Upper Wing II

4/2/2007

Next, I focused upon the tip bow. First I fitted the small nose rib at the outboard end. I decided to brace this rib to the main rib with a piece of spruce 1/2 x 1/4, this small piece I decided to glue in permanently to add continuity from the last main rib to the start of the tip bow. The pic for this is on the Upper Wing I page.

After spending a lot of time eye-balling and adjusting the bow, I then marked it and cut it, along with the spar tips to suit. The outboard angled strut was then added.

Tip: The angle strut is an internal piece. So it can be tricky to measure for length accurately. No one likes wasting spruce. This is how I measure for internal measuring: Say, the length is about 3', I use 1/4 x 1/4 x 20", 2 of. I place them both in the wing, one stick pressed against one surface, and the other stick the same. Then I marked a reference line in the middle where the two sticks overlap. Placing the two yard sticks on your strut on the bench ensuring the pencil line across the two sticks match, you can then mark off either end, resulting in a perfect fit.

To finely tune the gusset shapes I used a bench mounted 12" disc sander [a must-have in my opinion]. They were clamped in place with tie-wraps. I have seen pics of builders using string etc., but I don't know how to tie a knot under tension :0(, the tie wraps were a good alternative.

Next, I added the trailing edge. I notched it for the rib locations. Rinsed off any film inside with MEK, then glued on. Again, I used tie wraps where needed.

Tip: Mix some T-88 with fine sawdust, then place a blob on the very tip of each rib prior to pushing on the aluminium trailing edge - this will fill the small void on the inside of the trailing edge. If this small void is not filled, there is a chance the fabric will pull over time, therefore closing this gap slightly, resulting in fabric wrinkles.

I do recall Randy having a cool approach for the trailing edges:

- don't fit the trailing edge until the aileron is in situ. Then fit in one whole length, spanning the aileron too. Then cut. This way, you will get perfect alignment. [I couldn't do it this way because my pieces came cut to rough length]

- don't notch the trailing edge, but squeeze them flat at the rib locations instead.

I decided to notch because i) the lower wings are already done that way, ii) the notch holds the rib in place laterally, so no brass nail etc., is needed in the trialing edge.

You can see in the last pic, there is no tail rib yet [the one the center bow will attach to]. Normally the trailing edge ends at that tail rib, but I unfortunately cut my trailing edge short! So I have trimmed it to end at the first main rib. To remedy this, I will span the remaining gap to the tail rib with spruce, and shape it to match.