Please email Karl your questions by clicking "Contact Us". Please label your email "Karl: Question".

Some questions and answers will be posted in this section.

Page 9: Questions 240-259, click on links or browse page.
Q240 Saito 450R? Q250 What size 3 blade prop?
Q241 What warbird for a Saito 5cyc? Q251 4 blade prop for TF P-47?
Q242 Pros & Cons of Saito 15 or YS140 ? Q252 Trouble w/ G62?
Q243 Saito FA-90 3-Cyl in TF Corsair? Q 253 Can Saito 5 cyc turn a 4 blade prop?
Q244 Suggestions on performance of Quadra 42? Q254 Support for RCS radial?
Q245 OS engine kick back? Q255 46 or 60 for 63" ME109?
Q246 Check spark coil on gas engine? Q256 Q42 or M50 for Byron P-51?
Q247 Best engine for Byron Hellcat? Q257 Saito 450 R3 / TF GS P-47?
Q248 Quadra 35 or 42? Q258 31cc RYOBI for Meister P-51?
Q249 ST G4500 convertion to gas? Q259 24 cc YW engine problems?

Question240: "Hi Karl, I bought one of the first Saito 450R engines to arrive in North America. I flew it twice and had problems with consistent running. I shipped the engine back to Tower Hobbies. They replaced the engine. I was told the original engines had an intake problem that killed the # 3 cylinder. I was happy to receive the new engine. The new engine has the same problems the first one had: it does not run consistently on all cylinders, and the needle valve is extremely insensitive ( I can't get the engine to run rich). I am running the engine on 15% fuel, Hanger 9 glow plugs and a 22x10 Brolly prop. My top RPM is in the 6000 range. The valve clearance is checked regularly and I am using large silicon fuel line tubing. Yes, the brass tubing in the tank and the clunk are large too. It was suggested that I use OS-F plugs. I will try this and take advice from there. If the performance of the engine does not improve can you suggest someone who could evaluate and repair the engine. I would hate to part with this beast. Thank you, Duncan Campbell"

Karl: "Greetings Duncan, The size of the fuel tubing is crucial since, if the tubing inside diameter is too large, you have a significant drop in pressure. Not to mention the fact that it is easier to allow an air pocket to develop.
If it is too small, it can starve the engine of fuel, especially during high loads such as take-off, high-speed passes or any aerobatics that require near-max rpm's.

One thing to look into is a glow-plug driver. It is a good idea to have one installed so that the glow-plugs stay hot and lit at idle/low rpm range. The way most round-engine pilots do it is to simply utilize an on/off switch that activates at the throttle lever. At idle, mount the switch so it's closed, allowing power to travel through it. At the point when the throttle is opened enough for, say, taxiing, you can have it switched off, because now the combustion process helps keep the plugs lit. You can find these drivers through Hangar 9, Tower Hobbies, and several ads in RC magazines.

One thing that makes radials able to do what they do is in the intake manifold. It basically works like an atomizer by mixing the raw fuel with incoming air, theoretically evenly, and dispersing the mix around the manifold into the intake tubes. This works perfectly when the carb is metering fuel correctly. Which is to say, the carb is allowing the proper amount of fuel into the manifold to be mixed by the impeller. If these engines have a "pattern-failure" as we call it, with regards to one or more cylinders fouling or burning glow plugs, etc. then we need to be looking into carburetion as the culprit. The impellers are machined the same, the intake manifolds and tubes are the same, so the only other component to look at is the carb. Now that I think about it could also have a loose intake tube or carb mount. These can cause a vacuum leak and if the intake tubes, manifold and impeller housing are not sealed, it will wreak havoc on fuel metering the same way it will for an automobile engine. It might be possible the first engine you had didn't need replacement, it just needed a carb or inspection for a vacuum leak. Finally, when the mixture cannot be adjusted properly, as in your case where major movement in the needle position yields little change in performance, it will be the carb or the aforementioned vacuum leak. Let me know how it turns out, and thanks again. Karl"

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Question241: "Hi Karl, I am looking for a warbird that would match the cowl dimensions and power requirements to be a good with the Saito. Any suggestions? Al Taylor"

