Chapter 14
Center Main Spar


Well... Now comes the time to build the part the wings bolt onto. The plans were pretty true to form here.

The more attention you pay to get the jig perfect, the less fudging you'll have to do later on.

The Jig.

Got all the stuff from Home Depot and put it together IAW the Plans. Mark all the various W.L.'s and B.L.'s you can. They will come in handy later. I used drywall screws to hold everything together, and Bondo to hold it to the table.

I used 4 shims adjusted to the necessary width to get the correct thickness of the urethane at the ends. Worked pretty good.

I used numerous clamps to hold things in place during cures.

Hint: Use as few foam joints as possible during all stages of construction when using urethane foam. You'll be glad you did during the sanding process.

I use alot of drywall screws to hold things together while assembling the spar foam instead of the plans method. That worked well too.

ALERT!: When sanding the top spar cap troughs, make sure you notice the differences between the center and end sections. They taper in a manner that will leave you too deep if you do them the same way you did the bottom troughs.

Here's a shot of the main spar with the hardpoints placed. Getting ready to layup the shearweb!

1st shearweb layup done. The Dritz Electric scissors really came in handy here. I was able to get the edge of the glass right up next to the shearweb trough without disturbing the weave. MUCH easier than the Wiss Shears!

Here's the setup for the fences.

something I wish I had done: Make your fences the EXACT height of the sparcap thickness. Maybe obvious for you, but not me. I was fortunate mine came out OK, but forewarned is forearmed.

Here I am straightening the fibers in the sparcap. The white tool really made it easy. I think it's called an adhesive spreader.

Squeegie-ing the excess epoxy out of the spar cap while using a blow dryer to speed up the wetting out process.
I'm using nitrile gloves in this one. I still get epoxy in the fingers due to various sharp edges encountered. My fingernails are starting to exhibit weird signs of possible systemic contamination. 

Guess it's time to get the butyl gloves.

I used sandwich bag plastic to keep air from getting between the top and bottom layups.

The Finished Product!!

This was another one of those areas where accuracy was paramount.  I think I may have measured level fore and aft 33...... no... 34,000 times.

Mounting the Main Spar

Here is a shot of me cutting some for inch-wide BID tapes in preparation for glassing the spar in place.

The lines you see on the table helped me to align the cloth, so it can be easier to cut accurate 45° tapes.

And yes, those of the famous Dritz electric scissors.
It took me about four hours of taping


Here I am during on of the MANY pulling-out-sanding-pushing-back-in operations.

I gotta say here. I sure am glad I didn't accidentally knock the level/plumb boards I bondoed on a couple of years ago, when I drilled the wings. Hopefully, I got this right. Otherwise, I'll be flying sideways or in perpetual circle. Time will tell....

Did I install this thing upside-down????

The Plans make a pretty big deal about getting things square/true/level. This part, to me was just about as exhausting as the landing gear fabrication. (Don't really want to do THAT again.)

All in all though, this was very rewarding, in that the fuselage actually has something sticking out from the sides which might resemble wings some day.

Now... If I could only get an engine so Wayne Hicks will sweat a bit worrying if I'm going to beat him in the air...

Now... Onward to the Strakes!!!!

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