Question 97: "I have a 96 inch P 51 D glass over wood body. I am thinking of using a 69 cc weed whacker motor. Will it work and have enough power to swing a three bladed prop? "

Karl: "Thanks for the question, Mr. Doorer. Here's what I can tell you from my experience and common sense. First, weed-wacker engines are oily things, like Detroit Diesels. The carbs don't have to deal with altitude changes or g-forces so they are rudimentary at best. If time and money are no big deal, you can fabricate all the adapters you want, experiment over and over with carb tuning, fuel control and so on and somewhere along there maybe crash a plane or two trying to figure it out. Do you want to fly or just pretend? On the flipside, though, to validate your position, is the age-old ingenuity factor that says you can design what ever you want and build it. More power to you. As far as the power issue goes, it should have no problem moving a prop that size. Let's be realistic though. As you near completion of this great airplane kit and look forward to flying, do you really want to take all the extra time of the R & D factor? Personally, I like the idea of phasing in the engine work as I build, so the whole plane is like one big unit, not pieced together, and my patience says not to wait too long for engine work. I don't know if this helps, but you are more skilled than I if you decide to go with your own stuff. Cool idea, really. Hope this helps. Karl. "

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Question 98: "Karl, I have reciently purchased a C-160 Transall. I have installed 2 Magnum XL28's in it, inverted. I am new to inverted engines and I am having a problem tuning them. I have been into nitro for too many years to count but these are driving me crazy. They both start and run great at 1/2 throttle, and very close to each other in rpm 7900 and 8100. However, if I increase the throttle they both bog down. If I decrease the throttle one cuts out right away the other come down to a high idle but then will stall say below 4000 rpm. Also the one that stall right away tends to surge a bit if I decrease rpm to about 6500. They have independant tanks. The fuel lines have very sharp bends in them, I am afraid that is the problem but there isn't alot of room. I am wondering if a check valve might help... Thanks for any help you can offer. Bob "

Karl: "Good question, Bob. Here is what I can suggest to you. Make your fuel line the same diameter and possibly make it a smaller I.D. and add a Kline pump or something else adequate. What seems to be happening is they are loading up due to the inversion. The key here is to control fuel delivery and make it as equal as possible for both. Do what you can to eliminate the sharp bends and make the lines the same length. This is understood by the lanes on a running track or even a racetrack. The inside lanes travel less distance than the outer ones. You want to make the fuel travel the same distance so the fuel enters the engines at the same time. A slight reduction in the diameter of the fuel line and adding some pressure may also help even the fuel delivery by decreasing the chances of air locks in the line and resulting in engine surges or other pulses that can and likely will cause a stall. Sounds like you are on the right track as far as synchronizing, but let's deal with the fuel delivery first. Use a laser-type temp gun such as that made by "Raygun" as this will be the biggest help in getting the engines to run the same. Equal temps within ten degrees will mean more equal fuel distribution. Hope this helps. Karl. "

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Question 99: "Hi Karl Great web site.....I have a 1/7th sport scale spitfire (Topflite gold edition) and the all up weight is 9.5lbs. The engine I have fitted is a Laser 80 4 stroke do you think this will have enough power for the weight when taking off from a grass strip?
Thanks in advanceDave"

Karl: "Thanks for the question, Mr. Lakeland. 'Tis a pleasure to know we can help our friends across the pond with these things. The Laser engine is a pretty good one, it should be at least 1 hp---others I have info on show over that for the same displacement. For a 9+ lb plane taking off of grass, you might need a little more umph so I would look into say a Saito or O.S. 4-stroke. They are state-of-the-art, reliable, they sound cool and make good power. Try the Saito 1.20--this is plentiful and proven. Hope this helps you and I apologize for the lateness getting back to you. Thanks, Karl. "

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Question 100: "Hi karl I'm currently building a 1:6 scale (100") lysander,, and I'm looking at saito radial engines. have seen that the 5 cylinder (50cc) will swing a 20 -odd inch prop without too much trouble, it will also fit inside the cowling.
It turns out 3.8 hp and weighs 2.4 kg (5.3 pounds). Is it too big for the plane? what I also want to do is run on a 3 blade prop without it looking stupidly out of scale The saito is the only engine I can find that takes a decent sized prop, - 20 " is still a bit under , but isnt as bad as 14 - 16". was thinking of maybe trying a 20-22" x 6" 3 blade. what do you think? cheers, zippy."