Karl: "Thanks for the question, Al. What I have found is, most 1/5 scale round-engined planes are too large for that powerplant. Their all-up weight is usually more than 20 lbs so and this engine is better suited for planes between, say, 12 lbs to maybe 18 lbs. Due to its relatively low displacement and diameter, usually a 1/6 scale plane will work.
Hangar 9, Ziroli, GreatPlanes all have suitably-sized birds that will work such as AT-6, F4U Corsair, Zero, etc. The cowl diameter is less than 10-inches as well, so when you select an airplane, pay attention to the cowl diameter. You can also go to your local flying field and locate some flyers that may have that engine, ask questions, measure, etc. With due respect, most will let you learn that way.
Hope this helps, Al. Karl"

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Question242: "I have a Midwest AT-6. She will have flaps, robart retracts (air) & struts, glassed finish, heated glow, 6volt receiver battery and standard size servos (futaba and hitec). I require that the motor be inside the cowl as much as possible. I dont require speed but more scale performance.. (scale person). More than likely will be mounted inverted. I require the best ease of starting ,dependability, low idle, swing as scale prop as possible. I hope to put a Saito 15 or YS 140 in her.. what are the pros and cons of each? OR do you have a better suggestion? Thanks, Nick e.l. Palanza"

Karl: "Hi Nick and thanks for visiting our site. Pretty cool, huh? I think so. I believe I have a better suggestion for you. When you go to this website (RCWarbirds..) there is a link to RCV Engines. They are a British outfit and have made some of the most remarkable RC powerplants I have seen!

I tested one of the big ones, the RCV120 for review here on RCWarbirds. It turned out unfortunate because of time constraints and lost data that I had accumulated on the test stand. I ended up with nothing to post and since the engine was on loan, had to return it. Sucks to be me. It's a long story that I won't tell here.

What I will tell you is the RCV 120 spun a 22" 2-blade prop with ease, up to 18lbs of thrust as measured on a sled of sorts that I designed just for tests like these. That engine started easily and once I made the necessary carb adjustments for the environment it started even easier and made better power.
Very smooth throughout the power band especially in the mid-upper rpm range.

I think the RCV 90 would be the perfect engine for you. It only requires a hole in the cowl through which to insert the starter. Incidentally, your field box for flying will have an electric starter in it, and the RCV comes with an adapter to install on the shaft to accomodate these engines. You need to bench-test this bad boy before you put it on the front of a plane, though. Regardless of how much resources you spend to make it scaled and detailed, you don't want a crash. Period. Anyway, hope this helps. Keep us posted. Karl"

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Question243: "Has anyone put a Saito FA-90 AAC 3-Cyl Radial into a Top Flite Gold Edition 1/8th Scale Corsair, if so how did it work out. Did it fly well? Was it easy to install? What did you use for exhaust? I am a ways from getting this motor into my Corsair But I like to find out the hang ups and what parts I have to order first for the exhaust. Any info would be appreciated."

Karl: "Thanks for the question, Geoff. I have seen this engine in several planes as well as read about its installation and the results.

The over whelming results of this combination show that it is very compatible.
Radials typically lend themselves better to dynamic balancing by nature of their design than do singles or even opposed designs. However, in recent years the art of metalurgy and computer programs have all but eliminated stereo-types with RC engines. They seem to fit inside the cowling as far as I have been able to observe since diameter dimensions aren't listed online. How you handle the exhaust is really a matter of preference, Geoff.
Some guys let the individual exhaust stacks stay and it actually works with the nearly all-around cowl vent flaps allow the exhaust to exit sufficiently. Still, others spend the money and/or time to have custom stacks fitted or just install an exhaust ring.

This radial should look real nice inside the cowling and work real well for power. Master Airscrew has some cool three-blades that should work and I think APC does as well. This plane doesn't weigh much so you won't need much prop either. Hope this helps, keep us posted if you will. Thanks. Karl"

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Question244: "I have a Quadra 42 on a sport airframe, flying a 18 X 6-10 propeller. Tacked it today at 7300 RPM plus....idles at 2100 smoothly and 1900 roughly. Do you have a suggestion or comment? Also, what 2 blade prop would you recommend for my 3.2 Brisson powered 26 lb Corsair and then a 3 blade? Thanks, Larry Wilson"

Karl: "Hi Larry. The issues here could be ignition-magneto, plug wire, plug. It could be fuel-related in that the oil/gas mix is incorrect. If the fuel isn't volatile enough it won't idle well. Sometimes adding a little rubbing alcohol helps (someone told me that one so I don't even know if it would work. Maybe in theory...) or it could even be prop-related. Too much for the engine to swing.

