How strong is a 6mm (about 1/4") nylon bolt?

I am a bit reluctant to use these in a 10 pound SU-26. I am afraid they won't hold up in high negative G maneuvers.
I'm thinking about installing alu bolts, but people say metal bolts tend to vibrate loose...

Am I being silly?

Uncouth:

Ten pounds is right on my limit for nylon. I use stainless screws, though, much easier to find than aluminum. Never had them come loose, but check them between flights anyway. Plain steel would be OK, but I like the looks of stainless.

My Ultra Stick 120 has four wing screws, I figure on a max of 16 G rating. That puts 60 lbs load on each of the four. IF the load were even front to back and side to side, the nylon would be fine. The loads are never even. Stainless steel.

When the wing screws break,
. Fuselage becomes a tomato stake.

Bill.

I'm thinking this way: when you fasten the screw, chances are there will already be a considerable load on them (you know, if you give them that half a turn too much)...

I want to know for sure, so I am just going to test them. Make some sort of setup so I can put weight on one...and see what they can hold. Maybe if I can find a heavy fishing scale (dynamometer in dutch, don't know the english term) I can work with a steel screw to put tension on them so all that dead weight has no chance of crushing my toes...

I think we all under estimate the strength of these bolts, but I won't take chances on loosing a plane on something stupid like that...

Mannerless Brat:

A device for measuring line tension is also "Dynamometer" in English.

Most people think of a dynamometer only as an engine power measuring device, but it means a lot more than that.

Your English is excellent, you are a good example to many of the people on this side of the pond.

I am curious about the failure point of the nylons also, but remember there are different grades of nylon, just as there are different grades of metal fasteners. Over here, the "White" ones are weakest, the black are the strongest. So tell us also, what color your test screws are.

Thanks.

When the wing falls off,
. Take a bow, hat, doff.

Bill.

ROFLMAO!!! Bill, I love your use of synonyms and rhymes!

Rudeboy, a 1/4-20 nylon bolt will have about 150 pounds tensile strength and 200 pound shear strength. On most of our planes, a 10-32 is more then ample (125 pounds tensile/150 pounds shear) and you could probably get by nicely with 8-32 (85 pounds tensile/ 40 pounds shear). I use at most 10-32 on all my big birds and have never had a failure yet. The figures quoted above are from test Weckesser Company made on type 6/6 nylon bolts. A good source for nylon bolts is MicroFastners, you can find them on the web.

Well that's what I meant with most people under estimating the strength of these modern plastics.

If the real purpose of using the nylon bolt is to "save" the wings, I think I've seen crashes enoughy top tell that it makes no difference. Weight savings over metal bolts, yes. Ample strength, haven't seen or heard one fail mid-flight yet...........

The purpose of my wing bolts is to hold my wing in place, period.

But like everyone else, I'm not looking to drag extra (unneeded) weight around.

If I can get by with nylon instead of metal, I will do so...

Shouldn't that be 40 pounds tensile and 85 shear...?

i use 1/4-20 Nylon bolts for all wing hold downs. I have always used them for the landing gear also till this last week. I have sheared off several on landing and didnt land that hard. The gear broke off each time wihtout damage to tail feathers as usually happens. i switched to steel, heavier but wont break. I doubt if any more damage occurs wiht steel thant nylon. Nylon deteriorates in the Ariozona sun if you ask me. Especially if the heads dont seat at the exact angle to the item being secured. Stressed heads just pop off and that was my trouble. I had installed a wedge and the heads tightened down securly but popped under stress with a 13 lb. airplane. My .02cents worth.

I always make sure the heads are seated properly, nylon or metal, it doesn't matter.

I will never put washers under a motor mount or engine mounting lug to adjust side- or downthrust...that's just looking for trouble.

The 1/4-20 nylon bolt is surprisingly very strong. My 11 pound plane spiraled into the ground once, with one wing tip hitting the ground first. Unfortunately, only one nylon wing bolt broke. As a result, the fuselage cracked near the other nylon bolt. Had both wing bolts snapped, then the fuselage would have been fine.

Yes, on 8-32 it is 85 pounds tensile, 40 pounds shear. On bolts larger than 8-32 the shear is larger than the tensile but on 8-32 down, tensile is larger than shear.