Karl: "Good question, Zippy. Master Airscrew and I think APC make 3-blades that are that large. Master has a series they call the classic series and that would look great on this plane. As for the engine, O.S. also makes a 5 cylinder radial and it has 4 hp. You might look into another outfit called TechnoPower Engines. They have several radials to choose from for 1/5 and 1/6 scale. Their website is www.technopowerengines.com Give them a look. Hope this helps. Karl "

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Question 101: "I have a FPE 5.8 i want to put in a nosen P-51 but it looks like the carb will stick out of the cowl which is unacceptable for me. yes i may sound anal but thats what i want. so heres the question. is it a good idea to relocate the carb and are there any things i need to be aware of in doing so. BTW i am a foreman in a machine shop and i also own a full size CNC vertical machining center so custom adapters etc are not a problem. i was thinking about turning the carb around 180 and putting it in front of the cylinder out of the way of the cowl where i have room for it. will this work or am i asking for trouble? thanks Craig"

Karl: "Craig, here is what I think you should do. The engine is 8 1/8 inches wide and I don't think the cowl is that wide. If you put the carb in the front, the prop wash and air speed forcing air into the carb will likely give you metering problems bigtime since you can't control fuel while in the air. It will probably run real lean and possibly burn up the engine. Since doing the machine work is not a scary venture for you, here's what I think....build an adapter plate that will mate to the engine, like maybe 1/8 or 3/16 aluminum flat stock, then get some aluminum pipe that is slightly smaller than the carb outlet diameter at the back of the throttle plate so you can blend it by hand with a dremel or something similar (yes, like a porting kit...) The pipe has to be smaller to maintain air/fuel velocity since you are making it travel farther. Use a tubing bender or equivalent to form a manifold with another adapter to accept the carb. You might need to fabricate a support bracket for the carb due to the length. Run this manifold to the back, behind the head---perhaps tilting the carb slightly soas to better keep the carb throat into the air stream but also will allow you to keep the cowl intact. Give it some thought, draw some plans and see what happens. Thanks again for your help. Karl. "

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Question 102: "Karl, I want to build a Ziroli P51. Which engine would be better, G62 or Q75? I have been flying smaller mustangs for 13 years and now would like to go giant. Also, which is better, magneto ignition or electronic, Pros and Cons? Thank you for your help. John"

Karl: "Thanks for the question Mr. and Mrs. Thompson and welcome to RC Warbirds. The Ziroli is arguably the best out there for the money, as you know you could pay more, but that's what makes this sport so dynamic, all the ways to do things. Both of the engines you are looking at are good. They are proven, reliable, and make more than enough power for your needs. I wish I could offer you an engine that was, say a 4-stroke or an in-line that had enough power, but I can't so we'll stick with your choices. If I were in this situation I likely would select the G62. As far as ignition, you definitely need reliability since you can't pull over and park it to work out a glitch
that happens when you're flying. Drag racers use magneto's because of the power they can take without burning up components. The only problem I could forsee is possibly the magnet getting weak and not providing the current for adequate ignition voltages but to be honest, I've never heard of that happening to anyone using mag ignition. There is usually fewer parts to worry about as well. As for electronic, when parts go out, they go out---now. They are usually easy to replace but you have to make sure the ignition components are always clean. They have a lower tolerance for dirt, debris, heat, etc. As it looks now, if I had to make a decision, I would choose the mag ignition. Hope this helps you select what will be best for your plane, and good luck with the build. Karl."

