certainly come fly with some others whenever we go. Most people do not have that. Take full advantage of it, it's much better than trying to guess from internet posts, even if they are good guesses. 

      Brett

[Ken Culbertson]

 

I appreciate the insight and thanks. At this stage of my life, I'm probably not going to do much serious competition. I just want to enjoy the CL experience and learn all I can. And that will all take time. And I don't have plans to switch to electric. I really enjoy the IC experience and my engines run better and better all the time. Mayne it's the mechanical engineer in me, buy I need pistons and crankshafts to power by models.

No problem.  I still love IC too.  I just don't have time to mess with it anymore.  I need something that I know is going to work on the first flight cause that may be the only one I get.   I love to compete, even if it is only locally for now.  A predominantly electric contest goes so much smoother.  I have a video of a perfect engine run on my OS46LA on a plane I lost in a fire.  I watch it a lot just to hear the sound.   

Ken

[Colin McRae]

I have pretty much been using OS LA engines including 15 thru 46 sizes on my models. Once you learn how to run them, and run them stock, they are pretty flawless for basic stunt CL.

I participated in my first local stunt competition last summer in beginner class. Was a bit nervous but it was actually quite fun and an enjoyable experience. I plan to do more of it in the future.

The way I look at stunt competition is not necessarily to win an event, but just to keep improving my scores. I liken it to the days I ran high school track in Hawaii. As long as I was improving timewise week to week at my various events, I considered it a success and was happy. The same thing goes for my model building and trimming. As long as each model I build, or repair gets better and better it is a success story for me.

And concerning IC engines, at the same local competition last summer, I had the pleasure of watching Dave Fitsgerald beat all the 'electric guys' with his Thundergazer/piped PA 75. Quite a treat.

[Brett Buck]

And concerning IC engines, at the same local competition last summer, I had the pleasure of watching Dave Fitsgerald beat all the 'electric guys' with his Thundergazer/piped PA 75. Quite a treat.

   While I have an IC engine, I have decidedly mixed feelings about that result.

     Brett

[John Rist]

And concerning IC engines, at the same local competition last summer, I had the pleasure of watching Dave Fitsgerald beat all the 'electric guys' with his Thundergazer/piped PA 75. Quite a treat.

Done well both electric and IC will score high.  Both types have a person's hand on the control handle.  That hand is controlled by a brain.  That brain must know how to make the power source and airplane work.  So it is the person's total skill not the power source that creates a winner.  My back ground is electronics so I prefer electric.  The best two fliers in our club prefer IC.  They can fly the full pattern and I just hack around and have fun.  So in my mind it's not the power source but the person behind the handle and there background in life that determines a winner.

[Brett Buck]

Done well both electric and IC will score high.  Both types have a person's hand on the control handle.  That hand is controlled by a brain.  That brain must know how to make the power source and airplane work.  So it is the person's total skill not the power source that creates a winner.  My back ground is electronics so I prefer electric.  The best two fliers in our club prefer IC.  They can fly the full pattern and I just hack around and have fun.  So in my mind it's not the power source but the person behind the handle and there background in life that determines a winner.

      "IC" covers a lot of ground, some of which is still marginally competitive in the most expert hands, but mostly hopelessly obsolete. Certainly the knowledge, skill, and experience of the pilot is a critical factor - but one of those skills is evaluating what sort of equipment to use to maximize your success. In very many cases, even among the most skilled, it is mastery of the technical aspects is a crucial or deciding factor.

    As always, I have no objection whatsoever to people enjoying model airplanes however they want. No one is curing cancer here, it's all for fun. But I have been very frustrated over the years seeing people struggle (and somehow think that they are physically incapable of getting much better) with engines, in particular, that were far superceded, in the most dramatic way possible, *** 40 years ago ***. No amount of practice, knowledge, or skill by the greatest physical specimens on Earth will make your Fox 35 Nobler any better.

