Good Afternoon Everyone,
Before I go trimming the bottom half of my B model cowl, I wanted to see if anyone else needed to trim their lower (and probably upper) cowls in order to get the face at the prop hub to the proper spot. It looks like I need to trim 1.25” off of the back side of the cowl to land the front in the proper place. I think the other option would be to use a 1” spacer but I’m not sure that’s the way to go in this case. Just wanted a sanity check before trimming. Thanks!
Altho I have the A sonex, vert split cowl, I remember the same type of problem. I remember thinking the fiberglass molds are specifically longer than needed, and i feel it to be correct to shorten the length to meet the prop hub correctly. These things are all part of that 51% rule, as you know! And, the canopy fit looks great!
I had to trim my cowl a LOT. Pro tip - trim a little at a time. I ended up having to add some material at the end because I took too much off at one point.
Also, I believe you will be challanged to get the top cowl to fit with your current engine baffling - although they look really nice. The clearance from the #1 cylinder fins to the top cowl is very close.
Bill
N67WX
I also have that Merit Badge.
Yup. Although mine is a legacy “A” model, same experience. A lot more trimming than expected. I’ll also echo that you can expect to take a lot off the baffles.
Go slow. Removing material is relatively easy. Putting it back…..not so much.
On the other hand, as I’ve said before, anybody can do it right the first time. To fix a screwup takes real skill.
I prefer not to find out! 
Thanks for the advice, everyone! I know every build is a little different but I’m glad I’m not wandering into uncharted territory. As far as the baffles, they for sure need trimming; they are still in the pre-bent form straight from the FWF kit. I decided to take a break from the FWF manual to work on the cowl, but will go back and finish once I know how much I need to trim and how much baffle material to add. All of you guys rock and I appreciate the quick advice!
Not cowl related, but I’d definitely mount that VDO sender remotely.
On my A series, trimming the cowl to match the prop hub made for zero clearance to the sump. I added a 5/8” thick spacer to the prop, .simply machined from flat 6061T6 aluminum, with the holes very accurately located (on CNC mill) and reamed to accurate size, then made longer bushing again with very close tolerance with a slight in diameter step between hub and spacer as holes in hub were slightly larger than the common 5/8” reamer used for the holes in the spacer.
Advantages: bushing are held square to the prop hub even if a bit loose preventing damage to prop. Also permitted better cooling airflow to cylinders numbers 1&2.
More info on that can be found on the Jab-CAMit forum files, cooling a 3300 in a Sonex.
At one point Price propellors was offering a spacer with the bushing cast or machined into it.
David A
Based on the recent feedback on here, that’s for sure on the list of FWF tasks before completion
Thanks for the info, David! I’ll take a look on the groups site for your solution to this problem as well. I’ve got a request into Sonex Tech Support for another set of eyes on the issue as well.