I would consult the manufacturer of the engine and see if you can get spec's on things like resistance (ohms) in the coil/magneto and the wire. I can already tell you that if the plug wire shows more than 1k-ohm then it needs to be replaced. They are such short wires that there really shouldn't be that much resistance; Make sure the plug is the correct heat range; ensure your fuel is good quality and mixed properly; rebuild the carb if necessary as it could have a vacuum leak around the shaft, an o-ring or base gasket, which will also cause this problem. Hope this helps Larry. Karl"

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Question245: "Hi Karl, I have a Midwest AT-6 with a side mounted OS 1.6 with a pitts muffler and on board glow. My problem is this: When I fuel (thru a fuel dot) I fill until fuel comes thru the muffler tubes. I do not prime the engine as it will fire the first flip, but most of the time it pops, kicks back and loosens the spinner nut! (I am using a Hugley Heavy nut). Then smoke will ooze from the exhaust tubes! If the nut does hold and the engine does fire and run, it will not take throttle quickly. If you ease the throttle slowly, it will eventually reach full throttle and run perfectly. I have about a dozen flights on this plane/engine without incident in the air. It is just a pain to get it running at start-up. Any recommendation will be appreciated. Thanks, Mike"

Karl: "Thanks for the question, Mike. There are likely two causes to this problem; The first could simply be improper fuel metering--in that excess fuel is allowed to flow into the engine without relying on the engine vacuum for the air/fuel intake. The thing here is, is that the excess is not enough to kill the engine or constantly foul the glow plug so the over-fueling condition may not be readily apparent. When the fuel is flowing as it's running it mixes with the air and allows the volatile mix. When you shut down the fuel that has entered the combustion chamber does not complete the burn so it smokes. This likely is the cause for the prop shaft exhibiting excess "counter-torque" and loosens the prop nut.

The second possibility is the glow plug choice. I almost hate to sound un-caring about one's financial condition but get the best glow plug you can for these engines. As I've said in other posts here---"there's no emergency parking at 500ft...." (or 35k if you're in a real plane...) It makes sense to spend the money on stuff that has dire consequences for cutting corners---radio gear, servos, engine ignition parts, etc. In this case if the glow plug is too cold of a range it doesn't stay hot enough to burn all the fuel in the cylinder. This can also make for hard-starting.

Bottom line Mike, make sure all the fuel hose is the correct diameter, there are no air/vacuum leaks on the carb or its mounting base and make sure the proper mix of fuel is being used. Hopefully this will help you by giving some ideas to address toward solving this problem. Hope it helps. Karl"

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Question246: "Hi Karl; Do u know of a good way to check the spark coil on a weed wacker type engine, like with a meter etc. Thanks in advance. Dick"

Karl: "Thanks for visiting our site Dick, hope we can help you here. The best way is to simply disconnect the plug wire and connect a spark tester. Most of the time a decent auto parts store will have one of these---it is built from parts of a spark plug but has no provision for screwing it into a head for use--it is built with a spring-clamp and that clamp goes to an engine ground.

Attach the plug wire to the spark tester and clamp the tester to part of the mounting area or a bolt/fastener then---providing it has a rope-style starter as possibly a back-up start method---pull the rope starter as if trying to start it. Watch the plug tester for the spark to be present. Here's where it get difficult to "teach" about reading the spark to determine coil energy. If the spark is present and makes a "crack" noise and appears light blue or nearly white, the coil is very strong. If you're still not sure, just grab the tester and try to start it again and see how exciting THAT can get! If your nearby friends duck as you spasm and thrash about then it's all good....just kidding. If the spark appears light blue to perhaps orange, and has a weak sound it could simply be the gap between the coil and the magnet on the flywheel maybe too large--this can be adjusted and retested. If there is no sound and/or no spark present then you likely have a failed coil.

There's a few things you can check though which is basic electronics. Check all the related wiring for quality of the wiring, insulation and ground connections. Some of these types of coils have one or two blade-type connectors and they can come loose simply through engine vibrations. Bottom line is if you still have weak spark then replace the coil. These types of ignition systems are very simple to diagnose and repair. Hope this helps. Karl"

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Question247: "Hi Karl; I just picked up a Byron Hellcat . I was wondering what would be the best engine for it. I was hoping for a 4 stroke and possibly a radial to maintain a reasonably authentic sound. Any thoughts would be appreciated. Thanks John"

