Truth - I took a couple stabs at it and called Tom Swearingen. I don't need the aggravation.

Time out everyone-

This forum is about information and encouragement ? not shining sunlight up people?s backsides. And as soon as you post here the topic becomes bigger than you. It is going to the countless lurkers and/or builders who NEVER post. We have a duty to provide the best info we can ? and Doug has been very clear on this point.

In this particular instance I?m compelled to correct the misinformation that flex hose is a direct trade for hard line. It is not. While hose is functional and no less safe, it has some significant downsides compared with hardline. This is not my opinion ? this is fact. And I would be shocked to hear from an aero engineer who disagreed. I know for a fact that my Chief Engineer would throw someone out of his office who proposed using flex hose here because fabrication or installation of the proper hard line was ?too hard?. So while it is true that no one is compelled to build to ANY aerospace standard, it's kind of nice to know the right way to do it before you decide to ignore it, right?

So in finality (I hope), I have no interest in passing judgment publicly, nor do I believe I have the authority to grant permission, and I?m certainly not going to try talk anyone out of a decision if their mind is made up ? but don?t expect accolades for taking the easy way out either. Not when 10,000 other RV builders made it through just fine.

I will continue to provide the best information I can, and I will also fully support anyone?s right to completely ignore it.

By many standards, "functional and no less safe" indeed does mean that one would be a suitable direct replacement for the other. What has not been mentioned here, speaking of misinformation, is that flex hose also has some significant upsides compared with hardline. Both are specified for use in different applications. Each is superior to the other for certain uses.

Perhaps your Chief Engineer is unfamiliar with the concept of Design for Manufacturing? Sometimes ease of installation and repeatability are desirable even at the expense of weight and materials cost. Also, please post a reference to the aerospace standard (any published FAA or other CAA guidance, or released specification by any manufacturer of any type-certified aircraft will do) calling out 3003-O soft aluminum tubing for fuel conveyance, anywhere on the airframe. I doubt you will find one, which means that a cadre of aerospace engineers spanning multiple decades actually DO disagree.

There are a lot of other things we would have to apply to this standard as well, because not everything in an RV is designed per FAR 23 of other standards documents.
Does that automatically make all of those things unsafe? Not at all.
FAA documents are full of requirements that have always been followed because..... they have always been followed.

Your responses have gone from saving weight to judging that a decision other than the one you've recommended is the "easy way out" as if there's a lack of quality in workmanship in a decision process that may involve efficiency of effort , in which case perhaps we should all go back to the pre pre-punched days of the kits. That's silly. It's also Hubris 101.

If there's one constant over the years of RV building, it's that there's always someone -- from the original RV List, the old Yahoogroup, to the VAF -- who posits to speak for 10,000 RV builders as an evangelical of the proper way to build an RV airplane in the manner of redemptive suffering. Old-timers all know the names, very few of whom are ever heard from anymore, oddly enough.

Let's move along.

Should I use primer?

I just wanted to make a quick comment on this thread after speaking with Tom earlier.

First off, it is true that flex lines are heavier than rigid tubing. The question is how much. I will use an RV-12 crossover hose kit that was jointly developed by Aircraft Specialty and TS Flightlines. There are a total of 6 braided stainless lines as well as all the AN fittings to change over to our system.



This hose kit weighs 1lb 5 oz complete including AN fittings. It does not take into account the fittings/plastic tubing that is not utilized if you install this kit. So, my guess is that it is probably about a 1lb weight gain or perhaps slightly over versus the stock components. This is just for illustrative purposes. The advantages are that you end up with brake hoses that will last for the life of the aircraft, have a 10 year guarantee on them, and require no fabrication.

The disadvantage is that it is an aftermarket component that has a cost associated with it, and there is a small net weight gain.

Another topic that has been brought up in the past is the issue of life limits of flex hoses. The hoses that Tom and I use are only the highest quality teflon/conductive teflon hoses. These hoses have no defined service life and as long as they are not abused should be flying on your aircraft long after you are no longer flying it. In addition, we utilize stainless fittings throughout, rather than lesser quality fittings that may be a different material with a stainless coating over the top. This ensures that both the fittings and the hose are matched from the standpoint of a long service life.

Regarding the rigid tube discussion. Rigid tubes are intriguing because fabrication techniques and enjoyment vary from builder to builder. Some people thoroughly enjoy it while others absolutely hate the rigid tube portion of aircraft. That's one of the reasons we decided to begin fabrication of rigid tubes for select aircraft. Tom and I have a computerized tubing bender as well as a CNC lathe which has allowed us to start bringing new products to market. And, we are able to utilize 5052, 6061 and stainless tubing, depending on the application. These have better properties than 3003 from the standpoint of strength. The other day I took one of our 5052 thin wall rigid tubes to about 4,000 psi for the fun of it and held it there for a few minutes. Below is an example of an Rv-14 valve to wing root hose that is pre bent, flared and ready to drop in.



In addition, we can utilize the cnc lathe and bender to build custom rigid/flex assemblies where it is the best option. An example is this picture which shows a custom assembly with a rigid section at the andair valve that transitions to a flex hose to go out to the wing root.

http://aircraftspecialty.com/wpimage...c9fe_05_06.jpg

By having the capability to do rigid and flex hosing, Tom and I are able to offer solutions for those builders who really do not enjoy the fabrication of these lines and would like to focus their energy on other things.

With that said...everything we do can be done ala carte, to allow our customers the choice of fabricating what they enjoy, and allowing us to assist in the rest.

Happy Building, and thank you all for your support.
Steve

Steve,

Thank you for providing some real data.

Greg

Nope, you opened that door. See below.

...but the "too hard" sentiment is very typical of these flex hose threads. It is very reasonable to draw the conclusion that ease of installation is a compelling factor in this choice.

I'll not speak for any other builder, but I certainly will use the overwhelming data that the RV fleet represents.

I guess the bottom line here is that you had your mind made up before you even asked the question. So the only additional advice I can give you is don't ask the question on a public forum if you are afraid of the answer.

As I said, I work for a living and cost matters and I haven't talked to Tom yet, so I really haven't decided what to do. I really Don't think your considerable expertise extends to what I'm thinking or what I've decided or even how many fingers I'm holding up right now.

Let's move on and if you Don't mind I'd like to continue conversing with some of the people supplying useful data now. It's really interesting what they're providing and I'm anxious to hear more from them.

Thank you for your insight you've shared thusfar and I believe you have made it clear.

Thanks for understanding.

Happy to help Bob.

Next time I'm up your way and have a spare 30 minutes I'll build a set of lines for you.

Cheers