Spar Preperation

[av8shar]

Mine were actually only 12' long. They are two EAA spec work benches end-to-end longitudinally, so 2'x12' total.

Twelve feet was just enough without an extra support if you work it right. Basically one squeezer position at the extreme end of the bench and one in the middle, then shifting between the two as you move the spar through the process. I didn't get if perfected until the second one. On the first I used a step on a ladder for off bench support.

Tony is right that only two feet wide works out very well doing the spars and especially when I used the SPA squeezer. You can place the squeezer bracket in the middle of the bench (one foot on each side) and flip the spar over to do the top and bottom rivets in small sections as you work your way down the spar. The narrow bench also allows you to switch sides back and forth to monitor the shop head side (or whichever side you choose) as you flip the spar back and forth. That's why having the SPA squeezer cylinder on a hose so you can move it around is so nice.

Andy

[Tony Spicer]

Yep, it sure is. Mine was 4' x 14'. Too wide:

https://picasaweb.google.com/tonyboytoo ... 2772492802

Andy Shorter was smarter. Looks like his is 2' x 16'.

https://picasaweb.google.com/1078143629 ... 5182827506

Problem with a 4' table is you're forced to work from just one side.

Tony

[at7000ft]

Talking about spars, concerning the wing spars, is a 16' x 4' work table long enough to build these?

Rick H

[Tony Spicer]

Glen,

Here's a shot of the tools that will come in handy. It was hidden away in the wing spar Picasa album.

https://picasaweb.google.com/tonyboytoo ... 0261556098

The non-woven disks at HF work just fine. The cheap die grinders do not, as they just don't have enough torque to do the job. Best to borrow a good one, or spend the money and add one to your collection.

Tony

[GlenNJ]

Thanks Paul and Sean. Looks like I'll be heading to Harbor Freight to get some tools. Thanks for the picture Sean. That's a nice finish on your spar. I'll try to duplicate it.

Glen

[Seansull]

Hi Glen,

I found tapered sanding cones on a mandrel the most time efficient way to initially smooth out the tooling marks. I buy these in bulk at harbor freight, about $25 for 30 or so. After I smooth all of the marks, I come back with the scotchbrite wheel to polish up the edges.

Here is a close up of the finished product...

Hope this helps!

[psalter]

Glen,

It is always best to have a smooth surface. Small nicks and scratches can be "stress risers" especially in high stress areas, might be sources of cracks later in life. However, it is rare to have a perfectly smooth surface, typically on military aircraft we blend the area out about 10 to 1, or 10 times wider than it is deep.

One of items I like to use is a right angle air die grinder with a green scotch bright disk on it. The scotch bright pad is just enough to smooth, but not to aggressive. Like this http://www.harborfreight.com/complete-s ... 43029.html or http://www.harborfreight.com/pack-of-5- ... 99985.html. They can also be used with a drill, but that can be awkward, It leaves a nice polished edge, and can get into the large interior areas like you show. Tighter radius's are harder, use the largest radius drum you can fit, or emery paper. Small radius drums like you said can be hard to get a smooth surface.

[GlenNJ]

I'm preparing the .1875" spar doubles on my horizontal stabilizer for assembly. The edges are pretty smooth, but there is a slight ripple effect, left by the machining process. Do these surfaces have to be made perfectly smooth? I watched a EAA instructional video, and they imply that all surfaces must be smooth. On the front spar, I used a Vixon file on the outside edges, and is was pretty easy to get a smooth surface. The inside edges were another story. I spent hours getting nice edges, on one spar. Is there a quicker way to dress these edges. I tried a dremel tool with a small sanding drum attachment. It worked, but had a tendency to hop, and I had to be careful to keep it from digging in. I had more success, with a small file, then using 50 grit, to 120 grit sandpaper, and finishing with emery cloth.

Glen