Karl: "Thanks for the question, John. The Byron Hellcat is a cool kit for sure. Should be fairly easy to build and fly so have fun. With regards to the engine----I will, of course since I am a lover of round engines, recommend any suitable radial as this was one of the many premier fighters that used a round engine. Robart has one that is likely best suited for 1/5 scale which is slightly larger than 1/6 scale. Saito has their 450-3RD I might have the numeration messed up, but....) this is a large 3 cylinder radial that runs on glow fuel and probably will make 4-6 hp. If you feel like really scaling out the plane consider SoloProps' scale 3-blade ground-adjustable-pitch prop. What you give up in power due to scale fit in the cowling you can usually make up for with a GAP prop. The prop functions just like the rear end gears in an automobile. I can explain that one later if you want.... TechnoPower engines in California also has several engines including 5,7, and 9 cyliner radials on glow. Theirs are somewhat limited in power however so do some research (www.techno-power.com). The Saito 450R3D is perhaps the best unit because of power and size-should fit inside the cowling with no cutting.

If you want to spend more money and use gas then look at RC Showcase.
They have a few offerings that have to be seen and heard to be believed (they have audio and video of their engines running..)Hope this helps, John and good luck. Karl"

Update: "If you have a 1/5 scale Hellcat you can look at Saito's 450R3 radial. It makes great power (I think it's rated between 5 and 6 hp, which is good for many planes. Others to look at if the plane is smaller is ones from TechnoPower engines in CA, other Saito engines such as their 5-cylinder glow unit that is rated about 4 hp. Bear in mind you can also utilize a Ground-Adjustable-Pitch prop such as the one Solo Props makes, so you can use a scale-sized prop as well and really match the engine/prop/plane system.

If you go with a larger plane you will likely have to consider the more expensive but beautiful radials from Robart and the gas ones from RCS and even some through Desert Aircraft and Cactus Aviation. Go to their sites to find the links to these engines.
Hope this helps, Karl"

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Question248: "Karl, I have a Quadra in a Byrons Pitts, swinging an 18 x 8 prop. How can I tell if it's a 35 or a 42? Thanks, WG"

Karl: "Thanks for the question, Wayne. The easy way is to find on the crankcase somewhere the size that should be cast into the case on or near the mounting, it can also be in the side of the crankcase or even on an embossed or otherwise marked label simply glued to the engine.
*sigh* OR---you can do it mathematic-ally by using a digital micrometer and measuring the cylinder bore and measuring the distance the piston travels from top-dead-center to bottom-dead- center. The formula is bore x stroke=displacement. I think you might have to also multiply by PI which is 3.14. For example: 4.00" x 3.50"= 14"x 3.14 = 43.96 then multiply by 8 and you get 351.6 cubic inches (ala 351 Windsor Ford v-8).
So, you might try this and see what you get. Hope this helps. Karl"

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Question249: "I have a super tigre G4500 and want to convert it to an ignition gas
> oil burner and so far I have not had any luck?"

Karl: "Mark, I haven't had much experience with conversions of this type but with glow engines the compression ratio is very high, like 20:1 and this will not allow a gas engine to run well at all. One of the first things to do is ascertain its ratio and proceed to lower it by means of thicker head gaskets/shims, shorter connecting rod or different piston. Gas engines only need, say, between 9:1 and 12:1 depending on the octane rating--usually the higher octane the better burn so you want a higher compression ratio.

Other than that it would be advisable to seek a local expert with whom you can converse/do show-and-tell with this engine in different stages to make sure you cover the bases well. Some engine manufacturers I have heard sell conversion kits/parts to one degree or another so look into that as well. Sorry I couldn't be more help. Karl"

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Question250: "I was wondering if you can tell me what size three bladed prop would you use on a satio 1.50 engine? It says that it uses and 16x8 two blade. This is going on cmp 70" wingspan hellcat, Can you please help me with this problem. Thank You Eugene"

Karl: "Eugene, in general I have always used the rule of thumb that going from a two blade to a three blade you reduce either 1" in diameter or 1" in pitch.  So for the recommended 16x8 two blade you could use either a 15x8 or a 16x7 three blade.  I'll double check that for you but in the mean time I would give Horizon a call and talk to someone in technical support to see what Satio recommends. The thing is, is that now we have better fixed-pitch three blades that are larger, and one guy has developed a functional constant-speed unit to be used with his reduction drive for larger Mustang planes and the like. And we have Solo Props too, which has an unbelievable line of quality props and hubs.

