9.4.3 Upper Strake Half Installation

It was relatively easy to get the height of the bulkheads to within spec. However, the internal fuel tank baffles are another story. Because the bulkheads block the view of the baffles, you build them as close as you can based on the provided templates along with a lot of test fittings of the upper strake to make sure they arent too high! The installation process takes that into consideration. They have you mound up the Jeffco epoxy so that it squishes down when the top is put on. I wanted to get an idea of how much I’d need for each top piece, so I used some plumbers putty. I placed the putty on top at various locations, then put the strake top on to see how much each piece squished down. That gave me a good idea for how much Jeffco I’d need to place at each location.

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I'm using the putty to determine how much Jeffco epoxy I need to mound up on the tops of the bulkheads and baffles for sealing the tank.

You can see the results of my experiment below.

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Closeup shot of the now squished down putty.

Because the Jeffco cures so quickly, I did not have time to take photos of the mounded up epoxy at each location. Apprently the process worked, at least at the bulkhead locations since I could see squished out epoxy there. Yay!

The photo below shows the first strake top installed. Since we live in the mountains we have plenty of “free” weights available in the form of rocks to hold everything down. I used gaffers and duct tape on the leading edge to hold it into place during the cure.

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The first strake top installed! There's no lack of rock "weights" available here in the mountains so I'm using those rocks to weigh down the top while the epoxy cures. The tape is used to hold down the leading edge.

The wing and strake in the photo above lined up decently at the leading edge junction. However, due to a problem with the construction of the left wing (I was still learning, specifically that the instructions don’t always perfectly match what needs to be done now!) I knew that I’d have a mismatch here so it was finally time to fix that problem.

Luckily I saved all of the old foam core billets and in this case, that came in really handy since I used the billet for the right wing to fix the gap. The original billet is a huge, rectangular piece of foam. I did some pre-trimming on it before temporarily attaching it to the wing. 

Wings - Strake - Leading Edge Repair

Using some old foam to fix the gap between the inboard edge of the wing and the strake.

After sanding all of the Velocipoxy “finish” off of the area to be comvered by the foam, I epoxied the piece of foam to the wing using a new batch of Velocipoxy. After letting it cure overnight, I started to do the finish sanding.

Wings - Strake - Leading Edge Repair 1

Getting closer - a lot of carving and sanding to get to this point!

The leading edge needs to match the rest of the wing, and I need to get the curves and all as close to the original profile as possible. You can see the end result in the photo below. That piece of foam is actually quite thin up until the inboard edge of the wing where it thickens up to match the strake.

The duct tape on the strake is there to help release any fiberglass and epoxy that accidentally spills over. I’ll clean all of that up later when the wings come back off in preparation for the “big flip”.

Wings - Strake - Leading Edge Repair 2

The foam is now epoxied into place in preparation for the triax layup.

I precut a piece of Triax to the proper size and with all of the angles and such to get as close a fit as possible. You can see the end result below. I used standard EZ-Poxy to attach the fiberglass to the foam after first applying EZ-Poxy and Micro to the foam as a pre-coat. I still need to apply a finish coat of Velocipoxy over this, but at this point, the repair is complete!

Wings - Strake - Leading Edge Repair 3

The layup is complete - the gap is gone, and I now have a nice, smooth inboard leading edge once again!

Once the fuselage is flipped, it’s time to do the strake reinforcement layups. In the photo below, you can see the Jeffco epoxy that squeezed out of the joint between the top strake half and the fuel bulkhead. That’s good - it means we have a nice, tight seal. Nevertheless, I have to grind all of that down so that I can finished the reinforcing layups that lock the strake to the bulkhead.

Fuselage - Strake - Inside Layups

This is what one of the joints between top strake half and the fuel bulkhead looked like before grinding out the excess epoxy.

