Hor. Stab spar reinforcement question

[STINGRAY]

I'm filing the reinforcement bars (609PP) and wonder how much grinding/filing is permissable. Every time I turn around I find more scratches that need to be removed.
Van says all scratches need to be removed and finish should be that of a satin finish produced with 400grit wet/dry. I do have a couple of scuffs that will require a fair amount of grinding. Any thoughts you'd care to share? I put a mic on it and They are .187 thickness,

Tony

 

[mikeangiulo]

there shouldn't be any marks that are deeper than tooling mark scratches. I took them all out with a single cut file and scotchbrite. If you think you're actually changing the shape or dimensions of the part yours might be damaged. Do you have a picture?

 

[Transporter]

Spar Reinforcement

I remove rough edges on long parts like the 609PP by clamping the part on edge (lengthwise), followed by draw-filing the edge. Pad the jaws of your vice /workmate/etc. so you don't add scratches in the process.

You don't need to go overboard with the filing, just enough to get rid of the punch/tooling marks. Five to ten strokes with the file is usually enough to do the job.

On shorter parts I use 3M rubber sanding blocks (from Lowe's) with various grits of emery cloth/aluminum oxide sandpaper instead of the file.

Emery cloth/sandpaper wrapped around a dowel helps smooth the inside radius of any curved parts.

Filing is followed by a polishing using a 2" Scotchbrite wheel mounted on an air grinder. The wheel will quickly wear a groove since it's softer than the aluminum part. I use the groove in the wheel to round the edges as described in section 5B of the plans.

I remove any small scratches using a maroon Scotchbrite pad. This last step gives a nice satin finish and the part is ready for prep/priming.

About five minutes per side of a long part like the 609PP gets it done.

I also have a 1" Delta strip sander that does a great job removing tooling marks, but you can do the job without it using the hand method described above.

Hope this helps,

Mike

 

[STINGRAY]

Thanks

Thanks for the replies guys. I think I was being a little over concerned. I continued working the reinforcement bars and they are looking pretty good. Gad, this is fun! It is so nice to have a 2 days in a row with nothing to do but work on the emp.