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Question 103: "Do you know if anyone has done a in depth study on engine performance at higher altitude. If so where would one find this information. I fly between 5500 and 7000 feet and would like some kind of a starting point when tunning my engines. So far everything has been by guess or by golly. Thanks for any help you can give me. Jerry"

Karl: "Thanks for the question, Jerry. I may not tell you here anything that you don't already know, but it sounds like you may be in a place like Denver or other mountainous region so you already know about air density, etc. Turbochargers were originally invented for assisting airplanes in getting air/fuel to the engines at high altitudes because of the rare air. Compressing the air and richening the mix is how they achieved this. Turbos or other form of forced induction are out of the question for any RC plane smaller than 1/4 scale so you may need to stick with the not-so-consistent way of tweaking and running, repeat.

I don't know of anyone who has researched this and I attribute this to the fact that most RC airfields are in the wide-open---lower---elevations so this kind of tuning is not usually required. What I can tell you is from years of experience with a variety of internal combustion engines. You may be locked into experimenting with different spark/glow plugs, different fuels such as 100 or 110 octane av gas or different mixes of glow fuel. Beyond this, I don't think I can be much help. Well, I guess you could relocate to a lower altitude..(just kidding haha). Hope this helps in some way. Thanks, Karl. "

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Question 104: "I have acquired an Bud Nosen P51 Mustang Kit with the 102 inch wing span. I am concerned about an engine with enough power for it. Would a Zenoah G62 be enough? Please give me some information on other Zenoah engines or other brands that would do a good job. I plan to use 8 to 10 servos and retracts"

Karl: "Thanks for the question, Mr. Cote. Whether or not the engine is powerful enough will depend largely on what kind of accessories you put on this plane. At 102" it will already come in around 18-22 lbs. So if you add things like airbrakes, flaps, retracts of a heavier type, etc, these will all be contributing factors for you. Here's what I'll say first. Try to come up with as accurate as possible estimation of all-up weight for the plane, then look into engines. You might start off really liking one type of engine then find as you build, the weight will require a more powerful one. This affects the time-frame for the build as well as the pocketbook. As far as other engines, I like the offering from 3W Cactus Aviation. They have a 7.5 hp engine dubbed the 3W 75 that looks like it would fit the bill. Between the tried and true G62 and the 3W 75 look into the prop shaft length--they both have electronic ignition so that is a big plus---but compare how the CG will be affected with the longer engine from Cactus vs. the G62. Both are good engines, so it really comes down to plane weight and likely budget. Happy flying, it's a good kit. Karl"

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Question 105: "Hey Karl, I am curious if the G-45 really needs the spring starter or can it be hand prop'd? I have seen some people use the spring starter and others modify the engine with an electronic system. I would like to do without the spring starter if I can as that would eliminate the weight of the starter and the special motor mount needed to use it as well as the cost. Thanks Jay"

Karl: "Hi, Jay. Call me a coward or what ever, but when considering the thought of hand-starting any of these gassers for RC, the more I go back to the fact that I like all my fingers intact, pal. I have worked in the auto repair industry now for just over 10 years and have had some close calls with hands and fingers. I figure there is a reason for these RC engines to have spring starters when the torque developed by these is enough to literally take off your hand, so if I were you, that's what I would consider. As for other folks using hand-starting method, start asking questions, observe the safety precautions they use, and make your best decision. Only when you have all the facts can you make an educated decision. Hope I didn't waffle that one for ya pal. Thanks, Karl. "

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Question 106: "Karl, I am in the planning stages for my first warbird, a Ziroli AT-6. Now I know that everyone loves the G-62 for this plane, and I like the simplicity of it, but I am looking for an add-on electronic ignition module for it. Any ideas ? Also, I want to add onboard start to it. Any ideas on that one? Thanks a bunch, Brian"

Karl: "Hi Brian, let me tell you about some other options for engines. This is a big plane at 101" w/s and true, there are many favorite engines such as the G 62, Q 45, and others. Let me "up-the-ante" and tell you about some radials that would fit inside the cowl. There is the RCS 215 from RC Showcase, and the 3W 256 radial from Cactus Aviation. They are both gassers and have electronic ignition systems. As to whether or not they have electric start or not I can't say. They have the power, look and sound that would wow any crowd that sees and hears it. Give it some thought. You just never know..... Karl."

