Prepping Engine Beds

[JohnV8r]

Hey Guys,

Bit of a change of plans on my engine beds. I made my best Bob Lico engine mount location template to see where my engine mounts were going to line up. I'm sure it is considerably underbuilt versus Bob's, but it did the trick. Thanks for the idea Bob!



That led me to realize my engine mounts are going to line up differently than I expected as the mounts will be inboard of the current outboard stringers. It would be considerably easier to do engine mounts similar to these that I believe are from "Snipe" as opposed to cutting down the outboard stringers and adding sisters.





I was a little surprised at the amount of epoxy & cabosil used on my engine beds. I filled up one and half 5 gallon buckets with just bedding compound. You can see here where I was using a chisel to to knock off what was generally 1/2 - 5/8" thick bedding compound.



Another surprise was that there was bilge paint under the bedding compound. Clearly, that was part of the reason it was so easy to chisel off. I still have to sand some remaining bedding compound and bilge paint off the stringers.

My question is what to do to prep the stringers for engine mounts like those above. I have bolt holes that need to be filled. I did put in two limber holes on the outboard stringers (which worked great when I rinsed everything off). My preference is to clean up the stringers and add some glass to them. Question is should I use 1708 with some wide margins inboard and outboard of the stingers to add additional strength/stiffness to the stringers... OR should I just be concerned about sanding, fileting/fairing the imperfections & sealing the stringers with lighter glass mat and epoxy?

Any feedback would be greatly appreciated.

Thanks,

JohnV8r

[Snipe]

John I just sanded the stringers down and beefed up the for and aft bulked when installed then went right to the stringers. If I were to do it again I might add some glass to the stringers and run a full length backing plate on the opposing side of the mount maybe even bolt it bulked to bulked. You could layer woven roving and 1708. Couldn’t hurt.
If you look at the factory set up it was just a piece of mahogany glued and bolted to the stringer then the engine was mounted to that. I have seen repowers with Cummins sitting right on top of that and are just fine for years. I went the direction i did because it worked the best for fitting everything in with all of the changes made. My mounts are very low on the stringers and I feel they will be ok. Every thing was made out of 6068 1/2” structural aluminum angle. They were floated in with west system thickened with Cabosil silica then through bolted with a backing plate. If you have any questions you can reach out if you want.

[JohnV8r]

Jason,

Thanks for that. I am going to add 48" x 19" pieces of 1708 to each stringer. The 19" dimension should give me pretty decent footing off the stringers for additional strength. Once I get that in, I'll reassess. I do like the idea of a full length backing plate on each stringer. I hadn't thought of that, but that would add considerable strength in a pretty straightforward manner.

I am going to glass the stringers to the bulkhead. However, I think the bulkhead may benefit more from that than the stringers.

Thanks for the feedback!

JohnV8r

[bob lico]

your welcome !!! i even used a 1x12 piece of wood at the end of the main beam of jig mitered to 10 degrees the same as down angle of ZF-220 IRM gears .and put a prop coupling on the wood to emulate the gears connected to the engine so the jig is the exact same as the real cummins engine and gears