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Archive for September 19th, 2012

Tie Down Stop Options

September 19th, 2012 No comments

Set Screws for Tie Downs

I placed an order for some set screws to thread into the tie down blocks from McMaster-Carr. The theory is that that set screw sits inside the tie down blocks and remains there. Then as you insert the tie down rings, they hit the set screws and will stop. This allows you to tighten down the tie down rings without crushing the skin since there is a gap between the tie down block and the skin.

I ordered a pack of the above as one option. They are 3/8″ long with a self locking patch on them. This should help them from rotating out of the tie down blocks if I choose to leave the tie down rings out of the plane until needed.

Another Tie Down Option

Another option was to get some smaller set screws and use two of them as jamb screws against each other to keep them from vibrating out. Both are stainless, just like the tie down rings. I have not decided which to use and when I do, I will likely offer the extras to other builders since I have many extras.

Categories: Major Wing Sections

72 Nutplate Holes Done in 20 Minutes? Yah Baby!

September 19th, 2012 No comments

Nutplates in an Instant

Sorry for the lousy picture above, but I had to get a shot of the FANTASTIC tool I was able to use. Now that the Z brackets are drilled to the spar, the next task is to drill the nutplate holes and countersink them to accept the nutplates that are used to bolt the tanks to the spars. There are 36 holes that need nutplates. This means 72 holes to drill and countersink.

Typically, you would use the nutplate as the drill guide for the #40 rivet holes. Some do this by bolting a nuplate to the bracket from the underside and then using a block of wood that has a relief in it for the bolt head, drill a hole in one wing of the nutplate through the bracket into the wood, insert a cleco in that hole, and then drill the other. Then you have to repeat for each hole in each bracket. Once done, you then have to countersink the aft side of the bracket to accept flush rivets as this face sits against the spar. They do make drill jigs to speed this process up, but they are a bit pricey. It eliminates the need to bolt the nuplate to the part, but still requires the holes to be drilled one at a time, flip the jig and drill the other.

I was not looking forward to doing these. The time it takes is simply ridiculous. I sent a text to a friend that I know that works in aircraft assembly and asked if he had at least a nutplate jig. After a few messages back and forth, he said, “I have a better way. Meet me tonight.” Boy did he ever.

Basically, he had a pneumatic tool made specifically for doing nutplates. It uses a center pilot the size of the bolt hole that when engaged, it acts like a cleco, pulling the part to the tool. It then has two drill bits on either side, exactly at the spacing for the nuplate rivet holes, that plunge simultaneously to drill the #40 holes. Wait, that is not all. The bits also have countersinks on them. So at the end of the drilling, it also countersinks the holes. In one trigger pull, you get perfectly aligned rivet holes, that are countersunk all in about 10 seconds. Most of that is inserting the pilot and lining up the part to the tool.

Needless to say, I knocked out all 36 nutplate locations in less than 20 minutes and was left with parts that only needed the backside of the countersunk holes deburred. I could hardly believe my eyes. It is certainly true what they say about the right tool for the job.

Nutplate Holes Ready in a Flash

Here you see the result. I did this bracket in 30 seconds. Some of the nutplates will little askew, but they are nutplates you will never see…and it was due to me not being quite aligned with the part on the tool. No biggy, they are close enough. Needless to say…that was the coolest tool I have ever used. Next up, I will prime these (sans the flange that will attach to the tank) and then rivet the nutplates on with a squeezer. Then I will bolt them to the spars and continue with the “Checkoway” method in the next few days.

 

Categories: Tanks