engine pads

[Dudley Lang]

I am coming back to control line after 35 years.  In the 60's, I bolted the engine directly to the wooded motor mounts.  I now read in the forums about aluminum engine pads.  I assume that  a more solid mount makes for a better engine run.  On a profile plane, it appears that you simply bolt the pads to the plane and then mount your engine to the pads.  My question concerns full fuselage planes.  Do you have to relieve the wooden motor beams so that the pads fit flush with the top of the wooden beams so that thrust line is the same as mounting directly to the wooded beams and so that the cowl and spinner match up.  If you have to relieve the wooded beams, what is an easy way to do this.  Am I on track not.

[Bill Heher]

You are on track, and yes you would need to relieve the mount beams on a full fuse ship to keep the original thrust line.

Easiest way is to use a router before the hardwood mounts are assembled into the crutch or fuse formers. If the mounts arer already installed you will need to get in tehre with a dremel or similar tool and grind away.

[Leester]

Obviously study your plans, there are kits and plans that are designed with the use of engine pads.

[Ted Winterman]

       Dudley,

       If you notch out the mount for a pad, the sharp corner of the cutout causes a
stress riser and weakens the mount. The thrust difference doesnt really make a difference
that I can see.
       I use a 1/8th inch thick x 3/8th x 1 1/2 inch carbon fiber pad. It is lighter, stiffer
and stronger than what you have in mind. I used to use 1/16 inch stainless steel but
I like the carbon fiber better.

       Ted            

[Ralph Wenzel (d)]

You can also get good-quality phenolic pads in 1/16" and 1/8" thickness from www.controllinecentral.com - LIghter than alumnum, and perhaps just as useful in spreading the load. If you do use aluminum pads, be sure it's a hardened alloy, which won't turn into a "banana" when you tighten the engine bolts.

[Bill Little]

IMHO,  engine pads serve the purpose of keeping the engine from sinking into the mounts by spreading the load over more area and with a harder surface.  This helps keep the engine bolts tight longer, and we do not get the "foot print" of the engine in the maple.

I have found that a lot of models have the maple mounts below the top edge of the fuselage and that by simply raising the mounts to the top edge allows the aluminum, or other material, to be used with no other changes to the plane.

[Bob Reeves]

Well here is my take... If you are building the airplane 1/8 inch isn't going to change anything, just build the nose and cowl to fit. I use regular home improvement store aluminum stock, buy the 1 1/2 to 2 inch wide X 1/8 and cut strips off the end with your band saw. I set up a jig and cut a life time supply several years ago, still have 20 or 30 pieces and have used them in everything.

On several of my airplanes I mounted the aluminum using standard blind nut mounts with the holes close to the ends. Drilled the aluminum for the engine and mounted the engine with counter sunk screws from the back side of the pads and lock nuts. With this setup all I need to do if I decide to change engines is make new aluminum pads drilled for the new engine. This has saved many holes in motor mounts, I have had 5 different engines on the TwistMaster over it's life with only one set of holes in the motor mounts.

[Bill Little]

Hi Bob,

The bolts and nuts approach is great.  I have used that recently and it works, no problems.  I didn't have flat head bolts so I grooved the maple mounts slightly.  Changing engines takes only minutes.