| 51 | First Rib - Lessons Learned | 4/22/2006 |
| | I was really excited to have the first rib in the jig (one with bad wood that will be a wallhanging) and read on the T-88 box that it cures overnight. So, first thing in the morning I made tracks for the shed and checked in the the rib. It looked great. I then pulled it out of the jig and it came out fairly easily. I layed it on my bench and left to do my Sat. morning errands. When I returned 3 hours later a disaster had occurred! The gussets in the nose area let go and the capstrip had sprung back out and ruined everything. Next time...
- Although there was heat in the shed while I was building the rib, while the glue cured overnight the temperature probably dropped into the 30's. The instructions say to give T-88 a week at 35 degress, but will cure overnight at 77 degrees. The glue had not fully cured.
- I'm going to modify the bending jig and try to steepen the bend so that after springback it's closer to actual profile of the rib. This will prevent the gussets from being loaded up before they actually take loads from flying.
...back to the drawing board.
Man hours: 1 |
| 50 | Shop Maintenance | 4/20/2006 |
| | I found myself with some unexpected free time this evening so I headed straight to the shop. If you have a Delta 4" belt/6" disc sander you probably already know that it's a pretty weak tool. The new belt (3rd belt since I bought it 2 years ago) came in yesterday so I took it apart and replaced the worn belt. No teeth left on it in a couple 2 inch sections. After that I made a couple sanding tools that are really handy. All you have to do is cut a couple small pieces of aluminum plate into convenient shapes, file off the burrs, and T-88 handles made from pieces of a paint stick on. From model plane building I had a roll of adhesive backed sandpaper that you can stick onto the little sander. Great for fine work.
Man hours: 1 |
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| 49 | Trimming Gussets | 4/20/2006 |
| | When you T-88 the gussets onto the rib there is a small overhanging edge I leave to be trimmed off. I bought a laminate flush trim router bit. All you have to do is set the bit high enough so the ball bearing end rolls on the rib. Then just run the rib past the bit. It comes out perfectly smooth and doesn't touch the capstrip. It's impossible to make a mistake and the results are unbeatable. I did this with the test gusset and this will be how I do all the others.
Man hours: 0.5 |
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| 48 | Crush Test!!! | 4/20/2006 |
| | To establish confidence in my wing I made a copy of a single joint in my rib, the one with the smallest gusset. I figured that if it performed satisfactorily in my test I will be happy with the rest of the rib. Also, the amount of localized force I applied with the vise far exceeds anything the wing will encounter flying. As you can see the gusset is not the weakest link in the rib so I will go ahead with rest of the rib construction as planned. I slowly closed the vise so I could see the capstrip flex and keep the gusset under stress for a while. After continuing to close the vise the capstrip snapped. I turned it around and then crushed it again. You can see that although the gusseted joint came apart, wood is missing from the plywood and the capstrip failed as it split in the direction of the grain. Again, this was an extreme test and in actual use the ends are not free to move like this since they are secured in a truss arrangement.
Man hours: 0.5 |
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| 47 | Inspection of Wood | 4/17/2006 |
| | One thing I don't really like about the project is having to be somewhat of an expert on things that are life-critical,
which narrows it down to everything in the plane. My latest dilemma was wood quality. I had some obviously
questionable pieces of wood mixed in with my last order which inspired me to scrutinize the rest of the order. In doing so I
found some pieces with rather curvy grain and didn't know what the final word on the subject was, so I called EAA.
They referred me to Advisory Circular 43.13. I read a section that discussed grain on all four faces and thought
my wood was bad. I didn't realize that they were only talking about cross grain wood. If the grain is vertical
there are no grain lines on the side. So, it turns out that only about 1/5 of the order is bad, not the original estimated 1/3.
This is where the learning part of home building kicks in. You never study something
as hard as when you imagining it lifting you up a few thousand feet. This was another place where the matronics list
really helped me out. I posted my question and within a few days Bill Church hit the nail on the head and gave me reassurance
that my assumption that side grain lines were impossible was correct and that I was reading 43.13 wrong. So while I don't
always feel comfortable assuming the role of expert I think I'm learning fast. That's the beauty of this kind of project. It's
ALL good. |
| 46 | Testing Jig Clamps | 4/16/2006 |
| | I made another pair of my smallest gusset. I then mocked that joint in the jig, applied some T-88. Tomorrow I'll flip it over and do the back. I'll let it fully cure for a few days and then crush it in a vise. I was very satisfied with the clamp. The gusset didn't move around after I set the clamp. Others have told me the clamp will not work well because the gusset tends to change position. I think that's because most clamps aren't applying force normal to the plane of the gusset. This clamp does. I'll run it past the router with laminate trimmer bit and see how I like that too. Good time to get a method in place so I can produce all the ribs with an identical process.
Man hours: 0.5 |
| 45 | Gussets Complete | 4/15/2006 |
| | Another Saturday out shopping with the wife. I did manage to get some quality shed time though. I headed out at 9:00PM with the goal of sanding all the remaining gussets. The belt sander was starting to complain by making a lot of thumping and generally rough operation. I pulled the disc and cover off and the belt is shot. I'm lucky I made it through. I have another belt sander I can use for the capstrip shaping during the rib building process until the new belts come in. I'm going to order 2 or 3 belts tonight. I came in at 11:30 mentally prepared to make my first rib tomorrow. I've been thinking "I'll make the first rib tomorrow" for months. ...but I think this one is really a go. I have the steamer, bending jig and rib jig all ready, all the gussets are done, now all I have to do is START BUILDING THIS PLANE!
Man hours: 2.5 |
| 44 | Another Book | 4/15/2006 |
| | I'm not a pilot yet so while I was killing time while my wife shopped I went to Borders and checked out the aviation books. I picked up FAR/AIM 2006 which I'm hoping will provide some of the "ground school" type information I'll need. Seems like a good resource to a non-pilot newbie. |