Estes DARC-1, #7307 Build Part 4, Clearing The Fin Slots

The fin slots have to be cut from the blow molded conical body.

First things first - Start with a new, sharp blade! 

Take your time - don't attempt to cut through the plastic wall with one pass. 

The widest sides of the conical body have the thinnest plastic wall!.

The fin slot area plastic is thin. Go light with your knife, you could go through the plastic when you don't expect it.

Notice the pencil line I drew around the raised fin slot before doing any cutting. The pencil line will help visualize the edge when cutting.

I don't normally use my X-Acto knife with a #11 blade, but I will on this cutting chore. I want more control than my break-off blade knife. 

If anything - cut the slots a bit smaller than needed. You can (and will) widen the slots to fit the fin thickness.

Even cutting right at the sides of the long raised hump, the cut slot is inside the pencil lines.

You could shave the sides with a knife blade, but I found more control using a small flat diamond file.

Use a scrap piece of the balsa sheet to check the fit of the fins. 

TIP: Don't use the kit fins to check the width, you could scar them up doing test fittings.