gilslo

Hello I look this adress http://dreamworksrc.com/catalog/index.php?cPath=47_67 and I see 3 distinct UAT. What's the better UAT: BVM, Pleated Air Trap or Hanson Super Trap Header Tank. Hanson Super Trap Header Tank seems very well and cheaper. What do you think about this UAT ?

Don Perry

My Feedback: (51)

I would say the super trap.

i just ordered one and don't have it yet but the festo fitting was what made me pick it over the other two.

Harley Condra

My Feedback: (4)

Don,
Here's a few of my thoughts on Festo fittings and their useage.

Our fuel systems have two sides. Pressure, and suction.
Festo fittings work better on pressure systems than on suction. They will work fine on properly designed vacuum systems too, but in our environment, I don't use them anymore on suction.
As you indicated, they are easy to use. So easy, I may have become complacent.

Festo fittings will allow air to leak IN, if the fuel line has a minimum radius bend near the fitting end. Each and every formulation of tubing has it's own minimum bend radius. The stiffer the tubing, the larger the radius has to be. Small airplane interior compartments equals small bend radii.

Inside the fitting is a funnel shaped sealing ramp that the tubing is forced over when the tube is correctly inserted. Too sharp a bend at the end of the fitting will cause the tubing to move away from the cone seal on the outside of the bend, causing an airleak. I have had this happen, and have seen it happen too many times on other airplanes. Suction and airleaks can equal flameouts.
If this same bend is in a pressure system the fluid flow velocity keeps the fluid in the system, and it may not leak. If it does, you will notice it very easily.

I stopped using Festo's on the suction side a couple of years ago when I started noticing a small stream of bubbles from the 6mm ball valve to the fuel pump. The pump managed to process and stop the bubbles, but I changed to a 4mm ball valve on the pressure line from the pump to the engine, and got rid of the 6mm valve between the UAT by using an uninterupted line from the UAT to the pump. Since then, I've had no more bubbles.
Now that I am using ESD lines, (solid black colored) and can't see through them, I am learning an entirely new set of fuel system rules.

Just food for thought....

Harley Condra
BVM REP
JetCat REP

Kelly W

My Feedback: (2)

I'll second that...

This topic seems to repeat itself over and over, at least with respect to Festo Fittings and their appropriate usage. If its on the suction side, its just not a good idea for the reasons Harley mentioned. If you MUST use a Festo or similar style of union fitting on the suction side, make sure its up stream of the UAT so you can catch the bubbles and at least visualize the accumulate leakage over time. Barbed fittings, or preferable captured barb fittings like the original UAT use, are the preferred method of joining hoses in less that atmospheric conditions...

Kelly

Don Perry

My Feedback: (51)

So far I have never had any problems with the fetso fittings in my turbine helis and fixed wing aircraft. But I do make sure that all of the fuel lines are proberly fitted and replaced every two years in my models.

BlackCloud

My Feedback: (12)

You can read the spec on Festos site if you go digging. good for - 1 Bar meaning 14.7 PSI negative pressure and I think it was 200 Bar positive pressure, quite a difference and essentially you may get lucky using it as suction but if your fuel system draws more than 14.7 PSI, you are asking for problems. I haven't done it yet, but thought maybe an automotive vacuum guage on the vent line may show the pressure to see if it is exceeding the 14.7. If it is, I wouldn't be relying on a Festo there.

Kelly W

My Feedback: (2)

It shows up to 1 atmosphere of vacuum maximum because its impossible to create more that one atmosphere of vacuum, or -14.7 psi in gage pressure. Vacuum is really just a creative way of describing a situation where there's a lack of atmospheric pressure. Its like when you run your vacuum at home, the motor and impeller create a lower pressure, and the atmosphere around the nozzle forces itself up the hose along with the dirt... I haven't looked at the actual fitting specification in a long time, but in most cases these fittings are meant for air, in which case a small leak would only slightly change the level of vacuum or the flow rate. In fuel, the additional air and its effect would be quite obvious...

