March 2002

3/28/2002: I did the needed work to grind out the bubbles that had such a problem with on 3/24. I tried several different bits in the Dremel to see which seemed to perform best for this purpose. Some ground the fiberglass too slowly, which were taking too long. Others where too fast, and easily took more than intended. The best ones were the Dremel #107 Engraving Cutter for the smaller bubbles, and the Dremel #100 High-Speed Cutter bits for the larger ones.

As I started grinding, a layer of dust obscured the area I was working on almost immediately. I found that I could progress more quickly if I used an Ultra Fine Point Sharpie marker to outline the outer perimeter of each air bubble. It was much easier to see the black marker line through the dust than the actual bounds of the bubbles. Then I would grind until I had ground out the material inside of the marks, and then ground away the marks as well.

Although this was not difficult work, it did consume time that could have otherwise been used to make new progress. From now on, I will go to greater lengths to avoid bubbles in the first place. When I seal the wing attach bracket bolt holes in the left wing, I will make a very minor change in the way I put the 2 BID in place. Before I put the 1/4 foam sheet in place in the wing, I will bond a 2 BID layer on the foam on my fiberglass workbench. I will let the 2 BID cure just enough to where it barely beyond the tacky phase. Then I will trim the 2 BID along the perimeter of the foam sheet with a razor blade. I will also trim the 2 BID that covers the bolt holes that will be already cut through the foam. Then, while the 2 BID is still in the "green" curing stage, I will follow the manual instructions for bonding the foam in place, filling in the bolt holes, and creating the fillet along the perimeter. Finally I will use 2 inch 2 BID strips to cover the perimeter of the foam sheet in using the type of procedures described in Chapter 7, Section B, Page 18 for glassing in the wing ribs. This should make it considerably easier to avoid bubbles.

3/24/2002: This weekend I worked on sealing the wing attach bracket bolt holes as described in Chapter 7, Section C of the Lancair ES construction manual. The picture below shows a 1/4 inch thick sheet of foam that has been placed on the front shear web at the front of the wing fuel tank. The holes in the foam fit around the bolt heads that hold the wing attach bracket to the shear web on the opposite side. You can also see the holes in the shear web that the bolts fit through. The purpose of Chapter 7, Section C is to bond the sheet of foam into place, fill in the gaps around the bolt heads with epoxy/flox filler, fill the gap around the perimeter of the foam sheet with epoxy/micro to make a fillet, and cover the entire foam sheet with 2 BID fiberglass so that the fiberglass overlaps all 4 perpendicular surfaces around the foam perimeter by at least 1 inch. This will seal the whole fuel tank shear web wall so that fuel does not leak out of the tank through the bolt holes. It may sound complicated, but it is a fairly small and simple task. Despite, the fact that this a a small and simple task, there is still room for error.

Step C10 states that you should "Cover the urethane foam with 2 BID extending 1" onto the wing skin, shear web, and ribs. This is a potential leak area, so make sure there are no gaps.". This can be done with one 2 BID piece for the whole task, which is what I did in my right wing. Anticipating problems in the corners, I removed 1 square inch from all 4 corners. This would make it easier to accommodate the 90 degree bend along all four sides without having each side interfere with the two adjacent sides at the corners. Although I did anticipate that issue,I did not anticipate the fact that the fiberglass cloth would stretch by about 1/2" to 3/4". This reduced the benefit of the 1 square inch I removed from each of the 4 corners. Also, I did not expect that as I worked air bubbles trapped underneath the 2 BID toward one side of the glass cloth, I would be pulling the glass fabric tighter and induce bubbles at the opposite side. As a result, I found myself going back and forth re-removing bubbles I had previously eliminated. I felt that I was making the kind of progress that a dog makes while chasing it's own tale.

Air bubbles trapped under layers of fiberglass in an aircraft are unacceptable. Although this part does not provide structural strength, it is important that the seal never develop cracks which would allow fuel to leak from the fuel tanks. Also, this area will not be accessible once the wing is closed. Therefore, inspection or repair will not be possible. So, it really is critical that the air bubbles are removed now. This means that I need to use a Dremel to grind out the fiberglass over the bubbles, prepare the area for a good secondary bond, then fill the holes or depressions with epoxy/micro, and then put a 2 BID layer over the repaired areas. So, I have some reworking to do.

3/22/2002: Carstin Sundin from Lancair posted information in the Lancair Mail List regarding Lancair's Response regarding their position on recommended surface preparation techniques for secondary bonding.

