How To Make a Patch for the Nose Bowl


The nose bowl is a victim of vibration. Sooner or later it develops cracks. This is normal and can not be avoided completely. As precaution, make sure that the bowl is screwed on tight to the nose ring. You can use high temperature tape to support certain areas from the inside. Also make sure no baffling parts rub against the cowl, as it is easily rubbed through. Then you have a hole or crack that needs either to be stop drilled and/or patched.

Here is how I made one.

I was not smart enough to take a picture of the crack without the patch, so here is one of another nose bowl with a crack in the same area.

The area between the fuel pump and the propeller hole is weakened by an extra cutout for the fuel pump that is not needed in many cases. The material is lacking a pronounced profile here and will start vibrating. The repeated movement of the aluminum hardens it and then it cracks.

You can apply a sheet metal patch at the inside as shown in this picture above.

But it will need some retouching and painting to be smooth again, or you can patch it from the outside, proudly showing that your Ercoupe already went through something.

First find yourself a form or object to mold the patch around, that has the same radius and a similar curvature as the nose bowl area. Some parts of the nose bowl have curves that are more pronounced, some are more flat. Find yours. I found a pot lid that fit exactly the curve of the area to be patched. After cutting an over-sized piece out of 0.040 soft aluminum clamp it to your form and start hammering with a rubber mallet.

Fit it to the nose bowl from time to time, to see how much more you need to hammer.

With a saw, cut out special forms in wood to create the extra bends.

File the wood forms to the desired radius, and sand them smooth. The goal is a very smooth surface, since every little bump will be visible in the aluminum.

Carefully mark your piece and fit it to the form. Hammer the aluminum gently in place.

Verify the fit of your piece before you keep working on other areas.

Keep on working until the piece fits like a second skin to the nose bowl.

When satisfied drill, clecko and rivet evenly spaced around the edges. The nose bowl is no structural part, you can follow common sense and your aesthetic view. I have no pictures of that process, but here is the result.

As you can see, I was not perfect by any means, but IMO anything was better than the crack.

Finished cowl. As you can see, this is not the first patch applied.

Here is the cowling on the plane, showing the fuel pump adjacent to the patch.

Hartmut



Page last modified on October 13, 2010, at 03:56 PM