One of my favorite engine tips is those black composite plastic engine pads as sold by several manufactureres (Sig or Brodak).  They are ¹/₈" thick and ideal for profile fuselages.  Make sure you get the one without the built in offset.  Sig's are not offset.



I used one as a pattern to make an inlay jig for my router.  The jig is nothing more than a 4" x 12" piece of ¹/₈" basswood with a centerline drawn down the middle.  The jig is then either tack glued with hot melt glue or clamped onto the fuselage, making sure the centerline of the jig coincides with the centerline of the fuselage.  Then, using a ¼" or smaller bottoming bit in your router, machine away the ply doubler material.

You'll get a perfect fit to drop in the plastic C pad, your maple engine bearer surfaces will be trued up and your engines will never crush the doubler - cuz there ain't one.

I've gotten many compliments on my steady engine runs on my profile ships.  This is my little secret...   

Hi Steve,

Is it possible for you to photo the process that you use and post it here?
Especially the router 'bottoming' tool that you use..

Cheers, Peter O'Keeffe / Sunny Australia

Peter,

By a "bottoming" bit I mean only a bit which also cuts on the bottom of the bit - such as a hinge mortising bit shown here:

Is there an advantage to the "C" shape? I've been using 1/8" phenolic as a crush pad on the engine mounts. Glues and drills easily but does not connect the two engine mount beams like the "C" shape does.

I have no data to back this up but the "C" shape fixture does tie the upper and lower engine bearers together as a single unit so I would guess, "Yes" there is an advantage.  Plus they never get mushy from oil seepage.

Another tip for widening these mounts.  Scribe a line showing how much material needs to be removed.  Clamp the mount in a bench vise with the material to be removed sticking up above the surface of the vise jaws.  If there is a lot of material then cut off with a metal hacksaw blade using the jaws as a guide.  Then take a metal file and file down to a smooth finish.

Why not use the pads with the off set?
That are the only ones I have.

Thanks

I find the offset angle is too much.  Virtually all of my profiles now fly with zero outthrust.  On the flat pads you can stick a washer under the engine lugs if you need a little outthrust.  Hard to remove outthrust with pads with it already molded in.