I goofed. When I was building the balsa cowl I was less than 1/8" too long. When I put the spinner backplate on it rubs. The front of the cowl has a 1/8" inch plywood ring in the front, so I can sand it down but just a very little. Is there some kind of spacer I can put between the drive washer and the spinner backplate. Or is there another option. I would hate to remove the engine and put spacer behind the motor mount. It is very difficult to get to. This is a magnum 180 4s.

Putting a spacer behind the mount is the best solution, but you could TRY putting a plywood ring behind the backplate. The ply should be soft enough to allow both the backplate and the thrust washer to bite into it.

If the backplate is smooth, you might want to glue a sheet of sandpaper to the front of the plywood.

I did put a piece of 1/8" lite ply that I sanded down and really torqued it so the teeth on the drive washer and spinner backplate would make an indentation. Do you think I should then put CA on the plywood to harden it. Taking if off of course before I put the CA on. I did cut the plywood in a circle to match the drive washer.

Irish,

Like it or not, the easiest fix is to put some washers behind the engine mount to move it forward the required distance.

Hogflyer.

CA would harden it and also fuel proof it. Now that it has been "formed" by the initial installation it would probably be a good idea IMO.

.... OR... you can often redrill the engine mount holes to move the engine forward a bit.

This will have little affect on the C.G. if any, as you'll only be moving the engine forward a tiny amount.

At worst you may end up having to buy a new mount, but this is easier than having to deal with other options...

It is better to have the mount firmly affixed to the firewall instead of on washers, so that it spreads lateral loads out over the entire wood surface.

It won't be possible to drill new holes so close to the old ones.

If and when you ever need to remove the mount, make a plywood square a little bigger than the engine mount's footprint with through-holes for the screws and place that between the mount and the firewall. That's a much better fix than using washers.

Here is a couple of pictures to show what I am dealing with. The bottom bolts on the mount are very hard to get to.

Aw hell, that's easy.

File out some holes in the front plate so you can get a screwdriver in there (Fig. 1)

Then make a plywood plate like in Fig. 2

Loosen the mount screws just enough so that you can slide the spacer down between the mount and the firewall. Re-tighten the mount and, Voila!

Goirish,
Just sand down the spinner plate on the right side directly behind the spinner. There is enough wood there to sound down the spinner plate so that it matchs the angle of the spinner.

Ken

Depends upon the mount and distance.

Someone here posted a great solution for aluminum mounts, where you can friction weld a plug using nothing more than a tap & die set, a piece of aluminum stock and a drill.

They suggested putting threads on the stock and using the drill to screw it into place at high speed until it breaks off... effectively friction welding the aluminum plug in place.

Apparently you can then redrill the mount after this is done with no ill effects.

Yea, but this is a composite mount and he only needs to move less than 1/8"

I'll be right over MinnFlyer.

Ken
Not sure what you meant by sanding down- The plywood spinner ring. It is only 1/8" thick.

Great, if you leave now, you can be here by morning.

Actually Ken has a point (But if he wears a hat, no one notices)

How badly is it rubbing?

You could sand half of that ring away and still be safe.

the spacer that I used is 2.17mmthe ring on the the front of the cowl is 3.19mm

Ok, go back to doing it my way

Goirish:

1) The shim behind the mount proposed by MinnFlyer is a great solution.

2) If you glue some wood inside the cowl, you will have enough meat to sand back, as RCKen suggests. Use epoxy instead of CA, in order to stand the fuel.

3) You could also add a metal washer as a spacer between the drive washer and the spinner back plate.

Regards!

Shhhh, you'll give my secret away.

Goirish,
I'm talking about the plate that is the very forward part of the cowl. Remove the spinner and sand that plate down on the right side. You can sand 1/16" away and the plate will still be plenty strong. This is the solution that is going to be the least amount of work here, IMHO

Ken

I love it when you talk like that. (least amount of work)

Personally, since it is still "in the bones" I'd bite the bullet and cut the ring off the front of the cowl and rebuild it with the proper spacing.
It will never be any easier than it is right now. (Not that it's "easy" to start with, I just prefer to do it right when I have the opportunity...)

OK!! I was able to sand enough off the ring to make it work without the spacer. Think I will now CA the ring to harded it up. It is pretty thin. about 1mm.

Rotfl!

[sm=bananahead.gif] Yeah, just whack it off at the firewall and start over. THAT will teach you to pay better attention to details.[:@][:'(] OK, OK so I'm kidding. There have been several good ideas above. I thought one really bad idea couldn't hurt too much.[sm=bananahead.gif]Forgot my hat.

Oh No! - Not the HAT!![sm=bananahead.gif]

Love the hat. Looks like the one I wear. Except mine in purple.