    I would add, just because someone is low-time or a beginner doesn't mean they should use completely obsolete equipment or techniques - they need far more help than experts. Stunt, even at the best of times, is a challenge, that is why we all like it, but most people make it far harder on themselves than it needs to be.

    Here's a rule of thumb that has served me well over the years - if Bob Gieseke couldn't do it, you and I don't stand a chance.

    Brett

[Colin McRae]

   While I have an IC engine, I have decidedly mixed feelings about that result.

     Brett

I must respectfully rephrase!!

I had the pleasure of watching both Brett and Dave's IC-powered models beat out the electric competition.

[Motorman]

Brett, what are your thoughts on a 25 LA in a Nobler?

I saw a video of that combo doing the pattern and my take was the LA25 was basically running almost flat out with little head room on power. The LA25 had aftermarket ABC P/L. A bone stock LA25 wouldn't be my first choice. Brodak 40 would be a good engine for a Nobler.

MM

[Brett Buck]

I saw a video of that combo doing the pattern and my take was the LA25 was basically running almost flat out with little head room on power. The LA25 had aftermarket ABC P/L. A bone stock LA25 wouldn't be my first choice. Brodak 40 would be a good engine for a Nobler.

     More-or-less agreed, the original "old" 25LA, no chance. A 20FP would be about the same. **Stock** "new 25LA, maybe, but you are going to be running 4.5-5" of pitch to keep the RPM in range. "Aftermarket", I have no idea, depending on how it was, er, "improved".

     My choice would be a 25FP, abundant to excessive power and able to run 4" of pitch, if you can adjust the venturi small enough. Pat Johnston's was very fast even with a  greatly reduced venturi, but lack of power was absolutely no problem. Certainly more effective than a Fox 35 (which would work OK, about as well as it ever did - not my accident did it win all those contests) and much less fussy, certainly more effective than an OS-30S.

     The 40LA is a fine choice, and getting smaller venturis is certainly warranted because it is very much overkill for a Nobler. Set up correctly (and no, I have *no* experience with it and don't know for sure how to set it up) it should permit much faster recovery from errors and ham-handedness, which is critically important for beginners and low-time pilots. And, importantly, he already has one of those.

    This is one of those deals where perfection could be the enemy of good enough

     Brett

[Colin McRae]

Just thought of this option.

I also have an OS 40 FP (ABN version) in my stash. It also can use the OS 6 or 7mm venturi. But it is my understanding that the FP might be a bit more powerful.

Does anyone know if this is true? How does the 40 FP & LA compare power wise for a stunt application?

Thanks

[Brett Buck]

Just thought of this option.

I also have an OS 40 FP (ABN version) in my stash. It also can use the OS 6 or 7mm venturi. But it is my understanding that the FP might be a bit more powerful.

Does anyone know if this is true? How does the 40 FP & LA compare power wise for a stunt application?

Thanks

    The 40FP is more powerful, but that’s the last thing you need. The 40LA is known to be much more tractable for stunt, and it still far more powerful than you need.

      Brett

[Colin McRae]

I completed the repairs on the Top Flite Nobler ARF. Model is coming in at 47 oz with everything mounted (w/ OS 40LA engine).

My next question is CG. I have a copy of the build Nobler instructions and it mentions a starting point CG of 2.5" from the wing LE at the fuselage. Based on others flight experience with a Nobler ARF, does this location work out OK, or have others found a more optimum CG location?

If I use the instructions stated 2.5" from the LE as the CG point, I will have to add 1.5 oz of lead to the tail to balance that will increase the model weight to 48.5 oz.

Thoughts welcome

Thanks

[Dave_Trible]

That sounds about like I would expect.  Just add the weight.   The stab/elevator is too small on the Nobler to push the CG back very far.  This happens because the airplane was designed for a six ounce Fox .35.  Your OS (with muffler I presume ) is at least 4 ounces more.  You'll have power but you will be pushing the limits on how the airplane flies.   It can still fly well enough for you but would seem pretty sluggish in maneuvering compared to one in the more normal 42-44 ounce range.