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Question 107: "Karl I'm working on a Don Smith B17G. I bought 4 OS91 pumped four stokes. This is the factory pump system from OS. On the B17, the landing gear is right behind the firewall, so the fuel tank has to be located almost 1 foot away from the engine. My question is: Will these factory pumped OS91's continue to function properly a foot away from the tank? And, what is the maximum length of fuel line (fuel line routing considerations), that can be used? Michael"

Karl: "Good questions, Michael and thank you. There are a couple of things to consider here and I need to ask you about the placement of the tanks now. You said that the tanks have to be located a foot away now, on the inboard engines so where did you decide to locate them? If it works to put them behind the gear, you would need approximately 15" of hose to compensate and allow for turns, etc. You might be able to mount them further inboard---this might help with balance, but make it inconvenient for fueling. There are also some basic things to keep in mind where the physics of all of this is concerned. Now, if the spec's show an ideal length of say 8" of line assuming everything else being equal, then the inside diameter (i.d.) should be around 1/8". Let's say this is the hard and fast baseline. Well, if you move the source of fuel farther from the engine, fuel travels farther, and if you keep the size of the line the same, you might run into lean mix diffculties. If you leave the fuel line at 8", then you could conceivably make the i.d. smaller to compensate. Get the picture? Here's what it comes down to, the farther you set the tank from the engine, the higher the pressure you will need to overcome the distance. The reverse is true. The smaller the i.d., the higher the line pressure, the larger the line, blah blah blah. You can handle this simply by testing with different sizes of fuel line, or if possible, change the pressure settings on the O.S. pumps, if they have them. If the pumps are adjustable, you are in business, pal, just tweak these as needed until you have consistent engine temps (as I've said here before, with glow engines, usually the engine temp measured at the top center of the head is the best indicator as to how rich or lean it is running,...), the throttle response is good for all engines, and when you go full throttle the sound of all four should be close, and not sputter and smoke alot. If you or someone else needs a different kind of picture, think of the electrical needs in a car stereo. There is factory, then when you want to add more powerful speakers, deck, etc, you have to add an amp---or two or ten or whatever. The higher the demand, the higher the amp'ing has to be to get the signal there completely and clearly, savvy? Good luck on the project, Michael. Karl."

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Question 108: "Karl, On setting the timing on flywheel mags. On setting the timing at 28 degrees, how do you determine exactly where the magnets are in relationship with the armature, when the spark is delivered ? Some have two magnets and some have three. Jim "

Karl: "Thanks for the question, Jim. I don't know what engine you are referring to or what but here's what I can tell you of magneto ignition systems, which will essentially be a lesson in basics, and hope it will help.

When there is a reference to ignition timing it is always in terms of the crankshaft degrees, not the cam or anything else. That said, when the crank is coming up to near top dead center, the magnets are approaching the armature(s) and building an electromagnetic field around the windings. This occurs just before TDC so maximum exposure and field-building can take place. It's called coil saturation. At the designed timed moment when cylinder pressure is optimum (theoretically...) pressure and fuel has been introduced into the cylinder, the magnets rotate past the armature causing a collapse of this field and produces the electrical current necessary to fire the mixture. It is very similar to an electronic ignition but there are no moving parts to maintain like in a breaker point or aforementioned electronic system. The thing to do is time the magnets to pass the armature at the proper time---in this case, 28 degrees. As for the ones that have 2 or more magnets, this is usually what is called a redundant type of system, which will produce a weaker, second field and attempt to extract more power and efficiency from the air/fuel charge in the cylinder. Just make sure none of the magnets are still passing the windings in the armature when the piston is too far on its way down. The ignition has to happen just before TDC to make the most power since the force of the piston travelling up is resisted by the force of the exploding gasses in the cylinder, hence the term" power" stroke. Hope this helps you. By the way, the magnets are made of a ferrous metal for conductivity but should be readily visible around the circumference of the flywheel, just pinpoint your eyes on the armature and look for metal "bars" if you will, that appear to have been inset into the flywheel metal. Thanks for the question. Karl."

