Filling in upper cowl near air ramps

I am installing my air ramps in my upper cowl and I was wondering if there is a need or benefit to extending some epoxy into the outboard area on either side of the air inlets? Would this help prevent air from flowing behind the ramp?

Yeah. Stuff something in behind for a backing. Temp or permanent your choice. Then a couple little chunks of glass cloth and resin. Then I'd smooth in that and the nose sides with a few fingerfulls of micro/epoxy. Your baffle seal will terminate in there somewhere somehow.

Might be a good idea to wait on that until the cowl halves are joined with all the hinges or fasteners in place to see what access you have or might need.

Dave

Here is what mine looks like.
Make sure the cut out for the governor actuator arm is large enough.
I had to do some more digging out after I was doner with this.
I filled the cavity with poly foam and fiberglassed over it.
The baffling fits very nicely around the ramps this way.
Ther is no need for that Ziggi Zaggy cut out just make a nice round curve
to accommodate the governor and the full travel of the actuator arm.
The air will be blocked by the baffling around the base of the governor.

I'm futzing with that area right now too, and am doing much as suggested above. Sealed the small gap at the outer end of the ramps with glass and smoothed with micro. Am building a vertical bulkhead in the gap cut for the governor, which will give the baffle material something to seal against. It looks to me like the area around the governor deserves special attention to detail, as it could leak a lot of air. I think I may like the solution shown by Ernst above even better, nice work.

While you are working on the finishing, you should also add a joggle/step at and around the front two corners on the lower cowling. This will also stop air and also add support.

When I was Crew Chief for a Reno Air Race Super Sport air racer, we built a completely new air inlet for the Questair Venture. The inlets were smaller than those on my RV-6A but we had CHTs below 350 at well over 400 MPH . That was at over 70" boost.

One of the reasons for the great cooling was the inlet ramps and the large radius at the inlets. The inlet ramps should have a slope of not more than 7/1. For the -10 it would mean extending the ramps much further into the cowl. Mine will be.

CharlieWaffles said:

I am installing my air ramps in my upper cowl and I was wondering if there is a need or benefit to extending some epoxy into the outboard area on either side of the air inlets? Would this help prevent air from flowing behind the ramp?

Click to expand...

Your real goal is providing surfaces against which the rubber baffle seals can truly seal. That may or may not include closing off the ends of the ramp.

agree with Dan. Closing off those ramps is totally unnecessary if you fashion your rubber baffle material to rest flat against those ramps rather than against the upper cowl. If you do this, the upper plenum pressure helps ensure a very tight inlet. If you choose to close them off and allow the rubber baffle to lay up against that section and not flat against the ramp itself you will allow spillage from top-half to bottom-half as the baffle material goes from horizontal to vertical where the two halves meet at the forward inboard/outboard sides of the inlet. Even if the rubber baffle seals tightly against the cowl in this area it forms a vertical tube allowing air to spill to the lower cowl.