Cowl Inlet Ramp Gap

UnPossible · #1 08-13-2011, 01:00 PM

Hey - quick question..... I'm fitting the fiberglass cowl inlet ramps to the top half of the cowling. What sort of gap should I shoot for between the edges of the ramp and the baffles? I'm assuming that I will want an 1/8" or so gap as the seals are going to be above the ramp... but want to check before I make the gap too large.

Thanks,
Jason

RV8R999 · #2 08-13-2011, 01:26 PM

Jason -

I'd spend some time really working this area as I believe the inlet seal is probably the spot where the least amount of attention is placed - at least in many I've seen and I admit my first go round I didn't do as good a job as I should have.

After some tweaking what really worked well was to trace the shape of the installed inlet onto the aluminum baffle sections along the sides of the ramps and then cut the alum about 1/4" lower than those lines. What this did for me was allow the baffle material to lay snug and flat along the lower surface of the inlet ramp creating a really effective seal. I've seen others allow the baffle material go up alongside the ramp and seal to the upper cowl but this leaves a path for flow to travel to the forward portion of the inlets and down into the lower cowl section. I saw good improvement in CHTs when I did this.

This is just one of many ways to make it work.

UnPossible · #3 08-13-2011, 01:32 PM

Ken - thanks for the response... I'll trim the baffles sides once I get the ramps finalized... based on your response, I am assuming that the goal is to get the gap on the outsides of the ramp to be pretty tight with the side baffles before you trim them... Is this correct? Additionally, what sort of gap did you leave between the ramps and the inside baffles (around the prop area)? - or did you trim the inner AL baffles 1/4" below the ramp sides as well?

Thanks again,
Jason

RV8R999 · #4 08-13-2011, 02:14 PM

Yes... but it is more about vertical clearance than horizontal as the baffle material will span the the gap. I used 1/4" vertical clearance to ensure the ramps dont contact the baffle sides due to vibration during engine starts. This seems to work for me.

I did the exact same thing on the inside inlet baffle near the prop. When you cut your rubber baffle material you'll only need 1 1/4" or 1 1/2" wide on both sides right up to the forward lip of the upper inlet (where the inlet ramp meets the upper inlet). This will form a nearly perfect seal.

I'll try to take some pictures if this isn't making sense the way I describe???

UnPossible · #5 08-13-2011, 02:35 PM

Ken - Pictures would be incredibly helpful.
Thanks,
Jason

Quote:

Originally Posted by RV8R999

Yes... but it is more about vertical clearance than horizontal as the baffle material will span the the gap. I used 1/4" vertical clearance to ensure the ramps dont contact the baffle sides due to vibration during engine starts. This seems to work for me.

I did the exact same thing on the inside inlet baffle near the prop. When you cut your rubber baffle material you'll only need 1 1/4" or 1 1/2" wide on both sides right up to the forward lip of the upper inlet (where the inlet ramp meets the upper inlet). This will form a nearly perfect seal.

I'll try to take some pictures if this isn't making sense the way I describe???