The scale diameter for a 1/5 scale Corsair is 32". Given that this is a Hellcat and I haven't done any research on how large the full-sized prop was I would guess that for a 70" w/s plane the prop diameter would be around 20", probably less, and be a three-blade. See, even though we are increasing the diameter and the blade-count we can still adjust the pitch (on the Solo stuff anyway....) to achieve the proper flight characteristics. Pretty cool, huh? If it were me, I would use the Solo unit and simply make pitch adjustments to achieve good flight. Hope this helps, Karl"

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Question251: "I have a topflite P-47 86inch wing with zenoah G62. Im looking for a scale 4 blade prop and hub like what they use for static display but one i can fly with . Do you know were i can get one Thanks Ed"

Karl: "As a matter of fact, Ed, I can think of two places to go to; one you will hit paydirt directly and the other perhaps with some dialogue you can get what you want. Both are extra-ordinary in their achievements. One place is www.soloprops.com in Canadia and the other is www.warbirdpropdrives.com. The latter actually uses props from SoloProps to do prototype design and testing with, but I think they even have their own plan so it can't hurt to check them out and ask. Hope this helps. Karl"

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Question252: "Hi Karl, I bought a used 28% Extra 300 with a G-62 and C&H Ignition. I rebuilt the carb and added a vent line to the pump which is run inside the fuse. The problems are: When the low end is adjusted for a smooth idle I can't idle down low enough to taxi so I leave it a little rich. Mid range the engine 4 cycles. Top end the engine has an intermittent miss but no 4 cycling. I richened the high needle thinking the miss was caused by a lean condition, but it caused the 4 cycling at mid range. The engine has a new spark plug and ignition battery. I haven't check the ignition timing. The problems were present before I rebuilt the carb. I use Amsoil 50:1 Super Unleaded. Thank you for any help you can give, Lonnie"

Karl: "All right, Lonnie, let's get back to basics here. First we need to make sure the cylinder is sealing properly. There are a variety of backyard ways to do this including simply putting your finger over the spark plug hole (plug removed of course) and, with ignition and fuel off, spin the prop or use the starter motor to ensure it has a good, strong suction and will blow your finger out of the hole. Perhaps the best way is to simply install a compression tester to the engine and crank it over with the starter. It should be at least 100 psi I think. If it's down around 40 psi or so I think you have a problem. In that case you disassemble the engine, clean and inspect the piston skirt and top, and the cylinder liner/wall as well for cracks, scoring, hot spots.

If all of that measures up, please, do set the ignition timing. If I'm not mistaken on the strategy of the electronic ignition modules, you have to have base timing set to spec's and the computer takes it from there so make sure that is ok. Make sure the spark plug is the correct heat range. Believe it or not spark plugs can be rendered useless by too much fuel in the cylinder. It's called fuel-fouling. If it can happen to a brand-new vehicle it can happen to any internal combustion engine using gasoline.

You said you rebuilt the carb or had it done. This is a good step to take. Work all these bugs out before you take to the air, my friend or you'll be sorry. Make sure all the gaskets are correct for that carb, they are in the proper place (some gaskets in carbs have a sequenced installation procedure...) and the fasteners are tight. In a full-sized automobile with a carburetor there is a significant margin for torque variations in the carb fasteners themselves that won't always affect the operation of the carb. In a carb this small if you over-torque a screw you can crack the housing and cause a vacuum leak, and you can warp the mating surfaces so they won't seal properly so great care has to be taken here.

Check the coil and ignition system for performance. Is the battery good, even on a load-test? How's the resistance in the plug wire? For a short one like the ones used on RC engines it should be negligible---around 800 ohms and usually less (they technically are called-"high-tension-wires" so, hence the resistance levels). Have the module diagnosed if necessary just to eliminate all possible causes.

Hopefully you can then assemble the engine, add fuel/oil mix start it and see how it runs. If, along the way in the above-suggested process you find some glitches and fix them, then when you get to the bench-test phase you should have a srong-running engine. Hope this helps, Karl"

Update: "Thank you Karl. I found the problems. The fast idle was caused by the throttle plate not closing all the way.  The throttle cable was too short.  This problem was present before I rebuilt the carb.  I feel stupid for not looking at it closer when I rebuilt the carb.  Now that the throttle closes completely I have the carb adjusted for a smooth and low idle. The miss was caused by a bad place in the plug wire.  Apparently the previous owner attempted to repair the plug wire with silicone and a small rubber hose over the repair.  When I first saw the rubber hose I thought I was to protect the plug wire from being damaged from the bracket it was wiretied to. Thank you again for your time, help and input, Lonnie"