All that Harley and I are saying is that the barb fitting is far superior, which is an answer to the original question. Regardless of the spec I've seen union fittings leak under both circumstances, but I'd bet on them being more likely to fail under a vacuum. Additionally, a low restriction fuel system will lessen the likelihood of this problem, in that it will keep your fuel system closer to atmospheric pressure at high flow rates... This is done through the use the largest hoses possible, shortest lengths, etc. A side effect of that will be lower pump voltages, ECU potentially longer battery / pump life, probably lower EMI from reduced current, maybe even a more accurate RPM definition at idle and wide open...

Kelly

J. Campbell

My Feedback: (31)

I bought the Hanson Super Trap and here are my findings on it.. I have NOT flown it yet but it is installed. I found no pipe tape on the threads of the bottle, i taped it up myself, all of the UATs have this so i figured i better do it. It also came with no plug for the fill line, the aluminum plugs can be purchased seperatley for $1.25.
Now, for the quality of the trap it looks outstanding, "same" hardware, "same" bag, "same" fittings other than the FESTO and an internal filter in the bag. I figure in a installation that you have plenty of room and the 6mm line does not have to bend tightly it should be perfectly fine as long as you cut your line square and install it right.. If it is going in a tight installation i would probably go for the UAT as the line is screwed on and will not leak if bent.
The net savings on the trap after you have to buy the plug is about $25 bucks over the UAT. Just wanted to try it, if i like it i may buy another, if not its back to the proven unit for me. Russ

joeflyer

My Feedback: (48)

The simplest most reliable IMHO is the pleated filter type. I make my own for about $12. The UAT's can be a real pain to get all of the air purged out of the filter sock. I had several aborted take offs before I got mine sorted out. A friend had a couple flame outs in the air before he got his completely purged. After going through the purging/shaking routine the UAT works very well. If you drain the fuel out of the UAT you have to re-purge. The Hanson one would have the same concern, the issue mentioned about the Festo fitting, plus the extra micron filter might be more than what is required. I have no experience with it but if too fine a filter is used it would be prone to plugging easily.

With the pleated type you just connect it and it works.

Joe

Harley Condra

My Feedback: (4)

As a point of caution, with knowledge gained by the unfortunate experience of others, DO NOT under any circumstances allow the fill line to be plugged with a bolt or any other piece of threaded harware.

I witnessed a friend taxi out for his first flight of the day.

He took off, and didn't even make one circuit around the field...the new JetCat P-120 flamed out on downwind, and fortunately he didn't panic, but had the presence of mind to make a good one pass landing. No harm, no foul. He did a good job...dropped the flaps and gear AFTER he knew he would make the field.....

Upon inspection, the UAT was found to be completely empty. The UAT filler was plugged with an allen bolt. Enough air leaked past the threads to allow the engine to consume the UAT fuel, and not allow suction of the fuel from the remaining tanks in the system.

I asked the question..."Where's the aluminum plug?"
His reply: "On the workbench."
I gave him a plug to install in the fill line.

Once was enough.....he's a quick study, but almost learned the lesson the hard way.


You can also use a Festo ball valve or Festo one-way check valve on the filler lineif you don't want to use the plug.

Harley Condra
BVM REP
JetCat REP

Don Perry

My Feedback: (51)

I can second harleys statment as I did the same thing on my Bergen Trubine Heli. Left/lost the plug and put a allen bolt in. I finnaly figured it out on the third auto and like he said I'll never do that again!

Experience -- doing somethig stupid and being smart enough not to do it again!

J. Campbell

My Feedback: (31)

Well, now that i have used the trap i find that the 6mm line WILL leak at the festo if you put a sideload on it while the engine is at full tilt my tubing is square at the cut and it doesnt take much sideload .. I am dumping it and going back to a BVM UAT..Great looking product just wish it did not have that connection. Russ

lov2flyrc

My Feedback: (24)

Russ,
Are you using Festo type hard tubing or Tygon?

J. Campbell

My Feedback: (31)

Festo, from BVM.. Russ

Woketman

My Feedback: (6)

You can also use the appropriate size of brass tubing inserted in the Festo and then attach the plastic tubing to it.

causeitflies

Why not just change the fitting?
I use the home made pleated paper trap and if I get too lazy to make one I would buy the pleated air trap.

