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jonbakerok
10-13-2008, 07:34 AM
My '91 vintage M4 kit is missing the wood (spruce?) fuse stringers. The factory can provide aluminum stringers like what the current kits use, but I'd have to pay truck shipping because they're 10' and the UPS limit is 8'.

I decided to see if I could find something local to make wood stringers, but I'm not having much luck. Spruce is obviously out of the question, but apparently so is douglas fir. The best I can do is 3/8 x 5/8 rectangular molding stock in either yellow pine or oak. The pine seems too flimsy and the oak seems too heavy.

So I got to thinking, why couldn't I just splice aluminum stringers? ACS sells aluminum rectangular tubing stringer material. I could make some plugs from hardware store aluminum bar stock, which should make the splices the strongest part, but I'm not sure. Also, since the edge is not very rounded, I'm afraid my fuse might look funny.

What do you think? Spliced aluminum or pine or oak? Any other ideas?

DanB
10-13-2008, 08:31 AM
Jon, I feel your pain :>(
I had to replace mine when I did the wide body Mod. I ran into some of the same issues. I opted away from the pine as you already mentioned...not strong enough. It would really be a pain if one of those broke after covering & painting.
I went with the oak. I found a piece long enough (and straight grained enough) at the local hardwood supply which came 3/4" thick and maybe 4" wide. I believe I ripped a couple pieces to 1/2" (whatever the stringer forks accept) then took a 1/4" round-over bit and rounded the outside edges. Some sanding and a couple coats of epoxy varnish and they turned out good.
As far as your thoughts on the aluminum stringer...I would have the same concerns if the outside edge was on the square side.

kmul
10-13-2008, 10:07 AM
the aluminum stringer that came with my ss is .5x.028. you could order that in 8 ft lengths from acs. also order a short length of .5x.058. find someone with a lathe to turn that length down so it fits snug inside the .028 pieces. that would make a nice splice to blind rivet together and the additional weight would be minimal. after all its not structural and ups could deliver it. how much more is truck freight anyway.

jdmcbean
10-14-2008, 04:12 PM
Jon, We could cut them down to 8' as well... I'm not sure but "what-if" ou squeezed the tubing to fit into the side tabs.. I would have to try it but it may work out fine.

jonbakerok
10-15-2008, 04:53 AM
John, I'm not sure what you mean by squeezing the tubing. Do you mean that the stringers you have are thicker than the mounting forks on my M4? My forks are 3/8" and the ACS tubing is 5/16", so I figured it was close enough. What thickness are your stringers? If they'll work and they're rounded, I'd rather use yours. Here's what the ACS stringers look like (they're not very rounded):

http://www.aircraftspruce.com/menus/me/aluminum_rectangularstringers.html

ACS also has spruce T-stringers with a rounded edge. They're a little skinny, though, at 9/32, and I'm not as confident about splicing wood.

http://www.aircraftspruce.com/catalog/wppages/tstringer.php

jdmcbean
10-15-2008, 09:26 AM
Jon,
What I was referring to was round tubing... Looking closer at it I would consider 1 of 2 ideas...

1 trim the mounts on the fuselage back slightly.. about .188 and use a .375 dia aluminum round tubing.. This would most likely be my choice.. it would be real easy to do.

2 Use .438 dia aluminum round tubing and where it mounts to the fuselage simply sqeeze the aluminum tubing so that it fits in the .375 mount. I tried it with .500 dia tubing but it is just too much of a bump after it is sqeezed and wouldn't look right.. .438 may work great... but I didn't have any .438 to work with.