Need ideas on how to make an OS 25 fit in a fox 35 slot.

Can somebody tell me their method on reducing the opening gap, (where the engine mounts), on a profile fuselage. My Brodak Buster calls for a 19 to 40 size engine. A Fox 35 would fit perfect but I wanted to put an OS 25 on it. The gap is too wide to properly mount the OS. I have noticed several kits are like this. It seems it would make more sense to make the cut out smaller and one could trim away as needed. Instead of making the cut out large to begin with.

Aluminum mounts.. A search should bring up several threads.

I use popcicle sticks to shim the bearers. use epoxy to glue them to the motor mounts and trim after glue is dry.

>I use popcicle sticks to shim the bearers. use epoxy to glue
>them to the motor mounts and trim after glue is dry.
>
>Tom
The bearers? Im sorry, not fimiliar with that term. Are you epoxying the popsicle sticks to the hardwood motor mount? (Fairly new at building, thanks for your patience"

That is exactly what he means. Just be sure to add the same amount to both sides to keep the engine on the same center line. If you don't want to use popsicle sticks just use balsa that is the same thickness as your profile body less the doublers. Works very well either way.

Bill

LAST EDITED ON Aug-13-04 AT 10:28 PM (CDT)
 
All the .25 and .28 engines I've owned (BB ones, not plain bearing, though I don't think it makes a difference) have hole spacings very similar to a .35 stunt, just a hair wider. What I did when I needed to fit a .35 Stunt to a plane I had drilled for a .25 was to file the outsides of the holes of the .35 (this was for Combat, don't look so shocked.. ). I suppose you could file the outsides of the insides of the holes for the .25. I didn't notice that the case widths were different, but maybe they were, if so, I'd have trimmed the mounts at the corner right under the motor (going from a .28 to the .35).

I'm building a Walter Umland Shark 15 kit to replace my late lamented scratch built Shark 15. The bearers are spaced for 15-size engines and thus too wide for my TD 09. Not a problem because I made replacable aluminum pad mounts anyway so I could try a couple of other engines with different width cases and bolt hole spacing.

I think you will find that a strip of 1/20" hard balsa glued to the outside of each hardwood engine bearer/mount will narrow the spacing from a Fox 35 spacing to suit the OS 25.

Of course, you need to narrow the balsa spacers that fit between the bearers by the same amount.

pelham,
Unless I'm wrong, there are several methods being discussed here that may be a bit confusing to you. Here are a few more opinions.
The popsicle sticks may be epoxied on AFTER you have built the plane, or before you build it.
The balsa shims are installed BEFORE the engine bearers (mounts) have been installed so the mounts will be spaced closer together.
The aluminum mounts can be installed at any time.
As Isky mentioned, you might want to check if you can just "hog" out the holes first if it's already built.
When building kits, some mention what engine it is spaced for and that you may have to add or remove material to adjust width for your engine.
One thing to be careful of is cutting away existing mounts for larger engines. It is often done, but make sure there is enough mount left to safely support the engine you are installing.
If you have not built the kit yet, you may also want to replace the bearers with wider ones.
Good luck with it, whatever method you use.

LAST EDITED ON Aug-16-04 AT 05:40 PM (CDT)
 

> If you have not built the kit yet, you may also want to
>replace the bearers with wider ones.

I like the wider bearers idea. My local hobby shop only carries 1/2 by 1/2 mounts. Any ideas where I can purchase wider hardwood mounts?

I used 2 pieces of aluminum 1/4" thick 1/2" wide. I bolted the aluminum strips to the hard wood maple. I drilled and taped holes in the aluminum to match the OS 25 engine.