HS-908-L and HS-908-R

[llavalle]

Hi,

Long story short, I must redo one of the 2 ?L? brackets of the empennage of my -9(one of the angle rotated during drilling of the 2nd hole). Since the empennage kit does not come with enough material to make another one, I called my brother who works for a machine shop. He asked me for the material. So, here?s the first question:

1-What is the material? I assumed it was 6061-T6, and it was extruded (Part number AA6XXXX)... Contacted vans and they told me to order a replacement "AA6-187X2X2 1/2X5" and re-do it... AA6 angles are listed as "6061-T6 angles" on the webstore

He used a CNC to make the new angles. For some reasons, he used 7075 aluminum. Right now, it?s not heat treated, it?s a 7075-T0. He checked and he told me that bare 7075 has a tensile strength that is inferior to 6061-T6. He suggested we heat treat the 7075 to a T6... a 7075-T6 has more than 2x the tensile strength of 6061-T6 So, the other questions are:

2-Is 7075 BARE (T0) OK for this application? After all, 6061-T6 might have been chosen because it?s a lot cheaper compared to 7075.

If it?s not OK,

3-Is 7075-T6 ok for this application? I?ve read somewhere that 7075 is more brittle, but that was not a good source and it might not be accurate.

I?ve got 4 choices

1-Keep the 7075-T0
2-Heat treat the angle to a 7075-T6
3-Re-fabricate the angle with 6061-T6 no cost, the cnc program is made, put metal in CNC, hit the Start Button.
4-Re-order AA6-187x2x2 1/2X5 and re-fabricate... the part is only $5.96 but shipping, exchange rate + brokerage to canada will end up $20+ and waiting a couple of days.

What should I do? Asked Vans about it and they told me "We will not speculate on the 7075." What do you think?

Thanks

 

[rodcritt]

Save the Headache

For $20 why not just save yourself a headache and order a new part from Van's. You can move on to the VS while you wait.

 

[Steve]

Aluminum alloys

7075 is alloyed with much more zinc than 6061 making it harder to machine than 6061 but it is much stronger. The military uses lots of 7xxx aluminum. Ref this entry from wiki:

http://en.wikipedia.org/wiki/Aluminium_alloy

Steve

 

[llavalle]

7075 is alloyed with much more zinc than 6061 making it harder to machine than 6061 but it is much stronger.

Yeah, we knew that. It was harder to machine. It's also almost 3x the price of 6061.

My brother told me he was about to use 6061-T6 but his boss stepped in and told him "Hey, it's an airplane part, why don't you use 7075, it's way better and since you don't pay for it, you won't mind!"

What he did not realise is that the 7075 piece he had left was not heat-theated... it was used in a job where heat-treatment was done afterwards

I've just ordered the $5 angle from Vans

 

[BrentHumphreys]

I had to order a piece from Vans after I drilled the holes the wrong size. I ordered one extra long so I would have enough for a couple sets.

 

[Robert M]

I made two pair of these also. My mistake was deciding to build a second set based solely on how well they were shaped. Looking back - they would have been fine but I didn't like them.