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Question 109: "Karl: I am presently building a Ziroli P 51 and have arrived at the engine installation. I have a 3W 75i which I had planned to put in the airplane, however, it appears that I will have to some substantial cutting in the bottom of the cowl to accomodate this large engine. Is there a better choice that would not entail butchering the cowl?? Thanks, Curtis "

Karl: "Thanks for the question, Curtis and yes, there is another choice(s). When doing a little research since i rec'd your question, it seems that Cactus Aviation (3W--) may still be your best bet. Now, Ziroli recommends an engine of 3.7 cid or bigger. The 3W-75 I think is too big. You might look into the sizes from 50-70 in the same line. Twins are out since the only twin that I know of at this writing is from Saito in the 200 Ti and it is too small. The other twins are opposed in design and you would still have to cut and butcher the cowl. The only other engines I can think of are O.S. Engines, I forgot to look into them but you can just as well. www.osengines.com Hopefully you will find the one with the right size, weight, power and price for this great warbird. Good luck. Karl."

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Question 110: "karl, i'm new to this so please excuse my rookie/newbie question. where can i find information on small, lightweight radial engines? something on the order of about 5-10hp? I'm working on a somewhat unconventional ducted fan uav design and a radial would be perfect. thanks alot in advance, Mike"

Karl: "Welcome to RC Warbirds, Mike. Be it known that here at our site, we don't consider any question rookie or newbie. As far as I'm concerned, the more honest the better because if you pretend to be more experienced at this than you really are or try to convey in your question, then I would be likely to assume this and give opinion or advise that might lead you wrong and put you down the path of disappointment in us, this hobby and so on, and we just don't want that now, do we? Onward. You have at least two places that are making beautiful works of art that happen to be called radial engines, and here are the websites---
www.robart.com
www.technopowerengines.com.

The Robart engine is a 7 cylinder glow fuel radial making an estimated 10 hp. and will swing up to a 32" prop with ease. It measures just less than 10" across and fits in many 1/5 scale cowlings with relative ease. The Technopower folks have 5, 7, and 9 cylinder radials, also glow, and produce an estimated 4-6 hp. They have them for 1/6 and 1/5 scale planes. They all measure less than 10" across if I'm not mistaken. I am always glad to answer any question, but when someone asks about radials, it's kin, you know what I mean? Since I was a kid, the sound of a radial has always made me stop and look skyward---always, because I still do it! I'll be here to answer more, but pay a visit to the websites above, ask some more questions and enjoy the planning, pal. Thanks and welcome. Karl."

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Question 111: "I have a Q52 about 6 months old. The engine runs like a champ as long as I don't do a snap roll. I can fly inverted the length of the field, do roll after roll, loop after loop, knife edge, even split S's and immelmans. But as soon as I do a snap roll the engine dies (EVERY TIME). Any Ideas? On the GSWarbird group on Yahoo, one person said he had the same problem and rebuilt his carb. I am no doubting him but, do have a hard time believing I need to rebuild a 6 month old carb with only about 15 tanks of gas run through it. Ron"

Karl: "Hi Ron. The Quadra's are pretty good, but regardless of how new, there can still be bugs in the systems. I have a friend that races large-scale rc cars and he has had to rebuild every carb on every new engine he's bought, and after only 6 or so tanks. Don't assume that since it's new, it'll work flawlessly---defies logic, I know, but trust me. What is happening is the snap rolls are so sudden that the fuel is being held back from the carb, so not inducted into the engine. Making sure the carb is working perfect is top priority, and perhaps looking into pressurizing the tank is another option. I have been to many airshows both for rc and the real thing and when you see the difference between an immelman and snap roll, there's a whole different batch of physics at play and that needs to be addressed. Also experiment with fuel line diameter (inside) this to affects fuel delivery. Hope this helps. Karl."

