Plan clairification -

[fairchild]

Hello all---
I have finished forming all my nose ribs --- I have alodyned all of then and am priming them with stewart's eko-poxy. .
I am about ready to start making the tooling for the big center ribs. The plans look fairly clear--- except--- I don't see a dimension for the diameter of the lightening holes.
I cant remember how I determined them for the nose ribs. I don't see an explicit size for them on the plans. how do we determine how big to make them ?
and whatever that size is--- would that be the hole size BEFORE bending the flange down to 30 degrees ? ( I would think so .. )

( I think on the nose ribs-- I blew up the plans 2X and used the diameter of the 2X magnification. The master rib mylar only shows the center of the lightening holes.)

Tim

[marcusofcotton]

Scale the plans. Yes, before bending the flanges.

[fairchild]

I was a little uneasy about doing that (though that's probably what I did on the nose ribs) because I remember finding that some things on the plans are to scale and other
things don't seem to be...….

[S Lathrop]

There are cad drawings for the wing ribs on the old Bearhawk site (A model). You might find those helpful as you work to interpret your drawings. I am assuming you are working on the B model wings.

I do a lot of CAD drawing and I found it helpful to make my own drawings from the plans. For me it is kinda like "measure twice and cut once" practice. When doing the wing spars, it saved me a lot of time. I found that Bob had located everything on an exact spacing of the rivets and all I needed to do was make a drill jig to produce that spacing on a piece of steel 18 inches long, the width of the spar strips. Then drill the holes in the spar strips and then the spars themselves. I did use a CNC mill to make the drill jig. On other parts, doing my own drawings helps me plan how to make the parts.

[fairchild]

Can you clarify what (or where) the "old" bearhawk site is ?????

[jaredyates]

Probably this: https://groups.yahoo.com/neo/groups/Bearhawk/info

[Chris In Milwaukee]

There are cad drawings for the wing ribs on the old Bearhawk site (A model). You might find those helpful as you work to interpret your drawings. I am assuming you are working on the B model wings.

I do a lot of CAD drawing and I found it helpful to make my own drawings from the plans. For me it is kinda like "measure twice and cut once" practice. When doing the wing spars, it saved me a lot of time. I found that Bob had located everything on an exact spacing of the rivets and all I needed to do was make a drill jig to produce that spacing on a piece of steel 18 inches long, the width of the spar strips. Then drill the holes in the spar strips and then the spars themselves. I did use a CNC mill to make the drill jig. On other parts, doing my own drawings helps me plan how to make the parts.

You’re honestly making it harder than it needs to be. The Bearhawk isn’t a precision-punched RV. The important measurement is the spacing between the ribs, that’s it. Mark and drill those holes. Then use a rivet fan and adjust it so that the spacing between the rivets is as close to an inch as you can get it (there’s only one spacing on the fan that will do that). Boom, no precision jig required. Pretty sure Bob doesn’t expect anyone to measure to .02” on anything.

https://bearhawkforums.com/forum/bea...5163#post25163

But the CAD exercise is fun. It is all about education and recreation, right?

[S Lathrop]

Chris;

I probably did a bad job of explaining how I did my spars. First I made the end plates and splice plates, water jet cut. Next I drilled all the cap strips to the exact rivet spacing that Bob designed. To get that number I had to do a Cad drawing of the spars. I also made a drill fixture to do the vertical holes for the rib attachment angles and spacer blocks. With these pieces and drilling fixture, I only had to locate the upper cap strip on the spar and transfer the holes. I hate to do layouts because every time you lay out a part, you introduce the potential for some variations. I do lay outs once and produce a template. Bottom line was that all the similar wing parts were interchangeable until final assembly when the parts were riveted in place.

Old habits are hard to break. This is my first airplane but I have build hundreds of race cars over many decades. Some of those cars were aluminum monocoque construction (think aluminum fuselage) the others were tube frames, not much different from tube fuselages. I guess that I am so use to a certain degree of precision that I just can't work any other way.

[Chris In Milwaukee]

Chris;

I probably did a bad job of explaining how I did my spars. First I made the end plates and splice plates, water jet cut. Next I drilled all the cap strips to the exact rivet spacing that Bob designed. To get that number I had to do a Cad drawing of the spars. I also made a drill fixture to do the vertical holes for the rib attachment angles and spacer blocks. With these pieces and drilling fixture, I only had to locate the upper cap strip on the spar and transfer the holes. I hate to do layouts because every time you lay out a part, you introduce the potential for some variations. I do lay outs once and produce a template. Bottom line was that all the similar wing parts were interchangeable until final assembly when the parts were riveted in place.

Old habits are hard to break. This is my first airplane but I have build hundreds of race cars over many decades. Some of those cars were aluminum monocoque construction (think aluminum fuselage) the others were tube frames, not much different from tube fuselages. I guess that I am so use to a certain degree of precision that I just can't work any other way.

That’s awesome! you’ll probably have the most precision Bearhawk in the fleet.

[fairchild]

Just so everyone understands--- I always try to make everything harder than it has to be. later - after im done - I see how I should have done it simpler :-)
T

[davzLSA]

I thought I was the only one that did that?????

[davzLSA]

The more you suffer the more it shows you really care?

[Chris In Milwaukee]

Who knew you could relate the Offspring to airplane building? Now that I think to some of their other songs, I guess I’ve had a lot of Offspring moments during building adventures.

[N3UW]

Tim,
Make your life easier and get an Engineers Scale. Basically a ruler with different scales so you can simply read off the plans without doing math or blowing up the drawings.

Pro Art 12-Inch Engineering Scale

https://www.amazon.com/dp/B0027ACK7W/ref=cm_sw_r_cp_tai_8si0BbZ6CH1W2

[fairchild]

That sounds like an excellent idea. I found 5 of them in a drawer-- but they are all about 50 years old and mostly ill-ledgeable now. I will get a nice new bright white one with clear
easy to read marks. :-)
Tim
PS---- John----Watching your videos make me think I can REALLY do this ! They helped me decide to pull the trigger !

[N3UW]

Great. Glad the videos helped. Remember the project is just a bunch of small individual jobs. Don’t get overwhelmed looking at everything. One step at a time and try to make consistent progress

[fairchild]

Yes---- I am doing that- steady progress. I think the ribs are going fine- and pretty rapidly. I expect the spar to be the most intensive and demanding part of the whole plane.
(not much room for any error) By the time im tacking steel tubing together - Ill feel like im all most home ! :-)
I grew up doing down-to-frame restorations on classic cars. I think that helped me to not get in a hurry when I work.
After helping my cousin restore his 34 Fairchild-- I thought--- I could build a plane from scratch quicker than restore one (at least one that old) -- so here I am...…
and like the Blue Angels pilots like to say---- " Im just glad to be here"

Tim

[fairchild]

Got hole dimensions from Maria/Bob---- will post shortly here. ( Thanks Maria/Bob)