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Trimming Engine Baffles

pilot28906

Well Known Member
I am starting to make the first cuts on the engine baffles and am wonder how you guys have cut the baffles? Did you mark them then cut them while they were installed on the engine or did you take them all off every time you trimmed a little then put them back on for another mark? If you left them on the engine what did you use to make the cut; cut off wheel?

Thanks for the info.
 
You do an iterative process of trimming until you trim just enough to fit the top cowl and not hit the baffle. At that point you can reach in with a sharpie, holding the Sharpie barrel to the top cowl and mark the inside of the baffles. the Sharpie is just about the perfect thickness for this.

I standard tin snip is just fine for making the cuts. No real need to remove the baffles to make the cuts.

Go slow on the initial cuts - many small cuts to just get the top cowl on.

Carl
 
I generally cut mine in-place using aviation tin snips. There were a couple of spots where I had to go to a different tool, but in general these worked well.

The bigger tip is to use the paper clip method to determine how much to cut off. I still made a significant number of attempts to get them cut to the right height, but having the paper clips to judge spacing helped a lot.

Also, I was surprised at home much I had to cut off on my RV-10.
 
I still think the paint stick offset method is the fastest and most accurate method. Much faster than the paper clip method.
I think I made the cuts off the engine, but it?s been a while.
 
Thanks, tin snips works fine. I have made several cuts and still sneaking up on it. I will read up on the paper clip method.

Thanks again.
 
Thanks, tin snips works fine. I have made several cuts and still sneaking up on it. I will read up on the paper clip method.

Thanks again.
Simply, you get a squadron of paperclips and lay them next to each other on the installed baffles, then (try) to install the cowling, pushing down the paperclips.

Like this:
9604383550_b2bb2dd648_c.jpg



If any paperclips are pushed all the way down to the baffle, then that's an area that you need to trim a little more off. You're looking for around 0.5-1.0 inches of paperclip left before it's pushed all the way down, with the cowling installed to your satisfaction. In the bottom image, you can see I need to trim a touch more from the left side, the middle is OK-ish, and to make a nice rounded edge, I need to remove a bit more from the right side too.

Kinda-sorta like this:
9604372746_d76668bb51_c.jpg
 
Thanks for the photos. I need to take more off before I can use the paper clips. I am assuming the top cowling has to be fully on the lower cowling before the clips can be used?
 
Once I had the height within about 3/16” or more of the final height using snips and my nibbler, I used masking tape to mark the final desired profile. Then removed the baffles to use the belt sander, air tools and a file to take the extra material up to the tape edge. The snips leave a deflected edge and looks kind of crappy.
 
Last edited:
I am familiar with the paper clip method but what is the paint stick offset?
Wish I had taken pictures, but:
  1. Take four paint stirring sticks.
  2. Clamp them on the outside of the sides of the lower cowl near the four corners so that six inches or so of the stick is above the lower cowl edge. Location is not critical, just in a straighter area so you can clamp easier.
  3. Clamp the top cowl on the sticks leaving four inches or so gap between the upper and lower cowl (sticks are on the outside of the cowl halves). Make sure the firewall edge of the cowls are lined up, i.e. top cowl is not forward or aft of the bottom cowl.
  4. Adjust the clamps until the gap is exactly the same on all four sticks. The top cowl is now parallel to and "floating" above the lower cowl. (consider the thickness of your forearm in selecting the gap dimension!)
  5. Take another (thinner) stick and tape a sharpie to it with the marking tip sticking out about 1/8" or so from the stick (stick and sharpie form an "L"). A dowel works fine.
  6. Trim the stick so the distance from the top of the stick to the sharpie tip is the same as the gap between the cowls, plus your desired cowl to baffles clearance distance (1/2" or so) <<< important step!
  7. Reach in through the gap between the two cowls (created in step 3) and run the marking stick along the baffles while touching the inner surface of the top cowl (while keeping the marking stick vertical)
  8. Draw all around the outside of the baffles
You have just drawn the exact trim line for your baffles.

Super fast, and dead on. No need to "creep up" on the final cut line.
I will admit, I cut above the line for the first cut, just to be sure, but that turned our to be unnecessary.
The only area to watch is up by the intakes since the slope changes faster and you have the upper ramps to work around.

Note, this is the vertical method of trimming a countertop to fit an irregular wall, and all walls are irregular!

Hope you can visualize what I'm talking about. Once you see it, it's obvious.
 
I just did this last week, as Mike mentioned above (paint stick method). Worked perfect and much quicker than paperclips.
 
Paint Stick method

Wish I had taken pictures, but:
  1. Take four paint stirring sticks.
  2. Clamp them on the outside of the sides of the lower cowl near the four corners so that six inches or so of the stick is above the lower cowl edge. Location is not critical, just in a straighter area so you can clamp easier.
  3. Clamp the top cowl on the sticks leaving four inches or so gap between the upper and lower cowl (sticks are on the outside of the cowl halves). Make sure the firewall edge of the cowls are lined up, i.e. top cowl is not forward or aft of the bottom cowl.
  4. Adjust the clamps until the gap is exactly the same on all four sticks. The top cowl is now parallel to and "floating" above the lower cowl. (consider the thickness of your forearm in selecting the gap dimension!)
  5. Take another (thinner) stick and tape a sharpie to it with the marking tip sticking out about 1/8" or so from the stick (stick and sharpie form an "L"). A dowel works fine.
  6. Trim the stick so the distance from the top of the stick to the sharpie tip is the same as the gap between the cowls, plus your desired cowl to baffles clearance distance (1/2" or so) <<< important step!
  7. Reach in through the gap between the two cowls (created in step 3) and run the marking stick along the baffles while touching the inner surface of the top cowl (while keeping the marking stick vertical)
  8. Draw all around the outside of the baffles
You have just drawn the exact trim line for your baffles. ...
That's clever - probably would have saved me about 100 sessions of on/off of the top cowl. At least I got a lot of practice putting on the top cowl! :)
 
Mike in Venice

Thanks, that worked great, I did not add the 1/2 inch but I will reset the upper cowl and check, then trim once more, thanks again.

Matt
 
Mike in Venice- that is brilliant! Thank you for the write up, I am getting close to baffle trimming and this will save a ton of time.
 
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