SonexBuilders.net

Greetings Builders...

My Sonex #325 now has an AeroVee engine with an older (non-'universal') cowl, which required me to cut the cowl to allow the valve covers to protrude. Just wondering if anyone on this forum has done likewise, and wondering if anyone has experience with either purchasing or fabricating 'blisters' to cover these spots. Thanks!

I thought only the Onex's had exposed valve covers and that all the Sonex with aerovee's had no problem fitting even with the older cowls?

Nope.

Really early cowls had blisters/cheeks for the valve covers.

My Sonex/Aerovee has the same cowl. The blisters are not meant to be cut out but enclose the valve covers. To get mine to fit, I had to fiberglass about an inch to each side at the center seam.
Alan
Sonex 568

Thanks, Alan, but what blisters are you referring to? This is my question: where to get blisters. Or how to fabricate.

I thought they were part of the old Aerovee cowls. I have a picture from Sun-n-Fun 2000 or so, the factory Sonex had them. When I get a chance I'll find and post it.

I believe the cowling came with these back then...

To fabricate, make a plug mold from foam, dense foam that can be sanded and shaped is best. You will be better off making two (one for each side). Once your happy with the shape use the foam to do a wet layup of fiberglass and resin. A form release can be applied to the foam or just lay the f/g on the foam and when done you'll have to scrape away / sand off the foam that bonded and clean up the inside of the fiberglass area (with more resin and glass or body filler.

Your going to probably need 2-3 layers of glass and resin, and depending on how you make it- it can be done on the cowling with overlapping layers to the existing cowl (remember to sand away the gel coat so your bonding to fiberglass/resin and not gel coat)...or if you make the blister separate from the cowl then you will need to marry this to the cowl with a few layers of glass and resin. Finally smooth the parts out with light weight body filler...and your ready to sand and prime then paint.

Might be easier to put a request out for anyone selling their universal cowling who switched to the new horizontal split cowl, or just go for the new cowl direct from Sonex.

Making the parts isn't hard just time consuming:

Thanks, Scott. Was hoping for pre-fab bumps that I can glass on, but if it turns out that they are unavailable, I might just go this way.

Here is the picture I mentioned.