Method for cutting big holes in ribs-

[fairchild]

Noticed mention of using a fly cutter for cutting the big lightening holes in the rib blanks. From my previous but limited experience with fly cutters--- the idea of trying to
cut through thin sheet metal with one- seems really scary ! I would expect that when it starts to go through it will grab and then wad up the work like a ball of tin foil.
Not sure if a hole saw might have a similar problem........ Is there a "cleaner " way to make those holes ? Is there a superior style of fly cutter thats up to the job ?
Do yall make a cover plate that clamps down over the work and puts downward pressure on the work to prevent it being "grabbed" by the cutter ?
There must be a clean way to do it---- short of punching it somehow----
Tim

[Chris In Milwaukee]

Using a router with a wooden template is a popular option, and very repeatable. Check out my “Having a Rib Party” thread to see how I did it.

https://bearhawkforums.com/forum/bea...ng-a-rib-party

Chris

[S Lathrop]

I did the same process as Chris. I made a pattern for each rib out of 3/4 MDF board. For the wing ribs, a pattern for the end rib is sufficient to make all the other ribs that have similar shapes.

I used dowel pins to align the rib blanks. I used a thin plywood over the rib blanks to protect the ribs from the router. Here is a picture of the tooling for the ribs.

I found that I could route 3 ribs a time and it took about 3 to 4 minutes.

The picture shows the pattern for the ribs on the left. The protective covers for routing the ribs the form block for the rib flanges on the right.

[Bdflies]

I've used flanging punches: https://www.mittlerbros.com/aircraft...lare-sets.html
I don't know how many sizes would be required to do the ribs. These punches aren't cheap, but they work beautifully!

Bill

[BTAZ]

I routed my holes at the same time I routed the OD of the rib blanks. I used appropriate hole saws or an adjustable fly cutter as required to put the hols in the router templates.

Once the blanks were sandwiched in the template, I used a step drill to put a starter hole(roughly 1" in diameter) in each of the lightening hole locations of the blanks. Once the OD had been routed to size, I simply lowered the stack down over the router bit and routed out the holes. This didn't add much time to the overall "blank forming process".

Once the blanks were all routed out, I chamfered the holes to 45 deg. on the router templates and used them for rubber pressing in the flanges on the lightening holes.

I did make a flanging die set to flange the rear spar holes.

For the spars, I was able to source the appropriate hole saws on Ebay for about $15/pc. Was a bit less stressful the taking a fly cutter to parts with that much labor in them.

[fairchild]

My apologies---- I re-watched the youtube video From Mr. snapp where he uses the router method--- I had watched that a couple years ago and forgot about him using that
system to cut the lightening holes. I have a big almost new router. Making a table for it now- that should work nicely. I have a whitney foot powered punch I can use to
make the starter holes for the bit. The router way seems 100% easier than a crazy fly cutter ! :-)
Tim

[bergy]

I bought a second/smaller router for my Patrol project ( my larger router was way too bulky and heavy, would not even fit under my router table). The only advantage of router was that I could rapidly turn tall stacks of pristine 2024 aluminum into smaller pieces of scrap that were then good raw material for making attach-angles. I hated the mess and the little aluminum chips in my underwear; I hated the noise; I hated having to smooth out the finished cut left by the router. I soon quit using the router for anything. I used a fly cutter ($12 on ebay) for any holes larger than 1.5 inches and never had any problems. My drill press is belt driven and is set up perfectly for either drilling regular holes or spinning the fly-cutter; if a drill bit gets stuck or the last fraction of an inch of a wing-rib snags the fly cutter (a rare occurrence) the drill-press belt starts slipping. Plain old wood-working paddle-bits of the type with sharp little cutting tips on the outside corners work great for smaller holes

I've used a pair of vintage straight tin-snips for almost everything. I found that my best ribs are those where I cut my rib-blanks about 1/16" oversize, did my flanging and fluting next, and then trimmed/deburred the flange edges with my little belt-sander.

If I had to do it again I would not have bothered to buy the little router.

[Bdflies]

Chips in your underwear!?!?

Bill

[Chris In Milwaukee]

They certainly find creative ways to get into the strangest places.

[geraldmorrissey]

I use a fly cutter for the spar web holes with success. I used lots of big clamps which is the key to keeping all your fingers. It is a little scary at first, just take all the safety precautions and treat the thing with respect.
Cheers
Gerry
Patrol #30

[Chris In Milwaukee]

I use a fly cutter for the spar web holes with success. I used lots of big clamps which is the key to keeping all your fingers. It is a little scary at first, just take all the safety precautions and treat the thing with respect.
Cheers
Gerry
Patrol #30

I, too, used the fly cutter for the spar holes. Yes, yes. Clamp it well!

