Dig it

Ok, I have a old byron SU-26. Its an awesome plane and until recently I've been flying it with a OS91FX. I had original intentions for that engine and now I"m at the point where I'd like to use it on another project. To replace it I have a OS 1.20 4-stroke but dammmmmm, that things big. It's 106mm from the firewall to the outer edge of the cowl and my 91 right up against the firewall was 110mm (thats to the back of the prop). A good fit. The 1.20 however is 145mm, so ya, its wayyyy outside the cowl edge. Does anybody have any brilliant ideas on how I could make this 1.20 fit without hacking the bejesus out of the plane?

Tired Old Man

My Feedback: (1)

Think about this one before you decide that I must be crazy.

Stare at the firewall for a while to see if the is a way you can fit a new firewall behind the stock one after a little cutting. Using the right sized spacers for engine clearance, you should be able to install a new firewall behind the original one and still maintain enough of the original all the way around to properly brace and support the recessed one.

It's going to be some work, tho[:-]

Campy

My Feedback: (1)

Another option you can think about is another cowl that is longer than the stock one. Fiberglass Specialties http://www.fiberglassspecialtiesinc.com/ and Stans Fiber Tech http://www.stansfibertech.com/ have a multitude of cowls.

That would be easier than cutting and relocating the firewall, and I sincerely doubt most people from 5' away would notice the difference.

bigchap

i guess your problem is the carb hitting the fire wall,if so you are stuck unless you fancy major surgery,you may be able to get a short,straight inlet manifold made and use that in conjunction with a proprietary carb.

Dig it

I like the idea of a longer cowl. I posted the same topic on RCCanada and got the same answer. Ya know, the internet is a wonderful thing full of people with more experiance and common sense than me

Broken

I have done as silversurfer sugessted on one of my models and it works fine- I don't favor pushing the bigger motor further forward unless i had a need CG wise..