3/18/02: This evening I finished mounting the left wing attach bracket. I continued to have problems with bolts #5 & 6. I backed those bolts back out and devoted some time to trying to figure out exactly what the problem was. I concluded that the holes in the shear web and the attach bracket are drilled with tight enough tolerance that if the attach bracket holes were not perfectly aligned with the shear web holes, the bolts would be very difficult to put through both holes. This explained why the real resistance that I encountered started as the bolts entered the wing attach bracket hole. With a few light taps with a rubber mallet, I was able to adjust the bracket by an un-perceptible amount, but it was enough to turn this impossible task into a doable task.

When I do this for the right wing, I will do it somewhat differently based on what I found during my troubleshooting. The AN6 bolts that are used inside the wing are 3/8 diameter bolts. I will push longer non-AN 3/8 bolts through all of the holes with the bracket in place. These bolts will help make sure the bracket is aligned correctly before I start working with AN bolts. Once I have those bolts in place, I will replace each bolt one at a time with the correct AN6 bolt. Then I will place the AN5 bolts on the outside of the inboard rib. From there I can put the washers and nylock nuts in place, and go through the appropriate torque procedures.

I also torqued all 11 bolts to specs (100 - 140 inch-lbs. for AN5 bolts, and 160-190 inch-lbs for AN6 bolts). I also marked all of the bolts and nylock nuts "flight ready" with red nail polish.

3/17/02: Today I was able to work some more on the wing tie down bracket for the left wing. I am now ready to permanently bond it into place with Hysol 9339 adhesive. I am very pleased with how the spacer pad I built up with an epoxy/flox mixture holds the bracket in just the right angel to make the outer threaded hole sit flush with the outer wing skin.

When the time comes to close the wing, one of the concerns that I would have had was to avoid getting epoxy resin inside the threaded hole for the wing tie down brackets. If epoxy resin gets inside the hole, and it is not cleaned out before the resin cures, I would not be able to insert the wing tie down loop. Given a builder's trick I learned from Jim Nordin, I will be able to easily avoid this problem by melting paraffin wax and pouring it into the first 1/4 inch of the hole. The wax will protect the hole, and will then be easy to remove when the wing closure is complete.

I also worked on mounting the wing attach bracket for the left wing. There are 11 AN bolts that hold the bracket in place in the forward shear web. These bolts are inserted into pre-drilled holes. They also pass through existing holes in the wing attach bracket. The holes are drilled such that the bolts fit very tightly. They are tight enough that they cannot be pushed all the way trough with finger pressure. With most of the bolts, I at least had to push them through with a scrap block of wood. With some, I even had to use a plastic mallet with the block of wood to drive them through. Bolts # 5 & 6 are difficult enough that I have not gotten them pushed all the way in yet. Although it is very tempting to use a rattail file to make the holes slightly larger, I know that the tight fit is critical. If the holes are filed larger to the point that the bolts are able to move at all, the holes could become elongated with time. This would let the bolts move more, which would cause the holes to become even more elongated. With time, either the shear web might fail from the increasing stress, or more likely, the bolts could be sheared off, and the wing could separate in flight. So... the holes are tight by design. I need to keep them as tight as possible.

3/3/02: We had a cold-front blow through Houston. In my opinion, it is too cold to work in the garage on the project. There have been many days in the last few months that were too cold to do anything with epoxy resin, but this cold front makes it too uncomfortable to work on the other tasks too. I had hoped that it would not be necessary to insulate the garage for the winter here in Houston. I was sadly mistaken. I did realize that it would be essential to insulate inside the roof for the summer. Lesson Learned: No matter where you live, chances are it is going to get hot and/or cold enough to insulate your workshop. If you don't, there WILL be days where you won't be able to work on the project. This leaves a problem I have not been able to resolve yet. Maintaining temperature within a desired range, and maintaining good ventilation when mixing resins seem to be mutual opposing goals. I have not come up with a good solution that addresses both at the same time. I would love to hear suggestions that other builders may have come up with.

I am taking this opportunity to work on the website. I have switched web development software (from NetObject Fusion MX to Macromedia Deamweaver 4). Given differences in the way the two programs work, I have made major changes in how the website is built "under the hood". I am sharing this technical detail because any Bookmarks or Favorites saved for specific pages within this website are now broken (guaranteed). One of the drawbacks of using high-level web development tools such as these are that the resulting HTML code that describes what each web page should look like can be very inefficient. This was the case with the HTML code that NetObjects Fusion MX generated. Dreamweaver has helped me cut most of the extra code in each page throughout the website. Therefore, some people may find that some of the larger pages in this website download and display slightly quicker. The most probable candidates for experiencing perceptible benefits are those that have slower modem dial-up connections to the Internet, and/or those that have older slower computers. All others will not likely perceive a difference.

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