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Question253: "Hi, I I have been reading your articles with interest. I have just purchased a SC 400 5 cylinder radial engine I'm hoping to fit to a top flite 85" P47 The info for the engine states "After half an hour's running the radial turned a 22 x 8 ins Zinger prop at 6,500 rpm, and a massive 24 x 12 Zinger prop at 5,000 rpm" Do you think this engine would turn 20 x 8 or 20 x 10 4 blade prop? I don't have much more info on this engine at the moment but I believe its around 4-5 hp. Best Regards, Mike Knowles, UK"

Karl: "Good day to you, Mister Knowles and thank you for visiting our site. Like you I love round engines (radials) as they are a true master piece of engineering. Even the "little" ones we use in RC. The best place I will send you for this information is www.soloprops.com. They are a Canadian company and have perhaps the best adjustable-pitch props on the market. I know of some others that are coming close to production but they use a different type of set-up to make it work. SoloProps has what we call " Ground- Adjustable-Pitch", or GAP propellors. This type of system is decades past due, in my opinion. But, to be fair, the technology to make it possible did not exist for the RC modeler decades ago, so I suppose this IS the right time.

It is possible to install an adjustable-pitch prop to 4-5 hp engines and have them work very well. In the past, a fixed-pitch wood prop would have been too heavy for the engine and you would be defeating the purpose. Even if you bought several props of different pitch ranges you would have to remove the prop after each flight just to change it. It may well be possible then to have to replace the prop shaft and nut before it is due simply due to the wear induced by so many prop changes in the field.

The SoloProps will range from flat or "zero" pitch up to 24 or even 26 for the larger props (the thinking here is, if the engine is large enough to handle a 4-blade prop it likely has the torque to maximize the higher pitches---but within reason, of course...)

Mr. Knowles, I have addressed this propellor issue in other posts here that explain in better detail how for an airplane the propellor acts as the rear differential gears in a car do. With any kind of adjustable pitch prop you need time to test. And PLEASE don't fly until you have a grasp of what the low limit is for the prop/engine combo. Too much pitch and the engine bogs due to the loads induced; too little pitch and you could well blow an engine; either way here and you won't fly so that's why we test. Here is a guideline:
1) a 2-blade prop can be pitched up to 24 on this engine--it's moving alot of air but with only two blades;
2) add a blade and you increase the surface area for lift so you do one of two things---either decrease the diameter or the pitch;
3) if you fly with 4-blades the perfect combination my require a much shallower pitch than what you thought or think that you want, so keep an open mind.

Also it helps to research propellor theory and function. They are also a plane as the wing is and creates lift--it's just oriented vertically not horizontally.

Hope this helps and let me know if you have any other prop questions.
Thanks, Karl"

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Question254: "RCS have nice radial 4 stroke engines, but can't find any detailed specifications about them. Can buy them, but what with support? Can you advise me in the subject?...Joseph Gross

Karl: "RCS Radial---Welcome to RC Warbirds, Joe and thanks for the question. One of my favorite engines to recommend is, in fact, the RCS Radial. For me, there's nothing cooler than a round engine. Radials are an absolute engineering miracle. RCShowcase has perhaps the largest gas radials out there in the RC market. My research hasn't come up with any new ones. I believe their product support is outstanding, Joe. A few years ago I was corresponding with them while soliciting information not only for this site but for my own project. They answered all my questions, the quality seems great even though I don't own one. I know you can order one directly from them and I don't know how accomodating hobby stores are. It's a specialty item for them usually. The cost to stock them can be significant given the budget of most hobby stores that I know of. Balsa USA has a Stearman bipe that is perfect for this. Obviously, if you are serious and you haven't already tried, go to their web-site, www.rcshowcase.com and get their contact info. I'm sure they'd love to provide answers. Hope this helps, Joe. Karl"

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Question255: "I have a ME 109 with a 63" wing not sure of weight just wanted to know how big of an engine I need I have a 46 but thought it might need a 60 or larger I know you guys are in to the really cool big planes and some day I would like to build and fly one but Im a new bee at war birds and I think for learning this is big enough can you help me with this and I cant find a replacement cowling for it any Ideas of where I might find one."

Karl: "Hi Butch, Thanks for the pictures of the Me109. Nice work for starters. You've made more progress than I have on mine.

I have come to like a British line of RC engines that goes by the name RCV Engines. These are pretty easy engines to operate and the best part for guys with limited cowl space, they are perfect because of the design. Specifically, look into the "SP" line. You'll be impressed and you won't have to butcher a cowling.