Dave

[Colin McRae]

That sounds about like I would expect.  Just add the weight.   The stab/elevator is too small on the Nobler to push the CG back very far.  This happens because the airplane was designed for a six ounce Fox .35.  Your OS (with muffler I presume ) is at least 4 ounces more.  You'll have power but you will be pushing the limits on how the airplane flies.   It can still fly well enough for you but would seem pretty sluggish in maneuvering compared to one in the more normal 42-44 ounce range.

Dave

Thx Dave

That is pretty much what I thought. A good starting point.

The ARF instructions I got a hold of actually recommends an OS 40 LA engine. I know the original model was designed around a Fox 35 due to the age. Maybe Top Flite updated their ARF instructions at some point when a few more modern engines became available.

[Dan McEntee]

Thx Dave

That is pretty much what I thought. A good starting point.

The ARF instructions I got a hold of actually recommends an OS 40 LA engine. I know the original model was designed around a Fox 35 due to the age. Maybe Top Flite updated their ARF instructions at some point when a few more modern engines became available.

      Remember that the Top Flite that put out the green box Nobler was a different Top Flite that put out the ARF Nobler and there are a lot of differences between them even though the look a lot alike. You can probably avoid that excess tail weight, or most of it at least with a few moves. You don't say if you are using the stock muffler on the LA.40. If you are, replace that with a tongue muffler , or if you can find one, a Scott Dinger tube muffler. You will go from about 2.5 ounces for the stock unit to about 1/2 to 3/4 ounces right there. You can also make a decision at this point to use wood props. Wood props are much lighter than their plastic counterparts. It can be as much as 3/4 ounce, depending on the prop. Experiment with what ever you can gather up in the 10-4 and 5 to 11-4 and 5 range. The APC and Thunder Tiger props most guys use are good props and work well, but there is the weight penalty. The tongue muffler will be easiest to find and won't affect the power much at all. You can experiment with drill some extra holes to let it breath a bit better. We are talking about a RTF weight around 45 ounces instead of 48 ounces, and that is a big difference on that airplane and how it will fly and how it will turn.
  Type at you later,
   Dan McEntee

[Ken Culbertson]

I completed the repairs on the Top Flite Nobler ARF. Model is coming in at 47 oz with everything mounted (w/ OS 40LA engine).

My next question is CG. I have a copy of the build Nobler instructions and it mentions a starting point CG of 2.5" from the wing LE at the fuselage. Based on others flight experience with a Nobler ARF, does this location work out OK, or have others found a more optimum CG location?

If I use the instructions stated 2.5" from the LE as the CG point, I will have to add 1.5 oz of lead to the tail to balance that will increase the model weight to 48.5 oz.

Thoughts welcome

Thanks

1 1/2 oz is a lot of extra weight.  Mine weighed the same as yours and I powered it with an OS35s, an LA40 and finally a Cobra 2826.  The only modification was to change the control ratio from 1:1 to 2:3.  CG was at about 2"  A bit nose heavy but it still turned well and was rock solid.  The OS35s had about 500 flights on it and was over 30 years old.  The 40 was about the same as the 35.  One thing that may make a difference is that I used an old Rev-Up 10-6EW.   Hard to find now days.  My point is that it was more than enough power.  I can post a link to a YouTube video of a full pattern on the 35s it if you are interested.

Ken

[Air Ministry .]

Brains been going

NOBLER NOBLER NOBLER
WEIGHT WEIGHT WEIGHT

for the past week . Periodically .

