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Lower Cowling Intake Bottom Lip to Air Ramp Clearance

M

Meat

Active Member
Patron
Hi All,

Per page 47-25 I'm installing the CB-00032N and -32O Cowl Baffle Seals on the interior lower intake lips of my bottom cowling. How much space should exist between the bottom cowling aft intake edges and the left side air intake ramp and right side air ramp? The plans don't specify. Only to trim the cowling to the scribe lines. My concern is getting the cowling on and off. Particularly back on where those seals must be positioned on top of the air ramps. It seems you'd need a decent gap to manipulate the rubber seals to get them on top of the ramps when installing the cowling. Like maybe 5/16" to 1/2".

What size gap are you guys using and are you happy with it? How tough is it to position those seals on top of the air ramps when installing the lower cowling?

Thanks for any vectors.

Cheers,
Scott Davis
RV-14 #140702
 
Meat said:
Hi All,

Per page 47-25 I'm installing the CB-00032N and -32O Cowl Baffle Seals on the interior lower intake lips of my bottom cowling. How much space should exist between the bottom cowling aft intake edges and the left side air intake ramp and right side air ramp? The plans don't specify. Only to trim the cowling to the scribe lines. My concern is getting the cowling on and off. Particularly back on where those seals must be positioned on top of the air ramps. It seems you'd need a decent gap to manipulate the rubber seals to get them on top of the ramps when installing the cowling. Like maybe 5/16" to 1/2".

What size gap are you guys using and are you happy with it? How tough is it to position those seals on top of the air ramps when installing the lower cowling?

Thanks for any vectors.

Cheers,
Scott Davis
RV-14 #140702
Click to expand...
I can maybe answer half of the questions. The older baffle kit plans that I have specify a gap of 3/8" between the fiberglass cowl and the inlet ramps. The newer plans in OP-44 don't mention it and the drawing cross section appears to show no gap.
The engine shakes on startup, so that may be another reason to leave a gap, same as why there is a gap between the rest of the baffling and the cowl inner surface.
 
I target about 1/2” space between cowling & baffle inlet. This gives enough room to fold the (Vans rubber) seal material up & over while installing the lower cowling.
You might want a bit more gap if you are using silicone sealing material.
 
Here is another relevant post that confirms a gap of 3/8" to 1/2"

RV-7A JCarne

Another good day today. I'm beat after today, a lot of up and down movement. However, it was awesome to be installing systems on the engine. After installing the Avstar fuel servo I focused on the mixture control cable. This little Rube Goldberg contraption I think is just so cool! It...
vansairforce.net vansairforce.net
 
Meat said:
Hi All,

Per page 47-25 I'm installing the CB-00032N and -32O Cowl Baffle Seals on the interior lower intake lips of my bottom cowling. How much space should exist between the bottom cowling aft intake edges and the left side air intake ramp and right side air ramp? The plans don't specify. Only to trim the cowling to the scribe lines. My concern is getting the cowling on and off. Particularly back on where those seals must be positioned on top of the air ramps. It seems you'd need a decent gap to manipulate the rubber seals to get them on top of the ramps when installing the cowling. Like maybe 5/16" to 1/2".

What size gap are you guys using and are you happy with it? How tough is it to position those seals on top of the air ramps when installing the lower cowling?

Thanks for any vectors.

Cheers,
Scott Davis
RV-14 #140702
Click to expand...

Scott,

Your question is certainly valid. I think if you'll do a search, you'll find multiple instances on different models that have had some trouble with this question and solution. As for me on my RV-14, I am no exception. I think you'll find that if you have much of a gap/space between the air filter frame and the cowl on the RV-14 that your intake will look "funny". There's not a ton of room on the cowl after you remove what is required on the intake (pilot) side.

I worked on this for quite some time and finally decided that I needed to be able to install the seals after the bottom cowl was in place. Tough? Absolutely. However, regardless of gap, I just didn't see an easy way to install the lower cowl having to fight getting the seals over forward portion of the baffles. The cowl is tough enough to get into place without damaging paint as it is. For me, I thought adding inlet seals before installing it would aggravate the problem.

What I ended up realizing is that the elevation or alignment of the intake to the baffle is more important than the "gap". In other words, the intake lip of the cowl needs to be high enough relative to the baffle to allow the seal to slide in from the back of the inlet (baffle side). This gives the engine room to move and gives you room to install the baffle seals after cowl is installed.

I'm sure there's a number of good ways to do this, I just couldn't find one that I was happy with so I install the seals after the bottom cowl is in place.

Below are a few threads that talk about the problem:
 
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