Spar supports ?

[Tree top pilot 13]

I am nearing completion of both wings and fuse for the Ridge runner...making ready for the covering chores soon. I think I have asked this question prior to this post , but however I would like to get some opinions before I start adding weight.....unjustly. I know the Just aircraft wing spars as well as the Avid and Kitfox designs employ a length of extrusion to support the spars at the lift strut attach point to spread the load. My spars are 2 1/2" X .065" wall and are 141" long. Lift strut attach point at around 80" from root. Plans do not call for anything of the likes....MTOW will be very near 500 lds. I am not sure if the early single place Skyraider used anything either. Comments welcomed.

Pic is of my wingtip set-up....very light.

[dholly 718]

Just to clarify, the Avid Flyer models did not employ aluminum extruded spars or separate aluminum spar stiffener extrusions within the spars. They used plywood stiffeners, as did the first Avid Magnums. Later higher gross versions of the Magnum did go to the extruded stiffeners slid into the spar tubes. If you are interested, I put all the stiffener history in a thread title 'MTOW Modification' (or something to that effect) in the Fat Avid forum.

If your kit manufacturer does not require them and there are no reports of Ridge Runners falling out of the sky with bent spars, I sure wouldn't lose much sleep over the lack of stiffeners in your kit. If it bothers you, and you want to do something cheap, light and effective, just make up a set of ply spar stiffeners. The Avid Mk-IV uses 1/4" x 16" ply stiffeners, and my Avid+ came with 1/4" x 18" ply stiffeners. If you read through the above-mentioned thread, you will see that I started to make up some customized spar stiffeners for my Avid+ wings. I ultimately decided they were unnecessarily heavy and just added hardwood 'shoe molding' to the supplied 1/4" x 18" ply stiffeners. The original 1/4" x 18" Avid+ ply spar stiffeners weighed 4.2ozs each, my new stiffeners weighed 10.3ozs. each, for a total weight penalty of ~1-1/2lbs. total. I also added ply gussets between the drag and spar tubes and, while not shown in the pics, used any leftover Hysol as it became available to coat the gussets. Attached pics show all.

P.S. - I like the wingtips, reminds me of the Stewart STC tips for the clip wing pipers.

[Tree top pilot 13]

Thanks !!! I just couldn't leave the end rib as a finished product. Plus it will get me more effective wingspan. Not a bad bargain at a 1 ld. addition. One more for the going at it...I have made my trim tab on the elevator and have options at this point I think. A good cable or other means of deflecting it? I did weld tabs on it for a cable....but have heard they tend to break quite often. This is planned to be no electrics...with exception of the handheld TX/RX. I would like to be able to trim the stick off and have the backup of it.

Edited 8 May 2012 by Tree top pilot

[EDMO 1078]

My early Magnum manual shows 3 pieces of .090 ALUMINUM, 2 FEET LONG, riveted to form a "T", for the stiffener.

At first glance, I said, "500 MTOW shouldn't need stiffeners", but after thinking of the gust loads being greater stress on the ultralites than heavier planes, (Back to Barnaby Wainfain article on maneuvering speeds), then the inserts might be needed more on the lighter plane than the others?

However, I agree with Doug - if others haven't broke, then you are probably safe without them

Ed in MO

Edited 11 May 2012 by Ed In Missouri

[SuberAvid 617]

My early Magnum manual shows 3 pieces of .090 ALUMINUM, 2 FEET LONG, riveted to form a "T", for the stiffener.

At first glance, I said, "500 MTOW shouldn't need stiffeners", but after thinking of the gust loads being greater stress on the ultralites than heavier planes, (Back to Barnaby Wainfain article on maneuvering speeds), then the inserts might be needed more on the lighter plane than the others?

However, I agree with Doug - if others haven't broke, then you are probably safe without them

Ed in MO

Ed,

Do you have any details on the T construction and the rivet locations and size for making up the 3 lam aluminum stiffner?

Thanks,

Randy

[EDMO 1078]

Ed,

Do you have any details on the T construction and the rivet locations and size for making up the 3 lam aluminum stiffner?

Thanks,

Randy

I have the Magnum manual and Kitfox 1, 4, 5 manuals. All setting behind a freshly epoxied garage floor - will get to them by Monday.

Seems like the Kitfox insert was longer than the Avid - I will check all manuals and send what I find. I wonder if I would get into trouble by copying a page from the manual and sending or posting it. Dont want to be sued for copyright infringement........?

Ed in MO

[akflyer 1427]

I have the Magnum manual and Kitfox 1, 4, 5 manuals. All setting behind a freshly epoxied garage floor - will get to them by Monday.

Seems like the Kitfox insert was longer than the Avid - I will check all manuals and send what I find. I wonder if I would get into trouble by copying a page from the manual and sending or posting it. Dont want to be sued for copyright infringement........?

Ed in MO

Post it, it is for "educational" purposes not for sale.. I think your good! I posted up the PDF of the manuals here too.