Like a 30 S is LIGHT . Even if the muffler isnt . ( think its 1 1/2 Oz. odd )

All that lot ads up , whereas IF you use the 30 it'd add down . Hopefully .
if your on 60 foot lines and gottit to 43 or 45 even , it'd fly slower o.k. .

tho the liddle FSR 25 will drag 47 ounce , it gets hard pressed covered in grass & grunge . Took two hours with petrol & rag to get three or 4 ounce build up off .
so waxing & polishing wouldnt hurt any , either way . the tiny lite tounge on the La 40 , anyway . Thinning props makes em more fragile , But a stick with 80 Wt
& a few stroke , flip sides ( ends ) so as to keepem even , the balance stays - You smooth under , T E aft - top . strokeing fwd & out , smooth top & radius L E ,
spay with lacquer , same counting trick L & R , ends & hub . stuck on a pencil , stick , or screw driver , to twirl . Fine Paper after a few coats dry . If your fussy .

ANYWAY , you could pull weight out . Lite Plastic spinner etc . Fuel Proof the engine bay tho , or it'll pick up weight there later . Leave most of the stickers off , too .

Gieskes thing was 43 Oz , they said .

uverwise  go longer lines & faster . 64 or 65 ina da calm . Bob they said went by 18 inches on lengths , as it was discernable . But could be 58 handle to fuse. centerline .
18 thou. that long & your o.k. flying in gales . and theres always NITRO . Like 15 or 20 % seems to get a good 4 stroke that works in wind . 10 x 4 three blade on a 35 S is good .
or a 11 x 4 or 5 .

Nobler Noble nobler . weight weight weight . Go Go Go .     

might be threads inthe arf / arc thing on the hot tips for assembly & fine toonin the fits . Will the LA go back away further ? . & still fit

[Brett Buck]

Thx Dave

That is pretty much what I thought. A good starting point.

The ARF instructions I got a hold of actually recommends an OS 40 LA engine. I know the original model was designed around a Fox 35 due to the age. Maybe Top Flite updated their ARF instructions at some point when a few more modern engines became available.

   The ARF is about a Green Box Nobler in many respects, but the ARF showed up *long after* after the 40LA, it was the most obvious option so they showed it. The ARF was never intended to have a Fox, and the hot-melt glue and other aspects are not up to the task of handling the vibration. You could do  it, people have, and they usually stay together, but the original bellcrank has been known to pound itself to bits after as little as 4 flights* with a Fox.

     Dave has it right - balance it where required with lead, don't worry about the weight. Leave the engine alone unless you have some problem. I don't know specifically about the 40LA, but for at least the 20/25FP, 35FP, 25LA, and 46LA, the stock muffler is very important or mandatory for the run quality.   I would also note that the tolerance for CG movement is *tiny*, even a little nose-heavy and the turn becomes hopelessly soft, and even a little tail-heavy and it becomes unstable. This is a function of the tiny tail volume by current standards. Even the difference from beginning of the pattern with fuel and empty at the end is quite extreme.

    2.5" from the root LE sounds like a good starting point, but you will want to high-fi it because you have to split the difference on the CG shift, but even a heavy VS light prop nut is known to make a difference when you get it close.

       Brett

*before someone comes snarling in to say I am lying, this was Heman Lee's (very early) ARF Nobler with dead-stock controls. The Fox vibration pounded out the pushrod hole in the bellcrank to about 1/4" or more diameter in *4 flights*. Heman was flying it and complaining about how hard it was to fly, and getting worse. We cut it open and sure enough the hole was giant and there was black stuff all over the place where the (extremely soft) aluminum turned to dust.

[Colin McRae]

Thx for all the great recommendations.

I will just start with the 2.5" from LE CG location, add necessary tail lead to balance, and fly it. Continued trim will surely be necessary. Concerning the use of a tongue muffler to reduce nose weight, I have tried tongue mufflers on OS LA's in the past and did not like the engine runs. Went back to the OS stock muffler and engine ran much better. So, my direct experience matches Brett's recommendations. Run OS LA engines totally stock for best results.

This particular Nobler ARF model was given to me somewhat beat-up. I did not want to invest too much in it and just wanted to do basic repairs and get in the air. What I learn and trim data from this experience will go into a NIB Nobler ARF kit I have in my stash.

