dagaro1

Hi,
I have a problem with my UF fuselage tank. When I prepare to land after I dropped the flaps, and reduced speed, the hopper is empty me stop the turbine but I have more than 600 cc of fuel in the tank. I've checked everything and this right, I've given all I could tilt the tank but still have the same problem.

My configuration is:
Merlin 90 + hopper (180cc) + fuselage tank (2,2 l)

Please help me!!!!

Thank you, Daniel.

marc s

If anyone is going to be able to help we will need some more info and pictures of your setup.

marcs

lightningmcnulty

My Feedback: (11)

double check your setup, the way the manual is written it is easy to make the front of the main tank lower than the back, if its setup this way it looks like you have fuel from the front but in reality the clunk is in air because its in the back

Kim

dagaro1

Hi,
I`ve attached photos of my setup and the back fuel tank support. I´ve checked everything and I´ve tipped the tank to maximum. I´ve got other turbine planes and I`ve never haves this problem.

Thank you Daniel

bri6672

My Feedback: (6)

The tank is in 2 pieces, was the 600cc of fuel in both the front and the rear of the tank?? Did you confirm the clunk is not getting stuck and not reaching the floor if the back of the tank?

Dave Wilshere

Weighted or felt clunk in the tank? With just the fuselage tank flight time with the 90 is 5 minutes maximum. Small turbine =more throttle longer time. What is filler system connection? You have no barb on the fuel tank pipes? This mean air leaks. Shown in the manual is soldered barb tubes (provided in kit)

Dave

lightningmcnulty

My Feedback: (11)

The tank looks like it's tail high, although it's hard to see in the photos, the way to test it is to put the wing on and fuel then de-fuel the jet until you start seeing bubbles come from the main tank, do this while it's sat on its gear! next you have to take the wing off and set the jet on a stand in such a way that the attitude is the same as when it's sat on its gear! Then look at the rear of the tank from underneath and see if the fuel level is consistent throughout, if the problem that I suspect exists then the back end of the tank will be dry, as others have said the tanks baffle makes it impossible for the clunk to draw from the front end. The problem is that since the tank bottom is dead flat if it's tilted at all you land, see fuel in the front of the tank and assume it's also in the back.

if this is the problem, just remove the back support and drop the back end of the tank!

Also so listen to Dave he's a fountain of knowledge, make sure you solder the barbs on each fuel pipe end as the manual states for security. I also don't use the felt clunks as at some point they eventually clog and cause a flame out, in my experience

kim

Dave Wilshere

If the tank is built as per manual and installed as such, it works. Personally the felt clunk is the only way, never had to change one, but accept some fuels with additives might cause algae. Parafin/Kerosene we buy here is clean and stays so. My inner circle has 15 Flash models and none of the guys have ever changed a felt clunk. The clunks CARF are supplying now do need drilling out, the there are two sizes of hole and somehow they have a batch of small ones.

The only other thing I see working is BVM type clunk line on the rear section, with the small dia weighted clunk they offer.

Dave

dagaro1

Hi, I answer each one:

-bri6672: When the plane landing, the fuel is in the back. The clunk is free.

-Dave Wilshere: I use Dubro large clunk (see photo). The flight time is 5 minutes and I have more 600 cc the fuel in the fuselage tank. The merlin 90 in my old Boomerang have 6 minutes with a 1,5 l dubro tank and UF tank is the 2,2 l. The filler system connection is Festo connection (see photo). I haven´t the barb pipe but I´ve never had problems in my other tanks, in this case I checked and it hadn´t air leaks (I´ll put it).

-lightninggmcnulty: When I fill the tank in ground, the fuel is in the back of tank, I changed the tank position and it`s at maximum tilt.

-Dave Wilshere: I use a felt clunk in my hopper and the plane have only 4 flight, on the air fly fantastically. All tubes are 4mm and the fuel clunk and felt clunk are a big hole.

I think the problem is when I reduced the speed with the flaps with the nose down to lose altitude, the fuel in the fuselage tank going forward consuming all the fuel hopper and leaving the remaining fuel in the fuselage tank. The strange thing is that this does not happen to anyone because the shape of the deposit produced this situation. My UF landing very slowly with flaps.....and at the moment without engine!!!!

Thank you all for your answers.

what else do I can?

Daniel

erbroens

One of the best ways to debug a tank problem is unplugging the turbine fuel line and looping it back to the fuel can.. then using the terminal display, (GSU) run the pump in a average flying voltages and see what is happening.. cavitation, bubbles, leaks,clogged lines,etc.. this is noiseless and quite clean so it can be done at home.

In fact, is almost mandatory to do this in any new jet or installation. to help avoid those dreadful turbine flameouts.

I am sure you will find out the problem quickly, by doing this.