[fairchild]

YES- chips in your underwear ! Chips in your ears, chips in your hair- chips in your socks- in your pockets-
I have my router table all most done. Since it makes a geyser of tiny chips - I am thinking of making a square of thin plexiglas mounted to a bracket on the table---
have it hover over the table to about 6 or 8 inches over the bit to try to keep the chips from going airborne and in my face and down my shirt. Dont know it it will
work till I try it.....
Tim

[Chris In Milwaukee]

“Chip Geyser”. Yes indeed. And... and... those chips in your sneakers will get picked up by TSA scanners, too. Why don’t they believe me when I tell them I’m building an airplane in my basement?

[S Lathrop]

I used a router to cut all my ribs and all the spar holes. The chips were an issue but a few things I did minimized the chip issue. And now that I am writing this there is one thing I could have done that would have made a big improvement to contain the chips.

First, I mounted the patterns to a board. I used 3/16 dowel pins to align the rib blanks, the pattern and a cover plate over the parts I was cutting. I hand held the router. In post #3 you can see the cover plates. The cover plates were thin plywood. Because the cover plates over hung the pattern, they largely confined the clips to the space between the mounting board and the cover plate.

Second, I was very careful to always use a climbing cut as I went around the pattern. That is going clock wise on the out side cuts and counter clockwise on the inside cuts.

Third, if I had mounted the patterns inside a box, put sides on the board that I mounted the patterns, and had the cover plates extend to the edge of the boards, the chips would have been a contained way better than they were.

Yes, there are some chips that do come out the slot for the router bit, but that is way better than what the case would be if the cover plate did not cover the pattern as I had it. That would be a cover plate that was just the image of the pattern.

I used a 2 flute 3/8 flush trimming router bit, smaller is better. Keeping the bearing at the bottom of the bit well lubricated is a must. I lost the first bit when the bearing failed.

Hope this helps. I do not guarantee that you wont find chips in you under ware.

[fairchild]

Thanks SL--- Thats a neat idea you had. i may try that - making a frame maybe out of 2 by 6 on edge and put clear plexiglass on the top so I can see whats
going on. Just need a way to connect the frame and the sandwitch. That shouldnt be to hard.
Id like to use a 1/4 inch cutter as it would exert less forces on the work.-
Did you have to oil the bearing periodically while cutting ? Like every half hour of use ?
Fortunately im not afraid of chips. It couldnt be as bad as an angle grinder when the stream of red hot sparks are going on your cheek !
T

[Glenn Patterson]

I made a template for the rib to be cut & then sandwiched a second piece of MDF to it the routered it to match together. The sandwich was held together with no.10 (3/16) screws & wing nuts. The hole locations on the rib were determined for our master wing form template. I built a router table with interchangeable inserts so I can use either of my routers. I like table better as I can see what I am doing. I found the best cutting router bits were 1/2" flush cut with bearings. I bought a tad longer quality bits from Lee valley tools and the bits cut all the MDF & aluminum for the project. The 1/4" bit cutting edges runs hotter than the 1/2". It makes it easy to put the work on the table and run it against the router bit. I put big direction arrows on the table so I know the feed direction from either side of the bit, I found it reasonable to do about 3 pcs at a time but there is less chatter with one or 2 pcs. I bought a $30 foot pedal switch for the router so I can stay safe and if pieces fly which they may the router goes off when I step back. It is easy to switch on an off to clear the waste and ships. We fly cut our holes on the drill press. We added a plywood word surface to the drill press table so it is easy to clamp some scraps to stop the work from spinning. The fly cutter works good in the drill press if a person use safe work practices.The holes were cut undersize and finished with the router.

I do some wood work so this was my excuse to buy a 3.5 hp Hitachi varispeed plunge router that I mounted in my table. They were on sale and reasonable at the time. I am more than happy with that purchase. I could have got away with my smaller Craftsman. I built a router table that has a top that is about 24 x 30 that has been my work horse for 25+ years. The surface is large and makes it easy to run the wing rib templates.\

Eye protection and good hearing protection ear muffs. The ear muffs are a must for all the wing construction activities.

I posted a write up on how to make all the tool & die for the ribs with just a router about 4 years ago. It is one man's way and it is more information on the journey to create your system.

https://bearhawkforums.com/forum/too...hawk-jigs-dies

Glenn