ORIGINAL: maynardrupp
I finally have my OS75AX running good. I am now using a Graupner 13.5''x8 prop. This seems to be smooth,quiet, and pulls good vertical. I really never understood why this engine wasn't making power. I cleaned the carb., eliminated the filter and richened it a little. This engine doesn't seem to respond to needle valve changes with RPM changes like most engines. I also hate the knocking noise that all OS 75AXs seem to make, but OS says that is normal. Now it is powerful. I do have to keep adding support to the flimsy belly. This plane does fly great though.
Got mine stripped down for the refurb project, and indeed the fragile fuse belly is in pretty bad shape. Amazing the plane was still flying after the tumbles it has endured at my hands, and I'm lucky it didn't end up as a pile of splinters. The encounter with the wind sock pole did a lot more damage than I realized, so the overhaul is occurring just in the nick of time.
Wings will be ready soon for recovering and I will post photos, then on to the fuse.
The biggest hassle so far has been digging out those pinned and glued hinges. I am going to re-do with CA hinges, but if anyone doubts the security of pinned hinges just try to get these out![>:]