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Question 112: "Karl--- bought a used G23 from some one in RC Universe and said it was never in a crash. Problem is that at low idle, I see the blade and shaft wobble. Not at High RPM's. Also while turning by hand and after it comes down on the down or up stroke, it feels very tight. What do you think? Where should I send it to if I need a new crank. Thanks Jim"

Karl: "Hmm, doesn't sound good, James. If you were looking at buying a used car and noticed that the paint didn't match and you could see evidence of body work, wouldn't you be just a little suspicious if the seller said, "it' s never been in a wreck..." Duh. If someone has to say " it hasn't been such-and-such..." in order to sell a thing, then chances are it has been such-and-suched. Good eye you have to notice the prop shaft. It likely has been dropped on the prop at least, giving the seller the benefit of the doubt. this would have likely bent the shaft end or jammed the bearings so there is too much end-play. Both of these conditions will spell disaster for you and your plane, pal. My recommendation to you would be to contact the folks who market the Zenoah line ( they are a Czech or German engine....) and have them send you one, along with any other needed parts to fix it. It might cost a little more for the other parts, but trust me when you are in uncharted territory you will be thankful you have those other parts and don't have to wait for them in another shipment. Good luck and hope this is helpful. Karl."

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Question 113: "Inverted engine drawbacks? Hi, I have a question about mounting an engine in the inverted position. I am presently working on a Skyshark Fw190-A8. This is my first plane in which I have the choice on which way to mount the engine which is a (Supertigre G-75). On the plans they recommend mounting the engine in the sideways position. I am wanting to mount the engine in the inverted position so that any holes that are needed for the cowl are in the bottom and not the side. The plans state that mounting the engine in the invert position has some draw backs but doesn't really give any more information than that. I was wondering if you could expand on this for me as to what I might expect for the drawbacks? Thanks in advance for any advice and or knowledge. David "

Karl: "Thanks for the question, Dave. Lots of engines are flown inverted so I don't know what they might be referring to in that case. What I can tell you is that the problems should be minimal to deal with. You still have to ensure adequate cooling to the head, so don't shroud the engine too much. The fuel, as with most other things, follow the constraints of physics,which means that what goes up must come down. By this I mean that in most normal orientations for the engine, it is upright. This presents the least amount of problems where fuel delivery is concerned. The fuel can "fall" into the carb throat and into the crankcase (in the case of 2-stroke engines..) and obviously this is easiest. When you invert, the only thing to do is likely pressurize the fuel soas to make sure it gets to where it needs to be. In actual fact, I don't know anyone who had to do more than a normal amount of carb adjustments on the bench or at the field regardless of the engine's configuration. Hope this helps. Karl."

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Question 114: "Karl, I just purchased a Hangar 9 T-34 and am facing a decision of whether to top out on poswer and chance overpowering it withe a Saito 72 or dropping to a 65. I feel like I need something in between. Any advice you could offer would be appreciated, Thanks, Jeff."

Karl: ''Thanks for the question, Jeff. The T 34 looks like a great ARF trainer at least, and I think I have a great engine in mind for you, but let's look at a few important factors first. There are many schools of thought out there about engines and RC planes, ranging from the most conservative--which is to say staying to the smaller end of the engine size recommendations, to the other extreme of maxing out the size. The limiting factor of course is your airframe. If you overpower that, it will spell disaster real quick. The engine I think will work well for you here in a few ways is right at .60 cid and should make more than enough power for this plane. More later. The next thing is the prop. The prop works for airplanes as rear end gears do in an automobile---determines when the power is applied for most efficient results. A tall gear--3.23:1 to 2.50:1 makes for great highway cruising (top speed) but lacks torque for low speed launches (take-offs). The reverse then would also be true. Now, you want the prop to produce max thrust at the engines' max torque rpm. If you have a gargantuan engine you will overpower the airframe or without enough prop you overwork the engine because you aren't loading it enough, savvy? So, turn with me now to the text book Model Airplane News, Sept. '03 issue and refer to the article there on props. There we see a chart that can help us get a ball-park idea of prop using rpm and desired speed selections. The engine I think will work well is the Saito FA 60T twin. It looks scale, makes good power and sounds cool ( I just know that anything that's a 4-stroke just HAS to sound cool, don't you?...) It doesn't cost a ton of money and gives you a wider choice for props. Look into it and have fun. Karl"

