JGlassFNPJuly 20, 2019, 3:01pm
DO any minimax wings require rib stitching the fabric?
Building and Flying Related Boards › miniMax, Hi-Max, and AirBike General Discussions
Rib Stitching
16 posts
texasbuzzardJuly 20, 2019, 6:39pm
Many including mine did not have rib stitching since the airspeed of the max doesn’t justify it.
IMHO
Monte
IMHO
Monte
mullacharjakJuly 20, 2019, 7:02pm
Construction manual Page 3 says if using larger engines or operating outside the ultralight category then rib stitching is recommended.
ITman496July 20, 2019, 8:21pm
What airspeed starts to make rib stitching a requirement? I have an engine that is a bit larger then the 277 recommended..
JGlassFNPJuly 20, 2019, 8:23pm
Thanks mine plans says you may if you choose so I was getting input as this is my first build. I appreciate info.
mullacharjakJuly 21, 2019, 6:08am
A 3/4 wide ply rib capstrip on top and bottom would increase glue area three fold.Dont know if anyone used this idea on minimax.
Aeromodellers use this method often. It will also eliminate the step at the leading edge sheeting which nobody talks about.The thing to be seen is whether there is any weight penalty or not.
Aeromodellers use this method often. It will also eliminate the step at the leading edge sheeting which nobody talks about.The thing to be seen is whether there is any weight penalty or not.
TomJuly 21, 2019, 11:57am
I think this is an area where an extended, really scientifically valid, series of tests would be highly desirable to see what today's glues will allow. However since most of us aren't going to take the time to do that, I would certainly rib stitch on anything that wasn't a true ultralight. Personally I guess I'd rib stitch on the ultralight as well, and I'm a person with an awful lot of experience with glued structures.
Tom
Tom
ulbuilderJuly 27, 2019, 12:11am
A few maxes have had partial separation of the wing trailing edge. Rib stitches might save a life should a complete separation ever occur.
More info and informative videos can be found on my blog:
https://ulbuilder.wordpress.com/2016/07/25/rib-stitching/
More info and informative videos can be found on my blog:
https://ulbuilder.wordpress.com/2016/07/25/rib-stitching/
ITman496July 27, 2019, 1:00am
My plane's trailing edge separated a bit just sitting around, and I have to redo it and reinforce it.
ITman496July 27, 2019, 8:06pm
The fabric isnt separating from my trailing edge, more like the trailing edge wood has separated from the ribs where it mounds, strangely enough. I was going to glue and sew the whole thing back together on each rib with carbon fiber tow and epoxy.
texasbuzzardJuly 27, 2019, 8:47pm
Did the same on my air bike. The fix is to to add 1/4 in wood blocks to each side of the ribs using t-88 epoxy. I used clamps to bring the te down to the ribs while the epoxy dried. This will give the te a 3/4 in glueing surface. After a year no signs of lifting.
Monte
Monte
ITman496July 27, 2019, 10:17pm
Hmm, that does sound way easier. I'll do that instead! I can laser cut out a bunch of blocks, would save me a lot of time.
texasbuzzardJuly 27, 2019, 11:25pm
Keith103July 29, 2019, 11:31pm
I guess the likely point of separation of the fabric ( if at all ) in a wing like we have in MiniMax, may be at the trailing edge where it is wrapped around the RS 17. The fabric is unlikely to lift off the rib if the front and rear edges hold securely.
The leading edge has plenty of adhesion around the nose-ply and a 2 inch overlap to the fabric from the other side. With this much of glue contact area up-front, it is difficult to foresee the fabric lifting up from the front. Even the lateral edges have plenty of adhesion on the 1/8 plywood on the tip ribs.
I focused on the likely weak spot at the trailing edge, and I increased area of fabric contact by cutting the fabric on the trailing edge 1 inch broader than what plans call for. I tucked that excess fabric into the inside of the wing's fabric to give a glue-contact width of 2.5 inches all along the trailing edge. May be unnecessary some might say.
Also I rib stitched only the rear end of each rib beginning from the rear spar and going backwards till the trailing edge. I did this to make it almost impossible for the fabric to lift from the trailing edge. Stitching behind the rear spar is easy because you have full access to the inside of the wing at this location.
Just another point which I felt may have a bearing on fabric lifting off from the trailing edge. I did not over-stretch the wing fabric while heat-shrinking. Shrinking too much tends to lift the rear RS 17, and may be one of the causes why the fabric lifts from the rear. ( just guessing. I have no scientific data to back this up. )
I am not suggesting what I did is ideal. Just adding to this discussion, FWIW.
The leading edge has plenty of adhesion around the nose-ply and a 2 inch overlap to the fabric from the other side. With this much of glue contact area up-front, it is difficult to foresee the fabric lifting up from the front. Even the lateral edges have plenty of adhesion on the 1/8 plywood on the tip ribs.
I focused on the likely weak spot at the trailing edge, and I increased area of fabric contact by cutting the fabric on the trailing edge 1 inch broader than what plans call for. I tucked that excess fabric into the inside of the wing's fabric to give a glue-contact width of 2.5 inches all along the trailing edge. May be unnecessary some might say.
Also I rib stitched only the rear end of each rib beginning from the rear spar and going backwards till the trailing edge. I did this to make it almost impossible for the fabric to lift from the trailing edge. Stitching behind the rear spar is easy because you have full access to the inside of the wing at this location.
Just another point which I felt may have a bearing on fabric lifting off from the trailing edge. I did not over-stretch the wing fabric while heat-shrinking. Shrinking too much tends to lift the rear RS 17, and may be one of the causes why the fabric lifts from the rear. ( just guessing. I have no scientific data to back this up. )
I am not suggesting what I did is ideal. Just adding to this discussion, FWIW.
mullacharjakJuly 30, 2019, 6:05am
Just a thought.The fabric can also be stitched to the RS 17 as if it were a Riib.
beragoobruceJuly 30, 2019, 7:11am
Quoted from texasbuzzard https://youtu.be/k7riI8Z4zkE
Here is a video of the repair
Monte
The other way (if you're still building, too hard as a retrofit) is to close off the rear spar with a 1mm panel. Supports the trailing edge & stops mud wasps getting into the wing.
