Malcolm, you will likely get several responses on your question and these could differ significantly from one another. I suggest that one should err on the side of caution and safety with this model. The fuselage compression buckles some have experienced is as much a function of weak fuse sides as it is vibration induced resonance. As such, your Hacker set-up will experience less of the latter.
But since weakness of the fuse sides is the other variable of that equation, it's a good idea to reduce the free, unsupported fuselage span in the longitudinal direction, by adding at least two more fuse formers to go along with the one in the tail. Then the formers can be tied together with a pair of 6-8mm square balsa longerons glued to the fuse sides, at the formers' mid section.
I have written about this approach before as alternate to the crutch bridge, since this will open the center area of the fuse. This is similar to how airliner fuselages are designed. FWIW
MattK
ORIGINAL: Malcolm H
David,
When you put in the tray to replace the cross brace did you raise it up in the fuz to come close to the orginal cross brace position or did you leave it down on the balsa rails already fixed in the fuz?
I am powering my Impact with a Hacker setup and although I am fitting the rear bulkheads I am not keen to install the horizontal crutch as it does restrict access to the rudder pull pull setup. Does anyone have an opinion if the reduction in vibration etc of the electric setup reduces the likelyhood of a failure without the crutch?
Also can anyone running the Hacker setup give details of their air cooling outlets? The manual gives a suggested outlet size on the fuz bottom but suggests it could be bigger for the Hacker setup.
Thanks in advance.
Malcolm