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Question 115: "Hi Karl, I went thru your wonderful advise on the website. Just wondering if you can advise me on which warbird is most suited to the ASP 400FS 5 cylinder 64cc radial? A Vailly FW 190 perhaps? If not then could you recommend some other kits, plans and the generic wingspan/weight/scale I should be looking at for this engine? Regards, "

Karl: '' Thanks for your help in researching this and thanks for visiting our site. Pretty cool, huh? Yeah, I like it too. There are lots of choices for you with an engine this size, and they come from as many sources. The first thing I think you should watch is the wingspan and weight, for obvious reasons. Span no more than 90-95", weight around 18-23 lbs., to be on the safe side. You should put it in any plane that came with a radial in its original, full-size form. There are T6's (SNJ's) T 28's, biplanes, a veritable plethora of WW II fighter/bomber/attack/trainer planes that used radials, some Japanese fighters, many civilian planes---even tri-motors!!! as well as the ones you mentioned in your question.

The ASP line is built in the people's R.O.C. The parts may be harder and more expensive to get and replacement of the engine may take even longer or at least be more complicated. I don't know, because I have no experience doing business outside the US. Look into the engines from TechnoPower, O.S., Saito, they all have radials and they could be less hassle in the short---or long---run. You are on the right track here, with fitting the radial to the plane, props are another matter. Anyway, hope this helps, and good luck. Thanks again. Karl."

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Question 116: "Karl, Would an OS FF320 be enough engine for a Ziroli AT-6, or would I better to go with a Zenoah G-62? Thanks for the help, Brian"

Karl: ''Brian, dude, I feel really obligated to be true to the AT-6's roots and tell you the better choice would be the FR 450R3 radial by Saito. That engine is a beaut and fits perfect inside the cowl. I want to first say that in no way do I believe the engines you asked about to be inferior. The flat four from O.S. would admittedly be an interesting installation---both from looks and technical aspects. The G 62 is a proven powerplant and many RC'ers know its strengths. But really, Brian, the big Saito radial is likely the perfect choice, here. The plane came with a radial in real life, so, even though we don't have a scale, flying 18 cylinder P & W R2800, we at least have some radials to choose from, eh? Give it some thought and let me know what you decide. Karl. "

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Question 117: "Karl in your opinion what is the best 3 blade prop to use on a ST 3000 and also on a 3250 for a 1/5 scale spit. thanks n-brad"

Karl: ''Greetings, Mr Bradshaw. I think perhaps the best ones to look into for an airframe that size, if you are looking into scale is either Fuchs or APC. Master Airscrew has really good ones, so if scale size isn't a real concern, they will also be a good choice. Hope this helps. Karl. "

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Question 118: "I would like to have some info about adjusting the carburator of gas engines the proper way.
I'm having a 3W50i and finding difficulties adjusting the high and low needle right. Can you please give me some advice what procedure to follow and what to be looked (or listened) ad. I would like to have a reliable engine without having a constant fear of a "dead stick". Any info is welcome. Thanks on advance, Ronny"

Karl: ''Thanks for the question Ronny. Always bench-test the engine first before you mount it--well, assuming of course that you have already built the plane, with the engine in place so you can locate fuel tank, servos, linkages, etc. Remove the engine and test it for run-in. 2-strokers are a different breed since they don't idle like a 4-stroke engine. They are jumpier, sound like a motorcycle sort of. At least that's how they started. Lately there have been many improvements in this area so basically they run smoother. When you get the mixture set at idle, there won't be alot of smoke exept for what is normal for this kind of engine, and as you get used to the sound, you will be able to tell if it is missing or whatever. Try different settings and let the engine idle for several minutes so it can get used to the settings, then shut off the engine and check the spark plug. If it is totally black, like soot, it is still too rich. Using a laser or infrared pistol-grip type temp gun is a must, since a pyrometer isn't usually included with the engines.

