One only needs to assemble the cowl to get a good idea of the size of the kit. It s about 5 in. wide. That means 11 or 12 in. props won t provide very much thrust as a great deal of the prop-wash will be blanketed. We should then eliminate all but the very best .60 s running on tuned pipes and high nitro fuel. ( A US $300 value ,at least! )
The aircraft is also extremely light as it is entirely built-up . A 1.08 powered version can weigh as little as 8.5 lbs and even less for .60 powered aircraft. Most models (pattern airplanes are an exception ) with this low a wing loading tend to be very gust sensitive and difficult to stall, making snaps, spins and flights in windy conditions laborious. Simply adding weight may solve the problem but the admittedly average vertical performance afforded by engines of this size will be reduced.
The problem is to select an engine capable of turning 14 in. props in order to produce good vertical performance at an airframe weight of about 9 lbs. and not spend much more than US $300. OS and YS FUTABA both make great 1.2 four cycle engines that can adequately power this aircraft. For those of you who aren t four cycle fans, Webra makes a 1.2 two cycle engine that may be worth investigating. Tuned pipes for 1.08 owners may be an option.
In order to be cost effective when purchasing any engine one should consider two points (other than price) : 1) the engine should afford your present project better than average performance and 2) the engine should be considered for use on future projects.
So if purchasing that large engine for your Extra gives you nightmares, take a look at the performance of Mark s machine. The difference between frustration and awesome performance may be just a few dollars.
By Colin Chariandy