How many scratch builders out there ? you are all going to need them----

[fairchild1934]

Just to clarify-- the airfoil shaped ribs dont have the turned-edge--- only the "flat" ribs in the rudder and elevators. The stab ribs are the curved ones- and those are made on form blocks and dont have the turned lip. The parts Im trying to mfg are the exact ones in Rob's two pictures. Maybe i'm trying to turn
that lip at too much of an angle. Cant turn it too far in the brake because it its the hold down bar on the trailing edge end if it turns too far. im still on the struggle bus trying to get the widths exactly right at front and rear (template vs bent steel)

I found that Cleveland Aircraft tool has an edge forming tool that has two rollers welded to a vise grip designed for turning a flat on edges. Unfortunately it's shafts are facing the wrong way to get it inside the box section-- and the whole thing is too big and they dont make a Jr. sized one.

Rob: did you taper the width of the turned edge as it goes towards the small end ? That seems to be what the material wants me to do----
im using a 1/4 or 5/16 hold down bar on the brake--- so when you insert the 3 sided shape to make that final shallow edge bend-- the hold-down is about hitting the material before you start the bend. if I tapered the lip a bit that might relieve that interference.

I have a sheet of .025 4130 from spruce I have not cut into yet. I am currently using (possibly practicing on :-) ) .030 1008 from the box store. Seems to be bending well (cross grain bends)

PS---- I think at some point they went to lofted ribs on all the models for the stabs. (instead of just round tubing) But all the rudder and elevator ribs have non-curved steel ribs with turned flanges.

[Rob]

No mine does not taper. Same 3/16" wide complete length.

I have used hold down bars in the past also. But not all the brakes I have are the same. I have 3 different brakes. All with different upper clamping bar angles, and different leaf widths. Some things like this I am able to bend in one brake but not the others. So YMMY...

I my opinion you are getting a little too worried about it. I some cases the small end might get tweaked a little in multiple bending steps. You just need to go back and bend back in shape with duck bill pliers or hammer and dolly work to straighten back out. You just need a little turn down. Just a little turn down with add strength. But your just after a turn down to have a soft edge for fabric. You could just turn down with smooth duck bill pliers. Sometimes just a small bend to get a straight crease started makes it easier to finish bend with pliers. You can get it straight. Just take your time and work bending a little at a time back and fourth the length of rib. You can also straighten with a body hammer and dolly. If its not perfect it wouldn't be noticeable since the fabric shouldn't be touching the turned down edge.

[sjt]

I do not think the edge forming tool will work on steel. It turns down just a little on 2024

Maybe go to online metals and buy a 3/8x1/2 bar and a 3/8x3/8 bar. Tig weld them together and use that as a form block. You might be able
to sand the taper. I could not find a 3/8x7/8 bar.

Also, the procedure for closing the 2024 trailing edge by using a brake that might work for a much shorter piece of 1018.


I know the B-B secton is tapered but a brake can apply pressure on just one side. There is no need to pull both levers the same amount.

this is what my 2024 trailing edge form process looked like:
t.jpg

[fairchild1934]

I may be trying to make the
turned edge a little too wide. I was doing like 1/4 wide. I think its more important to have a nice clean uniform bend line than to have the flange be wider.

I am getting closer now to getting a good one------

will try to post some pics if I can remember how---- :-)

Tim

PS
I started out doing a 4 place---- but the overhauled O-320 I had seemed to be trumping the IO -360 that I didnt have----- (bird in the hand---)
along with the current IO-360 and O-360 core prices------- (not to mention O-540 core prices-)

[fairchild1934]

I think I just made a good one. width at each end about right--- the flanges look adequate----- and reasonably neat.

IMG_20240702_001519[230470].jpg
then there are the practice ones---- :-)


IMG_20240701_225450[230472].jpg

too wide--- too narrow--- flanges at 90 degrees----- completely closed ready to weld up seam---

[fairchild1934]

another question------ do we make the rudder counterbalance rib flat like the rear ones ? or do we make it a curved one to match the curved one on the stab that it kind of nests with. ??? I would guess flat---- but I don't think the plans say explicitly ----- maybe I need to look at B-Spot's video one more time ---- :-)

OK -- watched B-Spot again--- he uses a curved and formed over wood rib. So that's what I will do.
i would think flat would work - just wouldn't look as nice how the contours match at the gap. His videos are GREAT !

tim

[Camflyer]

Have you got Eric's manuals? That's another detailed resource

[geraldmorrissey]

The "turn down flange" on the non contoured Patrol factory ribs is .125 wide.

[sjt]

1/8 inch suggests the 45 turn flange is just to protect fabric covering.

[SpruceForest]

Those hor and vert stab ribs have additional form stiffness by virtue of that curvature; the straight C-section ribs benefit from that turned edge in gaining some additional resistance to buckling failure (although 90 degrees would be better, but tougher to fab in a home shop). I suspect that 45 degree turn is primarily structural, given a 15 degree tweak or chaffing tape would do for fabric chafe considerations and would be a bit easier to fab. That 45 degree tweak seems to suggest Bob wanted a bit more stiffness without appreciable weight gain.

[fairchild1934]

I think my bends are more like 30 degrees----- I would like 45 degrees - but on the little end-- there is no place for the lip to go during the bend.
the hold down plate is about 1/4 thick--- and even at 30 degrees--- I have to flex it open to get the hold-down inside it. The only other way I see to bend it might be sheet metal pliers. But that will turn the nice smooth bend line into a wiggly mess. So I resist trying that. I tried that on the first 4 I did that became scrap.

I am making the flange about 3/16 wide. Any narrower than that -- and the work wants to pop out from under the hold down plate while bending. The only other method I can see would be to make a metal insert for each rib--- and then fold the lip to 90 degrees (or whatever) and then slide the insert out the end.

One other way I thought of -- would be to block up the open ends of the rib and fill the rib up with cerrobend low melting point alloy. Try to fill it right to the bottom edge of the bend line. Once it cools and hardens---hold the outsides of the rib with bardwood blocks work the lip over against the hardened alloy. Then either slide the plug out or throw it into a pot of boiling water to get it ready to recast. I remember this stuff has a pretty dramatic miniscus when liquid. That might work against you if you were attempting an exact 90 degree bend. But might work for less servere bend.

(cerrobend and /or cerrosafe are low mP alloys of busmuth-lead used to bend copper tubing without kinks in the tube from a sharp bend. The one I used melted at about 195 degrees F. Its useful for many things. I used it when I worked at the radiation therapy place at the hospital. We had it in a 5 gallon stainless steel coffee urn. You just depressed the tap and if poured out like water. Still hot enough to burn you though)

Yes I bet thats right that the imperitive for the bend is firstly for fabric chafing and cutting. Another way to make them stronger-- would be when the rudder is all done-- to carefully fill each one with some high density 2 part expanding foam. that would give the bent flanges quite a bit of extra strength
against the 3 sided shape from collapsing on its self. You might have to pick a foam that would be compatible with the fabric glue (doesn't melt it)
i expect to be using stewarts-- so I dont think stewarts glue would hurt it being water based...... anyone tried foam inside for strength ?