Feb 26
2010

Hours
Logged: .5

I have been looking for some good material to use as a floor covering. Bob uses bare aluminum, and that method certainly has some merits. It is light, simple, and durable. Tabitha would rather have something that looks a bit more finished, but also something that dampens vibration a little bit better. She says that prolonged exposure of her feet to a vibrating structure like the floor will accelerate the development of arthritis and contribute to an overall mood of malaise and discontent.

I don’t really want to use something like carpet, because I know that it is going to be harder to clean than a solid surface. I don’t want to have to worry about getting into the airplane with slightly dirty shoes. I’d really like to find the airplane equivalent of linoleum, and there is a great example of it on the floor of our planes at work. It is thin, easy to clean, and super durable. It gets the foot traffic of lots of people, every other hour or so, every day, all day, and lasts years under those conditions. I asked a few of the mechanics about where it comes from, but they don’t know. Even if I could find who makes it, chances are good that it would not be available in the small quanitity and price that I would like to have.

A similar product is available for household floors, but it is 1/8″ thick and extremely heavy (pounds per square foot).

One of the email list members suggested that I try products intended for boat floors. This was a good lead, and soon I found Nautolux Decco Dot flooring. It has all of the good qualities that I like, and it is very light weight. I think that the entire floor would be under 5 pounds, perhaps even less. The bad news about the Nautolux is that it is a little bit too thin, such that it needs to be glued down to stay flat. It also doesn’t have much in the way of vibration dampening. I ordered a sample piece to try some burn testing on.

The whole idea of burn testing is a little bit silly in some ways. At first it seems like a really good idea to make sure that the interior materials have good qualities with regard to flamability. The unfortunate reality is that since the rest of the interior is made of aircraft fabric, the huge wall sections are certainly the weakest link. Having said that, I’m planning to burn a small piece of each proposed interior material, just to see if it is at least acceptable. Burn tests aren’t legally required for experimental airplanes of course.

Since the Nautolux is so thin, I figured that I could try to find some 1/8″ closed cell foam to use between it and the floor. This would help dampen vibration and noise, and also not add too much weight.

Decco Dot Sample Piece

I took the above piece and stuck it in the propane heater for an unscientific test. It started to burn, and when I took it away from the heater, the flame died down. That’s convincing enough for me, since it didn’t continue to burn brighter.



Thanks for Visiting! • This Entry is from February 26, 2010 at 11:00 am 


Feb 21
2010

Hours
Logged: 2

Today I was able to get away for a few minutes to finish prepping the seat frames for paint and apply a coat of epoxy primer. Today was one of the first days that we’ve had lately with a warm enough temperature.

Spray Gun

Chinese Spray Gun

This was my first time to use the little Chinese paint gun that I picked up a while back. I didn’t know how it was going to work, so I did some practice painting with some alcohol that I had on hand- simply because it was cheap and not water.

Headrest frames ready to prime

Colorful Polyfiber cans and colorful paint gun box

It was good to get a feel for how each of the different knobs changed the spray charactaristics. Since I was painting tubes, I adjusted the fan pattern to the narrowest setting.

Practicing with the paint gun- note the intentional run on the upper left.

I followed the directions on the can for mixing the polyfiber primer and poured it into the cup. For practice I painted a section of the side of the clubhouse. I wanted to see how much spray it would take to make the paint run, so you can see a couple of nasty spots. Feeling well prepared enough, I started spraying the seats. The most difficult but yet most important thing to remember was to keep the gun far enough away from the work- about a foot or so. When I started to get distracted I would find myself holding the gun way too close and getting too much paint on.

Here's the back seat frame after priming and headset modifications.

Bearhawk Front Seat Backs

Bearhawk front seat backs after priming

Bearhawk Headrest Modification

Here are the Headset Frames after priming

While I had the primer out, I also primed the elevator trim pushrods.

In the end I was quite satisfied with the finished product. Using the spray gun was easier than using a rattle can, mostly because of the “air only” trigger setting. I could keep the air flowing all the time, and then just spray the paint when necessary.

