Baffling doublers

[sport65]

Do the new jabiru 3300 engines need the baffle doublers? I noticed On kips ( in the jabiru 3300 tips and tricks and gotchas) it has a cutout below the doublers for the oil line, the new Engines do not have this cutout, and I was wondering if this is What caused the cracking?

[sport65]

Is this a dumb question?

[sonex892]

Not having the external oil tube cut outs should help prevent the plenums cracking on new engines. The oil cut out is where both of my plenums began to crack. I put doublers on after stop drilling the cracks. It held up fine for a couple of years then another crack started on the left front oil tube cut out. This crack travelled around and under the doubler effectively totally cutting the plenum.

I've now given up on the metal ducts and have gone back to the jabiru supplied fibreglass style plenums. I reworked the size to the same volume as the metal ducts. Problem solved

Steve
892

[tonyr]

Hi Jeff,
I have a late 2200 with metal baffles.
75 hours in service so far, and no cracks have appeared between the cylinders.

Cheers
Tony

[sport65]

Thanks guys! I'll try it without the doublers then and see what happens!
It's scary to think you said something so dumb that nobody would
Reply!

[LarryEWaiex121]

Jeff,

The cutouts really have nothing to do with the cracking. The cracking comes about as a result of the expansion and contraction of the shroud to a fix object. The engine. The tins grow and then shrink much more than the more robust structure of the engine.
Most of the vertical cracks will start from the valve cover holes around the 250-300 mark from most folks I've talked to.
Mine started about 250 hrs on my Waiex/Jab3300. I simply added doubler stripes and both riveted and JB welded the doublers in place. The cracks remain from the cover holes to the bottom of the doublers but then stop there.
In a perfect world the tins would be rubber isolated from the engine and allowed to expand and contract. This is not in keeping with the KISS principle and my guess, the reason it is, like it is?