Baffle trimming and intake ramp finishing

In order to get the top cowling back on, the baffle needed to be trimmed. I saw two ways to do this, and I ended up sort of using both. I started by elevating the top cowl 6″ above the lower cowl. Care was taken to make sure it was aligned both fore, aft, left, and right to the bottom cowl. I just used some pieces of scrap wood and clamps that I had lying around on each corner on the outside of the cowl. I measured in multiple locations along the horizontal split to be sure I was satisfied before moving on.

Cowl elevated 6″
More of a front view.

I then made a tool out of a tongue depressor and an aluminum block I had. I taped a sharpie to the bottom of the block and adjusted the stick to get exactly 6″ from pen to top of the stick. I didn’t take any pictures, but the idea here is that you have enough room (with the 6″ elevation) to get your hands/arms inside to hold the stick at a 90 degree angle with the sharpie along the inside of the baffle. Holding the stick on the inside of the upper cowl, you move it aft tracing the contour of the top cowl onto the baffle which will serve as a trim line.

I then trimmed to that line. That basically got me to flush. One could certainly add some extra to the length of the stick to get the the gap you’d like to achieve. Instead, once the initial trim was done, I utilized the 2nd method of paper clips all along the baffles. You barely stick them on and then place the top cowl into position. They slide downward and give you an exact indication of how much gap you have at that location to the top cowl.

Paperclips in position to measure gap

Below you can see the results of the first attempt. You’re shooting for somewhere between 12/32″ and 16/32″ gap per the plans. At each paperclip location, I wrote the number of 32’nds needed to get to 12/32″ by measuring how high each paperclip was above the edge of the baffle.

Measuring current gap

Those measurements basically were used to draw a new trim line.

Marking a more precise trim line.

I ended up doing this for a couple of cycles until I was completely satisfied with the gap all the way around. Making smaller adjustments in specific areas as I went. Below isn’t the best picture, but it was the results of the baffle trimming with a gap to the top cowl.

I fabricated the clips and drilled them into position per the plans. I’m holding off riveting most of this stuff until later.

Now that the baffles were trimmed, I decided it was time to affix the top cowl inlet ramps. I placed them into position with clecos and some scrap metal strip to hold them in place at the front.

I then test fit the cowl and had to trim the outer side baffles more to account for the curvature. I did get somewhat lucky due to my cowl being so far forward based on my prop/spinner setup compared to most. The ramps didn’t require trimming at the prop governor to at least test fit. I did end up trimming around to give some more clearance, which I’ll foam in later to provide a good backing for baffle material.

No initial trimming required for prop governor.

Once I was happy with their location, I epoxied them into place. Later I will layup some cloth, but for now just epoxy to hold them in position. I also did a single layer of cloth and some peel ply on the inlet circle just to hold that area into position.

Epoxy ramps into place.
1 temp layer of tape with peel ply on the outside.

I then laid up 3-4 layers of cloth for the underside of the circular inlet.. Placed that into position and let it cure. I sanded down the outside area and added micro. Once that was cured, I sanded to a smooth finish.

Right inlet ramp micro’ed
Same on left side.
Cutout for prop governor

With the upper ramps completed enough for now, I moved on to customizing the center baffles. I started with the right side, seeing it’s the easier side without compressor interference to deal with. I cut the stock baffle leaving just enough flange to rivet a new piece that would angle toward the inboard side of the inlet. I first made a template from construction paper and got it as close as I could. I transferred to metal and worked on trimming to get a good gap to the upper inlet ramps.

Paper template of right side.
Transfer template to metal and test fit.

I then spent some iterations trimming this custom piece to match the curvature of the upper inlet ramp with some gap for baffle material. Below are the results.

Right center baffle gap.

To hold the inboard side in place I fabricated up some 3/4″ x 0.125″ Angle. Seeing there was a slight bend in the baffle I just created near the inlet, I marked a cut to match that bend in the angle. I marked and cut out a “V”

Marking the cut to bend the angle
Cut made.
Bending the angle to match the bend in the baffle.

Below is the end result after match drilling and cleco’ing the baffle to the angle.

I utilized 3 screws to tie the aft piece of metal holding the carbon fiber ramp to the front pieces, including the piece of metal that runs under the carbon fiber ramp. I trimmed the excess away on the inboard side of any carbon fiber and metal plate so it didn’t protrude past the angle.

I then did a similar thing using a template on the left side. I decided to use one piece of metal to wrap around the governor and bend around the AC compressor belt to box it out of the inlet area.

Beginnings of a paper template

Once I was satisfied with the paper template, I transferred it onto metal, cut it out, and made the needed bends as shown below.

Initial trim of the custom left baffle.
A front view.

I then worked to fabricate another short piece of angle with a notch cut out for AC belt clearance to hold the inboard side in place. I drilled 2 holes for #6 screws to attach to the stock baffle that I had cut off and left a bit of a flange for connecting my custom piece to.

View of left ramp area with baffles screwed together and cleco’ed to the angle
Front view showing the angle and 2 #8 screws holding it in position, allowing clearance for the AC belt.
View of the finished up left ramp area.
Both ramp areas complete (beside riveting everything).
Final picture with top cowling in place.

This was a lot of work!

One thought on “Baffle trimming and intake ramp finishing

  1. melsuarez11 February 2, 2022 / 12:48 pm

    Hey Adam good work man I enjoyed reading this. I would love to be there when you fire it up and and would love to be of help otherwise

    Like

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