Basic repairs I did:
-Ultracoat recover various areas on the model that were coming off
-Re-glue a few loose flap and elev hinges
-New gap sealing tape on the flaps and elev (model came with simple scotch tape seal. I upgraded to Blenderm tape)
-Fix and straighten the tail and rudder areas. (Model came w/ a broken tail area and broken rudder)
-New Sullivan 4 oz clunk fuel tank and fuel tubing (set up for uniflow with adjustable vent location)
-Added gussets to the motor mounts for some additional strength. This should also help w/ lowering vibration.
-Fix loose tail wheel
-Lighter landing gear wheels

BTW, the model does not have a wing tip weight box and the lead-outs are fixed (not adjustable). There must be some lead in the wing tip as it does fall heavy to the outside. Hopefully enough.

I am aware of the potential for the bellcrank to come loose during flight. I don't know if the original builder upgraded the controls. I did not want to cut into the wing on a beat-up model so accept the risk. This might end up being my 'crash test dummy' Nobler.

On my future Nobler ARF build, I will surely upgrade the controls as recommended by many modelers.

[Colin McRae]

I was able to get in a couple of flights on the repaired Nobler ARF yesterday. (Maiden flights for me)

General data:

-OS 40LA engine. Basic stock engine and muffler except for a smaller 0.257" OS venturi and front NVA from Shtterman. The smaller venturi is the stock one that comes on a 25LA engine.
-11-4 wood XOAR prop
-80# test Spectra lines at 60'
-4 oz Sullivan clunk tank set up for uniflow (Uniflow vent exit in tank approx 1/8" above spray bar centerline)
-Model weight 48.7 oz (this includes added tail weight to CG balance)
-Model does have the rudder offset a bit. Would have to cut into the model to straighten
-Lead outs are not adjustable. Center of lead outs 3/4" behind the CG point
-No wing tip weight box. (Have no idea how much lead in in the wing tip)

Overall, a good experience. With the CG at the kit recommended 2.5" from LE at the fuselage the model flew quite well and level both directions. I did have to add 1.75 oz of lead to the tail to balance at 2.5".

First flight was at a ground rpm of 10,700 (+/- 30 deg rich off of peak). Model flew reasonably fast about 5 sec laps and with a pretty strong pull.

Second flight, needle was opened a bit to a ground rpm of 10,000, still in 2-cycle. Model flew a bit slower, but still with strong pull. I may try 62' or 64' lines. Also try 0.018 SS lines vs Spectra. Also experiment w/ different props. An OS 40LA stock engine is plenty strong for a Nobler! I understand lots of Noblers use a 46LA. (Not sure why-power wise!)

I'm generally happy with the model and not planning to adjust major trim items on this particular model. Just going to incorporate my notes and experience into my future Nobler ARF build. One example is I can probably move the engine back a bit to eliminate the need for tail lead, adjustable lead outs, adjustable wing tip weight box, etc.

I'm also still a long way off from various pattern maneuvers and will fly this model for practice and sport.

[Phil Hawkins]

I have tried 3 different OS MAX-S 30's. All had the same problem. Vibration. Annoying vibration. The first one I figured it must be a bent crank so replaced it with NOS parts... nope still shook through the lines. Bought another new in box .30. Yep, shaker. A guy from So. Africa gave me one, thinking, third times a charm... nope. Sold all three and never looked back. I had them on a Dick Mathis Mongoose. Granted, the Mongoose did not have plywood doubters, but 1/2" balsa cheeks. But putting an FP .35 flew that plane just at the limits of a stunt airplane. The MAX-S .35 was a bit rowdy, I had not yet gotten the 4/2 break figured out.

