Horizontal Spar Bubble Repair

I had previously circled some bubbles between the core and glass on the spar that needed repair. Today I sanded them clean to get ready to micro and glass them. This will allow me to move on with hard point installation.

Using 60 grit, I sanded away the bubble being very careful to cause minimal damage to the core material. I deglossed the surface about 1″ around each bubble to prep for glass.

A closeup of some sanded bubbles. I’ll vacuum these out, clean the area with acetone, fill the bubble with micro and glass with one layer of BID.

Horizontal Spar Hardpoints

I did this last Monday 8/20/17, but didn’t get to post until today.

I did this exactly to instructions, but after I wished I had deviated a little and used my laser cutter.

From 1/4″ aircraft grade poplar plywood, I cut 20 1″ circles using a hole saw. I trimmed the flashing with a knife and sanded the loose bits off the sides and face. I did not sand them smooth.

2×4′ was the smallest I could order from Aircraft Spruce. Looks like I could have fit them all the way across and saved material if I’d thought of it sooner.

20 rough cut circles.

After trimming and sanding. Rough edges will help epoxy grip. All the loose material or over-sized bits are removed and they should fit nicely in the spar holes.

Before and after trimming and sanding. It took a long time to do them all. Next time I’ll just laser cut them a little larger and sand off the heat affected zone. Less mess and I’ll have a nicer finished product.

A Little Bit…

After I pulled my last set of ribs out of the flange molds, I haven’t had a lot of time to work on them. So I started trimming the flanges a little bit here and there as I had time. I found a hack saw blade works really well for this.

On Aug 7th I put the flanges on last 4 ribs and trimmed them the next morning. A hack saw blade with handle on one end really works well for this. It’s long enough to trim the whole flange, but gentle.

Untrimmed ribs just out of the mold.

Closeup of the trimmed flange done previously and the untrimmed side just demolded.

All finished horizontal ribs together.

HRIBs Continued

I flanges 4 more ribs tonight. 2x HRIB1, HRIB2, HRIB3

Both HRIB1 had bubbles under the glass on one side. I sanded and repaired these like on the Spar. 

I had done a bubble repair on HRIB3 previously, but I didnt fill the bubble with micro. I sanded out the bubble, cleaned the surface and glassed over the divot. This left an indentation about the size of a nikle. I wasn’t happy with the indenation on the rib and I wasn’t sure of the reduction in strength. Since this repair was already dry, I filled the divot with micro and glasses over the top so the rib, once again had a flat surface. 

HStab Spar 2

I put two layers of BID on each side of the Spar joint and repaired a bubble.

I sanded through the layer of BID on top of the bubble with 60 grit being careful on to disturb the foam and roughed up the area 1″ around. I filled the void on top of the foam with micro and cleaned any excess from the surrounding glass.

As usual I laid up the glass between plastic. I put one layer of BID over the micro and stippled it smooth.

I put the two BID stacks, one on each side and covered the up side with plastic to set.

After it was gelled this morning, I trimmed the excess with a knife. I also marked any of their bubble with a pencil so they could be repaired later. Before repairing them, I will lay out and cut the hard point for the elevator. There’s no point in repairing them if they just get removed for a hard point. The pencil makes them obvious so I won’t miss them later.

Horizontal Stabilizer Spar

I got the horizontal spar started today. The two sides were sanded on the edges to be the correct size and be symmetrical. The face of each side on the joining edges was scuffed with 60 grit and 1/4″ of foam was dug out from the ends. 

I made a 20gram mix of 5 min epoxy and thickened it with flox to be like thick cream cheese. I then packed the ends of each half where I had dug out the foam leaving a lot sticking out.

I made center marks at 3 places on each half and put plastic wrap over the location of the joint. I put the two halves together and lined up all the dots along the laser. I scraped off any excess flox.

The two halves aligned. Noted the pencil alignment marks.

I sanded off any excess 5min flox and took off the shine with 60 grit and trimmed the edges with a utility knife. 

Last thing I managed to cut 2 layers of BID for both sides of he joint. I cut the top piece to size and then added 1/2″ on both sides to add a slight taper in thickness to avoid stress risers.

Flanging Part 2

I added flanges to the opposite sides of the ribs I had done previously.

BID for flanges is cut at 45 deg. First I cut a strip off the main roll to reduce waste.

Then cut strips at 45 deg approx 2 in wide.

I prepped the ribs by deglossing the surface with 60grit sand paper and wiping it down with acetone. I also knocked down any edges sticking up from the first flange so the overlapping glass on the second could lay flat. 

I wet out the BID between two sheets of plastic like previously, but this time I wet out the two ply layer together. Befor I put the two ply layup in place, I wet the surface with some catalyze resin.

Two plies BID wet out and squeeged out. Note the excess resonate the top and bottom.

HRIB2 after demolding and before and after trimming.

Flanging Part 1

2 hours to glass flanges on one side of 4 ribs. The jigs I made were all 12 inches as per the instructions, but that is not long enough for HRIB1 so I will have to make longer jigs. Each flange has 2 layers of BID as per instructions.

I started by wrapping the jigs in plastic wrap and  inserting the rib. I used 60 grit sand paper to take the shine off both sides of the rib first.

The BID was cut to size and I poured catalyze resin in a stripe down the middle of each piece of glass. I then layered plastic on top and used a squeegee to spread the resin from the center of each piece out to reduce air bubbles. I then squeegeed off excess resin to the long ends.

When done, the glass was totally transparent.

I then opened the plastic and peeled each ply up being careful not to distort it. This worked well for the smaller ribs, but peeling up the larger pieces of glass was more difficult without distortion. I think when I get to the main wings, the flanges will have to be glassed in place on the jigs.

6′ Sanding Block

Since I used a band saw instead of a knife to cut out my spars, the edges are a little rough and a little over size. So, I skipped ahead a bit in the instructions and saw this idea for big sanding block. This will make nice straight spars.