Joggling

[kilohotel]

I'm just starting to bend the flanges on my center ribs. I know it is considered optional to joggle, but I've decided that I do want to joggle.

I've watch The Desert Bearhawk Project video on YouTube using joggle blocks after the flanging was completed and it looks like it works pretty well. The other option would be to add the joggle recess to the form blocks before starting the flange bending so that it is already incorporated.

What method have others used? What is the consensuses on the best method for joggling?

[Bcone1381]

If you Joggle them after you bend the flange, the bend radius at the joggle gets reduced. I've not heard of the idea of sitting the joggle first, but I think it has good merit.

Keep a generous bend radius for your flanges. There is a recommended minimum but I advice you to not get close to it. There is no maximum. I ran into issues on my nose ribs when fluting them due to not having a generous enough bend radius.

[Glenn Patterson]

If by joggling you mean to put the step in the ribs for the spar flange? I think to joggle to fit with the spar flange should wait until the spars are formed to see how the ribs fit up. We made the flanges to the exact rib height so we had no choice. If the rib is a snug slide fit in the spar flange then there is no point to joggling the ribs. We routered a duplicate of the MDF wing template and cut it to make reference templates or gauge blocks to bend the spars to get the fit and the flange angles. We practised with short pieces to get the fit and see where to set the brake shoe for the bends before commiting to bending the spars. We bent a spare main spar section so we matched the best fit.. If the rib flanges are formed over the wing template then the spar formed over the template is a match. We joggled once we saw how the final spar assembly and ribs fit together. We made joggle pliers with stepped steel blocks welded in to squeeze the joggle.

There has been several discussions on joggling or not to joggle. The no joggle is a slide fit and the wing skin is riveted back from the edge of the flange to keep a smooth transition.

Here is a previous discussion with a PDF that has a simple slotted joggle tool. It would have saved us building a set of form blocks.
Glenn

[fairchild]

Maybe im splitting hairs here...… but if the rib is made (without joggles) to just fit perfectly inside the spar---- wouldn't you have to add a 5/8 wide extra strip of skin material
on top of the rib flange to faithfully duplicate the master wing rib form's shape ? seems like if you didnt -- you would have a discontinunity in the top wing surface......

I think I WILL joggle--- but I havnt decided the easiest/best way to do it yet. I could make a short segment of the form block again--- and hand cut a relief and somehow work
the material sown into the relief (by hand--)

I could also maybe - somehow make a male-female jaw thing to mash in a tiny jog. The difficult part is how to make it interact with the bend radius area. All most need a pliars with a 3-rd jaw that is sideways to hold thhe other jaws and prevent lateral movement. anyone tried that ? The good part is that it only has to joggle a TINY amount.

T

[Glenn Patterson]

We adapted a pair of vice grips to form the joggle that worked really well. Vice grips give excellent control. My friend spotted this in someones build and built a set for our shop. We made a set of fluting pliers then made a set of fluting vice grips that worked better than the pliers. There is no visible lateral movement and if there is then best to give the metal a little movement. If it is restrained side ways then if it can't move then it likely would crush. This is the page out our of build log on the joggle. Some builders ribs went inside the spar so the remedy was to rivet the rib back from the edge of the spar flange to allow the aluminum to flow from the spar flange to the rib flange. No added metal required. the slope would be a .032 in an inch that is very small. Those that did not joggle said that was not noticeable. I see this was from 2006 so the conversations would be in abandoned Yahoo Bearhawk forum. A rivet line tight to the spar flange would naturally pull the skin down to be obvious. We left the joggle until the spar was built..

[kilohotel]

Thanks for the input on this subject!

I realize many topics like this have been discussed again and again over the last couple decades, but searching previous threads can be challenging and new (and old) info is very helpful for us newbies!

So without a clear consensus yet regarding the question of joggle or not joggle; I'm leaning toward joggling because that is what's shown on the plans.

But, I'm still not sure on the best method or time to joggle... so in the mean time, I am proceeding to form my center ribs without modifying the form block to include the joggle...

I tried an experiment with my pocket ribs by modifying the form block, after I had already used it to bend the flange without the joggle. I'm not pleased with the results because I could not hammer it enough to revised the initial set radius and it develops a "whoop" (see attached photos...I cant think of a better word than "whoop"...). Any suggestions to fix this concern?

The joggling vise grips look great! (Thanks Glenn !!) Are there any better photos/plans/sketches for these?

[Glenn Patterson]

I don't have any more info on the joggle tool. The tool is in the shop at my friends that is about 15 min out. If you are not in a rush I could get him to bring them into town and could take more detailed photos. We traced a mylar copy of the wing pattern that we glue to the MDF master template. I took a flush cut router then made an exact duplicate. The duplicate had the spar lines transferred to the copy. We cut up the duplicate master to make template blocks for bending the spars. We used scraps of aluminum with masking tape across the ends so we could put reference marks to set the shoe on the brake for the bend. Radius the corner of the template lightly so that it fits inside the spar trials as a go or no go gauge. The spar templates helped us to get the exact locations for the long bends. Measure and mark the reference points for the bend and locate them the same as the trial pcs and it will go well. The ribs were bent over the same form shape. the spar fits over the same master shape so spar and rib flanges should match.

Honestly if the rib is a snug fit slide fit inside then it is pointless to joggle as it is manageable. Joggling a slightly undersized rib would compound the drop in the rib which could pull the flange down so it is not a smooth curve over the spar. Placing the first rivet on the rib out from the edge of the flange worked for some to avoid forming a valley in the skin. Every builder does their best along the entire build and have to make tiny adjustments or compromises to get the product we want throughout the entire build. It is hard to be CNC precise with manual processes. It takes a lot of patience and measuring over and over to get it right.

Once we had the measurements for bending worked out on the scraps then we bent the spar sections. Again same process only longer. Masking take across the ends and the middle. Place the marks and check in the brake. If a mark is off then go back and check. It is a good way to catch an error. A piece of poster board with the reference ticks could be used to hold & carry all the mark references for the spar bends. The gentleman that allowed us to use his brake even let us adjust the brake so it bent straight and true. He bent ducting with it and the minor off in the brake did not did not affect his work. We bent an extra of each spar section. The spar ends were compared and the best matched ends paired together to be for a spar. The advantage of the spare is that if one spar blank is slightly out then there are still enough sections to work with.

Glenn