Tip: Large paper clips for baffles

As I read months ago on VAF forum, one uses paper clips on the edge of the baffles to check clearance between the baffles and the cowl. The only problem is that until one gets some clearance this trick doesn't work. I am installing baffles in a RV9A with an O 320 Lycoming and am using the standard baffle kit from Van's. I "guesstimated" that if I cut off 1/2" from the rear baffles using the original contour, I would get some clearance. This worked and then I put on the clips as seen in this photo. You know you are there when there is about 3/8 to 1/2" of paper clip sticking up above the baffle edge when you put on and take off the cowl.

After cutting and grinding some more, I got the required clearance. I then used the same method for the side baffles. I found that the original contour was fairly accurate but that it required cutting slightly more from the center of the back baffles and from the forward ends of the side baffles. The contour around the nose seems to be pretty good.
I am so glad that there is a fine source of information in the Van's Air Force Forum.
Thanks D.R.

Yes

You're getting there Cleve.
Be sure to have the upper fiberglass ramps glassed to the upper cowl and fit the side baffles accordingly.....patience/fit/cut/fit/cut. When you start attaching the rubber baffle material, cut it across the narrow width. That will provide an automatic inward curve since it was rolled and will keep that shape.

Regards,
Pierre

Initial baffle cut

There is a trick for getting the initial cut.
Install the uncut baffles.
Take four paint stirring sticks or similar. Raise the top cowling about 6 inches above the bottom cowling and clamp in place using the paint sticks to create four "legs". (Clamp sticks to the outside of the bottom using c-clamps or similar and likewise on the outside of the top piece.) The top cowl is now "floating" above the bottom cowl.
Wish I had taken pictures.
Now, adjust so the spacing is consistant all the way around. Six inches is a good amount (std steel rule). Make sure the top is directly above the bottom and not skewed fore/aft, left/right.
Now you have room to get your arm in there.
Tape a Sharpie exactly 6 inches down another paint stick or similar.
Now, reach in and hold the Sharpie stick up against the inside of the top cowling and run the marker along the baffles.
If you kept the stick vertical, you now have a pretty "exact" line representing the contour of the inside top cowl on the baffles.
Cut along the line (or if you're real gutsy, go ahead and move the line down the "gap" amount". You can also add the gap to the marking stick).
This will get you very close to the final fit.

Somebody must have pictures of this. Once you see it you think "of course!".

Very good!

Outstanding piece of advice, Mike. Were you ever a wooden boat builder? They use many similar helpful techniques.

Thanks,
Pierre

Timely Info

I'm always amazed that this info seems to pop up at just the right time. I hope to start baffles in the next week.

Dumb question.....

Why doesn't someone mold a crystal clear cowling that could be used in this process?

Granted, I have never done baffles, nor am I anywhere close to doing them. But it appears to me that the largest part of the process is guesswork as to where to trim, how much to trim, etc.

What if there were some clear cowlings strictly for this purpose, based on each RV model. It seems to me someone could make a nice little living by shipping these cowls around for a fee, and the people doing baffles could actually see where everything was lining up? I know cowlings are somewhat different, as far as actual final fit, how much you trimmed yours versus the next guy. But, if you had some sort of a visual gauge system on your first set of baffle material, you could install the 'somewhat universal' cowling, then look in there...."OK, reference point #1 needs about 1/2" cut off. Moving up to reference point # 2, we need about 1/4" cut off", etc.

Just a thought....from someone who has never been through this process.

txaviator said:

Why doesn't someone mold a crystal clear cowling that could be used in this process?
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Click to expand...

Gary, its not as bad as it might seem. To get started on the initial cut, Cleve simply installed the rear bulkdhead baffle first. Then we fitted the top cowl over this and it became clear that our first cut needed to be 1/2 inch. We could tell this because that is how high the cowl was being held up across the firewall at the rear by the baffle. We made this cut across the rear and then re fit the cowl and bingo, we had a tight fit with no gap across the rear. From there on, we used the paper clips to measure our clearnence after we made another cut. On the second cut we had our 3/8 clearence. We then progressed forward down the sides and used the cut line from the rear baffle to project forward keeping the same contour as the originals. We didnt have to resort to any gymnastics to find the correct cut line. If you wanted to take the trouble, you can make a cardboard template of the cowling profile by laying a piece of cardboard across the cowl on the outside. Hold the cardboard in place and slide a sharpie across the cowl marking the profile on the cardboard. You can then use this to transfer the exact cowl profile onto the baffle. Just make sure everything is held firmly and correctly in place. It aint as bad as it seems..

Nice!

Excellent tips, Claude. Thanks for sharing the exact process!

Take care,