Dave Wilshere

When the aeroplane is flying, the fuel is towards the back, G force sees to that. Problem with weighted clunk and a flat tank is if the fuel and clunk are not together (long vertical down) there is no fuel being fed like there is from a big sponge. Each time the line empties it adds air to the hopper which is never replaced.
Dubro 50oz is bigger than European 1.5l, its more like 1.7ltrs...CARF 2.2l might be less.
I have felt clunk in both tanks (fuse and wing) and paper filter in MAP (Canada) Bubble trap. I have friends with P-180RX in the Ultra Flash with exactly the same set up. No air in the hopper after a flight.

What material for clunk line? Tygon? Too stiff for that weighted clunk. Felt clunk has weight and fuel soaked felt. What position in the tank did your clunk sit? How close to the tank rear?
This is one I built more than a year ago, still working 100%

Dave

paulhat

Hi Daniel.

I have had the same problem as you in my UF main tank.
You land with a heap of fuel but its all sitting towards the front of the tank. I dont use a felt clunk so that could be an issue.
I have heard of a good solution to this problem (which I am still getting around to trying).
That is to draw fuel from the wing tank rather than the main. This allows the main to be sucked dry during more "nose up" flight.

I guess the only downside is you have to connect 2 lines instead of one at the start of each days flying.


Try it and let me know how you go

Paul.

benitez195

Hi Daniel I have the same set up as in post #11 and I have never had any problem and my flash was 2 years with me before I sold it and the new owner has not had any problems either so you might wan to try this system

bri6672

My Feedback: (6)

Dave,

Can you give us a make and model number of the clunk you use?

husafreak

My Feedback: (3)

CARF supplies Tillotson OW-802-P

Dave Wilshere

Yep, that installation uses the std Tillotson clunk, but the centre hole is drilled out to 2.7mm. We now use clunk inners machined in the UK, these have 3.8mm holes and are really free flowing. Sadly its not viable to sell to the US.

Dave

Walo

I have felt in the main and hopper tank. Without felt in the main tank I get more air in the hopper and without felt in the hopper tank my engine goes out during a slow roll or timed roll. I also have the vent line into the airstream. Since I did this modifications I had no further problems with flameout or air in the hopper.

Regards, Walter

bigbri

My Feedback: (287)

I have the same problem I was able to lower the rear of the main tank. It now completely empties.

cbooth1979

My Feedback: (22)

So is the general consensus to run the felt clunks? I live in the Northeast and run regular Kerosene (dyed red) and oil mix. I am using Dubro heavy clunks in both my main/wing tank with a BVM Air trap. Both tanks have Tygon inside btw. I have 10 flights on my UF and have never had a flame out but I do notice my UAT is sometimes half full when I land. I also dont push my timer and have always landed with plenty of reserve. When I built my tanks last year I seam to remember people saying Not to use the stock CARF clunks? The last thing I want is a flame out so I would change them back if that is the way to go.

-Carl

ravill

My Feedback: (11)

This needs to be a sticky. ALWAYS do this on a new airframe. And then occasionally to check the integrity of your fuel system.

I learned this the hard way a long time ago.

UAT's are meant to catch bubbles which may arise from the aerobatic maneuvers you do in the sky. Your UAT is likely functioning properly.

If you are just doing laps without any aerobatics and your UAT still has bubbles, that may be an area of concern.

Kevin_W

My Feedback: (1)

I had this happen on my Bandit several years ago. I had a flameout several minutes into the flight and luckily I was able to land on the runway. I found that the main tanks were still more than half full, but the UAT was completely empty. It turned out that the quick connect fill valve I was using was not sealing properly when disconnected, and was allowing a small amount of air to be sucked directly into the UAT.
I installed a shutoff valve into the fill line and never had a problem again.

It's difficult to see in your picture, but it looks like you might be using some sort of quick connection for filling. I would check that first.

erbroens

You are right.. maybe one day of this I will try to write a webpage pointing to links of selected information (there are plenty of good ones from many people around) and some mine too. Thanks Ravill.

All this hassle and work would be worth if we can help save one jets or two from crashing, and potentially more.

dagaro1

I use Tygon as same as to your picture but my configuration is see the photo. The line is free and 3 mm from the tank rear.

Daniel

Dave Wilshere

OK, I don't like the extra length of brass tube in the back line section, its not needed and just limits the movement. Main thing is 3mm is too close to the back wall and will create a suction load. Mine finishes 15mm short of the back wall.

Dave

Randy M.

My Feedback: (38)

I had a similar issue with my turbinator. The tank is long and sits flat like the flash. I changed my clunk setup completely. I took a large Dubro clunk, I cut the barb off flush. I then bored the clunk for 3/16 id brass. I soldered the brass tube (7" long or so) directly to the clunk. Then connected it to the stopper with a section of Tygon . It has worked much better since. The old way, the clunk and tygon line would just lay on the floor of the tank. And sometimes even end up in the front of the tank.