Question for Ken Cook -- CG location

andrew Fri Jun 24, 2022 11:13 am

Ken -

In re-cataloging some plans, I had opened the Shark 15 by Lew McFarland (we were in the same club in Lexington) and noticed that the CG seemed to be well forward of what I would have expected. Can you (or anyone else) help me understand why it's so near the LE. I believe Kim flys a Shark 15 -- maybe he will jump in here, too.

andrew

Ken Cook Fri Jun 24, 2022 2:21 pm

Andrew. I've never built a Shark. I built the Dolphin ( .35-40 )size and it was a real sweetheart. My thoughts would be the longer nose moment. I would think that it's quite sensitive to fore and aft adjustments because of the longer nose and tail. I believe the Shark is a constant chord wing whereas a sweptback wing can offer some funny CG locations. To me, I believe the CG of the Shark is slightly ahead of the first leadout, to me this would be where I would balance the plane. Now the next hurdle to overcome is the engine type. I don't know how much is needed if a modern muffled .15 is used. I know this can really taxi old designs.

**Cribbs74** Fri Jun 24, 2022 9:46 pm

I can say for sure that a Fox .15X works well on the nose. I initially used a Fox .15BB and it was way too nose heavy. This was a built one that I received so I just threw an engine on. Just build it per plans and use the engine with the most pep with the least weight.

Kim does fly a Shark .15, but he uses an Enya .19 for power.

Kim Sat Jun 25, 2022 5:05 am

Yeah,
Mine was/is a nostalgia build to use my Uncle Wayne's Enya .19, which he used to power his Shark in the 1960's.

I did put a considerable chunk of lead in its tail to tighten things up, but this was to counter the solid rubber "toy truck wheels" that came with the original kit. I removed the lead when I started launching it gearless from a stooge.

I'm not a pattern flyer though, so my analysis is just that of a sport flyer who is happy to miss the ground with my assorted hi jinks.

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