The leaner the mix, the hotter the head will be. The richer, the cooler. Some friends of mine who mess with glow fuel engines like the head temp around 180-200 degrees. I can't say what the target temp should be for your engine, try asking Cactus. Is is them you are buying the engine through? If not, then simply follow the data trail to the manufacturer and ask them for the spec's. The high rpm settings will be achieved similarly. The leaner the mix, the higher the rpm but the easier it is to burn a piston or sieze it in flight. Again, there should be a low to moderate amount of smoke, sound like it is running smoothly and not missing, check head temp. Now for the kicker. Once you get it set on the bench, you will have to reset them usually when you get to the field since the atmosphere is different there than in your garage, eh? Work with it alot so you get to know it real well. Knowing what the engine sounds like in all scenarios is likely your best "adjustment" and could save you lots of time and money. If the engine doesn't seem right in any way, DONT FLY! better safe than sorry. Anyhow, hope this helps, just be patient, Ronny. Good things come to those who wait......for a little while anyway, haha. Karl."

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Question 119: "I have just started to build my B-25 (118" wing span) from Nick Ziroli plans with a pre-cut kit from The Aeroplane Works. I want to use radial engines for my B-25. Is this a feasible idea? Are there any engines out there that would fit the B-25 and give it enough power? Not to worried about the price, I am going all out on this airplane. I've tried a search on the internet, but got limited results. Any ideas would be greatly appreciated. Darrin Miller"

Karl: ''Darrin, you have come to the right place with your plans and questions, welcome. The Ziroli B25 is really cool, and safe to say the real plane is historical, at least. I don't know how far you got with your research on the web for engines, but I'll give you the website of a great operation in California and then answer your question. Their site is www.technopower.com These folks are sharp and will give you straight answers, as they have me over the last year or so. Yes, it is feasible to use radial power. The company I mentioned is the only one I know of at this writing that offers more than one engine, so if anyone out there knows different, please tell me. Onward...I think the best choices are either the 7 cylinder "B" series at 6 5/8" diameter and 31.93 cc (1.95 cid)----remember you have to have 2 of these....or the 9 cylinder "B" series at 7 1/16" diameter and 40.98cc (2.5 cid). They both swing at least a 14" prop, up to 16" so there is room to play with pitches and diameters---think 3 blades! Then there is a company in Canada that makes a killer hub and prop assembly for large-scale planes, www.soloprops.com Contact them and ask some more questions and see if they have what works for you. If you do good research, take enough notes, ask enough questions and don't let nay-sayers talk you out of what you really want, you will have an award-winning plane, for sure. If you have any more radial questions, let me know and I'll do my best to answer, hope this helps, Karl."

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Question 120: "Karl, I would like to know if the Saito 5 cylinder radial engine would work in the World Models Giant Scale Zero? Does it have enough power and will it fit in the cowl without cutting holes in the cowl? I have been trying to find a warbird that this engine will work in and am not having much luck. I am getting back into R/C after a 26 year absence and am amazed at the changes. Any input will be greatly appreciated . Thanks J. D."

Karl: ''J.D., thanks for the question and I will "Amen" that sentiment of being wowed at all the changes that have taken place in RC in the last 20 years. Just for your info, and not having the plane in front of me or any of the spec's on the World Models line, the beautiful Saito 5 cylinder is 8 11/64" wide, or 8.85". All you have to do if you have the model to measure is look at how wide the cowl is (keeping in mind the firewall is not the determining measurement for cowl size or potential engine choices since the firewall is usually slightly less diameter than the cowling....) and if your engine fits inside, PRESTO, you're in business. Tell you what, if you want some more help on this, reply to this e-mail and let me know of the all-up weight targeted, the cowl dim's and manufacturer's engine recommendations, this will help me better help you if you are interested. Thanks, Karl."

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