non-alclad spacer

prkaye · #1 01-28-2008, 08:09 AM

I may get flamed for this, but...
I'm ready to rivet my aft deck down, but for one of the spacers that goes between the angle at the top of one of the bulkheads and the aft deck (the 9.28" x 1" spacer) I ran out of AS3-125 (I previously used this piece for something else).
Now, I have a piece of non-aircraft alum angle that is the right thickness, and i could cut a strip off this, prime it and use it for my spacer. I don't believe it is Alclad. Would this be extremely foolish? the other option of course is to order a new part from vans, but living in Canada this means a $40 customs brokerage fee for a $4 part, or else waiting 3 weeks for the little spacer - I don't want to start working on skins until I have the aft deck riveted in place, since it is what keeps the fuse from twisting.
Thoughts?

SvingenB · #2 01-28-2008, 10:27 AM

I know how you feel

40$ and three weeks for a piece of metal worth a couple of dollars is just plain wrong. It is best to ask Van's. IMO alclad or not make no difference, just prime it. It is the strength that matters. Non-aircraft aluminum could be any kind of alloy, but is more often than not of much lesser strength than "aircraft grade".

2024 is almost twice as strong as the 3xxx series that is most often used in buildings and so on. 2024 is also 1/3 stronger than 6061 that most extrutions are made of. I don't know if Van's use the 7xxx series (spars?), but that is 1/3 stronger than 2024.

prkaye · #3 01-28-2008, 10:42 AM

Thanks for your reply... i was beginning to wonder if my suggestion to use non-alclad was so horrific that nobody could bring themselves to comment!

For a spacer such as this, I don't think it is under much load and strength shouldn't really be a major factor. I was only concerned that a non-alclad bit of metal in there might start some corrosion, but if i'm generous with the primer maybe I'm worrying about nothign.

Ted Johns · #4 01-28-2008, 02:26 PM

Remember, most aluminum doesn't need to be alclad for excellent corrosion resistance. 2024 AL needs it because the copper alloyed in with the aluminum in this alloy greatly reduces corrosion resistance. If you know the alloy you're working with, google will quickly tell you how much trouble to expect.

rwtalbot · #5 01-28-2008, 08:27 PM

Quote:

Originally Posted by prkaye

Now, I have a piece of non-aircraft alum angle that is the right thickness, and i could cut a strip off this, prime it and use it for my spacer. I don't believe it is Alclad. Would this be extremely foolish?

Phil, I would not say this is foolish, but what is the consequence of a failure in this area? If I understand correctly, you are talking about the area that supports the HS being bolted to the fuselage? The spacers that sit under the bolts? This is one of the most highly stressed parts of the airframe. You might get away with it, but this strikes me as structural in nature. i.e., we are not talking about a couple of drink containers being attached to the fuselage wall. There are serious consequences if a failure occurs here. Are you happy with the solution and do you believe anyone else riding in the plane/purchasing it later would be happy with the risk?

I would personally do it right. Make sure that the materials are aircraft grade and the appropriate alloy.

If in doubt, ask Van, but don't take my advice or anyone else's. I am not an aircraft engineer. I trust in the designer and believe that if I follow his instructions properly I will have a safe and functional airplane. There are certainly other ways to do it, but that works for me.

Richard
RV7A Finishing

rv8ch · #6 01-29-2008, 01:15 PM

There's gotta be a half dozen builders in a city the size of Ottawa, perhaps one will lend you a bit of metal? At least you can piggy back on one of someone else's orders to Van's. You're going to need more stuff from Van's soon one way or the other!

Jeff R · #7 01-29-2008, 07:52 PM

No reason to get flamed! Excellent question.

I would ask Van's, but I would think that if it is the right thickness and you prime it well, it ought to be fine.

fmarino1976 · #8 01-29-2008, 08:42 PM

Since I haven't started working on a kit yet, I can't picture exactly where the part is going, but If I understand this right, this part will be used as an spacer sandwiched between two aircraft quality parts. Are the parts fastened with rivets or bolts? How much torque on the bolts that fastens the assembly? I bet no where close enough to deform or otherwise damage the non-aviation aluminum spacer. Strength is not the issue here, since the spacer is not under any kind of structural stress beyond some compression, but since corrosion "COULD" be a problem on this part. I would alodine it to give it a protective conversion coating, and maybe prime it after that just for good measure.

I would have no problem using this part as described, I don't see a safety issue here. After saying that, I'll have to add a DISCLAIMER: this is in no way, shape, or form anything other than my opinion on this issue.

Good luck on whichever way you choose to go.

rv9builder · #9 01-30-2008, 01:28 AM

Perhaps you could find a small piece of 2024 that is the right thickness from a local metal supply house. They would probably sell it to you for a dollar or two.