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So I did the split cowling modification back last fall and am finally getting to the final trim and fitting. I am running into a problem with the upper half of the cowel Where the upper half comes down and over the edge to the side of the fusealage it sticks out from the airframe. It is like there was residule stress built into the cowling when it was molded. The top half is flareing out towards the back. I am planning on holding the top and bottom halves together with screws and nutplates but since the engine mount is right at the cut line I can only put a screw about 3" away from where the bluge/flaring is occuring. Has anyone else that has done the horizontal split encountered this? How did you get it straightened out? The only way I can see to make it work is to drill and tap the engine mount but would rather avoid it if possible.

Keith
#554

I have just finished the split cowling mod and noticed the same problem that you did except possibly not so bad it seems to magically change shape as soon as the pieces are parted. I put in nutplates and screws the first as close to the engine mount as I could and in this case it solved the problem although it is actually out about 1/4" which I am living with. If it should get worse I will drill and tap the same place that you are contemplating. If yours is real bad I would just drill and tap and be done with it.
This "easy" mod was a PITA but after much fitting and grinding and sanding it finally fits.

ken

I attempted the horizonal split and had the same issues.
The biggest kicker was trying to get the prop gap aligned.
I finally abandoned it and re-laminated my cowl back to the stock vertical split.
By far the worst part of the Sonex build is the cowl. I'm not sure how they could make it easier.

Thanks for the advice. I am too far into it at this point to turn back now. It looks like drilling and tapping a hole at the very back is going to be what I have to do. If I were to do it all over again I would have made a metal cowel with a fiberglass nose like some of the cleanex aircraft have done. I am much better working with metal than I am with fiberglass.

If builders had to start building an airplane by fitting the cowl and canopy I don't think there would be any builders left.

Keith

Now you all have me thinking if splitting the cowling is a good idea. I'm a ways off, but I was/am considering doing this mod. If anyone has pictures of the issue(s) or of a final fitting, I'd be interested in seeing them. I'm sure others would be too.

Keith, good luck with getting the cowl to fit the way you want it to!

I will see if I can get some pictures this weekend.

Keith

kmacht wrote:...If I were to do it all over again I would have made a metal cowel with a fiberglass nose like some of the cleanex aircraft have done. I am much better working with metal than I am with fiberglass...

Not only the cleanex builders have done this,
Here’s a German builder who recently completed his metal cowl with homemade fibreglass nose, He has the RevMaster engine hanging from his Sonex.















More info can be found on his website (unfortunately mostly in German):
http://www.loeff.de/eingangsseite.html

Neat thread!

I definitely won't be doing this mod after reading this. Way too much for me to consider. But looking at the German cowling made me think there are some very' very creative Sonex builders out there! At first I thought it was ugly, but after looking at it a bit I think it is kinda cool.....


Robbie
Sonex 1517

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I saw a perfectly executed horizontal split cowl at Airventure. It can be done.

Sonex1517 wrote:At first I thought it was ugly, but after looking at it a bit I think it is kinda cool.....

If you think that one looks cool, have a look at Dana Thurston's J3300 powered Sonex, similar concept: