Securing SCAT Tube to Oil Cooler on RV-14 w/EXP119?

[Meat]

Hi All,

I'm building a taildragger RV-14 with the EXP119 engine. For some odd reason Van's used an irregular octagon shape on the oil cooler flange to secure the 5" SCAT tube instead of a circular flange as they did on the intake side of the oil cooler duct. The problem is securing the SCAT tube to this oddly shaped flange with a conventional hose clamp. Vans directs the clamp be bent into shape by hand to match this semi rectangular shape. Being that the clamp constantly decreases in circumference as you tighten it down its difficult to make the clamp match the octogon shape of the flange. This results in sizable gaps along the straight edges of the flange between the SCAT tube and flange where the hose clamp doesn't cinch down flush and tight and resultant air leaks. There's got to be a better way to do this.

Has anyone else run into this issue and how did you deal with it? I've been looking at the Clamptite tool that utilizes safety wire to make hose clamps as one possible solution. Thanks for your time and advice.

Cheers,
Scott Davis

 

[georgemohr]

I pre-bent this hose clamp by hand working my way clockwise around the octagon without the scat tube in place. The fit is pretty good. not perfect to be sure. I also wish this exit was circular. I've seen some folks make a mould or a 3-printed part here.

 

[PhatRV]

My friend Steve is a tool maker and he makes a fiberglass oil cooler plenum for another angle valve engine. I can give you his phone number so you can chat if you IM me.

 

[stigaro]

In theory, can you measure the outer perimeter of the flange (P), adjust the clamp to that same circumference (P/3.14), then shape the flange to fit the octagon? You would have to loosen the clamp a few turns to get the scat tube in place, but not much and the final shape shape be the right size.

 

[bjdecker]

...Or just make your own plenum-diffuser...

 

[jeffreyuh60]

It will fit well. I put mine on and hand flattened the clamp. NBD, really.

 

[bwagner]

Per the plans; pre-bending the hose clamp then carefully cinching it down around that 5" SCAT tube about the oil cooler plenum flange, worked out just fine - it has remained secure as of 75hrs hobbs. Oil temps on my IO-390 EXP-119 Thunderbolt are running just under 200degF

 

[Reflex]

Scott,

It's my opinion that the way Vans has designed this is just plain bad. I ran into the same problem to which you're referring just about a year ago. After several nights of frustration and knowing what Vans has designed has significant potential problems, I decided to make a fiberglass transition from round to rectangular.

After posting pretty much the same question as yours above, I found that several builders agree that there are better ways to do this.

The thread can be found here

Round to Rectangular Transition

There are a number of solutions on the link. Note: I don't have an EXP-119, but the problem is the same.

Good luck,

Fred

 

[Bavafa]

I have made a couple of those transition from rectangular to round and that is what I have currently on my plane. In practical term, this has not done any improvement in temps, at least not anything that would clearly register as an improvement but it has made it for a better look and uniqueness. In fact I have one that may just work for you and could send it to you for price of shipping charges.