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.

Cutting Tail Parts

Tonight I layed out the long H Stab and V Stab parts and got them glued down and cut out all the parts. Time, about 2 hours.

I just loosely cut out this template in the interest of time and it actually ended up making it easier to see the line when I was cutting them out.

All the parts for a complete horizontal and vertical stabilizer. They just need to be sanded to match each other so my wing surfaces are nice and flat and symmetrical.

H Stab part cutting

Today I printed the rib templates and got them trimmed and taped together. I had the chance to get one rib cut out. 

I rough cut out a piece from the 1/4″ stock, then lay the HRB1 template on it and sprayed a light coat of paint. I was left with a nice silhouette to cut out on the band saw.

After cutting I sanded the edges smooth.

The result was perfect, but it took a long time to cut out the small piece with a knife and paint it. Tomorrow I will make the spar template and then spray glue them all directly to the laminate. I thin I can get all the spars and ribs for both vertical and horizontal stabilizers and elevator from this one piece.

H-Stab 2

I just finished the reverse side 1/4 foam that will become the spars and ribs. This time I mixed my micro super thick and spread it really thin. This made us easier to get it flat and I feel helped avoid bubbles under the BID. 

I again used the bias cut method for cutting the BID recommended in the manual. It worked great and the key was how I rolled up the fabric after cutting it. The first piece I rolled with the longest edge exposed and unrolled it along the 24″ length of the foam. The second piece I rolled with the angle cut edge exposed and laid it on the first to get the proper overlap and unrolled it diagonally. I left the pieces untrimmed and I’ll cut the excess off after cure. I used a lot of extra resin, spread it gently very thick and gave it time to soak in before working it in to the BID in two directions along the weave and removing excess.

The back side of the 1/4″ foam with excess fabric left. I’ll trim it after cure.

Horizontal Stabilizer

Tonight marks the start of the KR-Super2 build. I completed glassing the first side of a 2’x4′ 1/4″ Last-a-foam panel and one side of two 3/8″ panels for h-stab skins. Work was done according to Chapter 2 as per instructions. 

I was initially going to use Ecopoxy for this build because it was described as odorless and non-toxic and ok for structural parts. I purchased a gallon kit. Later I became worried that is may not be a good substitute. Aircraft Spruce was not able to provide a mechanical properties of the Ecopoxy resin system and I also read that the Aeropoxy does not contain the cancer causing substance MDA and is tested by Rutan for all structural use. I switched back to the Aeropoxy. Ordered a gallon kit from Spruce 3pm Thursday and it showed up 5pm Friday with UPS ground. Not bad. That allowed me to get started tonight.

All-in, tonight’s work used about 1/4-1/3 of a 1 gallon kit. About $30-40 worth of resin.

I laid out a sheet of 1/2″ ply to provide a flatter surface than my garage floor. The plastic is to protect the wood.

I cut the BID for the first two sheets as per instructions. The final piece I straight cut. When following the instructions I only had the small triangles as waste. Straight cut definitely has more waste, but the large leftover rectangle can be used elsewhere in the future. The bias cut method proved very hard to keep the cloth weave aligned as I was rolling out the cut sheets on the micro’ed foam. It took forever to get the weave aligned again. The overlap of the two pieces of cloth is also heavier. For future glassing, I think I’ll stick to straight cut and accept the waste to make a better, light part in less time.

Above, 45 degree cut cloth laid out and trimmed to size.
Overlap of 1.5-2″

Straight cut cloth trimmed to size.

Cut BID rolled up and ready to go.

Mixing station set up. I would pour out the amount of resin needed, weigh it. Divide that by 100 and multiply by 27. That gave the exact weight of hardener to weigh out. Tonight’s project used about 1/4-1/3 of the Aeropoxy that came today.

I printed and bound the. Hold manual for easy reference.


My first attempt at mixing micro. It was a bit hard to spread. I mixed subsequent batches thicker and it spread on much easier.

Edit – the next time I mixed the micro 1:1 by volume with catalyze resin and this consistency was much easier to work with.

1/4″ foam nearly done with micro. I used an extra large scraper to speed things along. Just had to be careful to keep it flat and not let the edges dig into the foam.

Edit – the next time I used my yellow plastic squeegee to spread micro. Though it’s smaller, it seemed to work much better and faster.

Rolling the glass on to the foam was so easy with one big single sheet. Smooth by hand to eliminate air gaps between glas and foam.

Completed side 1 of the 1/4″ panel that will become various structural parts for the horizontal stabilizer.

I did the 3/8 panels with two glass pieces cut at a 45 degree angle. This was much less wasteful on the glass, but hard to align the two pieces of cloth to get the right overlap while keeping the weave pattern intact. 

Closeup of a finished panel.

Three panels with glass on one side. The 1×2 strips will give the wing skin panels a small curve that helps them conform easier to the airfoil shape of the h stab. 

Total time start to finish, about 4 hours.