I’m sure that everyone’s composite moldings will be slightly different, but when I test fitted my Fin fairing, it wasn’t quite high enough … in other words the top didn’t line up with the rudder top fairing.
I played around with different options to solve the issue, but since the flange depth on this fin fairing is 5/8″ rather than 1/2″ on the others, I decided to it fit slightly raised in order to compensate, as can be seen in the picture.
The rear edges have to be trimmed to match the rudder and leave a minimum of a 1/8″ gap.
Also I added a flox mix inside the front top edge to allow adjustment of the front profile to match the fin leading edge.
It takes careful adjustment to make sure the fairing is aligned correctly in all plains.
Once satisfied it is sitting correctly, it’s match drilled as usual.
Then the layup for the rear face is resined/floxed in place.
When adding the flox & cloth to the inside, I added some flox mix inside the front top to give more material for trimming the front profile as required.
I also added some micro balloon mix to the rear top, again to allow adjustment to match the rudder profile.
I used NAS1149FN416P washers on the holes to give extra strength to the countersunk holes for the pop rivets.
Actually, the other benefit of the washers is that they provide secure centering for the countersink bit pilot.
So here it is attached, showing the amount I raised the rear in an attempt to improve the fin/rudder profile match.
I guess this is only possible if you are intending to fill & blend the join.
A micro balloon mix soon covered up the join!
You can also spot in the picture where I had to adjust the front profile slightly to match the fin … hence the flox addition.
The micro balloon fill at the rear top would have been much larger had I not raised the whole fairing slightly at the back.