[Colin McRae]

I have tried 3 different OS MAX-S 30's. All had the same problem. Vibration. Annoying vibration. The first one I figured it must be a bent crank so replaced it with NOS parts... nope still shook through the lines. Bought another new in box .30. Yep, shaker. A guy from So. Africa gave me one, thinking, third times a charm... nope. Sold all three and never looked back. I had them on a Dick Mathis Mongoose. Granted, the Mongoose did not have plywood doubters, but 1/2" balsa cheeks. But putting an FP .35 flew that plane just at the limits of a stunt airplane. The MAX-S .35 was a bit rowdy, I had not yet gotten the 4/2 break figured out.

Interesting

I have an OS Max S30s on a SIG Banshee and don't notice any undue vibration. I also carefully balance any prop I use (also brand-new props), and also the spinners. Prop manufacturers state that the props are pre-balanced at the factory, but I have found that not to be the case. I also check balance on older in-service props from time to time to verify balance.

[Brett Buck]

I have tried 3 different OS MAX-S 30's. All had the same problem. Vibration. Annoying vibration. The first one I figured it must be a bent crank so replaced it with NOS parts... nope still shook through the lines. Bought another new in box .30. Yep, shaker. A guy from So. Africa gave me one, thinking, third times a charm... nope. Sold all three and never looked back. I had them on a Dick Mathis Mongoose. Granted, the Mongoose did not have plywood doubters, but 1/2" balsa cheeks. But putting an FP .35 flew that plane just at the limits of a stunt airplane. The MAX-S .35 was a bit rowdy, I had not yet gotten the 4/2 break figured out.

  Yes, they saved 1/8 ounce on the counterweight, "for better performance". If it's 1/8 ounce lighter, it's 1/8 ounce better.

    I would also add, sometimes these engines are very unhappy with anything but 25%+ straight castor and one of the possible symptoms is excess vibration. I am not sure what the mechanism is.  I had one - a very long time ago - and while it is not as smooth as a modern engine, it was not out-of-family when it came to vibration compared to other contemporary engines, like the Fox 29 slantplug.

      Brett

[Colin McRae]

  Yes, they saved 1/8 ounce on the counterweight, "for better performance". If it's 1/8 ounce lighter, it's 1/8 ounce better.

    I would also add, sometimes these engines are very unhappy with anything but 25%+ straight castor and one of the possible symptoms is excess vibration. I am not sure what the mechanism is.  I had one - a very long time ago - and while it is not as smooth as a modern engine, it was not out-of-family when it came to vibration compared to other contemporary engines, like the Fox 29 slantplug.

      Brett

I have run my OS 30s on 29% all castor as well as 28% (50/50 castor-syn) and did not notice any real difference. I even tried 25% oil and to me it ran better at 28/29%. The engine has low hours, and I don't see an issue w/ 50/50 oil, but surely 28-29% total oil content.

[Phil Hawkins]

I have an OS Max S30s on a SIG Banshee and don't notice any undue vibration. I also carefully balance any prop I use (also brand-new props), and also the spinners. Prop manufacturers state that the props are pre-balanced at the factory, but I have found that not to be the case. I also check balance on older in-service props from time to time to verify balance

 I am fully convinced it was "operator error" however,  it is the only engine I have had such consistent issues with. I can't say I always balance my props, but with this one, I did balance props and switched props several times... as we used to say in the printing industry (I was a pressman for 30 years!) When you can't explain how or why the problem exists... it's a Phenomenon
I have an OS Max S30s on a SIG Banshee and don't notice any undue vibration. I also carefully balance any prop I use (also brand-new props), and also the spinners. Prop manufacturers state that the props are pre-balanced at the factory, but I have found that not to be the case. I also check balance on older in-service props from time to time to verify balance.

[Colin McRae]

I was wondering if someone can please provide me with the OS factory stock venturi size for an OS 40/46LA-s engine.

I believe it is 7.2mm  (0.283") but just wanted to confirm.

Thanks in advance.

[Brett Buck]

I was wondering if someone can please provide me with the OS factory stock venturi size for an OS 40/46LA-s engine.

I believe it is 7.2mm  (0.283") but just wanted to confirm.

Thanks in advance.

  .283 as measured from the outside using calipers.

    Brett