Rib questions

[quesauce]

A couple of questions for the group:

Has anyone used 2024-0, done the forming, and then had the formed ribs annealed to T3? There's a place not too far from me that does annealing and I've read that working the aluminum in a -0 state is noticeably easier than in T3.

Also, in studying the plans, I was contemplating making one cutting template instead of one per rib. Once each complete rib is formed, I would run the rib through the table saw to cut each to length. I'd be a little short given the kerf, but I don't think that's the end of the world as the gap can be taken up with the attach angles. Thoughts?

[Chris In Milwaukee]

The only thing I'd worry about with the saw method is catching the edge weird with the blade and mangling your rib. But with a good sharp blade, it may be a non-issue.

The full-size rib is 5-1/2 feet long, so it's probably going to be fairly unwieldy. You'll probably want to make a good, solid sled for your table saw with that approach, to make sure everything stays put, and is repeatable.

I wouldn't worry too much about the kerf. While you'll lost 1/8" of material in the cut, your spar is actually going to be thicker than that at the widest part. Just cut inside the line

I'm not qualified to answer the T0/T3 heat treatment question, I'm afraid.

~Chris

[quesauce]

The full-size rib is 5-1/2 feet long, so it's probably going to be fairly unwieldy. You'll probably want to make a good, solid sled for your table saw with that approach, to make sure everything stays put, and is repeatable.

Yep, that's exactly what I'm thinking of doing. I figured make a sled and put down some blocks to completely capture the rib. The table saw I'll use has a very long Biesemeyer fence so I think I can make it work pretty easily.

[Glenn Patterson]

These efforts to make the work simple will work against you.

Making the ribs in sections is the most accurate way to build ribs then tune their individual lengths. It also the most efficient use of material and time. If a rib is messed up then it is just a small piece of aluminum. The tail, aileron and flap ribs can be flip flopped on the sheet side by side to have virtually no waste. The nose ribs can be laid out for most effective use of metal as well. Cutting full length ribs would not allow good nesting of parts and the wastage would be very high. Trying to beat out all 66 inch ribs is not that easy either. The missing mid ribs in the fuel tank bays would be waste. It is not that difficult or require that much effort to make individual router templates. It is easier to work with and form smaller sections. We used a zipcut and or belt sander to tune the rib lengths if it varied from the rib templates. I clamped the belt sander on its side and the sander could take the rib to the final line quickly. There is no risk of damaging a finished rib by running it through a saw.

The full length rib form works for flanging the rib sections. It is in the technique using firm blows with the dead blow hammer to set the edge of the rib for flange then work it over. Use a second board that is about a 1/2 inch in all around inside the rib form as a clamp board so that the metal is restrained and the flange is the only metal moving. Keep the forms tight together in the areas being worked as you work the flange and it will go well.

Changing the temper of the metal is unnecessary. How does one confirm that the temper created is correct without valid Quality Assurance and Quality Control measures in place? In industry that type of effort to change metal states for critical service would have good QA/QC with testing to ensure that the metal meets the engineering specifications. It is risky to be altering metal states without good control processes as we risk our lives on the quality of the work and processes. Altering metal temper is an added expense and effort where none is required. The metal is best left in the original state.

[quesauce]

These efforts to make the work simple will work against you.

Very valid points! I hadn't thought about the material waste. I was thinking that it might be the most accurate means of getting a smooth transition across the rib/spar/rib joints but I think you're right in that it's more trouble than it's worth.

The place I was looking at doing the annealing does aerospace work so I imagine they're used to the required QA/QC. I don't think if I buy 2024-0 I can leave it untreated. I bet Bob was counting on the material properties of T3/T4 but I'll give him a call and check once AirVenture is over and done with.

[mswain]

Ernie Green, a scratch builder here in the Jacksonville area, pressed his ribs at -0 then had them heat treated

[Glenn Patterson]

Kevin,
The best way to be accurate is to make a full size wing pattern as you have done. That gives you all the layouts. Place the jig pin holes in the master pattern and use them for all the sub patterns. We drilled 1/8” holes on the master so that only the center of the lightening holes are transferred to the subsequent patterns & templates. Make the lightening holes in the routering templates.
To make the full wing form for hammering the flanges we through bolted a second piece using the jig pins with the screw heads countersunk. We made a back up master as well. The original is pristine and not mutilated. Then ran the hammer form through the router table with a 1/2 inch flush cut router bit with the bearing running on the edge of the master pattern. This gives a rib hammer form that is an exact copy of the master wing pattern. We ran a radius bit around for the rib flange corners. The jig pin holes & 1/8" reference holes are made to match on all the rib router templates, master back up and the hammer form set up. It is easy with a good master to spin off accurate router templates. I used 3/16 screws and wing nuts for holding all the patterns together & including the hammer form. All the ribs will index with the master if this process is followed. Make the router patterns for the longest length & cut them all. You could shorten the templates as you go but it is more precise to tune the rib. Everything on our wings indexed of the master and jig pin holes. Our wing is dead straight and looking through the end of the wing the jig pin holes line up so well that they appear to be one hole through all the ribs. The transition over the spars is seamless. We had to joggle our ribs to fit the spars. Some tuck the rib inside the spar and keep the rivets back from the joint to keep it smooth.

We used all MDF with no issues. The forming board got a couple coats of wood varnish to toughen then up & it still looks new.

Here is a write up that I did some years ago on how to make accurate tool & die for the wing parts all with a router and a circle cutter. This may give you a place to start and develop your own processes. There are faster ways of pressing the ribs if you have access to the equipment.

http://bearhawkforums.com/forum/tool...hawk-jigs-dies

The aluminum with the specified temper forms w/o any problems. There are hundreds flying or in progress of construction where temper has been a non issue. We did one practice rib and retired it as it was our learning piece. It looked fine but we did not want to chance using it. All our ribs came out fine w/o any misses. The internet is full of information and it can put a person in the ditch reading all the valuable tips. We almost got stung on the use masking tape to compensate for paint on the vertical spar bars. Nonsense. There is so much out there that it is hard to determine what is relevant or not. In this case I would dismiss the temper. Anything is possible but is it reasonable.

We generally followed Russ Erb & Eric Newtons processes or saw the end product & developed our own methods to get to the same place. You cannot go wrong with their CD's and get all the Beartracks from day one as they are invaluable as well..

All the best in your build.
Glenn