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greghughespdx 01-27-2018 07:44 PM

Trying a baffle cutting idea
I'm currently working (when I can find some time away from my job, it's been crazy-busy) on the engine baffles for my 8A project. I actually have two baffle kits. One is the "old" style kit that was available circa 2000. The other is the newer style kit that is more refined and has modern drawings and plans pages.

While thinking about making that first set of baffle cuts, to allow the top cowling half to finally sit down and fit to the bottom half, I spoke with several more experienced builders about how to get that initial trimming done. There are a variety of methods, with common themes. While I was working on another side project (microcontroller-powered pilot controlled lighting system for the airport) I was playing with a small collapsible metal antenna, the type that used to be on every walkie-talkie when I was a kid, which got me to thinking.

I decided to take my "old style" baffle kit and sacrifice it, to see if I could make a tool of sorts that would provide a variable template, which could provide an accurate measurement of the inside of the cowling, then be overlayed on the baffle pieces from the "new" kit, to make the initial trimming measurements a little quicker and simpler. I headed on over to the aviation section at a local Harbor Freight and picked up a big batch of small inspection mirrors for a few bucks each. When you remove the little round mirror, you're left with a collapsible rod handle with a little ball on the end. The cashier was curious and had never seen someone buy 18 inspection mirrors at once, so you know how that conversation went. "Wait, did you say you're building an airplane?!?!"

I cut down the old baffle sides and back pieces, got some aluminum tape, strategically places some of the collapsible rods, and ended up with essentially what I had in my head. It's entirely possible someone has done this before, no idea. I just wanted to do something different and fun.

Anyhow -- Here's a rather long video (sorry, I ramble a bit too much when I think out loud) showing what I came up with so far:

(Click image for video)


I have not yet completed the actual cutting yet, so if anyone wants to warn me away from this please feel free! But I will report back here to let people know if I end up having to buy any replacement aluminum baffle parts or not. :D When I ran the idea by our friend Scott he advised me to be careful about the resulting measurements since the top cowling is curving over and is at a pretty extreme angle in these areas, so it's not a simple measurement. Good thing to be sure to pay attention to. I think if I am careful not to cut too much and if I measure carefully this might work. We shall see. My goal is to get it trimmed to where it basically just meets the top cowling, then switch to the paperclip method. Just trying to simplify that first set of bigger trimming cuts and maybe shave off some of the time spent getting to the finer trim stage.

*If* it actually works well, I was thinking maybe it could be a "tool" of sorts that could be shared and used by people when they get to that point. This one fits a parallel valve 360. Not shown here (since I have not finished them quite yet) are the rear baffle pieces.

Robin8er 01-27-2018 08:03 PM

If you search the paper clip method its basically the same idea. The problem, at least on my 8, is that you need to measure about every inch or so, not every few inches. the gap between points that you measure isnt linear in most places.

pilotkms 01-27-2018 09:10 PM

Paper clips
Yes. I think paper clips are the standard method. Simple & cheap. $1.29 or so.

Gisnar 01-28-2018 08:24 PM

Looks kind of like the EAA Hanger near by! Nice job on the build so far. Another thing to try is set up a tripod with a digital camera. Take two picture, one with the cowling on, on off.
Overlay the pictures and presto you can see the contour.

rzbill 01-29-2018 04:04 AM

A sharpie marker with a 1" dia rubber grommet on the writing end, taped to a stick, worked quite well for me.

fl-mike 01-29-2018 06:15 PM

Five paint mixing sticks, eight c-clamps, sharpie, duct tape. Done.
Don?t over-complicate it.

Kind of like trimming a countertop to fit against an irregular wall, only vertical.

greghughespdx 01-31-2018 02:02 PM

Gotcha. I am planning to use paperclips after the initial cut that this things in intended to help make.

And over-complicate things? Me??? Hah... Ask my ex-wife about that. :D

greghughespdx 01-31-2018 02:04 PM


Originally Posted by Robin8er (Post 1235398)
If you search the paper clip method its basically the same idea. The problem, at least on my 8, is that you need to measure about every inch or so, not every few inches. the gap between points that you measure isnt linear in most places.

Yeah I have been looking at that. Have not had time in the hangar this week to do much so no new work here. The idea is to get a cut that is very close to the cowl surface, then user paperclips or similar to make the final 3/8 - 1/2 inch cut.

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