As for a replacement cowl, if you don't have luck contacting the manufacturer and obtaining one through them, try going to RCUniverse.com, HobbyLobby, and others to see if you can get one. Or, ask one of our other advisors about it and maybe they can hook you up with one. Hope this helps. Karl"

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Question256: "Which would be a better way to go for a Byron Mustang - reduction drive and a Q42 or M50? I have heard that the Q42 is still available from Quadra, but the M50 is out of production. Do you know if anything else (like a Fuji) bolts in place of the M50? Thanks for the help ..Josh

Karl: "Josh, Thanks for the question Josh. You seem to have quite the project on your hands. I have a few suggestions for you, starting with the most affordable of the new engines. First, look at Cactus Aviation's 3W line. It's known as 3W 85xi. This large single generates about ten horsepower and has enough displacement to get you airborne. Size does matter here, you know. You have a 1/4 scale plane at nearly 50lbs so this is one of those times you will appreciate having the extra power e'en though you may not need it. This engine retails for about $800 USD. Next we have an in-line gem from the Czech republic known as ZDZ. These are beaut's. This one displaces 100cc's, is an in-line like I said and has nine horsepower on tap. It is a real sweet thing, but at a heftier price of$1,275 USD just for the engine. The exhaust and other accessories are extra. These both are two-stroke gas engines with electronic ignition. Usually are a cinch to install and maintain. Lastly I like to plug these guys in California who have designed and built a true, 1/4 scale glow-fuel version of the Merlin v-12. Complete with supercharger, water cooling, etc. If you really want scale points and have the capability to engineer its installation and supporting structures, you need to consider this one. It's much pricier, as expected, but just having it would be enough for bragging rights! You have to buy plans and castings and do, or have done, the machining your self. Check it out for kicks and giggles: www.quarterscalmerlinproject.com. Let us know what you decided, hope this helps. Karl"

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Question257:"Hello Karl, I am in the process of buildind a TF P-47 Giant scale. The reason that triggered my interest to build it was to fit the 450 R3 from Saito. I think it fits .just fit. I had tried the saito 90R3in a H9 Corsair, it looked good but way under power. I had just begun in this hobby 1.5 year ago and thought that a 90 was a 90. I soon discovered that a 90R3 (1000,00$ can then!) is way underpower an it is now in a H9 Sopwith Camel and I only took it out 2 times so far on calm Sunday afternoon when I'm dosed up with my other well powered warbbirds.

I beleive that the 450R3 is powerful enough with 5.5 hp to pull this P47. I intenmd to install it with a 40 oz tank and reluctant to muffler pressure. I will use the MCD473 for glow power. Kelvin @ Keleo Creations is making my ring.hopefully for may 2008.

I will fit it in a fiberglass specialty cowl Do you have any advise on the size of tank, pumping system and do you know of anyone flying a similar warbird with the Saito 450R3. I know how heavy it is. Would appreciate to hear some comments from you. Thank you. Normand"

Karl: "Thanks for the question, Norm and welcome to our site. Pretty cool, huh? Yeah, I like it too. Sorry about the delay in answering. I had some computer prob's at home which still have not all been resolved so I have resorted to using my computer at work, which is dicey at best.

Anyway, the Saito line of radials is, in my opinion, the best glow radial offerings out there. They have already proven their metal in the four-stroke singles and twins so the multi cylinder versions in their radials is darn-near second-to-none.

I have heard good things about what's called a Kline-pump for glow fuel delivery. It isn't that much different than a pressure-tap from the exhaust but it is more positive fuel delivery. One guy I know locally (for me anyway) uses it and has not had a problem with fuel delivery. Oddly he even has a P-47 with about an 80-90-inch wingspan so it must be good. Never seen him crash or ditch so I'd say it works.

Search the web at Robart.com, Dubro.com and others to find the one that will work. The fuel delivery is affected at least by few things---plane weight, engine, how much aerobatics are going to be done, etc. so make sure it can meet the demand of the WHOLE system. Hope this helps and thanks again for visiting Karl"

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Karl: "Thanks for the question, Paul and welcome!
First, it is difficult to know the power output of non-RC-spec 2-stroke gassers since the folks who make the ones used for, say, weed trimmers/chain saws/ other lawn/garden type applications don't relate to "power-output" like guys in RC hobbies do.

