47 – Cowl Baffle Part 5 – Inlet Seals

IMG 7892

During the construction of the baffles, and test fitting the cowling, I realised there was an annoying snag brewing.

Ideally the baffle inlet air ramps should be slightly below the lower edge of the cowling inlet, so that the inlet seals will lie flat.

Of course the engine is likely to sag 1/8″ to 3/16″ inches, so during construction it may be best to accept this error.

But I reckoned my cowling inlet position was about 1/8″ too low, even allowing for some engine sag.

So I made the decision to face the extra work, and raise the cowling inlet lower edges by 1/8″. The picture shows parcel tape added to the right baffle air ramp to act as a release agent for epoxy/flox.

IMG 7893

It’s hard to see in this picture, but I made a jig to sit at the correct height above each baffle air ramp, so that the top of the added epoxy/flox would be moulded in the correct vertical position.

I added enough epoxy/flox to shape the inlet, and kept in place with peel ply during the cure.

IMG 7899

Once set I used the Dremel sanding drum to grind off the lower edges …

IMG 7898

… resulting in a raised lip.

IMG 7905

This shows a test fit of the cowling to check the underside of the lower inlet lip was now at the correct height.

I went for a compromise, allowing for some future engine sag.

IMG 7908

As per manual 47-25 I measured the misalignment between the bottom cowl air inlets and the CB-00033 Air Filter Frame Cover, CB-00007 Right Air Ramp, and CB-00034 Right Air Ramp Cone.

IMG 7915

Since I had ground off the lower edges of the cowling inlets, I added two layers of glass cloth to restore strength.

IMG 7918

It took quite a while to hand form the CB-00036-L & -R Clamping Strips, and then clamp them in a position to replicate the measured misalignment.

I again used parcel tape on the strips to act as a release agent, which I’ve found to work very well.

The picture shows the epoxy/flox added to the gaps and curing.

IMG 7971

Once set the rear edges and corners of the inlets are aerodynamically shaped, involving yet more dust!

I used the Dremel for rough shaping, and then shaped sanding blocks.

IMG 7927

Then the top cowl inlets have to be matched to the bottom cowl inlets.

Having measured etc I ended up using cardboard to mould the epoxy/flox into the approximate shape.

IMG 7976

And then after test fitting and marking, more dust!

IMG 7975

I used my long sanding block to fine tune the level of the top cowling outer edges … the cardboard made sure I wasn’t changing the carefully finished central area.

IMG 7977

I finished the final top/bottom matching with the cowlings connected.

IMG 7991

The rubber seals are now aligned with the CB-00036-L & -R Clamping Strips ready for match drilling.

I found it best to tape the seals into position on the strips prior to clamping.

IMG 7989

Once happy with the location I used clamps and a wooden block ready for match drilling.

IMG 7990

Match drilling parallel to the cowling inlet lip lower surface.

IMG 7998

The final result.

Loads of extra work raising the inlet lips, but I suspect it has saved future frustration with both the fitting of the cowling and the look.

I’m not sure why the cowling ended up a smidge too low, since I built as per the manual. The MT Propeller spinner is a very close match to the Vans stock one, but I guess the engine sag allowance is critical. Perhaps I slightly overdid it, although it looks and measures about right?

A few other builders have mentioned the same issue.

We’ll see : )

IMG 7997

Be the first to comment on "47 – Cowl Baffle Part 5 – Inlet Seals"

Leave a comment

Your email address will not be published.