I have a two piece engine mount. After drilling the engine mounting holes there is no right offset. Putting washers under the left mount does not seem to change the offset. I was considering sanding/filing an offset in the back of the mounts (where they attach to the firewall). Re-drilling is not an option. Any other ideas?

Regards,
Jerry

Putting a washer between the left side of the mount and the firewall will definitely give you some angle. If it's not enough, add more washers

MinnFlyer,
Putting washers under a two piece mount does not work the same as under a one piece mount. All that happpens is that the mounting holes become misaligned. The mount that I have has two beams that are not connected as shown in the picture that you put up.

Regards,
Jerry

Jerry, it will still work, just mount the engine first.

Mike,
Thanks for the quick responses. I'll mount the engine and try it.

Regards,
Jerry

if washers won't give it change, you can make a shim out of plywood, but it's a bit more work as you have to sand the angle into the ply which should be the same dimensions as the back of the mount overall.................what kind of mount is it?
Great Planes 2 piece mount will allow the use of washers, but i have seen a couple of 2 piecers that would not shim out with washers.............

Summerwind,
The mount came with a Lanier ARF. I looked and found a mount that is close to what I have and have put a pic up.

Regards,
Jerry

OK i see that it's not one of those that tries to flatten out when shimmed.................like Mike says, use more washers. you'll surely get some angle change, or better yet as you already said, sand down the side you want to give the angle.......

But sanding it down will make it weak.

You could also just glue a strip of 1/8" ply to the back of one, and then sand the plywood to the thickness AND angle

Why not fly it first to see if it needs any offset?

Pat Roy,
Something that occurred to me, but I'm pretty new at this and the older club members would probably give me a lot of grief if I didn't put some offset in.

Regards,
Jerry

The advantages of starting with zero-zero offsets is that you can later adjust to exactly what it needs (if anything) rather than have to over come too much of something built into it. Tell those old Geezers (of which I'm one, btw) to start thinking with accuracy and precision instead of estimates. You're going to fly it the first few times without the cowl anyway, right?

Pat Roy,
There is no cowl. It is just a trainer that I am bashing to put on floats. I will probably try it w/o any offset to start. If I don't put right offset into it and crash - I'll never hear the end of it!

Regards,
Jerry

I know where you are coming from-just tell them you used trig and calculated the offset at 1.75 degrees right and 1.25 degrees down thrust. That ought to keep them busy long enough for you to figure out what is actually needed.

Jerry
It might help if we new what type plane you are working on. On the test flight with out offset you can compensate with rudder trim to start.

I you have a table saw you can make a jig that will cut a pice of thin hardwood at any angle. Mount it to larger piece with adhesive like rubber cement and saw proper angle, sand and you have it. Some pieces can even be sawn with miter gauge that table saws have. I have done this for profile and conventional mounts. I wanted to use some kind of plastic but knew it would have to withstand intense vibration and some heat. Some company (J-tec, I think) makes a mounting plate assortment out of plastic but it won't hold up that well because the vibrations cause it to crack. A belt sander with a miter gauge will work also but I don't have one.

Hi,
Try Tower Hobbies and search-Ernst,thrust plates.
Worked for me.
Good luck,fredsedno

fredsedno,
That seems to be just the ticket. Thanks for the post.

Regards,
Jerry