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#1
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Airframe finishing and tooling
Hello again and thanks to everyone who gave suggestions on my search
for which aircraft to build. My shop is ready and I'm buying materials this week to kick things off. I've got some questions on how to properly prepare and work with the aluminum I use in constructing my plane. First: I know I need to sand/finish the cuts and holes I make on the 6061-T6 stock I use. The question is to what level. I know rough edges are points of stress and should be removed. The question is what is considered "rough?" Like to what grit size sandpaper to work my way up to? Steel wool at the end? I ask because the thousands of tiny scratches that even fine sandpaper leaves could still be called a rough edge in some context. Second: From what I read - the aluminum I use will be anodized which is a process I know a little about - enough to know that any place it gets drilled or cut will leave an un-anodized surface exposed to the elements. What is the "Proper" way to protect these places? If it matters - my plane will be stored in North Florida approximately 20 miles from the ocean so there won't be constant salt-spray involved, but I do envision flights along the beach etc and I also have a large fresh-water lake near my house that would make a great airport for my eventually pontoon-equipped plane. Lastly: What is the 'ideal' 3/8" drill bit and cutting lube to use for drilling 6061-T6 in .125" plate and 2" square x .125" tubing? There are only a few sizes that I'll be using on this project so I'm interested in a "cost is no object" brand/type that would be best. |
#2
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Airframe finishing and tooling
On 22 May 2006 07:01:44 -0700, "nondem" wrote:
First: I know I need to sand/finish the cuts and holes I make on the 6061-T6 stock I use. The question is to what level. I know rough edges are points of stress and should be removed. The question is what is considered "rough?" Like to what grit size sandpaper to work my way up to? Steel wool at the end? I ask because the thousands of tiny scratches that even fine sandpaper leaves could still be called a rough edge in some context. In MY opinion, a fine file and a radiused edge. Depending on the thickness, the hand deburring tools leave GREAT finishes. Second: From what I read - the aluminum I use will be anodized which is a process I know a little about - enough to know that any place it gets drilled or cut will leave an un-anodized surface exposed to the elements. What is the "Proper" way to protect these places? Anodizing is a great non-structural finish. When it cracks, and it is brittle, those tiny scratches you mention above are mild in comparison. I don't like to anodize for structural appliations. Definitely do not "hard cote" or hard anodize; the thickness really will cause stress risers in whatever cracks occur. Lastly: What is the 'ideal' 3/8" drill bit and cutting lube to use for drilling 6061-T6 in .125" plate and 2" square x .125" tubing? There are only a few sizes that I'll be using on this project so I'm interested in a "cost is no object" brand/type that would be best. There will be some who laugh here, but if you are rigid (stiff drill press or mill), I like solid carbide, positive rake, at HIGH speeds. I did some work some years back at 4000 rpm, 1/2" diameter, power feed to pull a 0.003" or 0.005" chip per tooth. At your thickness, no lube is required. We used high velocity air as the coolant on drill-mill applications. Watching the table move was scary; note that we were making 8000 cuts (0.005") per minute, so 40 inch per minute feed. We'd have been through your plate in less than a quarter-second. At lower speeds and feeds, our prototype shop machinist loved to spray isopropal alcholol as the coolant/lube. I was surprised it worked as well as it did; he gave glass-smooth finishes, as did the production tooling above. Note: CHIPS FLY!. |
#3
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Airframe finishing and tooling
Thanks for the info - I just realized I was wrong thinking the 6061-T6
came already anodized. I've been reading so many specifications I got them mixed up. I won't be anodizing.... |
#4
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Airframe finishing and tooling
In article . com,
"nondem" wrote: Thanks for the info - I just realized I was wrong thinking the 6061-T6 came already anodized. I've been reading so many specifications I got them mixed up. I won't be anodizing.... Do NOT use steel wool on aluminum! It will leave tiny bits of steel embedded in the surface and will induce electrolytic corrosion! Why 6061? Most aircraft sheet metal is 2024 T-3 Alclad; structural is 2024 T-3 plate. |
#5
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Airframe finishing and tooling
The plane design I'm building uses 2x2x.125" 6061-T6 for the fuselage
frame. I did notice that older versions of the same plans specified 6063-T351. I checked the specs on both and as I remember the 6061 is a stronger alloy. There is almost no aluminum sheet used in this design either...Just angles/square and round tubing for the most part. |
#6
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Airframe finishing and tooling
nondem wrote:
The plane design I'm building uses 2x2x.125" 6061-T6 for the fuselage frame. I did notice that older versions of the same plans specified 6063-T351. I checked the specs on both and as I remember the 6061 is a stronger alloy. There is almost no aluminum sheet used in this design either...Just angles/square and round tubing for the most part. That sounds a lot like one of the late Graham Lee's UL designs. Close? Richard |
#7
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Airframe finishing and tooling
It's an Affordaplane...
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#8
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Airframe finishing and tooling
"nondem" wrote in message ups.com... It's an Affordaplane... Short for VaporWare. See any fly at national flyins yet? -- Jim in NC |
#9
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Airframe finishing and tooling
"Morgans" wrote:
"nondem" wrote in message ups.com... It's an Affordaplane... Short for VaporWare. When nondem first mentioned it, I did a Google search for it. There is a web site for it, even has pictures showing the ultralight in the air: http://affordaplane.com/ |
#10
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Airframe finishing and tooling
Yea, I just laid out the fuselage so I'll be at next years fly-in
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