I cleaned the gun with some reducer, and then left to go to work.



Thanks for Visiting! • This Entry is from February 21, 2010 at 1:01 pm 


Feb 16
2010

Hours
Logged: 3.5

My plan was to use my cheap little sand blaster to prep the seat frames, but it didn’t work so well. The sand blaster needs some attention, but I was able to use it to clean most of the weld beads. Since the rest of the areas were flat and mostly straight, I used the scotchbrite wheel in the angle die grinder to clean them. The whole process took a while, but now the seat frames are ready to paint.

Clean Seat Frame

The steel really shines up nice with the burned paint and mill scale removed.

Close-up

In this close-up view you can see the sandblasted area vs the scotchbrite area.





Thanks for Visiting! • This Entry is from February 16, 2010 at 4:00 pm 


Feb 15
2010

Hours
Logged: .5

Since my toy brake only bends pieces up to 18″ wide, I had to find another way to bend the longer rudder cable guards. They are 25″ and 29″. Brad was nice enough to let me use the brake at his shop. It was a combination roll/shear/brake from Northern tool, and the dies were really sharp. I used Bob’s tip from the ancient Beartracks to make a protective shoe. I ran over to lowes and picked up a roll of flashing, then used the shear to cut strips that were wider than 30″ and about 3″ across. I bent those in the brake, then sandwiched the good aluminum parts between. The flashing was thin, so I ended up using about 6 pieces above and 2 below in order to get a radius that was acceptable for the 2024T3 guards.



Thanks for Visiting! • This Entry is from February 15, 2010 at 12:41 pm 


Feb 6
2010

Hours
Logged: 3

Today I drilled the top mounting holes for the right wingtip and clecoed everything in place. I’m still going to have to do some work on the gap between the fiberglass and aluminum to try and get something that is rain tight. I walked over to Danny’s hangar to see how Vans solves the problem, and I really like their solution. His RV-7 has the outboard wing rib mounted about 1.5 inches inboard of the end of the skin, which allows that the fiberglass part fits under the wing skin. In this case, there are no waves at the fasteners because the wing skin spreads the load like a giant washer. Since the skin is only .025″ thick, from arms length it looks flush. If the inboard edge of the fiberglass isn’t perfectly straight, it doesn’t show, since it is under the aluminum. This would be a cool feature to incorporate for a scratch builder, but I can’t see how it would be practical to do this late in the game. Here are some pictures of the vans setup:

Vans Wingtip

Note that the fiberglass is under the wing skin

Wider Angle - From here there are no waves, and it looks flush because the wing skin is so thin.

At the Aileron it switches to fiberglass on top.



While I had the wingtip mounted, I wanted to see how hard it was going to be to remove the ridge that the wingtip had as a result of the mold. The fiberglass is pretty thick in that section, and I was able to file the ridge flush without getting through the white coat in all but just a few spots. With some filler and wet sanding, this tip will look great.

This is the ridge left during the manufacturing of the wingtip. The file takes it right off.

Here I am filing off the ridge, not straying too far from the propane heater.




Now I get to do it all again. I’m glad this isn’t a biplane!



Thanks for Visiting! • This Entry is from February 6, 2010 at 4:15 pm 


Feb 5
2010

Hours
Logged: 4

I wanted a break from the wingtips today so I started working on some guards for the rudder cables. Since the cables run along the inside of the cabin, I wanted to protect them from passengers who are children, passengers who act like children, and shifting cargo. I also plan to use the guards to hold down the floor covering, once I finally find the covering that I’m looking for.

It's Cold! Here I am cutting some 4" blanks for the guards, not getting too far from my best friend the heater.

I started out by cutting some strips of .025″ 2024-T3 off of the 48″ stock. It sure would be nice to have a 52 inch wide combination brake, roller, and shear. Or, at least a shear! I cut them out with the snips, then deburred, rounded the corners, and polished the edges. I started with 3 strips, since I needed 4 total pieces at 30 inches x2 and 24 inches x2. The two bonus 18 inch pieces came in handy for the front 9″ panels and for test strips.

