Top longeron reinforcements

The top longerons get a few fiberglass reinforcement strips. Three UND layers get glassed over the length of the stiffeners and then a single BID (at 45 degrees) gets glass over the entire 103" span.

Here I started by cutting the 60" UND strips that will go over the stiffeners.



Then I cut the BID strips. Since the plans call for a 45 degree orientation, I had no other choice but to use 2 strips to span the entire 103" length (then double for the other fuselage wall).

Before glassing the top longerons, a fillet of flox goes on the lower lip of the top longeron. This is to aid the fiberglass cloth to curve around the edge. Here I am using the 'baker's icing on the cake' trick.



Oooooooo... that is a nice looking fillet if I may say so myself!

Since I wanted to glass the left AND right fuselage longerons on the same day, I laid both fuselage walls on my 'temporary' table. This left my workshop table free so that I could prepreg the layups.

Prepregging - this was harder than I thought. I laid the 3 strips of UND, poured resin in between like a lasagna and squeegeed it out. I then folded the top plastic piece over and cut the strip with a nice edge (the edge that would go on the lower lip of the longeron; the top edge overhangs and gets knife trimmed later). When I went to peel the top plastic off, it pulled the top layer of fabric off with it, making a mess! I fixed it back up the best I could, and positioned it onto the longeron (the middle section where the stiffener is located).

I then peeled the plastic off and worked the glass in, making sure to wrap and conform around the stiffener tips onto the longeron.

Here is an overview shot of the UND installed.

 Close-up of the UND strip that transitions from stiffener to longeron.

I then repeated this process for the left fuselage wall.

 I then applied the single layer of BID. At first, I used the prepeg method. HUGE mistake! BID does not like to be pulled from plastic as it will elongate and stretch. I learned my lesson and decided to proceed by using a brush to apply epoxy all along the top longeron, then placed the BID strip over it, and wetted it out using the brush. This method worked great as the brush helped tuck the BID strip into the fillet corner and remove all air bubbles that were present. I then peel plied the edge that meets with the fuselage wall.

Here is a close up of the peel ply and glassed top longeron.

I left a considerate amount of overhang. This was because I did not want to knife trim since I was afraid disrupting the layup would introduce unwanted air bubbles. Instead, I opted to let it cure as is, and use the vibrating cutting tool and router to trim later.  

After a full cure, I used the vibrating multi-tool to cut the edge as flush as I could. I made sure not to cut into the longeron or foam. Notice how I left about 1/8" overhang. The router will later trim this flush.

Ryobi router to the rescue! Damn I love this thing! Using the router, I flush trimmed ALL edges flush to the lip of the longerons.

Here is a better angle showing how the flat bit roller rides along the longeron, cutting everything above perfectly flush!

I took a picture halfway into the trim to show the 'before' and 'after'. Notice how the router cuts the foam AND the fiberglass perfectly flush to the longeron.

This worked so well I then flush trimmed the lower longeron edge flush using the same method.

Make sure you wear pants (NOT SHORTS!) while doing this kids! Holy crap did this make a mess in my garage!

But the results speak for themselves... a perfectly smooth, flush trimmed top and bottom edge!