Viton clunk line

crashflow said:

Does anybody do a brass tube in their tank and if you do do you run out of fuel on really long downlines?

Click to expand...

check this out:

pay attention to 19 or 20 seconds
i just came out of a 1/2 cuban 8 with a 45 degree downline.

this is a picture of the tank before and after i made the mods:



in the video, this is with the tank set up using the brass tube. In the video the motor wanting to shut down from the air bubbles, this was common to occur after about 5 minutes of flight, once the fuel level was about 1/2 of the 1.5 liter tank.


once i removed this brass tube and went with the Viton, the problem has been 100% solved. I also have discovered, Viton tube, and standard clunk, this can still happen. SO i went have changed my other planes to the felt clunk, and now, no more hiccups.

i am ashamed to mention this, but sometimes, a few times only, by the grace of God, i have landed the airplane, and the tank did not have a drop of fuel left!!!
The felt clunk really helps to keep the flow of fuel to the carb.

Do you use an idle up feature once you take off?

Scott

absolutely, on all my airplanes. i turn it on before i take off. once i make approach to land, i turn high idle off.

I've talked with a few other guys that have experienced this same issue and the the common thread is high idle. It's neither right or wrong, some guys prefer it like you and most of the IMAC fliers do. The thing is the design of the brass tube in the long thin "water bottle" tanks is to keep the clunk from folding over and getting caught up on it's self if allowed to fall forward on down lines much like the standard glow fuel tanks set ups. In "normal" conditions the total length of the clunk line from pick up to the carb nipple is usually plenty long enough to provide fuel to the carb reservoir to maintain a normal idle on down lines for the altitudes we fly from. Try this test to see what I mean. Time how long it takes for your engine to die at standard idle once you notice the first air bubble headed to the carb on an emptying tank. Several seconds. Plenty of time to be doing the maneuvers and recover. However, add in a high idle speed and that time is drastically shortened hence the problem you had before changing to the all Viton line. I've been flying the original design for a full 4 seasons now along with others in my club with zero issues but then again none of use use high idle either. Like I said, neither right or wrong here, just trying to shed light on what's going on and the design is sound for the majority of fliers.

Scott

Scott, that is very interesting indeed. my problem has been fixed with the felt clunk & piton line. Just goes to show, more than one way to skin a cat. IF it works for you that way, that is great. I guess if anyone else has similar problem, they can try your suggestion and get rid of the high idle. Thank you for sharing that with me.

G257945 said:

Do you use an idle up feature once you take off?

Scott

Click to expand...

I set my low idle at mid throttle trim. Then in flight I bump up 4 clicks. Still hate a digital throttle trim, after so many years with analog trim. But it is not as easy to bump your trim entering a pop top with digital trim. Ask me how I know.

I don't like flipping alot of switches. I use 1 switch for all my DR's and another switch for ignition kill. Less switches to flip, the easier it is for me to concentrate of flying.

Not disputing Viton. Just throwing it out here. The blue and yellow "siliconized"China tubing has been in my Edge with the funky rubber stopper stock tank going on five years. Stopper is not dried out and all lines are just as pliable the day they went in. Now if this stuff is dissolving I have not a clue but.....Inspecting my filters I have found no major debris build up other than some minor bacteria.

do you use ethanol free gasoline?

orthobird said:

do you use ethanol free gasoline?

Click to expand...

Nope. 89octane pump gas.

impressive!!
ok, next question, do you keep your tanks full of fuel when you are storing your airplane?