NACA Scoop

I used a weight or two, or three, to hold down the foam that gets microed to the top of the fuselage bottom when you start to install the NACA scoop. I count 16 weights. If I had this to do over, I wouldn't do it the same way. Weights worked great, but, I used a combination of 1" and 2" foam instead of all 3", or mostly 3" foam. I ended up with a ridge of sorts, when the sanding and contouring was done, where the micro made the foam hard where it was jined.

Here's a shot of the foam after installing, but before sanding. I worked really hard to get the inside edge exactly the right shape.

Weighting down foam as it is installed between the firewall and aft landing gear bulkhead.

I used double-sided tape to affix a small piece of thin plywood to the back of the aft landing gear bulkhead. This helped the installation of the 3/8" poly foam - keeping the right amount of gap for the joggle.

Starting to sand the foam to shape. The plans call for you to make this sanding block, it works very well. I still am using it, about 2 or three chapters later, and haven't changed the sandpaper yet. Doesn't need it.

This shot shows the aft foam installed, and that forward of the forward landing gear bulkhead roughed to shape.

Here's the 3/8" poly foam installed with the overlap for the joggle. Not too tricky of a task, but, I was pretty proud how nice it turned out and took a picture.

As you can see, using a piece of 1" foam and a piece of 2" foam was not the way to to. Once sanded, inevitably, the joint between the two revealed itself and made a sort of ridge when it didn't sand as well as the other parts. I am not really sure why I didn't just order the 3" and use it (it had been missed on an order I'd placed) rather than going ahead and using 1" and 2". Desire to move ahead? Thought I was smarter than the plans. Never make that mistake...

I used pieces of 3/8" poly foam, cut to the right thickness, to help me judge when I had sanded the urethane foam far enough. Worked pretty well.

I used these straight edges to clean up the joggle with my router. I set it to the right depth, put some weights on the boards and ran the router against them. Cleaned up the edge of the joggle real nice.

When I glassed the NACA scoop and the joggle, I made these wood pieces to help the glass stay in the joggle. They have 45 degree angle cuts on their ends, this forced them out and down as the weights were applied. Kept the glass in the joggle pretty well.

Here's another shot of the weights and the wood pieces I made. In case you were wondering, yes, they did fall once. I was cleaning up after installing all of this, bumped the fuselage with something and it all came crashing down! Not too worry, though, the weights just fell through the slot between the two landing gear bulkheads and hit the floor. I reset it all up, made sure I didn't bump the fuselage again, and they stayed there until the next morning when I checked everthing.

The whole assembly is visible here. I have seen lots of other ideas on other web sites - and frankly - don't think there's a really good way to do this. I ended up with some pretty decent bubbles in the areas just forward of the joggle that had to be filled. This is a very trick part to glass - spend some time thinking about how to set it up and do your best.

A close shot of the joggle wood pieces. Of course, all the wood pieces are covered with box sealing tape to prevent them from sticking to the glass as it cures.

The finished scoop. Looks pretty good from here - my joggle is pretty straight and deep. Like I said above, however I had some pretty decent air bubbles in the glass just forward of the joggle. If I did this again, I'd probably dado a step sort of cross-section in the wood, allowing the piece to go into the joggle but also pushing down the glass just forward of the joggle.

Another shot of the joggle. Looks pretty good - straight and deep enough.

A shot of the joggle in the after section. Pretty good, not quite as good as I would have liked, but, OK to move on!

Next step is Contouring the Bottom