Gordon Mc

My Feedback: (11)

I think this is a classic case of "If it aint broke, don't fix it!".

IMO, the SWB design is great as is. Why is this one done differently ?

Is it REALLY that it's expected to be seen as an improvement ? Or maybe just a change that was made in order to deflect any possible accusations of cloning the SWB/BVM tank, with some marketing spiel added after the fact to pass the change off as something that we have just gotta have ??

Gordon

lov2flyrc

My Feedback: (24)

Use Tygon and the problem will be eliminated completely...

Harley Condra

My Feedback: (4)

Wocketman,
How do you install a piece of brass tubing into a Festo fitting without leaking?

Lessee here: Festo 6 MM fitting=.2362 I.D.
7/32 brass tubing=.2188 O.D.
difference= - .0174 too small

Sounds like 7/32"is too small, and a 1/4" (.250 O.D.) tube is too big.
The 7/32" brass tubing will NOT seal on the "funnel shaped sealing ramp" inside the Festo fitting. I just tried it, and under suction or pressure it leaks like a seive.


Please explain to us how you manage to use hard tubing in a Festo fitting (designed to use soft tubing) without leaks.

Since my jets are more valuable than an improperly used Festo fitting, I think I will stick to the time honored methods I described in an earlier post.
No flame war intended.

Harley Condra
BVM REP
JetCat REP

seanreit

My Feedback: (60)

Harley, I would tend to agree with you, we're talking a difference of 20 bucks here. I'm not sure I agree with Tygon in a festo fitting myself, we had some problems down here with tygon in festo fittings over time as the tygon starts to shrink or change over time. The hard tubing doesn't seem to do that. Although I've also never seen where hard tubing in a festo could be moved slightly and achieve a leak because of it. there seems to be some play built into the festo fittings to cover this.

That being said, most of my installations these days don't include festo fittings at all. The shut off valve that Jetcat and others sell is a barbed shut off, and there are some other check valve options for propane fill.

Anyway, FWIW.

lov2flyrc

My Feedback: (24)

personal experience....thousands of flights on dozens of planes with Tygon to Festo. Not one leak, or flameout. Trick to inserting tygon into 6mm festo is to lubricate it during insertion. I use kicker as this lubricates the line during insertion but evaporates leaving a well sealed connection that does not leak regardless of bend in the line.

Harley Condra

My Feedback: (4)

Sean,
When I used the term "hard tubing" it was meant to be synonomous with Brass or Aluminum tubing. When you menioned hard tubing, I think you meant polyurethane flexible (tubing) hose. I don't agree with the use of Tygon F-4040A hose in a Festo type fitting either, as it does not fit properly, and is too small in bore size to feed a large engine fuel flow requirement properly anyway. The suction side of the system will siphon better through the lower resriction 6 MM hose.


6MM hose is .1582 bore (4 MM). Tygon F4040A hose is .250 O.D., .065 wall, leaving a bore diameter of .120 (that's less than 1/8", a full .0382 smaller than 6 MM polyurethane!)
Since the 6 MM polyurethane hose, as supplied with the BVM UAT, is a full 25% larger in bore diameter, would you rather use the 6 MM polyurethane hose, or the smaller (Tygon) hose?

Harley Condra
BVM REP
JetCat REP

seanreit

My Feedback: (60)

I tried to take a picture, but didn't come out well, but yes, I'm saying the 6mm fuel tubing, I call it the hard stuff. I have it in clear and green. It really is the best stuff for our application IMO.

Tygon is great for barbed connections, where you can safety wire it. You only really need this stuff between the UAT and the pump. From the pump you can go to the 4mm hard stuff, I have a 100' roll of the 4mm.

Harley Condra

My Feedback: (4)

Roger that.
Harley

Woketman

My Feedback: (6)

I have heard of folks using brass tubing in Festos successfully. I do not recall which size Festo. And I meant using an appropriately sized brass tube. If none exists, then I guess my idea is out. How 'bout metric brass?