Starduster 

Engine Baffling

Modification of Fiberglass Nose Bowl

The following pictures illustrates what I was going for with the nose bowl modifications.

Well, these were the plans until we decided to do the engine overhaul.  Jason had some other ideas on the nose bowl.  So we put garbage bags inside the engine cowling and filled the nose bowl with quick hardening foam.  The idea is to know where everything is located, shape the foam to the desired shape, and fiberglass over the top of it.

The Original Plans (for posterity)

I intended to bond fiberglass "L"s behind each inlet where the side of the "L" would mate just inside of (1) the aluminum side panels of the Baffle Box, and (2) the bottom of the "L" would come close to each cylinder, closing the gap with heat-proof tape.  The "L"s would also add a great deal of strength to the structure of the air intake and the cowling.  The pictures below at the L's after they were measured and shaped to miss the starter ring, generator belt, and engine.

I laid everything out on poster board and cut it to fit.  I'm beginning to wonder if I can remember where all the key marks are... This will be interesting to see how it close it comes after the first cut.

All measurements were taken from the leading edge of the nose bowl.  Propeller measurements were:

Pattern was cut for the hub diameter.  If the additional fiberglass on the front of nose bowl is too much further forward I will have to open the area for the propeller hub a little more.  The cowl fits between the Spinner and the Ring Gear.

An Alternative

A friend of my looked at my ideas and suggested closing the nose bowl completely.  He thought it would be better because (1) It would add strength to the nose bowl, and (2) It would reduce the drag even further.  By closing the sides we would change the "L's" into "U's" and add even more strength.

Things to do

1. I need to measure the distance from the centerline of the engine to the top of the sheet metal to make sure I have the clearance right.
2. Measure hole for oil cooler and overall size for mounting
3. Figure out best way to seal baffle top to top cowling

4. Determine if additional bracing is needed on nose bowl and where to place it if it is.

Basically, at this point I'm ready to begin.  I'll follow these steps:

1. Remove top and bottom cowling (send to Professional Fiberglass with templates)
2. Split the nose bowl and remove
3. Disconnect all the hoses, spark plug wires, etc.
4. Remove the old baffling
5. Disconnect oil cooler
6. Pull cylinders (see below)
7. Make templates from posterboard and size to fit
8. Transfer templates to aluminum sheet and cut
9. Mount side baffles, the rear baffle, and attach sides to rear
10. Mount top baffle and attach
11. Reinstall top and bottom cowling, check for fit.  Adjust if necessary
12. Remove top cowling and reinstall hoses, wires, etc.
13. Reinstall top and bottom cowling
14. Fit left and right halves of nose bowl, trim to fit
15. Attach heat tape to "L"s to close gaps between cylinders and side baffles
16. Mount oil cooler to right half of nose bowl
17. Reinstall nose bowl

Professional Fiberglass - Brighton, Michigan
401 Washington
(810) 227-6509  fax: (810) 227-9824

By chance I got in touch with Professional Fiberglass just to see about buying some fiberglass sheets.  Turns out they make parts for experimental airplanes and said they could do the fiberglass work.  I sent them the pictures above and they suggested using a fiberglass composite so its stronger and lighter.  So, I took some measurements, all my little cut-outs, and headed up to Brighton.

Fabrication of the Aluminum Baffle Box

The Baffle Box was constructed out of .032" 2024 T3 Aluminum.  I bought a 4x4 sheet and laid out the components something like the picture to the right.

I decided to use anchor nuts on the inside of the top cover so I would take it off and on without a lot of trouble.  Of course everything gets created in cardboard first to make sure everything is the right size.  This is what I had in mind in the beginning:

Materials

Aircraft Spruce

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