I'm about to install the engine oil dipstick door on my cowling. The point where the dipstick door needs to be placed is right on the crease on top of the cowling where it bulges out around the cylinders. The instructions show it up higher on the flatter part of the cowl, I know that won't work. If I cut the opening where it needs to be, I will have to bend the door to allow it to follow the curvature of the crease. that may be difficult as the crease is a compound curve. What have others done? Any help would be appreciated. Ron 

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Find a sheet metal shop with an English Wheel. They can make a door for you with the appropriate compound curve. When you cut out the hole in the cowling, take the cutout with you to the sheet metal shop so they can accurately duplicate the compound curve.

English Wheel Wiki

I recently cut the door as seen on the Homebuilt Help video.  Just as you said, it didn't work there, so I had to fiberglass it back in.  Now I'm back to the original (uncut) cowl.  I have a friend who is much more experienced with fiberglass who will help me cut it and use the cut out as the door.  I hope that will work. 

Got my door finished.  Added reinforcing layers to door and glassed in the hinge and metal plate under cowl.  Used cam lok fasteners to latch door.  Here it is pre-paint.

Hey Perry.

Did you flush rivet the backer flange before you fibreglassed it or just use glass? I’m working on mine now.


Just glassed it in.

Thanks Perry. How’s it holding up?

Doing fine, no issues.

I think your are on the right track...make an access door with the cutout portion of the top cowl.

just need a reinforcing frame of aluminum and your cutout out.  I also elected to use camlocks  HTH!  Dave...

You guys are the best. I'm going to go with Davids' method and use the cut out as a door. David, what did you use to cut the door out so neatly (a dremel cut-off wheel?)? Do you happen to have the part number for the camlocks you used? Thanks Ron

Ron, go here are you will find everything you need to know.  You will need the receptacle, retaining clip and appropriate stud sized camloc.  I believe I went with the -2 stud, and definitely with the Phillips head cad plated.


Dremel and a steady hand will do it.  I marked location by tape measure, sized as I felt necessary for my hand and withdrawal of dipstick. It turned out well and serves as a good visual access point for preflight inspection of that side of the engine.   ( I think Larry Ward's technique for positioning is a slick one!!)



I made my oil door opening using the existing hardware as the pattern to cut into the cowl over the dipstick. I did modify the final installation by putting two fasteners (one at each corner of the door)and it works great. I used a plumb bob hanging from the ceiling to locate exact position of oil dipstick. Then I put cowl back on and mark dipstick position from plum bob. Now when I open oil door, dipstick is centered in door and is easy to retract and insert. I carefully cut my door with my dremel tool. The thin cutting wheel works well and the gap once the door is installed is minimal. Good luck!

I did the same thing (cut the door out of the cowling), and one of the fiberglass corners turned up.  I found out that if you warm the fiberglass/epoxy with a heat gun it will easily bend so I heated it and let it cool down in the new perfectly fitted shape and it stayed that way.  I had to hold it while it cooled.


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