Franks LSA

[Frank]

Finally able to start my project! First step is to turn mylar drawing #4 into a template.

I didn’t like the idea of gluing down the mylar and cutting it out: I want to preserve it instead.

And I didn’t like the idea of cutting to the inside of the line: once the line disappears I don’t know where I am.

Took the mylar to a reprographics shop and had it scanned.

At home, I took the scan into Photoshop and turned the single outside line into a double line, easy to do.

The inside of the two new lines represents the inside of the original line.

Now I have a line I can cut just to the edge of, leaving that reference line visible.

Printing full size was problematic so I ended by printing at home and splicing the pages.

A slight pain but it gave me the advantage of aligning to the mylar drawing more easily.

When everything was aligned I taped and spliced onto half-inch MDF.

I cut the paper drawing free of the board and was ready to apply spray adhesive.

In my first attempt I sprayed adhesive onto the paper and struggled to lay it down properly.

In the second attempt I sprayed the adhesive onto the board instead, masking off non-spray areas.

Also made a jig which would suspend the drawing above the board, allowing for easier application.

The mylar on top of the glued drawing matches well and confirms alignment.

Then used the jig saw to rough cut the piece close to the lines.

Replaced the 80 grit with 120 grit on the disc sander, but the soft MDF is removed very quickly at 1750 rpm.

Used the disc sander in this way to get close to the line.

But it was by turning the motor OFF and using the disc sander manually was able to refine the edge.

Turning the disc with my thumb and sliding the piece on the work table made minute adjustments easy.

A bright light helps a lot as well as supporting the ends of the piece.

Repeatedly laying it on top of the mylar drawing and taking it back to the disc sander did the trick.

Now I have a template which matches the mylar drawing just to the inside of the line.

Yay!

[Frank]

The modified drawing.

[Frank]

To prepare for the first aluminum order, working up a parts list and a materials list and learning a lot in the process.

Making a parts list forces me to examine the drawings very closely; there are certain things I don’t understand yet...

The materials list can’t be determined until I get on the phone and work out the best deal and delivery.

Planning for extra material to allow for 2nd and 3rd attempts. Probably need an extra sheet of .032 for spars.

Looking too far ahead and I’m overwhelmed. So I stick to the immediate steps I need to make.

Glad I had the plans scanned to files: handy to use the computer for studying, copy/pasting, even measuring.

parts_materials_1.pdf

[Ironaviationc]

Good information there mate

[davzLSA]

Hi Frank, Have you looked at Marks Rib and Spar blank kit? It would be a big time saver if it is worth it to you.

[Frank]

Hi Dave, yeah I should really take a look. Actually looking forward to making the ribs.
It would be nice though, if Mark would let me send him some representative ribs after I make them.
And then he could bend the spar blank to match my ribs - the 8 foot brake being something of an obstacle.

[johnb]

See the video in my post John's LSA build. Just posted today. I built a brake, and had good results.

[davzLSA]

Mark is very easy to work with, hit him up, you my be surprised.

[Frank]

Update: improved the 4 x 16 worktable a bit but certainly not a perfect reference plane, but OK for making ribs.

The plan is to create a spar assembly jig on the table using a laser and make that perfect.

Then disassemble the table and make room for wing assembly jig when the time is right.

Currently I have the master and working templates done, the form blocks and backup block, and the router cutting templates.

I picture the my master template as a duplicate of what Bob used to make the Mylar “full size wing rib form block layout”.

My intention is to use two full length form blocks for all the rib sections, left and right, with a 10° bevel and indents for flutes.

I just put in an order for .020 and .025 2024-T3, enough to make the ribs (except for no. 1) plus extra.

Will work on the form blocks while waiting for the shipment. Looking for a router bit for the bevel and indents.

Use a HF trim router or other small rotary tool for all the bend radii, then harden the edges with varnish/epoxy.

Always reference back to the master and working templates, maintain the dimensions and contour.

My plan is to flange all of the ribs first, before cutting any lightening holes either in MDF or aluminum.

Made a table saw sled for trimming templates and rib blanks to length.

Will use the table router to trim the edges of the aluminum blanks, in multiples.

But I want to use the drill press and fly cutter to cut lightening holes at 300 rpm.

Testing this method works so far: cuts nice holes and circles, dust is manageable.

Can add 40° bevel to the male dies using sandpaper and the drill press as a vertical lathe.

I don’t see an advantage to having the holes cut in the MDF or blanks before flanging.

Will have to cut 400+ lightening holes individually, though.

Form the lightening hole flanges with the dies and arbor press.

Also on the near horizon is to contact EAA technical counselor(s) and arrange for meetings.

And pretty soon start an EAA builder log.

So far things are coming together nicely and it is quite enjoyable!

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[Frank]

Little problems which have to be figured out. Like how to safely uncoil 4-4x12 sheets of .020. Bar clamp the roll to the workbench in such a way that when the packaging tape is cut, only the free end will come out. Thwack! The rest stays clamped down. Thereafter, using spring clamps to hold the roll together, ease it out gradually. The potential energy diminishes as it unrolls and by the end, it's easy to handle. Nothing brilliant but made me happy.

My layout of the rib sections is tighter than what I had calculated, so there will be even more excess than planned. But I didn't order all the .020 at once so I'll be able to use it. Also ordered some .025.

The Harbor Freight snips work great, easy to cut this thin material.

Realized now that all the cutting template holes need drill guides, not just the master and working templates. I'm using 5/16 x 3/4 tension pins which fit snugly in the MDF. The inside diameter is just right for the 3/16 carriage bolts.

[BTAZ]

"I don’t see an advantage to having the holes cut in the MDF or blanks before flanging."

