Here is one that was suggested to me.

 

Its not clear to me how much of the red area has to be routered out but this suggested jig is about what I would make, you need flat areas on each side of the cut for the router to rest on and the gap should be made to suit what ever pilot guide will be used, this type of jig would work you just have to make the sides of the gap to suit the cut, the depth of the cut gets set by the depth of the cutter. N

 

Hi Abraham, does the bottom of the cut on the spar have to follow exactly the shape of the rib (such as if you're putting on a skin of a specific thickness)? Or can it be flat?

Assuming flat is OK, the jig you show looks fine, except that I'd put in adjustable guides (or stops) on the ends so that you don't cut into the ribs. You don't really need accurate spanwise guides (the dark wood in your jig), because you're removing the full width of the spar.

You may have mentioned this in another thread, but what airplane are you building?

 

Hi Abraham, does the bottom of the cut on the spar have to follow exactly the shape of the rib (such as if you're putting on a skin of a specific thickness)? I don't really understand the question because the rib is where the routing stops. The cut will follow the spar and stop at the rib(s) Or can it be flat?

Assuming flat is OK, the jig you show looks fine, except that I'd put in adjustable guides (or stops) on the ends so that you don't cut into the ribs. You don't really need accurate spanwise guides (the dark wood in your jig), because you're removing the full width of the spar. Any suggestion how I can add these guides

You may have mentioned this in another thread, but what airplane are you building?

Building a Steen Skybolt

 

The jig looks OK, but only if the top of the spar is to be flat. If it is to be at an angle to match the shape of the green cross piece then you might need to set up the jig so it is at the angle you want. I would also suggest using a Japanese pull saw to cut the ends of the red area so the router doesn't have to travel all the way to the green. Even if the router eliminates most of the waste, you will still need to trim the small trianvles it will leave at the end. Perhaps another option would be to tape then clamp a half inch thick sacrificial piece on each side of the spar, then make the guide fit that. Route the spar and the sacrificial piece both, then your bit will make a cleaner cut and won't tear out and you won't have the remains. I assume you'll use a relatively short mortising bit with the guide bearing on the shaft end of the bit. I'd be very careful about the depth of cut and would sneak up on it gradually. Those FAA inspectors can be nit picky.

 

I would also suggest using a Japanese pull saw to cut the ends of the red area so the router doesn't have to travel all the way to the green.

Yes of course..

 

Careful, aircraft wood is $$$$$$$. The jig looks ok but I would use a chisel and wood rasp on the ends of the cut to insure I did not touch the metal ribs. What aircraft are you working on. I had to replace the wing spar on an Aeronca Champ rebuild. Started out with the metal framework and replaced everything else with new material. Fun project.

 

Forgot the money aspect do you know how much work would be involved if I damaged the spar:surprise:

 

thanks for the way better pic...

I believe Phil hit it w/ this one...

 

I am going to the airport today to set-up my new drill press and table saw. My mentor will also come-by today and eyeball all of my progress and I will run these ideas by him.
Can I get some suggestion on what kind of wood to use on this jig. The spar (yellow) is 1 inch wide.

 

Baltic Birch...
forget MDF...

 

Should be a fun airplane. I love bipes. Had the opportunity to fly a Stearman a few times. Original radial that used more oil than fuel and most of it ended up on the fuselage. Original counterweight, hand cranked starter.

Yes, I do know how much work would be involved in replacing the spar. Stringing it through all of those ribs is a task. I was in a club that rebuilt Classics. That is why I would hand work the area around the metal parts. Any info on how to do it in the Steen builders manual ? Good luck...

 

Steen builder's manual? Unfortunately the manufacturer only provides plans. So a lot is left up to the imagination. And again remember I am removing what the previous builder mistakenly added to the spar. The strips were only supposed to be in the area of ailerons and not the whole wing spar.

 

Abraham: check around, Steen originally had a builders manual for their airplanes. Might be able to find one on line somewhere.

check :Welcome to Beej's Skybolt They reference a manual for sale.

 

Sounds like it would be well worth the money for building and for maintaining afterwards. $35. might save you hundreds if it averts just one mistake.

Herb

 

I have that reference manual, and it does not give you everything that you need. If your building airplane from scratch it does help considerably but certain things you just need to figure out yourself.

 

My first attempt at making the jig was a failure. I had a pre cut 15 inch by 9 inch piece of oak from Home Depot. I also purchased a wood boring bit that will cut the turnaround in the jig. I made a big mistake because I just looked at the package of the bit and it showed a piece of wood on it and I assumed that this would be okay to use in a drill press. {It says on the package, do not use in a drill press} As soon as the bit penetrated the wood the oak cracked in half.

Another member recommended using baltic birch to make the jig, where can I purchase a pre cut piece of Baltic birch online? I also purchased the correct bit, (forstner) to make turnaround.

 

If there is a Rockler or WoodCraft near you they will have smaller pieces of Baltic birch and will even cut one for you.

Herb

 

Just purchased the Baltic Birch from Rockler.

 

Here is the oak board that cracked