I have been spoiled with three Hangar 9 ARFs where the engine mounting blindnuts have already been installed. I bought this cheapie Edge(seems to be a nicely fininshed-out kit) with NO instructions on how and where on the firewall to mount the 2-piece engine mount. To make it even more complicated, the plane has a cowl. Help?!!

Draw the firewall on a piece of paper. Set the cowling over the diagram of the firewall and properly locate the cowling by viewing thru the nose openings. Use a make shift plum bob thru the engine crankshaft hole in the cowling to determine the location on the firewall. Use this location to determine where the engine mount will be on the firewall drawing. Transfer these locations to your airplane's firewall.

pmw

Are there center lines marked on the firewall? If so, it should be no problem to locate the mount location and drill the mounting holes. If not, you'll have to figure out engine offset, etc.

Yeah I regularly assemble planes like this.

I do similiar to PMW...

However here is what I do.

- I first determine the engine to firewall distance and temporarily place the engine on the mounts using clamps.

- I then check to make sure that the engine is perfectly square with the mount using T squares, and at the proper distance.

- I drill out the engine mount, engine mounting holes as needed then affix the engine to the mount.

- I then place the engine and mount on the firewall, with the fuselage of the plane pointed straight up

This is easiest to do BEFORE you put the plane together.

- I then sight straight down the engine shaft line to align the shaft ( where it hits the prop back plate ) to the scribed lines on the firewall, if they are present.



- If no lines are present I will start on the cutouts for the cowl, so I can get the cowl over the engine, minus the muffler and/or carb if needed.

- I measure and mark the center of the firewall and draw the intersecting lines.

- I will then sight down the engine shaft and make sure that shaft ( where it hits the prop back plate ) aligns to my lines. This will properly offset the base of the engine.

- I'll apply a drop of CA or use a clamp to hold the engine & mount there, until I have a chance to mark the desired locations for the motor mount holes using a GP Dead Center Hole locator.

- Once done I remove the engine & mount, drill the holes, harden them with CA, and install the blind nuts using any of the standard blind nut mounting tricks...


It may take a little longer than a pre-done firewall, but you have far more flexibility in engine mounting if you can do it yourself.

e.g. I can do 45 degree head down ( or up ) mounts this way, which hide mufflers, etc.