I think the exposed clunk would suck air rather than the submerged cluck sucking fuel.

I agree the clunk thats out of the fuel would suck air easier than the clunk in the fuel,but here again wouldnt there be a syphoning going on and get at least some fuel to pick up ,I would think it should be plenty for a downline at idle . Again I have never done this ,but it seems logical to me that it could work.

Oh man, clunks that move forward, twin clunks... this has become madness. Opjose... he's just trying to sound important, make this problem more than it is so don't for gods sake join in as the could well be somebody that'll accually do these things. As everyone is saying, we don't have the problem!
Maybe Opjose does, maybe thats why he's so keen to talk about big things, yet this isn't a big problem. Admit it, if you suffering it's because you're done something wrong bubba and thats a shame because folks have been tring to help you but you've gone and got that head suck so far up... you're critically close to turning yourself inside out.

Listen, if this was a major problem, people world wide would be having major problems. But they're not. So lets pretend that all of us ain't doing the "advanced" aerobatics that you do. Jez yes now you mention it, every plane I've seen performing aerobatics at competition... ran out of fuel during a down line! Including my own! Yikes, we all must be suffering from some form of delusion because I sware that the engines seemed to stay running!
Let me ask you, when your doing all this talking and acting like a pro... why are you having your fuel tank at the front like a amature?
Why not on the CG where most, if not all aerobatic boys have it? Make physics your practical answer instead of just talking about it.
Not as if it's necessary of course, folks don't seen to suffer from the problem anyway.
Where here to help you Opjose... just with draw your head and wash out your ears.

Uh Oh, Bla bla is "flaming" Opjose. That's an RCU no no and will get you placed on modified status. I hope the moderators are seeing this.

If you believe that, then thank you for the complement, obviously I seem "important" to you.

No, there are many posts about this on the boards, by others with the same problem.

I believe that this thread started with "running out of fuel on downlines" posted by people.

It's great that you solved your problem.

If so and you are so exasperated by this discussion, why are you making a point of hanging around other than to troll and flame?

If this isn't a "big" problem, that itself indicates that there maybe SOME problem that you may not be experiencing.

So thanks for the reaffirmation that I'm not imagining things.

I don't believe I've ever had you look at my plane, so the comment is not only uninformed, and unhelpful, but also contradictory. You haven't been trying to "help" thus far.


Ask to have a look at their fuel system. Most are quite sophisticated, use headers, pumps, redundancy on large planes, etc. to prevent all of this. A bit out of my expense league.

Importance? Pro?

A re-occurring theme, which has what to do with the discussion?

Though again thanks for the comment.


Did you bother asking where it's at?

You don't know where it's at, but are making both an unfounded assumption and a generalization.


Then why bring it up?

Really? You know this for a fact?

NO ONE has this problem? Did you take a pole?

The clunk should NOT be permitted to travel forward, and it should become exposed to the air and that is OK?


Yes others do seem quite helpful and intelligent...

Just not you.

"just with(sp?)draw your head and wash out your ears."

Opjose, Opjose, Opjose, we're here to help.
Don't worry so much about it.

I wouldn't worry about it, if my engine would continue to operate when I pull out of a long blender.

Then at least for me this discussion would be moot.

Wow, Norway sure produced a fair number of insulting people. There's this guy, motorboy and a couple others. He sure took an instant dislike to you Opjose.

Right, I can see we got of to a bad start... lets now try and solve you're problem in a safe, well tried and trusted method... without strange clunk arrangments.
How big is the aeroplane? What engine size, make, tank size. How long are you holding the blender? Is this the only time you're getting this problem?
You say it cuts when you pull out the blender. Does it always do this? If you perform a short blender as opposed to a long one is it the same result.
Have you tried this with a different engine? Are you flying buddies having the same probliem? Lets solve it.

Airplane: Funtana 90S

Engine: Evolution 1.00NX side mounted no pump, stock muffler, stock tank located just after wing tube.

I originally had a fuel filler which I've removed completely. The tank has the fuel line to the remote needle, the muffler pressure line and a fuel fill line on it's own hose, tube and fitting.

