Rib Form Blocks

[markcr]

I've seen several posts and YouTube videos where people are making two separate rib form blocks, a left and right. Sorry for the newbie question but couldn't you just use the same rib form block and just bend from the other side for the opposite rib flange direction? I plan to cut out the lightning holes with a router and then use a Bob stick to bend the 30 degree flanges.

[BTAZ]

I made a single form block(double thick) and used both sides. Just used MDF and coated the edges with epoxy.

If you make two form blocks, you may be able to bevel them to allow for spring back(in particular if you are going to put the flutes into the form block and form them as you go; you can find videos of this technique). Note for flanging the lightening holes, I used the "Rubber press method" and it worked great with little resulting distortion of the ribs.

Hard to believe that I finished the wings a year ago. You can see my build log in this PDF. https://www.dropbox.com/s/xkt9a5ro3x...wings.pdf?dl=0

Note this is a big file so it takes a while to load

[markcr]

Thanks! Yep, I downloaded your pdf file yesterday but have only started going through it this evening. Great stuff! I'm going to have to put in an order with Aircraft Spruce to get my rib material. Shipping is a killer. It doesn't matter weather I order a single sheet of 4x8 2024 T3 .020 or 10 sheets. They want $164 dollars shipping. I might try and figure out all of my ribs and spar materials and order all that together since I have to pay the same shipping either way. How do you deal with ordering materials? Here in Northern California, I don't have many resources for aircraft grade aluminum. Aircraft Spruce seems to be the only outlet out on the west coast. There are a lot of metal dealers closer but none that carry 2024.

[BTAZ]

Regarding shipping, if you let them roll it it will go down.

Almost all of mine was shipped rolled. The exception was the material for the spars and that was because I was going to have to pay a truck shipment anyway for the cap strips.

[sjt]

Somewhere on this forum is a cut sheet made by X'N. Using a hand shear I got a little more out of the sheets then was in his layout. I then promptly screwed up and came out even.

I am working on a bearhawk patrol. You should check if this looks right.

1 sheet 03-27840 2024T3 ALUM SHEET .020 4'X4'
2 sheet 03-28020 2024T3 ALUM SHEET .032 4'X8'
3 sheet ALCLAD/PVC 03-27910 2024T3 ALUM SHEET.025 4'X12'
1 SHEET ALCLAD/PVC 03-28010 2024T3 ALUM SHEET .032 4'X12'


I had the above rolled. The only thing that can not be rolled is material for the cap strips. That material can be purchased in the future. Also, the wing skin is ordered in the future. Order the wing skin in 4x12 foot lengths.

[markcr]

Good information. I didn't see a place on Aircraft Spruce's online order form where you could specify rolling the sheets. I'll call my order in. I'll go through the plans tonight after work and get my materials list finalized. I'm fairly certain that the majority of the ribs on the LSA are .020. I'll double check, though. Another question regarding the MDF rib form block is how you cut the lightening holes in the MDF? Hole saw or fly cutter? Just curious. I couldn't find a fly cutter at Home Depot but they sell many sizes of hole saws - pretty expensive, though.

[sjt]

Most of the ribs on a patrol are 025. A few of them are 032. The spar is 032. You might need a similar arrangement of sheets just different gauge for the LSA. I used a fly cutter with my drill press going as slow as possible. It is a dangerous operation - you are always tempted to reach in and brush away dust as it goes around.

Somewhere I got hold of a fly cutter that could span the diameter. I am not sure about the ones at home depot.

Amazon is one of the hot spots for odd stuff. I am not sure if this will work for you

http://www.amazon.com/General-Tools-Instruments-55-Circle/dp/B00004T7P1/ref=pd_sim_469_1?ie=UTF8&refRID=1G2TY28EMSEGYCCEMQHW&dpID=41VMXNN02SL&dpSrc=sims&preST=_AC_UL160_SR160%2C160_

When you drill a pilot hole thru your mdf template it has to go thru a sacrificial board bellow. Then pull out the drill bit from the fly cutter and replace it with a drill rod shaft of the same diameter.
Your drill rod shaft must be inside the sacrificial board before the cutter contacts your mdf. The sacrificial board has to be clamped down to the drill press table. None of this will work without a drill press.

[Bcone1381]

This post below has a document that shows a great technique for making all the jigs and flanging dies.

http://bearhawkforums.com/forum/tools-technics-and-best-practices/233-routering-methods-for-bearhawk-jigs-dies