Tying knots in Monofilament

[jakeluke]

I've run into a problem that I need help with. On the Grand that I'm building i have to attach one end of a piece of nylon monofilament to an eye already affixed to the bottom of the lower wing, and the other end to the top of my wheel carrier. It will be slack when I tie it in, but it has to support the weight and limit the downward travel of the wheel carrier when the plane is in flight. As such, it must be of a pre-determined length.

And then there are all the rigging lines, but at least those are tied between fixed anchors.

The only 2 knots I know of to use here is the one (clinch knot) that I used to use to tie fishing flies on to a leader, and the other is a pair of half hitches.

The clinch knot cannot be used under tension, nor can it be made to any precise length. I believe that in the monfilament I can pull the loose end and achieve a reasonably pre-determined length with the half hitch, but I'm wondering if anyone has a better idea?

[GrrrAmps]

I usually use a palomar knot when I tie rigging couplers, but they're almost impossible to get a predetermined length. Your best bet is probably a half hitch, but put a drop of CA on it when you're done to keep it from slipping. Otherwise, can you tie an eye on the end first, then screw it to the wheel carrier to take up the tension?

[jakeluke]

I might be able to use a threaded eye, I'm not sure. It's certainly worth taking a look at. It would have to be either 2-56 or 4-40 at most, but I suppose I could make up 4 such. Flattening one end of a threaded rod and then drilling a hole would probably work. Thanks!

[GordonTarling]

I'm not so sure you should be using monofilament at all for that job. That line will stretch under load, so making the 'precise' length somewhat variable. I'd be tempted to use nylon covered stainless fishing trace - it can't stretch and it's easy to make the ends off with a small crimp barrel.

[Dorsal]

Lots of knots = http://www.layhands.com/Knots/Index.htm
http://www.animatedknots.com

[gnats82]

jakeluke -

I use a loop formed and coming back through a small piece of tubing crimped tight on the loop, then ca. You can get the precise length and tension you want! Works with many kinds of strand material.

[staggerwing]

I'm not so sure you should be using monofilament at all for that job. That line will stretch under load, so making the 'precise' length somewhat variable. I'd be tempted to use nylon covered stainless fishing trace - it can't stretch and it's easy to make the ends off with a small crimp barrel.


Yes, if lines are functional on a large plane---don't use monofilament---you're asking for trouble---if only for esthetics, maybe OK but it will still look poor w/ time unless you are using turnbuckles for tightening

[GrrrAmps]

You're right, I didn't put two and two together about being for a large plane. Don't use mono if it''s functional. I used steel leader a bunch of times in the past, but more recently have been using kevlar braided spyder wire. 50 pound test is lightweight and has zero stretch. But you cant crimp it, you have to use fishing knots. I just finished up a 1/4 BUSA Pup with all Kevlar pull/pull and flying wires.

[gnats82]

GrrrAmps -

So, what's the story - why can't kevlar braided spyder wire be crimped? Help us out here...does the crimp slip or is it a breakage issue? Return looping through the crimp barrel would surely not slip...?

[GrrrAmps]

I tried crimping it a few times and couldn't keep it from slipping. I tried it the same way as wire, with a return loop and it still slips. It might just be that the crimp was too big, but it was the smallest crimp I could get three passes of the kevlar thru.

The downside of kevlar is that it is susceptible to abrasion. So I'll be keeping a close eye on the turnbuckle knots.