Blender: I'd say 3-4 seconds. The shorter the duration the less the problem. E.g. nose down for short durations and there is no problem. Do a slow blender at full deflections slowing the plane greatly. normally I bring up the throttle to about 50% on the downline because the plane slows down so much, then by the time I pull up the engine is cutting out.

Important note: if the tank is almost full the problem practically does not occur. It only seems to get bad after there is half a tank of fuel left.

Re: Different engine

This is the second NX I've tried in this plane.

Re: Buddies.

This has them stumped, I've not had the opportunity to get our senior field engine expert (this guy DOES write the book on this stuff) to look at my engine and setup. I'm hoping to try to have him look at everything in a couple of weeks.

You are overdone when you are writing about us norwegian..
I am not with here to dislike Opjose.. I can see Blabla are more worse here in RCU, but not my matter!!!!

Up with humor!

Jens Eirik

Don't worry.

We've produced MORE than our FAIR number of insulting people.

We have an "insulting people" surplus.
Want a few more?

Motorboy,

Say WHAT????

Opjose,

But there are 300 million us us. Not nearly that many Norwegians

Opjose I don't know that engine so i'ts difficult to comment. The airplane is a standard... a standard set-up being flow all over without problems so I'd instantly tend to rule out the standard tank setup as long as it's standard and you don't have the tank to far back without a pump.
That leaves us with the engine. Can you try another engine brand? Have you tried my longer fuel line suggestion? Don't worry about going lean during a vertical, sort that problem later...just grab a lenth of tubing, and connect it up.
If it still cuts out, it ain't a fuel problem, it's a carb problem. If it works, try moving the tank back some more.

You say you're holding on some throttle in the blender which sound right, but 50% is a lot of throttle, you'll (anyone) be using up you fuel reserve very quickly. What happen to the engine (forget what the blender looks like) when using a lower throttle setting? Does it last longer? Is the engine cuting out when you're throttling up after the blender or during?

Don't bother with clucks that can fall forward they get stuck. you'll discover exactly when one day just after you've pulled up into hover.
Twin clunks... ones going to be sucking air... that ain't good either. You'll be spending a great deal of time chasing the engine.

Try the extra fuel line and that'll give us the answer.
It's late here, I'm going to bed.


Talk tomorrow

PS. Just make sure you do all the normal safety checks and the engines OK with the extra tubing before you take off.

Hi!
You have the fueltank at the wing tubing...!!!!??? If so That's were the problem is.
You can't have the tank so far back from the engine without using some form of pump! Or a Tettra bubbleles tank...
Ordinary R/C fule tanks could not used the way you have described without pump.
Show us some pictures of your set-up please.

Regards!
Jan K
Sweden

loughbd
Stop agitating!!

Jens Eirik

Washing machines have Agitators. I just needed a translation. I don't understand your posts.

The fact that there are 300 million Americans statistcally means there must be more insulting people here than in Norway. Wouldn't you agree? Mathematically, that has to be.

I guess this [link=http://richter-lackierung.de/aktualisierung_2006/5MBVersionflycamefuntana.wmv]movie[/link] will settle some of the arguments about how fuel inside a fuel tank behaves during flight. Enjoy!

/Red B.

Great Video That purdy much tells the whole story.

This was as clear as daylight.

The clunk never follows the fuel to the front of the tank...
That is why you often get a 'hiccup' when advancing the throttle, on recovery from a long, off-throttle dive, spin, Etc..

Going down-hill at full throttle will just give you a dead-stick.

The only way to always have fuel available, is by using a bladder tank, with external (in relationship to the bladder) exhaust pressurization, so there is nothing but fuel in the fuel compartment. No air, no exhaust gasses, no foam, nothing.

Yes thank to the poster for brilliantly illustrating the problem.

It's exactly as I posted, not an "imaginary" event.

Fuel staying in the back of the tank on a downline? Right.

Sorry if I missed it but did any suggest having two clunk lines int the tank? One regular and a "Y" int the line to attached a seconf short line with a clunk that would sit near the from of the tank. Would this work? I'll leave it to the experts to tell us why this would or would not work.

Thanks Jim

Not necessarily, if going fast enough the windspeed may keep the prop turning, the compression may be enough to keep the plug lit, especially with a two stroke which will get fresh air through the exhaust port. Though I doubt this would keep it running for more than a fraction of a second or so.