Looking at the photo above, you can see how deep it is inside of the strake. My arms aren’t long enought to reach to the back so I had to make some extensions for my two tools used to grind down that epoxy. A couple of 2-1/2 foot long 1x2’s and some tie wraps took care of the problem. I made sure to wear my respirator and eye protection because grinding this stuff down was messy! 

Fuselage - Strake - Inside Layups 1

My arms aren't long enough to reach all the way back into the strake, so I needed to make some extensions for the tools I used to grind down that epoxy.

The grinding is finished. The next step is to add the layup. It’s 2 layers of BID but first, I have to fill in the gaps with a special mixture of Jeffco, Micro and flox. Again, since I can’t reach in far enough, the manual recommends using a long pole with a nail or screw on the end. After wetting the fiberglass on a long sheet of plastic, one end of the plastic gets poked through the nail or screw. The pole is then used to guide the fiberglass into place and since it’s already attached to the plastic, can then be used to carefully remove the plastic from the fiberglass. I attached a brush to the other end of the pole that I used to help pat the fiberglass into place. I actually was not looking forward to this job, but in the end, it wasn’t too hard to do.

Fuselage - Strake - Inside Layups 2

You can see how deep these are. In the end I was able to grind all of the excess epoxy down so that I could get a smooth layup over the joint.

Even though I didn’t talk about it, I needed to add strengthening layups between the main spar and the strake half. You can sort of see that in the photo below. I used the same process for that layup, except in this case, the usual EZ-poxy and BID was used. You can also see the finished layup on the right side in the photo below. 

Fuselage - Strake - Inside Layups 3

It's dark in there and the camera didn't want to focus, but you can still see the final layup over the joint. In the end, it came out better than I expected.

There are two baffles that need to be installed after the strakes are closed up. The reason for that is due to what you see in the two photos above. All of those long seams need to be sealed up before these can be installed. To say installing these is a pain is an understatement. Layups need to be applied to each side of the baffle. The side you see in the photo below is relatively easy (even though it’s a long reach) but the inside layups are a whole ‘nuther story! You’ve got to do it by feel. I’ll admit that they most likely aren’t very pretty, but then again, no one will ever see them so does it really matter? As long as the baffles have the support that they need is good enough. Apparently some builders don’t even seal the inside. Others try to make a seal before putting in the baffle, but that’s just as much of a pain, so it is what it is! I yanked on these good to make sure they were tight and they are. In the photo below some peel ply is still attached to the upper layer of fiberglass.

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Baffle #5 is now installed!

This baffle is closer to the open end of the strake, but it’s really not any easier to apply the fiberglass on the inside. This baffle still needs a couple of layers of Triax on both the top and bottom to really lock everything into place.

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Baffle #8 is now installed!

This is the #8 baffle on the other side. The final step is to run a double layer of Triax fiberglass along the bottom and top seam to fully strengthen everything. I’ve done that on the “top” side (which is the bottom in the photo below because the fuselage is currently upside down). I’ll do the “bottom” when the airplane is back rightside up.

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Completed baffle #8.

Although this next part isn’t really a part of this section of the manual, I’ll put it here anyway since it does involve the strakes. Finishing work! Yeah, back to sanding and filling and sanding and filling and sanding and filling! The first step is to smooth out the seam where the two strake halves meet, sand out the factory “finish” coat, then apply a 2-BID layer of fiberglass. The photo below shows one of the strakes prepped for the fiberglass. Since I had a lot left, I decided to use Jeffco here instead of the regular epoxy. While it’s harder to work with, I hope that it’ll do an excellent job of sealing any possible pinholes in that seam.

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I've sanded the bottom of the strake (remember, the airplane is upside down) in preparation for a 2-BID layup to finish off the seam.

The BID is now applied and waiting to cure. Once this sets up I need to start working on filling and smoothing all of this out with the regular old Velocipoxy + Microballoon mixture. More to come on that later!

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The layup is complete. Peel ply is still attached.

ui© John Trautschold 2018