Chapter 14 - Step 4

This step involves glassing the forward face and attaching it to the rest of the spar. Then the spar caps are cut in the top and bottom of the spar.

May 9, 2002. Here is the inside face of CS4 after being glassed and peel plied. I propped up the ends 5" like they will be on the spar. The glass was added this way to ensure it will lay correctly on the spar.

Trough Sander May 17, 2002. Sanding the spar troughs was made fairly simple with this sanding block. It is simply two boards glued together at a 90° angle. One face has 36 grit sandpaper attached to it. The face with the sandpaper is exactly 3" wide - the width of the spar cap. The only thing I would do different is to make both pieces of wood the same length. With the other piece being a bit longer, I couldn't sand the area where the spar bends. I had to do that region by hand.

Sanding Bottom Trough May 17, 2002. Here is the sander in action on the bottom trough. Before using this block I did as the plans call for and measured the trough depth and removed the 1/4" foam and micro. I then used this sander to sand the urethane foam to the proper depth. I simply used the denser, 1/4" foam as the stop. It is pretty easy to tell when the urethane is sanded to the same depth. The only thing to be careful about is making sure you keep the half of the sander sliding on the aft face good and flat on the aft face. If you don't, the trough may end up being non-perpendicular.

Completed Bottom Trough May 17, 2002. The bottom spar is fairly easy because it is straight and there is no twist. Here is one half of the spar cap trough with all four jigs in place. You can't tell in this picture but at one of the jigs, the trough is a tiny bit too deep toward the forward face. I must not have kept the sanding block flat on the aft face in that area. It's not too bad and won't be a problem.

Completed Top Trough May 18, 2002. The top spar cap trough is a good bit trickier than the bottom. At least in the outboard sections due to the "twist" in the trough. I spent a good time looking at the cross section drawings and the jigs. It seems simple enough looking at the drawings but when you pick up the sanding block - you really need to stop and think about exactly how you are going to do it. The middle section between butt lines 33 is just like the bottom trough - nice and straight. I did that first because it was easy.

End of Spar May 18, 2002. Here is a shot of the end of the spar. You can obviously see the top and bottom end jigs in place. The top trough is on the left. You can see the bottom trough is straight while the top trough angles a bit. This angled section is what makes you think a while. After some careful thought and triple checking of dimensions I figured out a fairly simple way to make it right - I think.

What I did was to set the end jig in place on the end foam. I traced the jig on the end foam and then sanded the end foam to the line. I then used the square sander I used for the rest of the trough and sanded the trough to the depth the trough would be if it wasn't sloped (Confused?) I did this only on the last 6" of the spar. I then layed a yardstick on the aft face so it would act as a stop for my sander. The yardstick was angled so it would allow me to sand the spar trough from B.L. 37 to the end as if the trough was not sloped. After sanding that much, all that was left was to sand, by hand, just a little more for the angled trough. This was done slowly and carefully to avoid sanding too much.

The description is much more confusing than it really was and the trough came out very nicely. This all assumes of course that I properly understood what it was supposed to look like in the first place.