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General control line discussion => Open Forum => Topic started by: Curare on December 18, 2013, 07:54:26 PM
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Hey guys, some of you may have noticed my comments in one of the recent Sig Chipmunk threads.
Well, I took possesion of mine yesterday, and as you do, I rifled through the box, to see what I had bought.
I assume the wing construction is pretty well known, deep bottom spar square top spar, rear sub spar, and diamond leading edge, which is then sheeted over.
I was thinking how I could jig this thing, considering it has LE sheeting right over the diamond leading edge. I don't really like using the 'adjusto-jig' style jigs as I usually scallop out as much rib material as I can, and doing this after a wing is assembled is just not nice. My preference would be for a lincoln log style jig, or a bastardization of that.
I was thinking of using vee blocks on the underside of the LE, sheeting the top then flipping it over (while either removing the vee blocks or zona sawing them down 1/16" to a wedge sheape) and praying I can keep it all straight while I do the bottom sheeting. It sounds pretty precarious at best.
So, thoughts on this one?
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I've built several of those wings and believe the best way to do it is with an Ajusto Jig.
The construction does not lend itself to a lincoln log type of jig and you have to keep removing it from the jig to sheet it. Warps and twists!!!
The Ajusto Jig is perfect for that type of construction and will build it fast and accurate.
As for removing all the material you were talking about from the ribs. All of it won't amount to even half an ounce but makes the wing far less resistant to twisting and warping.
Sounds to me like your idea results in a lot more work to make an inferior product from a well designed kit wing!
The picture is a Geiseke Nobler wing in an ajusto Jig. Very similar construction and light and stiff. The Sig kit wing will build very much the same. This one weighed 7 oz including flaps and bellcrank.
Randy Cuberly
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I acquired an Adjusto-Jig many years back but have never used it, though I'd like to on a future project. I'm curious how you accurate locate the jig rod holes in a stack of already die cut ribs. I presume you use some sort of homemade template. The mylar one that came with my jig doesn't exude confidence. Any tips would be appreciated...
Thanks,
Gary
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I acquired an Adjusto-Jig many years back but have never used it, though I'd like to on a future project. I'm curious how you accurate locate the jig rod holes in a stack of already die cut ribs. I presume you use some sort of homemade template. The mylar one that came with my jig doesn't exude confidence. Any tips would be appreciated...
Thanks,
Gary
Hi Gary,
Yeah, I agree about the mylar template supplied with the jig.
I simply stack the ribs very carefully aligned with a common feature. In the case of the Nobler or SIG Chipmunk that is the trailing edge of the ribs. I carefully locate the best place for the jig holes where the jig pieces will not interfere with construction by using one of the jig rod holders placed on an end rib. Mark the locations of the rod holes then pin the stack together. I made some long pins from .030 music wire sharpened on one end with a grinder and bent to shape on the other end like a T-pin. Hold the pin with a pair of pliers and simply push it through the stack of ribs. One at the Leading edge of the ribs and one at the trailing edge.
Put the stack in your drill press and drill the holes for the jig rods all at once. Sometimes when using kit ribs with cutouts in the ribs it's necessary to temporarily glue small pieces of balsa into the holes in the ribs to allow a location for the jig holes. They can be removed eaisly after construction.
I think some of these might be visible in the wing in the picture.
This sounds a lot more difficult to do than it is. It works very well.
Set the jig blocks on the jig by measuring the rib distances from the plans. I use a long (36 inches) aluminum ruler to measure the placement of the jig blocks and then tighten the screws in the jig. I also use that aluminum ruler on edge to make sure all of the jig blocks are flat since the ajusto jig can be used to build dihedral into the wing.
Check the positions and when satisfied slide the ribs on the rods and rubber band them to the blocks. Easy and works like a charm.
You can build the wing complete except for the bottom center sheeting without ever removing it from the jig. I insert the spars first and glue them in place then the trailing edges then the leading edge and the sheeting. for the sheeting use aliphatic resin glue (like Elmers etc) and simply tapen everything in place with masking tape to dry. I can build a complete wing sans flaps and controls in about an hour...not counting the couple of hours for the glue to dry.
I then slowly slide the jig rods out about two inches on each side and install the controls.
Actually you may want to do this before putting the top front sheeting on.
After everything is dry remove the wing from the jig and install the flaps. Actually this can be done in the jig but I prefer to do it afterwards.
Randy Cuberly
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Thanks for the rundown, Randy. It sounds easier than clearing off my building board. And when I'm not using it, I can't stack tools and parts on it either. Win-win.
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I use the Adjusto-Jig in much the same manner as Randy describes above. But instead of holding the stack together with pins, I use a dot of glue stick applied to the forward and aft portion of each rib. I press the ribs together and the glue holds them in place. You can easily separate the ribs by using a putty knife after they are drilled. I also pre-treat each hole location with a dot of thin CA on each side of the rib prior to pressing them together. (Make sure the CA is completely cured before stacking the ribs or you will never get them apart!) This will allow for a much cleaner and stronger hole for the rods to go through and prevent the rib from splitting during construction.
Paul
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I use an Ajusto-jig as well and follow the basic procedure that Randy explained. Nothing else works as well for me. The first thing I built on it was a Sig Chipmunk kit wing, which came out great.
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Right, then I'd better pull my head in and get a adjusto jig!
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They want a fortune for those things on ebay. I wish I could find one to but I am not paying $300.00 for one.
Mike
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You can make your own jig. While that flies in the face of the racers motto, "Never make what you can buy". You will get the jig that you want ... there are some really good ideas on wing jigs on Brotherhood of the Ring.
Joe
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http://brodak.com/wing-jig-kit.html
A little more work but the end results are the same and the price is right. Build two halves then slide the rods half way into each half to put the two halves together and do the center sheeting.
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I still like my CLC wing jig, the Tom Morris Log jig and the jig you make when you build and I-beamer. But, my latest was built with out a jig.