However, that said, a gasser is a gasser with the only real potential difference being the porting and reed valve calibrations for fuel management. Face it, a weed wacker doesn't have to worry about high-g turns or inversions that affect fuel delivery. Sure, you can invert a weed trimmer but it still is at what might be termed a "zero-state" of pressure vs vacuum so fuel delivery is always the same.

The rpm sounds too high--perhaps a typo somewhere but no small gasser that I know will turn much more than 18k rpm. Now, a jet turbine for RC will see 100k rpm, but we aren't talking about them here. Still, many past RC guys have modified their weed eater engines for RC use and had alot of success with them with some tweaking of course. The Meister P51 is 90" in span and should weigh-in around 18lbs. according to their info. Depending on scale details, powerplant, etc you could exceed 20 lbs. In my opinion, with engine in good shape and good fuel you should be able to swing an 18" prop, maybe even up to 20" without performance problems. The thrust sounds pretty accurate if not slightly low. I tested the RCV 120 once and with a 20" prop it made 16 lbs thrust.

Maybe also look into an adjustable-pitch prop to maximize your engine setup with that airplane. You'd even be able to get a prop then in 4-blades--just watch the pitch if you do that. The engine isn't that big so you can't be too aggressive on the pitch.

Hope this helps, Karl"

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Question259: " Hi Karl: I hope this email gets to you. After clicking on your email link in RC Warbirds it comes up as mike@rcwarbirds.com. Hopefully Mike will forward it to you.

I want to see if you ever encountered this problem. I have a little 24 cc YW gas engine in a scratch built 96" Cloud Dancer. The engine runs well in any position but there is one situation where it appears to be starving for fuel. If you fly way up high and do a full power dive it will run fine all the way down to the ground. However, when you begin to pull up the engine burbles as though it is starving for fuel. It does not matter how high you are or how long you are flying nose down it is always fine until you pull up. I have been thinking of putting a header tank so that the fuel line could never see air but I realized that this also happens on a completely full tank of fuel.

In an effort to correct the problem I rebuilt the carb and put all new gaskets with a new diaphragm valve and little spring loaded control arm. Had it adjusted with the webro gauge but did not correct the pull out problem.

I was having an issue with the igniting module where it was arcing internally. Occasionally it would only run slowly no matter where the throttle was set. I replaced that and flew it yesterday and now there is no more ignition problems but the pull out condition still exists.

Here is another clue. If I do an inverted pull out I have no problem. I did not want to pull supper high g's as I was afraid the wing would fail but no hint of a problem.

Changing the high speed needle valve setting to richen it up does not seam to help. By the way the engine turns up to 8450 rpm on the ground and runs faster in the air with a 16-8 apc prop.

Here is what I am thinking is the cause. The carb is orientated such that the weight of the diaphragm valve would want to close when the plane is pulling out of a dive due to centrifugal force. In level it is pointing up and down. If it goes down it would tend to close the valve causing it to lean out Do you think stretching the valve spring may help? Did you ever hear of this condition before?

Best regards Lou Cetrangelo"

Karl: "Thanks for the question, Lou. Sorry for the long delay in responding. I have had some significant computer issues to sort out and it appears likely that I have eradicated them. Hopefully I can keep them at bay for good. I can't stand it when I spend hard-earned money on something nice and it won't work like it's supposed to. Onward.

I must say you are many things:observant, detail-oriented, thorough, and likely have much common sense where mechanical issues present themselves. You have likely diagnosed your own problem, sir! Since the problem goes away inverted you likely are on the right track with regards to the valve position under load.

Carb diaphragms are finicky things to be sure, and usually are susceptible to a miriad of changes---usually pressure-related. Could be atmospheric pressures or pilot-induced through adjustments. However I would not recommend "adjusting" the spring by stretching it. This could alter the spring's ability to respond properly under other operating conditions and THAT could mean taking your plane home in many more pieces than when it came to the field. Try to be innovative in finding a source for the spring---ball-point pen, cabinet door closure spring, automatic transmission check-ball (or other kind of check ball..) spring. These all see differences in pressure in their normal environments and are well-suited to withstand many cycles. The deal would be whether or not they fit. It would have to be pretty small.

Ensure your fuel supply is not being compromised through collapsing of the fuel line, make sure the fuel line is the same kind and diameter (inside especially, but outside diameter difference means more flexion in the fuel tube walls, which translates into fuel pressure fluxuations, which will directly affect fuel delivery). These are really the only other significant items that I can think of that would contribute or possibly cause this symptom in flying, so I hope this helps.

Thanks again for your patience, visit us again soon. Karl"

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