They're called your Gluteus Maximus muscles. They're much larger in humans than in other primates because we walk upright instead of on all fours, and the "glutes" help hold us upright.

http://en.wikipedia.org/wiki/Gluteus_maximus_muscle

do you guys use these wing rods on steroids for all your builds? seems like over kill for i can barely flex this rod with my bare hands and im in construction,,,,seems to me the nylon bolts would shear/pull out or the blocking for bolts would pull out b4 the wing folded up...or am i being nieve. ill order it and one for the ollyIIs im waiting for if replacing the is rod the norm. just asking
jeff

Depends on the plane. The wing rod has to be strong enugh for the loads applied to it. For an open class airplane that has to be tolerant of winch launching, that means being able to handle about 300 pounds of winch line tension.

That means each wing is carrying about 150 pounds, centered about 40% of the way out from the root, so on a 10 ft. span airplane that's a bending moment at the root of about 3600 in-lbs. If you have a 1/2 inch diameter joiner, stress = Mc/I, where M is the moment, c is the distance from the neutral axis to the outermost fiber (so half the diameter, or 1/4" in this case), and I is the section modulus. For a round rod:

I = (Pi * D^4)/64 which in this case is 0.00307

Plugging all of that into our equation, we get:

stress = 3600 * .25 / .00307 = 293,000 PSI

which would require a hardened alloy steel with a hardness of about 55 Rc or better, which means heat-treated tool steel. Some of the ejector pins in the previous posts are that strong, some are not. Music wire, particularly piano wire, is that strong and hard (which is why it can put nice little dents in tool-steel diagonal cutters), but good luck trying to find some 1/2" piano wire!

If all you plan to do is high-start or electric, you can get away with less.

It all depends on what you plan to do. If you are going to apply a certain load to a part, then that part must be strong enough to handle that load.

Nylon bolts are incredibly strong in tension, but are designed to shear relatively easily, thus preventing damage to your wing. As for seeming like they would pull out of the mounting blocks with such a heavy load, somebody explained that to me once, but I can't remember how it goes. But basically, the load is the weight of the fuse on the wing times any g-load, or extra load imposed by a winch or hi-start. Not nearly enough to cause structural failure..... unless you really try!

Another Bird of Time emerges.

Just a bit over 40oz., too light I reckon. But I'm already thinking of ways to add ballast. Build info in Sailplane Talk, LISF BOT one-design thread.

It's a fun glider.

John

Hi John

Very clean build job i like your set in rudder and hindge pin , i put a set up like that on my Goose in the avatar pic works well and looks good too.

Don

John,

That really is a fantastic looking BOT! Love the fuse.

What a fuse! nice to see originality.

She looks a peach.

Thanks you guys. I've only got a few flights so far, still getting the feel of it.

Don, I've always liked the hinge pin idea too. Rudder removal is very easy as well.

John

John,

I like the rudder hinge setup too. I use pins too but can you elaborate on the retention system? I can't tell in the photo but is the retainer soldered into the tail skid? I just can't make out the details. Probably my eyes ain't what they used to be.

Hey Sean,

Here ya go, these pictures may help. I flattened a short piece of alum tube, wire hinge has a folded-over prong that inserts. It has lots of friction, but I dabbed on a bit of glue for peace of mind.

The skid wire inserts into a seperate nylon tube. It's held in place w/ friction too. The top rudder pin is glued into the fin, shaped like an inverted 'U'.

Hope this helps.

John

Ahhhhh! Got it! Thanks John! I shall now steal that idea on my next project.

What keeps the U-shaped pin from wagging side-to-side around its forward end?

Sean,

I've also 'borrowed' ideas from others too, and these threads always have good tidbits, if not just entertaining.

I mess around with WW1 scale stuff, and this quote applies there big time, but perhaps with most areas of this hobby:

"Stealing from one is plagiarism, stealing from many is research." anon

John

Originally Posted by Don Stackhouse

What keeps the U-shaped pin from wagging side-to-side around its forward end?

Hi Don,
The flattened alum tube keys the prong into position. The fit is quite snug.

If you meant the top pin..the top 'U' pin inserts about 3/4" into the fin and is epoxied in place. Part of the 'U' is also bonded to the tip of the fin.

John