Locating Inlet in 'Space'

[TX7A]

I started working on my baffles a few days ago and worked my way up to the front baffles. As Van's baffle instructions indicate, it usually takes a few iterations of trimming the forward end of the ramp and side baffles and then attaching and removing the lower cowl to check for fit each time.
The problem is that you need the lower cowl and the forward and side baffles on at the same time...before you start trimming...to see how much to trim.
Sometimes I have a hard time visualizing things and how the finished product is suppose to be.
What I needed was a way to locate the rear edge of the cowl inlet without the cowl being on the plane. Here's what I did:
(Note: to use this method, the cowl fitment to the fuselage needs to be completed.)

Attached the cowl to the plane. Using one of the 1/4" holes in the flywheel, attach a scrap piece of aluminum (I used some .025) that is slightly bigger than the cowl inlet. I'll call this the 'locator'. I used a 5/16 wood shim to get clearance for the aluminum. (see pic) Bend it so that it is parallel and flush against the aft edge of the cowl inlet. This is the edge that you are ultimately trying to fit the baffle to.

From the inlet opening, trace a line on the aluminum around the edge of the rear of the inlet. (disregard my scribbles)


I made a little index pointer that conveniently attached to the forward baffle bracket. The pointer lines up with a random tooth on the flywheel and acts as a way to keep the the locator in the right place in case you accidently move the prop. (be sure to mark the tooth on the flywheel)


Remove the aluminum locator and trim to the line that you traced. Attach it back on to the flywheel. Double check the accuracy of the aluminum locator and the pointer. Remove the cowl.

Now you have a fixture that locates the cowl inlet without the cowl being on. Attach the forward and side baffles. You'll be able see how much the ramp needs to be trimmed and re-bent, how much the sides need to be trimmed and bent inboard and you'll easily see where the "tangent" point is for the diagonal bend.

I got 'chicken' and left my cuts about a 1/4" long. I could have cut the baffles to the locator and they would have been just about perfect.
Here's the finished ramp cut. (I'm pressing it down slightly so you can see how the locator line matched to the cowl inlet.)

Took me about 30 minutes to set it up.
...just another way to skin a cat.

[Lars]

Nice approach, Sam. I cut mine a few weeks ago. My approach was far cruder. With the lower cowl on I sorta shoved the ramps under the cowl opening, marked the approximate location of the trim line with a Sharpie, then trimmed well forward of that. Then iterated on that until I got it right, which required several rounds of lower cowl r&r. Eventually I wound up with a very satisfactory result, but it took a long time. Your method is far more elegant.