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Bud Nosen 104" P-47D Kit Build Question

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Bud Nosen 104" P-47D Kit Build Question

Old 12-06-2023, 11:46 AM
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Real2You
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Default Bud Nosen 104" P-47D Kit Build Question

Hello, I picked up a Bud Nosen P-47D kit that was partially built. I plan to complete the build and was wondering what size engine I should use. I have never built anything this big before. On the box it says its a 22lb. plane. I saw on a different thread and the guy was going to use a DLE 120 twin(he called it a flat twin). Is that a proper size motor for this build? Thanks.
Old 12-06-2023, 07:18 PM
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LLRCFlyer
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Default What size engine?

22 pounds for a 101" span scale airplane sounds a little too light. My 90" span Clean-Cut sport pattern plane has all-balsa construction similar to the Bud Nosen P-47D and weighs 20 pounds fully fueled. It has unlimited vertical capability with a 20 year old 53cc Brison engine turning a 20x10 propeller producing about 26 pounds of thrust. Is there enough of the kit already built that you could make a good estimate of the finished weight? If so, all you need to get great scale type performance, but with greater than scale vertical performance, is to have a thrust to weight ratio close to 1. The real P-47 Thunderbolt was a great fighter with a thrust to weight ratio way less than 1. Since the Bud Nosen P-47D is not intended for 3-D, a thrust nearly equal to its weight should provide sparkling sport pattern style performance. My single cylinder DLE-55RA turning a 22x10 propeller produces over 30 pounds of thrust and would fly your P-47D. The DLE-120cc twin is listed at 12 hp and 58 pounds of thrust. It turns 26" to 28" diameter props and is intended for 30 pound 3-D airplanes designed to hang on their prop and hover at half throttle. 58 pounds of thrust on a 30 pound airplane would be extreme overkill for a non-3D airplane. Assuming your plane is less than 30 pounds ready to fly, I would suggest a 60cc to 70cc engine nominally producing 6 to 7 hp. I recommend opposed twin cylinder engines when over 55cc displacement simply because they run with much less vibration than single cylinder engines. A 60 to 70 cc twin cylinder gas engine should be more than adequate for weights between 25 to 30 pounds. Possible choices would include the Desert Aircraft 70cc Twin which is a top rated engine but is also the most expensive at $859. DLE makes a 60cc twin rated at 6 hp and 33 pounds of thrust and costs $629.95. The RCGF Stinger 70cc twin cylinder 7.4 hp engine is also a lower cost ($529.99) option and the reviews say the thrust is around 34 pounds.

Good luck
Old 12-06-2023, 07:48 PM
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Real2You
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Thank you for your reply. The weight of the plane is probably heavier as it seems heavier to me. I was going by what it says on the box. The fuselage and the wing are both about 90% complete so I should be able to weigh them and get a pretty good estimate of actual weight. I wasn't sure as to how much weight finishing and painting will add as I have never done or worked with anything other than monokote or other iron on material. I stilll need to do some research on a lot of things to get it ready to fly. Like servos...I'm assuming a standard size servo is to small? The 120 twin does seem like overkill for the type of flying I'll be doing. I will look into some of the engines you suggested. I know the guys at my flying field like the DA and DLE engines. I have a RCGF Stinger 40 twin and a couple DLE engines but I have yet to run them(to many airplane projects and swap meet finds) that have taken away from some of my other builds. I appreciate your advice. Thanks!
Old 12-07-2023, 07:24 AM
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You are correct that standard size (nominal 40-50 ounce-inch torque) servos are too small. I would use one servo on each control surface (5 servos + throttle, 7+1 if installing flaps). Since the P-47D does not have the huge control surfaces of a 3-D plane, servos rated for at least 150 ounce inches (except for the throttle) should be satisfactory. Some people also install a servo for the choke if a manual choke rod is too hard to reach or is too ugly. This size servo is going to weight around 2 ounces each. Buddy RC carries the KST servos which are good and reasonably priced. The larger servos pull more power, as much as 5 amps or more if stalled. The typical Futuba battery connector is only good for about 5 amps. If multiple servos are running, it can easily exceed 5 amps and result in voltage drops that can brown out the receiver. A typical installation for gassers bigger than 35-40 cc would be to use two LiFe batteries (3000 mah in your case) and switches with larger cables and plugs and use a power expander (distribution) board such as the Smart Fly Competition 12 Plus (the Plus version includes the necessary optically isolated ignition kill switch which isolates the ignition RF noise from the engine). The Smart Fly Competition 12 has two Deans T-plug connections for the batteries. It automatically switches to the battery with the higher voltage in case one battery fails. It also buffers the receiver voltage to a constant 5 volts while routing full battery voltage to the servos. You will also want at least one (and preferably two or three) satellite receivers. If you are installing retracts, include the weight for those too. They are heavy. You will want a 24 ounce fuel tank (1.5 pounds). Lots of weighty things to consider for the final weight. Larger planes can fly well at higher wing loadings. Obviously, the lighter the better, but your P-47D should still fly well at 32 to 35 ounces per square foot wing loading. As for engine brands, all of the engines I recommended are good. I don't have a DA engine because of the price, but one of my flying buddies has a DA-70 twin and it is absolutely sweet. My DLE-55RA runs strong and is reliable. I have RCGF Stingers in 15cc, 20cc and just ordered a 26cc. I would get the DA if money were no object, but as my wife says, I'm too cheap to have fun and would probably get the Stinger-70. As for finishing materials, if using UltraCote or Monokote, just add on the weight of how ever many rolls of covering will be needed. Fiberglass /finishing resin/paint finishes would probably weigh about half again more. Enjoy the build!
Old 12-07-2023, 09:14 AM
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Wow I hadn't even thought about the amp draws and other electrical type decisions I would need to make. I'll take all your advice, I appreciate it. Thanks!
Old 12-07-2023, 03:15 PM
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A good G62 flew all the typical Nosen warbirds very well...
Old 12-07-2023, 05:23 PM
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I looked up the Zenoah G62 specs. It is rated at 4.75 hp and weighs 82 ounces (5.125 pounds) including muffler. It turns a 22x10 prop at 7,200 rpm (about 30 pounds of thrust). Foodstick is correct in stating it would fly the P-47D. The G-62 has a magneto and therefore does not need an ignition battery, however this also requires another servo to ground out the ignition to serve as a kill-switch. G62's were reasonably smooth for a single cylinder engine, but will never be as smooth as a twin cylinder engine. The G-62 weighs 1.127 pounds more than the RCGF 70T, which may or may not be beneficial depending on how the CG turns out. A shorter nose moment on most radial engine airplanes can cause the model to be tail heavy. The RCGF Stinger 70cc twin weighs 3.98 pounds including ignition and mufflers.

The down side is, the G62 engines are discontinued, but you can still get parts. I found a new G-62 at B&B Specialties for $459.95 without muffler, engine mount or throttle linkage (https://www.bennettbuilt.com/shop/En...h_G62_CID.html). It would be well over $500 by the time you add those items. (For $449.95 you could get a new DLE-55RA which weighs 3.42 pounds and makes 5.5 hp.) Considering the
Old 12-10-2023, 08:42 PM
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I'll probably just go with a Stinger or DLE 70 twin. As I get closer to completion I should get a pretty good idea of how much it will weigh and that should also help me in what engine to use.

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