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Building Tips and technical articles. => 1/2 A building. => Topic started by: Jim Carter on September 17, 2020, 10:08:17 AM
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Greetings! Folks, I built a reduced sized, semi-scale, control line Grumman Widgeon from a set of RCM plans. I successfully mounted a couple of perfectly good Brodak .049's. However, I believe I need a bit more power for successful flight since, with the engine running near peak, it wouldn't pull itself off the cradle. It's flying weight is quite realistic at only 2# 5.8oz, dry. I know I probably should just buy a couple but I just don't have the expendable funds at this point in time. Would anyone possibly have a couple of the Norvel .074 engines that they might consider trading or even loaning out for a brief time?
Jim Carter
Titusville, FL.
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Our experience at the Tucson 1/2A multi-engine CL scale contests has shown that for two Norvel .061's, a wing area of around 200 to 220 sq in and a weight of around 30 oz has been successful. Slightly smaller, say a max of 200 sq in with two TD .049's at around 25 oz also works. Those numbers allow the model to remain airborne with only one engine running
Your weight of 37 oz is asking a lot of those Brodak .049's unless you have an area of more than 250 sq in. Larger engines would be a solution. How big are those 3-blade props? Assuming they are 5" diameter, it looks like the span is around 35 or 36". That may not give the wing area to carry that weight with the Brodak .049's. If the span is less than 35", there will not be much area to carry that 37 oz as a scale project. Just saying.
Nice looking model of an interesting subject.
Keith
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Are they the new or old Brodak engines? If the old design, they are easy to improve!