Fuel tank senders

This weekend I made good progress on finishing up my second flap as well as starting the final assemble on the first tank. The flap went well as I figured out the optimal bucking situation from the first flap. Also, the pro-sealing of the Trailing Edge went much smoother/quicker/cleaner than the first one.

 

With the flap clecoed to the table while the pro-seal dries I started the final assembly on the first tank. I squeezed the end rib wet, but started the other method where you let the sealant cure while the clecos are holding pressure and then shoot wet rivets after a couple of days of curing. I have gone back and forth on the pros/cons of shooting wet rivets vs letting the sealant cure and what finally did me in was while I was placing the first full rib I really did not want to be rushing to shoot rivets. My take is that I increase the risk of shooting bad rivets when I am in a hurry, so I am going to go with the Rick6a Method (at least for this tank). About the only thing that made sense to me against this approach was someones comment on the forum about how the clecos would not provide enough tension in this method and there would be too much pro-seal stuck between the rib and the skin. When you let it cure like that and come back to shoot rivets over cured sealant that the compression of cured sealant leaves a weaker mechanical connection between the rib and the skin due to the compressible material between the two. My intuition is that is a valid statement. My intuition also says that bad rivets due to rushing also make a poor mechanical connection. So cured sealant and wet rivets it is.

After 3 ribs I ran out of clecos. (I still have the flap in the jig, so I guess I am going to need to wait until I finish that up this week before I continue on the tank.) 

Since I was waiting for sealant to dry I thought it would be a good time to start taking care of the fuel senders. I am going to go with the standard float sensors for this build. I really don't trust fuel senders all that much anyways, so I might as well stick with the standard ones. I am not sure why I do this to myself, but I always seem to start with the right side of the plane even when the plans call out the left assemblies. In doing that, I guess I am more careful to read, re-read, and re-read the plans because I am always double checking left vs right. Also, it is always nice to put together the second assembly per the plans and have no incorrect part numbers.

In the case of fuel senders, this cannot be more true. I started with the right float arm bending. I remember reading someones post about the right float arm needing a couple of more bends than the left in order to clear one of the tank stiffeners.  I mocked up the float arm in some TIG wire so I did not screw up the real arm.

Now I am normally pretty good with building up pictures in my head, but I will say, when I started making bends for the right float arm I got really lost. What it came down to was the senders themselves. Per the diagram and the plans the LH side gets the 385B-F and the RH side gets the 385C-F.

That is fine and dandy, but for some reason I would have guessed that if there was a left and right sender that they would be symmetrical inverses of each other. If you look carefully at the sequence of photos below you will see that the operation of both senders are identical to each other. Also, I am a little ashamed of these photos considering I do own a real multi-meter (Fluke). Weird. I would have thought one would have been backwards from the other for some reason.

So what is the deal? I am a little saddened that it took me a good 20 minutes to figure it out. It wasn't until I tried screwing the 385C-F into the right rib before I figured out what was going on. If you look at the left photo, you will see that the hole pattern on the flanges are 180 degrees out from each other. That is beginning to make sense now.

I had to dig into the wonderful inter-tubes in order to verify what I was seeing. The Je-Mo build log had a great write-up on this. The following images are from his site:

Left tank (the sender orientation identical to the build plans)

Right tank. If you look carefully here, the float arm comes in from the forward side of the tank opposed to the left tank where the float arm comes in from the aft side of the tank. 

Being able to enjoy flying with your family and friends is one of the greatest things ever!

N Numbers

I spent tonight priming the interior structure of the left flap. While waiting for the primer to dry I got a couple of other things done:

• I have been in email contact with South Florida Sport Aviation and I am seriously debating purchasing their front seat covers, rear seats, overhead console, and headliner
• I got my list of question together to talk to Rhonda at Barrett Precision Engines tomorrow
• I started designing my matco parking brake valve bracket
• I started designing my wingtip landing lights
• I reserved our N number! 5412K for 05/04/12 (Our daughters Birthday) K for our last name. Also I like how one-two-kilo sounds. I can't wait to make that radio call. The process was pretty painless. I thought I had to mail in a written letter, but there is a website that you can both check if a number is available as well as pay your $10 dollars to reserve an available number. Done!

