Build Process Question

[Wolfpilot]

Grab your favorite beverage and sit back this is a long discussion/question LOL

Both my wife and I will be scratch building our Patrol together. She is very excited about doing this. I have experience working with processes in wood, metal, fabric, etc. In 2019 I took her to Airventure. This was her first exposure to the real world of aviation. We attended various workshops together to expose her to these various processes.

While we wait for our plans I have been going through the Bearhawk Builder’s manual. Showed her the nose rib blanks and other material I previously made when I was attempting a 4-place years ago. I am doing this to get her familiar with the work we will need to do. What is cool about this is she is asking questions I would never have thought to ask. When a person is used to doing things a certain way we tend to not think out of the box anymore. I love the new perspective she brings to this project. Here is her question:

“Wouldn’t it be better to build up a single rib first and be able to verify it was done correctly before mass producing all the parts like the Nose Ribs, then all the Center Ribs and so forth?”

It is a valid question when I consider what happened to me in a wood build I was working on. I built up all of the ribs per the plans and the jig. Then I built up the first spar. On a whim, after building the spar, I took one of the ribs and laid it out to grasp in my mind how it was going to attach and fit the spar. They did NOT match. The spar was about 1/8 inch wider than the leading edge of the rib. When I talked to the MFG about it, it turned out that the full size rib template was off due to errors created when it was printed. It was a common issue but I was never aware of it. Now I had 28+ ribs that needed to be modified (per the MFG recommendation).

So, when I think back on that issue, her question makes a bit of sense. She also acknowledged the fact that any issues similar to what I ran into on my other project would already have been identified, communicated, and changed via the engineering changes with a Bearhawk (which is a huge advantage of this build).

I also know some people build additional parts and use them for destructive tests. I think that is not a bad idea but it can also get expensive. In any case I thought this might be something to put out here in the group and get your thoughts on it. I love having a community like this to share thoughts and ideas.

[geraldmorrissey]

I would build the spar webs first. Make several small samples until you comfortable that they fit the mylar keeping careful notes about brake setup etc. Then bend up the fwd and aft spar webs. Then build the rib tooling to fit the mylar and the webs. Form one rib, check fit, adjust as necessary. Let the mylar guide you. Sounds backwards but setting the spar webs right makes everything downstream easier.
just my .02
Gerry
Patrol #30

[rodsmith]

I also know some people build additional parts and use them for destructive tests. I think that is not a bad idea but it can also get expensive. In any case I thought this might be something to put out here in the group and get your thoughts on it. I love having a community like this to share thoughts and ideas.
[/QUOTE]

If you insure that you use the correct material and thickness (ie 2024T3 not 6061 etc), I see no reason to destructive test anything, it is a well proven design. I do think it is a good idea to build a few spare ribs, just in case. Definitely keep all your rib forms in case you were to damage a wing.

[zkelley2]

No reason at all to do destructive testing. In fact it was already done. 2002 beartracks.

[Glenn Patterson]

We built the ribs then the spars. The master wing layout was traced on mylar using a light table that was glued to mdf for our master pattern. Once that is done a flush cut router bit can be used to run against the master to make identical duplicate wing templates that can be used for the hammer forms. One was cut into slices to have the shape gauges for bending the spars. Trial bends were done with with scraps to see where the bends needed to go on the long spar sections. The spars came out great. We bent 3 sets for both spars and end matched the best mates. The ribs and spars were on the same line so the ribs were joggled to go inside the spars for a very flush rib to spar fit. We did one trial rib and it turned out great. We had done a lot of learning on the first rib so we retired it to a wall hanger and never looked back with no do overs. If the rib patterns are accurate and the spars built using gauges from the same wing shape then there should be a minimal risk of a mismatch.

Do you reading, build it to the plans and do not over think it. Some of the conversations are mind boggling and go in so many complicated directions that are unnecessary. Some spin off in complicated processes to where the process becomes the project. Do what ever is efficient, gives a quality part and keep moving. Bob Barrows has built about 6 more airplanes In the simplest of shops and processes. Barrows aircraft may not win Oshkosh awards but they are good fliers. Scratch built take 1000's of hours so do what gets you a quality piece with the simplest methods and not invest 100's of needless hours in complicated process or musings. Ours was built to the plans with the one variance was eliminating the Bearhawk bump in the fuselage. Our fuselage follows the wing form over the top and flows into the top stringers. My partners thought that would add about 42 more inches to the top wing surface that may assist lift. It may do anything but it looks good.

[Wolfpilot]

I want to thank all of you for your comments. I agree it can be easy to over think some things but at the same time it never hurts to get some input. After reading your comments I was interested in Geraldmorrissey’s thought about spar webs first. I looked at that method and realized (after reading the Builder’s Manual that Eric Newton made (and I am familiar with his work) where he says “…Cut the .032 aluminum sheets into the correct width strips for the spar being made. To figure the width of the cuts needed, measure your ribs to determine the web height of the "C" channel….”

I guess when you consider the mylar rib drawing is the only basic full size reference and the ribs are made correctly to it there should not be any issues as Rodsmith indicates.

We will continue on the same path that most do with the build and have the confidence as to how it should turn out.

Thanks again to all
Rocky (aka wolfpilot)

[Glenn Patterson]

I think you have it. Make a copy of your mylar so you have the original and glue the copy to mdf then take the board down just to the line. Put all the jig pin holes in the master template. The jig pin holes can be used to secure another pc of MDF to it and take a flush cut router bit against the master template so every knock off or copy will be exactly the same. The finished wing is slightly larger than the drawing as the ribs have been folded over on the pattern and the skin laid over the ribs. The wing is still the exact shape just a whisker thicker than the pattern when done that is of no consequence. Maintain everything to fit with the master template & the wing will come together nicely. Slices of the working copy master template mdf at the spars will give the gauge blocks to determine how & where to bend the spars. The gauge block should be a snug fit inside the folded spar along its length. We glued white paper on spars that stayed on until taken off for paint. the paper allows clear conscise marks to work with. Bent scraps for trial with paper on also like mini spars until you have what want. Then with the marks on the trial pcs they can be used to mark where the brake has to be at the ends of the spar blanks. We were fortunate that a heating contractor allowed us to use his break at the end of a work day & he watched as he knew his brake. Gerald has it bang on. It is keep the work dedicated to the master.

[geraldmorrissey]

Whatever method you choose let the mylar be your beacon.
Gerry
Patrol #30