Depending on how you approach cutting the lightening holes. I put the rib blanks in between the MDF routing templates and drilled "starting holes" in each lightening hole. Then I routed both the outside of the blank and the lightening holes instead of using a fly cutter.

[johnb]

I did same as BTAZ. It worked well and was faster than fly cutting each rib.

[Frank]

That does seem to be a popular method. But here's my thought process, such as it is:

The LSA book of instructions is clear on the sequence: "After forming the rib, it's time to cut the lightening holes and flange them." Also on the forum someone had this confirmed by Bob (now I can't find that comment).

My intuition is probably worthless since this is all new to me but I suspect having lightening holes as close as 1" to the form block while flanging the rib is an invitation to unnecessary deformations, not that I've seen any complaints about this.

I like the router for trimming the outer edges of the blanks and I have the shop vac set up to catch 100% of the debris from these cuts. The rough-cut blanks will all be within about 1/2 radius of the cutter for the outer edges.

But how to efficiently vacuum while cutting inside the holes with the router which is using the full diameter of the cutter? There's probably a way. But I think controlling debris will be easier with the 300 rpm drill press.

Router versus fly-cutter each have their own safety issues. On the drill press I can clamp the work down and use the column as a brace. And I have a plastic shield on a goose-neck placed in front of the work. The router means I have to rotate the work on the table and concentrate on how the circle is fed into the cutter.

The router is loud, the fly-cutter is not. Nobody would hear me scream over the router noise.

As for speed of fabrication, Bob would have us doing it all by hand!

Edit: Though come to think of it, if you flanged the all lightening holes by hand with the bob-stick, as instructed, you'd have a lot of them done in the time it takes just to get set up with templates and dies and so forth...

[BTAZ]

Certainly lots of ways to do it and some of them will be best defined by our surroundings.

The router does make a mountain of small chips that end up everywhere and it is noisy(wear hearing protection). Best done outside where you wouldn't mind seeing aluminum "snow" for a few months after you are done.

As far as flanging, I used the "rubber press" method. It simply required using the router to chamfer the lightening holes in the form block and a hydraulic shop press(with some random metal chunks for platens and a stack of random rubber for the working). Saves time over making multiple flanging dies but again, more than one way to do it.

Not sure if you have seen it, but when I finished mine I posted links to a pretty extensive build log(IIRC, it is in my "First Flight" post from about three years ago,)https://bearhawkforums.com/forum/bea...t-flight-today). Again, it shows how I did things, not necessarily the best way but one way that led to a flying airplane.

[Bcone1381]

After making a set of ribs using the wood die method, I believe that the rubber press method superior. The apparent quality after flanging was superior, meaning way less deforming took place with the rubber press.

[Frank]

Thanks BTAZ, I have your wings .pdf and have studied it! (I'll download the other two now make sure I don't lose them.) Pretty sure I'll cut lightening holes with the fly cutter. But I should carefully weigh the option, as you suggest, of the rubber press method!

[Frank]

Drawing outlines on the aluminum sheets and rough cutting with snips. The .020 cuts easily and the parts can be laid out very close. The .025 cuts less easily and needs a little more space between parts.

In retrospect, if you’re going to layout everything on the computer to estimate material needs, then you might start by laying out the skins first. Start with the biggest parts and work down to the smallest.

Also in retrospect, while laying out the rib blanks on the aluminum with the sharpie, I could have made punches for the jig pin holes at that time. On the other hand, punching after the rough cut allowed me to punch two blanks at one time.

I used a hammer and awl. A precise 3/16 center punch might have been better.

All the holes in the cutting templates have 5/16 OD steel tension pins with ID of 3/16. On the drill press, the guides not only protect the hole but also help to center the drill by pulling the piece into alignment.

The initial jig pin holes drilled first. A 3/16 round file is helpful. Then, many blanks can be sandwiched together and the other holes drilled. While the sandwich is pinned, individual holes can be reamed out. This results in a blank which fits easily over the pins. In reality, these are 3/16 x 2 1/2 in. carriage bolts, flat washers and wing nuts.

Sandwiching five blanks at a time (four at a time for .025) ran these through the router with flush cutting bit. The cutter has two straight blades which throw the tiny chips horizontally. A vacuum attachment is set as close as possible and catches 90% or more of the chips.

The nose ribs will be put back into the template sandwich and the 3/16 relief holes drilled and filed. Likewise, the relief holes of the aileron and pocket rib notched flanges to be drilled. Then I plan to cut the notches first with the jig saw and finish with the file. The holes on the LSA measure 3/16.

So that’s where I’m at now. Next step will be get the form blocks freaky for flange-making.

https://www.dropbox.com/s/86ptmvzd0trg53i/nose%20ribs4.mp4?dl=0

Also, I have been advisedto take off the gloves while operating stationary power tools that have moving or spinning parts. I intend to learn this lesson from advice and not from experience!

https://www.osha.gov/Publications/osha3151.pdf
https://www.osha.gov/Publications/osha3170.pdf

[Frank]

Also in retrospect, and this is likely aesthetic only, the center rib template and blanks should probably have an angle added to front and back top flanges. An angle is indicated on the nose rib in the plans but I didn't extrapolate the corresponding angle on the center rib flange. Likewise the center/back rib. This is because, although it's a "90 degree flange", you're folding over an additional angle, making it a compound angle and the straight line becomes a bent line when you fold it over. Which means, the folded edge of my center-rib-flanges will angle away from the bend. That edge of the flange will not be parallel to the spar. Easy to check out with a scrap of paper. And better do that before cutting the piece.

Not to worry, but makes me wonder: where else might I fail to extrapolate, and where might that happen in a more significant way?