Landing Lights

I probably have already written this, but one of the reasons of why I wanted to build my own plane was the intimate knowledge that I am have going to have about this plane. I hope to never have any in flight problems, but being able to visualize how a fuel molecule travels through every line and fitting in transit from the tank to the cylinder makes me more comfortable.

The second reason I went with building my own is the ability to setup the plane exactly how I want it. Per the name, this is an experimental plane. Yeah yeah, for all of you true experimental builders, this is really just a kit plane. Even though this is a kit plane, there are many things that the builder can experiment with. More so that I think I was actually prepared for before starting this project. There are the obvious things like avionics and panel configurations, propellor, seat materials, paint colors, etc. Beyond that, there are so many other things. Door handles, door pins, consoles, wheels, brakes, ignition, fuel system, etc. 

I have been looking at all of these things lately and I needed to narrow down my work to a manageable number of simultaneous projects. I am going to start planning the position and landing lighting.

When I picked this kit up it came with a Duckworks Leading Edge landing light kit. Thankfully the wing had not been cut yet. I am not afraid to cut the leading edge, but quite honestly I don't like the look of the leading edge landing light on the RVs. To me, the way the lenses end up always look, well, experimental. I would really like to get my landing light into my wingtip. I could probably just pickup some ZipTips, but I would really like to do it myself. 

I have seen a lot of adaptations of Baja Designs Pro Squadrons into the wings and wingtips. I have a special place in my heart for Baja Designs products because I have run many thousands of miles off-road behind Baja Designs lights. How cool would it be to get them into my plane!

The second thing that bothers me about wingtip lighting is most of it looks like boat designs from the 1970s. I am a computer engineer and I like raw circuit boards. The Cirrus position lights and the ability to see their raw LEDs really does it for me. I think it would be a nice touch to have a similarly designed wingtip setup.

I started down the path the other day of drawing up my own boards in Eagle, but then I came across FlyLeds.com. FlyLeds has a product line pretty close to what I was starting to design, so there is no reason not to go with them right now. They have two things that I really like. 1) They have skinny boards that area designed to work in conjunction with a landing light. 2) They give you the option to build your own boards!

The standard MR-16s that Vans sells for their wingtips sound fairly useless if you are actually making night landings. They draw a lot of current, they get hot, and they don't put out much light (relative to an actual landing light). Going back to the Baja Designs idea, it would be super cool to get some Squadron Pros in the wingtips for the landing light, and use the side FlyLED boards for anti-collision and position lighting. 

While digging through the BajaDesigns website to order a Squadron for experimenting I found out that they have a S2 version of their light:

 

The S2 is still pretty bad ass. It outputs 2450 Lumens, draws 1.66A, and only weighs 8 ounces. Did I mention it was Baja Designs and that Baja Designs is a bad ass company?

Now I have to do some work in CAD to see what I can all fit into that poor wingtip. From the looks of it, I think there is a fair chance to get the S2 in either a horizontal or vertical orientation into the tip alongside the skinny FlyLEDs board. (I don't actually know that I am just going off of someones previous photo of a Squadron Pro inside a wingtip)

I will obviously have make some brackets and probably cut away some of the existing bracketry, but this looks promising. Here are the S2 Pro dimensions:

The cool thing about this approach is that if I put lights in both of the wingtips I should be able to select and position the beams to provide both great taxi as well as landing lights. The S2 has many lens options:

I drew this up in Solidworks to get a rough proof of concept in terms of size and fitment. I don't have the exact parabola of the wingtip modeled correctly (I was lazy), but for a rough size this is pretty close. The FlyLEDs "skinny" board is supposed to be 1 inch wide. The wingtip gives me enough room to put a plate that is 6 inches tall at the tallest point and 4.5 inches wide. I haven't measured it but I think the curvature of the wingtip is a little more slim than I modeled. However, with these rough dimensions it appears that the S2 will fit into the wingtip plate in both the horizontal and vertical orientations. That would give me forward facing strobes from the FlyLeds board, a "racer" series landing light that would give great distance, and a shorter wider beam illuminating the nearby taxi and runway. That is the theory at least.

With the sizing looking like its going to work I think it is time to order some components to see if the theory will hold up. Worst case I have some small LED lights for my wife's jeep.

-To be continued-