Sunday, August 8, 2010

Culminations and Beginnings

It finally happened. I reached the inevitable culmination of the period of time that I will be able to build the RV-12 in my basement. I stretched it out as far as I could by doing the rudder pedals and fuel lines before section 23, but those are both done now. Section 23 is the beginning of a new phase of building, where of a necessity everything will be done in the hangar. It wasn't a completely painless transition; a lot of tools and partially completed pieces of airplane, along with the very long wing spars, had to be loaded up and moved. It turns out that the fuselage section will fit nicely in the back of a Toyota Tundra, but the wings spars not so much. The spars aren't heavy, but they're a pain to move because they're unwieldy and don't balance the way you think they will. There is definitely a heavy end.

A lot of rearranging and housecleaning (I've been in that hangar for a decade - stuff piles up) was required in the hangar to make room for everything and spiffy it up to make it a more pleasant environment. All in all, I think I spent two or three days getting fully situated.

I've also been dreading the beginning of section 23 because it starts with forming the longerons. A longeron is:

In aircraft construction, a longeron is a thin strip of wood, metal or carbon fiber, to which the skin of the aircraft is fastened. Longerons are attached to formers (also called frames), in the case of the fuselage, or ribs in the case of a wing, or empennage. In very early aircraft, a fabric covering was sewn to the longerons, and then stretched tight by painting it with dope, which would make the fabric shrink, and become stiff.

Longerons often carry larger loads than stringers and also help to transfer skin loads to internal structure. As stated above longerons nearly always attach to frames or ribs. But stringers often are not attached to anything but the skin, where they perform the duty of preventing the skin from deforming, which would create stress risers that would destroy the structural integrity of the monocoque. It is not uncommon to have a mixture of longerons and stringers in the same major structural component.

Sure, whatever. On an RV-12, there is one longeron per side, and it has to follow the curvature of the fuselage as it bends around the cockpit. It is fashioned from a straight piece of angle aluminum. Thousands of words have been written about the difficulties in fashioning longerons, so as I am the first in line to put off something I don't really want to do, I found a different way to occupy myself for a couple of days.

That story starts way back before I started building the RV-12. I needed a smaller project to test my mettle. Hours and hours went into deciding what to build, dozens of blog postings were written as I searched far and wide for a suitable project, and I eventually landed on the idea of building a kayak. I don't remember how long it took to build, but it was probably five or six months. It turned out pretty well, in my opinion.

It's great for paddling down the Big Darby, but I eventually got it in my head that I'd like to be able to go to other places. The Darby is close by and it was easy to have someone help load the boat onto the car, drop me off at the river, and pick me up downstream a few hours later. Going further away was more difficult in that I needed someone to go with me, but no one would want to sit around for a few hours while I was out paddling around. I solved that problem by buying another kayak. 

That worked out well, but I've recently had a relapse. I've always liked sailing, and having experienced the effort required to traverse a large reservoir paddling against the wind, I decided I'd rather have the wind as a friend rather than an enemy. I rekindled my interest in sailing. I managed to catch a healthy dose of 'want' for a sailboat. It's not exactly out of the blue; it's just been lying dormant for a few years. Meanwhile, neither kayak has seen the water this year. I decided to sell the kayaks and buy a sailboat. That was only a temporary decision, lasting only as long as it took for me to realize that I couldn't part with the boat that I had built. I set my sights a little lower and decided to sell just the guest kayak and see how much sailboat that I could buy with the proceeds. I thought it would be easy since I only want a simple boat that I can rig in just a few minutes and sail by myself.

And so it transpired that I sold the kayak Friday evening, and went to look at a potential sailboat on Saturday afternoon. The boat I went to look at is a Force 5. It's less that 14' long, can be rigged in just a few minutes, and can be sailed by a crew of me. The asking price was within budget too. What could go wrong?

Well, you know me. Plenty can go wrong! The seller had it all rigged and ready to go by the time I got to the reservoir. All we had to do was get the boat into the water. But rather than tow it up to the boat ramp to be launched, he suggested that we just carry it down to the water. I think that would have worked out okay except for one thing: there was a foot and a half step to go down. As we were bringing the boat down the step, he let it drop and there was a resounding 'CRACK" as the rudder split. 

I'll never forget what he said next. "Well, that was the product of a bad idea!"

