‘Scale’ Sounding Board?
When I decided to build the Spitfire I combed through all 130 pages or so of this thread (at the time) looking for modifications and tips. I adopted those I wanted and would do a few more after now gaining experience flying FT foam airframes. One of the tips I tried, but which was not needed since I made a battery hatch on top, was the addition of a simple flat foam piece to fill in the bottom of the cowl up to the nose.
I thought it would be a battery hatch so covered the rear seam with tape for belly landings, but only spot glued the front corners until a later time when I had the complete electronics package. Because I have an air scoop on the bottom of the power pod, I had to carve the front edge of this flat board of foam to make clearance for the scoop when the pod was being inserted into the airframe.
I think what I’d inadvertently done was to create a reed - like in a musical instrument.
Every flight so far when the plane is going fast - as in pulling out at the bottom of a dive - something is vibrating. But the sound is almost that of an engine when it flies past! If I weren’t worried about fatigue I’d leave it alone for the ‘scale’ sound. I think the foam board is the source of the vibration since it has a sharp edge and the middle is free to flex and move. I’ll find out next time the weather clears enough to fly...
Because my ESC was getting warm inside the pod, I’ve now moved it to the bottom of the power pod. Then more clearance was needed to slide the pod in, so I cut the foam board back a bit from the nose so it now has a flat edge, and Glued all three sides down since it will never be used as an access hatch. Next time I fly we’ll see if the sound is gone. If so, then it might be a safe addition to the design to add it back in. And the length of the board might be tuned for pitch. ? TBD
(Hope it’s not the tail feathers vibrating.)
Edit: It was NOT the bottom battery hatch. So now that you’ve read to this point, ignore all the above speculation. The sound is still there so now looking at the tagboard that forms the top edge of the nose. Also will check pushrods vibrating, they are long since the servos are mounted inside under canopy.
Further Edit: It was the tagboard on the top edge of the nose. The sound was reduced at the flying field by sticking masking tape to the front edge of the tagboard. The sound disappeared after gluing a former under the tagboard edge at the very front of the nose.