Rudder Cable Guard Strips

A Skinny Test Piece for Shape Idea #1

This was the first idea that I had. I had planned to drill holes in the top and thus be able to mount the guards with the same screws that held down the floorboard. I liked that concept, but this guard wasn’t very aesthetically elegant, nor was it very rigid. The best looking examples that I had seen used angled pieces, so I tried a few more samples.

Let's try some other shapes...

Here they are in place, just visualize the vertical panel. This picture is looking down at the white floorboards.

Here are a few eligible configurations.

After seeing all of these in place, the only realistic choice is the one with two 135 degree bends. I’ll just end up putting a couple of extra nutplates in the floorboards, and that will be well worth the result. Now, to finalize the specifics…

This one looks too close to the cable. My goal is now to make one that has as much clearance as the OD of the fairlead, just to provide some extra margin.

I know it’s kind of arbitrary to make the guard clear the fairlead, but since the OD of the fairlead tube is 7/8″, that gives the rudder cable more room to work without bringing the guard way out into the interior.

There's no need for the shape not to be symetrical. I'm glad I was trying this with little test strips!

I experimented with a few different lengths. It was sort of like goldilocks and the three bears. Perhaps I should call this story alumilocks and the one bearhawk.

This one's too long, see how there is a large gap between the guard and the fairlead?

The straight stretch is too short on this one. It needs a longer hypotenuse.

This looks better!

Here's the "just right." Note how it just clears the fairlead.

Here are the various test subjects. The best one has a 7/8″ flange on either side, leaving 2.25 inches in the middle.

Final Results: 7/8-2.25-7/8 (bottom) wins.

With good results from the test strip, I bent the first 9″ panel. Since my little toy brake can only handle short pieces, this was a logical choice.

Here's where this piece goes. It is protection from the right side passesnger's right foot.

I knew that I would have to do some trimming, in this case to clear the front seatbelt mount and the front seat track.

Here's a bent blank, ready to trim the top corner and make a hole for the seatbelt.

Here’s the test piece in place. Before I make the other side I guess I should put a front seat in and make sure that I don’t have any unforeseen problems.

Here's a view from the front looking aft

Bearhawk Rudder Cable Guard

Here's a top view of the rudder cable guard with the cutout for the front seatbelt.

Here's the front guard ready for testing

Here's a test fit to see if I got the radius correct. Not bad for the first try.

I had to stop there since I couldn’t bend the larger pieces. I’ve got some good leads on a bending brake that can handle the 30″ wide width.

Since I had a few extra minutes I figured I would make the support tube for the top of the fuselage. The stock Avipro fuselage has arrangements for a single shoulder harness attach for each front seat passenger. To use a dual shoulder strap (or a single y-shape) Bob recommends adding the tube from the rear spar carry through forward to the x cluster in the middle.

Here I am test-fitting the tube. Fish-mouthing with the grinder is not hard at all, and I've only done it a dozen times.

Bearhawk Shoulder Harness Support Tube

Support Tube for Shoulder Harnesses - the black one that's hard to see.

There’s not much to it. I can see why I keep hearing stories of people who buy a fancy tube notching contraption and then stop using it when they figure out how easy it is to fish-mouth with a grinder. While I was there I stood by my little heater and worked out how I’d like to incorporate the skylight. I think I’m going to reproduce the structure that happens under the fuselage at the trailing edge of the boot cowl (the trapezoid shape) over the top of the main spar carry-through. This will act as a rear support for the skylight. I’ll add extend the longitudinal tubes in the roof area near the trim wheel back to that point, and then add in another 3/8″ tube spanwise trapezoid somewhere up there where it starts to get curvy. I was glad to have some time to wrap my head around all of that and make a shopping list.