The break in the rudder is nothing that can't be fixed, but there was also a little leakage around the tunnel the centerboard goes through. That too can be fixed with a little work, but I decided that I'm just not looking for a fixer-upper. I have longerons to bend, after all. He had another prospective buyer coming to look at it that might be more interested in doing the required repairs, so I just told him to go ahead with that deal. Meanwhile, I'm foraging around the house looking for other stuff to sell so I can afford a newer boat. I have my eye on this Zuma 13-footer up in Sandusky:

The seller hasn't gotten back to me with an answer to my question as to whether he has sold it yet or not, and I'm not in a terrific hurry anyway since my new trailer hitch for our Subaru still needs to be delivered and installed.

That leaves me with no options but to start on the longerons. As I mentioned, there have been thousands or words written about easier ways to do the longerons than the method provided in the build manual, but I want to at least try the Van's way first. The first step looked easy: measure and cut the provided angle aluminum to 82 3/8" (I think - I'm going from memory on that). Well, that really was easy. Tape measure, band saw.

The mathematicians in the crowd will have noticed that I put my mark at the 84 3/8" mark. I do that because I start my measurement at the other end at the two inch mark. It's more reliable that way because of the folding claw thingy on the other end of the tape measure.

The next step is so easy that one begins to wonder what all of the fuss was about. All you have to do is measure and mark some spots on the longeron that will be used as start and stop marks for certain bends and twists. One suspects that it is the bends and twists that cause all of the heartache. 

One suspects correctly.

In any event, I measured and marked.

Then we come to the innocuous direction, "Open the angle of the longeron an shown." What is shown is that I need to open the 90 degree angle to 95.4 degrees. Heh, only 5.4 degrees. A pittance. The method shown looks easy enough: just put the angle on the work bench with the open end down and whack it with a rubber mallet. Continue whacking until you have opened the angle a measly 5.4 degrees. What could be easier? I set my angle measuring doohickey to somewhere in the neighborhood of 95.4 degrees and put it on the angle to see how far I would have to whack.

Okay, then, start the whacking!

I pounded and pounded and pounded. Then I measured again.

This continued for half an hour. No progress whatsoever. I really wanted this to work, mostly because the PSTRV had stated unequivocally that this method works. Perhaps, I thought, the problem was that I was only using a 2 lb. hammer. Maybe I just needed more mass. More velocity would work too, but I was already giving it all I had. Nothing for it but a trip to Harbor Freight. Wearing that shirt. A trip that would be fraught with peril, what with me being dressed like a cabana boy. 

Harbor Freight had a 4 lb. mallet on sale, and no one even noticed my shirt. Somewhat rebuffed, I had to revert to calling attention to it myself. As I was at the checkout counter, I told the girl running the register that today was my lucky day because I had begun to despair that I would never be able to find a hammer that matched my shirt.

So it was back to whacking on the longeron, but this time I was able to double the force applied on each whack.

See what I mean about matching my shirt? What an amazingly gauche color for a hammer! (Looks good on a shirt, though, right?)

I pounded and pounded and pounded. Then I pounded some more. I thought that surely I had made some progress, so I reset the angle measuring doohickey to 90 degrees to check my progress.

Progress = 0.0.  Nothing. Nada. Zilch. Bupkus. A complete goose egg. In other words, the PATRV is either superhuman or wrong. This method doesn't work. Oh, I supposed I could keep trying bigger hammers. But I think instead that I will try some of the suggestions provided by others that have been though this.
I also had a hard time getting the 90 degree angle on the end of the longeron to open up- the soft hammer method simple didn't budge it. Here's what I wound up doing: step 1. Take the ten inch or so piece that you cut off the longeron to trim it to length and place it over the angle that you want to open up (this will protect the longeron from the next step) Step 2. I used a short 3# sledge hammer to beat directly on to the scrap piece on top of the longeron (as an anvil, I placed the longeron on top of my table saw cast iron top). You will really have to apply some force to get it to budge, but the srap piece will keep it from being otherwise deformed.
 I'm not too keen on that idea, and not just because I'd have to buy another hammer. It seems almost too brute force. And there would seem to be some risk involved. It wouldn't be hard to destroy the aluminum. I'm going to keep that idea in reserve and try this one first:

I used a 3/4 inch pipe coupling inside of the angle and squeezed it with a vice. Check it with a square and there should be about 1/16 of inch gap at the vertex.
That idea has a problem too in that it is contingent on finding a 3/4 inch pipe coupling. I'll try Lowe's for that.

I'm stuck for now, but I will stop by Lowe's tomorrow to look for a piece of pipe. I've been wanting to stop by there anyway in order to pick up a couple of lengths of rope so I can start practicing sailing knots. 

It's a beginning.

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