What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

How to blend and how far to blend

steve murray

Well Known Member
Fiberglass newbie here, long story short, scarfing to add material to horizontal hinge line on upper cowl resulted in upper cowl surface now sitting about .1" proud of lower cowl when the top and bottom cowl hinges are joined back together. I now need to build up mating edge of lower cowl to blend in my transgression.

1) Should I use few layers of fiberglass or epoxy & micro to build up the .1" height?

2) How far down from the hinge line do I need to extend this blending of .1" buildup? Do I go from .1" build up back to natural surface of lower cowl over 1" .... 4" other? Not sure if there is a rule of thumb for this?

Thx for the help
 
I personally would use only an epoxy micro balloon mixture. First sand the area to be filled with 80 grit sandpaper. Then follow with a light coat of straight epoxy and let it set until it gets tacky. Then I would follow with a fairly dry mixture of epoxy and micro balloons so it will sand easily. To make a nice transition I would use a flexible sanding block that would span over both the top and bottom cowling. A 1" wide piece of sheet metal with sand paper glued to it works well. When you lay this over the joint, it will tell you how far to extend the transition. Hopes this helps.
 
Thx for the tip John. I have been surprised how hard epoxy is to sand, I will definitely mix micro\epoxy towards the dry side if it reduces the sanding effort.:)
 
...long story short, scarfing to add material to horizontal hinge line on upper cowl resulted in upper cowl surface now sitting about .1" proud of lower cowl when the top and bottom cowl hinges are joined back together. I now need to build up mating edge of lower cowl to blend in my transgression.

Why not simply reduce the excess thickness on the upper cowl?
 
Why not simply reduce the excess thickness on the upper cowl?


Hi Dan

My goof up was the scarf joint on the upper cowl was too thick, and after riveting the hinge along the "too thick" cowl edge it now protrudes. I could remove the hinge sand down exterior service and fix the problem but I have already removed the hinge once and I am a bit nervous with all the filled holes in this area.

Steve
 
Hi Dan

My goof up was the scarf joint on the upper cowl was too thick, and after riveting the hinge along the "too thick" cowl edge it now protrudes. I could remove the hinge sand down exterior service and fix the problem but I have already removed the hinge once and I am a bit nervous with all the filled holes in this area.

Steve

In a similar situation, I added one ply of glass an inch or two wide along the edge, then used micro to feather the whole thing. On the relatively flat sides of the bottom cowl, you'll probably need to feather 6" or thereabouts to make the fix disappear. It'll take less in the curved areas. As always, apply micro a little thicker and spread it a little wider than you really think is necessary and your odds of a re-do go way down.
 
Back
Top