Put a Radial Engine in your Sopwith Camel

7/9/2007 by Jim Booker

Copyright:© 2007 Horizon Hobby, Inc.

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Hangar 9 Sopwith Camel Equipped with a Saito 3 cylinder engine

When Hangar 9 introduced the 60-size Sopwith Camel ARF World War I warbird, it seemed just too good to be true. Here it was, one of everyone’s favorite airplanes—that is dear to the heart of model builders everywhere. But it was always a difficult project to build until this new ARF model was released. Now there is no reason to just dream about flying a Sopwith when you can have one ready to go in short order, thanks to Hangar 9. Coincidentally, I had a chance to do something most of us just dream about—put a Saito 3-cylinder radial 90 into the Sopwith and actually fly it! And since my picture is on the box, I thought I’d better get going on this project.

The Saito 3-cylinder radial four-stroke engines create dreams of WWI biplane models, but reality sets in because these airplanes are usually difficult to build and there haven’t been any ARF models available.The Sopwith sans cowl, showing the Saito engine. The Saito 90 3-cylinder engine is a beautiful piece of machinery, and it just seems to be designed to fit in the cowl of a Sopwith Camel idling at the end of the runway, waiting for an early morning sunrise to lift off for another dawn patrol flight. Hangar 9 has brought us the Sopwith Camel ARF and the Saito is ready to go. However, for most of us, that 3-cylinder radial might be more than our modeling budget can afford. So most people will install a single-cylinder engine and just have a great time flying the Sopwith.

The Sopwith Camel has been a popular RC model since it was introduced and many people have assembled the ARF kit with excellent results. The color scheme is very realistic looking and contributes to the outstanding appearance of the Sopwith cruising around the field. Like the original, this Sopwith Camel is modestly aerobatic and capable of most maneuvers that an RC pilot would expect of it. Certainly, the model performs admirably with a .60-size two-stroke engine, but I have the opportunity to install that wonderful Saito 3-cylinder engine in the big round cowling for swinging a large scale-like propeller to lend additional realism. This is truly a dream model. But there is more. How about a video of the model with engine sound to let you enjoy this model with almost as much fun as I am having? Well, we did it and you have to see and hear the results. Now, this is fun!

First a little about the engine and airplane assembly. The Hangar 9 model is very nicely done and will only take a few evenings in your shop to be ready to fly. It includes very nice, but easy to install, details such as the flying wires and machine guns. This is definitely not typical of the more-difficult-to-build models normally associated with RC WWI airplanes.

A big question comes up right away. Does the Saito 90 fit in the cowling? Let me tell you that if I didn’t know better, I would say it was designed for that engine. It fits, and the factory-supplied Saito engine mount provides the perfect spacing for the propeller in front of the cowl. As you might expect, you will have to drill the four holes in the firewall for the Saito mount. I elected to use a remote multi-cylinder glow driver to make starting easier and ensure a reliable idle (waiting for that sunrise). I used two Saito flexible exhaust pipes, plus one of the supplied Saito exhaust stacks to get the exhaust out of the cowling. This requires some minor clearance in the bottom of the cowl for the three exhaust outlets. Be sure to connect the exhaust pressure line to the fuel tank. I also would recommend using a remote fuel filler cap to make it easy to fuel the model. This pretty much finishes the modifications necessary to fit the engine in the model.

Using a normal 60-size engine, A closer look at the Saito engine mounted to the firewall. it is necessary to add weight to the nose of the Sopwith as explained in the instruction manual to achieve the correct center of gravity. With the Saito 3-cylinder 90, the model will balance very close to the manual’s specification with out any weight. Please make sure your Sopwith balances correctly and add weight if necessary. This model has so much wing area that the nose weight will not increase the wing loading any significant amount.

It is a good idea to start the engine and make sure all of your connections are working properly for the remote glow driver and fuel system. This is a good time to fine-tune the needle valve settings so that the model is ready to fly without further tuning. We took a number of pictures of the model to show the installation of the engine and give you some ideas of how nice this airplane looks.

Shot of the wing struts.
Shot of the pilot and guns.

Let's get the engine running and see how that Saito 3-cylinder sounds on the ground and in the air. Here is an audio clip to give you an idea of the sound of the Saito engine.
I used these initial tuning runs to get familiar with the operation of the engine. After a bit of needle valve adjusting, it was running as smooth as a person could imagine. Fuel consumption seems to be pretty much normal for a 90-size engine, but the sound level is very low compared to similar 2-stroke engines. This was also an opportunity to complete a ground range test on the radio and confirm all the control surface directions before the first flight.

Really, we are ready to fly—but it is time to take a few pictures of the model. This is a very nice and popular model, so your friends are going to want to see pictures at the next club meeting. Now it is ready to fly. Time for the takeoff. See our video to experience the flight of the Sopwith and hear the sound of that 3-cylinder.This is too much fun and I really didn’t want to land.

*These videos require at least Flash Player 8.Download the latest player here.

Speaking for Horizon Hobby, I hope that you enjoy seeing our model fly and that you will build a Sopwith Camel yourself. It is one great-looking model in the air and the Hangar 9 ARF kit makes it possible for anyone to experience the fun if offers. Send us a note and let us know how yours looks.

In the meantime, I will be at the field very early on Saturday morning to take off with the morning sun and dream about that 1917 dawn patrol.