Brakes, the continuing saga

[Slyfox]

I agree with Slyfox; those inserts are mandatory. Without them the compression ring just collapses the plastic tube without getting a good seal.....

it will be like turning the faucet down and getting a little trickle of water. so no brakes is the result. have to put those insert in to keep things open and flowing.

[jrevens]

I had concern about the lack of inserts for the tubing with my Kitfox. I was told a couple of different times that the tubing (Nylaflow Type 3/16" T) & fittings supplied by Kitfox do not require the inserts. I hope that John or someone else from the factory can re-confirm that, as I will soon be plumbing my brakes.

[Slyfox]

I had concern about the lack of inserts for the tubing with my Kitfox. I was told a couple of different times that the tubing (Nylaflow Type 3/16" T) & fittings supplied by Kitfox do not require the inserts. I hope that John or someone else from the factory can re-confirm that, as I will soon be plumbing my brakes.

best way to know is to go ahead and do it. install the line and tighten it down. than remove It and look into the end, if it's crimped shut or close to it, guess what, you needed them. they are there to keep the hole from closing up. vans says you need them, so nylaflow hose is nylaflow hose. and my hose did close up without them. I installed the inserts and got braking afterward.

[jrevens]

best way to know is to go ahead and do it. install the line and tighten it down. than remove It and look into the end, if it's crimped shut or close to it, guess what, you needed them. they are there to keep the hole from closing up. vans says you need them, so nylaflow hose is nylaflow hose. and my hose did close up without them. I installed the inserts and got braking afterward.

I agree that using the inserts is probably the correct and safest way to go, but you may have some difficulty finding the correct ones for your particular tubing.
"...so nylaflow hose is nylaflow hose" is not exactly true. With Nylaflow tubing, you have types H, T, LM (both natural & black), & LP. Different wall thicknesses (& hence I.D.s), pressure & temperature ratings, UV resistance, etc. The "standard" Type T that came with my kit is the thinner wall version, and I would definitely recommend inserts if you're going to use it for brake lines, regardless of the fact that many have evidently had no problem with it leaking or coming apart at the fittings without them. It should also be protected from exposure to sunlight, as it hardens and becomes brittle with UV exposure. It's hard to beat the plastic for light weight and ease of installation, but there are probably better materials to use - especially at the wheel cylinder. The I.D. of that tubing I got is also large enough that it would be impossible for it to be squeezed shut with the Parker compression fittings I got from Kitfox. My main concern with not using inserts is the tubing "relaxing" with age and not maintaining a strong/leak-free connection.

[Slyfox]

to each there own. I do believe on these aircraft, vans aircraft also, that the nylon hose is all the same. argue all you want. I redid my lines after building my rv7 because of the inserts. the person here that is having troubles must take each connection off and look into the end of the line to see if it closed off from NOT having inserts. yes you could maybe get away without them, but if you tighten the line to much, guess what, that line will get closed off. so check your lines if you are have braking problems, most likely this is your problem.

[cgruby]

if you don't have those installed at the end of your lines you will crimp down the line when you tighten the nut. it crimps the outside compression ring and than closes the line. if you didn't install those you need to cut off the end and press the little insert in.....

Apparently I have two types of fittings, one has the brass compression ring that fits over the tube. Clearly this one needs the insert. But the Poly Flow fitting has the compression device integral to the nut and does not require a sleeve (according to AC Spruce).

I have a couple of joints that have the brass compression rings which I'll have to go back and examine.

[jrevens]

Apparently I have two types of fittings, one has the brass compression ring that fits over the tube. Clearly this one needs the insert. But the Poly Flow fitting has the compression device integral to the nut and does not require a sleeve (according to AC Spruce).

Chuck,

Some fittings have a separate compression sleeve, but the Poly-Flo fittings have the sleeve also. It's just connected to the nut. They work the very same way. With compression fittings like this, it's critical to tighten them correctly - there are published guidelines. You don't want to over-tighten or under-tighten them.

[jrevens]

to each there own. I do believe on these aircraft, vans aircraft also, that the nylon hose is all the same. argue all you want...

Nobody's trying to argue, Steve... just sharing information and trying to help others. The tubing used is not always the same. There is Nylaflow, Nylaseal, Parflex, etc., and all have been used as brake lines by some builders. There are sometimes some important differences between them for our purposes. I agree with you that inserts are a good idea. Maybe not necessary in all instances, but a good idea. I don't know what size O.D. your lines are, but if they are the smaller 1/8", or the 3/16" with a heavier wall (like Parflex), there might be a greater chance of crushing the tubing to the point that it closes off. Again, with the tubing and fittings supplied by Kitfox to me, it's pretty unlikely that you could have that happen... I just did a test with a small piece and over-tightened it to the max, and the compression just doesn't get anywhere close to closing off the tube. So there are some reasons that the differences in tubing are important - and there are differences.
When Rutan first specified the Nylaflow tubing for brake lines, his recommended technique, as I recall, was to insert a small piece of 1/8" brass tubing into the end as an insert. Many of the RV builders, and Van's themselves, have moved away from the plastic brake lines - at least to a certain extent. I used solid aluminum and Teflon-lined braided stainless on my T-18, and haven't had a single problem with it in 25 years. I repeat - this is all offered in the spirit of sharing knowledge and information, not to argue.

[Dave S]

All,

Jrevens is precisely correct....on the compression nuts with the captive ferrule, there is a prescribed way of tightening them.

I think where we might get separated from the instructions is this.

In the manual the Nylaflow/compression fitting instructions specific to the captive ferrule type nut is not in the assembly instructions where you would expect it. It is under "Compression Tube Fittings" in the Bulder Tips at the beginning of the manual before the assembly manual...goes on to say for the captive ferrule it is a "not to much" and "not too little' issue.....explains that a person should hand tighten, then wrench tighten JUST enough to seal and prevent the tube from backing out so you cannot pull it free. No more tightening than is necessary for the seal to hold; and, enough for the ferrule to bite the tube enough to hold...but no more. Also mentiones that hand tight plus one turn on the wrench works out about right. Nowhere in this tip section are inserts mentioned.OK, now going to the assembly manual covering running the brake lines. In this section there is no mention of the captive ferrule type compression nut; but, there is mention of putting a nut on the line, inserting a ferrule onto the line before attaching. Interesting part here is these instructions including inserting a ferrule over the tube separate and following placing the nut over the tube...which would not be the case if you had the captive ferrule type nut since that is a one piece deal. I don't see any mention of an insert in the assembly instructions, just the ferrule.

This is from my S7 manual.

I can see that the captive ferrule has an extended barrel which sticks out past the nut while a conventional compression fitting would not.....might explain differences people experience between using the two.

By the way.....for the tubing between the wheel cylinder and the gear leg...I used aircraft hydraulic hose (3000 psi) and AN fittings .....I know what kind of junk I have a tendency to drag my feet through..

Sincerely,

Dave S

KF 7 Trigear
912ULS WArp Drive

[Slyfox]

Steve...this is all offered in the spirit of sharing knowledge and information, not to argue.

ya I guess I went overboard. my apologies. I wanted to state that there might be a problem with the clear line.

with the problem of uneven braking, checking at least the end to make sure they didn't close off would be needed at this point. I myself like the idea of a clear line, inspection for air bubbles is easy to detect. my rv for instance, I fly pretty radical and I loose fluid out the res. on the brakes. I always look under the panel at my hoses to see if the fluid is getting low.

when bleading the brakes I can see where the air is, than I just remove the fitting close to the air and it will in most cases just exit where I removed the line on it's own.