I seem to remember Palmer saying he used screws to mount his engines (Fox 35) on his Smoothie and T Birds.  Would it be okay to use screws to mount an old Fox 25?  We often use them on the plastic radial mounts.  I am thinking long sheet metal type screws.

Hi Sleepy,

Well, I know that back in the day I used long sheet metal screws in the nylon R/C mounts like the Kraft/Hayes.

Just never tried it in a C/L model with maple mounts............

BIG Bear
RNMM/AMM

I hadn't realized that this was such a "hot" topic with Sleepy. Otherwise, I would have responded much earlier. I remember reading the OP, and well, just didn't think my reply (I did type something out) was worth posting.

FWIW, at this point in time, I would not expect any problems, except the potential for splitting the wood engine bearers might deter me from trying it. I would certainly do some test holes to see how big a pilot hole should be drilled. I would also use paste floor wax on the screw wrinkles to ease the entry, and would use socket head sheet metal screws, like Jim wrote.  The wax would also tend to seal out the oil soaking.  Steve

Another option. I have an old R/C biplane that I built in 82 and has been flown a lot. It has an OS60FS four stroke (the old one with the open rockers) that I drilled and tapped the maple mounts for 6-32 bolts. I did harden the threads with CA but I have had the engine in and out many times over the years without problems.

The trick with sheetmetal screws is to drill the holes the right size. I drill holes in a piece of motor mount and try the screws before doing it on the plane. The screws will make there own threads. Then for more permanancy, remove the screws and hit the threaded holes with a little CA and wait a few hours before mounting the engine. Works for me. If you get the holes to small it can split out the wood, if to big they won't stay tight or you can pull the threads out of the hole when tightening.