Thanks for Visiting! • This Entry is from February 5, 2010 at 7:45 pm 


Feb 4
2010

Hours
Logged: 4

I was able to get some good working time in today. The two areas of interest were the wingtip and the seats.

Back when I was at Bob’s this fall, I noticed that the fiberglass wingtips on his new Patrol LSA prototype were really smooth, with no waves between the rivets. I asked him how he did that, and he said that he put a protective piece of wood on the trailing edge (where the aileron would go) and used a ratchet strap to pull the wingtip tightly aft and down to the wing. Today since I was finished with the underlying AL support strip, I got out the ratchet strap and did some drilling.

Ratchet Strap on Wingtip

Here is the ratchet strap in place. I had to slide it left and right occasionally for drilling.

Hole Displacement

Here you can see the difference that the strap makes. The black hole on the fiberglass part used to correspond with the larger (center of 3) rivet hole. This picture is fairly close to the leading edge, and the strap is pulling towards the left side of the picture.

Hole displacement

Here you can see the old hole. Note how far the old hole is from the large rivet.

I’ll have to say that the ratchet strap did make a big difference, which was cumulative as I worked my way aft. There was probably a half-inch difference at the aft section. This is certainly better, but I’m still not all that pleased with the finished product. It still has some waviness.

Burned Hair

This is a picture of my burned hair, after reaching down to pick up something that was a little bit too close to the heater. Working on airplanes in the cold is a hazardous occupation!

Before I did any drilling, I wanted to make sure that the trailing edge of the wingtip was going to be parallel with the trailing edge of the rest of the wing. After all, if it was tilted, it would be acting like a miniature aileron all of the time. Since I’m trying for a flush mount, I had to trim the inboard side of the top of the wingtip so that the trailing edge would line up while the edges were flush with the skin.

Wingtip Alignment

Can you see how the trailing edge of the wingtip is now aligned with the trailing edge of the wing?

Trimming the Wingtip

In order to make that alignment possible with the flush mount, I had to trim about 3/16 of an inch off of one side.

Me trimming the wingtip

See, it is me doing the work.

After it started to get too cold to work in the hangar, I went back home to check on my chemistry project. I was wanting to weld some nuts onto the seat backs that would accept thumb screws. These thumb screws would hold the headrests in place, though for now the headrests are pretty snug as it is. I was worried about welding the zinc plated nuts and having zinc fumes, so I did some Googling. It turns out that zinc is very reactive and will dissolve in just about any acid. Steel also dissolves in most acids, which is a problem since the base metal of the nut is steel. Fortunately, phosphoric acid is one that will dissolve the zinc and leave the steel alone. This is handy, since I can drop the nuts into a jar and come back later without coming back to an empty jar. I left them in there for a few days, until they had mostly stopped bubbling.

Tapped Hole

I used a tap to cut threads into the tubes, so that I can use a screw to hold the nut in place during welding. These threads will also function in the final part.

First, I drilled and tapped the actual seat part. These threads were deep enough to hold a finger-tight screw in place, but certainly not deep enough for use in service. I threaded the nut onto the screw, put the screw into the seat hole, and lightly snugged the nut down tight to the seat part. This would help ensure that the threads would be lined up.

Nut Ready to Weld

The stainless screw is there to hold the nut in place and limit distortion. Note the dull luster of the nut after its acid dip.

I was reading the conversations on the Bearhawk email group about problems with welding nuts. Lots of folks were having problems with distortion of the threads during welding, so I took some of the advice of the more experienced welders to try and mitigate the distortion. For starters, I put a screw into the threads when I did the welding. Also, I tacked on four sides and tried to keep the puddle away from the middle of the nut as much as possible. Finally, I took the screw out as soon as I finished the weld, so that it wasn’t stuck there forever.

Nut Welded in Place

Here's the finished product, ready to blast and paint.


After the part cooled completely, I chased the threads one more time with the tap and everything was ready to paint.



Thanks for Visiting! • This Entry is from February 4, 2010 at 9:00 pm