Speed brake glassing (inside)

Now that the speed brake was resting on my workbench, it was time to glass the inside of it. A lot of prep work had to go on before glassing though... let me explain...

First I had to clean up the mess the 5-min epoxy made on the fuselage recess. This required a lot more sanding than I thought.

I then test fitted the piano hinge. The plans calls for 8" worth of piano hinge; however, the tips were rubbing up against the 'transition' area...

Here is a close-up of the 'transition' area. It's hard to see in the picture, but the tip of the piano hinge was laying up against this area... so it would not lay flat onto the surface.

So I took it back to the band saw and trimmed it down by removing a slot from each side (it now has 15 slots instead of 17 as seen in the picture before last). There we go! Much better fit!

I then moved on to making the LB19 doubler. This was cut from 1/4" plywood leftover from the firewall. The plans say to cut a 3"x5.6" rectangle - however, since I am mounting an electric actuator to it, I widened the dimensions to 4"x7". Using sandpaper, I rounded one edge so that it will give the piano hinge more room to swivel.

Since LB19 rests on top of the piano hinge, a shelf must be milled out so that everything fits flush. I reassembled my table router and put a flat bit on it.

I adjusted the height until I had it just right.

Vuala! Instant shelf complete!

Oooooooo! Look at that! Nice and flush!

Look at how the front lip is rounded so that it won't come in contact with the other side of the piano hinge when it is rotated around.

I then cut the foam to make room for LB19 and the piano hinge and test fitted everything together.

I dipped the hinge in the alodine solution... but it ended up not working. Looks like the alodine I had ran out of juice! Oh well... I decided to continue since 95% of the piece will be embedded in epoxy anyway.

It was now time to remove enough foam to make sure it would not come in contact with the recess of the fuselage - remember, the foam was epoxied to the recess - so after glassing, it will grow slightly in thickness. In order to make sure it will remain flush with the fuselage's belly, some material must be removed. I removed enough material to maintain a thickness of 0.5". I placed the heavy 'duraflame' box in back to keep the assembly from sliding.

Just to make sure I was in the clear, I rolled up some marble-size clay balls and scattered them around the recess. I then placed the speed brake on - pressed down hard on it squishing the clays - and then removed the speed brake. 

Using calipers, it showed a 0.2" clearance between the recess and the speed brake - this put my mind at ease.

Now I had to make sure I had enough clearance around the perimeter. I figured 0.25" all the way around would do the trick. So I began removing material using a knife...

Everything was then sanded down nice and smooth to give a nice transition when glassing.Notice how I finally got rid of all the clay around the perimeter that was stuck on there from when I glassed it on the fuselage - the clay kept the glass from falling into the gaps.

After looking at the plans 1000+ times - I ended up removing the foam on the sides of the piano hinge.

I then measured and marked the center line and F.S. (fuselage station) position - just enough so as to clear the piano hinge's hoops.

Using the vibrating multi-tool, I cut the fiberglass and taped it onto the speed brake to test its location (I placed the hinge on the OUTSIDE just to make sure I had the proper F.S. location.. it will go on the INSIDE when it is permanently bonded in place).

I then slid the entire assembly as far forward as I could until the hoops came in contact with the LB23 section.

I then made sure that I had removed enough foam around the perimeter and that no edges were touching - especially the aft lip of the speed brake. Looks good from here!

With all clearances checked and double checked... it was time to bond the piano hinge and LB19 onto the speed brake. I taped off the hinge so that no epoxy would go inside or between the hoops.

Applying 5-minute epoxy...

Clamping down on the hinge - I used a scrap piece of wood to increase the clamping force. I made sure everything was properly aligned and centered with the marks I had previously made.

I waited 10 minutes (just to be safe) and proceeded to bond LB19 in place.

I then placed a roll of tape (to act as a puck) and a heavy tool box over LB19 to force everything down in place while it cured...

10 minutes later... it was all set and finally ready to be glassed!

I know the norm is to use micro to fill voids and around the edges to make a nice transition... but I used flox here instead. Notice how I used liberal amounts of it - especially where all the transition edges are - where LB19 meets the foam, LB19 meets the hinge, where the hinge steps down to the glass, etc.

And all around the perimeter...

I then used a brush to paint on plain epoxy all around the perimeter where the new wet glass was going to bond with the dried glass below. I also painted the top surface of LB19 with plain epoxy to assure a good bubble-free bond.

And of course - slurry all over the foam surface area... she was now ready for the first ply of BID.

Layer number 1 of 3... all BID at 45 degree bias....

All three plies wetted out!

I used scissors to cut the fiberglass on the sides of the piano hinge - this was so I could insert a scrap piece of plywood to hold the glass up and allow for it to cure without disrupting the transitions around this area.

Here is another look...

I then let it rest for 2 hours and came back to knife trim this tab out.. I simply used an exacto knife and ran it across the line just forward of the piano hinge hoops. I hope the tape kept the epoxy out!

I then let everything cure overnight. The next day, I made sure I had no air bubbles... and it came out great! The flox did an excellent job at transitioning everything. Next step will be to test fit everything and trim the speed brake to its final shape!

1 comment:

Unknown said...


Really enjoy reading all of this wonderful information! I'm preparing for my own Long-EZ build and your site has been invaluable.

I also follow a guy that builds guitars. When he needs to temporarily hold something in place he'll put down a piece of tape, use superglue on the top of it and adhere that to another piece of tape on the part that needs to be held. Do you see that working well in place of the 5 minute epoxy assuming you use foam safe CA?

Here's a video that explains the technique better than I can.