If you have been following along with this extended Workshop Build-Along series, you know that from the start, I designed the Sopwith Camel around the Zenoah G38 gasoline engine. One of the great advantages of scratch building, is that you can from the start workout everything so you can use the engines and equipment you want too without having to “re-engineer” things. All your parts fit.
(Above) here’s a section of my plans showing the engine, firewall and the fuel tank positioning.
If has been about 16 months from the time I started the CAD drawings for the project and last weekend I accomplished one of the more important tasks involved in a new airplane project–that being test running the engine. I have learned from experience, that it is not a good idea to wait till you are at the flying field, (with all your club buddies around), to try and setup and adjust the engine.
(Above) Here’s my old reliable G38. It is more than 15 years old and is the older magneto equipped type.
In the pit area or the pilot station at the field is not the time to rush things. So, my procedure is always to gather all the equipment that I plan to use in the model and assemble it on a test rig. So for the Camel, this involves mounting the engine and muffler on a suitable structure and then setup the fuel tanks and any other parts like the throttle linkage and fuel line fittings.
I also decided to use the new RotoFlow Fuel System from JL power Products. This is an entirely new fuel tank concept and after using the tanks in several models, I have found them super easy to install and very reliable. They are also completely maintenance free, which is great for a lazy guy like me. As you can see, I made support brackets to support the tank inside my model.
(Above) As you can see here, I have replaced the original carb. with a larger, choke equipped one from a Quadra 50 engine.
(Above) here’s the engine installation in the Camel. It is soft-mounted to the firewall which is recess into the fuselage.
For my test run, I simply supported the servo end of the throttle linkage with a rubberband so I could adjust the throttle settings and set the linkage length for what ever power setting I wanted. Usually I also install the throttle servo and control the engine with my transmitter and airborne radio gear. I make the test box from heavy pine boards and screw them together with heavy-duty screws. I also screw the box structure to a secure base like this 2×10 board which is also screwed to the sawhorses. Do not screw your test rig to your wife’s picnic table!
I was very pleased to find that the G38 fired right up without any issues and I only had to tweak the low-end needle valve a smidgen for a good reliable idle and smooth transition to full power. Just the way I like it! Whenever I can, I like to use an electric started (Sullivan DynaTron), when testing engines. Once the engine has warned up for a few minutes, its throttle response is very good. I also installed a Zenoah velocity stack but this is more for just containing unburned gas that gets siphoned out of the carb from the airflow, and less about increasing air intake.
Of course, you should always check all the engine bolts and screws to make sure they are tight and ensure that your propellers are properly balanced. I use Xoar and Falcon Propellers so this is rarely and issue, these props come out of the package balanced and ready to bolt into place.
Hope these tips help you be successful with your first test flights.