I know there are a few here who can relate

What follows 3 days of rain?
Monday!


Now I am stumped.  I have an FP20 ready to go, or I have to fart about with the LA25...

Over the weekend I had to sand down and glass the bell crank platform, still gonna need an extra couple washers to keep the bolt out of the wing.  I installed the wing saddle.  I last minute decided that the bell crank platform needed more reinforcing, so I put a layer of 24k carbon tow on the saddle which is epoxied to the bell crank platform.  

I got the elevator hinged today.  I went with stitching since I am irritated with all other hinging methods lately.  No blood was involved with today's efforts.

Jury is out on the cotter pin for a fairlead. Seems better than a safety pin at least.

Phil

The cotterpin looks pretty hideous. I like to use 1/8" landing gear strap. So the pushrod is not rubbing against the fuse directly, I glue a small piece of ply pretty much the outline of the gear strap.

Why not just a CF tube, it doesn't need any bracing.

I'm stumped. I COULD lace up some lead outs, since the everything is exposed I would probably run 65# power pro and not think twice. Some eyelets on the ends so I can use lines I already have

I understand that combat style lines run straight to the bell crank. How is the termination made so it can fit through the LO guide?

Phil

Phil, while photos are loading

I wanted adjust ability and did not like the wire push rod.   I used small diam CF tube with horn end a titanium insert with 4-40 threads and a dubro metal 4-40 clevis...assy is J&B welded together using some alum tube that fits OD ...you can wrap the ends with thread and CA to prevent any split of the CF tube instead of the outer tubing at the ends

Front at BC is part of the supplied metal wire and zee bend ( I could not make the double bend Phil C describes and shows) and inserted about 2 inches inside the CFtube

I used .27 stranded for the lead outs inside 1/8 copper at the BC with typical crimp connectors and eyelets

Not happy that I can't change line rake but fortunately it is good where it is for my engine, CG, weight, non stunt flying style

That ridiculous double bend took me 2 tries, one on each end of the wire. It really is needed to clear those odd looping connectors.

I will go with making LO's from the spectra on this one. Easy to do at least. I don't think I have any suitable wire or LO kits currently.

Phil

Phil, passing Spectra through those bushings is going to make a quick failure of your line. I fly with Phil on a regular basis and he will agree with me that the lines need to be flipped every few flights. We pull test every flight which is required but not everyone does this. We also use 100# test on our .25 size models. We have used 80# but have also seen failures. drill out the bellcrank and place a slider type line clip on the bellcrank ends. Tie your Spectra with about a 5/8 size loop on the end and pass that through your leadout guide and hook it onto the line clip. You can now remove it and flip the lines if chaffing is taking place. I no longer use those bushings and use ceramic eyelet guides for fishing rods. Just make certain that your line clips aren't jamming on the pushrod. This may require more washers under the bellcrank. For thicker bellcranks like Sig or Brodak, I use these,

I have 65# that I have been using.  I am not flying combat.  

What knot do you recommend?  There are not many loop knots that hold well in spectra.  A figure-8 is one that I know is stable, but I don't know how much it reduces line strength.   I will probably tie it doubled anyways.  (New England ropes rates the figure-8 around 60%, but that is not fish line, knot strength depends on the material and the knot )

I can order 100# if I really need to.

I have those clips. I already installed extra washers.

Phil

When Phill ties his proposed knot that was submitted to the AMA, the breaking strength of stainless .018 was the same as 100# test.  Your model only needs .015 to fly due to it's weight. Regardless of flying style weight is the determining factor. I was just saying that even using 100 # test we were seeing line failures at the lead out guides. Just keep an eye on it is what I'm saying and if need be allow yourself the luxury of being able to swap the lines end for end to prevent wear in just one spot which is exactly what will happen and it happens fast. Not an easy thing to do with leadouts directly attached to the bellcrank. The lines cut into the nylon and causes it to start abrading the line due to the line getting drug through the kerf it makes.I tie the knot Phil recommends, he gives us a 8x11 blown up view of this which makes it very simple, I keep it in my pit box but, I will try and copy it here which should make things easy assuming it shows up well in a photo. Ken

This was written by Phil last year. Some of what he explains is exactly what we experienced over the past few seasons.  

                           From Phil

         A lot of the ".018" stainless wire comes in under .018, sometimes as small as .017, due to the way it is made.  Stainless steel is not as strong as many other steels or music wire.  The .018 stuff usually breaks at the termination with a pull of 50-55lbs. Some of  the F2D lines mike out at .0175 and will take 65+ lbs.

The Power Pro 100 lb. test Spectra will break at 50lbs, like stainless steel with even a simple overhand knot tied on a bight- fold the line over and tie an overhand knot on the doubled line to leave a loop.  The 5 turn Uni knot in the rulebook is usually stronger, but it needs an overhand stop knot in the tag end.  Unless the knot is pulled down smoothly and carefully with some spit for lubrication the fishing line is slippery enough to pull right through the knot. It also has to be tied to a clip of some kind and is very difficult to tie to an exact length. Other knots such as a figure eight knot tied on a bight or a figure knot on a bight(see picture) can't slip, are easy to tie to fixed lengths,  and will pull over 50 lbs if they are pulled down smoothly.

Some folks have gotten cheap stuff from China that isn't nearly as strong and stiff.  If you make up a 60ft. line and it stretches more than 1.5 inches with a 35lb. pull test it's not the right stuff.  Spectra is as strong as or stronger than stainless steel and stretches about the same amount.  I used 100lb test Spectra on F2D planes at the NATS and Team Trials.  It stretched exactly the same amount as the 4 strand brass-coated F2D line-  1.5in. the 44lb pull test.

Jim Carter's suggestion of using standard crimps is a good that I'll give a try.  A knot is very easy but if the crimp is stronger that is a plus.

A couple of thing to watch out for.  If you run the lines directly to the bellcrank the lines may start to wear at the leadout guide.  It doesn't seem to make much difference what you use for a guide- brass eyelets, nylon eyelets, even glass beads- will all wear.  Depending on how it is braided you may just see little black nubbins or a bit of fraying.  If you see actual loose ends of fiber frayed the length of the line travel it is probably time to either pull test the lines individually, or just throw them out.  Wrapping the lines up from the plane and switching them end for end after every use evens out any wear and will double the useful life.  Unlike stainless where you can't see the fatigue in the wire or a broken wire in the crimp or wrapping the Spectra lets you see when it is getting tired.

Some F2D models have very rough wire for the leadout fittings.  Polish out any visible roughness.

Most brands of Spectra line are a little draggier than stainless lines.  If you have to go as fast as possible(dumb idea) don't switch.  Makes no difference in the speed limited events.

Thank you Ken. This is helpful. It sounds like a figure-8 is being used, and pull test is the requirement - not the knot.

I will think about my plan. It will involve using the clips that came in the kit, that you posted a picture of.

Phil

Phil did you get the RST done and flying?