I have been concerned about the
silk covering "bridging" or wanting to pull away from the fin's bottom
concave fillet at the bottom near the front. So I added some balsa fill
wood above the bottom fillet to give the silk a surface to stick to that
is in line with the fin's ribs. A discussion and pictures have been
included herein. ........................Tandy
The bare fin primary structure shown below
requires ribs, spars, and all sorts of fill wood to give it its final
The four symmetrical fin ribs along with the
internal spar were glued into the primary structure. A soft balsa block
was then carved and sanded to the top contour of the stab to make the
fin's root rib. With fin mounted in the stab slot, this contoured block
was glued to the base of the fin as shown below.
Next soft balsa fill strips were glued to the
trailing edge as shown below.
Then soft balsa fill strips were glued to the
leading edge as shown below.
When everything was dry, the fin's leading
edge, trailing edge, and root rib block were carved and sanding to shape.
The fin's resulting foot print is shown below.
This shows the fin mounted in the stab slot.
Notice the shape of the fin's forward fillet now.
This is a nice close up of the fin/stab
This is more of a frontal view of the fin/stab
In the picture above, you can see that when I
try to cover the fin, the silk will want to "bridge" or pull away from the
fin's bottom concave fillet, which I have been worrying about. So I
decided to add some balsa fill wood above the bottom fillet to give the
silk a surface to stick to that is in line with the ribs above the fillet
as shown below.
This balsa fill wood was then sanded and
contoured to shape as shown below.
In the picture below, I have drawn on a series
of vertical lines. Think of them as straight lines of silk covering that
stop at the point where the fin's bottom fillet starts to increase in
thickness. If I have explained this right, you will see that the silk will
now some flat surface to stick to and should not pull away from the bottom
fillet near the front of the fin...................Tandy